Just spitballin' - 3.6 plenum fit to 3.2/3.3 heads?

[spuggy]

Hey,

Just wondering; does a 964/993 plenum line up with the ports on a 3.3 motor, or is there a difference in port-to-port spacing between 1-2-3 on the same bank?

Looks to be pretty trivial to deal with bank-to-bank spacing, if that's different...

Thanks in advance!

[Tippy]

They’re the same

[oh snap]

I think you just need adapters for the studs. I think rothsport makes them

[Evan Fullerton]

Clewett makes some or TurboKraft can make them from their 930 aluminum EFI injector blocks. That's the route I went to get a proper taper from the ~42mm VRam intake runner ID down to the 39MM big port SC head size.

[Steam Driver]

PM me.

[spuggy]

Cool, thanks guys!

Had hoped it'd be that simple, but wasn't that hopeful...

Was looking at some of these (well, actually, a GT3 RS intake plenum caught my eye first), noticed ends obviously intended to fit straight onto ITBs and thought "hmmmm",

Then, not actually having $4K lying around for a rare carbon fibre motorsport part, I looked at some 964 manifolds and thought "gee, these look functionally identical - but much cheaper...", and "be pretty easy to connect the intercooler outlet to where the throttle body used to bolt on"...

I'm leaning towards alloy over plastic - other than weight, any reason to prefer the plastic ones?

[Steve@Rennsport]

The GT3 plenum is too big for a 3.0-3.3 and N/A engines will lose a lot of low & mid-range power unless ITB's are installed under the plenum. This one is best suited for 3.5 & larger.

The late 964/early 993 plastic ones can be made to work, however you will lose some low end power (unless ITB's are used under the plenum for N/A applications).

For turbo motors, its a nice upgrade when bigger cams are used.

[Tippy]

Originally Posted by spuggy

I'm leaning towards alloy over plastic - other than weight, any reason to prefer the plastic ones?

Apparently, the plastic ones flow more evenly from runner to runner.

I have an aluminum set if that is not a super concern for sale. It does not have a center section or any other supporting parts. It's just the manifold halves.

[Steve@Rennsport]

Originally Posted by Tippy

Apparently, the plastic ones flow more evenly from runner to runner.

True, but aluminum ones may be Extrude-Honed for effect.

[spuggy]

OK, I probably shouldn't be too coy about why I'm asking, 'coz guys are guessing

Car's a Motec 3.4 930, 8:1, heads ported to match 3.2 manifold(s) and SC cams. Runs great. Throttle response totally unlike CIS...

However, distance from the throttle butterfly to the valves is still ~2 feet; ITBs would seem ideal to further improve throttle response low speed/off-boost.

964 manifolds look like a laughably easy route; drop them on top of ITBs, the intercooler outlet->plenum joint is one fitting, one bend and a straight shot to the manifold throttle body flange...

Or am I missing something obvious?

[Tippy]

Exactly what I am going to do. Read my sig.

The 964 intake couples to ITB's with a simple silicone coupler and hose clamp.

[sp_cs]

I’ve have done similar recently using 993 intake and ATPower ITBs - more work still needed due to failed valve stem seals, but runs pretty well. Looking to use the opportunity to increase the CR with new JEs:

[ChrisBennet]

Originally Posted by sp_cs

I’ve have done similar recently using 993 intake and ATPower ITBs - more work still needed due to failed valve stem seals, but runs pretty well. Looking to use the opportunity to increase the CR with new JEs:

I don’t see a distributor. What sort of EFI setup are you running? (If it’s not a secret I mean.)

[sp_cs]

Originally Posted by ChrisBennet

I don’t see a distributor. What sort of EFI setup are you running? (If it’s not a secret I mean.)

Motec m84, Audi COP

[clutch-monkey]

Originally Posted by sp_cs

I’ve have done similar recently using 993 intake and ATPower ITBs - more work still needed due to failed valve stem seals, but runs pretty well. Looking to use the opportunity to increase the CR with new JEs:

what's the advantage of running a system like this instead of trumpets?

[sp_cs]

Originally Posted by clutch-monkey

what's the advantage of running a system like this instead of trumpets?

Torque is meant to be the primary benefit - i’ve read that the plenum provides a ready (pre-collected) dollop of air to expedite/improve combustion and sharpen throttle response.

William Knight mentioned to me that a common plenum will always provide more area under the torque curve than straight stacks.

[clutch-monkey]

Originally Posted by sp_cs

Torque is meant to be the primary benefit - i’ve read that the plenum provides a ready (pre-collected) dollop of air to expedite/improve combustion and sharpen throttle response.

William Knight mentioned to me that a common plenum will always provide more area under the torque curve than straight stacks.

interesting. i have CNC'd mounts for the plenum but my tuner prefers the trumpets (perhaps for setup). i may look at doing back to back dyno tests down the line.

[sp_cs]

The atPowers leave you with stubs so relatively easy to mount the plenum with use of silicone connectors.