Anyone care to guess how this happened?
#31
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What do I do then, I certainly don't want my pistons to look like poor DonE's, if the best we can get in the uk is equivalent to 93 then I’m on a time bomb????
#32
No. 93-US (or US equivalent) should be fine. Just don't push up the boost above 1bar. Also if you are running a lot of boost switch to a step colder plug.
I'm just letting you know that you guys have got about the same stuff as we do here. I've said it before and I'll say it again. Boost doesn't kill engines. Knock kills engines. But, as you increase your boost (or compression) you increase the chance of getting predetonation.
I'm just letting you know that you guys have got about the same stuff as we do here. I've said it before and I'll say it again. Boost doesn't kill engines. Knock kills engines. But, as you increase your boost (or compression) you increase the chance of getting predetonation.
#35
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Originally Posted by WERK-I
DonE,
I forgot your previous post regarding your engine details. I seem to recall you are using the Electromotive EFI, yes? Did you twin-plug the engine?
I forgot your previous post regarding your engine details. I seem to recall you are using the Electromotive EFI, yes? Did you twin-plug the engine?
Timing from 100 kPa starts at 24 and ends up at 15 (208kPa). Timing at 2300 rpm is 34, then comes down to 30 at 3500 then 28 from there.
Since there is not sign of detonation anywhere else in the engine (examine plugs, pistons), I am considering this is an injector problem. You guys know that I try to be scientific about what I am doing and I try to do it with quality equipment. Well, with 2 blown engines in less than 5000 miles, that method is out the f***ing door. Right now, it looks like I will order 6 new pistons since the min order is 4. Now I have to decide which CR, as well as have the injectors tested. Obviously, this has been a nightmare.
I hope this helps you guys with your cars.
#36
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Originally Posted by DonE
Yep and yep.
Timing from 100 kPa starts at 24 and ends up at 15 (208kPa). Timing at 2300 rpm is 34, then comes down to 30 at 3500 then 28 from there.
Since there is not sign of detonation anywhere else in the engine (examine plugs, pistons), I am considering this is an injector problem. You guys know that I try to be scientific about what I am doing and I try to do it with quality equipment. Well, with 2 blown engines in less than 5000 miles, that method is out the f***ing door. Right now, it looks like I will order 6 new pistons since the min order is 4. Now I have to decide which CR, as well as have the injectors tested. Obviously, this has been a nightmare.
I hope this helps you guys with your cars.
Timing from 100 kPa starts at 24 and ends up at 15 (208kPa). Timing at 2300 rpm is 34, then comes down to 30 at 3500 then 28 from there.
Since there is not sign of detonation anywhere else in the engine (examine plugs, pistons), I am considering this is an injector problem. You guys know that I try to be scientific about what I am doing and I try to do it with quality equipment. Well, with 2 blown engines in less than 5000 miles, that method is out the f***ing door. Right now, it looks like I will order 6 new pistons since the min order is 4. Now I have to decide which CR, as well as have the injectors tested. Obviously, this has been a nightmare.
I hope this helps you guys with your cars.
#37
Originally Posted by WERK-I
.....OR an errant/erratic fuel pressure problem. Fuel pumps or pressure regulator?
#38
Does the Tec 3 show the Timing at the crank? Are your Timing numbers inclusive of the machanical base timing?
Take comfort that these engines when built and mapped correctly do last. Something is amiss, so before buying anything, find out what the cause was. Talk to someone that knows these engines and does this all the time. Call the guy I PM'ed you. He will tell you very quickly what is going on, and what to look for.
When a Piston melts like yours has, and on the Intake side, this always points towards a lean condition.
Take comfort that these engines when built and mapped correctly do last. Something is amiss, so before buying anything, find out what the cause was. Talk to someone that knows these engines and does this all the time. Call the guy I PM'ed you. He will tell you very quickly what is going on, and what to look for.
When a Piston melts like yours has, and on the Intake side, this always points towards a lean condition.
#39
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What I meant to say was, is a modified 930 with standard pistons and cylinders putting out 490bhp at 1bar of boost (along with other mods obviously) safe with 93 octane fuel, forgive me for being dumb I don't do any work on my car I leave that to the specialists, I’d like to be fore warned
#40
Don,
Sorry to see this happen. It looks like a tuning issue to me, knowing that Essa tuned the first engine means it was gonna happen on that one. I know quite a few people whose cars have blown up from his tuning, I can't believe he is still in business.
