# anyone break a ringland and not have any detonatoin marks in the combustion chamber?



## weeblebiker (Apr 3, 2003)

so I lost comppression on cylinder #3, tore it apart and found cracked ringlands on piston #3. other than the cracks the pistons, the plugs, valves and combustion chambers look fine, no indication of detonation. cylinder walls are not marked
really detonation damage or did my 18 year old pistons just give out
running E85, tuning around 15 psi, maybe 11:1 compression











_Modified by weeblebiker at 2:11 AM 8-5-2009_


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## broko (Mar 18, 2005)

pictures of your pistons? my car just started throwing smoke from the valve cover breather but still ran very strong and no smoke out the tailpipe. cylinder walls, valves, combustion chamber etc. looked just fine. here's what pistons 1&4 looked like.








I don't think detonation caused this either, just stress I think.


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## weeblebiker (Apr 3, 2003)

*Re: (broko)*

I don't think I can get a pic to show the cracks, everything is still in one piece. heck I didn't even see them when I was looking for them the first time I had the piston out. 
i threw a compressioon test when I heard a slightly rough idle.


_Modified by weeblebiker at 3:04 AM 8-5-2009_


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## broko (Mar 18, 2005)

well, to answer your question. mine went out without detonation. or maybe I did have some but my a/f ratios were no higher than 12.8 under boost.


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## weeblebiker (Apr 3, 2003)

*Re: (weeblebiker)*

hey what ms are you using? are you using the boost control solenoid function?


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## broko (Mar 18, 2005)

using ms1 v2.2 not using any type of boost control at the moment, just the spring that came with my wastegate. you on v3 ?


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## weeblebiker (Apr 3, 2003)

*Re: (broko)*

ms2 v2.2 ms extra code.
my af was around 11.5:1 (E85)


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## AutobahnTuningSolutions (Jan 14, 2008)

*Re: anyone break a ringland and not have any detonatoin marks in t ... (weeblebiker)*

Ive seen this from running too rich. Fuel puddles between the rings and detonation there.


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## weeblebiker (Apr 3, 2003)

*Re: anyone break a ringland and not have any detonatoin marks in t ... (AutobahnTuningSolutions)*

how rich?
I'm stoich +stoich at everything in cruise /regular driving range around max power lambda for most everything around 10 psi. 10-15psi on the rich side of max power, but not pig rich. and when I was around 15 psi, I was only there long enough to asses the boost controller PID adjustments, maybe 2-4 seconds. not spiking more than 18 psi max


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## AutobahnTuningSolutions (Jan 14, 2008)

*Re: anyone break a ringland and not have any detonatoin marks in t ... (weeblebiker)*

Do you have a pic of the top of the piston?
Ive seen it happen at a/f's of 10.5:1 in boost but since you're running E85 its going to be a bit different. Usually you dont see it right away but after time it seems to happen. I assume you meant at max power, lambda is around 10:1 not 10psi. But if you could clarify.


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## pdogg (Nov 11, 2004)

*Re: anyone break a ringland and not have any detonatoin marks in t ... (AutobahnTuningSolutions)*

ya i have had my last 3 motors break ring lands on 2 pistons first motor was #1 piston ring land and 2nd motor #3 piston ringland (looks just like the pic above) and the whole piston broke on the last motor was #3 piston cracks all the way down both sides from piston pin up and down all 3 motors had around 120xxx miles on the pistons but the rings,hone and all new bearings had 400miles. the most i got out of any stock piston was 480miles at 18psi and 10-1 compression never any detonation on any pistons on all the motors afr 11.5 and egt at 1200 to 1400 pre turbo and every thing was checked with a 10x magnafine glass. im thinkin stock pistons just no good with lots of miles on them. just rebuilt new motor with all new everything trust me it not cheap


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## weeblebiker (Apr 3, 2003)

*Re: anyone break a ringland and not have any detonatoin marks in t ... (AutobahnTuningSolutions)*


_Quote, originally posted by *AutobahnTuningSolutions* »_Do you have a pic of the top of the piston?
Ive seen it happen at a/f's of 10.5:1 in boost but since you're running E85 its going to be a bit different. Usually you dont see it right away but after time it seems to happen. I assume you meant at max power, lambda is around 10:1 not 10psi. But if you could clarify. 

