as im lookin at this now im thinkin i can just port the mi to suit bigger butterflys does any1 agree? and lookin at my mi tb its not the same as the 1 on the left. do both of those units butterflys open at the same time as each other or does 1 side open first then the other ?

Couldn't you get past the TB issue by running more boost?

yes indeed that is possible, but it means making the turbo work harder which in turn creates more heat less power so on n so on. a healthy fowing turbo setup is more advantagous over a restricteve setup runnig higher boost pressures

mi8turbo: Mi16 one opens both same time, 605 one opens one at the time, just as the one that's on my car at the moment.

So I think there are 2 versions of Mi16 tb's, one that opens at the same time (possibly D6C), and the other that opens one at the time (possibly DFW).

I'm not sure about the throttle body sidewall thickness, but you could definitely bore it to a larger size, at least at the part where there is a reduction (where the butterflies actually are.

There is a mark 78° on the 605 butterflies.

Isn't it better for a turbo car to have a single throttle body? I'm just asking this as I've never seen a turbo car that has a double tb mounted by car manufacturer.

I've got two D6C-engines, both have tb's that open "one at the time".

That means there are no rules about it. I thought the one opening both at the same time was D6C because it had a stamp of year production - '89, I guess I was wrong.

Anyways, on the 605 one there is a serial number 42CFP26 197 2, and on the Mi16 one 38CFP 6 0030, so the first 2 numbers obviously mark a throttle bore dimension.

yes single tb is one of the better routes to go but ill be running standard mani from 405 sri so cheapest option is to get the mi16 bored out to what ever it can take

my dc6 tb opens both at the same time

Good find but I imagine these are gonna be pretty hard to get hold of.

hence the idea to bore out the mi to suit bigger butterflies. does anybody know the limits that the mi tb can be bored out to ?

If you look at that throttle body from the 605 the bores are same size as the Mi16 throttle body until down by the butterfly valves. Then on the Mi16 item there's a step that narrows the bore to 38mm, that's not present on the 605 tb. And when you view both from behind you can see the 605 one has thinner walls, just like it's been bored out.

why not make life easy and use the RFS single throttle body inlet? 63mm IIRC..

Are there outlets on the pipe connected to the throttlebody though? Need somewhere to connect breather pipes.

Yep theres a nice large breather outlet on it, and a hole on the underneath of the manifold that the Idle valve can be connected to, would just need a pipe to the AFM making which isnt hard.