ITB's

[kowalski]

Since FI people are generally the most knowledgeable on these boards here we go.

Now, performing my calculations based on Jenvy FAQ's, and going by the fact that i will be reaching anywhere from 57.5 hp per cylinder to 62.5hp per cylinder give or take. This means that i should be using a throttle body between 40-42mm. This seems really small to me and makes me think i'm doing something wrong here, and i definitely don't want to get TB's that are too small. for these calculations, i'm supposed to be using a 150mm distance between the top of the valve, and the butterfly correct? assuming so, this works good because i need a spacer to addapt the throttle bodies to my head anyways. And to top this all off, the engine is going to be a street driven engine, but capable of 7,700 rpm so i should be looking for 25mm trumpets to give me an overall length of 200mm correct? or should i aim for smaller trumpets for a lower rpm power band?
kowalski is online now Edit/Delete Message

[Jand3rson]

For FI info, I would actually go search over on E30Tech. Those guys are the boost junkies.

[kowalski]

well its not FI, its going to be naturally aspirated. Since this is the only section that deals with performance i figured it should end up here...

[PiercedE30]

What motor are you going to be working with?

[matt]

Since FI people are generally the most knowledgeable on these boards here we go.

Now, performing my calculations based on Jenvy FAQ's, and going by the fact that i will be reaching anywhere from 57.5 hp per cylinder to 62.5hp per cylinder give or take. This means that i should be using a throttle body between 40-42mm. This seems really small to me and makes me think i'm doing something wrong here, and i definitely don't want to get TB's that are too small. for these calculations, i'm supposed to be using a 150mm distance between the top of the valve, and the butterfly correct? assuming so, this works good because i need a spacer to addapt the throttle bodies to my head anyways. And to top this all off, the engine is going to be a street driven engine, but capable of 7,700 rpm so i should be looking for 25mm trumpets to give me an overall length of 200mm correct? or should i aim for smaller trumpets for a lower rpm power band?
kowalski is online now Edit/Delete Message

A couple things... 40mm sounds pretty good. Why do you think that's small? Carbed cars making ~60hp/cyl routinely use 40 and 45mm DCOEs that choke down even smaller.

Second, longer runners move the powerband down, shorter runners move it up.

Third, what motor are you doing this to? Street driven motors with ITBs tend to... suck.

[Mr Deagle]

Third, what motor are you doing this to? Street driven motors with ITBs tend to... suck.

all of the ///M cars have them (except certain e36's)

I don't see what you are getting at......

Its all about your engine management, and idle control.....

[kowalski]

if you can tune it properly and design it properly there is no problems running ITB's.

they're for an m42 engine. I think they're small because the dbilas kit supplies 50mm throttle bodies. but then again they're kit isn't very good, so who knows.

[Mr Deagle]

why dont you get a set of s14 throttle bodies, and make an adapter?


The evo3 throttles are 48mm, and they are capable of over 300 hp n/a, and standard s14 throttles are 46mm

[kowalski]

the intake port spacing is wrong, s14 itb's are fairly expensive as well. I've got my eye on a set of dbilas ones that are 50mm. I know the euro s50 itb's are the correct port spacing, and i may end up usiing those if things don't pull through with the dbilas ones, or i'll go with the hayabusa ones... but at the moment it looks like i can pick which ones i want, and i don't want to get over sized throttle bodies, nor do i want to get undersized throttle bodies...