Darien

Very Nice

ErnestSw

I've got Carl's X pipe, low restriction cats, GT resonators and an RMB. My dyno runs with and without the cats and with and without the RMB show no measurable difference in performance. Since I already have the stock 2.25" cat back system I'm assuming that there would be no benefit in changing the cat back system. I'm making 310 HP at the rear wheels with stock fuel pressure and I ASSUME that I'm getting near the limit of the stock setup. As far as I'm concerned any exhaust system that doesn't increase flow enough to require me to add fuel pressure is a waste of money.
I invite comment/correction/education.

the flyin' scotsman

The exhaust system only increases flow at one end; while there's no doubt there's hp to be had with a X etc but I wonder about the other end. Open up the air box, get more, cooler air but then you may need more fuel............etc etc etc

Its all a fine balance.

ErnestSw

Malcom,
You're restating what I said. If the exhaust system does not increase flow it will not allow for an increase in air through the engine, The stock intake is capable of a lot more air flow than my current exhaust system. The only reason I installed a variable fuel pressure regulator was in anticipation of a freer flowing exhaust increasing intake flow and needing more fuel. I'm not understanding how a 2.25" exhaust will do this.

the flyin' scotsman

I wasn't aware of that fact; so the original design is heavy exhaust restrictive.

I find the Motorsport X to be very free flowing compared to the stock Cats but perhaps mine were plugged. I also added the AFPR and consider it somewhat of a waste with the stock set up.

I'm hopeful of using another Listers shark tuner to tweek the LH more precisely.

ErnestSw

The LH adjusts the fuel flow to the amount of air seen by the MAF. The stock MAF will work up to about 450HP IIRC. That's a lot more air and fuel than the stock exhaust system or the stock fuel pressure regulator can handle.

fabric

If you needed to replace your stock cat-back exhaust system due to corrosion or whatever, how much would a stock system cost? I'm guessing it's not much more to replace with this all stainless system, which will probably outlive the car. Considering how long your stock system has laster, maybe that's not really a concern.

Also, this has something more along the lines of the early S4 resonators, vs your GT sized ones.

SO there's some reasons other than performance that I would think make this a good option if you *need* to replace your system.

Carl Fausett

Fortunately, I took the 1985 test-mule to the dyno to get a base-line already. After this low-restriction exhaust is installed, I'll go back to the same dyno and see what the results are.

I will also make an audio file so you can hear it.

Yes - Sterling is right - the OEM exhaust is non-corrosive material, so you will not be replacing it because its rusty.

But you might want to replace it because the mufflers on it are restrictive and these are less so, or you might want to replace it because you want to hear more bark at the tailpipe.

MarkRobinson

Factory 32v pipe is 2-1/8" (metric) if memory serves, so 2.25 is larger (Pi x Radius(squared) by a reasonable amount.

My tested 2.5" system added resonance & noise, lost some peak mid-range torque, & was generally not worth the extra pipe size. I *could* get dyno charts showing this if I were to visit the dyno & go through my many dynos, but don't feel very motivated to do so due to the weather.

Mark

MarkRobinson

(Peak HP was unchanged BTW)

Carl Fausett

Exactly. At first draft, I was going to produce a cat-back exhaust right to the tips. After further consideration, we decided to just produce the missing middle component that is not available from anybody anywhere for two reasons:

1) so you coulkd mix-and-match pieces to get the sound or meet the emissions standards you want, and
2) so we would not step on a product already manufactured (the RMB) by one of our suppliers.

I don't like stepping on those people who supply us - so this product dovetails with Motorsport's X-Pipe and makes use of 928 Intl's RMB - and may make more sales for both of them... but certainly will not take sales AWAY from them.

It's a missing after-market pipe. I had been looking at the "hole" in the exhaust product offerings for years and finally decided to do something about it.

Did you follow the link to Stebro?
www.stebro.com

They are first class - if they make aftermarket performance exhausts for Ferrari (and they do) you KNOW they're good. I am happy to have them on board as a supplier to us.

auzivision

Will this system allow the use of high flow cats or does it eliminated that option?

Carl Fausett

Absolutely. The high-flow cats are placed into the X-pipe, which is ahead of this. What we have designed for is maximum flexibility to the owner.

You could: keep stock front pipe and stock cats, and this install from Cat-back. You could use this with the after-market X-pipe and also fits up to the after-market hi-flow cats. You can use these with or without a RMB too.

This is a bolt-on for 1987-1994 Porsche 928 and fits 1995 with a small mod if needed.

Carl Fausett

I now need a 1987-1991 Porsche 928 to test-fit these on.

I do not have one here at the moment that I can do it to.

I believe there will be no fitment issues, the fit has been perfect so far on the '85 we just put them on. But I need to check.

If you are interested in a SS hi-flow set of intermediate mufflers and pipes for your 87-94, please contact me at 920-485-0488 or email me at carl@928motorsports.com

I'll provide a good discount for these new parts in exchange for you putting them on your 928, and sending me photos of them installed.

the flyin' scotsman

Carl........if distance and weather weren't issues I'd be right there. I'd like to try them with my X sans cats and a RMB.