Power output for various exhausts

PeteK · Aug 20, 2014

Dear denizens of the Forum: I've fished around in the archives for this information, but it does not seem to succumb readily to my queries. I would like to know if anyone has measured the before and after HP and torque of different exhaust system changes. Not the sounds (yes, there's the excellent sticky with the sound files, and I think they would benefit greatly from being played back on the FGT MacIntosh, rather than my Apple MacIntosh), but the numbers behind the soundtracks.

I hope some of you with the data will post the HP and torque curves or tables for your cars before you made an exhaust system change, and after, with no other simultaneous changes. Yeah you would have to be pretty mechanically anally retentive to dyno the car several times as you make changes, but I'm hoping one or more of you are kinda like me in that department.

An example of this data would be the data of a dyno run before the FRPP/Borla muffler is installed, and immediately after, on the same dyno, and preferably on the same day. Is there any performance difference? Another example would be the data from changing from stock to a header exhaust system.

Given my past experience with engines and modifications, I suspect that the performance differences are pretty small, if any, for the FRPP muffler or the X-pipe, and probably not significant even for the long header system. I suspect this because with supercharging on the intake side, the efficiency of the exhaust in extracting all burned gases is not as great as in a non-supercharged engine. However, since the long header system eliminates the cats, I would expect to see more effect on performance, but probably not a big difference.

I'd love to be proven wrong (which would give me an excuse to buy a Borla muffler or even headers), so let's collect all the data we have and publish it here for future reference.

We could also add data on other changes, such as modified tuning tables.

Torrie and GT Guys, if you're reading this message, please jump in, as your experience tuning these cars has given you a lot of insight and experience with what changes have what effects.

I will be happy to collect everyone's inputs and assemble them into some consolidated table for the moderators to post as a sticky.

Thanks in advance, Pete K

Fast Freddy · Aug 20, 2014

after 35 years of racing and hot rodding, exhaust is all about the sound to me now. which means louder is better. there are other ways to make more power like TT's but you don't get the sound i get with my Borla Headers, no cats and Borla race muffler. i figure it makes 50 more HP at the crank than stock based on dyno data that i have conducted on my car with various exhaust combo's. look at the factory collector size on the stock exhaust manifold and you will see the biggest source of the problem imo.

Note: my data applies to a car with a 4.0L Whipple suckin 22 lbs. of boost like mine does on the dyno. at speed it might be more but then i have cut holes in my airbox so i doubt it....

fjpikul · Aug 20, 2014

Pete, you won't find it casue no one has really done it. The effects are negligable. THE big savings is heat in the engine bay. Watch out for drone at 2K rpm.

Fast Freddy · Aug 20, 2014

^^^^ - you can add weight savings to that list....

nota4re · Aug 20, 2014

Going to be a lot of subjective feedback here because there are very few if any genuine back to back comparisons isolating just an exhaust change. With only a couple hundred hours of dyno time with GTs, my input would be the following;

a. Borla - virtually the same as OEM from a HP/TQ perspective.
b. H-pipe or Plus-pipe (intersecting exhaust bank output at 90-degree angle) exhaust maybe a just measureable improvement over OEM/Borla
c. X-pipe designs - fractionally better improvement over the above systems

d. Headers w/x-pipe - more significant improvement. Whereas above difference are in the 1-10 HP (MAX) difference, headers can give 20-30HP
e. Headers with no cats and no or minimal muflers - 20-40HP improvement over OEM

Guesstimates above assuming car with pulley/tune set-up. Cars with Whipples and turbos would likely see bigger gains from these exhaust mods.

RALPHIE · Aug 20, 2014

nota4re said:
...Cars with Whipples and turbos would likely see bigger gains from these exhaust mods.

That's interesting - my gut feel would have been that bigger superchargers with higher boost levels would further minimize the effects of exhaust management. I learn something everyday - thanks!

BAT · Aug 20, 2014

Fast Freddy said:
^^^^ - you can add weight savings to that list....

Like you, I have the Borla headers an exhaust. What is the weight savings with this combo? Just curious....

Xcentric · Aug 20, 2014

BAT said:
Like you, I have the Borla headers an exhaust. What is the weight savings with this combo? Just curious....

I'm too lazy right now to haul a scale down the driveway. I have Borla long tube headers and muffler and the original parts in the steel building, including a cracked 1st gen Borla.

I'd ballpark the Borla muffler as about 20 lbs less than stock. And about the same for the Borla headers vs. cast iron manifolds and cats.

Bumper delete saves about 25 lbs too I'd say...bumper and frame horn extensions.

Just guesses based on muscle memory. I'll weigh them when it's not 95 degrees.

If anybody is handy with welding stainless, I'll sell the old Borla as a restoration project. Heck, I'll sell the stock muffler too.

BTW, I don't feel any seat of the pants performance gain from the long tube headers with 16 psi pulley/tune. It sure sounds a lot faster though!

