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It was my understanding that carbon build on pistons is helped by premium fuel and driving hard, both things I do very often for the last year and 14k miles, am I misunderstanding that.
What car and engine?
Is it all stock?
You can run some fuel injection cleaner through the system now and again
But unless you are having issues i would not worry
Check your intake between the filter and the engine and see if your *PCV* coming from the valve cover is spitting oil into your intake before it gets to the engine.
If your *PCV* valve is leaking oil a new one comes with a replacement valve cover and gasket kit. You'll also get gaskets for your spark plugs with the kit.
OP was joking. Scroll up and you'll see it's a 1.8 Mazda. If they had been experiencing pre-detonation they would have noticed engine failure long before the carbon on the pistons
The NC is just on the brink of being to old for e10 (designed in the early 2000s), it can cause issues with the seals in the fuel system, at least according to a MK3/MK4 specalist.
Some vehicles (usually modern and/or turbo sports cars) either require or benefit from premium fuel. They make less power on regular fuel. It normally won't be noticeable in daily driving, except for cars where premium is required.
Premium fuels - like Tesco Momentum, which seems to be well regarded in the 'community' - tend to have more/better additives, like detergents.
It's not about the octane rating, but the quality of the fuel.
That's crazy. The UK uses actual different detergent packages in fuel?
The US is pretty much the same between octane ratings. The only detergent package changes exist between gas supplier/station but they run essentially the same additives in all grades.
I'm only going off experience from an MX5 specalist, the NC was designed in the early 2000s and only just came out in 2005, so for the extra couple £s it costs me for peace of mind i don't mind.
Just a heads up, premium (high octane) and "premium" (top tier) are two different things. I notice I get better mileage and a smoother idle out of my 07 when I fill it up at Amoco or Marathon instead of a store branded place (like a grocery store that's 30 cents cheaper).
In the UK there is is no top tier gas like the states you just have different brands, the two best ones in my experience is v-power and Tesco Momentum.
Pistons always have carbon on them and yours look perfectly fine. Premium fuels do have more additives in them that help clean the combustion chamber (and intake valves if port injected), but you'll never find a completely shiny piston ever. If you do, it's either very new or burning coolant.
Understand what octane is.
Octane is gasoline's resistance to ignition.
That's why cars with higher compression ratios and beefier turbos need premium, so the gas doesn't detonate prematurely.
Running premium in a regular engine will result in less of the fuel being burnt.
There's the same amount of energy in a litre of premium than there is in a litre of regular.
You'll waste money and have a less efficient engine running premium.
It's an old wives tale.
It depends. Modern engines can advance their timing more with premium. Old engines can't. So, with an old engine (no knock sensor or programming to push timing), you didn't get anything extra out of premium while more modern engines can.
That said, it's an extremely small increase and it's not really worth the extra money unless it's a boosted or high compression engine. Modern boosted and high compression engines can really take advantage of pushing the timing on high octane.
At least that's my understanding and I could be way off here.
some truth, some confusion there. many modern cars are actually running wideband instead of narrowband o2's in their upstream o2 location, which in theory could allow for them to advance timing and take advantage of better fuel. doesnt mean they do, though. if you pull most any vehicle's tune, there's going to be an upper limit to their timings, and the sensors will then throttle back from there. few if any actually advance forward outside of the flashed tune in order to find the limits of the octane. i havent tuned many since \~2016 but I just cant imagine from a business and support perspective how that'd ever be different.
it's more the additives that are typically put in premium, also in the UK Premium has the lowest Ethanol percentage Which can cause issues with this engine, only minor but still issues.
You should listen and 100% take note. If you are running the wrong rated petrol or gasoline it will cause that buildup due to unburnt/poorly burnt/preignited fuel
Different ways of measuring octane, Europe uses research octane number (RON), the US (don’t know about Canada) uses anti-knock index (AKI) which gives a lower octane number than RON for a given knock resistance
I think it causes increased wear on rubber seals in the fuel system, that's what I recall in a small conversation I had with an Mx5 specialist a year ago.
I also anecdotally had a small decrease in fuel efficiency but that's probably not true and just me looking for issues/could be fixed with some small tweaking of the fueling software.
Is the wear on the rubber seals due to the presence or lack of Ethanol, per your conversation? I know that premium is recommended for MX5's, so it would certainly make sense that you'd want to run premium in your motor :)
So its the presence of Ethanol which damages the seals, premium fuel only has 5% ethanol over here whereas regular has 10% Ethanol hence using premium.
However as the UK has on average higher quality fuel, your (assuming you are in the States) standard fuel is 87 octane, our standard fuel is 91 octane, hence regular fuel is alright to use in an MX5 if you only consider octane.
I'm not inclined to agree with you on the "unburnt fuel" when running premium in an engine designed for lower compression. The octane rating is really only to prevent pre-mature ignition; once ignited by the spark the fuel should burn just as readily.
[I asked this same question on stackexchange](https://mechanics.stackexchange.com/questions/41610/will-93-octane-fuel-burn-completely-in-an-87-octane-engine) nearly 7 years ago.
You would think. While it's not necessarily bad for your vehicle, it has shown to reduce efficiency.
(CBC tested this 8 years ago) https://youtu.be/FPPkPAbzwbU?si=5HLafwhqplDSOw67
While I'm sure there could be a more scientific approach, I'll take it over forum comments.
That's very interesting! I'd be curious to know exactly what was going on there for sure. I feel like someone could dedicate an entire piece to this; the answer seems like it should follow plain logic (octane = ignition point, not overall combustibility or burn temp) but in reality there are many other variables.
I wonder if fuel additives have anything to do with it; a detergent stripping carbon off the engine. Or could it be that the particular premium fuel used in the engine was different somehow in being refined than the regular used before?
I'd be interested to know too!
In Canada at least, having worked at oil refineries myself, the only difference in the refining process for different brand/company fuels is the additives put in after the refining process.
