DonE

Ironically, I was picking up valve cover gaskets at the parts store and I let it idle for about 3 - 4 minutes while I ran in - you think this would bring temps down. This happened about 5 min after that.

These are the same pistons that lived through the detonation problem I had last year, so it's possible they were not in good shape. However, I had a shop do all the measuring to make sure they were up to specs before re-installing. These are custom JE's at 8.0:1CR running on pump gas.

DonE

The best fuel around here (south Atlanta) is 91 octane. I fill it with Chevron or Amoco only.

BrianKeithSmith

Dude.... at 8:1 compression, at 1 bar of boost you are at approx 13:1 compression.

I know with my old engine, running stock compression, with 1 bar of boost my pistons were destroyed, and pitted with 93 octane and a good AFR.

That's when I started running 100 octane, but by then, the damage had been done.

Brian

BrianKeithSmith

How far are you from Jackson Ga, they have Sunoco 100 octane (just for future reference).

Georgia Sunoco 100 Octane Locations

Allen Oil
2809 Limerick Street
Savannah, GA 31404

(912) 691-1015




Atlanta Dragway
500 East Ridgeway Road
Commerce, GA 30529

(706) 335-2301




Jones Petroleum
407 East 2nd Street
Jackson, GA 30517

(770) 775-2386




Mansfield Oil Company
1025 Parkway S.W.
Gainesville, GA 30501

(770) 532-7571




Road Atlanta Raceway
5300 Winder Highway
Braselton, GA 30517

(770) 967-6143




Shorty's Quick Stop #10
101 Rodger's Street
Eastman, GA 31023

(912) 374-5632




W.W. Fowler
7514 Lee Road
Lithia Springs, GA 30122

(770) 948-9414

My87Targa

id say predetination, but you said you didnt see anything wrong when you looked. when your running 91 octain does your car ever ping?? i know when i put low grade fule in my n\a car it misses and runs like crap. id think the same should hold true for a modded turbo, unless your car was directly tuned for 91 octain. even then it can still miss.

sorry to hear about what happened, specially as spring is finally here

sand_man

So sorry Don!

DonE

Since I have to buy a min order of 4 pistons to replace one (remember, custom order), I will just order 6 new pistons.

You have a good point though. I am sending the bad piston to JE for comments and recommendations. There are lots of 8.0CR turbos around with no problems. However, I don't want to go through this again and I might order 7.5 or lower.

If I was under boost when this happened, I would understand it better. But I was in traffic and had not stabbed the throttle for a long time.

And thanks for the 100 octane info. Jackson is 45 min away, so not bad.

Rgds

m42racer

A classic case of running lean. Always on the intake side. The damage was done while under boost, the end failure that told you so was while idling. Better check the wiring, Injector and mapping. Do you have any knock control? Better get something. Had you had something, it may have told you what was going on. Sorry to see what happened, but this is what happens often. The plug must have been white hot. Did you look at the plugs during your mapping?

senna21

PREDETONATION (knock). I'll get in line behind m42racer and say you need to get a knock sensor on that engine. The GM sensors are very robust and inexpensive. Get it wired into your ecu, if your ecu doesn't have an input for it get another one that does! When the sensor reads knock (predetonation) it'll pull timing. Even with proper A/F mixture you can still get knock. Although as you run lean that'll increase the chance for knock this may not be a case of running lean causing it. Sometimes you get some bad gas and that's all it takes.

kens911

where did you get the list of 100 octane stations? do they have any here in south florida? there used to be a place out by the indian reservation where people used to get av gas for their air boats but they no longer sell it.

JBL930

why not use octane booster? Does it work? we get 98 octane fuel here in the uk, is that enough for a 500bhp 930??

kens911

octane booster doesnt really do any thing. When the bottle says it increases octane 3 points it meant from 93 to 93.3 not 96 unless you get the several gallon cans of moroso octane booster.and 98 ron in the UK is more like
93 r+m/2 octane in the us I went through all of this with my euro carrera the gas flap said 98 ron and the best I could find here was 93 it turns out they are pretty much the same just a little different way of measuring it. found that out from my neighbor who purchases fuel for the military from all over the world.

JBL930

is 98 good enough then??

kens911

should be

senna21

Sorry to say but octane "ratings" vary from country to country. If memory serves me correctly your "98" rated octane is the exact same as our "93" rated octane. Don't think that the extra "5" points gives you any extra stability because you don't really have a higher octane content.

Just as your 0-deg Cel isn't any colder than our 32-deg Fer.