Svante

Ok my friend and i went for a ride today, just a small one due to there was rain on itīs way. But we had time for some WOT pulls and i didīnt like it at all.

The engine mods are:

383 Lt1 4-bolt 12:1 CR
Srp professional light weight pistons .30 bore pistons ( flat tops )
AFR eliminator 195cc heads
Cometics mls gaskets ( quench is at 0.045" )
Scat 4340 3.75" crankshaft
Compstar 6" h-beam rods with arp 2000
Custom grinded camshaft 278/286-248/254-.621/.607-108LSA solid roller
AFR stud girdles
Edelbrock Lt1 intake, matchported with the heads
Canton racing oilpan with high volume oil pump and canton pickup.
TCI flexplate
GM Performance Lt4 camdrive
Isky racing mec, roller lifters.
Comp cams pushrods.
Comps 1,6 roller rockers.

First of all. The idle is worthless below 34-35degrees timing ( i never had this much timing on idle before, maybe because of the cam? ). Anyway the engine revs up happily when standing still and sounds pretty nasty. I pulled from 2nd gear ( automatic ) and we noticed the Lambda was way to lean ( 0.95 ) at load so i backed off. After increasing the fuel map some we tried again ( 35 degrees of timing pulling from 3000-6000rpm ) and i though it felt weak. There wasīnt any really WOW feeling over it. I was hoping to break loose some tires but nothing :/ . We tried increasing the timing on top to 40 and even 45 degrees just for a quick test but i couldīnt feel any difference... Iīm no tuning expert but it feels like something is really wrong. I was thinking of make an appointment to the local dyno and get it tuned but i donīt want to go there and pull 200RWHP... Should i try to richen it up some more? My friend noticed the lambda go to the lean direction when we were heading up for higher RPMīs so maybe thatīs the big problem?

Iīm currently running E85 and running good at lambda 1 at cruising but what lambda should i aim for on WOT?

And then there is the EFI, itīs a million possible settings everywhere, i have currently only been changing the base fuel and timing map but then there is injector timing, individual ignition timing etc etc... What else do i need to change?

ECU is Autronic SM4 and ignition is M&W Pro 14 CDI with 4 coils and waste-fire.

Please help!

/Svante.

Sliding

I'm not sure if I'm allowed to post here, but there is nice forum for
Autronic user. Maybe you'll get some more help there.
I'll send you a PM.

bjankuski

E85 likes a lambda of .78 at WOT for best power. I would check you timing, my gut feeling is your actual timing compared to desired timing is the problem. That is why you need 35 degrees at idle. I have seem many lt1's with as much as 27 degrees of timing error when compared to actual. Verify that the timing is correct and then see how it responds.

Svante

Yes you are correct. One of the problems was actually the timing mark. I built my own piston stop and compared the new mark with the mark i made previously on the damper and it was way off. The timing is now 5 degrees on idle. It can be 10 or 15 to but she runs at 5 so i let it be there. The lambda was down on 0.68 on WOT so i have some tuning to do, but she tears some tires loose now so i guess im in the right direction.

Thanks