max power on E85 is .7143 lamda, equivelent to 10.5:1 afr on a af gauge. 
I was around 11:1-10:1 afr up around 15 psi. haven't been up there enough to dial the afr in better than that.
starting to sound like new pistons are in order,
now are forged slugs really necessary or will new cast slugs such as TOPLINES be adequate? for this level of boost and compression.
I'll try and get pics tonight


_Modified by weeblebiker at 10:46 PM 8-6-2009_


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## ade007 (Jun 12, 2007)

ive blown ringlands twice.... then i fitted an open element intake sensor to retard timing when engine is heatsoaked by stuck in traffic etc and run a colder plug since that ive had no problems


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## weeblebiker (Apr 3, 2003)

*Re: anyone break a ringland and not have any detonatoin marks in t ... (weeblebiker)*

I'm also running open element ait and the cold coldest njk plugs, I forget the pn but ya know the ones


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## AutobahnTuningSolutions (Jan 14, 2008)

*Re: anyone break a ringland and not have any detonatoin marks in t ... (weeblebiker)*

BKR7E?
Also, I have a set of 4 9a pistons Ill get rid of for $50.


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## Agtronic (May 14, 2001)

*Re: anyone break a ringland and not have any detonatoin marks in t ... (weeblebiker)*

I cracked the ringlands in my ABA a few years back. Fuel pump fuse kept blowing and happened once under boost and she went. It ran good for about 3-4 years before that. I drove it broken like that for a few weeks, still made power under boost, but it was puffing big time at idle, and basically ran like crap. There were no signs of detonaton. I was running two head gaskets, 550cc injectors and SDS.


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## weeblebiker (Apr 3, 2003)

*Re: anyone break a ringland and not have any detonatoin marks in t ... (Agtronic)*

so by the evidence, I detonated my piston to poo.
alright, I can live with that. they are cheap enough to replace and keep tuning, until I quit detonating.
then I'll put my other block in with fresh pistons and over bore this block.


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## Jefnes3 (Aug 17, 2001)

*Re: (weeblebiker)*


_Quote, originally posted by *weeblebiker* »_ms2 v2.2 ms extra code.
my af was around 11.5:1 (E85)

Edit: I wrote this before I read the engine thread....

1. I assume that your afr data is gasoline reference NOT 'ACTUAL' AFR.
That AFR is too lean for E85.
In terms of lambda:
Boosted gasoline: Lambda 0.80 - 0.82
Boosted E85: Lambda .70-.72 (~10.3 AFR gasoline reference)
On E85 too rich doesn't hurt anything like gasoline does.
(no power loss)
Suggest: simply go into the fuel map and add a bunch...

-Jeffrey Atwood



_Modified by Jefnes3 at 11:15 PM 8-8-2009_


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## weeblebiker (Apr 3, 2003)

*Re: (Jefnes3)*

naw the 11.5 afr is in gas terms, as my megasquirt display only shows gas afr. so lambda was .79 ish. 
remeber that the o2 sensor only reads lambda, and the software takes that and multiplies it by 14.7 to give afr
I think what killed the piston(s) was my over run fuel cut settings. I was cutting fuel .7 seconds after my throttle closed. so going up and bouncing around 15 psi than letting the throttle slam shut = super lean decel = detonation










_Modified by weeblebiker at 5:30 AM 8-9-2009_


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## EL DRIFTO (Jul 11, 2004)

*Re: (weeblebiker)*

all good info
no wonder my **** kept blowing up
too much e in your oil will result in bearing failures


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## weeblebiker (Apr 3, 2003)

*Re: (EL DRIFTO)*

a match will take care of the E in the oil








yah I'm richening things up and pulling the timing back a bit.


_Modified by weeblebiker at 4:34 PM 8-9-2009_


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## steve12345 (Jan 8, 2006)

*Re: (weeblebiker)*

Popped a ring land as well.
I may have another one broken now too. Crank case pressure is a bit high.


