Bigger intake plenum and throttle body

[Br1jzl]

Hey,

I've been searching forums again and was reading about the bigger throttle body for the PFL Galants and legnum, but I was wondering if anyone knows of a bigger intake plenum/runners?

Also, does anybody know which car the 68mm throttle body is from?

[Cairnsy]

im interested in changing to a bigger throttlebody also. whats the size to go for and where can i get it.

[Davezj]

Other than changing from a PFL to fl throttle body I don't think there are any people that have done a bigger throttle body.
Are you considering changing the plenum chamber as well?
You can't fit a much bigger throttle body on the factory plenum, only a few mm of metal on the mating flange.

There are plenty more cost effective mods to do like bigger turbos and cams that will give you more power rather than just a supporting mod that will probably not add anything to the power.

Depending on manual or auto gearbox changing the throttle body can be more difficult. 2 sensors on the auto one on the manual, plus the idle control valve.

[Pugme]

Is he not on about the mod of fitting the NA throttle body?

[Davezj]

well the profacelif throttle body is smaller than the facelfit throttle body, but i can remember the exact sizes off the top of my head, but i think it is something like 68mm PFL to 72mm FL, but even with that minimal change you still have to grind out the PFL plenum chamber opening to make it fit correctly. but you are not gaining much more potential volume with the FL throttle body. if you are going to do it a then a 90mm or 100mm throttle body will do nicely, not sure how the idle control would be handled though.

i think the the NA V6 is the same size as the VR4 Facelift one.

however i do know it is very difficult to find a larger throttle body to fit a PFL atuo VR4 with TCL. because the Facelift does not have TCL so does not have the correct vacuum actuator. the NA V6 auto throttle body is larger but the vacuum actuator operates in the opposite direction under vacuum conditions so you can't use that setup. the PFL VR4 auto TCL vacuum acuator does not bolt on to the NA V6 auto throttle body due to the different arrangement of springs and holes on the accel cable attachment side. but a NA V6 auto throttle body with cruise control does have a vacuum actuator on the front of the throttle body that operates in the same direction as the VR4 PFL auto TCL vacuum actuator. so if you can find one of those it will fit and work with you TCL.
unfortunately they seem to be few and far between. goog luck with the search.

manual PFL VR4 without TCL you can swap the throttle body over easily from a NA V6 or Facelift VR4, i believe.

hope this helps

[swinks]

Dave, IIRC, there is 64mm vs. 72mm difference.
Also, S90 throttle boddies are 70mm or 75mm, not 90 or 100mm. No-one use over 75mm throttle bodies (due to drivebility) but users of drag monsters running over 1000 bhp vehicles.
No power gains from bigger throttle body, just quicker, sharper response to loud pedal and moving torque band down the rev range :)
There is some power gain potential (roughly 10-20 WHP) from fitting bigger intake manifold plenum with matching throttle body, but... there is none available for VR4 ;)

[Adam.Findlay]

correct as swinks says the stock intake manifold is terrible, having a custom one made like my attached picture would net you some good gains.

73002

[Davezj]

Dave, IIRC, there is 64mm vs. 72mm difference.
Also, S90 throttle boddies are 70mm or 75mm, not 90 or 100mm. No-one use over 75mm throttle bodies (due to drivebility) but users of drag monsters running over 1000 bhp vehicles.

There must be people using them as there are hundreds for sale in both 90mm and 100mm size. I am only guessing this but if nobody was buying them there would not be so many for sale.
You just have to search for 90mm throttle body and hundreds come up.
Probably china mass produced rubbish but still there.

But I get your point about the 90mm size making the throttle response very snappy and not nice to drive while cursing around town. Thanks for pointing that out, very valid

There will probably be some kind of formula for sizing the throttle body and inlet plenum size and inlet manifold runners based of flow from the turbo. Well I assume there is.

[Oblivion]

correct as swinks says the stock intake manifold is terrible, having a custom one made like my attached picture would net you some good gains.

73002

/JawDroppi Drooling over that engine bay right now!

[swinks]

There must be people using them as there are hundreds for sale in both 90mm and 100mm size. I am only guessing this but if nobody was buying them there would not be so many for sale.
You just have to search for 90mm throttle body and hundreds come up.
Probably china mass produced rubbish but still there.

Ha ha ha... Dave those throttle bodies are for Nissan RB25DET or RB26DETT engines. It's down to construction of Nissan intake. /pan
Mitsubishi stock intake plenum openning hole diameter varies from 64 to 70mm and no-more. IIRC biggest common use TB in Evo is 75mm (Ford bolt pattern) to match aftermarket intake plenums of AMS, Bushur or Skunk.
And if not convinced... try imagine running hard pipes in matching diameter to throttle body, i.e. 90mm hardpipe system. :speechles
So... in Mitsi world, we rather stick to biggest possible TB diameter of 75mm, just because common sense and technical implications. :)

[Davezj]

Yes I take your point , so for easy of conversion the way to go is the facelift setup. Which is a bit of a pain for anyone with an auto box wanting to go for a facelift size throttle body.

[billybobboot]

Are the pfl and fl intake manifolds the same? I have most other suport mods may as well do this one.

[SEAN-NZ]

Yes it is