In my findings on the dyno,I picked up alot of HP and TQ going from my old Cargraphics with your 100 cell cats to my current 100 cell Milltek using the standard tips on both,, which both systems were piped down at the end to except the stock tips?? Thats when I picked boost up and needed an extra fuel pump with the Milltek..I wrote a thread on it..
So,I believe there is more to the WHOLE exhaust piping then the end tips being piped down because of my experience...

 

John, that is what we found using the same systems on the same day in direct comparisons with just tip changes - everything was constant except the tips. Your testing is with completely different muffler designs and IMO, the difference was most likely in the OVERALL exhaust design, not just due to the pipe size of one vs. the other. With those variables in play, it is hard to be certain why your results were what they were. Also, if the tests were on different days, then it's not really accurate either.

As a side note, I have never heard of picking up so much boost with just an exhaust swap (of any kind) that you required a second fuel pump just because of an exhaust change, especially when both were aftermarket hi-flow exhausts.

Anyhow, I reported our findings and I feel very confident of our data on the effect of outlet size on exhaust performance with all other parameters remaining constant.

 

Here are some pics of my friend's exhaust. Work of art!

 

Gorgeous exhaust, but what's with the badging on your friend's car?

 

http://s799.photobucket.com/albums/y...t=1cfaebc6.mp4

 

Ya I don't like it either..... But whatever it's his car.

 

John,Not to disagree with your opinion,you have alot more experience and knowledge with these cars then I do or ever will have..
But it did go up .15 bars and Tony (EPL) data logged after that when it was on the dyno and the fuel pump couldnt supply enough to the injectors..I wrote a thread on that also.Prior to that he dynoed my car at his shop with the Cargraphics exhaust...
I measured the inner pipings on both exhausts..Cargraphic had 2.375'' inner piping going into around a 2.125'' sharp bend to the tips..Milltek has 2.75'' inner piping going into a 2.5'' smooth radius bend to the downsized end to fit the tips.
Believe me I had to pay alot for dynoing,fuel pump addition and ended a relationship over that exhaust swap BUT at least I got more power..LOL..

 

Sounds like the Cargraphic was very restrictive by design. Now, let's get this thread back to ek9max's exhaust - you can email me if you want to discuss this further and I'll be happy to share what I learned...

 

HI, Agreed...

 

So the 2.5" is a restriction even on stock turbo cars?
I suspect that the 3" would make a tiny bit more up top on modded cars as mentioned, but would also guess you could not feel it.

 

My car dynoed over 700 whp with a switzer 70mm exhaust. I do not see the need for a 3". I have billet 20g's.

 

HI,Cat Or Catless??..Stock TB/Plenum....Thanks..

 

catless,upgraded plenum & throttle body,dual fuel pumps,60 lb injectors,protomotive tuning,turbo piping,BBI coil packs,stock y pipe & air filter box.etc,etc......

 

How long will the drive train take that sort of power? The 600whp mark seems common enough, but is 700 getting close to issues? Impressive, to say the least! Must be a blast.

 

Thats great...Was that on straight pump gas?.....One day I would like to see what K24/20's would do on my package only staying on pump gas like I run my K24/18's on..