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DETONATION, The Real Quest Killer


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#1 brianpaul98

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Posted 27 October 2005 - 11:34 PM

Hello,

I read where people in the know talk about it but I'm not sure how many truly understand what it is or what the consequences are when it happens. Here's an example to get this started

If you are running 12 PSI of boost and run a 14.50 in the quarter mile on 93 octane and the factory ignition timing setting of 10 degrees BTDC that's a decently good run for a mildly modded Quest.

So you think, well, I ran a 14.50 at 12 PSI so I'm going to bump it up to 15 PSI and I'll pick up even more. So, you turn up the boost and nothing else and at the end of the run you look at the time slip and realize you just went 2 tenths slower  :shock:   maybe more depending on the weather conditions.

Now your thinking, how the bloody heck did that happen :? You just turned up the boost and went slower?? Here's the deal, there is this thing called detonation that is the all powerful killer of engine parts. When I say powerful it has the ability to turn forged pistons into black scared rubble. It can take a brand new cylinder head crack it into junk and all too many of you know heard the horrible stories of the knocking rod syndrome. Stock and forged pistons don't just come apart in a 2.6 liter due to sheer torque or horsepower, heads don't just crack because of too much cylinder pressure and head gaskets don't just blow out because the bolts are not strong enough. You can choose to believe these myths if you want to because that is your prerogative.

For those of you who may be interested and do not know what detonation is I will try to explain it in simplified terms. Picture your engine running along very smoothly. The pistons are going up and down through the cycles drawing in the air fuel mix in the intake stroke, compression stroke comes up and BANG fires the mix, power stroke back down the hole and exhaust stroke out the tailpipe. Very general description as I said just to give the picture.

The fuel that you run in your vehicle directly affects this cycle when it comes to a turbo engine. Under normal driving conditions or quick bursts you may not have any problems but under a steady load like 1/4 mile racing the fuel you run has a serious affect on the performance of your vehicle. At 12 psi boost with 93 octane on a cool day you car will probably run strong with no problems because the 93 octane fuel can support the final compression ration in your engine at 12 PSI. Turn up the boost to 15 or 18 PSI and that same 93 octane fuel will start to ignite before the piston reaches the position in its cycle when the spark plug is set to ignite it, hence the name pre-ignition. As this pre-ignition is happening and the rpm's keep getting higher the engine is fighting against itself until it reaches a point where the pre-ignition pressures are equal to the horsepower the engine is production and it turns into a sort of pressure lock within the cylinder. This extreme pressure lock is not the necessarily the killer in itself but the severe vibration that comes with it. So what do we have, extreme heat, extreme vibration and extreme pressure. When these three elements are put together the outcome is disaster. A rod bearing that is riding on a cushion of oil just can't support those conditions and the upper cylinder parts take the worst of it. Starting with a fairly delicate head in the first place its usually the first to go, then the head gasket is soon to follow.

If the pressures in the cylinder can be controller and managed keeping detonation to a minimum there will be less chances of blown head gaskets, cracked heads and rod bearings failing. Well this is all good right but I'm sure you going to ask... So what do you suggest we do, right? Its fairly simple actually, the first thing you need to have is a way to know when the engine is actually detonation, right?? I mean if you don't know its happening how can you correct the problem.

For those of you that think if you can't hear your engine pinging then its not happening, well, you can keep believing that but just have an extra set of pistons, rod bearings, a head and a few head gaskets handy.

For those of you that are still with me, there is a fantastic little tuning tool that should be one of the first things you invest in when you start turning up the boost that's made by MSD and called a Knock Alert (PN# 8964). This is the one of the simplest things to install and with only 3 wires (power, ground and sensor wire) you can have it up and working in an hour. Its about as big as a radar detector and has the same looking LED display and it will visually and audibly alert you when your engine is experiencing detonation.

Now with all that said, if your engine is running smoothly at 12 PSI and detonation is occuring at 15 PSI, you will more than likely go slower because the engine is working against itself.

