Hollywood

I spent tonight planning my y pipe for my headers to cat back., since I am new to technical information for V8's over the big turbo 4 cyl I decided to do more research.

I have planned making the ypipe several times making slight variations and I have decided back to my original plan of running 2.5" pipes instead of 2.25. No cats w/o2 simulators.

This site has lots of info and dyno results using a v8 on all kinds of scenarios. Very informative. Seems like that 2.5" was the way to go though.

http://www.pypesexhaust.com/dynotests.html

Enjoy.

JBrady

Hollywood,

Do what you want but you are NOT comparing correctly with this site.

First of all it is a manufacturers site that is selling a product. Second the smallest engine listed is a 5.0 liter. The others are at least 5.7 liter and probably 389cid and 400cid engines. Third the "stock" systems may be standard 2.25" but were NOT mandrel and had smaller cross sections through mufflers and transitions. Again, they are comparing lousy old pipes and stock type mufflers to modern high flow pipes and mufflers. If they had compared modern 2.25" pipes the differences would be minimal with my guess being better mid range even with these LARGER engines.

Please also notice the engines shown made MORE power with pipes after the headers than open headers alone.

Our engines are small. 4.0 and 4.3 liter. Our cars are heavy. Why use a larger pipe that weighs more and is harder to package when smaller pipe works better?

Also, pipe diameter alone is the LEAST important consideration. Did you review this link?

http://www.popularhotrodding.com/eng...re/0505em_exh/

Hollywood

The last engine is a big hot rod motor, but still made under 300whp, which with various mods our GS's will be close to, The only reason open headers made less is because the car was not tuned for open headers, or the header was not designed to be an open header. None of those motors have the benifits of VVT-i. The website It's a general idea of V8's and exhaust info, I have not seen anyone else post much in the technical side of stuff like this, so I figure 10+ dyno'd configurations may be helpful to someone.

That header article is old school. Tuners of that era are behind in todays technologies. You ask those hot rod heads at mufller shops you want mandrel bent stainless, they start getting out the order books etc and quoting pricy numbers, as they live the life of crush bends, clamps, tapered piping, and maybe their own pipe bender for aluminized pipes, which is like a loss of 30%. No thanks. An import tuner shop will have stainless madrel piping 2.5-3" in stock! And cost 30-50% less.

Im not to worried, it will turn out fine. I just found out today I can get my ECU mod retuned on the dyno. So after I'm all done I will have tuned numbers to compare to others numbers.

Few questions for ya J. What size is the flange on the jbrady headers? What is the thickness of the header piping?

JBrady

Here is a more appropriate comparison dyno test to the Lexus engine. It shows a stock Cobra NA 320hp 4.6 liter 32v V8 that makes 272rwhp stock with 2.25" duals and cats. Trying both a 2.5" H-pipe and a 2.5" X-pipe both without cats showed dissapointing results. I think a well designed 2.25" system would pick up the low end as well as the top end. I still suggest that dual 2.5s are too large for our engines. I am contemplating dual 2.125" pipes with a new style merge of my design.

http://www.mustangexhaust.com/tech/HvsX/HvsX.htm

Hollywood

I think that's worse comparison cause of this;

Upon replacing the stock mufflers with some Magnaflow mufflers, their test Cobra gained almost 20 rwhp and adding a catted X-pipe yielded 1 additional rwhp (read the article here). It seems that on the 2001 Cobra the big restriction are the mufflers and not the stock H-pipe, and the results of this Tech Article and that of Hot Rodding magazine support that theory. Undoubtedly, with forced induction and better flowing mufflers the mid-pipes will show their true worth. We also want to point out that these results do not necessarily apply to all years and models of Mustangs as exhaust systems are periodically redesigned by Ford. Your results on your model Mustang may very well be different.

All there tests were using the stock cat back. Which was pointed out to be **** resulting in 20whp gain when swapped. The results would not be considered to be accurate till the rest of the exhaust was done IMO.

Also on the cobra the cat back is the limiting factor, on our cars its not the case as its the headers on our cars, so it's not a great comparison either.