TPS for megasquirted CIS engine ?
 

I have had happy days since the tBitz Megasquirt was installed. It has been a blessing in every way except I always seem to have this urge to continue tweaking. The laptop seems to be on the passenger seat a lot. The good thing is I feel I have an intimate knowledge of both MS and the engine, but the bad thing is I am never completely happy.

It got worse after installing EDIS ignition (also MAP/RPM based) with even more variables up in the air. The car runs better than ever but fuelling and ignition are not independent, and with only MAP sensor it is difficult to get it all optimum.

Just suspecting it may not be optimum is constantly eating away and now this project needs to be finished or I need to get another obsession.

Talking to tuners I would like to install a TPS and use a combination of TPS and MAP to have it tuned to perfection or as close as possible, on a rolling road.

Any advice on a suitable TPS for adapting to the CIS butterfly axle ?

I cant help you, but I just want to say, it sounds like you are having fun.

Any chance you have got some pics of your tbitz install.

I am putting my Carrera 3.0 back together. In the process I put a MS harness in, just in case...

Trond, Good to see you here.

What problems are you having? Just trying to make sure that the installation of a TPS will help your issues.

Many tuners are used to seeing a TPS signal but this does not always solve the problem. Is this related to acceleration enrichments? Is this related to high load or high rpm situations where MAP signals may be close to maxed out?

A TPS can be installed but it does require some fabrication. Look up Tony Bitz original threads and he has a nicely detailed thread about installing a TPS.

Jamie ! The systems (MS2 Extra and MegaJolt/EDIS) both work beautifully and last week I installed the dual pressure sensor to avoid fuelling changes at altitude, so I am enjoying the experience. The issue I may have is part load tuning of especially ignition. I spent hours with the car on a Dynapac chassis dyno (rolling road) attempting to create an ignition map but found it impossible to hold a steady manifold pressure. I´d lock the bench at specific RPM and then while trying to maintain a constant manifold pressure adjust ignition timing up/down to look for peak torque. Very difficult too manipulate the throttle pedal while playing with the tune. There were no issues tuning WOT, but part throttle was difficult.

All tuners I have talked to are used to TPS and I have not managed to find anyone to take on the job with MAP sensor only and this is the reason for wanting to install TPS. I want a tuner to set it up and for that I need TPS. Also excellent fun to expand the system and make it work

Fuelling I feel is easier with the AFR target table and the autotune function combined with manual tweaking.

As it runs now my car has excellent throttle response and good fuel economy but I feel the engine is not as free revving as it should be, compared to a friends stock CIS SC of same year and configuration.

Not sure if the shaft is the same as a C3.2 TB, but if it is, an E30 BMW TPS will slide onto the shaft and just need to make an adapter to bolt to.

The 3.3 turbo throttle body has a TPS...might just bolt up and do the trick.

Most E30 BMW TPS are just an on/off switch. The exception is late models that have true position sensors. Clewett has a sensor for the 3.2 but don't know if it can be adapted or not. If the 3.2 butterfly axle is same shape as on the 3.0 CIS then I would guess it can be adapted.

But I'll make the rounds on the tbitz forum as was suggested and report my findings here

BMW's M30 engine *with automatic trans only* in the late '80's used a 5 wire TPS that has the switches and a potentiometer. It is what all the megasquirt BMW guys use.