Ok, now that you have something to tell you when detonation is happening that STILL doesn't explain how to avoid it. This is actually the easy part and there are a few EASY steps to follow to save your investment.

First, if you don't already have one and you plan to go race your car or just want to get the most out of it, go out and buy yourself a good adjustable timing light. If you plan on having your car for a while its the least you can do and a worthwhile investment OR you can just trust Cooter at the local slam and bang down the street every time you need to make a timing adjustment. Personally, I can't see how anyone who's serious about building a performance car can live without an adjustable timing light. I have seen two different styles of distributors and each one has a different amount of mechanical advance built into it. Maybe one comes in the automatic cars and the other comes in the 5 speeds or maybe its the year the car was made that's the difference. I don't know but what really matters is you want the distributor with the least amount of advance built into it. I modify my distributors to be adjustable so I can limit the degree of advance where it only moves the timing between 10 - 15 degrees.

I'm sure most of you have the mind set when you look at the factory service manuals as they are the all knowing Quest Bibles but there are certain things to understand, those books were written with the idea in mind that the FACTORY TUNE UP SPECS would be used with FACTORY STOCK BOOST LEVELS and FACTORY STOCK PATRS. If you own a bone stock Quest and are doing a general tune-up because you want better gas mileage and all round driveability the tune up in those manuals is for you. If your car has more mods done to it than you care to remember then they are going to get you in trouble.

PLEASE LET ME CLARIFY THIS BECAUSE I'M SURE MANY PEOPLE OUT THERE WHO ARE NOT FULLY READING WHAT I'M SAYING WILL START RANTING AND RAVING ABOUT ME TELLING EVERYONE THAT THE FACTORY SERVICE MANUALS ARE WORTHLESS ARE EVERYTHING IN THEM IS WRONG.

What I am simply saying is that when you start to modify your engine, fuel system, intake, exhaust, electronics past the point of the stock realm the factory service manuals were specifically written for, your tune up is also going further away from those norms. Therefore the information in the service manuals becomes less correct for the realm you are now working within. Boy I hope that makes sense.

Back to the ignition timing. When setting the ignition timing you must first understand that the 10 degrees BTDC was arrived at by the Mitsu engineers to cover the full spectrum of drivers and driving conditions that this car would encounter. It needs to start easy and have good fuel economy for the average driver. This is not my main concern and if your attempting to build a fast Quest, I hope its not yours either.

I set the ignition timing as high as the engine will tolerate and still crank over fairly easily. If you have a half dead battery and a starter thats on its last leg this won't be much higher than 10 degrees BTDC. My race Quest with the 296S cam will start with no problems at 15 - 18 degrees BTDC and this also helps it to idle better with the throttle being in a more closed position. If you have a stock cam you will not be able to run this high of an initial timing because the stock cam builds much higher cranking cylinder pressures and the engine just won't turn over at 18 deg BTDC. I run my TOTAL timing advance no more than 30 degrees and with nitrous no more than 28 degrees advance.

What this TOTAL timing advance hoopla means is when the engine reaches 3000-3200 rpm the distributors mechanical advance mechanism is completely in. I don't run the vacuum advance because it has too much room for error with boost fluctuations. If you get little spikes or drops in pressuer this will be messing with the ignition timing and that's bad. The less moving parts in the distributor the more accurate your ignition timing and thats better. Most real race cars have the distributor completely locked out so when they start the car the timing is already right at total advance and never moves.

For those of you who use an MSD digital 6 box you can easily do this because it has a built in feature called a start retard and the digital 6 box also has the advantage of the nitrous retard built in that can be set up to work as a single stage boost retard. The advantages of setting the timing in this way is that high initial timing will give the engine more off the line power but it needs to be limited because if total timing should not go past 32 degrees with high boost (15-18 PSI) or the engine will start to detonate.

