any ideas why the rpms drop and rise in the log data?

 

Tirespin, intermittant ignition, bumps in the road (tires slip then catch), other wiring problem. . .

RBob.

 

I have log data from 4 totally different cars. They all do the same thing. I was thinking it was trace detonation or related to fueling. Maybe the dist gear is kind of rocking? It consistant in every gear. That log data above is from my friends car w/ t-56. All the cars have different engines and stuff. I honestly dont think it was tirespin, etc. The log data shows the timing flatlined(just how I like it). But could the timing actually be fluctuating? The cars run great but that little thing has botherd me.The rpm16 line is smoother but does the same thing. Thanks!

 

If it's common to all the cars you test, it's in the testing procedure, or eqipment.

It's only in 3 + 4th gear so it looks to be load sensitive.

I'd look at the VE and timing tables in that region, if you can rule out the testing. You might be working a flawed logic in your timing, vs peak torque HP levels. ie working on what you like rather then what the engine is telling you.

 

That's the kicker. Is the engine telling me something or is this a common occurance that just needs to be ignored? I'll look into the timing and ve tables. I can rule out testing procedure because it just a simple wot run, in the same location and under similar conditions. The equipment....well if you mean diag software,pc and cable then I can say the pc and cable is ok. The software...I don't know,maybe has to do with software timing to the aldl stream?

If you said that trace detonation could cause that to happen then maybe. In that case I would back off timing before tq peak,right?


Thanks for the help! I still have alot to learn. The deeper I go, the less I know......

 

What vehicles are these? I don't know of many in the 3rd gen family that have an RPM/16 term.

Rbob.

 

all 730 ecms. I didn't "just" dismiss what you said earlier. That stuff would vary by car.know what I mean?

 

 

Not sure what kind of help I can provide. I also wonder about the data. Look at the middle of 3rd gear, the RPM term shows a distinct drop and recovery. At that same point the RPM-16 term does nothing.

About a third of the way in 4th gear the RPM term smoothly rises drops down then back up to the normal curve. At that same point the RPM-16 term shows something different.

The speed term (MPH) shows no change at all during those two points. It does show the 1-2 & 2-3 tire spin though.

Look at the RPM & RPM-16 at the 3-4 shift. They do not follow each other. Looking at that 3-4 shift and the RPM-16 term I would say that the driver never lifted for the shift. The RPM-16 value spiked a little. Whereas the RPM term does not show that.

It would be interesting to find out what DataMaster is doing to produce the two RPM terms as shown on the graph.

RBob.

 

I can email you the log, if you like. and/or I can post the same data on my car in this thread.That car was a manual. I could have graphed the tps but I know he lifts for gear changes.

The rpm/16 is acurate within 50rpms and varies from the regular rpm 25-150rpms, from what I understand. Only the beta version of datamaster has rpm/16...

Does your car have the same thing happen to the rpms(in log data?). If it's common on all the ecms then I would bet mechanical issue or something with the ignition....

 

Does anyone have a datamaster log file I can look at?