C20LET - Fried forged pistons nr. 2-3, 1-4 ok

[Pet]

Yea, you are bloody right 
But now I have inside the block old XE machined Mahles with new rings, CR aprox 9.5:1. So I am planning to tune the engine on slight boost (max 0.6-0.8bar) with knock control. And then, if all will be fine I re-bore the block for my new set of JE pistons. I am starting with this spark table now (max boost is now 0.25-0.3bar).

[MWfire]

you have to much rumping up with rpms(difrent from 7000 and 3000rpm). Usually 6-7deg difrent.
BTW MBT on c20let is before knock on good fuel.

[Pet]

Hi all, I would like to ask someone about injector/spark fire sequence. When I am looking around user pages, forum etc. I am more and more confused if I have set the right inj/ign sequence. So I found on Peter Jensen user page (VW Corrado G60, 1-3-4-2 engine) this timing picture (http://www.vems.hu/wiki/index.php?page=MembersPage%2FPeterJenseninjector original page)


From this timing diagram I'm reading:
1-3-4-2 - spark
4-2-1-3 - inj
For Vems it means:
h[0] = 04 01 02 08 ..  (Pre_Inj00 - cyl1, Inj01 - cyl2, Inj02 - cyl3, Inj03-cyl4)
h[2] = 40 50 40 50 ..  (Wasted Spark: 1&4 or 4&1 on Ign259-channel 5, 2&3 or 3&2 on channel 4)

This sequence looking good for my engine (now without cam sync). Idle is nice and smooth, then it pulls in any RPM range well.
But then when I switch second (CAM trigger) on, engine will not start. (I have 2-nd trigger set to raw 24, it means
 it reacts on falling edge of CAM pulse ('cause rising edge - raw 25, is near my primary trigger).
I tried to change h[0] and h[2]
h[0] = 01 02 04 08 ..  (it means 4-3-2-1 inj sequence)
h[2] = 50 40 50 40 ..  ( 3&2-4&1-2&3-1&4 spark) 

With this setting engine idling nicely (2nd trigger still active), but after 3000RPM there are missfires or what, and it's running bad.
My wiring is checked twice, inj0 is realy in cyl 1, inj1-cyl2 etc. so I am really confused how to set up, or what is the right setting for this C20LET (XE) engine. Thanks for any help.

[Pet]

Little up, I have changed trigger tooth to 12 (TDC atfer...then 45) and it seems it works well. Plugs have quite good color, haven't ?

[Sprocket]

Yea, but why only pistons 2-3 ??  1-4 are hitted to, but absolutely not so much like 2-3.

Only just picked up on this.

I suffered plug failure on cylinders 2 and 3 on Nitrous. I spoke to the experts as to why only 2/3 failed when they were fed with nitrous on oposite sides of the distribution block. Their answer is that the middle two cylinders combustion temperature will always be higher as those cylinders are surounded by other cylinders on each side, where as 1/4 are only surrounded by one cylinder on one side. The other contributing factor was the amount of advance I ran, and I would tend to agree with them on that one, as Even though the engine was not knocking, the advance was most likely beyond MBT, even after pulling 2 degrees out on Nitrous. Basicaly the peak cylinder pressure was happening early which raises combustion temps.

[Sprocket]

Little up, I have changed trigger tooth to 12 (TDC atfer...then 45) and it seems it works well. Plugs have quite good color, haven't ?

Have you checked the TDC after Trigger value with a timing light? Plug colour looks good. maybe a little lean, or it could be a temperature of the plug. perhaps try a #8 plug and check the difference?

[Pet]

Yes, it was checked at 0deg and 30deg advance during idling; I have marks on the flywheel, all was absolutely in one line. Under boost (0.6bar) I have it very rich, around AFR 11, in atmo area around 14.7.