Second is the fuel. I know right now with gas prices the way they are Super Unleaded is just ridiculous and forget race fuel. Fact of the matter is that without the correct octane fuel you are just self destructing the internals of the engine. You can lessen the chance of detonation by running a really efficient intercooler and doing various mods to keep the fuel/air mix as cool as possible but under hard steady acceleration it will only work to a point. You may say, this is all a bunch of BS because I run 18 psi all day long on 93 octane and I never have a problem. Well, all I can say is you have been very lucky and your day is slowly coming so you better have the new engine kit ready.

The last thing that will really help the detonation problem is to add something to the air/fuel mixture to keep it cool. I have mentioned this concept to people several times but didn't really get any light bulbs going off so maybe if I write it down it will start to make sense. Since the early 1900's automobile engineers and aircraft engineers alike experimented with water / alcohol injection to get every last horsepower out of the engines they produced and worked with. Right now on e-bay there is a 1947 DODGE SEDAN / WATER INJECTION SYSTEM for sale.

http://cgi.ebay.com/ebaymotors/1947-DODGE-...sspagenameZWDVW

I wouldn't recommend buying it but its just to show this is not a new concept. During WWII Sir Harry Ricardo helped to perfect this system and the water / alcohol injection was used on bomber planes to get every horsepower out of them which enabled them to take off fully loaded with all the bombs they could carry.

Ok, its not the 40's and we aren't building bomber planes here either but my point is that alcohol or better yet RACING METHANOL will help to cure the detonation problems and the best part is YOU CAN RUN 20 or 25 PSI WITH 93 OCTANE PUMP GAS using the methanol injection !!!

Oh boy, I can just feel it already... the opinions are raging and are going to start piling up like rednecks at a mud hop  ohmy.gif  Heres the deal, racing methanol is generally less than 3 dollars a gallon, if misted in before the intercooler it will super cool the entire air/fuel mixture, clean the entire intake track, clean the carbon from the cylinder head, valves, pistons, spark plugs and the engine will see this new mixture as if you were running 110 octane race fuel in the tank depending on how much alcohol you use. Use it when you need it and still have the economy of running pump gas. Just think how many tanks of race fuel you will run in the next few years. A alky kit will pay for itself 10 fold compared to all the high octane fuel and broken engine parts.

There are different supplemental methanol injection setups available like the one offered by alkycontrol.com which gives you a progressive controller, steel braided lines and everything you need to put it on. Some kits like the ones from Cooling Mist are just an on / off type of deal and although the progressive is the way to go the fixed mist setup will work pretty well too. I have also seen alcohol being misted in before the turbo to cool the housing and cleans the turbine wheel while it helps to atomize the mix.

Well, I think thats enough for now and I hope this was informatiev, understabndable and I'll keep the colors all black so as not to be hurting peoples eyes this time  :shock:
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If its not broke, tear it apart and make it go faster!!!
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Brian Arnone
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#2 Vanishing Point

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Posted 28 October 2005 - 11:30 AM

Thanks Brian,

I use the $3.50 110octane gas because its easy and close to home, but I may look into water injection incase I plan on going out of town, or as a selling feature. Anyhow how hard and how much time does it take to tune the water injection? To me its almost another system and complication that I need to tinker with all the time. Mount the tank run the hoses set the switch to much water whoops not enough......... I guess.

Knock sensors are tricky because you need to tune out all the engine noise. was that a knock or did I reach an RPM that made more noise.

Stock timing is a balance of burn time, pump gas, and emissions. The stock dist. retards the timing under boost to avoid knock, if its not working you can detonate.

Tony
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#3 brianpaul98

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Posted 28 October 2005 - 04:30 PM

Sure you can run the stock vacuum advance in the distributor if you want to and for the vast majority of people that own these cars it won't affect anything if it malfunctions here and there. In fact you probably wouldn't even know it. Some of us know how poorly the car runs when that vacuum advance goes all together bad right?

I'm not saying that using the distributor the way it is would be wrong or right, I'm just saying I don't trust it to always work the way it was designed to and the results of it not working the way its suppose to are something I don't care to deal with.

