engine/drive shaft RPM data acquisition

[lindertw]

anyone making use of data acquisition at the track to further tune their car?

- autometer ultimate memory tach
- rpm performance data logger (basic)
- racepak sportsman
- etc...

the following is an excerpt from a manual trans racing forum I've been watching:

[FONT=Verdana, Arial, Helvetica]example of the rpm data from an Ultimate tach

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[FONT=Verdana, Arial, Helvetica]Blue is motor RPM, Green is driveshaft RPM, and the other is some type of weird composite of both RPM's that I have yet to understand (and usually turn off).

Note that the tach records for 2 seconds before the launch and shows the 2 step holding RPM (4200.) When launched the car initially hooks, bogs, hooks and bogs again before finally accelerating to the top of first gear. Video showed that both wheels hit hard and wheel hopped. You can see the shift RPM's and the effect on the driveshaft speed, plus how far the motor drops off during shifts. The car is in first gear until after the 60' mark. Once the car is in 4th gear the engine and driveshaft RPM's are the same. You can also see that this run was aborted before the traps. There is more info to be gained by studying this graph, but that is about as much as this novice has ID'ed while studying it.

Info markers shown on the graph (ie 60', 330', etc) comes from manually entering data into the graphs database from the timeslip.

[/FONT][FONT=Verdana, Arial, Helvetica]At first blush the cost seems prohibitive, but most would think nothing of spending $500+ on a 1pc drive shaft - and I think the data above would be more helpful in the long run. I'm interested in hearing any experiences and pros/cons for any particular system.

thanks, and Happy New Year!
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[555]

Very Interrrrreeeeeesting.

 

[lindertw]

so it turns out much of this might be accomplished with SCT livelink software

I recently had my car tuned at JPC after installing steeda CMDP's. Before I headed up for the dyno tune, I had to update the firmware on my SCT X3, and also downloaded the latest version of livelink software.

Tonight I decided to tinker with datalogging, and discovered the following items that I think I'll log to help me decode what the car is doing at the track:

- accel pedal position 1
- actual axle torque
- engine load
- engine oil temp
- intake air temp
- throttle mode
- pedal position
- spark
- clutch engaged
- clutch pedal position
- transmission vehicle speed
- output shaft speed
- rpm
- vehicle acceleration rate
- vehicle speed
- distance traveled since startup (presumably datalog start, we'll see)

Output shaft speed = drive shaft speed, and plotting it against engine rpm is what I'm after - without having to step into one of the data acquisition systems listed above! Here's a sample from a quick drive around the block

pink = clutch
thick light blue = engine rpm
thin purple = drive shaft rpm
thin green(ish) = vehicle speed

I did this trial from a roll, but I'm excited to see the results from the track. I should be able to monitor:

- engine rpm drop at launch
- engine rpm drop between shifts
- tire slip (as a function of vehicle speed / drive shaft rpm?)

I'm stoked to try this out! I won't be getting to the track until the fall, but I have time to check for other PID's to log. Being able to manipulate the graph in SCT is limited, but I can save the data off as a .csv and plot it in excel and make it easier to read.

 

[lindertw]

I chatted with Kelly (BMR) about data acquisition briefly last night:

We log all of that for our race cars (engine rpm, ds rpm, clutch position, throttle position). The only issue is its very difficult. What you may think will happen based off of those factors, sometimes doesn't. For example, sometimes spinning more gets you better ET and worse sixty.....and sometimes spinning more gets you better sixty and worse ET, etc. Recovery rate matters more. You want wheel speed, and you want to find the fine line. The problem is, the logs won't show you an overall pattern because of all of the other variables being inconsistent.

He's absolutely right, variables will exist (weather, tires, track condition, driver skill/inconsistency, etc.), but I think many of us tend to be a 'crew of one' when we go to test and tune, and if we already have the SCT device, then the barrier to entry for data acquisition is gone (presuming you have a laptop you can take with you to the track).

At a minimum, I think it makes sense to monitor engine RPM and driveshaft RPM. Driveshaft speed is used to look at tire slippage and also to calculate a slippage ratio between the engine and the clutch or torque converter. For those of you with automatic transmissions, you can monitor the following which can help your tuner better refine things, as well as optimize your torque converter (source).

I hope to see folks tinkering with this, and posting results - maybe it can be as helpful at the AS%, IC height/length discussion thread!

 

[lindertw]

logged one run at test & tune last night...

blue = engine RPM, purple = driveshaft RPM, gold = clutch position (on/off). launch, 1-2 shift and 2-3 shift shown. 12.446 @ 108.80, with 1.675 60' (DA hovered around 2000')

[FONT=Verdana, Arial, Helvetica]time between launch and clutch in for 1-2 shift = 1.751 seconds (it looks a little skewed here because I expanded the x-axis)[/FONT]