Air intake plenum modified to larger diameter intake?

[MarkSanne]

Last week I did some work on the old VR2 (new clutch, fresh fluids, new suspension arms straight and curved, new axles, new custom downpipe) and while I had to get the V6 N/A throttle body back on the VR4 intake plenum (which is a PITA) but I wanted this setup mainly because of the factory cruise control which I enjoy very much on long trips.

Then I started to wonder how much of a difference in diameter both really are. So I took my gauge caliper and measured the V6 N/A throttle body opening diameter and then the VR4 intake plenum opening. The VR4 intake opening is 5mm smaller. Hmm... As I was also replacing the steel gasket for a 3mm teflon (self cut) version (needed badly as the VR4 one doesn't cover a vacuum hole from the V6 N/A TB) I thought this was a good moment to start using my spare VR4 intake plenum and widen the opening. I used like 15-20 dremel grinding belts to get it done and actually ended up just over 5mm... oops. I don't think there is any harm in that, but...

Has this been done before and has anyone noticed or better yet: measured any differences?
I haven't mounted it yet, will probably do so this weekend.

gasklepv6.JPG
V6 N/A TB opening diameter

gasklepvr4.JPG
VR4 stock inlet plenum opening diameter

vr4-inlet-manifold04.JPG
Wider opening, more air, more power?!

vr4-inlet-manifold03.JPG
Did a bit of polishing on the outside too just to make it look a bit more fresh

pakking.JPG
Stock VR4 vs teflon 3mm self cut gasket (great idea thanks to @swinks)

FYI: rest of the setup on the engine is a very low down mounted K&N airfilter with quite slow bend to MAF, all 2.75" dual exhaust, no cat (I'm allergic), stock boost, stock IC.

[Davezj]

@swinks has done it before, and i have just bougt the V6 N/A throttle body and plenum off him as i could not find an auto throttle body with TCL for sale out in the wide world of the interweb.
it was the TCL bit that i wanted to i could continue to use it on my PFL.

I believe the facelift have the larger throttle bodies already. bbut i could be wrong.

[swinks]

Yes, I did that. Thanks Dave for mention.
Just beware that vr4 opening hole although smaller is located in exact cenntre of flange, where v6 one is locatted slightly off-side.
In general, v6 throttle body has intake of 70mm and outlet of 75mm, vr4 is 65mm and outlet 70mm.
So, once you replace TB you won't fit plastic pfl elbow over v6 TB.

[MarkSanne]

Thanks guys! But Tomasz, did you find any effect from doing it?

BTW: The VR4 plastic elbow will fit over the V6 N/A but it is insanely tight. I had to use black gasket silicone kit and glue the rubber grommet onto the inside of the plastic elbow or it won't stay in place. But ever since I can get it on and off although I usually need to use a bit of spit to get it to slide over (it's such versatile stuff to get things going!).

[Davezj]

i have not even had a chance to unpack the one i got off tomasz. so this weekend i will have a look. i have just bought some new plugs to go in when i change it over.

[fassi1]

I usually need to use a bit of spit to get it to slide over (it's such versatile stuff to get things going!).

I would recommend silicone grease for this kind of operations