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## weeblebiker (Apr 3, 2003)

*Re: anyone break a ringland and not have any detonatoin marks in t ... (weeblebiker)*

a good read
http://www.streetrodstuff.com/...ation/
http://www.superchargersonline...D=104


_Modified by weeblebiker at 5:40 PM 8-9-2009_


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## schimt (Jan 15, 2007)

*Re: anyone break a ringland and not have any detonatoin marks in t ... (weeblebiker)*


_Quote, originally posted by *weeblebiker* »_a good read
http://www.streetrodstuff.com/...ation/
_Modified by weeblebiker at 5:40 PM 8-9-2009_

That is a great article


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## EL DRIFTO (Jul 11, 2004)

*Re: anyone break a ringland and not have any detonatoin marks in t ... (weeblebiker)*

very useful http://****************.com/smile/emthup.gif 
now i know why you need more gas after 30 seconds WOT...duh
10.0!!! slower & colder
and the prem chip timing isn't going to last on the highway indefinately either...hmmm
it's a good thing my car isn't running yet








thanks again, i learned someting today


_Modified by EL DRIFTO at 11:48 PM 8-10-2009_


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## weeblebiker (Apr 3, 2003)

*Re: (steve12345)*

i'm figuring if one ringland breaks, all the pistons are compromised.
I replaced all of em.


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## 206danebmx (May 16, 2001)

*Re: (weeblebiker)*

This sounds all too familiar, I too am in the process of tearing my motor apart due to compression loss in cylinder #3. 1.8L 16v turbo running 15psi controlled via wastegate spring, 9:1 compression, MS1, AFR's were around 12.5 under all boost conditions, no more than 15 degrees of timing under full boost 
I haven't pulled the pistons out of the block yet, but so far, plugs, head, piston tops and cylinder walls look decent, no harsh signs of detonation, plug color was perfect looking when I first pulled the plugs.
I'll let everybody know the outcome of my situation.
Are all of these failures that everybody has posted so far all from stock pistons? Mine are stock by the way too, probably many miles i'm guessing as well. I only had the turbo setup running for like 800 miles .


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## weeblebiker (Apr 3, 2003)

*Re: (206danebmx)*

yes, i believe so.
I was looking at forged slugs, but after reading what people have acomplished on stock pistons, and reading the articles I linked above, I think breaking ringlands is a tuning issue. 
so dollar for dollar, 
better to buy expensive stronger parts?
or
buy tuning aids like knocksense and dyno time?
I'm going for tuning and dyno time


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## sp_golf (Nov 28, 2007)

*FV-QR*

Re-tune it and keep the timing conservative 'til you go on the dyno, especially in the mid range, bring it down to 18-20 at 150+kPa/3500+RPM(just to be safe) and extend the map past 210kPa


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## 206danebmx (May 16, 2001)

*Re: FV-QR (sp_golf)*

Update: So I too have cracked ring lands, the #3 piston that was giving low compression appears to have multiple cracks. I have not checked the other pistons. I could feel the hesitation that must have been this and I was at full boost around 6K rpm, 4th gear.
I may go forged pistons and knock sensor setup to be safe, I don't feel like pulling this thing apart again. I want reliability and power.


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## schimt (Jan 15, 2007)

*Re: FV-QR (206danebmx)*

just for a heads up, i have forged pistons and destroyed them, Scroll down for the pics
http://forums.vwvortex.com/zerothread?id=4516861


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## EL DRIFTO (Jul 11, 2004)

*Re: FV-QR (schimt)*

i vaporized the only set of forged pistons i ever put in, before i got back from the first test drive.
the aba oe distributor plug was wet under the rubber booty, ran like it had a miss, wot a few times, done deal - looked melted, all cyl evenly
that's when i decided to give up on anything nice
i kept blowing the 4th cyl in that setup, come to find out when i cc'd the injectors, 4 was lean
4 was also the cylinder that needed the most fuel in my personally ported, 4th is getting way too much air now, manifold
even though the collective af coming out the muffler, with some ring lands, was 12:1
preig melts stuff
what's interesting to me is that, over the years, my ringlands have never cracked unless i kept wot, could hear detonation, which meant the knock had already pulled 12 degrees...
so misfires are preig
cc your inj
why would anyone run lower than #9 plugs, in the middle of summer on pump gas
know your intake manifold if you dont have 4 wideband
go with the airplane tune, or read weeble's preig link about wot af after 30 seconds
i personally grenaded lots of times getting off the highway top speed in the summer, park it for 5 minutes off to heat soak in front of gas station. then start it back up, ignore all that noise chasing down someting
a friend of mine tried to tune his own standalone before dyno, for about a year, 4G63 when he got it on the dyno, it was shamefully off


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## weeblebiker (Apr 3, 2003)

*Re: FV-QR (EL DRIFTO)*

hey don't feel too bad.
I'm pulling my engine out tonight because the timing belt im gear key sheared and the gear worked loose enough to drop the timing belt and ruined the snout of my balanced 3a im shaft, so I have to pull the im shaft out. my belt dropped off idle starting from a stop sign so I may not need to change the head, maybe, but I think I will anyway.


