I've been doing a bit of tuning latley and have some concerns. I datalogged a bunch of runs at 10psi with no timing retard and found that I was getting a little bit of knock. In all of these runs my EGT would peg at 850 (1562). I then datalogged a few with some timing retard. My EGT's shot up alot faster and I had to let off at about 6k because my EGT's hit 900 (1652) BUT the knock was gone. I then tried richening up the fuel mixture in the high RPM's with timing retard and the EGT's seem to drop and I could take it to 7 grand and not even hit 900 (1652). When I pull timing it seems the A/F mixture get's Leaner. Does this make sense to anyone??

From talkign to you, and knowing yoru setup,and what kind of timing your car gives, you wre probably getting a LOT of knock at 10 psi with no timing retard, which was destroying the "adiabaticness" (.......all the engineers know what I am trying to say, asn adabatic-ness isn't a word) of your cylinder and you were acutally transfering a LOT of heat through yoru cylnder walls, head and pistons. this is "bad". This is what makes heat spots in cylinder walls and what melts aluminum pistons. since the heat is leaving the cylinders via teh hard parts, less is exiting through the exhaust (where it should exit) and you saw 1550 on your egt. Once again, this will put a hole through one....or all of your pistons and flatten out your rod and main bearings. once you retarded timing, you probably found your car was too lean to begin with at that temperature and all the excess heat caused by detonation and normal combustion left via the exhaust ports at alarming temperatures (beyond 1650). once you richen it up, you shoudl be able to acheve an even 1600 on cylinders 2 and 3 and 1550 on cylinders 1 and 4. It is best to tune on a dyno, and always know that unless you are running glue for gassoline, 30 degrees of timing and 10 psi on 8.5:1 compression pistons just doesn't mix. most of this is explained on my site.



A.D.P.
"...If you do too much, people become dependant. If you do to little, people loose hope. If you do it right, people won't be sure you've done anything at all."
bring it on............

Isnt 10 psi a bit low to be seeing knock? Especially with lowered compression. I thought 10 psi would run perfectly with lower compression and not knock at all. Imagine what the people running 8-10psi on stock compression are geting. Their engines must be knocking like crazy.

hmmmm.... ive ran 15psi with no timing retard. EGT's never got over 1550 though. seems weird you have an upgraded fuel system such as yours, and are leaning out at just 10psi. do you have an inline pump also?

My Fuel and Ignition system consist's of this: 2 fuel pump's (in-line and in-tank), 550 injectors, S-FMU, S-AFC, Programable DIS-2, and the map sensor for boost retard. I've found that I am getting the bugs worked out. Dyno is next! We'll see how my car likes C-16 (117 motor octane) :D

The main thing that greg forgot to mention is that his car has about 30 degrees of spark advance (timing) at wide open throttle as most people have about 23. so if he retarded 7 degrees of timing, it would be like he was runnign the same spark advance as other people's cars. and yes, 30 degrees of spark advance on 10 psi with 93 octane gas will blow sh!t up ;)

A.D.P.
"...If you do too much, people become dependant. If you do to little, people loose hope. If you do it right, people won't be sure you've done anything at all."
bring it on............

Greg, what MAP sensor are you using and where can I purchase it from. I'm pretty sure I need one for my Crane and I'm not sure what to get....thanks bro....

MSD Map Sensor, 3-Bar, blown/turbo applications up to 30 lbs. boost
Part # MSD-2313
$47.99

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