I took my car to a local club's dyno day. My car put down only 306 rwhp and 295 rwtq. I know something has to be wrong. Before it dynoed the numbers in the signature. It seems to be running really rich. The wideband shows an AFR of about 12-12.5:1 from 2500 to about 4000. After that, it gets progressively worse, finishing at about 10.5:1 at around 6000. The torque curve and horsepower curve don't look too out of whack, just low.

I had a friend datalog the runs, so when I get the file I will post it. He showed me where I was getting up to 9 degrees of knock at higher RPM, and one or two while they were running through the gears. I will scan the dyno graph on Monday at work and post it.

Any suggestions? Could the rich air-fuel ratio and knock be sapping that much power? Where's the other 80 hp?

See the mods in the sig.

Thanks,

BRAD

 

maybe it was the dyno you were on

 

if you run too rich you can cause detenation to occur. sounds to me like thats what happening. you should not be that rich. maybe check the program, but also check things like fuel pressure, plugs, wires, air filter, O2s. never know what it could be if your tune is right

 

Actually if you're too lean detonation is an issue, not rich.
Steve...

 

oh hell talk about a brain fart. your right my bad.

 

Here's the Dyno Graph

I know there's a lot to check. It's sure frustrating to spend all this money and get the same results as with bolt-ons. Everyone was kind of shocked with the results.

 

I know i'm in the same boat as you. I have a question what springs are you running and what lifters? and how many miles are on your combo? Phil at AI said my springs might be worn out because i have 20k miles on my setup or my comp OE replacement lifters are collapsing.

 

i sent you a pm llafro

 

I am using Comp 987 springs and Comp OEM replacement lifters. I don't think from the graph that I am having valvetrain problems at high RPM. The graphs don't look bad. It's just the numbers are well short of where they should be.

The car will be going back out to my mechanic soon, so we'll see what the problem is. Hopefully he can find it. The first thing will be to fix the AFR.

BRAD

 

What DYno did you run on? A mustang dyno reads consitterably lower figures and could account for most of your lower than expected numbers.

Real dumb question, but I didn't see PCM tune listed in your mods. Has it been tuned for your curret set up?

As far as your other problems, that overly rich condition could cost you as much 15-25hp on the top end. You are also loosing 25-35HP because of the spark knock. Do you have a LT4 knock module? I didn't seen it in your mods list, If not your getting false knock because of the Roller Rockers. Fix these things and you will see a big improvement.

 

80 hp is a huge dip. Maybe you should take the car back to where you dyno'd the 380 and see if the number holds. Might be just a bad dyno.

Sister's b-friend went to a dyno with a car group. He has a 409 stroker with a 150 shot. On the dyno the car put down 230rwhp and another 50 more with a 150 shot. He was pissed. But then a guy with a nitro car who runs 9's dyno'd his and got 380 rwhp. The dyno was fubared.

I tell you what, I would think you would feel a 80hp loss no?

 

Sounds like he was on the dyno that Horsepower TV uses

 

LOL! Isnt that the truth! I laughed when I heard that. He even had the video from the dyno. That Nitro car almost jumpped off the rollers..............with 380 rwhp. LOL!

 

The dyno was a Dynojet. It didn't seem to be giving out crazy results with the other cars that were there. A couple of LS1 cars put down 320 +/- just before me. A cam and heads LS1 with nitrous put down 450 or so right before me.

I do have an LT4 knock module. The car was dyno tuned when all the stuff was installed almost two years ago. I had felt that the car was "off" somehow, which is why I wanted to dyno. I have had some things fixed over time, such as a leaking EGR tube and a leak in the collector gasket on the driver's side header. I also had a burnt plug wire that was causing a miss.

I am wondering now if I don't have a dead cylinder. That would explain a lot of the loss. I will have to try the old spray water on the primaries trick tonight.

BRAD

 

well if you find anything out let me know. Our graphs look very very similar. So maybe we have the same problem. How many miles is on your heads and cam set up?