e36 TPS Question

[bravo 35]

Does the e36 TPS have a constantly variable voltage output??

E30 only has 2 or 3 positions I understand???

Anyone able to dish the dirt on this?

I want to run two TPSs. The stock e30 one in the stock location, and the e36 one piggy backed (yet to work out how) for another purpose.

Thanks.

[Guest FrantiC]

Yes it is variable.

The e30 one is either, Closed, just open or Wide open.

m50 one is variable depending on position. I don't know how exactly it works, I just have one I am using for megasquirt as it requires a variable TPS.

[BM WORLD 1283]

also e34 e32 ones withround plug with 5 or 6 pins , has fully open , fully closed switch plus varible out put , will fit in the same place as m20 and m50 type

[bravo 35]

OK, that's a good start.

Maybe I'll explain more as someone may be able to save me some of the hard work.

I want a relay to activate the supercharger clutch at various throttle positions. This would allow the SC clutch to disengage during a cruise scenario with only partially open throttle, but engage when the throttle is opened further for acceleration. I also want to work out how to piggyback on the engine speed sensor so I can switch the SC off at low revs (say under 2 grand) but come on over that.

That would allow there to be no boost in low-rev situations, and will solve the problem during the engine braking scenario with only a TPS switched clutch. If the SC switches off in this situation (closed throttle), thats great, but potentially it would then engage the clutch again as soon as the power is put back on upon exiting the corner, with potentially quite a few revs on = bad.

Here's a rough idea of how I'd like to see it operate - actual rev thresholds may need work - advice appreciated.

Revs <2000rpm

Throttle closed = clutch disengaged

Throttle cruise = clutch disengaged

WOT = clutch disengaged???????????

2000rpm<Revs<3000rpm

Throttle closed = clutch disengaged

Throttle cruise = clutch disengaged

WOT = clutch engaged

Revs>3000rpm

Clutch engaged

[bravo 35]

Brent - will e30 factory ecu recognise output??? ie could I use 1 TPS and have the e30 ecu work OK, and just take my feed off for the SC relay????

[Mike 1]

You want the one Brent is talking about. It still retains the normal function of the e30 TPS so will work fine with your factory ecu. But, it also has the variable output of the e36. It will have to be custom wired in and probably some tricky circutry to work but could be done. I'd run the super charger relay completely seperate from the factory ecu, the dual TPS should allow you to do this.

[bravo 35]

Thats the plan. I've been told I can get an adjustable voltage sensor that can take two variable inputs and provide a switchable output signal/voltage (or two outputs maybe?). So it would take inputs from TPS and hopefully revs, and then output to a relay depending on how it is setup. Off the shelf items apparently, so not too difficult or expensive once it's worked out.

So you think I'd need to run 2x TPS sensors to achieve this??? Or does the TPS you talk of have two outputs?

[CamB 48]

You could do it the slightly rangi-er way:

- cheapest rpm switch you can find (cheap shift light?)

- microswitch on the throttle pedal

Link them up in series to trigger a relay?

Hmmm. Science project!

http://jaycar.co.nz/productView.asp?ID=KC5...mp;form=KEYWORD

http://jaycar.co.nz/productView.asp?ID=SM1...mp;form=KEYWORD

(edit) This is cooler - voltage selectable switch, although it would mean you need to get a proper TPS. I don't see why the TPS couldn't be used by both ECU and for this purpose (as long as the E34 one suits the E30's ECU).

http://jaycar.co.nz/productView.asp?ID=KC5...mp;form=KEYWORD

Edited May 26, 2009 by CamB

[bravo 35]

^^^^That's the who-dickey I was thinking of.

Will go the TPS route. Just have to work out what sort of output I can get from an engine speed sensor.

Still not sure if I can take the output from 1 TPS and split it without affecting what the ECU sees.

[Mike 1]

Or does the TPS you talk of have two outputs?

This one^.

