piston failure
Discussion
hi there
after building a gtr 640 track only (no sva possible here in switzerland) during summer, i have serious piston failure after just 100 miles of track-testing because of detonation. gail told me there are only a few reasons like: lean fuel conditions, poor fuel quality, running out of fuel under full throttle or improper ignition timing.
in my opinion none of these reasons can be responsible for failure. i run the engine with v-max 100 oct. only, the EFI-adjustement is on the rich side and i didn't run out of fuel. i didn't change anything since the engine was delivered. what happend was overheating caused by throwed belt and evt. too restrictive exhaust (track-rules).
gail will send some new pistons, i will check everything and buy a lambdasensor that's not the problem, but i would like to ask you for your opinion and experience how to prevent such problems in the future.
thanks a lot
after building a gtr 640 track only (no sva possible here in switzerland) during summer, i have serious piston failure after just 100 miles of track-testing because of detonation. gail told me there are only a few reasons like: lean fuel conditions, poor fuel quality, running out of fuel under full throttle or improper ignition timing.
in my opinion none of these reasons can be responsible for failure. i run the engine with v-max 100 oct. only, the EFI-adjustement is on the rich side and i didn't run out of fuel. i didn't change anything since the engine was delivered. what happend was overheating caused by throwed belt and evt. too restrictive exhaust (track-rules).
gail will send some new pistons, i will check everything and buy a lambdasensor that's not the problem, but i would like to ask you for your opinion and experience how to prevent such problems in the future.
thanks a lot
I think your 'restrictive exhaust' statement is rather telling.
There was a guy in the UK who fitted restricters in the tail-pipes to try and get the noise down for track. It caused so much heat that his yellow rear clip turned orange. I believe the engine also caught fire but I'm not sure of that.
Steve
There was a guy in the UK who fitted restricters in the tail-pipes to try and get the noise down for track. It caused so much heat that his yellow rear clip turned orange. I believe the engine also caught fire but I'm not sure of that.
Steve
hi steve
because of the hilborn-efi i had to use a 23° afr 220-head instead of the standard 18°-chapman head which is normally mounted on amerspeeds high-reving engines. it fits only 1 3/4" headers instead of 2" headers and its exhaust-internals seems to be designed for lower output-engines. do you belive this was "restricting" enough for such a amount of heat?
philip
because of the hilborn-efi i had to use a 23° afr 220-head instead of the standard 18°-chapman head which is normally mounted on amerspeeds high-reving engines. it fits only 1 3/4" headers instead of 2" headers and its exhaust-internals seems to be designed for lower output-engines. do you belive this was "restricting" enough for such a amount of heat?
philip
steve_d said:
I think your 'restrictive exhaust' statement is rather telling.
There was a guy in the UK who fitted restricters in the tail-pipes to try and get the noise down for track. It caused so much heat that his yellow rear clip turned orange. I believe the engine also caught fire but I'm not sure of that.
Steve
There was a guy in the UK who fitted restricters in the tail-pipes to try and get the noise down for track. It caused so much heat that his yellow rear clip turned orange. I believe the engine also caught fire but I'm not sure of that.
Steve
The actual facts of the matter were; 1/ Supertrap mufflers were used to quieten the exhaust but did not protrude far enough from the rear grill and the extreme heat from the 606 bhp 406 cu motor was pulled back into the rear clip and although there was no fire, the lights popped out and the clip was scorched by the heat 2/ The motor did not catch fire and 3/ The Ultima in question was a Mclaren orange CanAm. How can I be so sure I hear you ask? I was there on that fateful day. I was excited to see an Ultima and was looking forward to chatting to the owner (Dave Butler), needless to say, he didn't really want to talk about it after all that happened.
Back to the point in question, if the motor is making over 600 bhp 1"3/4 headers are not really large enough. Stands to reason but the more air you put into an engine, the more air has to come out. Is your motor a 377? What do you have as peak RPM?
engine was dynoed with that sort of headers but without exhaust, gail told me efi was set up on the richer side. i didn't change anything but i heard of nascar-engine failures cause of changing weather-conditions and altitude. i just can't belive lean fuel conditions are the reason because of spark-plug reading.
philip
philip
Detonation is detonation. Usually caused by spark or fuel issues. I would run a car in for at least 200 miles before loading it up and then carefully at that. If you post a pic of the piston it might be helpful. Assuming that the ignition map was done and tested beforehand on similar engines I'd wonder about fuel delivery given that you were 'tracking it'.
Also a dyno session for a few seconds at peak torque tells you nothing, you need to hold it and see what happens. I don't know how your engine was dynoed but I would run my engine in for several hours before doing the full load settings.
Read your plugs right at the bottom, not the top. My 2 cents worth
Boosted.
Also a dyno session for a few seconds at peak torque tells you nothing, you need to hold it and see what happens. I don't know how your engine was dynoed but I would run my engine in for several hours before doing the full load settings.
Read your plugs right at the bottom, not the top. My 2 cents worth
Boosted.
some pics of two damaged pistons, other two pistons only have broken rings.
http://img205.imageshack.us/my.php?im
http://img215.imageshack.us/my.php?im
http://img205.imageshack.us/my.php?im
http://img215.imageshack.us/my.php?im
heard different theorys of engine brake in. some load it up right in the beginning to prevent glasing of cylinderwalls?!
http://img205.imageshack.us/my.php?im
http://img215.imageshack.us/my.php?im
http://img205.imageshack.us/my.php?im
http://img215.imageshack.us/my.php?im
heard different theorys of engine brake in. some load it up right in the beginning to prevent glasing of cylinderwalls?!
Difficult to say imo. Not the detonation I usually see. I noticed the damage on the exhaust valve side so would concur with comments about header temps maybe being high however there's some damage on the other side of the piston which leads me to think the end gasses are getting to hot over there to. I'd have to ask what the compression ratio is and if you have a wild cam in there. Also, does the head your using have quench pads?
Oh my god, it's a domed piston!
Boosted.
Oh my god, it's a domed piston!
Boosted.
boosted
a pic of the head. quench pads are pretty big i guess. head is afr 220 with 76 ccm combustion-chamber , 4.125 bore and JE 9 ccm domes, results in a compression 11.0:1. don't know exactley what cam is used but looks pretty wild (flat and wide tops). recommended ignition timing is 38° total advance @ 2500 rpm.
spot you see on top is melted-on piston part. also melted-on alu on top of cylinderwalls. it was easy (not realy) to cut away with a knive. measures are fine.
http://img206.imageshack.us/my.php?im
a pic of the head. quench pads are pretty big i guess. head is afr 220 with 76 ccm combustion-chamber , 4.125 bore and JE 9 ccm domes, results in a compression 11.0:1. don't know exactley what cam is used but looks pretty wild (flat and wide tops). recommended ignition timing is 38° total advance @ 2500 rpm.
spot you see on top is melted-on piston part. also melted-on alu on top of cylinderwalls. it was easy (not realy) to cut away with a knive. measures are fine.
http://img206.imageshack.us/my.php?im
Thanks for the pic. It's nice and clean in the quench area. You'd also expect that on a new engine. I can't really say any more then I have already. I'd double check the compression situation in fact I'd accurately record it with fluids. I'd check the total max advance, is 38 degree's typical for your engine spec? If those come up trumps then I'd search for something which effects all cylinders and go from there.
Boosted.
Boosted.
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