Top Tier Gas is not a thing in the UK, it's based on brand of fuel, i use tesco momentum 99, well known among british tuning circles as the best fuel on sale.
You're misunderstood. The grade of gasoline changes its potency. Higher grade gas is more potent, faster burn... requiring more air. Different engines are specifically designed to be used with specific fuel because of this air/fuel/compression mix thats happening inside the combustion chamber.
To remove carbon build up, the best way is to remove the pistons and valves, soak in alcohol, hand clean, perform valva adjustment.
The easy way, fuel system treatment. Helps to burn some of it off. (Similiar to what you're trying to do now with higher grade of fuel) . This can help burn down some chunks of carbon... but this will never return it to new/clean.
Good luck op
I’m not sure if premium fuel with higher octane makes much difference with deposits, however using Top Tier gas allegedly does. Top tier brands have more than the required amount of detergent additives in their blends, which is separate from octane rating. There is a study that showed about 19x less carbon deposit in an engine that only ran only top tier fuel
Define driving hard. Because it's more about long highway drives than it is about driving hard. You can try oil and fuel additives to see if it makes a difference. I would prefer to avoid that in a more modern car though.
I do long motorway drives once every 2 weeks of about 100 miles and then i commute down country lanes 50 miles a day where i rag the shit out of it.
The car also takes part in autosolo and does about 25k a year.
No premium won't help with injectors, valves or pistons. As required by law all grades of gas sold in the US have same additive package. Only uses higher octane gas if your engine requires it. Otherwise a waste of money.
Yes running at wide open throttle and up near the redline on a regular basis helps to keep the injectors, ports, valves, and pistons clean. Putt putt is very hard on engines.
Just checking because I do 25k miles a year in it and it has a rather worrying knock on startup since I bought it, got worse quite quickly then leveled off the last 14k miles even with autocross and constant high rpm usage.
Already taking the garage to court for another issue so if I find something else it makes sense to throw it on there (this is after taking legal advice in my home country).
You sound like someone who isn’t confident in any information they’ve ever gotten and can’t be bothered to do their own research. Not meaning any offense by that statement, just telling you what it sounds like.
Carbon buildup happens inside of cylinders, or any structure organic matter is burned in. Yours does seem slightly heavy, but you’re also not using the fuel the engineers said you should. That’s not awful, but absolutely can cause carbon buildup beyond the norm. Fuel in your cylinders doesn’t explode like people think. It’s actually doing something known as deflagration. Coincidentally the deflagration of hydrogen was also what caused the vessel to burst during the Chernobyl nuclear accident. That means as pressure builds in the cylinder and subsequently decreases, the higher octane will resist burning more than lower octane at various pressures and not burn completely. This is also the same mechanism by which fuel detonation occurs in higher compression engines when using a lower octane fuel. Detonation is violent and bad for the engine. And if you need something to consider beyond this, just understand that seals are designed to be replaced, your entire engine isn’t necessarily. Let the seals go bad using the proper fuel, do the required maintenance and repairs, and don’t worry about software or wear parts that are made to be replaced during the life of the engine. I am an engineer, nuclear but still, and I do understand design principles in this regard.
Second thing I’d like to say, I’m not sure if anyone else already told you this, but that noise coming from your Miata at start up is super common. I have no clue why you’d make a post saying nobody has ever heard it. Not stalking you, but I needed to hear it to be sure. I don’t own a Miata, but I can tell you beyond a shadow of a doubt that it’s lifter noise. Some engines as they age don’t hold oil under the lifters as well and they will knock until oil pressure gets there to restore the hydraulic lifting pressure and eliminate the ticking sound. This is normal, even in some new cars. I bought my 2022 scat pack challenger brand new and it’s even right in the manual for the 6.4 L engine that sometimes lifter noise on startup is normal until oil pressure is high enough to stop it. If it goes away within a couple seconds there’s nothing to worry about. However, lifter noise like that while driving is a vehicle death sentence if you don’t shut it down immediately and get it towed somewhere to inspect for damage.
I hope you enjoy my adderall fueled novel. If I could recommend you pick up a Hanes manual for your vehicle and read it over, as well as a catch can. I’m not completely sure, and correct me if I’m wrong, but I think your car is direct injected? This means the carbon buildup in your cylinder is an indication of buildup also on the back of your valves. Port injected engines wash the valves as fuel is sprayed so the egr/pcv/crank case breather hose doesn’t cause oil to burn on the back of your valves. A catch can will help if you are direct injected, especially if a turbo is in this cars near future.
A couple of things, I'm not certain about this issue as it's none of the things people say it is, it's not timing chain related as the whole system has been replaced, it's not knock as it's lasted 14k miles and finally it cannot possibly be lifter rattle as these cars have solid liftets not hydraulic like NAs and NBs.
Also higher octane fuels burning slower is a myth, there octane rating Is only determined resistance to preignition as far as I'm aware.
And as someone who studied computer science at degree level I am very much of the mindset that I don't take something without fully understanding it, and none of the explanations I've got full make sense regarding this rattle.
Ok. Not hydraulic lifters. There is still hydraulic pressure involved in damping the impact and subsequently the sound. Until oil pressure is up to NOP you are basically hearing metal slapping metal. It gets quiet because of the oil’s adhesive/cohesive properties when in contact with a surface that creates a barrier so to speak between the two surfaces. If you understand pascal’s law then you will understand why the noise gets significantly quieter when the oil is between the impacting surfaces. It’s like the difference between slamming a book on a table vs slamming a book on a table with an inch of water on it. One is considerably quieter.
