So several months ago Tim and I were working on my car and at about 1am he said lets get rid of your X-flow exhaust. I said no it sounds great . He said - "how about this: we put a boost tap before the X and take the car out on low boost 22psi. if the car has more then 1psi backpressure we are cutting it off". I said OK. Half hour later we had the boost bong welded up and ran a metal tube and then vacuum line to the boost gauge inside the car, we had another boost gauge showing actual boost.

Results: at 22psi of boost there was 6psi of backpressure before the X section. we cut the exhaust off.

Interestingly enough I came across a good read on a test done independantly of what Tim and I did by the guys over at AMS and a popular X pipe exhaust here. AMS doesn't make an exhaust for 996 or 997 so they have no horse in the exhaust race.

http://truth.amsperformance.com/

... and now my car sounds like this...

just thought i would share...

 

Just read the AMS link you posted. Funny how they don't mention who makes this "horrible" exhaust that has cracked welds and broken $65 cats after one run on the dyno but they go and show a close up of Marek's 911Tuning name plate on it. I've always heard nothing but high praise for his stuff so this is a bit suspect. Oh, and the exhaust robs you of 70-90hp compared to the AWE. Hmmmm... I suspect they make a good margin reselling the AWE stuff.

 

But what did you have built? Did you want it very quiet? With 200 or 100 cell cats??

 

o lawdy.....grabbin my popcorn now. this should be a good one.

 

i could care less. i know what i know because i tested it on my own car and saw the numbers. my car sounded much better with my X but it was holding me back so it had to go.

and honestly i REALLY doubt that AMS even cares about selling AWE exhausts period, they make their money selling big power GTR builds now a days.

i liked the test AMS has done for our platfrom in the past on the fuel pumps... where they also didnt sell any fuel pumps for the 996tt.

for now i have straight pipes, but i am going to try to quiet it down without losing too much and creating back pressure.

 

tim told me about this when he made my x-flow exhaust.
flows perfectly. Tim, can you chime in ?

 

we tested it ourselves after he made your exhaust. your car has K24s on it and it maybe sufficient for them and the power level..

 

Mark,

The client wanted a quiet 2.5" exhaust including all the piping from the cats and to the tips... also 2.5" ID of mufflers... not to mention with 100 cell cats.... thats probably good for upper 500s to the wheels...
With that said, AMS put on A28s and turned up the car to as you say 22 PSI... Had I known that I would never sell that exhaust to the client.... Not to mention the cat cores got dislodged from the inside probably due to HIGH heat caused by un burt fuel from tuning the car ....( verified with the cat manufacturer). Now , the car was just dynoed from my understanding... and this is what I got back- Yet I gave a full refund... you tell me if a handful of pulls will do that any exhaust? including yours ?
Had I known I would tell him he needs a full 3" catless... but the client didn't want it... wrong exhaust for the application was the case...
AS far as making power... the X we make does make 900 whp incl. our own 997.. no gimmicks no magic... sure a straight pipe will do better but thats not what we are saying nor comparing too... The AWE exhaust is all piping with one small muffler in middle.. The owner did not want a loud version which is why he opted for a quiet one with small ID piping and ID mufflers... I could have made a free flowing one no problem.
There are a few members making 700whp at 1.5 bar catless 3"... and this is our 997 with TIAL 30rs NOT 28s making power... 870 and look at the TQ








This is what I received back...

 

I would imagine that the x-flow design would be contributing to the backpressure along the same lines as an external wastegate dump being recirculated into the exhayst. The competing air flow it seems, would add to the backpressure and be robbing of some HP for sure. I'm curious to see however, if it is possible to fab a system that is as quiet as some of the x-flow designs, without using the x.

James

 

no the testing we did was on my car which was done independently from AMS and has nothing to do with your exhaust. i do not know what boost they ran etc... i do know they switched your 2.5 for the AWE 2.5 so its not like they went from 2.5 to 3 and then started screaming "heyyyy we found 60whp"

mine had no cats or mufflers, so nothing to fall apart really. not sure what happenned there.

i believe you. the X I had made over 900whp on a dynojet as well and not a hub dyno. however we found that it was creating 6psi of back pressure in the exhaust before the X at 22 psi of manifold pressure (boost). very simple test. so we cut it off because it was holding me back from making more power

 

Wow..this is going to be a good thread..
I believe that the way that an X-pipe merge would be the best,at least in theory, would be to have the both sides do a complete 180 bend and then have a common window/chamber connection between the two..
Matter a fact I might be getting a 2.75 X- pipe like that to compare on the dyno against my Milltek in which I modified it to be a 2.75 system also?

 

Do you have any other numbers like that from other exhausts to get a thought of how bad or good that 6 is in relationship to another type?
Did you think about checking the pressure After the X ?
If I may ask,was that an EB Werks pipe? Their merge does look like it has enough volume and nice bends.
Thanks

 

Interesting. Mine makes good power. Heck great power. I have 100 cell cats and the tune was perfect. Can't say we know the truth about what's happened at AMS. Did they run C16 in it and kill the cats? I have 911's X pipe on my car and it made 3hp less then straight pipes I will take that over a headache any day. Let the truth really be told!

Oh and BTW if anyone doesn't believe me they can come here or call the shop that I bring the parts to and ask them what's on the car. What has been on the car. And what ever they want.

 

Its so funny that today I did call AMS and ask them if I could do a few Dyno pulls with my car AND then swap exhausts there or have them do it there,,And then put it back on the Dyno to compare..
I told them what exhaust I was running and I wanted to try it against an X-pipe that I might be getting...
They said no,,they are booked on the dyno with no foreseeable openings..
REALLY this did happen just before this thread..

 

So choking the turbos with 2.5 in exhaust with cats steal some power WOW!!! Please everyone now that you need 3 in and cat less exhaust to make big power. Mark do awesome products, if only the owner follow his advice that problem will not happened. I have bought AMS intercoolers before for my 335 tt and the 4.5 in intercoolers that Mark sold me are light years above them on craft matching!!! I said these because is not fair to criticize other product in the way that AMS did!!!!