Where do you buy 110 race fuel for $3.50 per gallon? Man thats cheap, its close to $7.00 a gallon here. I think I'm moving to Michigan  smile.gif
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#4 Boosted_One

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Posted 28 October 2005 - 04:37 PM

This is great info.

I think this should go into the FAQ area.

You make some great points!!
Mike K

#5 brianpaul98

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Posted 28 October 2005 - 06:28 PM

Thanks and I'm glad people are actually reading it. It took quite a while to type up and I was nearly crosseyed when I finished  :? I didn't know where to post this and I just figured it would fit ok here.

Its just some ideas and tips that I have gathered through the years and looking over everything I have done this is what I would have wanted to know about first back when I started blowing things up. Like I explained in there, just because you can't hear detonation doesn't mean its not happening. If you CAN hear it, oh boy, its really bad and generally doing its dirty work to the pistons. I wish I knew how to post pictures on here because I can show you exactly what detonation looked like on a brand new set of Wiseco pistons with very low miles.

If you would like to see them PM me your e-mail address.
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#6 Boosted_One

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Posted 28 October 2005 - 06:39 PM

QUOTE (brianpaul98)
I wish I knew how to post pictures on here because I can show you exactly what detonation looked like on a brand new set of Wiseco pistons with very low miles.

If you would like to see them PM me your e-mail address.


Like this?




There's a fairly long story and diagnostic opinions on exactly how it happened.

To post pics copy the URL then type:

[IMG]URL[/IMG

Put another ] bracket after the /img above.

Or hit the IMG button up above.
Mike K

#7 JustPaus_88TSi

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Posted 28 October 2005 - 06:49 PM

Definately FAQ material.. biggrin.gif
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#8 brianpaul98

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Posted 28 October 2005 - 07:41 PM

Thanks for the help with the pictures but I don't have a URL for them.  They are just on my computer right now. Where are your pictures hosted on the net?


Is that piston a stock cast piston or forged? From the top it doesn't look cast  but its hard to tell. Stock cast pistons generally don't take a lot of abuse to look like that. If you read T(SL)OP ENDS big misconception under their blocks section of Tips, Tricks and Things to do before taking it in the arse from them on their website you will see that they claim high boost takes the ring lands off.


QUOTE
The stock pistons are a different story. They suck. Anyone considering anything bigger than a 14G sport turbo and more than 15 psi boost had best start thinking about Forged pistons. It is only a matter of time before the stock ring lands shatter and your car turns into a smoke machine.



That is total BULL and I have run stead 15 PSI on my STOCK BOTTOM END 89 Quest for years and never took off a ring land. I personally know a guy with a Monza who ran a 350 Chevy with 12:5.1 cast claimer pistons in it. He shot that thing with more 250HP (maybe more, he'd never show the pills) shots of nitrous that I can tell you and was running low 9's in the quarter mile before he made a few bad adjustments and detonated the heck out of it. I wish I had a picture of is pistons because they very much resemble yours.

Stock cast pistons act a little differently when detonation hits them because they are made of a softer casted metal. Does that piston of yours have the Black Death on the skirts? Forged pistons that are detonated badly will have the undeniable Black Death or Black Scorch / scratch marks all over the piston skirts which generally results in the scratches going right past the rings which ultimately ruins them. The rings will more than likely be stuck right in the grooves also.

To really diagnose that mishap I would need to look at the big end of the rod and the bearing. If the bearing looked bad or was spun and the piston has a lot of black scorching and scratches on the skirts and the piston was tight, not necessarily stuck, on the pin it was bad detonation.