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## 206danebmx (May 16, 2001)

*Re: FV-QR (weeblebiker)*

Next thing I plan to do is check the flow on the injectors. The manifold is stock I'm not sure how that affects things in cylinder 3. I'm wondering if 4 egt sensors is a good idea on top of the knock sensor setup?
I feel like there are numerous people that have been running these similar setups with no issues...?


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## Jefnes3 (Aug 17, 2001)

*Re: (weeblebiker)*


_Quote, originally posted by *weeblebiker* »_naw the 11.5 afr is in gas terms, as my megasquirt display only shows gas afr. so lambda was .79 ish. 
remeber that the o2 sensor only reads lambda, and the software takes that and multiplies it by 14.7 to give afr
I think what killed the piston(s) was my over run fuel cut settings. I was cutting fuel .7 seconds after my throttle closed. so going up and bouncing around 15 psi than letting the throttle slam shut = super lean decel = detonation









_Modified by weeblebiker at 5:30 AM 8-9-2009_

Go a bit fatter on full boost. Seriously. aim for ~ .70 lambda 
NO fuel deos not / cannot detonate. So as long as your decel cut is 
a true 'off' at the inj. your fine. I do suggest longer time before cut off, say ~2-2.5 seconds, this stops the 'pop' on upshift.
checking decel: turn off decel cut off, check afr when you close tb from
WOT and see what it 'coasting' besure its not lean here. suggect .85 lambda or richer on full decel. once tuned turn back on decel cut off.
-Jeffrey ATwood


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## 206danebmx (May 16, 2001)

*Re: (Jefnes3)*

quick update. I pulled all my pistons out and all of them have failed ringlands, wtf. I don't see how this is a tuning issue, I'm convinced that something else happened, maybe just too much stress on the ringlands, I mean these pistons were designed for stock power not that plus 15psi of boost.


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## sp_golf (Nov 28, 2007)

*Re: (206danebmx)*

That's strange... I've had a clogged exhaust before which caused the crank case pressures to be stupid high and didn't have any problems with the ringlands


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## EL DRIFTO (Jul 11, 2004)

*Re: (sp_golf)*

its a tuning issue


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## weeblebiker (Apr 3, 2003)

*Re: (sp_golf)*

back on the road.
from what I've read I am convinced ringland breakage is detonation.


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## EL DRIFTO (Jul 11, 2004)

*Re: (weeblebiker)*

pmd weeble


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## weeblebiker (Apr 3, 2003)

*Re: (EL DRIFTO)*

I just checked out an ignition map done by valvecovergasket for a 2L16v 8.5:1 compression on pump gas boosted to 215 kpa. my map was 10* advanced than his over most of the bost area. 
evan more evidance that my breakage was tuning and not just old pistons.


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## weeblebiker (Apr 3, 2003)

