My Dyno Results with JMS Chip.

[Tim Lester]

I went to dyno my Cobra today with a JMS chip. I did 2 base runs with the chip off, 2 runs with the first tune, 3 runs with the second tune, and 3 runs with the third.

The base pulls started off good with a 309.2 rwhp and a 299.7 rw/tq.

Once I turned on the first tune there wasn't much of an increase over the base with a 309.5 rwhp and a 301.4 rw/tq, I was not pleased. Tried it again, barely anything.

Then I tried the second tune, the power went up to 312.1 rwhp and 305 rw/tq. which was a 2.9 rwhp and a 5.3 rw/tq. increase. The other 2 were about the same.

Finally, I tried the third tune. The first pull was a 311.2 rwhp and a 302.6 rw/tq. which was a 0.9 hp and a 2.4 tq. decrease, I was kinda dissapointed. Tried it again, a little increase but not much. Finally, the last run was a good one. I was quite pleased:-D

 

[Tim Lester]

Base vs. Final (3rd Tune)

 

[Joe Lynch]

Tim--check the correction factors printed below the graph. Someone changed something. There is no way you would get a bump like that throughout the hole rpm range just by making another run. What was changed? How did it go from 311 to 316 on the same tune after everything was warmed up?

Where was the dyno operator taking the air temperature and humidity readings from? Did he make a bunch of runs without checking the temp, then check it before the last run and change the temperature or the humidity?

Also, you nearly have to go back to the base tune to make the last run just to see the effect the warm trans and rear end fluids had on the base.

Joe

 

[Tim Lester]

Joe- Nothing was changed. I let the car sit for 10 mins. between the first pull and the last pull with the 3rd tune. His wideband O2 was not working on the last 2 pulls. Right off the street with a 15 min. cool down, chip turned off the car made 309 rwhp like you see. Then as I started changing chip tunes, I did not shut the car off, don't know if it made any difference, but with the last run with the 3rd tune, I shut the car off. Then adjusted the chip. And like I said earlier, the last 2 pulls with the chip on the 3rd tune, I let the car cool for 10 mins. Air temp. outside was 20*, but doesn't the DYNO correct for air temp.? I made 10 pulls with an hour.

 

[Joe Lynch]

Tim--The dyno computer has to be told what the inlet temp and the site elevation and the humidity is. I think some of the newer Dynojet installations have instruments directly connected to the computer. If the sensor was in the right place, then the input was probably OK. But, if the ambient temp warmed up during the hour you were testing, and the operator input a change in temp for your last run, it would change the correction factor slightly and maybe contribute to the difference, that's all.

If he did that, it may mean your earlier runs need the same correction, and that may make the difference between the switch settings more consistent.

If the data was input correctly for the early and the last run, the gains look reasonable to me. But the three runs on the last switch setting should be closer together than you got.

Joe

 

[Lateapex]

So, the first pull was without the JMS chip functioning -- Ford control? I see the comparison you posted showed 7200rpm on the base pull, how did you get to that rpm?

 

[Tim Lester]

The chip was pluged into the computer but was turned off. The only thing that I can think of is that the guy running the dyno and pushing the buttons did not stop the data transfer after I let off the gas. I was doing the driving and he was pushing buttons like I said.

Tim

 

[Lateapex]

I was interested because the fuel-cutoff is 7000, normally, and high on my list of changes is raising the rev limit. So, the baseline hp is the result of the other mods you've done, listed in your email?

 

[Tim Lester]

Yes everything you see in my sig is whats giving me the HP. My revlimiter has been rasied to 7200rpm.