s5 T2 vs s6 FD UIM design
10-08-09, 02:41 PM
#1
s5 T2 vs s6 FD UIM design
This topic is more of a concern for 2nd gen owners and also be more academic than dyno driven. Besides the larger FD throttlebody and intake ports/runners (which would help to some degree), it seems to me that the s5 turbo UIM architecture would be better if your goal were topend power. The main things to consider would be plenum volume then runner length and diameter.
Don't many high peak hp, high rpm powerband cars out there use large plenums? Even factory designs tend to favor large plenums for high rpm use. The NSX increases the effective size of the plenum volume when in high rpm operation, and that got me thinking.
The runner diameters are different to reflect the larger FD ports. Now for the runner length: I know there is the dynamic supercharge effect as the two rotors alternate the opening and closing of the intake ports. But all the nonturbo VDI intake manifolds (s5, Rx-8) use the longer runner setup for low and midrange torque and the shorter runners for high end.
I've got my car set up for high rpm driving right now. It has a larger turbo (T04R), long runner divided exhaust manifold, big streetport with big exhaust ports, and the short close ratio gearing of the s4 turbo tranny. I've thought about the FD UIM but it just doesn't seem like much of an improvement for my type of setup, even with the larger TB. The 13B-RE has a large plenum volume, that seems like it would be best for this kind of application.
10-09-09, 07:12 PM
#3
I once did a project on a full ported 6 port engine with a t70 turbo, the ports were ported together and i still had the high compression 9:4:1.
I ran a complete fd intake set-up since i had a friend who tig welded for a living all we had to do i cut and reweld only one piece of the manifold and resurface the mounting face that meets the block. i then made a custom throttle bodie set-up consisting a custom made adapter plate to a 80mm or 90mm dont remember the exact size single throttle bodie. I ran the car with the stock t2 manifold on this block and yea it was nic but when i ran the fd intake on it the top end was like having another motor push me down the road. Keep this in mind with intakes.. the shorter the runners the lower the torque and higher rpm and top end power, but when running more runner with more plenum you will get more torque and less top end. Also to look into on the cosmo intake manifolds the primary intake runners only run off the bottom hole of the throttle bodie its all seperated unlike the t2 plenum and the FD plenum they all are connected and run together.
I ran a complete fd intake set-up since i had a friend who tig welded for a living all we had to do i cut and reweld only one piece of the manifold and resurface the mounting face that meets the block. i then made a custom throttle bodie set-up consisting a custom made adapter plate to a 80mm or 90mm dont remember the exact size single throttle bodie. I ran the car with the stock t2 manifold on this block and yea it was nic but when i ran the fd intake on it the top end was like having another motor push me down the road. Keep this in mind with intakes.. the shorter the runners the lower the torque and higher rpm and top end power, but when running more runner with more plenum you will get more torque and less top end. Also to look into on the cosmo intake manifolds the primary intake runners only run off the bottom hole of the throttle bodie its all seperated unlike the t2 plenum and the FD plenum they all are connected and run together.
10-11-09, 02:59 PM
#6
no the cosmo has more low end power hense it is in a luxury automatic car. The cosmo is more likely to be driven for dayly driving with the ocasional pull but as for the fd the manifold design has more top end flow with lower low end hense its more of a high performance car not a luxury car. i have driven both and a cosmo engine has way more low end driving comfort than a fd where u have to use more rpms when driving
Trending Topics
10-14-09, 12:00 PM
#9
The FD intake manifold is an improvement over the FC manifold simply because it has less turns. The runners in the manifold appear slightly smaller though which makes no sense with larger throttle plates. There isn't much of an effective "plenum" on either manifold but what is there resembles a dual plane V8 manifold in pricinciple. Not because each side feeds half the engine but rather in the way the air flows through the throttle plates. If the dynamic chamber, as Mazda calls it, were hogged out to one large chamber, top end would improve but low end and part throttle drivability would suffer a little bit. This fits right inline with single plane manifolds vs dual planes on V8 engines.
Another thing that helps the FD manifold is the engine itself. The intake runners don't enter the FD engine from the side parallel with the ground. They enter in at a downward angle. The lower intake manifold as such also has it's runner pointing down a bit which is why you can't integrate the lower manifolds onto FC engines, even with an adapter so it bolts up. You can adapt the upper FD manifold onto the lower FC manifold though with little effort. It's not quite a direct bolt on and does need a little work.
My personal opinion is that a street driven turbo rotary should have long intake runners and a decently large plenum volume, being careful not to go too large on throttlebody size.
Another thing that helps the FD manifold is the engine itself. The intake runners don't enter the FD engine from the side parallel with the ground. They enter in at a downward angle. The lower intake manifold as such also has it's runner pointing down a bit which is why you can't integrate the lower manifolds onto FC engines, even with an adapter so it bolts up. You can adapt the upper FD manifold onto the lower FC manifold though with little effort. It's not quite a direct bolt on and does need a little work.
My personal opinion is that a street driven turbo rotary should have long intake runners and a decently large plenum volume, being careful not to go too large on throttlebody size.
10-14-09, 12:15 PM
#10
From what I saw working on the FD and FC manifolds-
the FD has slightly larger diameter secondary runners. Like the difference between the S4 and S5 TII secondary runners yet again or about 1mm.
The FD has quite a bit smaller primary runners than the FC TII manifolds.
The smaller "plenum" on the FD manifold is designed to diffuse the dynamic wave less as it travels from one opposing secondary runner to the other.
A continuation of the difference between the GSL-SE 13B plenum and the FC NA plenum where they rounded out the corners inside the secondary runners plenum to increase dynamic wave effect.
the FD has slightly larger diameter secondary runners. Like the difference between the S4 and S5 TII secondary runners yet again or about 1mm.
The FD has quite a bit smaller primary runners than the FC TII manifolds.
The smaller "plenum" on the FD manifold is designed to diffuse the dynamic wave less as it travels from one opposing secondary runner to the other.
A continuation of the difference between the GSL-SE 13B plenum and the FC NA plenum where they rounded out the corners inside the secondary runners plenum to increase dynamic wave effect.
10-16-09, 08:52 PM
#11
The lower intake manifold as such also has it's runner pointing down a bit which is why you can't integrate the lower manifolds onto FC engines, even with an adapter so it bolts up. You can adapt the upper FD manifold onto the lower FC manifold though with little effort. It's not quite a direct bolt on and does need a little work.
Thread
Thread Starter
Forum
Replies
Last Post
Turblown
Vendor Classifieds
12
10-17-20 03:25 PM
