Hi folks.

I just dyno'd my 93 LT1 6spd with a P600B@8psi max boost. Other mods are ported heads, hotcam, LT headers.

Air fuel ratios are at 12.0:1.

I made 435 rwHP/446 rwTQ. Graph has some dips in it above 5300 RPM that restricted it from making more HP up top.

What should my spark advance be set at? I used tunerpro RT to set it at 28 degrees. My cheap frame scanner shows spark advance as low as 17degrees past 4500 RPM and as low as 13 degrees past 5000 RPM.

Knock retard shows 1 degree at 4000 RPM and 4 degrees past 5000 RPM.

So those low spark advance numbers dont make sense to me (ie. they would if I saw 11 degrees knock retard past 4500 RPM and 15 degrees spark retard past 5000 RPM).

What total spark advance works for you with boosted applications?

 

8psi at sea level on a stock compression LT1 on pump gas should be right around 20 degrees. Pull timing untill you dont see any knock retard and then back it off a degree or 2 to be safe. I'd also drop the air fuel to 11.8 at higher boost levels.

 

Thanks MikeGyver,

This is as I expected -

28 degrees is way too much timing and the computer is pulling timing through spark retard.

One other question, when my Auto X-Ray frame scanner tells me I have 1 degree knock retard at 4500 RPM, 4 degrees knock retard again at 5000 RPM, does this mean its now deducting 5 degrees knock retard total from my timing during that pull?

This would make sense in answering my question above.

 

KR is displayed as total instant knock retard, so it's pulling a total of 4 degrees at 5000 RPM.

 

OK, well somehow a lot more timing is getting taken out - than what is indicated by knock retard. I dont know how thats possible but somehow must be occurring for me to have it set at 28 degrees (with MAP maxed out) and then seeing only 13 degrees timing at WOT.