upper intake manifold
 

any one have a custom intake manifold made?? im going to have one made this winter to eliminate the bulky oem one. and have a smoother transition into the lower intake .

are you still NA? not sure why you'd want to unless boosted :dunno:
did you even try google?
aftermarket custom inltet manifold

yes ive looked through web sites for years,
there was a company that made a cast one a years back but nothing ever came of it. figured id ask see if some one did but never posted anything about it.

There are many benefits from modifying or upgrading intake manifolds. Changing the Runner length alone can have massive effects on the effectiveness of a power band, and Peak Torque as well as Peak Horsepower

Though Mazda's is optimized for the best blend of peak horsepower while retaining good midrange torque, (it also has valves that open/close to balance Torque and Peak Horsepower as well) - that is speaking specifically towards 100% stock car. There are plenty of modifications that you can do to a NA Rotary, Renesis included that can cause the factory intake manifold to start holding the car back.

For a street car with basic bolt ons and a flash tune, I would strongly urge to leave the intake manifold alone - Alot of people will have a hard time wrapping their head around this next statement but for a NA 2 Rotor that makes the high rpm power it does, the RX-8's midrange torque is actually surprisingly good in my opinion. You will miss it like no tomorrow when it is gone on the street..

If you have a fullout race car that spends most of its time above 7,000RPM with some crazy 1 off header, a 10,000RPM Redline, and some crazy Port work, then it would be a good time to look at the intake manifold....

Something along the lines of almost half the stock runner length, and Individual Throttle Bodies sorta like this....


http://i1228.photobucket.com/albums/...psaeef5967.jpg

Though I do believe a Full Bolt on and Tuned NA Renesis, especially with a mild port job of some kind would benefit from a larger throttle body that was matched insize at the manifold.

My experience with various other cars like S2000's and my Silver car is most engines benefit from a slightly larger to massively larger Throttle body with piping, and the Manifold being bored to match it...

The reason they usually end up with a slightly too small throttle body is drive-ability. With a Large Throttle body, the throttle can be too responsive for the average joe, (slight-mild Snap feeling a bit like a on-off switch, which The RX-8 *mine at least* Does do this slightly) and also often lead to jerking at low RPM's when trying to hold the throttle steady to maintain speed (Like my Silver car at 25-30mph in 2nd gear) despite being early driveby wire, with how responsive the RX-8's throttle is stock, almost like the stock TB is too big for consumer level drive-ability, I can see that being the case....

If recall correctly, I remember accidentally finding an old, old old, article or webpage of someone who dyno'd a stock Renesis, with a Halfway decent header, and a Lower Intake Manifold that allowed the removal of the stock upper, and replaced it with a nice Carbureted Multi-Velocity Stack setup, and it made something like 270-280hp (Flywheel) on a engine Dyno on mere 87 octane fuel... Torque was not near as sufficient but it made all the high rpm power in the world.

Oh yes defiantly!! My full bridge na rx7 was a beast but only above 5k used to take out turbo cars all day, with a smooth 215 220 to the wheels, i was going to go shorter on the manifold we were estimated to gain 30 -40 more hp from the design defined auto works was making for me, but i parted ways with her and got the mazdaspeed rx8 instead. im still not sure how this build is going to go.

Not me. I happen to share your opinion.