Dyno results

dfink · 08:03 AM

Ran the car on the dyno yesterday and results were a bit less than I expected. I was warned that the mustang dyno would be less I had seen on the dynajet so I was prepared a little anyhow. Bet run on the mustang was 175 with 158lb torque. The operator estimated a 25% drivetrain loss so flywheel somewhere around 218. This is with a fresh top end and rings, 964 grind on the cams, SW chip, fabspeed cat bypass and B&B sport muffler. The car however feels much stronger than it used to. The last dyno I did was on a dynajet a couple years ago and it was 203HP with 187 lb torque.
The car however performed flawlessly. No smoke made 4 runs and stayed at 180*. The guy kept asking if I wanted to wait to cool down and I just said don't need to look fine I don't think he believed it could run like that and not overheat. Didn't even have a fan blowing on it. Was probably 65* in the shop with the outside door open.
Boy 6700 rpm sounds like a lot sitting on dyno. After the 6700 run we turned the test down to 6400 as the HP was dying off at 6200 anyhow. The torque kicks in around 3700 and holds good to about 5800. Even with the chip in I still that kick in the pants around 4000 rpm when on the street er... track.

a couple results below is this reason

I think run 2 rpm at 6700 max

and I think 4 rpm at 6400 max edit:I think the A/F had fallen out

hobieboy · 02-22-2007, 08:39 AM

Well, if it feels stronger & better, and your bud-meter said so on the track, then it probably is.

I have grown to not trust absolute dyno numbers - sensors can be off (I have experienced that with inaccurate AFR reading), different day/different temp will definitely produce way off numbers.

Eagledriver · 02-22-2007, 10:56 AM

I think something is wrong with those numbers. With the A/F ratio you have and an SW chip you should have much more power than that. Also 25 percent power loss is unlikely (unless you have a sportomatic). Did you check to see if you are getting full throttle?

-Andy

dfink · 02-22-2007, 11:30 AM

I did forget to pull the carpet out as the throttle is adjusted with carpet out. I checked however to see how far open the throttle is going and the rotation is about 3/16 short of hitting the stop on the throttle body. I have it set about 1/16 short with the carpet out so I hit the stop on the pedal before the stop on the throttle body. That could account for some lowering I don't know how much difference that will make. The curve is nearly identical to the one I made on the dynojet 2 years ago the numbers are just lower. In fact even the dip in the A/F mixture is there on the old one. What did happen is the torque curve moved giving me about 300-400 more RPM worth of good torque. I am attributing that to the cam grind.
Maybe a few tweeks on the chip and then I will re-run (with carpet out) before I adjusted the throttle I was only at about 80% throttle that was a good 1/2" from the stop.

jtratza · 02-22-2007, 02:49 PM

25% correction sounds really high. I been told to use 15% to 18%. I dyno'd mine Jan 2006 after rebuilding in 2005 and got 210 hp and 186 torque at the rear wheels on a dynojet at Motorsport Tech in Houston. Mainly a Corvette/GM tuning shop. Last week I took the car to ProTechnic (also a Dynojet) near Houston to get a AFM read because the first one couldn't give me a reading and I thought the engine was running rich. Turns out the mix was fine only a little rich in the mid range. Result this time was 225 hp and 198 torque again at the rear wheels. Difference I believe is the engine is now broken in after the rebuild and a change to the exhaust. Both were corrected to ambiant temp. I suspect the second dyno was a little optimistic but ProTechnic does do a lot of 911 race prep. They did say this is for base line use however which I read to mean it may not be 100% acurate as others have pointed when using dyno figures.