If the rod bearing was ok with no discoloration on the big end of the rod, the piston skirts looks to have just normal wear with the piston moving freely on the pin then its something else. The way that piston really looks ,now that I take a better look at, appears as if you leaned out pretty bad during a hard run and the top of the piston took so much heat that it started melt. Eventually the ring land lifted resulting in piston to head / valve clearance issues then broke off. Detonation will just break a ring land off clean or beat the ring lands wider on a forged piston and it will have a lot of small black porous hole surround that area. That really looks to be a melted then lifted ring land that hit the head then broke off more than an engine that was detonating.
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#9 Dcrasta

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Posted 28 October 2005 - 08:06 PM

We're not worthy!
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#10 JustPaus_88TSi

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Posted 28 October 2005 - 08:23 PM

I host my pics at www.2.6liter.com

Also, to attest to the stock piston strength. Artinist runs a 60-1 T4, modded stock intake MPI, 17yr old bottom end.. Dyno'd 341hp, 338tq with 91oct..

I believe he was pushing over 22psi aswell..

http://www.starquestclub.com/forums/viewtopic.php?t=8890
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#11 brianpaul98

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Posted 28 October 2005 - 10:39 PM

Yes and I would be willing to bet that as long as artinist keeps a good tune up on his engine it will continue to run strong. He may need a quick hone and re-ring eventually, hey nothing lasts forever and what a ring goes through  :shock:  can't imagine they lasted 17 years. I also wouldn't hesitate to put the stock slugs right back in there too.

If'n they ain't broke, don't fix em.


I'm trying to get the pictures uploaded now, hope I got it right.
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#12 JustPaus_88TSi

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Posted 28 October 2005 - 10:45 PM

QUOTE (brianpaul98)
I'm trying to get the pictures uploaded now, hope I got it right.


If you run into problems, send me a PM and let me know if you want assistance. smile.gif  I have LOTS of pictures hosted there..
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#13 brianpaul98

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Posted 28 October 2005 - 11:01 PM

I think I got it. The first two pictures are of a set of Wiseco pistons that were for sale on e-Bay not too long ago. The rest of the pictures are a different new set of Wiseco pistons that replaced the first set that was for sale on e-Bay.






These sorta remind me of the pictures you see on the internet of some guys head after he wiped out on his chopper without a helmet. Not much difference when it's all said and done.










You can see in these last two pictures what high boost (25psi) a small amount of detonation and too tight piston to wall clearance (.002") will do. Two thousandths piston to wall clearance is for a stock rebuilds, you know something you'll give to grandma to go get the groceries with. I run AT LEAST .006" and after a few freshen ups, well its a bit more.  biggrin.gif  






Hope this is enough to get your attention and take care with the pump gas, high boost and ignition timing.
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Brian Arnone
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#14 Boosted_One

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Posted 29 October 2005 - 06:00 AM

Yeas Brian the piston I posted is a JE forged piston. Ceramic coated domes and moly coated skirts.

If that was a cast piston it would look like a bowl of corn flakes.

Here's what happened.

I was on the dyno on my 6th pull.

I ran it to 6000 RPMS.

I let off.

It coasted down to 3000 rpms then the motor shut off.

Followed by a large puff of black smoke.

Pulled the head and found that.

I think I had too mach back pressure, too much valve overlap and it preignited.

There was no load when the motor went. It was coasting down.

My air fuel ratios never exceeded 12.2's as we were using WB readings on the dyno.

As far as the rods and stuff they are fine...in fact there in my new build up.

Even the metal shim headgasket was still good.
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#15 Outlander

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Posted 29 October 2005 - 06:49 AM

Thank for all the information Brian, those are some pretty ugly looking pistons. So the stock set up with the lets unplug the waste gate mod just dosent work for you? Well i guess that makes two of us.  laugh.gif  I will PM you later for some more information on my setup and where I would like to go with it. All that stuff definatly needs to go in the FAQ area. Good work bud  :wink:

#16 Vanishing Point

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Posted 29 October 2005 - 10:47 AM

QUOTE (brianpaul98)
Where do you buy 110 race fuel for $3.50 per gallon? Man thats cheap, its close to $7.00 a gallon here. I think I'm moving to Michigan  smile.gif


I dont know why its so cheap. One station had it for $3.59/gallon and another was $3.25/gallon. Last time I bought some almost 2 months ago it was $3.50/gallon. Might be the lack of demand around here. I think I should have bought a 5000gallon tank and stored some, Im sure the price will be going up now that I found it. Always happens that way.

