pp13bnos

iTrader: (1)

I was curious if there where any gains in having your LIM, extrudehoned or anything. From what I understand, the LIM is a restriction, not the upper. Is this correct?

When I tear my FD apart to go single, and have the motor ported, I was thinking about having it done, and curious if the cost was worth the hp. Has anyone done this with any kind of results? Even if its a butt dyno, I don't mind.

Later, CJ

fdracer

no gains really. it's not really a restriction because the intake port inlets are the same size. it's just that it's restrictive when compared to the uim, but overall it's not a restriction, cause there are more restrictions downstream. it's major problem is that it makes a 90 deg. turn right at the end where it is also constricting to the size of the intake ports. you can't change the basic shape w/ extrude honing, so the restriction is still there.
the best you can do is to feather the lower wall of where it meets the port to get a bit larger turn radius.

RonKMiller

Match porting and polishing the entire intake tract is good for a 6% increase in flow. I've seen certificated bench results from a lab. It's a lot of work. It's especially hard to reach inside the UIM for polishing but it can be done with special tools and a lot of blood, sweat and tears.

When you consider how efficient the whole 3rd gen STOCK intake is to begin with this is an incredible improvement. Not sure what the hp gains are but it is significant. Unlike radical porting there is no loss in low end torque or idle quality, indeed, it improves both. I would think a mild street port would compliment it nicely.

There is no downside to this except that it is very time consuming and $$$ and requires a bit of "artistic ability" to pull it off. It's probably the most overlooked mod out there.

hapa

I remember a discussion about porting the lower intake manifold taking place on the big-list about 2 or 3 years ago. It was stated that there would be little if any gains by porting the upper, but the lower would yield significant improvement. Anyone have any details of the discussion they would like to share? I have searched my archives, but I don't have any notes. Does anyone know someone that has done this or knows much about porting this piece? I've always wondered about the modification myself.

thanks,
eric

RonKMiller

Jay has been racing and building rotaries since the early 70's: He does exceptional porting work, truly meticulous.

From his site:

Rotary Response and Racing

Flow Bench - Tech findings.

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Air flow rates for FD3S intake manifold being generated....
Comparison tests between a stock and modified intake manifolds show promise....
Initial tests are showing a 4% increase in air flow through a modified intake and dynamic chamber...

--------------------------------------------------------------------------------

02/01/01-03/12/01
All parts tested are 1993 FD3S US Fed spec

Preliminary test runs of a modified intake manifold and dynamic chamber indicate that there could be a significant gain in air flow made for a reasonable cost.

Runs made on a flow bench using of a FD3S intake system mounted to FD3S intermediate and rear housings.

At 20in of H2O vacuum the flow was 97% with open non ported new FD3S housings.

Stock lower manifold: 92% loss of 8%

with dynamic chamber: 89% loss of 11%

Modified lower manifold: 97% loss of 3%

with dynamic chamber: 93% loss of 7%

These are only the first tests on this manifold and by the results found, it is optimistic that further improvements can be made. Even so 6 to 8% with an affordable price tag right now looks very feasible.

Please email for more information and to get on a mailing list so you can be notified when the new findings are ready. email rx4ur7@theriver.com subject: FD3S INTAKE

Air flow tests on modified housings are also showing improvements.

As it shows now a 15% to 20% increase overall in air flow seems very obtainable

Granted Mazda has made this powerplant very efficient. Nothing like the earlier motors. Especially the hard to flow six-port motors. So any improvements now are going to be small. It is when you add up all the 5%'s here and 7%'s there that we are seeing excellent results. We have a test car on the street now. Images to be posted soon.

1993 R1 modified induction, cleaned up ports in housings,clean up oil system ports, PFS intercooler, intake, silencer, Bonez downpipe, PFS engine management system, CenterforceII, Jacob's wires, Redline water wetter and SI1, Redline 2-cycle race oil added to fuel. All stock otherwise. But from the short time on the road it has shown that we will have to be doing some suspension work to handle it. Otherwise, driveablilty is excellent.

Turbo lag- doesn't happen. Smooth through all transitions.

This car is emissions legal, fast, and fun to drive.

April 05, 2001

fdracer

yeah that's kinda what i was saying. but you have to remember that the intake ports are also a bottle neck. so gains you get from porting the lim will be somewhat negated by the intake ports. the lim is not the only bottleneck so gains from porting it will not be appreciable.

mmaragos

I don't quite understand what you are saying. They (Rotary Response & Racing) flow tested the assembly with non-ported housings and that test showed an improvement.

Just the LIM was a 5% improvement, LIM with the dynamic chamber was a 4% improvement.

Not hacking...just want to understand.

paw140

What is a dynamic chamber?

fdracer

oh ok so it was flow tested w/ the intake ports. so the dynamic chamber is the intake port?

pp13bnos

iTrader: (1)

Good stuff. I guess I'll start looking for prices from different people.

My goal is 450rwhp, at low as boost as possiable.

Thanks for the info guys, and if you have anything else to share, please feel free.

The dynamic chamber is the first part of the upper intake manifold. Right after where the throttle body is.

CJ

fdracer

yeah, so where does it talk about the intake ports?

RonKMiller

rxrotary2_7

https://www.rx7club.com/forum/showth...=port+matching
interesting thread.

fdracer

a little different on a turbo engine though, cause the intake charge is pressurized. exhaust really can't escape out the intake port. match porting would help laminar flow, in fact the step between the manifold runner and intake port in a mismatched interface will cause reversion. but again i'd say the power gains w/ match porting can't be felt unless on an all out race motor.