It looks like the car was running really lean on cruise. u can do that on a water pumper but not on our air cooled engines. maybe it is an injector but what cylinder went on the engine before, unless its the same one i would doubt it, but inj are cheap in comparison to building an engine over and over.
Sorry to see this happen. It looks like a tuning issue to me, knowing that Essa tuned the first engine means it was gonna happen on that one. I know quite a few people whose cars have blown up from his tuning, I can't believe he is still in business.
It looks like the car was running really lean on cruise. u can do that on a water pumper but not on our air cooled engines. maybe it is an injector but what cylinder went on the engine before, unless its the same one i would doubt it, but inj are cheap in comparison to building an engine over and over.
#41
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How and where do you install a knock sensor on a 80's 911 Turbo? I thought there was too much rattling going on with the timing chains and all for one to do any good? I understand the later model 911 Turbos have one though because the engine is quieter.
Originally Posted by 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.
#42
Knock sensors can are fitted to 930 engines. Most systems have the ability to dial out the engine noise, or set a threshold that above this point, you will consider any noise, Knock. The sensors are fitted under the Throttle mount between it and the case. The damage caused to the above Piston would certainly rattle the case, as does most knock. Anything to give an indication of detenation is worth the trouble our friend now faces.
#43
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Originally Posted by WERK-I
.....OR an errant/erratic fuel pressure problem. Fuel pumps or pressure regulator?
#44
Don,
After the first engine problem, were the pistons Zygloed? Any microscopic cracks will cause a heat concentration and speed the erosion of the material under high heat loads. A crack could have originated at the base of the valve pocket, where the piston head is the thinnest.
Was this piston out of one of the previous split cylinders? Once a high strength aluminum alloy is over heated, it becomes annealed and looses significant strength.
After the injectors and ECU wiring are checked, it would be interesting to have JE or someone else thouroughly check that piston, and maybe a couple of the others. Zyglo and hardness. The original detonation problem could have had something to do with this.
Food for thought.
Win
After the first engine problem, were the pistons Zygloed? Any microscopic cracks will cause a heat concentration and speed the erosion of the material under high heat loads. A crack could have originated at the base of the valve pocket, where the piston head is the thinnest.
Was this piston out of one of the previous split cylinders? Once a high strength aluminum alloy is over heated, it becomes annealed and looses significant strength.
After the injectors and ECU wiring are checked, it would be interesting to have JE or someone else thouroughly check that piston, and maybe a couple of the others. Zyglo and hardness. The original detonation problem could have had something to do with this.
Food for thought.
Win
#45
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Originally Posted by m42racer
Does the Tec 3 show the Timing at the crank? Are your Timing numbers inclusive of the machanical base timing?
Take comfort that these engines when built and mapped correctly do last. Something is amiss, so before buying anything, find out what the cause was. Talk to someone that knows these engines and does this all the time. Call the guy I PM'ed you. He will tell you very quickly what is going on, and what to look for.
When a Piston melts like yours has, and on the Intake side, this always points towards a lean condition.
Take comfort that these engines when built and mapped correctly do last. Something is amiss, so before buying anything, find out what the cause was. Talk to someone that knows these engines and does this all the time. Call the guy I PM'ed you. He will tell you very quickly what is going on, and what to look for.
When a Piston melts like yours has, and on the Intake side, this always points towards a lean condition.
One of the problems I am still facing is all the opinions on how to tune this thing. And the opinions are far apart - one has very aggressive timing, another states nothing above 30 degrees. One states 11.5 AFR on boost, another says nothing below 12.5. I set cruise AFR at 14, others say I could have gone higher.
The only two tuners I have used have only set WOT timing and AFR's. That's not tuning to me.
Another issue is CR. Should I stay at 8.0:1, tune better and keep the boost under 1 bar or should I go down to 7.0:1, tune better and run boost at 1 bar?
Yet another issue: deck height. Currently, I'm at .069. The reason for this is that my heads have been shaved by the previous owner to bump compression. I ordered special 8.0:1 CR pistons and had my machine shop measure everything to give me proper deck height. He told me 069 rather than 039 because that's how the math works out to get proper squish and CR. No one agrees with him on this issue except me because he has my parts and he is a reputable machine shop/builder/NA tuner.
WTF....