Feedback on High Flow Cats vs Resonated Test Pipes; Benefits / Disadvantages of both?

[MileHighNSX]

I am looking into getting the HFC (300 cell) from the group buy that Mark put on through Pride. But as I was thinking about it the Resonated test pipes are a lot cheaper, so I was wondering what the differences are in flow characteristics between the two? Any opinions and experiences are welcome.

Obviously the resonated test pipes are straight through and will have no obstacles for the exhaust coming through to contend with freeing up some more horsepower. I also heard that your exhaust will smell more without a catalytic converter, (more pungent?) is it that obnoxious with a cat on the car? I will have to swap out to my current catalytic converters every two years when emissions are due if I go with the RTP.

On the other hand if I stick with the HFC (300 cell version) then I won't have to worry about passing emissions hopefully? The piping diameter will be the same throughout my exhaust system from the headers out to the exhaust system all at 2.25" alleviating the bottleneck that is currently happening right now.

I've gotten some feedback from other members saying that having some backpressure is good for throttle response and I don't doubt that, so if I go with either the HFC or the RTP will I loose some of the backpressure that I currently have due to enlarging the diameter of the exhaust system all the way through??

Thx guys

 

[clr1024]

I have the pride headers and resonate test pipes, I have not noticed any difference in smell. As for back pressure being good for throttle response that's a fallacy, it has more to do with the velocity of the exhaust gas exiting the engine and exhaust pipe diameter and mass flow. Theres a whole science behind it but exhaust gas will flow at a higher velocity through a smaller diameter pipe..until that diameter becomes the limiting factor for flow, which is why people go to larger diameter for more HP. However you trade a little in throttle response due to the larger tubing diameter and the initial push to get the existing gas/air out of the pipe. In short, it's not the back pressure.

 

[MileHighNSX]

Interesting, ok so I will trade off a little throttle response due to the larger tubing like you said, but once the exhaust gas starts flowing then the car can breathe better with associated modifications. Is that why you see gains in the mid to upper part of the rev range due to the fact that the exhaust has filled the larger diameter tubing and is now flowing more free??

 

[USAFguy22]

Performance gains between both will be negligible, even if it was 5hp at most would you be able to tell the difference in a 1.5-2% power difference? I chose high flow cats for a couple reasons: no black soot build up on my bumper, no smelly cold starts, and my Pride exhaust is already loud enough, if I went any louder I would have difficulty talking on the hands free setup in my car. I think you would be content with HFC but if you really want to push every last hp out I "assume" the test pipes might be better (citation needed).

 

[MileHighNSX]

I guess I didn't think of that about black soot building up on the bumper from test pipes? I wouldn't say that my current exhaust is loud, but I'm assuming even if I go with the HFC it would allow my current exhaust to be a little bit louder which would be welcome. Looks like I'm leaning towards the HFC again, just have to come up with that extra cash for those.

Kind of touching on the whole back pressure thing we were talking about above, did you notice anything about throttle response being less responsive after you put on the HFC and your Pride Exhaust (I'm assuming you have headers as well)?

 

[scammy]

I went through this a while back when I first installed my headers and exhaust about 10 years ago at first I deleted the cats and the exhaust was not only louder but had a blah sound to it when first accelerating away (sounded like crap) it also felt flat down low (no Dyno to back that up) so I then ordered some Python HFC and it improved the sound and initial throttle response so back pressure felt like it helped.
it also stopped the soot on the bumper.

 

[clr1024]

Interesting, ok so I will trade off a little throttle response due to the larger tubing like you said, but once the exhaust gas starts flowing then the car can breathe better with associated modifications. Is that why you see gains in the mid to upper part of the rev range due to the fact that the exhaust has filled the larger diameter tubing and is now flowing more free??

Pretty much!there's a bit more science to it, but that's the jist, you can play with tubing diameter to help enhance more mid vs high or vice a versa both come with pros and cons and a lot of it has to dowith how you drive your car, if you never wind her up, what's the point, other than sound.

- - - Updated - - -

I don't have a lot of soot on my bumper either and my car is way past due for a car wash. Could just be me, but that's my experience.

 

[MileHighNSX]

I went through this a while back when I first installed my headers and exhaust about 10 years ago at first I deleted the cats and the exhaust was not only louder but had a blah sound to it when first accelerating away (sounded like crap) it also felt flat down low (no Dyno to back that up) so I then ordered some Python HFC and it improved the sound and initial throttle response so back pressure felt like it helped.
it also stopped the soot on the bumper.

So in your case the back pressure loss of removing the cats did result in the throttle feeling flat down low. Question are the Python HFC and others being sold through the community now about the same as far as quality is concerned with 300 cell versions??

- - - Updated - - -

Pretty much!there's a bit more science to it, but that's the jist, you can play with tubing diameter to help enhance more mid vs high or vice a versa both come with pros and cons and a lot of it has to dowith how you drive your car, if you never wind her up, what's the point, other than sound.

- - - Updated - - -

I don't have a lot of soot on my bumper either and my car is way past due for a car wash. Could just be me, but that's my experience.

I feel ya about winding her up, I know I can go to certain spots where smokey isn't and I can let her rip when I drive, seems like I have to do that at least once a week to get my fix of VTEC! With regards to you not having a lot of soot on your bumper vs others that have RTP, maybe it's the gas or condition of the motor? Running rich? Maybe it varies from car to car and isn't that big of deal anyway with regards to that issue.

 

[robbiedawg]

angus (wil)makes very high quality high flow cats and rtp's. i am getting some of his 100 cell cats.he's been great about answering all my questions,and i have learned a lot.i had some similar questions about the differences,and in post #20 here he explains them:

http://www.nsxprime.com/forum/showt...X-NSX-Resonated-Test-Pipes-and-High-Flow-Cats

he owns an nsx and works on lots of them,and is very familiar with our cars.he's a great guy,and i have enjoyed dealing with him.i didn't want a super-loud sound,but wanted a better flow,so that's why i chose the cats over the rtp's.

 

[MileHighNSX]

Thanks for the link to that thread it did answer some of my questions:eagerness:

 

[scammy]

So in your case the back pressure loss of removing the cats did result in the throttle feeling flat down low. Question are the Python HFC and others being sold through the community now about the same as far as quality is concerned with 300 cell versions??

- - - Updated - - -



I feel ya about winding her up, I know I can go to certain spots where smokey isn't and I can let her rip when I drive, seems like I have to do that at least once a week to get my fix of VTEC! With regards to you not having a lot of soot on your bumper vs others that have RTP, maybe it's the gas or condition of the motor? Running rich? Maybe it varies from car to car and isn't that big of deal anyway with regards to that issue.

yes flat down low without cats, with cats seemed way better and sounded better down low. If you were hard up it at the track it didn't make any difference, and my car is running a bit rich but even if it wasn't i think without cats you will get some soot on the rear bumper

 

[davidf]

I'm running 200 cells and get zero smell {even up close} and no soot.

 

[Pappadaddio]

Long time listener, first time caller. For the purpose of this conversation, I will be replacing the words "backpressure" and "turbo" with "buttfissure" and "furby".

some buttfissure is good for throttle response and I don't doubt that, so if I go with either the HFC or the RTP will I lose some of the buttfissure that I currently have due to enlarging the diameter of the exhaust system all the way through??

Let me put it to you like this: Closing the air valve into the pump reduces power. So why would closing the valve on the exit increase power¿?

It's about scavenging cylinders and constant flow. That's why twin-scroll furbys and twin furby systems exist. Buttfissure only comes into play on the hot side of a furby when/if you want it to spool more quickly (power adder).

Thank you and good night.