*Re: (weeblebiker)*

from this site
http://www.kb-silvolite.com/ar...id=36
"COMPRESSION RATIO -vs- COMPRESSION PRESSURE
Compression Ratio as a term sounds very descriptive. Compression ratio by itself, however, is like torque without RPM or tire diameter without a gear ratio. Compression ratio is only useful when other factors accompany it. Compression pressure is what the engine actually sees. High compression pressure increases the tendency toward detonation, while low compression pressure reduces performance and economy. Compression pressure varies in an engine every time the throttle is moved. Valve size, engine RPM, cylinder head, manifold and cam design, carburetor size, altitude, fuel engine/air temperature and compression ratio all combine to determine compression pressure. Supercharging and turbocharging can drastically alter compression pressures.
The goal of most performance engine designs is to utilize the highest possible compression pressure without causing detonation or a detonation-related failure. A full understanding of the interrelationship between compression ratio, compression pressure, and detonation is essential if engine performance is to be optimized. Understanding compression pressure is especially important to the engine builder that builds to a rule book that specifies a fixed compression ratio. The rule book engine may be restricted to a 9:1 ratio, but is usually not restricted to a specific compression pressure. Optimized air flow and cam timing can make a 9:1 engine act like a 10:1 engine. Restrictor plate or limited size carburetor engines can often run compression ratios impractical for unlimited engines. A 15:1 engine breathing through a restrictor plate may see less compression pressure than an 11:l unrestricted engine. The restrictor plate reduces the air to the cylinder and limits the compression pressure and lowers the octane requirements of the engine at higher RPM.
At one time compression pressure above a true 8:1 was considered impractical. It still is in many cases with today's gas. The heat of compression, plus residual cylinder head and piston heat, initiated detonation when 8:1 was exceeded. Some of the 60's 11:1 factory compression ratio engines were 11:1 in ratio, but only 8:1 in compression pressure. The pressure was reduced by closing the intake valve late. The late closing, long duration intake caused the engine to back pump the air/fuel mix into the intake manifold at speeds below 4500 RPM. The long intake duration prevented excess compresson pressure up to 4500 RPM and improved high RPM operation. Above 4500 RPM detonation was not a serious problem because the air/fuel mix entering the cylinder was in a high state of activity and the higher RPM limited cylinder pressure due to the short time available for cylinder filling.
The following compression guide should be considered realistic for sea level operation. Cam timing and special applications can move the recommendations around some, but in most cases the following recommendations work.
PUMP GAS (regular)
8.5:1-Non-quench 2 valve head road use standard sedan, without knock sensor.
8.5:1- Quench head engine for tow service, motor home and truck with torque cam.
9.0:1- Street engine with proper .040" quench, 200° @ .050" lift cam, iron head, sea level operation.
9.5:1- Same as 9:1 except aluminum head used. Light vehicle and no towing.
10:1- Used and built as the 9.5:1 engine with more than 220° @ .050" lift cam.
10:1- 4" and smaller bore, high RPM cam, cold plugs, good fuel distribution, full power limited to 30 seconds W.O.T.
RACE GAS
13:1- is the highest compression ratio suggested with unrestricted gasoline engines.
13:1- Plus o'kay with restricted intake engines at high RPM.
ALCOHOL
15.5:1- is the highest compression ratio suggested for unrestricted alcohol fuel engines. Probably will lose power at 15.5:1 in most applications.
Satisfactory use of 14:l - 17:1 compression engines can be made when restrictor plate or small carburetor use are mandated by race sanctioning. High altitude reduces cylinder pressure, so if you only drive at high (above 4500') altitude, a 10:1 engine can often be substituted for a 9:1 compression engine. General compression rules can be violated, but it is usually a very special case, such as a 600 Hp normally aspirated engine in a 1500 lb. street car with a 12:1 compression ratio. The radical cam timing necessary for this level of performance keeps low and medium RPM cylinder pressure fairly low. At high RPM, detonation is less of a problem due to chamber turbulence, reduced cylinder fill time, and the fact that you just can't leave the above conbination turned on very long without serious non-engine related consequences.
Piston temperature and Hp are interrelated. High Hp per cubic inch engines not only make more Hp, but they make more heat. How the excess heat is handled has a significant effect on total engine power and longevity. Some engines have ceramic exhaust port insulation lines that allow cooler cylinder head operation, while keeping exhaust temperatures elevated for efficient catalytic converter operation. The same ceramic-type insulation on a piston top has not been quite so successful. Ceramic insulation on pistons can insulate the piston too well. The piston stays cool while the very top surface gets so hot that the intake air is immediately heated on contact with the piston. The heated intake charge expands and reduces the air flow into the cylinder. 
