RLTC - RPM Wiring Warning!

If you’ve got RLTC check your RPM signal! The following is likely to be more relevant to NA owners but may be relevant to TT too.

I discovered in somewhat scary circumstances this week that my RLTC hasn’t been working above about 5000 RPM. Fortunately the Supra and I survived to do some investigation.

Basically there are some RPM signals in the car which don’t appear to be strong enough to drive the RLTC over about 5000 RPM. If you look at the attached trace from the RLTC data logger you can see what happened on my car, the signal suffers from drop-outs at higher RPMs. It had me fooled, because it works fine at lower RPMs, so I didn’t notice when I first installed and tested the system. The trouble is that from the RLTC unit’s point of view the drop-outs look like that engine RPM has actually fallen and once it drops below the minimum threshold (default 2000RPM) the system does not apply any traction control!

On the NA there are a couple of signals that produce this effect and I would suggest you avoid for RLTC:

• IGT – Igniter Trigger – ECU (E9) Pin 57 - Red/White Wire
  
• IGF – Igniter Feedback – ECU (E9) Pin 58 - Red/Yellow Wire
  

These are often used to pick up RPM on the NA, as there is no dedicated RPM output on the NA ECU, unlike the TT ECU. I’ve not tested to see if this effect is evident on the TT, but the TT is similar with six Igniter Triggers IG1 to IG6 and some people use the IGF signal if there are too many things already loaded on the dedicated RPM output pin.

On the NA the wire that is used to drive the TACHO seems to work fine, this comes straight from the Igniter and not the ECU. It can be found at the back of the Rev counter amongst other places. If you have a NA I would suggest you use this signal!

• TACHO – (A) Pin 13 – Black/White (from EXT – Ignitor External Output – Igniter Pin 4 – Black/White).
  

If you want to check your car is ok, you can either plug a laptop in and use the RaceLogic software, or watch the little green diagnostic light with the slip control knob set to Off. Either way Rev the car hard and check the signal doesn’t disappear!!

At this time of year you really don't want your RLTC to fail...

Thanks for that!

I'll check mine tomorrow.

I'm not 100% sure the RLTC is working properly, I've been getting noticeable wheelspin at higher speeds in the wet. Definately worth checking out.

That's how I noticed mine wasn't working... except I was on a long sweeping bend! Hope you get yours sorted.