Hey all, here is a comparison of some dyno runs. Read the Note in the picture and it explains which run is which. Why did my power drop off above 5500 RPMs after all the EXTRA mods in the Red Run? Any ideas? Or was my car just getting old? It showed gains in low end, but a loss in high end?

WTF, decreasing power mods. Maybe you should have run the same cam setup or somethin.

My guess is it has something to do with porting and milling the head. Shaun experienced power losses and a significant drop in his 1/4 mile times after porting his head. Also, with porting and milling, your actual timing will change. Who knows what the hell is goin on in there. The stock HP at the wheels in a 5 speed nonturbo is about 116hp. My advice to you would be to get a stock head, bolt it on, and see what happens. :) Good luck in whatever you do though.

I'm auto, that's why my numbers are lower. And ya, it seems like everyone that ported their heads ran slower after. But I have a question: I thought that porting might hurt low end, but improve top end. I seem to have the opposite results? I also need to advance my cam gears more to make up for the milling (which retards timing). At the time of the second dyno, my intake cam gear was stuck so I couldn't do that. Hopefully I will get better results at the next socal dyno day we're planning.

Porting should add more power at high end, unless he ported for a 25psi turbo. In my mind there is no way milling a head causes a loss in power since compression is helpful.

As he said, timing. You can mill the hell out of it all you want, but if the ECU is retarding the timing 20 degrees, you aint gonna do jack schit. Its all about tuning.

Yeah he posted after I started writing mine, I see now.

i think the red run has a lower hp level at the 5krpms+ cuz you put the intake cam back to 0, advance it 2 again, and see what happens....

yup sounds like you need to tune it take some more time on a dyno as soon as you can.

Advance the intake 2 I bet you'll see a diference.

Yes you need more overlap on the cams. To pull the aitr through the motor to take advantage of the porting and higher compression.

"The world is a dangerous place to live; not because of the people who are evil, but because of the people who don't do anything about it." - Albert Einstein



Michael J. Kulaga
e-mail: Michael_97RS@2gntDSM.zzn.com aol IM: MJKulga
http://highlander.dsmpower.com/

Injen CAI, 55mm TB, Hooker 4-1 Stepped Header, GS-T Muffler, AFX UDP, S-AFC, 8.5mm Magnecor Wires, Crane Fireball HI-6DI2, SS Clutch Line, NRG Susp. Motor Mount Ins., FU/RU/RL STBs, TSW Blade 17x7.5, Bridgestone Potenza RE730 215/45ZR-17. Front KVR Cross-Drilled Rotors & Carbon Fiber Pads

To Be Installed: Ported/Polished Intake Manifold 1/2, Rear disc brake conversion kit w/, Rear KVR Cross Drilled Rotors & Carbon Fiber Kevlar Pads, SS Brake Lines

Ahh! You're trying to compare too many things at once. When doing an experiment you only change one variable at a time. The first run was a baseline run. The second one was just the cam gears being adjusted.

The third one you've got a header, UDP, different exhaust, ported head, AND 5 angle valve job! That's 5 different mods. What mod did what? Did the header tune too much in the low end and cost you top end? You can't tell, because you are trying to compare graph A with graph B when graph B has 5 things different on your car from graph A.

It could be the cam gear settings are not right for a portedhead. They're fine for a stock one, but not a ported one. Also, the car could be pulling timing on the top end due to seeing more knock fromthe air/fuel mix not mixing as well or the same as stock.

Even though there are too many variables, I'm goign to re-assert my opinion, porting the head is a BAD idea for our cars if it's going to remain a street car. Now, if someone was making an all motor tube frame car with a 420A in it, that would be a different story, then you would have to port the head.

Once you port the head, you change everything. The combustion chamber changes could cause the flame front propogation to change, the flow properties change, the amount of "tumbling" the air/fuel mix sees changes. The head is a very tricky part to modify, and in this cse (fortunately for us) the guys at Chrysler did a good job.

I agree, porting the head should be for all motor or drag cars. My idle suffers as a result too. I know I'm comparing too many things in the last dyno, but it seems strange that there is a sharp drop off in power above 5500 rpm. There is a definite gain down low. The headers are Hotshot 4-1 too which should hurt low end and help high end. Also, I thought the UDP is supposed to give over 10 hp throughout the RPM range? I'm gonna hope to get back on the dyno soon. BTW, for some reason, my idle got really bad when advancing both gears 4 degrees - is that too extreme?