351W Basic Trigger Boosted Tune

[br1070]

Hey there,

This is a 351W boosted with a 7875 turbo with the proper fuel system to supply the required fuel. The board is an MS2 V3.0 running extra code see msq attached with the relay board. I am injecting fuel with 4x85 lb F.A.S.T. injectors via their tbi design. I am controlling spark with a vr sensor through a MSD billet distributor. I have not gotten into boost and have not driven the car yet as I am still trying to get it idling a little better as its hunting a bit and rich (AFR in the 12s). I am trying to construct the tables for a boosted motor and do not expect to run more than 10lbs for now but have a 5lb spring in the wastegate and have a manual boost controller. Could anybody look through the tune and let me know if I am heading the right direction with fuel, spark timing and ego targets?

Any help is appreciated,
Brad

[slow_hemi6]

I am using the same TBI. You get rubbish fuel distribution on one squirt per cycle, a lot of air passes before you get any fuel injected into the manifold. Try 4 squirts. Another thing to watch is the gm stepper motor those have, can be leaking or start to leak air through them if they are left disconnected. You can feel it at the little hole on top behind the rear throats. Not having a IAC of some form will make it more prone to hunting during cold start ups. The best idle for mine is around mid 13 AFR.

[br1070]

Thanks for the reply I will give the extra squirts a try. I dont have am iac valve placed currently....placed a rubber stopper for the time being.

Brad

[br1070]

Strange thing though....it seemed to want to hunt after the temps started going up on the motor...ill play with it some more to see if i can smooth that out.

[Digger]

I have the same setup minus the turbo. (351W, FAST TB, MSD distro) I agree with slow, you need to up the squirts per cycle. 4 is better, but I'm successfully running 2 squirts / simultaneous. I had some issues with a 4 squirts / alternating setup at WOT due to uneven cylinder fueling. Too many squirts and you lose idle resolution.

Mine idles smoothly at 13:1 AFR with a mild cam. Leaner than that and it hunts. If your cam is as aggressive as it looks on your VE table(your peak torque is at 5000 rpm, mine is 3500), you will need a richer AFR to idle smoothly because of the valve overlap at idle will draw lots of raw fuel straight through the cylinder. (O2 reads rich)

Looking at your timing table, you 2nd column should be your idle speed (900 rpm) and the 1st column should be 100-200 rpm lower than that. (As you have it set), However your idle advance is pretty high and could be dropped to add stability. Additionally and more importantly, your 700rpm column should be 0.5 to 1.0 degrees higher than the 900 rpm column. This will help stabilize idle by bumping timing as rpm sags. Timing can react faster than the IAC to control idle torque.

What you have now is inverted, so as rpm sags, timing is pulled and causes rpm to sag further.

[br1070]

Hey Digger,

Thanks a lot there is a lot of good stuff in there I will definitely try some of that out on my combo. As for the cam I know its a solid roller turbo grind and it has higher lift around .650ish but I don't believe the duration as all that aggressive. I do think bumping up the injections will help as well as backing off the timing a bit at idle. This could probably help me find a happier medium with the fueling at idle.

Brad