Tuning ls ecu with hp tuners pro#
Tuning ls ecu with hp tuners mods#

A 3' diameter exhaust is only 1/4' (9%) larger than 2.75', but it's 20% larger in cross-sectional area. The 3.5' exhaust is 27% larger in diameter, but 65% larger in cross-sectional area. Doubling the diameter will quadruple the area. Remember that area grows at double the rate than diameter when it comes to a circles. No matter how I cut the math it points to a single 3.5' pipe straight (or 3/4' larger than where I am now).

That puts me at about 1071CFM needed or just over 3.5' diameter single straight pipe as I sit. Most guys go with 2.2CFM per HP and 115CFM per sq inch of exhaust pipe cross section. My current exhaust flows a max of 624CFM before it represents a restriction (and that's straight with no bends), I need 970CFM or 55% more cross-sectional area. The exhaust right now is about 65% the size it should be, so it's a restriction and a pretty good one at that. The TB will get done along with the Intake in time.

This is all taking into account my engine as it sits. I'm well over that, going even larger will have nil an effect at those engine speeds from where I currently sit. To that point, my VE tables at my cruising speeds are ~50%, that would mean that optimally a single straight 1.5' exhaust pipe is optimal. In either case they are both about 3.5'.Īt lower RPMs I will lose some scavenging, but it actually won't be too noticeable from where I am at now due to my LT headers and Y-Pipe and VE chart. At 7K (assuming 100% VE, a 6% drop from 6100RPMs) I need a 3.53' diameter exhaust, straight piped. My engine at 6100RPMs needs a 3.40' diameter single pipe exhaust, straight (using. Of course the pipes are not straight, but it doesn't have to be perfect just close. I need 115CFM per square inch of cross sectional straight pipe to match my 970CFM of exhaust gases. Extrapolating the data from my PE AFR correction tables and the data log AFR on the dyno chart I can conclude that at 6100 RPMs my engine is at 106% VE.Īt 6100 RPMs and 106% VE the engine is pulling in 664CFM of cool air, but pushing out about 970CFM of burned air and fuel.

Tuning ls ecu with hp tuners pro#

A straight pipe will flow ~ 115 CFM per square inch of cross-sectional flow area.Īt 6100 my VE table is maxed out in the tune (tuner pro RT won't let me go any higher than 99.61%) and my AFR is ~12.5:1. Once the exhaust pipe goes to a certain size it should stay there or get bigger only, never smaller. Even if it's set up to go from 3' to 3.5' to 3' again it's losing power. And to that you should never reduce exhaust size down stream as it introduces a restriction. The further away from the engine the smaller the pipes need to be due to cooling, but with my engine VE exceeding 100% and pushing 6600 rpm (going to be 7K in the future) the math shows the 2.75' diameter over axle pipe is too small.

Tuning ls ecu with hp tuners mods#

And it'll rise more with future mods too. But, that will go up as I open the exhaust. Optimally I should be at about 3.5' single at my dyno powered. Click to expand.I understand exhaust gas velocities, but at my power level a 2.75' pipe (and a single 3') is a pretty good restriction to power.