Higher octane fuels don’t burn more “slowly” per se, but due to the properties of octane it can burn less efficiently. Your spark plugs have a temperature rating based on the compression and the intended fuel to be used. This is all to supply the appropriate energy into the system in the form of heat (spark) and compression (also heat from compression) that will ensure proper ignition timing without detonating. Higher octane fuels will work perfectly fine in an engine not necessarily designed for it even without a tune or any upgrade. You are correct that given the appropriate amount of energy into the system both fuels will be indistinguishable. The problem is that you’re not putting the appropriate energy in for the premium fuel. Higher compression and hotter spark input more energy allowing the fuel to be burned efficiently through the pressure transient involved in the power stroke of a 4 stroke engine. The problem with using higher octane is the ability to maintain the reaction toward the end of the stroke when pressure is at its lowest and no more energy is being added to that cylinder. This can cause small amounts of fuel to be left unburnt. This will be very small amounts and buildup will not happen overnight, and the carbon buildup isn’t really much of an issue anyway if it’s not causing you any problems. If you want you can do a cold engine soak and then re-scope it to see if you cleaned it. Or just use something like sea foam. All of that to say, you’re right, but not completely and it’s a lot more complicated of an issue than people make it out to be.
Maybe these explanations can help? I feel like we probably do the same thing it’s just I’m more mechanically inclined as I was a mechanic for 10 years. Now computers? I get it, but arduino is about as far as I’m going. Also making a VR game, but that is with some help from someone who is a developer.
Honestly, if you learn like I do this book will help. I have one for my Ranger, Tacoma, and one for my old challenger since I just bought the one I have now in 2022. https://haynes.com/en-us/mazda/mx-5-miata/1990-2014
Looks pretty normal for an engine from 2009. Like someone else said run a some fuel injector cleaner through it a few times.
I’d also recommend looking at finding fuel stations that have good detergent additives and get some tanks there if they aren’t out of the way. Exxon gas is really good but I believe 76 gas has the most detergent available per gallon.
Honestly everyone is hyperfocused on removing carbon....with your description you are more likely to damage the engine than fix it pouri g liquids in it. Run some techron / pea in the gas tank
This looks like normal carbon build up. Why are you inspecting your cylinders? What issues do you suspect? How many miles are on the car? Driving hard and using premium gas isn’t going to clean the carbon. This is a common misconception. I just rebuild my engine on my civic hybrid with 190k.
It has had a nasty rattle on startup (replaced timing chain and it's lasted too long for rod bearings) for the last 15k miles and I was taking the plugs out so I thought I'd just take a little nosey. It's currently on 99900 miles and does 25k a year.
https://streamable.com/q6nyuh
It also occasionally has weird difficulty starting (just cranks for like 20 seconds then splutters a bit then starts (batteries good, no codes, no apparent issues.
It has a compress test about 3 months ago where it got 180 on all 4 cylinders, that's 6 above minimum tolerances and well below factory 250psi.
Nasty rattle on startup could be a number of things. When was the last valve adjustment? Does it still have catalytic converters? Are the heat shields properly tightened? Any loose parts/tools in the engine bay? Is it just the injector noise?
Also, is it truly a rattle? Or more of a tick? Does it do it when it's fully warmed up (and specifically when it's started while fully warm)? Does it happen throughout the RPM range?
If the cylinders all tested at the same pressure, typically the variance can be attributed to the tool and not the engine (unless all the cylinders are extremely low). That being said, if you are worried about the compression test numbers, you should look into possible valve train issues.
One more thing you should try is taking a dowel rod and using it like a stethoscope, placing one end by your ear and the other on various areas of the engine to locate the true source of the noise.
It's never had a valve adjustment, one is reccomended in the haynes manual i have for the car at 100k miles however i've never seen anyone actually do it or seen anyone with the same rattle. It still has both catlytic converters and it still passes emissions (however this can still happen if one catalytic converter is removed).
It does sound like a rattle and not a tick, it only does it on some cold startups for about 2-3 seconds, very similar to the sound you get if you change your oil and don't fill the filter as the oil is working it's way through the engine. If i crank the engine without starting it the noise doesn't happen. I've started it without the front pulleys and belt on and it still rattles.
Can injectors make noise only on startup which then dissapears?
I have tried to use a mecahnics stethascope on it but as it's very short lived and seems to never want to do it when i want it to, it's making it a challenge, i've had garages tell me it's everything from normal engine noise froms starting on a hill, to it's a timing chain (from an MX5 specalist) to big end or small end bearings.
[https://streamable.com/q6nyuh](https://streamable.com/q6nyuh)
That's the video of it, it's been driving me nuts since i bought the car a year ago and i've honestly just given up thinking about it too much as no-one can seem to figure out exactly what is causing it without dismantling the entire engine.
So that's a rattle not a knock, and that does sound like a timing chain tensioner, or chain, or cam gear. What ever it is, it is most definitely the timing system, i dont think those have vvt so maybe the tensioner or chain is stretched beyond service limit. You like to race it at high rpm that is what comes with high rpm racing. The holes look fine.
Well fuck me. Try doing valves, you said you haven't done them right? Could be they just need oil pressure. You stick with reccomended oil right? That can cause issues too. Other than that, there really isn't much that can cause that noise it definitely isn't piston slap and it definitely isn't a rod bearing.
The valves may need adjustment according to haynes they do but i've never actually seen it be done as they are just solid shims and so need the shims replaceing rather than being adjusted. I was on 5w-30 but i changed to 10w-40 as it gets used in autocross and on circuit and it was reccomended to me by a specalist, this has not made a difference to the sound.
I have also just checked the invoice the garage sent me and it's showing a timing chain kit which states it's compatible with the 2.0l and the 1.8l but i can't see any kits which are compatible with both engines, the oem kit has an oil seal and a different crankshaft sprocket for the 2.0l, now i'm questioning whether they even did it?
Currently taking them to court over this issue, they refused to repair it then after much negotiation they agreed to repair it with a contribution of £300, then this happened, currently the court wait times are over a year and the garage is refusing any communication with me hence court proceedings.
It has multiple usecases pillock, and how else are you supposed to learn without asking questions, without that urge we'd still be primitive animals.
I'm only 20 and into working on my own cars, people aren't born with an inherent knowledge of the function of vehicle mechanics.
