Dyno'd the Cobra today

[BAD03COBRA]

and I'm a little surprised on a couple things...

the whole reason I went to my tuner's was bc my wideband was hitting a couple lean spots going down the track. It would stay right around 11.8-11.9 but have a few spots where it jumped to 12.2. So I wanted to make sure it was the sensor going bad.

This is a OEM motor w/ 32k on the clock. Posi Dragon TB, Posi port w/ 2.93 / 4# pullies, LT's w/ no cats, no muffs, solid axle w/ 4.10s and I was in full race trim on the 28x10.5 ET Drag slicks.

C4 has a 4800 stall..so the runs went pretty quick....I also had ice in the ice box bc thats how I run the car. and these are the first pulls Ive done w/ the C4 since it went in over a year ago!

first run - 23 degree's timing
492whp and 455wtq and it WAS lean. car was mostly from 12.0 to 12.2 on the run. so adding a little fuel into the mix.

2nd run - 23 degree's timing
499whp and 466wtq

now that was all set, I wanted to try an extra degree of timing bc at the track on 24, I gained 1mph and close to a full tenth in the same day / conditions.

3rd run - 24 degree's timing
498whp and 465wtq.....whaaaat??? no change at all. the graphs looked identical which is boggling my mind. I guess I'll have to try it again at the track and see what happens.

now onto the good info....

4r70w w/ converter locked, drag radials - 468whp / 465wtq
4r70w w/ converter locked AND slicks - 445whp / 445wtq
4r70w w/ converter UNlocked (like the C4), drag radials - 436whp / 391wtq

C4 w/ an UNlocked converter AND slicks - 499whp / 466wtq

seems on MY car, slicks cost the car about 20hp. and with both trannies being UNlocked, the C4 is up by 63whp and 76wtq to the wheels. A guesstimate of about 83whp and 96wtq if the 4r70w was done UNlocked and with slicks.

overall Im pretty happy. the car is squared away, and I came home with 7 more hp and 10 more ft lbs.

[MY-S281]

Great Post!~

Jake that is a decent gain for sure, your car is a Monster!~

I'm betting the goals you have set for yourself will be forth coming !!

No question you're a pro at ripping that beast down the track...

[TorchRedSVT]

dude.....9 second slips with 499/465 ?? All I can say to that is

VERY impressive!!

[BAD03COBRA]

Great Post!~

Jake that is a decent gain for sure, your car is a Monster!~

I'm betting the goals you have set for yourself will be forth coming !!

No question you're a pro at ripping that beast down the track...

thanks man! I just wish I knew why the degree of timing did something at the track and not on the dyno...

[lxfiveo]

Pretty common to see slicks put down lower numbers Jake, so you may find your new tune does more than you think at the track. As far as the drivetrain goes, I don't really pay attention to anything other than converter efficiency. I could put a stick in my car and lay down a grand at the wheels, but I will for sure put down worst times at the track.

[BAD03COBRA]

Pretty common to see slicks put down lower numbers Jake, so you may find your new tune does more than you think at the track. As far as the drivetrain goes, I don't really pay attention to anything other than converter efficiency. I could put a stick in my car and lay down a grand at the wheels, but I will for sure put down worst times at the track.

I dont care about the numbers either, but its cool to see all of the differences with similar setups and diff trannies. although my car is prob up 20hp or so now over the t-56 and 4r setup, still close

[SmokinStang]

Great data......

I just wish I knew why the degree of timing did something at the track and not on the dyno...

No all DYNO's are created the same!!

Drag racing: 1/4 mile prediction based on dynamometer measured power
Horsepower figures are a strong predictor but do not guarantee a specific 0-60 mph, 1/4 mile elapsed time (ET) or 1/4 mile speed. An engine accelerating in a vehicle experiences different conditions than on a dyno. G forces and different temperatures as well as different modes of vibration in a vehicle can cause significant differences in power output.

Inexpensive "inertia dynamometers" commonly provide insufficient loading, and complete their "test" in less time than the real world 1/4 mile takes, causing inherent power value errors, due to unrealistic internal engine temperatures.
More sophisticated dyno systems are capable of "loaded testing", which can potentially recreate the same temperatures as on the drag strip.
In engineering units, the power figures used should be "True" or "Effective" horsepower scale.
________________________________________________

Also could be perhaps be variables in Parasitic loss
(See post below: step-by-step instructions on determining (and entering) driveline parasitic loss values into DYNO-MAX - for any chassis dynamometer)
SmokinStang

[SmokinStang]

How do I determine Parasitic Loss Values?

"How do I derive the ‘Driveline Power loss’ values to enter (on the Run Information - Vehicle tab)" These parasitic drag fields are used to return lost horsepower (and torque) - consumed by the dynamometer's shaft bearings, drive belts, etc. - back into the displayed test results. For example: the roller's windage and pillow block bearings rob energy that would normally be delivered to the pavement. It does not matter if you are doing inertial or steady state (absorption) testing, this is delivered Hp that never makes it into the data-acquisition computer!

Fortunately, it is relatively easy to perform your own coast down test, utilizing DYNO-MAX itself, for determining a very close approximation of these non-linear power losses. You will also need a small vehicle and a floor jack.
1) Place the vehicle onto the dyno without using straps! Wheel chocks alone will suffice, as no significant torque will be applied during this test.

2) If the dyno has a load cell, it must be properly calibrated and zeroed before beginning. The correct inertia values (for the roll assembly and any other drive components) must also be entered.

3) A floor jack under the axle (or an overhead lift for a bike dyno) should be in place - to lift the tires off the rolls during coast down.

4) Prepare DYNO-MAX for a manual recording. But do not press the console's Record button – yet. Stay in Knob (no load) mode!

5) With the test area clear, gently accelerate the vehicle to bring the dynamometer up to normal test speed. Then signal the driver to lift off the throttle and disengage the vehicle's transmission.

6) With the rolls coasting, jack the tires just clear of the roller(s).

7) Press DYNO-MAX's Record button to capture the coast down.

8) Once the dyno falls below 30 MPH (this takes some time), press Pause and then save the recording.

9) Edit Graph Set Up and use Time Averaging 0.1 second to graph Engine Power (only). Uncheck the Y-axis's “Lock Low to Zero” box, as you are graphing negative (lost) power!

10) Modify the Driveline Power loss Hp and Exponent fields (on the Run Information - Vehicle tab) to flatten (zero out) the negative horsepower graph line. Experiment to get the flattest overall line!

Tip: Try an exponent of 2 as a good average for the various parasitic loss curves involved. Leave the ‘RPM’ field at 5252, as it is merely a scaling anchor for generating the exponential curve.

11) That's it, these two fields' values may now be entered into the next New Run as your default Driveline Power loss values.

[BAD03COBRA]

yea, I know it could be the dyno, just figured a change in power would show.

[KandyRoush]

my car gained no power from 12 to 14 degrees of timing. It picked up 50hp when leaning it out a from 11.2 to 11.7 tho. My car would not respond to timing but drastically to a/f. Its probably due to the efficiency of the setup.