Variable TPS

[Nate]

i found out something very interesting yesterday. Whilest doing an engine insertation into the catmobile my noticed that the SOHC auto astina's come with a variable TPS. When you think about it that makes perfect sense because that is how the ECU knows to kick it back a cog with you give it a bootful

'So what' you say ... WELL!! the SP's (and SOHC manuals i would presume) only get a switch type - ON or OFF, so for those of us out there with an BG BP and aftermarket management (are you reading this dave??) a quick TPS change, presuming they are interchangable, and all of a sudden the ecu just became a bit more tunable

[Dogo]

my bpt has a variable TPS

Tony used to drive with it disconnected - apparently it improved response i think ?

[QuicKSilveR]

I've driven heaps without TPS on BPT and B6T. When I first put the Microtech in I had it as ON / OFF. Now I have it on Variable........but the BPT (and I assume) BP have a Variable wire on the TPS

[Nate]

as far as i can work out the BP has an on off (three pronged plug) and the variable (which comes on the BPT as you said) is a four prong plug. I remember this from when we did the MT install and it was a difference between 323mazdabators car (BPT enhanced ) and mine.

driving without a TPS probably will get a better response, but hopefully with on i will improve hwy fuel economy???

[Dogo]

bah fuel economy is for people who drive like grannies.

[Nate]

and poor apprentices like me

[Osprey06]

I find it difficult to believe the BP only has a 3 pin TPs (open, closed, somewhere in between). The early spec B6Ts ran a TPS like this, but late spec jobs run a 4pin variable resistance TPS. Still, I don't know BP/Ts very well, I just assumed if the B6T had variable, the BP's (at least twin cam jobs) would have one as well...

I ran around with my TPS unplugged for a little and noticed nothing except very off idle (nearly stalling, then compensating too high, then nearly stalling etc). I was just testing pulling codes from the ecu.

[BigBoyLemonade]

Originally Posted by Dogo

bah fuel economy is for people who drive like grannies.

Yeah the more sensors I d/c the fastest the car went on less boost! Used a hell of a lot more fuel though

[EVOlution]

I have a BG 1992 DOHC and it has a crappy switch type TPS - that is crap, I thought being a '92 model would mean decent electronics but one day I will try driving with the crappy switch TPS disconnected and see if it goes any better (or worse).
I have a serious flat spot off idle, it's pissing me off big time and I can't find anyone who can give any other advice than "replace the ECU with aftermarket....." duh easy fix but I want to REALLY fix it, solve the damn flat spot problem and know why the fk it is happening in the first place
I am buying a Familia 4WD turbo engine to drop in soon but I still want to get this engine sorted until I can get the turbo engine rebuilt and installed.

[Cosmo Dude]

A variable TPS doesn't realy tell the ECU anything it doesn't already know. If you want max power then you will activate the WOT, else the AFM will let the ECU know that you want more or less power and the O2 sensor will ensure you are using the right amount of fuel.

[ROB-80E]

Originally Posted by EVOlution

I have a serious flat spot off idle, it's pissing me off big time and I can't find anyone who can give any other advice than "replace the ECU with aftermarket....." duh easy fix but I want to REALLY fix it, solve the damn flat spot problem and know why the fk it is happening in the first place

Check your timing. Standard timing should be at 10 degrees advanced.

Unplugging your TPS will do very little...as mentioned it just tells the ECU when it's not idling...but the AFM there as the main ECU input.

[EVOlution]

Ok, have to go buy a timing light. Might have to buy a full service manual so I can really get into this car and start fixing it up completely back to brand new. Might restore the whole car then look at dropping in the turbo engine. Just picked one up that's done 29,000km genuine out of a Familia 4WD.

[jrp928]

Usuallly a on/off tps is supplemented by manifold pressure sensor to give the extra information, so i really wouldnt worry about it too much. If you did swap one in where it wasnt before, will all the pins have connecting wires? If not, waste of time. If yes, try it with pressure sensor connected and disconnected.
jp 89,91 bg, 92 mx5

[CHiMPY]

Originally Posted by EVOlution

Just picked one up that's done 29,000km genuine out of a Familia 4WD.

Where from and where is mine?

[EVOlution]

I might be able to get them again, I do some work at a private rally workshop and it was a spare that was purchased for their Familia rally sprint car. I may not even use it yet and if I do it might go up for sale it was part of a whole front cut.
Anyway, back on topic - i have checked my timing and it's a perfect 10 degrees, rock solid and dead on..... now I will go check and maybe replace the manifold pressure sensor if it has one. This is getting to be a bastard of a car - I bought a lemon maybe I'll paint it yellow, grrrr.

[ROB-80E]

You don't have one, it uses the AFM for that. So that's probably the next thing you should check.

Start replacing stuff like Feul filter and spark plugs and even leads. The leads if you buy em can be used on the BPT when you get it.

[Nate]

Originally Posted by jrp928

Usuallly a on/off tps is supplemented by manifold pressure sensor to give the extra information, so i really wouldnt worry about it too much. If you did swap one in where it wasnt before, will all the pins have connecting wires? If not, waste of time. If yes, try it with pressure sensor connected and disconnected.
jp 89,91 bg, 92 mx5

I have already have a microtech installed which reads manifold pressure instead of using the ****ty AFM, and also gives me all the wires i need to hook it up. Im not worried about power, well i am but that is not why i am looking at installing it! the only reason i was looking at it is the microtech is set up to accept a TPS and hopefully finer tuning and wiz bang functions might work a bit better with the variable TPS