On the compression cycle, the now over heated intake charge offers more resistance to being compressed and, because of the higher compression pressure and temperature, is more likely to detonate during combustion. Ideal piston temperatures in an operating engine would suggest refrigeration during the intake and compression stroke, and incandescence during the combustion and exhaust stroke. The advantage of a hot piston on the power stroke is that less combustion energy is going to be absorbed by the piston. So far, it is not practical to heat and refrigerate a piston 6000 times a minute. However, if the incoming air is not heated by the piston and the piston reflects the heat of combustion, you start to approach ideal conditions. A polished piston runs during the power stroke. A smooth polished piston runs cooler than a non-polished piston even after combustion deposits have turned both pistons black. A cool, smooth piston will transmit a minimum of heat to the incoming fuel air mix.
The KB Performance Piston line gives the racer a real "out of the box" advantage with smooth, diamond-turned piston heads. A polish is relatively easy to achieve and does improve the already excellent reflectivity of the KB Piston. If a buffing wheel is used on hypereutectic pistons, you will note a gray cast to the finished piston. The gray results from the exposure of the silicon particles that are dispersed throughtout the piston. Our forged pistons will polish like chrome.
Experimental work to reduce piston heating of the incoming fuel mix has been very limited, but in theory a thin coating may prove to be beneficial. A thin, smooth coating over a polished piston should still reflect combustion heat while reducing caron buildup and protecting the piston polish. It is easier for a thin film to change temperature with each engine cycle than it is for the whole piston to do the same. A thin film can be cooled by the first small percentage of inlet fuel mix, allowing the main quantity of fuel mix to remain relatively cool. Tests have shown that polishing the combustion chamber, valves and piston top can increase Hp and fuel economy by 6%. So far it has proven difficult to keep a coating on a polished piston.
All this polishing is counter to the practice of dimpling the combustion chamber. Dimpling has been shown to put wet flow back into the air flow and improve combustion. We do not recommend dimpling, but do suggest cutting a small discontinuity close to the valve seat to turbulate wet flow. Some bench flowed cylinder heads encourage fuel separaton at the inlet port. If a small step is added at the valve seat to force the wet flow over the resulting sharp edge, fuel will re-enter the air stream and give you the same affect as dimpling, only without losing the benefit of a completely polished chamber.
As you re-atomize wet flow you will improve combustion and most likely need to install leaner carburetor jets. Leaner jets compensate for the excess fuel that is available when we flow is put back into the air/fuel mix. Significant additional Hp gains can be had with careful attention to cylinder-to-cyliner fuel distribution by allowing all cylinders to be set "just right." More on this in the "Combustion Science and Theory" article.
Combustion chamber design work has increased steadily in the last ten years. Some of the work is mandated by the EPA and some is the result of race engine development. Some of the smog work has actually enhanced race engine development. Combustion chamber science is now focused on the effects of swirl, tumbling, shrouding of the valve, quench, flame travel, wet flow and spark location. A combustion chamber shaped dish piston can improve the flame travel in the combustion chamber, but may increase piston temperature. A new step dish allows the flame to travel further and expand more before it is stopped by a metal surface. This rapid flame travel makes it unnecessary to run big spark advance numbers. Ideally, we would like to be able to initiate ignition at top dead center since this would reduce negative torque in the engine that now results from spark advance. We are some time away from a practical spark ignition system that will make optimum power with a TDC setting. Don't go out and buy dished pistons for your non-supercharged open chamber 454. The advantage in flame travel is more than offset by the low compression ratio this conbination yields. Small combustion chambers respond well to dished pistons, expecially reversed dome "D" cups and step dish. A 400 small block Chevy can use a 22cc D-cup piston and still have 10.4:1 compression. A trend in modern engine design to smaller combustion chambers with slightly recessed piston tops is resulting in more Hp per cubic inch with less fuel.
Ignition timing on most KB installations should be 30-34 degrees total with full mechanical advance dialed in. More advance may feel better off the line, but the engine lays down as the combustion chamber components come up to temerature. At the drag strip set timing for maximum MPH, not best ET. Even at max MPH (max Hp) you likely have 4 cylinders wanting more timing and 4 cylinders wanting less. We worry about the cylinders that want less. Too much spark advance will shorten the life of any engine, sometimes drastically."

