U7140 Engine Load Readings

[stangman_2]

I have a U7140 used by my local Diablosport authorized speed shop to custom tune my 2003 Mach 1 with ProCharger supercharger system, 42 lb injectors, Cobra pumps/tank and Autolite copper 103 plugs gapped to 0.035”. Over the last couple of months I have been attempting to diagnose a stalling/rpm dip problem with car since it was modified over a year ago. I recently discovered this problem occurs when my Predator indicates very low engine load readings. The lowest engine loads occur when I am coming down off of high rpm and using the engine to brake/decelerate. I also have a wideband A/F sensor, which goes off scale lean (>18.5:1) when this is happening. The rpm dip or engine stalling occurs when I push in on the clutch during these conditions. I needed to data log to help with the diagnosis and had contacted Diablosport about activating this function on my Predator, however was told my model didn’t yet offer it so I purchased AutoTap v3.10 software/kit to perform data logging. Relative to engine load, I have noticed a large difference in the readings the Predator gives me compared to the calculated engine load readings from AutoTap. At idle Predator gives me 15.5-17%, while AutoTap says 22-23%. The lowest readings (engine braking) on the Predator say 10% load, while AutoTap says 14%. My questions:

1) How does Predator measure or calculate engine load?
2) Which is more accurate…Predator or AutoTap? In other words, which engine load reading should I believe?
3) I am working with my tune shop to richen the mixture during light load conditions, however does Diablosport have a base tune for the supercharged Mach 1 which has already solved this issue? If so, how could it be made available to my speed shop?
4) Will Diablosport offer a data logging feature/function to the U7140? If so, when?

Thank You!

[stangman_2]

Sorry...I'm using a U7146.

My bad!

[ChrisDiabloSport]

The Predator doesn't calculate load, it reads it directly from the PCM.

The difference in the Predator and the AutoTap is most likely in the sample rate, the Predator will sample more times per second than the AutoTap.

The issue you are experiencing is fairly common, your tuner just needs to go in and modify the idle airflow functions and this will fix your stalling issue.

The Predator already does data logging, when you go under Real Time Data and select the group you want to monitor, it will ask you if you want to log, select yes and you will be able to play back the log directly on the Predator or download it to your PC for playback using the DAT viewer in the following link. http://www.diablosport.com/index.php?mo ... lay&pid=14

[stangman_2]

Thanks Chris. I'll try the data logging function one more time. When I tried it last it didn't work which prompted my call (and purchase of AutoTap).

[ChrisDiabloSport]

If for some reason you have an issue while trying to log try doing a Live Table Reset.

[stangman_2]

Chris,

I did as you suggested...installed CMT_DAT.exe program, reset live parameters on the Predator, data logged on my ride into work this morning, and got as far as uploading the file from Predator to my PC, however an error message "Aborting Communication" came up. Nothing...no packets or anything were transferred. I rebooted PC and Predator power, double checked the serial cable connections and tried again, but with the same result. I made sure to follow the instructions I downloaded from your website. This is what happened when I tried to originally data log about 1 year ago and when I called into Tech support at Diablosport was told no data logging uploading option existed for the U7146. I know the Predator communicates with my PC, as my speed shop has sent me several tunes trying to solve the low load/stalling problem and it communicated just fine in this mode. In addition I've actually changed idle rpm a couple of times in the past and sent this tune file from Predator to PC without any problems also. I know the log file is there becasue I went into playback mode and saw everything happening on the Predator screen. Any idea what's going on?

Thanks!
Brian.

[stangman_2]

Discovered I had the wrong bit rate setting in the CMR_DAT program. When I seletced 57600 baud it started communicating with my PC. Sorry for the hassle. I'll let you know if I have any other questions.

[mikel]

Glad to hear you got it going.

Thanks

[stangman_2]

Hey guys, data logging/playback works great - really glad I was able to get this set-up. One parameter I was measuring was MAF voltage. As I was logging the display showed it as Volts, howver in playback mode it shows as A/D "hits" intead of voltage. I was trying to create an MAF air flow (or even rpm) to voltage transfer curve. Is there any way to log MAF in air volume or velocity, and how can I convert from A/D hits to voltage?

Thanks again for all the great support!

Brian