Melted a piston - unsure why.
Launching!
Joined: Jan 2018
Posts: 283
Likes: 0
I run pump gas turbo cars at 11.3-11.5 no leaner. stock LS1 on 11psi on our best pump fuel I would have 9 degrees through the mid range creeping up to 11 tops provided the exhaust was still flowing well at high RPM. otherwise would be a flat 9 deg if it was choking up over 6000rpm. im hoping the 152 IAT was F not C. I would have pulled 2-3 degrees out by 65 degrees IAT on Pump gas.
Originally Posted by Luke19901
I run pump gas turbo cars at 11.3-11.5 no leaner. stock LS1 on 11psi on our best pump fuel I would have 9 degrees through the mid range creeping up to 11 tops provided the exhaust was still flowing well at high RPM. otherwise would be a flat 9 deg if it was choking up over 6000rpm. im hoping the 152 IAT was F not C. I would have pulled 2-3 degrees out by 65 degrees IAT on Pump gas.
Launching!
Joined: Jan 2018
Posts: 283
Likes: 0
sorry would be pulling 2-3 degrees at 65deg C or 155 ish F. turbo pump fuel cars seem much more prone to IAT caused det than a PD blown combo on pump fuel.
Originally Posted by 99camaroturbo
Little more info here, took the short block apart. All 7 other pistons look great, no signs of detonation or extreme heat. #6 rod is bent pretty good, the others look good. All bearings look mint. I’m still wierded out by the fact #1 had issues and #7 didn’t.
BTW, thanks for starting this thread. Great info being discussed as a result of your loss.
Launching!
Joined: Jan 2018
Posts: 283
Likes: 0
bent rod means massive dynamic cylinder pressure.
I have seen plug porcelain fall out once before with no signs of det evident when engine was pulled down. was a boosted application on pump gas. happened twice!!
assembled with identical components the second time round, flow tested injectors and they were within 5%. I threw them in the bin anyway and replaced them. ran flawlessly for the next 12 months until we snapped factory crankshaft. cause of that was square edge left when machine shop opened up oil galleries creating a starting point for a crack.
I have seen plug porcelain fall out once before with no signs of det evident when engine was pulled down. was a boosted application on pump gas. happened twice!!
assembled with identical components the second time round, flow tested injectors and they were within 5%. I threw them in the bin anyway and replaced them. ran flawlessly for the next 12 months until we snapped factory crankshaft. cause of that was square edge left when machine shop opened up oil galleries creating a starting point for a crack.
TECH Fanatic
Joined: Feb 2015
Posts: 1,080
Likes: 178
bent rod means massive dynamic cylinder pressure.
I have seen plug porcelain fall out once before with no signs of det evident when engine was pulled down. was a boosted application on pump gas. happened twice!!
assembled with identical components the second time round, flow tested injectors and they were within 5%. I threw them in the bin anyway and replaced them. ran flawlessly for the next 12 months until we snapped factory crankshaft. cause of that was square edge left when machine shop opened up oil galleries creating a starting point for a crack.
I have seen plug porcelain fall out once before with no signs of det evident when engine was pulled down. was a boosted application on pump gas. happened twice!!
assembled with identical components the second time round, flow tested injectors and they were within 5%. I threw them in the bin anyway and replaced them. ran flawlessly for the next 12 months until we snapped factory crankshaft. cause of that was square edge left when machine shop opened up oil galleries creating a starting point for a crack.
Launching!
Joined: Jan 2018
Posts: 283
Likes: 0
I would certainly think that to be correct. I have seen a ring land break off a piston from really bad det on a boosted car without the piston top arearing like it had been rattled to bits
LS1 Tech Stories
The Best V8 Stories One Small Block at Time
6 Common C5 Corvette Failures and What's Involved In Repairing Them
Pouria Savadkouei
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph
Verdad Gallardo
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked
Pouria Savadkouei
Top 10 Most Powerful Chevy Trucks Ever Made!
