Chris,
I agree that long tubes help, but your post only shows that the headers AND the high-flow cats/H-pipe made more power. If you really wanted to show that headers alone make more power, you would have had to run the stock midpipe, or at least the stock cats. So you might want to get off your high horse about the power gains coming SOLELY from the headers, and maybe jump onto a slightly shorter horse.
Its nearly impossoble to run the stock cats and stock mid pipe with long tube headers. That would require some custom work including cutting off the stock cats and rewelding them in at an odd angle. The stock cats are higher up than the collectors of the long tube headers.
Again, I agree that long tubes help make more power, but I do agree with a lot of people that deleting the restriction of the stock cats is also responsible for some of that power.
It doesn't seem that replacing the stock cats with ones that flow better gives much of a power gain at all based on dyno results posted here and other places. To me it seems that replacing the stock cats with a higher flow version might get you 2 HP at the most when looking at the dyno results before and after the stock H pipe and a catted aftermarket H pipe.
I've seen the dyno results before and after the Mac pro chamber with and without cats. At one point, I was considering getting JBA equal length shorties and the catted Pro Chamber for emissions reasons, but they stopped production of the catted pro chamber for the S197 and I could't find it anywhere. The difference in SAE corrected dyno results with the catted and catless pro chamber seems to be around 3-4 HP on two cars with the same mods(same intake, same canned tune from the intake manfacturer) other than the catted or catless pro chamber.
Its harder to compare corrected power results of other cars because there are variations from the factory. My results were 311 HP and 325 ft-lbs using STD correction and 302 HP and 316 ft-lbs using SAE correction. However, if we do look at corrected results, this is what I found:
- I found another s197 with a custom 93 octane tune, CAI, and Bassani exhaust with off road X pipe. Its SAE results were about 10 HP at the wheels less than mine peak and it looked like it lost power in the upper RPM range faster than my car did.
- I also found a dyno of another S197 Mustang with a CAI, tune, offroad H pipe, and axle back exhaust. Its SAE and STD dyno results on a dynojet were more than 10 HP less at the wheels than my results with the same correction factors.
- Another one I found is a S197 with FRPP shorty headers, off road H pipe, CAI, and 91 octane tune. Its SAE corrected dyno results were 11 HP at the wheels less than my SAE corrected results.
- There is another I found with a CAI, 91 octane tune, stock exhaust manifolds, a Bassani X pipe with high flow cats, and cat back exhaust. Its SAE dyno results was 292 HP at the wheels. After the installation of the Steeda UDP kit, it gained 8 HP peak at the wheels peak to bring it up to 298 HP. I have the stock crank and accessory pulley on my car. So it made 10 HP less at the wheels with the CAI, tune, offroad X pipe with high flow cats, and cat back exhaust.
- I found another with the JBA shorties, Pypes offroad X pipe, JLT CAI, Bamachips 93 octane tune, CMCV deletes, and Steeda UDP's. Its SAE corrected results were 296-298 HP at the wheels on multiple dyno pulls. That's with CMCV deleteds and Steeda UDP's, neither of which my car has. The addition of both the CMCV deletes and the Steeda UDP set is good for 10 HP or more depending on who's results you look at.
- I found another dyno that showed the before and after results of CMCV deletes, Steeda UDP set and a Bassani offroad X pipe with stock maifolds. The results with the other mods before the CMCV deletes, Steeda UDP set and a Bassani offroad X pipe were 289 HP. The results after the CMCV deletes, Steeda UDP set and a Bassani offroad X pipe and custom tune were 304 HP. Both were on the same dyno. Considering the CMCV deletes and UDP's were installed at the same time, as the offroad X pipe the offroad X pipe looks like its good for only a few horsepower.
Getting rid of the stock cats and replacing them with high flow cats and an aftermarket H pipe doesn't seem to do much for power gains. If you have multiple results that show otherwise, I'd like to see them.
It looks like I can't find a single dyno of a S197 Mustang GT with an offroad X or H pipe and stock manifolds or shorty headers that has similar other mods as mine that can produce anywhere near the horsepower HP of what my SAE or STD corrected results are and I have cats and an H pipe. The difference between the Kooks long tube headers on the same car with and without the high flow cats is also about 5 to 8 HP at the wheels on naturally aspirated S197 GT's depending on who's results you look at.
Based on the dyno results of other cars, if I were to compare apples to appes with the cars that have no cats to just see the effects of the headers alone when comapred to stock manfiolds and no cats, then my results would be even higher.
Agreed! the sound has some crazy effects on you (or it did with me) and in all honesty... ALMOST 16hp gain isnt that much for spending $1300 on a lt and high flow cats. yes you will feel a difference, no there are not that big of gains on the dyno (i have seen better on other cars but will not say which ones), BUT its not the dyno that matters anyways, its how much faster you will run at the track.. so have fun with the new setup
I got in on a group buy with the Kooks headers and my price shipped to my door was much less than that. If I went without the cats I could have saved another $100 and gained more power. It ended up being not all that much more costly when compared to getting the JBA equal length shorties and a good quality catted H pipe or getting high flow cats installed into an off road pro chamber, which was the setup I was originally looking at for emissions and sound reasons.
Looking at other people's results and talking with a shop owner that has done multiple installs of the Kooks headers on S197's with and without cats, it seems that if I went without the high flow cats, I probably would see at least another 5 HP at the wheels, maybe more. Also, the power gains from headers depends on what other modificatiosn you have. Anything you do on the intake side to increase air flow before you install the headers could give you bigger gains after the install. A custom tune after the headers could also increase the power too.
Who ever would actually believe LT's don't do anything, just don't know.
