What makes the FD intake manifold better than the T2's?
12-21-07, 04:35 PM
#1
What makes the FD intake manifold better than the T2's?
Forget about throttle bodies for this discussion. It looks like the FD has longer runners maybe (at least the UIM), and larger diameter? Why is the FD manifold considered an upgrade? I can see how the 13BRE is way better with its larger runners, but I'm not clear on the FD's.
Now obviously the n/a s5 manifold is way better than the s4 n/a, but what about for the T2? And are there any major differences between the s4 and s5 T2 intake manifold that would actually affect the powerband?
Now obviously the n/a s5 manifold is way better than the s4 n/a, but what about for the T2? And are there any major differences between the s4 and s5 T2 intake manifold that would actually affect the powerband?
12-21-07, 08:42 PM
#6
hey fellas, look at what I found:
http://www.rx7.org/public/13BTvs13BREW.html
UIM:
I'll hopefully test a bunch of things out throughout '08.
http://www.rx7.org/public/13BTvs13BREW.html
One significant difference on the 13B-REW is the areas around the dowel pins on the side housings. They are reinforced and ribbed with thicker castings. This is a major problem area on high output 13BT engines, as they tend to crack at high power levels and is the main reason that the 13BT blocks are not reliable beyond 400HP. Most competent rotary rebuilders will look for this before rebuilding a 13BT motor. The 13BT GTX blocks are said to be more reinforced than the earlier motors but not as significantly as the newer 13B-REW designs. Before the introduction of the 13B-REW motors, some engine builders experimented with brazing extra metal around the dowel pins area on the side housings of the 13BT motors.
The port sizes on the 13B-REW are extremely larger than the 13BT's, especially the primary ports on the intermediate housings. This is accomplished by increasing the height of the side and intermediate housing where the ports are located and relocating some of the coolant passages inside the housings. The larger ports increase the duration and "lift" of the intake stroke, allowing more air to be ingested into the combustion chamber. While the intake ports are larger, the intake runners of these motors are still about the same size. The 13BT intake manifold has a surge tank plenum which is found to create too much pumping losses because of its large volume. The 13B-REW intake manifold is a "Dynamic Pressure Intake System" which eliminated the surge plenum tank and has opposed-facing secondary intake runners. This new design enhances intake flow by taking advantage of the strong pressure waves inherant in rotary engines. The throttle bodies on the 13BT are 3x45mm, while the 13B-REW are 1x45mm + 2x50mm.
The port sizes on the 13B-REW are extremely larger than the 13BT's, especially the primary ports on the intermediate housings. This is accomplished by increasing the height of the side and intermediate housing where the ports are located and relocating some of the coolant passages inside the housings. The larger ports increase the duration and "lift" of the intake stroke, allowing more air to be ingested into the combustion chamber. While the intake ports are larger, the intake runners of these motors are still about the same size. The 13BT intake manifold has a surge tank plenum which is found to create too much pumping losses because of its large volume. The 13B-REW intake manifold is a "Dynamic Pressure Intake System" which eliminated the surge plenum tank and has opposed-facing secondary intake runners. This new design enhances intake flow by taking advantage of the strong pressure waves inherant in rotary engines. The throttle bodies on the 13BT are 3x45mm, while the 13B-REW are 1x45mm + 2x50mm.
I'll hopefully test a bunch of things out throughout '08.
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12-21-07, 11:02 PM
#8
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when you do the swap you use the fc LIM you have to get the fd UIM port matched , also the air flow with the fd UIM is a straighter shot (as mentioned above) remember you want evrything to flow as easy as possible
12-22-07, 06:03 AM
#9
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look nearly identical to me
Isn't there an issue with the FD LIM with the uneven lengths of runners from one rotor to another causing one rotor to go lean? Maybe this is why people use the FD UIM on the T2 LIM? and not the FD LIM?
12-22-07, 08:55 AM
#11
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12-22-07, 10:21 PM
#13
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thats correct, heres how you wire it incase you are considering doing the swap and still have your stock ecu
https://www.rx7club.com/showthread.p...&highlight=tps
12-23-07, 01:01 AM
#14
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You can machine a FC TB with FD plates. So I think He was avoiding the whole discussion of TB variables, and just focusing on the manifolds.
12-23-07, 03:59 AM
#16
The 3rd gen UIM has a better dynamic wave effect on the 2ndary runners because the runners curve around to face each other across a low volume plenum. Because of this less acoustic wave energy is lost en route to the opposing port.
The smaller plenum volumes (primary and secondary) in the 3rd gen UIM also decreases pumping loss as previously stated. Basically, the air spends less time accelerating and decelerating from the lower velocity higher volume plenum into the high velocity low volume port runners during normal (and reversion flow).
This smaller plenum volumes in the 3rd gen UIM is enabled by the very fast spooling tiny primary turbo in the twin sequential turbo system. Like a supercharger it is always providing some boost under load to smooth reversion and pulsation as a larger plenum would.
So, with a slower spooling turbo the 3rd gen UIM should have somewhat less driveability than the 2nd gen UIM or Cosmo UIM due to the lack of plenum volume.
Finally, the most important advantage the 3rd gen UIM has in my opinion is that it looks cool.
The smaller plenum volumes (primary and secondary) in the 3rd gen UIM also decreases pumping loss as previously stated. Basically, the air spends less time accelerating and decelerating from the lower velocity higher volume plenum into the high velocity low volume port runners during normal (and reversion flow).
This smaller plenum volumes in the 3rd gen UIM is enabled by the very fast spooling tiny primary turbo in the twin sequential turbo system. Like a supercharger it is always providing some boost under load to smooth reversion and pulsation as a larger plenum would.
So, with a slower spooling turbo the 3rd gen UIM should have somewhat less driveability than the 2nd gen UIM or Cosmo UIM due to the lack of plenum volume.
Finally, the most important advantage the 3rd gen UIM has in my opinion is that it looks cool.
12-23-07, 10:08 AM
#18
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Huh, I didn't know that. Interesting how similar this is to the NA manifold design.
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