I quite like what Cam suggested, though the downside is that when you are above 3000rpm and modulating the throttle your S/C clutch will be engaging and dis-engaging very quickly and at high speeds and could cause significant wear on the clutch? That frequency switch could take care of that though with the hysteresis function?

Or, you could do it another way, have 2 rpm sensors:

one is set at 2000rpm and is in series with the throttle sensor (be it microswitch or voltage). This means that both conditions have to be met to engage the clutch.

other rpm sensor is set at 3000rpm and will trigger a separate relay that doesn't depend on the throttle position, ie it bypasses this switch.

The electronic for using the TPS will be quite simple, probably a transistor and a few resistors, pretty sure its only a variable resistor itself. As soon as the current is high enough the transistor will switch and activate the relay. Google should be able to help you out here?

How did toyota do it?

Still not sure if I can take the output from 1 TPS and split it without affecting what the ECU sees.

See top of this post, dual output so wont interfere with factory ecu.

Edited May 26, 2009 by Mike

[bravo 35]

Thanks Ron, Mike, Cam. All valuable input.

Ron I agree totally with your reasoning, but will have to do some more research before I fully understand the methodology. Sorry about the variable voltage semantics.....

Will have to look into the TPS vs RPM differential more closely as basically what it would be reacting to is engine load, although you would still want a max RPM where the SC is always engaged so if you floor it during a high-speed cruise scenario, it doesn't kick in at the high revs - it would have already engaged at safe RPM.

I don't think I want to get into a software-activated solution for now. Want to keep it under budget and simple.

So the solution will have to be something already discussed here or a derivative of. My main goal is to reduce the motor and SC loads. The SC currently runs all the time, except with the ignition Off, Acc, or cranking. My information is that this is a great way to overheat the SC and eventually kill it, and my loss of boost at higher revs could point to heat being an issue.

So the game plan is for now to turn the SC off at idle. I could do this with just a TPS feed, but that would also cut it out on engine braking which as earlier explained isn't good if I then reapply the gas and it re-engages at high RPM.

So, if I can devise the system to work so it switches off at say closed throttle provided the RPM < say 1000rpm criteria is fulfilled, then I can use that to get the electronics side working under the current tune. Then head back to the dyno, change the RPM and TPS presets, and then retune.

[westy 614]

How did toyota do it?

Can you find this out??

I'd be trying to replicate this??

[Andrew 30]

I have a couple you can have Bravo. I was using them with my Link. Probably same as the Toyota ones - 0 - 5V TPS.

[bravo 35]

Thanks Andrew.

Good info Ron.

Still researching...

[keen 6]

Can you keep us posted on this I'm very interested in your project and I'm sure It would be very general to most supercharging problems. Was the S/C a toyota sc 12 or 14?

[bravo 35]

Yeah no worries. SC14. It's fine for the low boost I'm running, but I've already decided that long term I need a bigger one

[keen 6]

Just a further question are you lifting the boost? I understand that if it stays under 8 pounds you don't need to intercool it. but if you are around the 10 to 12 you do, but is that about as far as you should go to keep the reliability and not have too much of a monster on your hands. could you post up some pictures of the fitting that you have or are going to do? Pleeeeease. Ken

[bravo 35]

It's intercooled and plan to either leave the boost as is or perhaps lift it a couple of PSI, but I think I'm close to max on this SC.

Build thread is here.

[Guest FrantiC]

Just thought you would like to know, There is a m20 variable TPS found on 89+ auto models with the Sport Selector special auto ZF 4HP22 EH (Must be EH). Or on E32/E34 M20 auto's with EH trans. It has a different circlular 6pin connector though, but is a direct bolt up to m20 throttle body and is a variable TPS not the WOT switch.

Couldn't be bothered trying to mount my m50 one to the TB and through research found there is already an m20 one so why not.. Thought this info could be of possible interest.

[bravo 35]

Thanks man.