kayakerx

So I'm trying to mix old and new. I've installed an AIM MXG 1.2 dash in my 944 race car. Still setting up sensors, etc., but the main issue I'm having is with the RPM signal. With my old Traqmate, I could just hardwire a line from the negative post of the coil to get the RPM signal. For the MXG, I used this forum and read that won't work. It supposedly needs a square wave signal (per the post I read), so I used a green wire with a black strip off of a secondary plug off the DME. After tapping this, I got a signal so I was happy, but actually driving I realized it wasn't correct. It's hard to explain, but essentially it redlines twice. It gains quickly in the first half of the rev band, then resets to what I assume is the true RPM in the second half of the rev band. I have a video of a simple engine rev here:


My next step was to just hardwire the coil to the MXG. This gave the exact same result, so I'm assuming whatever wire I tapped is just this signal. Looking at a plug diagram online, my next step is to find the wire from pin 21 on the DME plug. Any other advice from the experts here? Do I maybe just need the RPM filter add-on that AIM sells? Any advice would be appreciated!!

ProCoach

That ain’t right. The car is not that smart and the dash isn’t either. I’d send it in to get checked. If the Traqmate worked, the AiM should with the same connection.

kayakerx

Just an update, everything is fine. I was pulling the correct RPM signal (which was just coming off of the coil), but the dash was essentially doubling the value. It's a feature of the dash that if the signal gets to the top of the scale configured on the display, it will half the value and reset the screen. I should have realized this because after the display reset, the value was correct. The fix is just using a "/2" factor on the signal.

The AiM reps said that they see it all the time with karts, but this is the first time they've seen it in a car. I think I'm just one of the first to use the MXG 1.2 in this old of a car. Anyway, simple fix for anyone having the same issue.

jwasilko

Thanks for sharing the cause and fix!

ProCoach

Odd “feature” for sure.

I think the reason why many of the folks here who have experience with the new (and old) AiM dashes in older cars (and there are many) missed this is that in the INITIAL setup for reading correct RPM, the procedure IS to set that multiplier FIRST to the appropriate cylinder count. It’s all over the documentation.

4 cylinder= /2
6 cylinder= /3
8 cylinder= /4
10 cylinder= /5
12 cylinder= /6

What threw us all off was this changing reading at the limit. Glad you figured out the proper setup.

Matt Romanowski

It's also the rate at which the limit is approached. Robinson and Cameron will probably fight over who figured it out, but Bryc was holding the phone!

FastCarSlo

Glad you figured this out - we have a 944 with an MXG as well and went through the same hassle getting our RPM working. Sorry I didn’t see this sooner and chime in, I could have saved you some grief!

reach out if you have any other q’s, we’ve been running it for a year now at 3 lemons races and some PCA SDR events. We have oil temp, water temp, fuel, oil pressure, TPMS (thanks Matt!) working and pipe out to a smartycam and and Autosport Labs podium connect.

would love to compare notes on fuel level sender as I’m not convinced we have our mapping right

pwengland

Haven’t got my car with me at the moment, but just wanted to check whether the MXG (7inch) fitted nicely in the cavity of the oval dash. Wasn’t sure whether it would be too high to fit.

Just wanted to order one so thought better to ask someone who has done it !

Matt Romanowski

Use this link and you can print out a template to see how it fits in your car https://aim-sportline.com/download/d...n_template.pdf