itb size

For the first time I want to do my own itb (I've helped a few honda buddies put some bolt ons on). So I found some cheep ones, and they are 43mm... is this good? and if so, then let's talk design, how long should the runners be before, and after the throttle?

Another option is these used BMW itb setups, are they any good? I can't find any dimensions on them

aussyvolvo said:

For the first time I want to do my own itb (I've helped a few honda buddies put some bolt ons on). So I found some cheep ones, and they are 43mm... is this good? and if so, then let's talk design, how long should the runners be before, and after the throttle?

Another option is these used BMW itb setups, are they any good? I can't find any dimensions on them

Click to expand...

Probably depends on what sorta power you're ultimately looking for..Not merely peak power but what sort?
In rally practice, cars that have to pull good from relatively low rpm it seems to follow carbie sizing..which means 48 throttle for 2,0 to 2,4 engines..45 for 1600s. Pure roadrace one step bigger...

John V said:

Probably depends on what sorta power you're ultimately looking for..Not merely peak power but what sort?
In rally practice, cars that have to pull good from relatively low rpm it seems to follow carbie sizing..which means 48 throttle for 2,0 to 2,4 engines..45 for 1600s. Pure roadrace one step bigger...

Click to expand...

megasquirt, with fuel injected itb, sorry. This is for drift, and only a little bit for paddy bashing. So primarily higher rpm ranges.

I used Toyota 4age 20v itbs on my brother's 245, they are 44mm I believe. Runners are 6.75" long, so with the ITB body and the runner in the head total intake tract length was around 9" total. Running techno toy trumpets, the length I forget now, but I am very close to hitting the hood so can not make them any longer. With a custom 4-2-1 header I made, k cam, and a stock b230f on megasquirt with the ITBs it made 125whp at 5800rpm and 134ftlbs at 5500. Find a set from a 4cyl, wil be much easier. Get good at syncing them, if this is your first venture into megasquirt I wouldn't suggest a diy ITB tune as your first go. What happened to your plans for a supercharger?

upon closer inspection, there's huge gouges in the housing of the sc. I've also always wanted an itb setup, so this is an interim setup. The SC will happen, but later. I also want to have some fun, instead of immediately blowing up the trans. I hear that the 360 5 speed is meant to be stronger, but I can't imagine it'd be that much stronger.