Questions about boost, afr, timing trade offs

[cc-rider]

I'm going to be installing some LT headers on my car. Currently has the KB 2.8 supercharger. Running 8 lbs of boost. I know that LT headers can reduce boost ~2 psi as a result of it being a more efficient engine after header install. I see that most people pulley down and get back that lost 2 psi back.

I'm wondering if anyone has left their boost lower after header install and tried to get some more timing and afr at the lower boost levels, rather than pulley down and get back that boost? Theoretically the engine should be able to take more timing and afr at 6 psi than it would at 8 psi. Especially these high compression LS3's. And less heat from the blower too at lower boost levels so IAT's should be lower (2psi = 20 degrees I think?).

Or is this a case where 2 psi more boost will always trump any timing/afr/IAT gains?

[supergt99]

I think the reason is because the 2psi boost is worth more power than what the timing would give you.

[cc-rider]

Any other thoughts here? Nobody has ever tried maximizing 5-6 psi on the LS3?

[Moreair1]

In my opinion that isn't based in fact and may be wrong, but I would think it would be safer on the motor running 8lbs than trying to push the envelope on timing, and you might get more answers if you asked this in the tuning section

[fif_gen_powa]

Just because the boost is lowered to 6psi because the engine now is less restrictive doesn't mean the same thing as running 6 psi without headers. You have to think in terms of cylinder pressure or hp/power output. Those are not going to be lowered by adding headers and in theory increase. You may not be even to add any timing at all because of that.

So yes more boost is a no brainer

[Unreal]

IATs don't go down because PSI levels go down. IATs are more dictated by how hard/fast you spin the blower and its map/efficiency. You are still spinning the blower at the same speed.

Call KB and I'm sure they could explain how to maximize power and how it should be setup.

[agent5]

I'm not an expert but when I ran 7.5 PSI initially with my stock LS3, I ran in to some minimal knock retard, we lowered the timing by 2 in certain areas on the map, the overall loss of power was minimal compared to the overall gain from boost. Now, I don't know how that applies to your application but it seems like that's the rule of thumb.

[cc-rider]

Thanks guys. I was kind of thinking that the 2 lbs of boost would always trump the afr/timing. I may play around with 6 lbs just to see what happens. I'll report back if I see anything noteworthy.

[Unreal]

For reference, each PSI of boost is typically 30-40rwhp depending on power adder.

Each degree of timing is ~10-15rwhp, depending on how close you are to peak timing/etc. AFR even less.

So boost>timing>AFR when it comes to power.