Indeed you are 20, your answer has nothing to do with my question… I commend you for wanting to learn, I commend you for asking questions. However, learning basics of a combustion, and what happens during combustion is more important then owning a bore scope in my opinion…
A borescope is like £35, it also allows to check issues with drains, internal cable runs and better visibility to anywhere it's difficult to see, it's a handy tool for where you'd otherwise be guessing.
No, you asked why i needed a boroscop, i said some reason i need a boroscope, you then say i'm missing the point.
And this whole thread has been a learning experirence, i now know what carbon deposits look like a piston which i didn't before so that point is fucked as well.
Stop changing your argument when someone gives a rebuttal.
Bro doesn't even know what question he asked...
"why does someone like you need a boroscope?"
*lists reasons why someone might need a boroscope*
"jokes on you asshole, that's not what I asked"
Gotta love the internet...
I’m not changing an argument. You answered my question and I really don’t know why you keep running your fingers… you are a 20 year old that likes to poke things with borescope, that you happened to buy for 35$,out of curiosity. Plain and simple.
It actually looks good. It time to worry if one or more cylinders look clean. Those scopes the way they reflect and magnify make it look a lot worse than it actually is. Most cylinders look just like this
It's in the cotswolds, from devices to oxford to bristol, there are loads around the UK though, look up motorsport UK, they have list of associated clubs around the UK, can sometimes be a little hard to find stuff in there but there is plenty of stuff around. There are a couple main types of motorsport like this.
Autotest - This includes autosolo, autotest and automini, basically setting fast times round a series of cones on and airfield, generall in 1st and 2nd gear, automini is smaller, autotest involves reversing, my favourite is autosolo.
Rally - This isn't your typical rally, it will generally be navigation based on public roads with short sections on private rally stages.
Trials and Crosscountry - This is where you take your car and try and see how far you can make it down an offroad trail or hillside.
All of these are designed to be taken part in your every day street vehicles with no modifications nessicary, fun fact you are not permitted any offroad tyres or 4wd vehicles for trials or rally and you are not allowed competitive race tyres for autosolo.
It's a great way relatively cheap way to get into motorsports.
You can try the Seaford method of getting rid of the carbon by removing a vacuum line and sucking up Seaford till the engine shuts down let it sit over night then start and run in the morning it will smoke a lot and ur carbon should be gone or at least have a lot less this has worked for me not for carbon build up but for sticky rings that were smoking
Try this mixture, 10% brake fluid, 25% carb cleaner fluid, engine oil 15% , the rest petrol or diesel, depends on what you're working on. Get all the cylinders halfway and leave to soak over night. The next day turn over , very slowly manually with the plugs out to allow the whats left of the mixture to lubricate and clean. Do not start yet.
Once you've gotten all the liquid out by turning it, leave the plugs out and swing a few times with the starter motor and check compression afterwards for each( if its diesel engine make sure it can expel the fluids to avoid hyrdoblowingaholeintheEngine)
Just to be sure it's still got compression.
Once you've made sure of both things, then get it ready to start and turn it manually one more time.
It will smoke, the fumes are likely to be unhealthy so wear masks and put the extraction pipe on the exhaust.
Ive done this for a number of issues, from zero comprehension to sticky rings and rusty bores.
Worked every time. Best of luck
This is fine .. no problem here , youre never going to get all carbon off the pistons as its a result of combustion,
If theres no warning lights then replace spark plugs and youll be fine
- mazda tech
Thank you for posting to AskMechanics, Zdos123! If you are asking a question please make sure to include any relevant information along with the **Year**, **Make**, **Model**, **Mileage**, **Engine size**, and **Transmission Type (Automatic or Manual)** of your car. *This comment is automatically added to every successful post. If you see this comment, your post was successful.* *** Redditors that have been verified will have a green background and an icon in their flair. *** # **PLEASE REPORT ANY RULE-BREAKING BEHAVIOR** ### **Rule 1 - Be Civil** Be civil to other users. This community is made up of professional mechanics, amateur mechanics, and those with no experience. All mechanical-related questions are welcome. Personal attacks, comments that are insulting or demeaning, etc. are not welcome. ### **Rule 2 - Be Helpful** Be helpful to other users. If someone is wrong, correcting them is fine, but there's no reason to comment if you don't have anything to add to the conversation. ### **Rule 3 - Serious Questions and Answers Only** Read the room. Jokes are fine to include, but posts should be asking a serious question and replies should contribute to the discussion. ### **Rule 4 - No Illegal, Unethical, or Dangerous Questions or Answers** Do not ask questions or provide answers pertaining to anything that is illegal, unethical, or dangerous. # **PLEASE REPORT ANY RULE-BREAKING BEHAVIOR** *I am a bot, and this action was performed automatically. Please [contact the moderators of this subreddit](/message/compose/?to=/r/AskMechanics) if you have any questions or concerns.*
I assume the first picture is carbon on the piston? If so, nothing to worry about.
It was my understanding that carbon build on pistons is helped by premium fuel and driving hard, both things I do very often for the last year and 14k miles, am I misunderstanding that.
What car and engine? Is it all stock? You can run some fuel injection cleaner through the system now and again But unless you are having issues i would not worry
2009 MX5 1.8L Mazda MZR. I exclusively run e5 premium.
Good deal I like to run catch cans on all my engines Also helps to keep oil out of the intake tract and off pistons
Check your intake between the filter and the engine and see if your *PCV* coming from the valve cover is spitting oil into your intake before it gets to the engine. If your *PCV* valve is leaking oil a new one comes with a replacement valve cover and gasket kit. You'll also get gaskets for your spark plugs with the kit.
PCV*
No it's PVC like the glue. Positively vented crankcase
No, PCV is right. Positive crankcase ventilation. Whoever told you pvc is dyslexic
Thank dog my dyslexia doesn’t affect my work at random house…..
I think most boats run on diesel
1.9pd NC here we come.
