Author Topic: C20LET - Fried forged pistons nr. 2-3, 1-4 ok  (Read 40852 times)

Offline Pet

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Re: C20LET - Fried forged pistons nr. 2-3, 1-4 ok
« Reply #15 on: September 17, 2009, 04:18:25 pm »
These Wiseco's were 8.5:1, low temp thermostat (82C) and 100 octane fuel.....

Offline GintsK

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Re: C20LET - Fried forged pistons nr. 2-3, 1-4 ok
« Reply #16 on: September 17, 2009, 05:21:02 pm »
 It is not considerable as "conservative" map. It is weird map - retarded, where it can be safe at almost any advance and advanced in dangerous area. If your engine was not tuned, result is as it should be. Some seconds with hard knocking and - done. Also you use original hot spark plugs. IMO it is not a safe way. Black dots on isolator was months ago. Usually it is from knocking.

 It is rare when all pistons are melted.

Gints

Offline rob@vems.co.uk

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Re: C20LET - Fried forged pistons nr. 2-3, 1-4 ok
« Reply #17 on: September 17, 2009, 05:24:26 pm »
I'm looking at this:

What is the deck surface like between 2&3 especially in the area where those two black half moons are?

They look as if they might be pitted.

Also can you raise the pistons so that we can see the crowns more clearly?


Offline MWfire

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Re: C20LET - Fried forged pistons nr. 2-3, 1-4 ok
« Reply #18 on: September 17, 2009, 08:19:44 pm »
your map is very bad, probaly knock at 3000rpm. At high rpms you need more advance, no less.
here is little retarded map for c20let 8.5:1, safe map(not for max power).
http://img263.imageshack.us/img263/5743/mssparkv2set3.jpg
btw opel c20let stock exhaust mainfold is crap, cly 2 and 3 have many better flow.
what is your trigger tooth and rising or falling?

Offline Pet

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Re: C20LET - Fried forged pistons nr. 2-3, 1-4 ok
« Reply #19 on: September 18, 2009, 01:52:10 am »
your map is very bad, probaly knock at 3000rpm. At high rpms you need more advance, no less.
here is little retarded map for c20let 8.5:1, safe map(not for max power).
http://img263.imageshack.us/img263/5743/mssparkv2set3.jpg
btw opel c20let stock exhaust mainfold is crap, cly 2 and 3 have many better flow.
what is your trigger tooth and rising or falling?

Thanks,
  my trigger tooth is 8, trigger angle 68 (was 74), rising edge.
Here are detail pics of piston 2 and 3 + head is destroyed too :(




Offline rob@vems.co.uk

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Re: C20LET - Fried forged pistons nr. 2-3, 1-4 ok
« Reply #20 on: September 18, 2009, 02:22:59 am »
That last picture is a perfect example of detonation.

Offline NOTORIOUS VR

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Re: C20LET - Fried forged pistons nr. 2-3, 1-4 ok
« Reply #21 on: September 19, 2009, 01:51:24 am »
That doesn't look like an overly aggressive timing table @ all...


Offline rob@vems.co.uk

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Re: C20LET - Fried forged pistons nr. 2-3, 1-4 ok
« Reply #22 on: September 19, 2009, 03:32:21 am »
It doesn't have to be aggressive to get detonation.
If the inlet temperatures are too high, or the octane too low (I know that this was running 100octane fuel) then detonation can occur.
In this case it may be possible that the timing was out on cylinders 2 and 3, or it could be that the water flow was not right and the middle cylinders overheated and that this started the detonation.

Offline MWfire

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Re: C20LET - Fried forged pistons nr. 2-3, 1-4 ok
« Reply #23 on: September 19, 2009, 05:45:28 pm »
i take a look to my c20xe settings, and i have trigger tooth 9 and 69deg.
So 9*6+69=123deg, and you have 116, so you have 7 deg advance more than me. My setup is 100% correct for that type c20xe. So scope your engine again.

Offline GintsK

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Re: C20LET - Fried forged pistons nr. 2-3, 1-4 ok
« Reply #24 on: September 19, 2009, 08:21:47 pm »
I have 6*9+63=117
 ::)

Offline Pet

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Re: C20LET - Fried forged pistons nr. 2-3, 1-4 ok
« Reply #25 on: September 20, 2009, 12:48:14 am »
Thanks, I'll check it, asap I get some new pistons and head....
Here is detail of one melted piston, I must say, the most upper ring was very strong to hold together....





Offline MWfire

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Re: C20LET - Fried forged pistons nr. 2-3, 1-4 ok
« Reply #26 on: September 20, 2009, 04:04:26 am »
I have 6*9+63=117
 ::)
as i sad, i saw two types of trigger wheel on c20xe(123 deg is from one c20xe with motronic 2.8. That c20xe has heavier flywheel and blue injectors(241cc)). Difference is 6deg. So you can't only copy config for c20xe.
So far did 4 c20xe and 2 c20let, and two have 123 deg, 4 have 117deg.

Offline GintsK

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Re: C20LET - Fried forged pistons nr. 2-3, 1-4 ok
« Reply #27 on: September 20, 2009, 02:28:57 pm »
Ah, remembered: "LET" was builded from XE !

Offline Pet

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Re: C20LET - Fried forged pistons nr. 2-3, 1-4 ok
« Reply #28 on: October 22, 2009, 12:53:20 pm »
So the engine is running again and I have really 117deg version, so now I have trigger tooth 6 and 81deg angle, checked with timing light. Thanks.

Offline max

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Re: C20LET - Fried forged pistons nr. 2-3, 1-4 ok
« Reply #29 on: October 22, 2009, 02:46:09 pm »
And remember that you shouldnt drag-race before you your car is correctly mapped ;)