Someone told me it is better to use the Magnaflow X-pipe Section in place of the Cats instead of using them in the H-pipe location? "The Closer to the headers the better" Is this ture? I already have straight pipes in place of the cats, is it better just to buy a $70 x-pipe section and put it there, or buy the entire x-pipe section that puts it closer to the mufflers.

 

Well the question I would first ask is do you have a DEQ test required for your car. If so then leave the cats on. The engine management system is designed to have them in place and if you are looking to maxzimize HP this is not the way to do it. There are many other options for that. I have a Mangaflow and it works quite well installed as designed. If you cut off the cats I am not sure the Magnaflow would fit although seems like it might. The engineers spend a lot of time to make these things right and I am not inclined to screw with success.

 

you need the cats .. you've already got a VERY free flowing exhaust ..

i have the straights & Magnaflow X myself and I found once i added the x i lost power in the lower range .. i imagine the cats add a tad bit of backpressure so cutting them off would be a bad idea.

but hey, it's your car .. enjoy.

 

Yes, closer to the headers is better.

 

no flames, but i don't know if that's totally true. i thought i read somewhere how to determine the ideal spot for a crossover pipe (h-pipe, x-pipe). as i remember, it said to spray some a light coating of paint on the exhaust pipes, and run the engine. the point where the paint first starts to burn off is the spot where you need to install the crossover pipe. i dont remember all the specifics, but that's it in a nutshell.

 

I guess I should have mentioned that I have 530 RWHP so I dont need or want cats. Emission testing is also not an issue, got that covered.
Yes it is true about painting your pipes and check where it burns 1st, that is done on a full track pass.
Thanks

 

LG motrsports use to put the X right after the headers. I think the only reason they moved the cats forward was to keep them hotter to pass emissions. My Kooks headers and offroad system also has the xpipe right after the headers where the cats would normaly be...

 

I found a post I had some time ago on an article on X-pipes contained in the June, 2001, issue of Hot Rod Magazine. if you can find a copy of the article (maybe Hot Rod has it in their archives?) I believe it would answer your question in fairly significant detail. Basically, here is a synopsis of the article:
They discussed how an X-pipe works, then ran a car on a dyno, and the strip with:
1) open headers
2) mufflers & pipes w/o a crossover
3) mufflers and pipes with an H-pipe
4) mufflers and pipes with an X-pipe.
These are the results:
a) Test Vehicle / 1970 Olds 4-4-2 w/350 block and modified
b) Where first seen / NASCAR guys began using X-pipes
c) X-pipe design theory - "By running the two exhaust pipes together in this fashion, the alternating pulses in each bank can work to create the same type of scavenging action in the other."
d) Works best on a V8 engine running 300-500 hp because the volumetric efficiency is not as great as on a 700-800 hp V8 engine.
e) Dyno pulls:
1) Open header
430 hp @6850 rpm, 384 lb-ft @5600 rpm
2) 3" exhaust pipes w/Straightline mufflers and no crossover
412 hp @6650 rpm, 371 lb-ft @5600 rpm
3) Same setup as #2 except with an H-pipe
419 hp @6600 rpm, 378 lb-ft @5600 rpm
4) Same setup as #2 except with an X-pipe
428 hp @6600 rpm, 391 lb-ft @5600 rpm
Strip tests:
1) Open header
1.65 sec 60', 10.885 sec @123.89 mph
2) No run with the exhaust system w/o a crossover
3) Exhaust system w/Straightlines and full pipes and an H-pipe
1.55 sec 60', 11.007 sec @121.33 mph
4) Exhaust system w/Straightlines and full pipes and an X-pipe
1.62 sec 60', 10.897 sec @124.13 mph
This car, which used to run open headers at the strip, now runs with a dual exhaust system with an X-pipe. More details in the magazine, naturally, but very interesting, I thought.
And yes, the article discussed mounting the X-pipe far forward in the car, just after the headers, to maximize scavenging.
Maybe more than you wanted, but a great article.
Ed