Throttle Body Sizing ??, For Megasquirt Options

[yarin]

I'm building a MS system and i'm trying to pick a throttle body to bolt onto the 2.0 intake plenum.

The motor is relatively stock, some head work, cam, 4-2-1 headers. I've searched and searched, what throttle body size do i want? This will be an occasional street car but built for autox / track.

It sounds like 50mm is the "right" size. Are the stock 1.7, 1.8 and 2.0 TBs all the same size? What size?

A few ppl have used a volvo TB on here. Does the stock TPS do the job? What modifications were required?

[DNHunt]

Yarin

I'm using a stock 2.0 throttle body that has been bored to 50mm from the stock 45mm. You have to make your own butterfly valve. I'm running this on a 2270 with a cam Jake provided and so far it looks OK.

You'll just have to try stuff. A couple of things to look for. If the throttle body is too big, throttle response will suffer. If it is too small (the whole intake system is too small) vacuum will increase at WOT and higher RPM's. You can see this with a viewer looking at logged runs. Mine is poshing the limits of being too small right now.

Dave

[lapuwali]

I would use a stock TB, get the MS and everything else working perfectly, and only then start futzing with things like the TB size. As Dave says, a too small TB shows up pretty easily on datalogs, so you'll know after you build if the TB is too small, and if you need to go bigger.