malahhaor

Hi guys, cross posting from 6Speed, hopping some tech knowledge lurking here that could help me.
I just got 06 C4 and Im wondering if there is any differences in 3.8 intake manifold vs the 3.6. Would there be any advantage in air flow if i swapped mine to a 3.8?

I'm thinking of getting 82mm TB and 82mm Plenum and i'm not sure if 3.6 manifold would even benefit from that upgrade. Perhaps if i combined it with 3.8 intake manifold it would provide a much better airflow to cylinders?

Any info would be appreciated.
Thank you

OKB

They are different engines I doubt if they would be interchangable. But my experience with tuning a 3.6 I would go with a IPD plenum and a cold air intake like K&N. I had it, It worked. The whole system will make a performance difference with a complete free flow exhaust, try Agency power, and a ECU program, Get a good one like EVOMSIT or REVO, etc.

Petza914

Go with the Evolution Motorsports or Fabspeed intake over the K&N. The K&N uses plastic tubing - EVOMS is metal tubing with a plastic box and Fabspeed uses Carbon Fiber. With the metal tubing, you can get the clamps nice & tight so you're sure there aren't any air leaks with air getting past the MAF. I have the Fabspeed J-Pipe on my car (my car is modded with a supercharger and although I tried the newer Y-Pipe, it didn't work as well, but with a stock engine, it's better) an my wife's has the EVOMS intake. I had put the K&N on her car before the EVOMS so I have first hand experience with all 3. My car has the full Fabspeed Valvetronic mufflers, headers, X-pipe and my wife's the Gundo hack.

utkinpol

Do plenum if you want but i would leave rest of intake alone.

malahhaor

thank you guys. good info.
So Im thinking to get 82mm TB and 82mm IPD and will pair it with EVOMS intake

Any thoughts?

alpine-al

The 3.6 and 3.8 intake boxes are the same size and shape and both have a resonator that modifies the intake sound, but the resonator in 3.8 box is controlled by a vacuum line that deactivates the resonator at higher RPMs. If you have a 3.6, you don't have the vacuum line - so don't bother with that.

I believe that you can get the same benefit of the Evoms intake by putting a BMC or K&N air filter in your 3.6 box. I wouldn't get a Fabspeed or K&N warm air intake unless I was only interested changing the look of the engine bay.

If you install an 82 mm GT3/X51 throttle body and an ID plenum, then you should also install 200 cell cats - otherwise you wont get much of a performance improvement. Although you might get a bad headache when you go for a state inspection sticker (if you live in state that tests for engine mods).

.

malahhaor

Yeah Fabspeed looks nice but too much hot air. I've seen this with other cars as well.

I will get cats done a little later when i take few days off in December.

Petza914

There are many threads about this with actual specs (temperature readings) to prove it, but in reality, the only time these intakes would be sucking warm air is when the car is sitting still or barely moving. Once underway, the volume of fresh air entering through the decklid prevents the intake from sucking engine bay air or it sucks so little of it as a percentage that it doesn't really matter. Fabspeed also redesigned the CF heat shield on their newer Y-intake to block off almost all of the engine bay and with the dual intakes right under the openings in the decklid (once the right side is punched out on the template), it's sucking a tiny percentage of warm air from the engine bay, with almost all of it entering through the decklid . Both the EVOMS and Fabspeed are great units.

Becuase of the Kompressor pulley and RUF CF decklid, the only aftermarket intake I could use was the Fabspeed one and the heat shield had to be modified to fit (heat shield mounted backwards with a standoff bracket and new larger semicircle created for the intake pipe), but the car has much better throttle response and accelerates much harder in the higher revs where the stock airbox was running out of capacity to flow capacity. RUF determined this same thing and part of the R-Kompressor kit was to create holes in the OEM 3.8 airbox base to allow more air to enter than was possible through just the one upper opening on the left side.

My wife's car, in addition to the EVOMS intake, also has the IPD plenum which sharpened throttle response and makes the car smoother and more powerful at higher RPMs. I couldn't use the IPD on mine because my intake manifolds are completely different due to the RUF Supercharger so the standard T-style plenum is gone.

malahhaor

Thanks for all the feedback guys, much appreciated.

OKB

if you look at that K&N it has a very contained air filter. the air comes in thru the hood air inlet hole. The Fabspeed is open to the engine bay, which is hot air.
The ideal of a cold air intake is to only let the cold outside air into the air filter, as opposed to heated enging air.
This pic is of a K&N for my 996, also has a very contained channel for cold air from the outside
Maybe K&N arent as showey but they are more effective

utkinpol

Crazy. Is it original wrapper shipping plastic around that cone? How can it get any air at all this way?

Those cone shaped filters must be used only on forced induction cars as then hot air it sucks from engine bay goes via intercooler so it does matter. It was all tried and tested many times. No one runs such thngs on NA track cars, it kills timing and, no, air flow via holes in deck lid is not even nearly cmparable with amount of air motor sucks in at hi rpms.

On any naturally aspirated car it leads to problems with timing and loss of power as it keeps sucking in hot air. It is a worst marketing crap, those so called CAI systems as they are not CaI at all. Stock airbox is CAI. If you want more efficient CAI - spend a grand and get x51 dual intake airbox.

As of having gt3 bigger throttle body - you will need bigger x51 headers and 200 or 100 cell cats with ecu tune to get full benefit from additional air it can pump through. With stock ecu bigger throttle body most likely will lead to issues.

malahhaor

so another question for you guys.
The intake manifold has this second tube that's located between the two halves towards the back of the engine. Like the plenum but no external air comes in. What does it do? Equalizes air between manifolds? I would think better design would be to have the air come in and get delivered equally across all 6 rudders instead of being upfront pointing to two rudders and then get equalized to the others.
Perhaps a new plenum is in order

semicycler

The GT3 design is exactly like you describe.

malahhaor

Interesting. Hmm.... Looks like a good opp for me to play around.
I know it would be easier to just get a new manifold but its the journey not so much as the result

StormRune

Be sure to realize that you will almost certainly need to buy an aftermarket tune if you change any intake part from the throttle body on down. Otherwise the car will run worse and will likely throw a variety of check engine codes. I'd recommend that you check with one of our sponsor tuning companies before proceeding.

On the subject of the second port, rest assured it is there for a good reason. A lot of performance comes from tuning of the dynamics and harmonics of the air flow that are beyond me and I think it is almost certain that the back port is there to improve performance by insuring that the pressure pulses and vacuums caused by the opening and closing of valves work to assist the engine's consumption of air instead of hinder it or hit it randomly.