12 replies to this topic

[Duncan]

I'm posting this to see if anyone else has run into the same thing.

 

I have a 99 with the AIM MXL dash.  I've tapped into the stock TPS wire off the ECU for the data system, however there's quite a lot of noise in the signal.  Looking at an OBDII scanner, the ECU doesn't seem the same noise, or it damps it somehow.  

Here's a picture from RaceStudio.  

 

 

Any ideas?

[Glenn Davis]

One thing I have heard is to place a 1k-Ohm resistor in line with the measurement.  Also, have you tried any filtering on the signal?

[Duncan]

One thing I have heard is to place a 1k-Ohm resistor in line with the measurement.  Also, have you tried any filtering on the signal?

 

I forgot to mention I do have a resister inline.  1K - Ohm.  Without it I would get an occasional CEL.

 

Duncan

[Danny Steyn]

Does AIM provide any filtering to dampen out this noise?

[Duncan]

Does AIM provide any filtering to dampen out this noise?

 

They do.  I'll try a math channel tonight, running the TPS through the low pass filter and see what happens. 

[Danny Steyn]

Duncan - I would bet that this would resolve what you are seeing. In Traqmate the low pass filter takes care of most of the erratic signal behavior on most of the various inputs we record.

[Duncan]

A little better with some filtering.  Certainly useable.

 

[Danny Steyn]

Is this with a low filter factor? I would have expected a flatter throttle trace with the foot pegged to the floor.

[Duncan]

I need to do some more playing around with it.  This is using the 'filter' option in the normal channel mode, setting it to 10.  There's an option in the math channel's for a low_pass function, however there's no documentation on how it works and I can't get it to behave the way I think it should.

 

Just curious, but what sampling rate do you have your stock TPS set to?

 

thanks,

Duncan

Is this with a low filter factor? I would have expected a flatter throttle trace with the foot pegged to the floor.

[Danny Steyn]

Not sure what the sampling rate on the TPS is but even at zero filtering, when at WOT I have a completely flat  line at 100% in my Traqmate throttle trace graph. Now for my AF ratio and FP ratio signals I do need to set the filtering at LOW to get rid of the fluctuations 

[Danny Steyn]

Actually Duncan, I take that back. My Traqmate throttle trace actually does have slight variations off the 100% flat line with no filtering - strange - never noticed it before until I checked again today!!!!!

[Duncan]

It's been so long since I hooked this up that I had a thought last night.  I wonder if I tapped the TPS signal ground in the data logger to chassis ground, rather than the ECU sensor ground.  Might explain the noise I'm picking up. 

 

I sent a data file to Roger Caddell from AIM, who generously agreed to take a look at it.

 

thanks,

Duncan

Actually Duncan, I take that back. My Traqmate throttle trace actually does have slight variations off the 100% flat line with no filtering - strange - never noticed it before until I checked again today!!!!!

[tLinder]

Maybe this thread has some helpful info.

http://mazdaracers.c...hrottle-sensor/

 

(Adding TPS to my AIM MXL is on my "to do list", so let me know how it goes )