Pre detonation if you put e5 in it
OP was joking. Scroll up and you'll see it's a 1.8 Mazda. If they had been experiencing pre-detonation they would have noticed engine failure long before the carbon on the pistons
A 1.9pd is a turbo diesel VW engine I believe.
It is, but that's not the engine they have, it was a joke
isnt premium for race cars and old cars... like cars that are not designed to run ethanol...? why are you using it lol...
The NC is just on the brink of being to old for e10 (designed in the early 2000s), it can cause issues with the seals in the fuel system, at least according to a MK3/MK4 specalist.
Some vehicles (usually modern and/or turbo sports cars) either require or benefit from premium fuel. They make less power on regular fuel. It normally won't be noticeable in daily driving, except for cars where premium is required.
Anything post 2005 is approved for e10. The e5 is only specifically needed for the miatas prior to that
Premium fuels - like Tesco Momentum, which seems to be well regarded in the 'community' - tend to have more/better additives, like detergents. It's not about the octane rating, but the quality of the fuel.
That's crazy. The UK uses actual different detergent packages in fuel? The US is pretty much the same between octane ratings. The only detergent package changes exist between gas supplier/station but they run essentially the same additives in all grades.
I'm only going off experience from an MX5 specalist, the NC was designed in the early 2000s and only just came out in 2005, so for the extra couple £s it costs me for peace of mind i don't mind.
Just a heads up, premium (high octane) and "premium" (top tier) are two different things. I notice I get better mileage and a smoother idle out of my 07 when I fill it up at Amoco or Marathon instead of a store branded place (like a grocery store that's 30 cents cheaper).
In the UK there is is no top tier gas like the states you just have different brands, the two best ones in my experience is v-power and Tesco Momentum.
Pistons always have carbon on them and yours look perfectly fine. Premium fuels do have more additives in them that help clean the combustion chamber (and intake valves if port injected), but you'll never find a completely shiny piston ever. If you do, it's either very new or burning coolant.
That's how I clean my pistons. I pour water down the intake manifold /s
Understand what octane is. Octane is gasoline's resistance to ignition. That's why cars with higher compression ratios and beefier turbos need premium, so the gas doesn't detonate prematurely. Running premium in a regular engine will result in less of the fuel being burnt. There's the same amount of energy in a litre of premium than there is in a litre of regular. You'll waste money and have a less efficient engine running premium. It's an old wives tale.
It depends. Modern engines can advance their timing more with premium. Old engines can't. So, with an old engine (no knock sensor or programming to push timing), you didn't get anything extra out of premium while more modern engines can. That said, it's an extremely small increase and it's not really worth the extra money unless it's a boosted or high compression engine. Modern boosted and high compression engines can really take advantage of pushing the timing on high octane. At least that's my understanding and I could be way off here.
some truth, some confusion there. many modern cars are actually running wideband instead of narrowband o2's in their upstream o2 location, which in theory could allow for them to advance timing and take advantage of better fuel. doesnt mean they do, though. if you pull most any vehicle's tune, there's going to be an upper limit to their timings, and the sensors will then throttle back from there. few if any actually advance forward outside of the flashed tune in order to find the limits of the octane. i havent tuned many since \~2016 but I just cant imagine from a business and support perspective how that'd ever be different.
it's more the additives that are typically put in premium, also in the UK Premium has the lowest Ethanol percentage Which can cause issues with this engine, only minor but still issues.
You should listen and 100% take note. If you are running the wrong rated petrol or gasoline it will cause that buildup due to unburnt/poorly burnt/preignited fuel
I'm using the only fuel with e5 you can still buy, which people all over the UK use to fuel MX5s, Tesco Momentum 99 specifically.
Do you guys have toptier fuel specs in the UK? Usually I just make sure to go to gas stations with that rating here in Canada.
Different ways of measuring octane, Europe uses research octane number (RON), the US (don’t know about Canada) uses anti-knock index (AKI) which gives a lower octane number than RON for a given knock resistance
Oh yeah I was aware of that, really threw me for a loop seeing European octane rating for the first time! Toptier measures the additives in fuels.
Canada also uses aki
I'm curious what specific issues this causes :)
I think it causes increased wear on rubber seals in the fuel system, that's what I recall in a small conversation I had with an Mx5 specialist a year ago. I also anecdotally had a small decrease in fuel efficiency but that's probably not true and just me looking for issues/could be fixed with some small tweaking of the fueling software.
Is the wear on the rubber seals due to the presence or lack of Ethanol, per your conversation? I know that premium is recommended for MX5's, so it would certainly make sense that you'd want to run premium in your motor :)
So its the presence of Ethanol which damages the seals, premium fuel only has 5% ethanol over here whereas regular has 10% Ethanol hence using premium. However as the UK has on average higher quality fuel, your (assuming you are in the States) standard fuel is 87 octane, our standard fuel is 91 octane, hence regular fuel is alright to use in an MX5 if you only consider octane.
I gotcha! I 100% agree with what you're thinking on that one
I'm not inclined to agree with you on the "unburnt fuel" when running premium in an engine designed for lower compression. The octane rating is really only to prevent pre-mature ignition; once ignited by the spark the fuel should burn just as readily. [I asked this same question on stackexchange](https://mechanics.stackexchange.com/questions/41610/will-93-octane-fuel-burn-completely-in-an-87-octane-engine) nearly 7 years ago.
You would think. While it's not necessarily bad for your vehicle, it has shown to reduce efficiency. (CBC tested this 8 years ago) https://youtu.be/FPPkPAbzwbU?si=5HLafwhqplDSOw67 While I'm sure there could be a more scientific approach, I'll take it over forum comments.
That's very interesting! I'd be curious to know exactly what was going on there for sure. I feel like someone could dedicate an entire piece to this; the answer seems like it should follow plain logic (octane = ignition point, not overall combustibility or burn temp) but in reality there are many other variables. I wonder if fuel additives have anything to do with it; a detergent stripping carbon off the engine. Or could it be that the particular premium fuel used in the engine was different somehow in being refined than the regular used before?
