diyman25

I think about 10-20 WHP depend on your mod.
on my friend Knight sport we do a back to back test between a Test pipe and High flow cat. we see about 15WHP different on DYNO JET.

On my T04R I loose more about 20WHP, compare to the test pipe.

What about every one result
J

SlvrRexx

I"m not sure how much HP you lose but i heard that a high flow cat allows your turbo to spool up faster

maxcooper

I am putting a cat on my new R85 setup. However, I know that it will cost some power and I seriously doubt it would make the turbo spool faster (???). Maybe I will try it with and without eventually and do a dyno comparison. I have always wondered how much power the cat costs, too, and I haven't seen much test data.

-Max

diyman25

I think what he is saying is

With CAT, there will some back pressure. and your TQ curve will be a bit better compare to straight pipe...

Rhode_Dog

There was a thread a while back on those new mettalic cats, which are supposed to flow almost the same as a midpipe.

https://www.rx7club.com/showthread.p...ght+Sports+Cat

https://www.rx7club.com/showthread.p...ght+Sports+Cat

There's a few, i know there were more threads.

maxcooper

The problem with all the tests I have ever seen for these cars is that the car is not re-tuned for both tests (cat and no-cat). I realize that would be a lot of work, but the results aren't all that trustworthy otherwise with the FD's speed-density FI system.

And although I not a believer in the myth that backpressure increases torque (but rather that smaller pipes scavenge better at low flow rates, which isn't the case with a cat in a big pipe), I have just imagined how that might actually be true on a turbo car under some circumstances (backpressure and boost "stuff/hold" more fresh air in the combustion chamber than boost with no backpressure... hmm). Still, I am 99.99% sure that my car would spool better with a straight pipe. I can always do a test with some datalogging at some later date if I really want to see what difference it makes.

-Max

books

iTrader: (8)

I used the same timing maps but the AFRs were about 0.8 higher with the midpipe. The boost was nearly identical. I don't remember the exact numbers for boost, intake temps,etc.. With a Bonez hi flow cat (stock twins) the peak horse was 311. With the midpipe peak was at 321. Both runs were datalogged.

mjw

iTrader: (1)

Max:

I am curious which cat you are considering purchasing? I have been eyeing the Knightsport cat like some other people, looks like a nice product although the price of entry is steep..probably looking to cut down on that stink in So Cal like me?

-Matt

SnowmanSteiner

Maxcooper, I'm surprised. If you look at one of the dynamics of torque, that specifically related to the rotary, is that with heavier rotors you yeild greater torque due to the amount of mass being revolved at certain RPM's. This is obviously to a point. But the basic concept of that is that with greater resistance, to a point, higher torque will be produced due to the strain. So with greater backpressure, again to a point, the exducer will have higher torque and spool faster. This is a rudimentary assumption that I've made, so if anyone has substance that disproves that, please relay it. As I love to learn, and am always eager to seek out new information that can benefit.

- Steiner

maxcooper

I don't believe the "heavy rotating assembly increases torque" myth, either.

I don't understand what you mean by "So with greater backpressure, again to a point, the exducer will have higher torque and spool faster."

-Max

maxcooper

I've got an N-Tech cat that I will be using, at least at first. I was thinking of picking up the largest Magnaflow available (or perhaps another maker).

One of those metal cats sounds interesting, too. I have a 5.0 Mustang and Fast Fords where they dyno test a metal cat versus some "known hi-flowing" ceramic cats and they came out with roughly the same results. They also tested a straight pipe which made a little. but not a lot, more power on their test car.

-Max

jhillyer

The cranking assembly mass costs. The exhaust begins venting and dropping pressure on the rotor, having assisted it's companion rotor into compression, the inertia continues the torque output until the companion's combusion thrusts. That exhausted rotor's inertia is useful after its exhaust stroke dumped, but it initially cost early in the combustion, and from previous combustions.

This storage and release is balanced because to reap torque without combustion pressure requires leaching inertia from the crank assembly*, and leaching inertia will slow the assembly if combustion does not replace that inertia.

A dynomometer designed to measure torque between combustions probably would see the latent torque per cycle, but I think if we see heavy rotors outperform lighter, the NSU-Wankel has a ('nother) design flaw.

*really beyond the flywheel and including the rolling vehicle if entire driveline is coupled