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The mkiv Supra Owners Club

Suppressing the stock TRC function


Paul Booth
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Ignoring the braking action on some model's TRC. That is simply a plumbing job to remove.

 

I bought myself the TRC removal kit, as did others, and noted the grief after they'd been fitted to cars with auto boxes.

 

Now while I acknowledge the main issues seem to be around the self- test function on the TRC ECU and the sub-throttle position sensing, and that a potential fix could be achieved by mating the actuator and the sub-throttle position sense mechanicals; it seems to me that it may be a great deal of work for not a huge return.

 

Assuming the actuator and position sense were mated, with the manual box that's the end of the story; with the auto box there's the not fully understood issues around torque control during up-changes.

 

The TRC ECU enable/disable switch is a momentary SPST which applies a ground to the appropriate pin on the TRC ECU. It's not buffered or driven externally so it's protecting itself internally.

 

You may have noted that if you press the 'slip' button, turn on the ignition the TRC is made inactive, as shown by the warning light. I've held the button for en extanded period and nothing changes.

It might be possible to argue that you could simply solder the pin to ground and the TRC function would alwas be inactive, however, I wouldn't want to say you aren't stressing a junction somewhere internally and that it might pop one day leaving you with a TRC you *can't* switch off.

 

Better to have an earth pulse applied to the pin for 5 seconds after ignition on and then removed. You'd then have the choice of removing the button from your dashboard and removing the warning bulb but you'd still retain the torque control during up-changes.

 

I'm not sure at this time exactly what influence the lateral movement sensor has on slip control but it's just another step along the road.

 

This could be done with a simple Schmidt function, basically a tranny (Darlington?) a capacitor and resistor, but it would be nice if it was on a PCB and potted........ Pete :)

 

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Better to have an earth pulse applied to the pin for 5 seconds after ignition on and then removed.

***************

 

I'd also considered such a simple solution. Not wanting to modify anything to do with the normal operation of theTRC but saving my memory and turning it off for me as I've got the RL TRC.

But again never quite got around to doing it.

 

 

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This could be done with a simple Schmidt function, basically a tranny (Darlington?) a capacitor and resistor, but it would be nice if it was on a PCB and potted........ Pete  

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Depends on the take up of the idea. Time is precious to us all as you know.

You might get away with Veroboard design as it's only a few components. Probably use a 1" cube potting box. To give you an idea of size.

 

I've got loads of ideas similar to you Paul but not all of them would sell in the hundreds so that rather limits what I spend my time on.

 

Maybe I should do a Justin and pack up my normal job? Err! Not just yet. Good luck Justin by the way.

 

 

What does the HKS TRC kit include then? and do they do one specifically for the Auto?

 

Pete

 

 

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I believe I have cured the problems I was having with mine, I just have to disable the warning light now.

 

There is a rotary contact on the cylinder side assembly that is held by a spring in the "throttle butterfly closed" position when the Trac gubbins are removed.

 

You need to remove this item, snip the spring, and superglue the rotary contact in the opposite position so the ECU thinks it is open.

 

I fitted, removed and re-fitted my HKS kit to check this solution, with this in place the autobox appears unaffected and the 2nd turbo comes online at the correct revs.

 

Regards,  

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Paul......

 

Let me have your address and I'll send you a timer box. Buy me a couple of large ones when we see each other at some meet or other.

 

Yours,

J  

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I have got the TC removal kit, and was eager to fit it.

 

However reading all the related posts over the last few weeks has made me wonder if it is worth the hassle with the auto box.

 

Has any one any idea if just removing the butterfly but leaving the connecting rod in place would give a good end result, a lot cheaper and a lot less hassle?

 

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Sorry if I'm wrong but I thought the other Phil had the solution a couple of posts ago. Apologies for having zilch knowledge on this but I've yet to fit the components.

 

Yours,

J

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Yeah I had read that!

 

Phil can you confirm that all things are functioning OK?

 

I only mentioned it, because as yet were have no idea what actual gains are to be made.

 

Have I missed something, I was surfing (on the waves) for a week, has anyone any objective idea of the impact of this removal.

 

I am willing to just to remove the butterfly and try the car for a week or so then do the Phil super glue mod(I might move upmarket and use araldite) and give a subjective comparison..

 

The only trouble with that is when we have spent time and money we anticipate a gain!

 

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Quote: from Ash on 8:49 pm on Sep. 4, 2001[br]

 

 

Paul......

 

Let me have your address and I'll send you a timer box. Buy me a couple of large ones when we see each other at some meet or other.

 

Yours,

J  

 

Ash,

 

before I 'waste' one of your timers. To reiterate: I want to connect an earth to the slip disable pin on the TRC ECU for a set period 1-5 seconds (ish) after ignition on.

 

I think I was aware that your box switches live to the fans on power activation, will it also allow earth switching, i.e., is it a relay or semiconductor switch?

 

Oh and much obliged for the offer which I'm hoping to take up.

 

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Yep, that's what I thought. I'll set the timer to activate for the timed period on power up. You can set it from between 1 second to several minutes (your choice). The outputs are relay switched, 5A max. Single pole with common, NC & NO contacts.    

 

Sounds a bit clunky but it's dead reliable and cheap.

 

RS do some neat little semiconductor ones but they cost over £30 just for the unit. Whereas I can get the whole thing built for around £25... that's potted, in a neat little box, with a mounting bracket, etc.    

 

Yours,

J

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