and this 
"This chart shows the final compression ratio in your engine by combining the static compression ratio read down the left side and the amount of boost applied to the engine across the top. Use this chart shown below as a guideline to determine the proper amount of maximum boost level for a specific application.
Final compression ratios above 12.4 to 1 are not recommended for use with "premium pump gasoline." The higher the final compression ratio the higher the octane rating of the gasoline must be in order to help prevent detonation and serious engine damage. 
Final Compression Ratio (FCR) = (Boost / 14.7) + 1) x CR
Boost = Maximum Boost
14.7 = Psi. at Sea Level
CR = Engine Static Compression Ratio
Altitude plays an important role in determining compression ratios. If the altitude in the area where the vehicle is driven is significantly higher than sea level then the compression ratios will vary. To determine the effects of the altitude on a calculated compression ratio use the following formula:

Correct Compression Ratio = FCR minus [(altitude/1000) x 0.2]
Compression Boost (in pounds per square inch)
Ratio
2 4 6 8 10 12 14 16 18 20 22 25
6.5:1 7.4 8.3 9.2 10.0 10.9 11.8 12.7 13.6 14.5 15.3 16.21 17.0
7.0:1 8.0 8.9 9.9 10.8 11.8 12.7 13.6 14.5 15.3 16.2 17.0 17.9
7.5:1 8.5 9.5 10.6 11.6 12.6 13.6 14.6 15.7 16.7 17.8 18.6 19.5
8.0:1 9.1 10.2 11.3 12.4 13.4 14.5 15.6 16.7 17.8 18.9 19.8 20.9
8.5:1 9.7 10.8 12.0 13.1 14.3 15.4 16.6 17.8 18.9 19.8 20.9 21.9
9.0:1 10.2 11.4 12.7 13.9 15.1 16.3 17.6 18.8 20.0 21.2 22.4 23.6
9.5:1 10.8 12.1 13.4 14.7 16.0 17.3 18.5 19.8 21.1 22.4 23.6 24.8
10.0:1 11.4 12.7 14.1 15.4 16.8 18.2 19.5 20.9 22.2 23.6 24.8 26.0
10.5:1 11.9 13.4 14.8 16.2 17.6 19.1 20.5 21.9 23.4 24.8 26.2 27.6
11.0:1 12.5 14.0 15.5 17.0 18.5 20.0 21.5 22.9 24.5 26.0 27.5 28.9

The above information was supplied by Blower Drive Service,"BDS." 
Blower Drive Service


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## weeblebiker (Apr 3, 2003)

*Re: (weeblebiker)*

considering I get 240 psi on a wet compression test, , looks like I'm gunna stay @ 6-8 psi and get the timing back up to where is should be and call it a day.
15psi is probably out of the pall park for what I'm doing. 



_Modified by weeblebiker at 3:15 AM 10-2-2009_


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## EL DRIFTO (Jul 11, 2004)

*Re: (weeblebiker)*

maybe you could retard your cams for a bit less comp
thats an aaweful lot of comp for a turbo
obviously you can get away with more compression on sc than turbo @ same boost


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## weeblebiker (Apr 3, 2003)

*Re: (EL DRIFTO)*


_Quote, originally posted by *EL DRIFTO* »_maybe you could retard your cams for a bit less comp
thats an aaweful lot of comp for a turbo
obviously you can get away with more compression on sc than turbo @ same boost

ha-ha
I always thought total compression, mechanical +/- (forced) induction, was total compression. it's good to know superchargers make a better quality compression than turbochargers








maybe I can mimick turbo lag by retarding the cams too! 
but at least I'll be able to say I'm pushing 20 psi boost in even if it doesn't make any more hp than 6 psi and I only get 10 mpg and I melt my cat.
If I was worried about highest hp #'s, yah I'd drop the mechanical compression to like 8:1, run a stock cam and put a bigger turbo on it. because you can put more air-fuel in each cylinder for the total compression limit of the fuel/motor design.
but I'm not, my aim for this build was instant low rpm power with lots of torque in the mid 2k rpm range.
kind of an all add, with no lag type thing over my na motor. so I can have as much power as I wan't in any corner without having to downshift into second gear all the time.
I just wasn't sure what the ball park for total compression was till recently,,,,after popping a piston.
aw heck,,,I gunna try and go back to bed
8:16 am! is this server in england or something










_Modified by weeblebiker at 8:19 AM 10-2-2009_


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## EL DRIFTO (Jul 11, 2004)

*Re: (weeblebiker)*


_Quote, originally posted by *weeblebiker* »_
I always thought total compression, mechanical +/- (forced) induction, was total compression. it's good to know superchargers make a better quality compression than turbochargers









it's way overgeneralized to say that sc is quality compression
when better eff is better
sc driven off crank, turbo off ex pulse so that's why turbo need less comp .5 or so
but that being said, a properly sized ebay turbo will make more power per psi of boost that the best sc, with less compression somehow
shelby or Michelle Mouton could help your lag out

that's allot going on there, 
timing will even help your spool so add just a little @ a time
it should have a sweet spot bell curve
way b4 your prev settings


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## rabbitchaser (Sep 20, 2004)

i blew my ring landings in my abat 
but then again i was running 25lbs of boost on a stock motor, running c2 obd1 chip. 
i blame mine on way to much boost on a stock compression motor, im now working on going c2 head spacer to drop the compression, im back to my stock cam and going with 23 lbs of boost. im very confident in the c2 tune just cant wait to feel 300 whp in my caddy


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