I'd be interested to know too! In Canada at least, having worked at oil refineries myself, the only difference in the refining process for different brand/company fuels is the additives put in after the refining process.
Premium fuel has nothing to do with it. If you want ADDITIONAL fuel additives for cleaning use TOP TIER GAS. Google it.
Top Tier Gas is not a thing in the UK, it's based on brand of fuel, i use tesco momentum 99, well known among british tuning circles as the best fuel on sale.
No Top Tier gas in UK? I didn’t know that.
You're misunderstood. The grade of gasoline changes its potency. Higher grade gas is more potent, faster burn... requiring more air. Different engines are specifically designed to be used with specific fuel because of this air/fuel/compression mix thats happening inside the combustion chamber. To remove carbon build up, the best way is to remove the pistons and valves, soak in alcohol, hand clean, perform valva adjustment. The easy way, fuel system treatment. Helps to burn some of it off. (Similiar to what you're trying to do now with higher grade of fuel) . This can help burn down some chunks of carbon... but this will never return it to new/clean. Good luck op
I’m not sure if premium fuel with higher octane makes much difference with deposits, however using Top Tier gas allegedly does. Top tier brands have more than the required amount of detergent additives in their blends, which is separate from octane rating. There is a study that showed about 19x less carbon deposit in an engine that only ran only top tier fuel
Define driving hard. Because it's more about long highway drives than it is about driving hard. You can try oil and fuel additives to see if it makes a difference. I would prefer to avoid that in a more modern car though.
I do long motorway drives once every 2 weeks of about 100 miles and then i commute down country lanes 50 miles a day where i rag the shit out of it. The car also takes part in autosolo and does about 25k a year.
Maybe try running some seafoam or Lucas GDI deep clean through the intake.
No premium won't help with injectors, valves or pistons. As required by law all grades of gas sold in the US have same additive package. Only uses higher octane gas if your engine requires it. Otherwise a waste of money. Yes running at wide open throttle and up near the redline on a regular basis helps to keep the injectors, ports, valves, and pistons clean. Putt putt is very hard on engines.
Someone got a scope from santa...if the cars driving, leave it be...there are plenty of other places you can scope.
Looking for a good time?
😀 true to your name
>there are plenty of other places you can scope. Instructions unclear; wife wants a divorce now.
Just checking because I do 25k miles a year in it and it has a rather worrying knock on startup since I bought it, got worse quite quickly then leveled off the last 14k miles even with autocross and constant high rpm usage. Already taking the garage to court for another issue so if I find something else it makes sense to throw it on there (this is after taking legal advice in my home country).
You sound like someone who isn’t confident in any information they’ve ever gotten and can’t be bothered to do their own research. Not meaning any offense by that statement, just telling you what it sounds like. Carbon buildup happens inside of cylinders, or any structure organic matter is burned in. Yours does seem slightly heavy, but you’re also not using the fuel the engineers said you should. That’s not awful, but absolutely can cause carbon buildup beyond the norm. Fuel in your cylinders doesn’t explode like people think. It’s actually doing something known as deflagration. Coincidentally the deflagration of hydrogen was also what caused the vessel to burst during the Chernobyl nuclear accident. That means as pressure builds in the cylinder and subsequently decreases, the higher octane will resist burning more than lower octane at various pressures and not burn completely. This is also the same mechanism by which fuel detonation occurs in higher compression engines when using a lower octane fuel. Detonation is violent and bad for the engine. And if you need something to consider beyond this, just understand that seals are designed to be replaced, your entire engine isn’t necessarily. Let the seals go bad using the proper fuel, do the required maintenance and repairs, and don’t worry about software or wear parts that are made to be replaced during the life of the engine. I am an engineer, nuclear but still, and I do understand design principles in this regard. Second thing I’d like to say, I’m not sure if anyone else already told you this, but that noise coming from your Miata at start up is super common. I have no clue why you’d make a post saying nobody has ever heard it. Not stalking you, but I needed to hear it to be sure. I don’t own a Miata, but I can tell you beyond a shadow of a doubt that it’s lifter noise. Some engines as they age don’t hold oil under the lifters as well and they will knock until oil pressure gets there to restore the hydraulic lifting pressure and eliminate the ticking sound. This is normal, even in some new cars. I bought my 2022 scat pack challenger brand new and it’s even right in the manual for the 6.4 L engine that sometimes lifter noise on startup is normal until oil pressure is high enough to stop it. If it goes away within a couple seconds there’s nothing to worry about. However, lifter noise like that while driving is a vehicle death sentence if you don’t shut it down immediately and get it towed somewhere to inspect for damage. I hope you enjoy my adderall fueled novel. If I could recommend you pick up a Hanes manual for your vehicle and read it over, as well as a catch can. I’m not completely sure, and correct me if I’m wrong, but I think your car is direct injected? This means the carbon buildup in your cylinder is an indication of buildup also on the back of your valves. Port injected engines wash the valves as fuel is sprayed so the egr/pcv/crank case breather hose doesn’t cause oil to burn on the back of your valves. A catch can will help if you are direct injected, especially if a turbo is in this cars near future.
A couple of things, I'm not certain about this issue as it's none of the things people say it is, it's not timing chain related as the whole system has been replaced, it's not knock as it's lasted 14k miles and finally it cannot possibly be lifter rattle as these cars have solid liftets not hydraulic like NAs and NBs. Also higher octane fuels burning slower is a myth, there octane rating Is only determined resistance to preignition as far as I'm aware. And as someone who studied computer science at degree level I am very much of the mindset that I don't take something without fully understanding it, and none of the explanations I've got full make sense regarding this rattle.
