What James said. "Tuning". Also, the dyno graph looks like they never turned on the "smoothing function". I'd find out. Whenever you do a dyno run, its also a good idea to have a wide band O2 so you can get a plot of the Air/Fuel ratio. That drop off in torque around 3500 is really hurting you.

 

I talked to ben on aim, the smoothing function is on 0, thats why its not that smooth. And he has true duals, so he doesn't need cutouts.

 

You guys keep mentioning the tuning, but it's the same guy that tuned LT4POWR's car that put down 416 rwhp. I would think he knows what he's doing. A log of the dyno run and an a/f graph would help a ton.

 

Yep, Scott knows tuning, I'm sure his A/F (and timing) are/were optimized for the best results. Did they do any kinda scanning or data logging? I'm sure the hot weather isn't helping the #s, but the SAE correction should help adjust (some) for it.

 

The "smoothing" entered into the program will affect the smoothness of the curve. The smoothing setting should be shown on the dyno sheet. Without that, its hard to interpret the "jaggedness".

The dyno sheet shows the "SAE" correction factor (1.04 on the 8/10/06 pull). The "1.04" is your correction for the test conditions. The test conditions are shown at the bottom of the sheet, but can't read them because they printed the shop address and phone number on top of it. In effect, they gave you 4% extra HP to correct for the ambient conditions. It made 357HP undcorrected.

 

I hope you get it all worked out. I have AFR 190 LLoyd/BRE setup, almost the EXACT same setup as yours but I havent been to the dyno. Went to the track with it and could only muster 12.6's @ around 109-110 I think. I always thought my setup was slow but I wanted to get it on the dyno and make sure there was nothing mechanically wrong first. Keep us updated

 

nope, when i talked to bret about the heads, he said Lloyd ported 'em


btw, i'm not BASHING anyone in any shape or form. I'm just looking for pointers on what you guys may think i need to check and what-not

fwiw, i have Jet-hot Longtubes w/ 3" true duals (dr. gas x-pipe, flo-pro's, dumped).

first things first i'm going to address this stock LT4 intake, going to double check to see if it's been hogged out for the 58mm TB. and I'll probably take it off and send it to Lloyd to have him work his magic on it.

A/F ratio graph i will get tomorrow, but it's right at 12.9-13.0 all across the board, w/ it going around 13.1-.2 up top. nice and straight.

timing is around 34-6 degrees i believe, he played w/ timing and didn't really affect the numbers at all.

thanks for all the help guys, i will keep ya'll informed on what actions are being done and the consenquences of 'em

-Ben

 

I wasnt implying you were bashing, I just noticed in the forsale post that the guy said bret ported them. Thats all. Gotta give credit where credit is due, thats all.


Be sure to find out whether or not the AFR190's were setup for the LT4 raised runner intake. The AFR190 head is setup for an LT1 intake... ports could be mismatched.

 

What kind of shortblock is this setup on?

The dip in the torque curve most likely is knock. I remember the same thing going on with my car on the dyno. My tuner wasnt very concerned because apparently LT1s always like to knock right at that rpm range. He tuned it out mostly by pulling a little bit of timing and making sure the A/F was a little fat in that area on the curve. In the final tune you could still see it a little but it was damn near gone. Also you have to make sure that if the computer is picking up knock in that area that the retard is decaying all the way back down to zero. Otherwise once it pulls the timing it wont give it back for the rest of the pull.

My motor carried peak hp between 6000-6400 kinda like yours so i think your headed in the right direction though i would agree that you do seem down on power.
However: over a 100 degree air temperature certainly does not help. the dyno is supposed to correct for it. But, the motor isnt going to be as "happy" in 100 degree air as in 75 degree air....

Steve

 

porting the throttle body holes on the intake will not make a huge difference, maybe a few HP. Something else is the problem.

 

The LT4 intake ports in the heads are taller the LT4 intake manifold ports are the same size/shape/location as LT1 intake manifold ports it just has more material on top of the ports to seal to the LT4 head but does not match the taller head ports, needs porting for that.

 

yeah my heads are set up to take either the LT1 intake or the LT4 raised runner.

I got a few things i'm going to try so I'll let ya'll know how it works out.


this is on a stock-rebuilt shortblock w/ 47K miles on her.

 

Doubt it's heads related or intake, looks more like tunning/ignition, but most likely tunning bro.

 

Yes, Lloyd did do those heads.

Yes that cam works, it's worked many times before just as well.

The big indication that something is off is the huge dip in the TQ curve from 3000-4800rpm. That thing should just climb to 3500-4000rpm and peak TQ and hold on for a bit. Did the shop who installed it DEGREE IT IN?

Scott is bad *** at tuning so I doubt it's him. I know the cam works and I believe those heads made 420rwhp plus before...... so the parts are there.

Bret

 

What kind of compression does the engine have? I know the AFR heads out of the box have a larger combustion chamber than stock, are they milled? do you know what cc the chambers are currently? What heads gaskets are you running, and did you have the block 0 decked when it was rebuilt? I'm no expert, but I'm betting that if your compression is low with that cam, it's not gonna make the power that it should.

Bret, what kind of compression do you like to see with that cam? Sounds like the same cam that I have from his description...or at least its close.