You dont want to move to Michigan the employment picture doesnt look so good here. I know, but with the cheap racing gas its a toss up. biggrin.gif  

By the way the sander is working great. I sprung a coolant leak, but its totally unrelated. Darn Ebay junk.

Tony
07 013web.jpg
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#17 TurboRaider

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Posted 29 October 2005 - 11:52 AM

This is one of the better writeups of piston damage from detonation, effect and casues.  It covers how the boundry layer gas that insulats your pistons gets stripped away by detonation and gives good photos of the damage.

http://www.sacskyranch.com/deton.htm

Good read,

Kevin

#18 TurboRaider

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Posted 29 October 2005 - 12:30 PM

QUOTE (Boosted_One)
Yeas Brian the piston I posted is a JE forged piston. Ceramic coated domes and moly coated skirts.

If that was a cast piston it would look like a bowl of corn flakes.

Here's what happened.

I was on the dyno on my 6th pull.

I ran it to 6000 RPMS.

I let off.

It coasted down to 3000 rpms then the motor shut off.

Followed by a large puff of black smoke.

Pulled the head and found that.

I think I had too mach back pressure, too much valve overlap and it preignited.

There was no load when the motor went. It was coasting down.

My air fuel ratios never exceeded 12.2's as we were using WB readings on the dyno.

As far as the rods and stuff they are fine...in fact there in my new build up.

Even the metal shim headgasket was still good.


Mike,

I would say it was detonation and the piston was hot and soft from the last dyno pull.  See the link to the article on why you would get localized heating at the edge or the piston.  Light / moderate detonation can cause localized damamage.  You are more vulnerable when you are alreaady making a lot of power and the piston temps are high.

When you have the motor loaded the pressure from combustion is pushing the top ring downward so there is no pulling load on the top of the top ring land.  The top of the piston is supported by the ring if it gets soft and starts to fail.

The mix enters under boost so you are not pulling a vacuum.  

Get some detonation soften the piston top up and once you back off the throttle and pull a vacuum the top ring starts to load against the top of its ring groove.  My guess would be that the pistons was already hot and soft and once it got pulled on it gave way.

How did it stay together during the run?  The top ring was supporting it, it was pinched down clamping the ring.

Thats my theory at least.  smile.gif

BTW I ran some informal tests on ceramic coatings on piston tops and did not measure any differance in heat transfer rate using a flame against the piston top between a coated and uncoated piston.  I'm not convinced.

Kevin C

#19 TurboRaider

TurboRaider

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Posted 29 October 2005 - 12:38 PM

[quote="brianpaul98"]

You can see in these last two pictures what high boost (25psi) a small amount of detonation and too tight piston to wall clearance (.002") will do. Two thousandths piston to wall clearance is for a stock rebuilds, you know something you'll give to grandma to go get the groceries with. I run AT LEAST .006" and after a few freshen ups, well its a bit more.  biggrin.gif  



[quote]

Just dont confuse cold clearnaces with hot clearances.  The forged pistons may start out looser but since they expand faster once they are hot they should have a similar running clearance to grannies pistons.

Kevin C

#20 brianpaul98

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Posted 29 October 2005 - 12:44 PM

Hey Mike,

Another thing I noticed about that piston was that there is black carbon down past the top ring. If the other pistons had the same thing the top compression ring wasn't sealing or lost its seal on those also. Now if it was just on this piston then its understandable and was probably due to the ring land failure. The carbon should never be down past the top ring or the compression rings have lost their seal and the engine will be losing a considerable amount of power.
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If its not broke, tear it apart and make it go faster!!!
----------------
Brian Arnone
Lower Shores Performance
lower.shores.performance@gmail.com
New Jersey, USA




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