Ok. Not hydraulic lifters. There is still hydraulic pressure involved in damping the impact and subsequently the sound. Until oil pressure is up to NOP you are basically hearing metal slapping metal. It gets quiet because of the oil’s adhesive/cohesive properties when in contact with a surface that creates a barrier so to speak between the two surfaces. If you understand pascal’s law then you will understand why the noise gets significantly quieter when the oil is between the impacting surfaces. It’s like the difference between slamming a book on a table vs slamming a book on a table with an inch of water on it. One is considerably quieter. Higher octane fuels don’t burn more “slowly” per se, but due to the properties of octane it can burn less efficiently. Your spark plugs have a temperature rating based on the compression and the intended fuel to be used. This is all to supply the appropriate energy into the system in the form of heat (spark) and compression (also heat from compression) that will ensure proper ignition timing without detonating. Higher octane fuels will work perfectly fine in an engine not necessarily designed for it even without a tune or any upgrade. You are correct that given the appropriate amount of energy into the system both fuels will be indistinguishable. The problem is that you’re not putting the appropriate energy in for the premium fuel. Higher compression and hotter spark input more energy allowing the fuel to be burned efficiently through the pressure transient involved in the power stroke of a 4 stroke engine. The problem with using higher octane is the ability to maintain the reaction toward the end of the stroke when pressure is at its lowest and no more energy is being added to that cylinder. This can cause small amounts of fuel to be left unburnt. This will be very small amounts and buildup will not happen overnight, and the carbon buildup isn’t really much of an issue anyway if it’s not causing you any problems. If you want you can do a cold engine soak and then re-scope it to see if you cleaned it. Or just use something like sea foam. All of that to say, you’re right, but not completely and it’s a lot more complicated of an issue than people make it out to be. Maybe these explanations can help? I feel like we probably do the same thing it’s just I’m more mechanically inclined as I was a mechanic for 10 years. Now computers? I get it, but arduino is about as far as I’m going. Also making a VR game, but that is with some help from someone who is a developer. Honestly, if you learn like I do this book will help. I have one for my Ranger, Tacoma, and one for my old challenger since I just bought the one I have now in 2022. https://haynes.com/en-us/mazda/mx-5-miata/1990-2014
https://preview.redd.it/hbhtg0152cac1.jpeg?width=2592&format=pjpg&auto=webp&s=5b006ae182ebf844082c614264e04a85282a0f34
Looks pretty normal for an engine from 2009. Like someone else said run a some fuel injector cleaner through it a few times. I’d also recommend looking at finding fuel stations that have good detergent additives and get some tanks there if they aren’t out of the way. Exxon gas is really good but I believe 76 gas has the most detergent available per gallon.
It's at 1.8 L Miata NC so they must be in Europe. In the US all gasoline has detergents added. I prefer Shell or Texaco.
Is the vehicle direct injection? How many miles? Any info?
This is the question. Direct injection is the carbon culprit
Honestly everyone is hyperfocused on removing carbon....with your description you are more likely to damage the engine than fix it pouri g liquids in it. Run some techron / pea in the gas tank
Best comment ever from a friend looking at borescope photos “It’s a boy!” The first photo confirms that statement.
Normal carbon buildup
This looks like normal carbon build up. Why are you inspecting your cylinders? What issues do you suspect? How many miles are on the car? Driving hard and using premium gas isn’t going to clean the carbon. This is a common misconception. I just rebuild my engine on my civic hybrid with 190k.
It has had a nasty rattle on startup (replaced timing chain and it's lasted too long for rod bearings) for the last 15k miles and I was taking the plugs out so I thought I'd just take a little nosey. It's currently on 99900 miles and does 25k a year. https://streamable.com/q6nyuh It also occasionally has weird difficulty starting (just cranks for like 20 seconds then splutters a bit then starts (batteries good, no codes, no apparent issues. It has a compress test about 3 months ago where it got 180 on all 4 cylinders, that's 6 above minimum tolerances and well below factory 250psi.
Nasty rattle on startup could be a number of things. When was the last valve adjustment? Does it still have catalytic converters? Are the heat shields properly tightened? Any loose parts/tools in the engine bay? Is it just the injector noise? Also, is it truly a rattle? Or more of a tick? Does it do it when it's fully warmed up (and specifically when it's started while fully warm)? Does it happen throughout the RPM range? If the cylinders all tested at the same pressure, typically the variance can be attributed to the tool and not the engine (unless all the cylinders are extremely low). That being said, if you are worried about the compression test numbers, you should look into possible valve train issues. One more thing you should try is taking a dowel rod and using it like a stethoscope, placing one end by your ear and the other on various areas of the engine to locate the true source of the noise.
It's never had a valve adjustment, one is reccomended in the haynes manual i have for the car at 100k miles however i've never seen anyone actually do it or seen anyone with the same rattle. It still has both catlytic converters and it still passes emissions (however this can still happen if one catalytic converter is removed). It does sound like a rattle and not a tick, it only does it on some cold startups for about 2-3 seconds, very similar to the sound you get if you change your oil and don't fill the filter as the oil is working it's way through the engine. If i crank the engine without starting it the noise doesn't happen. I've started it without the front pulleys and belt on and it still rattles. Can injectors make noise only on startup which then dissapears? I have tried to use a mecahnics stethascope on it but as it's very short lived and seems to never want to do it when i want it to, it's making it a challenge, i've had garages tell me it's everything from normal engine noise froms starting on a hill, to it's a timing chain (from an MX5 specalist) to big end or small end bearings. [https://streamable.com/q6nyuh](https://streamable.com/q6nyuh) That's the video of it, it's been driving me nuts since i bought the car a year ago and i've honestly just given up thinking about it too much as no-one can seem to figure out exactly what is causing it without dismantling the entire engine.
So that's a rattle not a knock, and that does sound like a timing chain tensioner, or chain, or cam gear. What ever it is, it is most definitely the timing system, i dont think those have vvt so maybe the tensioner or chain is stretched beyond service limit. You like to race it at high rpm that is what comes with high rpm racing. The holes look fine.
Issue is that i've replaced the whole timing system and it made no difference at all. you are right aswell it does not have VVT.
