RLTC for smoothing auto gear changes

One of the modifications to improve intake air flow is to remove the secondary throttle butterfly. On a manual car this is a *very* worthwhile mod as the only function it's performing there is the totally useless stock traction control.

On an auto model, there seems to be some ambiguity in the functional spec and the TRC is *supposedly* used to reduce torque during *up* gear changes by momentarily closing the secondary throttle. Although this is what is stated in the 'Good Book', it has to determined whether it actually does anything useful.

However, the possibility that it *may* be removing stress from the gearbox during up changes means I have hesitated to fit the HKS secondary throttle removal kit.

I've just finished off locating the RLTC and wiring in Pete's FCD and was wondering if that's my last assault on the passenger footwell.

As it does in your dotage, my mind wandered to the 'full-throttle' clutch switch gear-change, whereby the RLTC *reduces torque during gear changes*. AHA!

If I wired the secondary throttle actuator circuit such that it asserted a signal to the clutch switch sensor input, the RLTC would rev-limit/reduce when the TRC was trying to reduce torque *only* during up changes. I could therefore remove the secondary throttle in its entirety as being guaranteed redundant.

Just one question/thought. What is the *effective* difference between closing a throttle butterfly for a fraction of a second and momentarily shutting off the injectors; bearing in mind the latter is exactly what the clutch switch does?

I can't see a major problem and if no one spots a 'gotcha' I'm gonna put it on my list.

Having fitted the HKS trac removal kit a while back and sorted out the associated gremlins I can confidently say it has made no noticeable difference to the auto gearchanges - they are as smooth as ever.

I almost wish they were a bit less smooth sometimes and a bit more dramatic for that 'warp speed' effect!

Before I tricked the electronics they were all over the place though.

Cheers,

Phil

Quote: from Phil on 6:22 pm on Oct. 14, 2001[br]Having fitted the HKS trac removal kit a while back and sorted out the associated gremlins I can confidently say it has made no noticeable difference to the auto gearchanges - they are as smooth as ever.

 

I almost wish they were a bit less smooth sometimes and a bit more dramatic for that 'warp speed' effect!

 

Before I tricked the electronics they were all over the place though.

 

Cheers,

 

Phil

But you should know by now Phil, if it's there for a reason, I like to know why and what the effects are before I start attacking it.

I've asked Pete if he's ever scoped the ECU during gear changes to see what the ECU is doing during an up change.

I'd actually like to know if the ECU *really* closes the throttle flap during up changes or whether it just thinks about it.

Having seen the gubbins that goes into it first hand, for far too long , I would be surprised if it could open or close quickly enough to do anything.

I certainly can't tell the difference.

It's Box Hill in a couple of weekends, if you are coming down Paul you can take it for a spin if you like as you will be better able to spot any difference 'back to back'.

The beauty and the curse of the MkIV is that it is very civilised for such a monstrous car!

Cheers,

Quote: from Phil on 8:53 pm on Oct. 14, 2001[br]Having seen the gubbins that goes into it first hand, for far too long , I would be surprised if it could open or close quickly enough to do anything.

 

I certainly can't tell the difference.

 

It's Box Hill in a couple of weekends, if you are coming down Paul you can take it for a spin if you like as you will be better able to spot any difference 'back to back'.

 

The beauty and the curse of the MkIV is that it is very civilised for such a monstrous car!

 

Cheers,

Given the speed of the up-change, I just can't see a throttle flap closing cause a fast enough response and it's probably coupled with retarding the timing and shutting down the injectors too. Ergo, if it continues to do everything else, it probably doesn't really need the butterfly.

Pete Betts expressed the opinion that the Supra has a gear selector rather than a belt and clutch arrangement and why it's able to handle so much grunt. I was a bit skeptical about that until I grated the gears this morning. I'd been refitting the dash and had the selector in neutral. I started the engine and moved the selector towards reverse; it grated. Made me think about Pete's idea more seriously.

That being the case, any errors changing gears would be very audible and I'm therefore probably going to swap out the butterfly when I get chance this week.

You can start yours with the selector not in Park?

I thought that couldn't be done??

Quote: from Phil on 9:37 pm on Oct. 14, 2001[br]You can start yours with the selector not in Park?

 

I thought that couldn't be done??

 

Neutral.

Thought it was my imagination at first but I've done it a few times now.

I'm not saying it's supposed to or that I didn't confuse the poor thing, just that it does. Maybe hence the grating noise when trying to put it in gear.