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.

MY_2K_Z

iTrader: (1)

Lol pull 2-3* at 65* iat? That's nuts man, not sure where you live but my car only has only seen sub 65* a couple times and through the summer ambient temp is 95-105 so my iats are 100-130*.

tblentrprz

65c?..

Luke19901

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.

epfatboy

iTrader: (3)

I think it is time to talk about your injectors, what are they, buy them new/used, flow data if you have it....

BTW, thanks for starting this thread. Great info being discussed as a result of your loss.

Luke19901

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.

tblentrprz

Massive dynamic cylinder pressure due to preignition or detonation. Fuel and timing not right with knock limited fuel for that combo. Pic of failed piston?

Luke19901

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

txazformula

iTrader: (8)

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

Luke19901

stupid rich afr and low timing and cause pre ignition or dieseling which causes the same damage as detonation from too much timing. cylinder pressure during detonation is massive in comparison to clean combustion

txazformula

iTrader: (8)

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?

99camaroturbo

ddnspider

iTrader: (26)

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.

truckdoug

iTrader: (25)

I just don't see Lance's approach working with pump gasoline, which varies so wildly in blend and octane.

stevieturbo

And why would it not work ? He's covering several factors, it cannot do anything but work.

truckdoug

iTrader: (25)

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.

Luke19901

100%. boosted on pump will be more stable and less prone to det at an 11.2-11.5 then it is at 12.0-12.2. provided the timing miles off.

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.

99camaroturbo

Luke19901

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

99camaroturbo