Well fuck me. Try doing valves, you said you haven't done them right? Could be they just need oil pressure. You stick with reccomended oil right? That can cause issues too. Other than that, there really isn't much that can cause that noise it definitely isn't piston slap and it definitely isn't a rod bearing.
The valves may need adjustment according to haynes they do but i've never actually seen it be done as they are just solid shims and so need the shims replaceing rather than being adjusted. I was on 5w-30 but i changed to 10w-40 as it gets used in autocross and on circuit and it was reccomended to me by a specalist, this has not made a difference to the sound. I have also just checked the invoice the garage sent me and it's showing a timing chain kit which states it's compatible with the 2.0l and the 1.8l but i can't see any kits which are compatible with both engines, the oem kit has an oil seal and a different crankshaft sprocket for the 2.0l, now i'm questioning whether they even did it?
Take it the fuck back bro I thought you did it yourself
Currently taking them to court over this issue, they refused to repair it then after much negotiation they agreed to repair it with a contribution of £300, then this happened, currently the court wait times are over a year and the garage is refusing any communication with me hence court proceedings.
What car is this? Because that definitely seems like a VVT actuator issue.
You gotta tell me someone saw that face... Come on
I see Billy, from SAW!
If you’re using an aftermarket or K&N filter stop and go back to an OE setup
Seafoam it and move on
Why do people like you have borescopes? What good is it for you if you look at an image and have no clue what you are looking at?
It has multiple usecases pillock, and how else are you supposed to learn without asking questions, without that urge we'd still be primitive animals. I'm only 20 and into working on my own cars, people aren't born with an inherent knowledge of the function of vehicle mechanics.
Mic drop
Indeed you are 20, your answer has nothing to do with my question… I commend you for wanting to learn, I commend you for asking questions. However, learning basics of a combustion, and what happens during combustion is more important then owning a bore scope in my opinion…
A borescope is like £35, it also allows to check issues with drains, internal cable runs and better visibility to anywhere it's difficult to see, it's a handy tool for where you'd otherwise be guessing.
Really is that what borescopes are used for? No way… Again completely missed my point… Good thing they are 35$, perks of the 21st century…
No, you asked why i needed a boroscop, i said some reason i need a boroscope, you then say i'm missing the point. And this whole thread has been a learning experirence, i now know what carbon deposits look like a piston which i didn't before so that point is fucked as well. Stop changing your argument when someone gives a rebuttal.
Bro doesn't even know what question he asked... "why does someone like you need a boroscope?" *lists reasons why someone might need a boroscope* "jokes on you asshole, that's not what I asked" Gotta love the internet...
I’m not changing an argument. You answered my question and I really don’t know why you keep running your fingers… you are a 20 year old that likes to poke things with borescope, that you happened to buy for 35$,out of curiosity. Plain and simple.
I only have two things to say i paid £35 and fuck off.
I didn’t expect you to say anything intelligent, really. Good luck
What and you did, that's fucking laughable
Run a few cans of fuel cleaner through and it'll clear right up
It actually looks good. It time to worry if one or more cylinders look clean. Those scopes the way they reflect and magnify make it look a lot worse than it actually is. Most cylinders look just like this
How's the compression??
Have you considered seafoam?
It's fine..send it
Apart from ye old death rattle [https://streamable.com/q6nyuh](https://streamable.com/q6nyuh) ahh shitty car dealers, my dream.
It will just be faster before death. Send it
already got an autosolo championship lined up next year, if it's going to die it's going to die in a blaze of cones, wheelspins and angry marshalls.
That sounds pretty fun. Where in the country is it?
It's in the cotswolds, from devices to oxford to bristol, there are loads around the UK though, look up motorsport UK, they have list of associated clubs around the UK, can sometimes be a little hard to find stuff in there but there is plenty of stuff around. There are a couple main types of motorsport like this. Autotest - This includes autosolo, autotest and automini, basically setting fast times round a series of cones on and airfield, generall in 1st and 2nd gear, automini is smaller, autotest involves reversing, my favourite is autosolo. Rally - This isn't your typical rally, it will generally be navigation based on public roads with short sections on private rally stages. Trials and Crosscountry - This is where you take your car and try and see how far you can make it down an offroad trail or hillside. All of these are designed to be taken part in your every day street vehicles with no modifications nessicary, fun fact you are not permitted any offroad tyres or 4wd vehicles for trials or rally and you are not allowed competitive race tyres for autosolo. It's a great way relatively cheap way to get into motorsports.
Sounds like lifters to me.
You can try the Seaford method of getting rid of the carbon by removing a vacuum line and sucking up Seaford till the engine shuts down let it sit over night then start and run in the morning it will smoke a lot and ur carbon should be gone or at least have a lot less this has worked for me not for carbon build up but for sticky rings that were smoking
Try this mixture, 10% brake fluid, 25% carb cleaner fluid, engine oil 15% , the rest petrol or diesel, depends on what you're working on. Get all the cylinders halfway and leave to soak over night. The next day turn over , very slowly manually with the plugs out to allow the whats left of the mixture to lubricate and clean. Do not start yet. Once you've gotten all the liquid out by turning it, leave the plugs out and swing a few times with the starter motor and check compression afterwards for each( if its diesel engine make sure it can expel the fluids to avoid hyrdoblowingaholeintheEngine) Just to be sure it's still got compression. Once you've made sure of both things, then get it ready to start and turn it manually one more time. It will smoke, the fumes are likely to be unhealthy so wear masks and put the extraction pipe on the exhaust. Ive done this for a number of issues, from zero comprehension to sticky rings and rusty bores. Worked every time. Best of luck
May I add that every mazda on the planet burns oil. You want that gone, get an injector cleaning. Or just send it. Carbon's normal.
This is fine .. no problem here , youre never going to get all carbon off the pistons as its a result of combustion, If theres no warning lights then replace spark plugs and youll be fine - mazda tech
Did ya cheek the whale penis exhaust intake