SteveA · Aug 21, 2014

I tested the stock exhaust, then a Borla, a X-pipe, straight pipes (no Cats) into stock, straight pipes into a X-pipe and lastly straight pipes into a Borla. The Borla over stock was not measurable, the X pipe over Borla was at most 10hp, the straight pipes (no cats) into stock or Borla was about 8 to 10 hp gain however the X pipe and no cats was only about 10 to 12hp gain. Our conclusion was really Ford did their homework on the performance of the exhaust. The only real change was the sound.

Xcentric · Aug 21, 2014

SteveA said:
Our conclusion was really Ford did their homework on the performance of the exhaust. The only real change was the sound.

+1. And looks.

Sinovac · Aug 21, 2014

BAT said:
Like you, I have the Borla headers an exhaust. What is the weight savings with this combo? Just curious....

Roughly 43lbs

http://www.fordgtforum.com/forums/s...ust-components?highlight=Exhaust+installation

PeteK · Aug 21, 2014

SteveA said:
I tested the stock exhaust, then a Borla, a X-pipe, straight pipes (no Cats) into stock, straight pipes into a X-pipe and lastly straight pipes into a Borla. The Borla over stock was not measurable, the X pipe over Borla was at most 10hp, the straight pipes (no cats) into stock or Borla was about 8 to 10 hp gain however the X pipe and no cats was only about 10 to 12hp gain. Our conclusion was really Ford did their homework on the performance of the exhaust. The only real change was the sound.

Steve, that's the kind of feedback I'm looking for. And about what I suspected. Dyno curves would be nice too, if you happen to have them.

SteveA · Aug 21, 2014

Pete, I didn't even take them home from the dyno shop (except the best one) because they were all basically the same. I could try and contact the So Cal dyno shop that did all the pulls if it's important to you. These were done in early '06 so I have no idea if they are still on his hard drive.

Xcentric · Aug 21, 2014

Sinovac said:
Roughly 43lbs

http://www.fordgtforum.com/forums/s...ust-components?highlight=Exhaust+installation

I'm glad your OCD beat my OCD.

Sinovac · Aug 21, 2014

Xcentric said:
I'm glad your OCD beat my OCD.

Let's be honest. Nothing beats your OCD. :lol

SteveA · Aug 21, 2014

My wife says I have "CDO". It's the same basic thing as "OCD" but the letters are in the correct order.....as they should be.

PeteK · Aug 22, 2014

SteveA said:
Pete, I didn't even take them home from the dyno shop (except the best one) because they were all basically the same. I could try and contact the So Cal dyno shop that did all the pulls if it's important to you. These were done in early '06 so I have no idea if they are still on his hard drive.

Steve, if you don't have them, don't spend a lot of time trying to get them. I just wanted to get actual data posted on this thread for everyone's future reference.

Indy GT · Aug 22, 2014

Pete, you are correct with your assessment below-

PeteK said:
Given my past experience with engines and modifications, I suspect that the performance differences are pretty small, if any, for the FRPP muffler or the X-pipe, and probably not significant even for the long header system. I suspect this because with supercharging on the intake side, the efficiency of the exhaust in extracting all burned gases is not as great as in a non-supercharged engine. However, since the long header system eliminates the cats, I would expect to see more effect on performance, but probably not a big difference.

As “typical” an exhaust manifold system as Ford developed for our car given the packaging constraints, the system does flow very well with little back pressure. Then too, as you correctly identify, with a Forced Induction engine, acoustic combustion chamber scavenging due to pressure pulses in an exhaust system are not as effective as in a normally aspirated engine. No doubt, headers look cool and do add a pleasurable exhaust note to our car, but if you are looking for meaningful power gains, there are other changes which provide more bang for your modification buck.

Steve summed it up pretty well-

SteveA said:
Our conclusion was really Ford did their homework on the performance of the exhaust. The only real change was the sound.

PeteK · Aug 23, 2014

Can the moderators turn this into a sticky, or should we let it run a little longer to get more comments?

SMOKDU · Aug 23, 2014

Indy GT said:
Pete, you are correct with your assessment below-

As “typical” an exhaust manifold system as Ford developed for our car given the packaging constraints, the system does flow very well with little back pressure. Then too, as you correctly identify, with a Forced Induction engine, acoustic combustion chamber scavenging due to pressure pulses in an exhaust system are not as effective as in a normally aspirated engine. No doubt, headers look cool and do add a pleasurable exhaust note to our car, but if you are looking for meaningful power gains, there are other changes which provide more bang for your modification buck.

Steve summed it up pretty well-

Dan S and i just 3 days ago added headers and took off my borla catless system and it added about 40hp. Same dyno same day. Then we added E85 and an over drive crank 2 degrees of timing and made another 60 hp. With a bigger blower you need btter flowing exhaust . Bottom line is on a stock blower and stock boost you will see little gains but with more CFMs you need a better axhuast. We proved it .

Power output for various exhausts

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