throttle body options

[nickmpower]

well, if the m42's TPS is a potentimeter, and takes the input of exactly how far the TB is open, it may not work to have a larger, differnt style throttle body on there which includes ITB's??? I think this really stinks becaue i have been wanting to build some itb's oh so bad.

the other option is boring the current one out. Does anyone know if universial throttle butterfly's are avalible? then you could just have a machinist bore out the body, and buy a butterfly to fit?

what do you guys think?

[haledj]

I think someone should use 4 throttle bodies- one for each cylinder, that would be hot.  But as for the other bit, IDK:confused:

[StreetSpec_iS]

this is something that i've thought about before also.

the main way to implement it would be to have a custom plenum fabbed, then run a larger, single TB on the nose of it.

ie, something like:



anyone know anything about TPS interchangeability?

[///Motorsport]

man individual throttle bodies would be so badass. someone do it now.

[Febi Guibo]

hello? tim_s, or should I say, --the man!-- has done it:

http://www.m42club.com/forums/showthread.php?t=982

[bmwman91]

Slide-throttles.  Dooo it.

[tim_s]

well, if the m42's TPS is a potentimeter, and takes the input of exactly how far the TB is open, it may not work to have a larger, differnt style throttle body on there which includes ITB's??? I think this really stinks becaue i have been wanting to build some itb's oh so bad.

the other option is boring the current one out. Does anyone know if universial throttle butterfly's are avalible? then you could just have a machinist bore out the body, and buy a butterfly to fit?

what do you guys think?

i believe you're correct about the TPS being a problem. There's a chap over here with an e36 m42 on ITBs and he's having trouble trying to get motronic to work with his ITBs due mainly to this. I think running motronic would be a real waste without a MAF/MAP conversion and a serious remap anyway, else you just won't get the best out of throttle bodies performance-wise.

I didn't even bother trying to get my setup to run off the factory motronic. I'm running megasquirt for fuel and sparks, and as a result have a restrictionless intake (no AFM/MAF etc) and instant throttle response.

[BrandC]

I think a MAP conversion/stand alone will help an ITB setup run a lot smoother.

As far as the TPS, you just have to find out the voltage range. Find a similar TPS from another car (easier said than done), but if you seriously ask around on other forums I'm certain you can find a similar voltage potentiometer TPS.

[tim_s]

I think a MAP conversion/stand alone will help an ITB setup run a lot smoother.

As far as the TPS, you just have to find out the voltage range. Find a similar TPS from another car (easier said than done), but if you seriously ask around on other forums I'm certain you can find a similar voltage potentiometer TPS.

nah think you're missing the point!
The problem is, in simple terms, say at 50% throttle given on the TPS, on the ITBs you have way more air going into the engine than with the standard throttle body, which confuses the hell out of the motronic, even if you use a standard BMW TPS.
if you think in terms of change in manifold pressure versus change in throttle position with the standard throttle body and with 4 throttle bodies with say almost 3 times the surface area (as mine have), you realise that what's called TPSdot in MS terms (rate of change in TPS), and change in TPS value in absolute terms, doesn't correspond to the same change in manifold pressure. As a result acceleration enrichment etc gets screwed up, and from the experiences of the guy with the e36 I mentioned (I have no firsthand experience because I went MS), this theory proves true in practice.

[silverblades181]

think an alpha-n type intake could be fitted to a 4 throttle body M42?

[BrandC]

nah think you're missing the point!
The problem is, in simple terms, say at 50% throttle given on the TPS, on the ITBs you have way more air going into the engine than with the standard throttle body, which confuses the hell out of the motronic, even if you use a standard BMW TPS.
if you think in terms of change in manifold pressure versus change in throttle position with the standard throttle body and with 4 throttle bodies with say almost 3 times the surface area (as mine have), you realise that what's called TPSdot in MS terms (rate of change in TPS), and change in TPS value in absolute terms, doesn't correspond to the same change in manifold pressure. As a result acceleration enrichment etc gets screwed up, and from the experiences of the guy with the e36 I mentioned (I have no firsthand experience because I went MS), this theory proves true in practice.

Understood. Hopefully you find a solution, I'd really like to see video footage of the car in action!

[tim_s]

Understood. Hopefully you find a solution, I'd really like to see video footage of the car in action!

thanks, but i'm afraid I won't be coming up with a solution as I run megasquirt which has no probs of this nature and i can program specifically for my setup. I did this in the knowledge that i'd never get the best out of the setup with motronic!

I will make a video when i borrow something which has sound (my digi cam doesn't), the car sounds great on the ITBs and with the 2.1!

[E30own'er]

tim ... if i want my 85 318i into the same kind of manifold as urs with ITB's where should i look for throttle bodies and what size , ect , how to custom a manifold what should be the best and can i shoot it stright off the block?

[tim_s]

85 318i is an M10, no? If so, there are quite a lot of kits and inlet manifolds out there that will fit. Throttle body size is fairly complex to get right, iirc jenvey.co.uk has some good reading on this.