Dynamometer Results & Comparisons - LSX BMW M3 little down on power? your input

Here's the setup.

99' LS1
LS6 intake
Stock LS6 heads, milled .005" stock valves w/ Patriot double springs.
232/232 112 .595 Comp Cam hydraulic
Fidanza Al flywheel
Powerbond UD pulley
Full length headers w/ 1.75" primaries w/ 3" collectors.
into 3" pipes into X pipe back out to 3" then steps down to 2.5" pipes into dual 2.5" in, dual 2.5" out Spintech sportsman XL muffler (yes just one).
no cats

Stock TB
Stock MAF

made 394rwph 375tq

Intake air temp was 98F on a 70F day, so that's a bit high. I plan on shielding the filter. The IAT sensor is in the 90 degree elbow just before the TB.

I'm wondering if the muffler is at all restrictive, or the step down from 3" to 2.5" pipes. I will probably dyno it again w/ muffler removed to rule it out.

Could the valve springs be too stiff for stock valves?

A friend of mine made 368rwhp on a 02 Z06 w/ just Cat back and cold air intake. So that got me thinking about where my setup is not optimized.

I'd appreciate any input.

Video of dyno

http://www.youtube.com/watch?v=_YdXDJsIwio

What type of EMS are you using?

What type of EMS are you using?

EMS? Engine Management System? Stock GM PCM that has been tuned. AFR at WOT is right at 13:1. That's w/ the gas analyzer in the muffler.

EMS? Engine Management System? Stock GM PCM that has been tuned. AFR at WOT is right at 13:1. That's w/ the gas analyzer in the muffler.
I think If you upgrade to a standalone computer you will be more happy with the tuning results.

I think If you upgrade to a standalone computer you will be more happy with the tuning results.

Really why? I've never used one and don't know anything about them.

What brand Dyno?

What brand Dyno?

dynojet

Cant see the video at work.
Trans?
Rear?
Tire size?
Also the exhaust is probably limiting it I would think at least 10hp

I think If you upgrade to a standalone computer you will be more happy with the tuning results.

Huh? You do not need a stand alone system for a heads/cam car.

I'm gonna vote towards the exhaust hurting you, as well as your cam choice. Single patterns work best when both the intake and exhaust flow is optimal. You might need to switch to a standard split to create somewhat of an exhaust crutch. LS6 heads tend to like split duration cams better also.

cant see the video at work.
Trans?
Rear?
Tire size?
Also the exhaust is probably limiting it i would think at least 10hp

t56
3.23
245/40/17

Huh? You do not need a stand alone system for a heads/cam car.

I'm gonna vote towards the exhaust hurting you, as well as your cam choice. Single patterns work best when both the intake and exhaust flow is optimal. You might need to switch to a standard split to create somewhat of an exhaust crutch. LS6 heads tend to like split duration cams better also.


Which part of the exhaust? muffler or pipe size step down?

Huh? You do not need a stand alone system for a heads/cam car.

I'm gonna vote towards the exhaust hurting you, as well as your cam choice. Single patterns work best when both the intake and exhaust flow is optimal. You might need to switch to a standard split to create somewhat of an exhaust crutch. LS6 heads tend to like split duration cams better also.

+1 The stock PCM is more than adequate at this level of modification. And, when I saw the cam specs I wasn't thrilled. Lastly, spintech mufflers have gotten a bad rap in the past for being restrictive. Just my $0.10

I am went Damian.. Make sure there are no restrictions in the exhaust.

Things to consider:

Exhaust after X
Differential loss %
That 90* bend in the CAI (can be removed by going SD tune, ie: MAFless)

But all together perhaps 20 rwhp?

+1 The stock PCM is more than adequate at this level of modification. And, when I saw the cam specs I wasn't thrilled. Lastly, spintech mufflers have gotten a bad rap in the past for being restrictive. Just my $0.10

I hadn't heard about the spintechs getting a badrap but it's believable. Anyone know of the correlation of exhaust backpressure and HP loss?

I know I have it backwards, but basically I need a set of ported heads to go with that cam. (Or should have ported heads then get a cam to go w/ the flow specs).

Here's the exhaust system

http://s486.photobucket.com/albums/rr221/B_Rooker/LS1%20BMW/?action=view&current=exhaust2.jpg

I would drop the muffler and redyno just to rule it out. As for cams, I have AFR 205's on my car - very good Int. to Ext. flow ratio. They still liked a cam with an 8* split vs. cams with less split. When I say liked, it made a good amount more peak power, and a ton under the curve.

Dyno graph

Seems about right to me. I had a very similar engine combination in a second gen RX7 (IRS) and it made like 396rwhp. I think the IRS robs some power for sure.

Andrew

That exhaust looks great! I'd definitely look into the muffler though as spintech mufflers have been known to sap some power with their "chambered" design. As Pred-Z said, that 90 degree bend isn't helping things and if the IAT is that close to the radiator, I'm sure it's not helping either. As was also stated, IRS rears eat some power, no doubt.

Good luck man!