i guess i could have titled it better, im really looking for what would keep me from running a lower lsa cam on a fuel injected engine and why? just thought i'd toss this one out. ls1 tech wouldnt give me a straight answer and i figured you "Advanced" guys may be able to provide an answer.


im about to get a custom grind done and i see plenty of guys going with 110 LSA cams on these motors. i want to know why you dont see anyone attempting a 108? could it be done with custom tuning, MAF-T, drilling the TB, tricking the IAC ect?? what do you guys think? BTW im an M6 guy so i dont really have to worry about a converter. ;D just looking for a little imput.

engine mods:
ported heads, Dynatech LT's, 226/232 114 cam.

 

I'll take a crack, but understand you're in uncharted territory.

108 LSA vs 114 LSA is 6 cam degrees more, or 12 crank degrees more (your durations are measured in crank degrees). You gained as much overlap as if you went to a 234/248 cam (roughly).

Because the overlap is so much larger, you will proportionally lower the rpm at which exhaust scavenging adds torque. Basically, your mid-range torque should increase, though your upper rpm torque will die off sooner and faster. You may need to shift at only 6300 rpm.

It's really a crapshoot at idle and low rpm. A 108 LSA may be small enough that even off-idle you're getting a little scavenging benefit, so torque is good. If the scavenging only kicks in at 1500 or 2000, then it may be an utter dog off-idle.

Basic summary: narrower, steeper torque curve, higher peak torque, lower peak power rpm, possibly lower peak HP, and idle is a crapshoot.

Good luck

 

Exactly what Joe said, and remember when you go with an LSA of 114 you will have a much broader powerband than a 108, including a smoother idle.

 

Joe,

Nicely put. thats the kind of information i was looking for. im looking to decrease my lower end Tq so i can launch easier on slicks, and make up for it further down the track. ;D uncharted territory is acceptable because ya live and you learn and thats hotrodding.

 

Maybe its just me, but normally you fix traction problems with more traction, rather then less power. All you'll be doing with this method is slowing down your car's potential ETs. Only in Extreme conditions would you want to slow the car down to help traction.

JM $.02

 

extreme cases like hooking hard on the street with a 4th gen? ;D

all im really going for is effectively mooving the powerband up a bit and to retain the driveablity.

 

It mainly has to do with the fact that your LS1 PCM fuel and timin tables dont even have matrixes covering the MAP readings you would get from a cma like that, from what I understand. Majority of EFI cars all run wider LSA so their MAP radings stay where the ffactory pcm can cover them. Theirs ways around that