capt. bill1

OK, here's the deal. I had my back pressure tested with a DP, N-Tech high flow cat and an PFS cat back. 7 LB. Not good. So I'm going to try a resinated MP. Not sure if I want may CMY 7 to be as load as most MP cars are. Cops take long looks as it is.

First, who has resonated MP besides Pettit?

Second, I would like to remeasure my back pressure with my current set up, then measure it with a MP and finally with the resonated MP. I would post the results on the board for all to see. What I need is an old MP. I would be willing to pay for one if the price is real cheap. But I am hoping someone has an old but usable non stainless one they might be willing to let me have for shipping only to further the cause of getting some real world numbers on these different exhaust setups.
Any takers?

capt. bill1

So, does anybody know who else sells resonated MPs besides Pettit?
Nothing against Pettit. Just want to price check.

Want2race

i believe shane racing does!

Pressurized

I thought Jason used to sell them from the rx7store? They usually go for $350...and that's the same thing I did. I went from the Ntech to the Pettit resonated and I truthfully couldn't tell much difference in sound or performance. Although I would say that the car pulled significantly better towrads redline with the MP....

jimlab

Don't waste your time on a resonated midpipe. Based on experience, it's not worth the effort.

Look into having a Borla XR-1 stainless muffler welded into a standard stainless midpipe and you'll have a reduction of sound level without significant additional backpressure.

capt. bill1

Pressurised, Thanks for the info.

jimlab, Did the resonated MP just not reduce the sound to your liking? Or did it have other problems? And did you do a back pressure test on the Borla?

jimlab

The resonated midpipe from Pettit has almost no affect on sound level. It's basically the same as a standard midpipe, for a lot more money.

I chose to put the Borla in the midpipe after talking with Brian Richards (Mostly Mazda/M2 Performance) about his track cars. He runs the Borla XR-1s and swears by them for noise level reduction while keeping exhaust velocity high and back pressure low.

Bottom line is, the resonated midpipe doesn't work. If you want something that flows better than a high-flow cat and knocks the sound down, then the Borla is your answer.

Tim Benton

iTrader: (1)

I'll have to respectfully disagree with Jim on this one. The resonated midpipe I purchased from SR and installed does indeed flow better than a hi-flo cat, so it obviously is an upgrade that flows nicely. Nicer than the borla muffler welded into a mid-pipe, I don't know, but I do have dyno proof comparing my car with the hi-flo cat and the only change being the resonated mid-pipe. It makes a big difference at the top end when you want the exhaust to be flowing lots of air.
So indeed it does work better than a hi-flo cat and also knocks some of the noise of a standard MP. On the noise level, friend here has the same exhaust setup as mine, except he has a MP, to my resonated MP, and his car running the same boost is louder than mine.

Tim Benton

jimlab

Tim, I think you misread or misunderstood.

Here we see that resonated midpipe = standard midpipe + $$$.

And here we see that standard midpipe + Borla = better flow than a high flow cat.

At no time did I say that the resonated midpipe was more restrictive than a high-flow cat. It is my experience, however, that it does almost nothing to lower sound level, and is not worth the money if that's your goal.

The Borla is a better choice for someone who wants to quiet the exhaust without introducing excessive backpressure. Look through the Borla... you can see straight through. Look through a high flow cat... see the grid of the catalyst brick? Which has less backpressure? Borla.

Tim Benton

iTrader: (1)

I see your point now, I just misunderstood the last sentence..
"Bottom line is, the resonated midpipe doesn't work. If you want something that flows better than a high-flow cat and knocks the sound down, then the Borla is your answer."
I misread it and thought you meant it (resonated MP) wasn't worth it compared flow-wise and noise-wise to a hi-flo cat, but you were referring to the MP/borla setup in noise, flow and cost.

Tim Benton

jimlab

Yep.

I agree, the resonated midpipe is a definite flow advantage over a high-flow cat. I've tried the Random Tech. high-flow cat, the Pettit resonated mid-pipe, a straight Tri-Point stainless midpipe, and the Tri-Point with a Borla in the center, and was most happy with the performance and noise level of the Borla setup, because emissions wasn't an issue for me.

capt. bill1

Thanks for all the info guys. I thing I'll get a SS MP and add a Borla to it. Here's another couple of questions while we're at it. How loud do you think an exhaust would be with just a MP with Borla in it and straight CAT back with no muffler? Or how about two Borlas and no muffler? Seems like you might keep the sound in check and get full flow with that last set up.

jimlab

Borla claims an 8 dB drop for each XR-1, and Brian Richards said that he ran 3 in series on his road race cars. I doubt one would do the trick all by itself, but you could try two.

I ran a PFS single cat-back and then the Racing Beat twin tip behind my Borla and it had an exceptionally good sounding idle, very livable, even though the car was full non-sequential. I replaced the PFS because it droned at highway speed, which was not a fault of anything but the muffler. With the RB twin tip, the car was quiet when it needed to be, but damn loud at WOT, which you'd expect from a non-sequential rotary engine.

I'd recommend using another muffler behind the Borla, or 2 (or more) Borla mufflers in series.