Hennessey's New Supercharged Silverado ZR2 Has 700 HP
Verdad Gallardo
Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes
Verdad Gallardo
Awesome K5 Blazer Restomod Comes With C7 Corvette Power
Verdad Gallardo
10 Camaros You Should Never Buy
10 LS Engine Myths That Refuse to Die
Verdad Gallardo
melted a piston Curious as how OP low timing/ rich afr results in bent rod on cylinder #6 ? What's the effect of rich afr on dynamic compression with boost? Not familiar with fi so legit question. Also, old school plug reading was wot, clutch in, engine off and then pull the plug. Wondering what the process is now; post 17 OP states will try a new set? Edit- first question answered post 67
Last edited by txazformula; Jul 7, 2018 at 01:05 PM. Reason: updated posting
Launching!
Joined: Jan 2018
Posts: 283
Likes: 0
Curious as how OP low timing/ rich afr results in bent rod on cylinder #6 ? What's the effect of rich afr on dynamic compression with boost? Not familiar with fi so legit question. Also, old school plug reading was wot, clutch in, engine off and then pull the plug. Wondering what the process is now; post 17 OP states will try a new set?
Appreciate the response. Looks as if Lance and ddnspider are both right about afr and spark but working from opposite ends in the tune? Rich and low timing/ lean and high timing + high iat tear it up. OP, any pics of the piston or your boost plugs you can post up?
I will go so far as to say that Lance's take on AFR could work IF the timing is low enough....but there are more benefits to running a richer AFR (not 10s rich) as I've pointed out in several threads.
9 Second Club
Joined: Nov 2003
Posts: 13,616
Likes: 185
From: Norn Iron
Which several factors? EGT and drive pressure?
I don't use an egt monitor but I can report from experience that drive pressures don't change noticeably in relation to fuel quality. Only thing that changes IME is mechanical changes.
I don't use an egt monitor but I can report from experience that drive pressures don't change noticeably in relation to fuel quality. Only thing that changes IME is mechanical changes.
Launching!
Joined: Jan 2018
Posts: 283
Likes: 0
I have seen many pump fuel turbo LS tuned by guys with an import background come in running 10.50-10.80 AFR and about 4 degrees more timing than I would ask for. every one that ive retuned makes more power, more torque. the engines sound more crisp and rev cleaner and are more responsive on the road. all I did to them was come up to an 11.6-11.8 AFR and run timing I consider appropriate (ballpark 4 less than the import tuners file).
touch wood, theyre all still running
attached is a twin turbo SBE 5.7 on pump. "ovebang" file is from other tuner.
Last edited by Luke19901; Jul 8, 2018 at 11:04 AM.
Thread Starter
Teching In
Joined: Jun 2018
Posts: 21
Likes: 0
I’m considering switching to e85, since we are having such a good discussion here, I’d like to ask for some input on what you guys prefer for afr on the gas scale and timing? I think I should be good to go if I switch to e85 and leave my timing table alone? Should fix my iat and octane problem?
Launching!
Joined: Jan 2018
Posts: 283
Likes: 0
your combo 9psi 93 pump 11.50AFR 12degrees starting to pull timing from 60 degrees C IAT
11psi93 pump 11.50 AFR 10 degrees starting to pull timing from 60 degrees C IAT
9 psi E85 11.80-12.0AFR 16 degrees starting to pull timing from 60 degrees C IAT
11psi E85 11.80-12.0AFR 14 degrees pulling from 60*C IAT
13psi 11.80 AFR 14 degrees pulling from 60*C IAT
11psi93 pump 11.50 AFR 10 degrees starting to pull timing from 60 degrees C IAT
9 psi E85 11.80-12.0AFR 16 degrees starting to pull timing from 60 degrees C IAT
11psi E85 11.80-12.0AFR 14 degrees pulling from 60*C IAT
13psi 11.80 AFR 14 degrees pulling from 60*C IAT
Thread Starter
Teching In
Joined: Jun 2018
Posts: 21
Likes: 0
Another question. Why is it stoich for pump gas is 14.7, and you target say 11.2 for wot boosted, and E85 stoich is is 9.x and you target in the same 11.2 area?!? Why do you target richer than stoich on pump gas and leaner than stoich on e85?
also thank you for that Luke, I’ll go convert 60* c to F so I know what I’m looking at lol
also thank you for that Luke, I’ll go convert 60* c to F so I know what I’m looking at lol