TRM tune, rev limit went down to 6k

[sludge1300]

Thanks for the pointers. Track day next weekend, I'll drop back in after with an update on if it still works.

[FredK]

Oh. Sweet.

[sludge1300]

Fixed it. I checked continuity on wires leading out from dme pin 42. Turns out the wire was blue/yellow. wtf? Anyway, made sense cuz it was included in the Treehouse wiring harness, and unused behind the dash (was formerly running into plug C1, C2 or C3, not sure which, i cut them off) . Anyway, I hooked it up just as I describe above. Red line is back to 7k, and the dash speedo still works.

Hopefully not a fluke....

[sludge1300]

[sludge1300]

There's no harm in trying, for sure. If it works, great. If not, it's probably best to borrow someone's scope and check the output at the cluster. This sounds like a race car, so maybe you've already deleted the cruise control. But the cruise control would be a good place to intercept the VSS, with the cluster in place.

I think that you might need to install a small VR to square wave circuit, like http://www.diyautotune.com/catalog/z...ers-p-378.html

Yep, I'll just give it a try. I have no cluster, no cruise, no nothing. Here's my circuit:

[FredK]

There's no harm in trying, for sure. If it works, great. If not, it's probably best to borrow someone's scope and check the output at the cluster. This sounds like a race car, so maybe you've already deleted the cruise control. But the cruise control would be a good place to intercept the VSS, with the cluster in place.

I think that you might need to install a small VR to square wave circuit, like http://www.diyautotune.com/catalog/z...ers-p-378.html

[sludge1300]

Sorry I confused you earlier. The sensor in the diff is the road speed signal. The VSS is a signal that originates from the e30 cluster.

If you had a handheld scope, you could easily find out what type of signal the DME is looking for. It is likely that it is looking for a square wave signal. The signal from the diff should be a sine wave. You will have to find alternate means of conditioning the sine wave so that it appears to be a digital signal.

Ahh, ok. Interesting. The reason I'm running a pull up resistor is for that exact reason. The dash requires a square wave voltage signal. The question is, without a scope....how could I know what the dme needs?

I suppose i could just try it out. Split the wire after the resistor. The question is, what voltage does the DME want? I'm pretty sure I'm running 12v from the sensor into the dash now.

[FredK]

Sorry I confused you earlier. The sensor in the diff is the road speed signal. The VSS is a signal that originates from the e30 cluster.

If you had a handheld scope, you could easily find out what type of signal the DME is looking for. It is likely that it is looking for a square wave signal. The signal from the diff should be a sine wave. You will have to find alternate means of conditioning the sine wave so that it appears to be a digital signal.

[sludge1300]

Ok, well I'm going to check this out tonight, but I can say confidently that I have the VSS running into my dash with a pull up resistor.

If i:

-splice the VSS wire coming from diff, into a Y
-connect one half into the dash, through resistor,
- connect the other half to the black/white (?) wire going into C101
do you think the dme will get the type of signal it needs?..or is the resistor going to screw it up?

Sorry, I can never remember too much electrical stuff at once :)

[e30rapidic]

VSS applies in all gears. I know firsthand!

[sludge1300]

I think the soft cut is only in 1st and 2nd gear? Not sure though.

kinda losing me here. I can tell you that my issue is for all gears, but i guess without the vss the DME wouldn't be able to tell that anyway.

[FredK]

I think the soft cut is only in 1st and 2nd gear? Not sure though.

[sludge1300]

So what you're saying is that the tune requires a vehicle speed signal...and it took a while for it to figure out that it's not there?

I guess i can believe that, I only tested the high rev limit in the first 10 minutes after installing the tune.

I have the vss wire running straight into the dash, can't think of why I couldn't just splice that and connect it up to the harness going to the DME

[FredK]

Yes, sorry, I meant VSS. Vehicle speed signal. That originates from the instrument cluster to the DME.

[328ijunkie]

Vss.