worthwhile performance gains from 2.5" exhaust to 3"

[builttodrive]

My 07 Gt500 has been on the back burner for the last 4 years and I'm just starting to give it a little attention again. The rest of my mods are in my sig but for exhaust I have Dynatech long tube headers with Dynatech 2.5" off road X pipe, stock 2.5" pipe from there to Ford racing SVT1 (Borla Touring) mufflers. Would there be any real gains to be had to go to a 3" x and 3" all the way back to the mufflers?

 

[me32]

Not unless you are pushing the upper 700s, its its mostly for sound in the 600hp range.

 

[Islandcat]

Not unless you are pushing the upper 700s, its its mostly for sound in the 600hp range.

this is what I was basically told when I was researching the same question a couple years ago, so I just kept the stock 2.5 on mine.

 

[MG0h3]

Call ARH. When I asked about 2.5 vs 3 the tech kindof chucked. Said people have no idea what kind of power 2.5 will support


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[03SVT10]

What kind of power will 2.5 support?


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[builttodrive]

I’m sure the 2.5” can support more power but I was curious if the 3” would yield any decent gains. On the cars in our restoration shop I generally like the deeper sound of the 3” even though I know it’s not necessary on a lot of the cars. But then I’ve watched a 500 hp naturally aspirated car pick up between 2 and 3 tenths going from a high flow exhaust to simply opening up electric cutouts in the 1/4.

 

[PM-Performance]

It is just a tone change. The exhaust piping size thing has been debunked many of times on the internet

 

[Robert M]

My personal experience, not internet chat. I changed my 725 Super Snake from the oem 2.5" cat forward and Shelby installed Borla Touring 2.5" catback which was the 50 state legal set up that was standard install on a 2008 Super Snake, to the Shelby/JBA 3" mandrel bent manifold back exhaust system that was called the "Super Snake 700 optional exhaust" which was available years ago through Shelby Perf. Parts. I also installed a pair of ceramic FRPP shorty headers with the 3" and my 725 came alive. The difference in the engine rpm spin-up was noticeable, not that the 5.4 had problems spinning up with the 2.5", but the quickness of the spin-up was surprising. I also lost some boost with the 3" and mentioned that to Rick at Kenne Bell in a recent conversation, he said that was good (the loss of boost), boost is restriction, you lessened the restriction, that is why the engine is spinning up so much quicker than it was with the 2.5".

^^^^^Just my personal "installed" experience. The FRPP shorty's and 3" Shelby/JBA was louder than the oem manifolds, cats and Borla Touring and the first time I started the car after the exhaust change I was surprised the difference in tone and volume. I recently removed the Shelby/JBA 3" X-pipe and installed a 3" MAC Pro-Chamber, I can not say I noticed a large difference in that change, but the change for 2.5" to 3" along with the shorty's, THAT was a Big change in the way my car breaths.

The 3" MAC Pro-Chamber installed......

^^^^^ I can't say there was no gain with the MAC PC, I have not driven my car much since that install.....

The "manifold back" 3" tucks nicely with plenty of ground clearance.

R

 

[PM-Performance]

@Robert M , any dyno numbers to confirm your feelings? I hate to be that guy, but alot of times this stuff ends up being placebo.
Side note, do you know if those 3" pipes are still avail? I was told changing piping may take out some of the rasp I have with my recent axleback change, but not finding any 3" cat back to axle back mid pipes avail.

 

[DutyCalls]

I gained 38RWHP doing LTH and 3" exhaust on my 2010......thread here

https://www.svtperformance.com/threads/added-long-tubes-gained-hp-but-lost-torque.1027921/

 

[Robert M]

@Robert M , any dyno numbers to confirm your feelings? I hate to be that guy, but alot of times this stuff ends up being placebo.
Side note, do you know if those 3" pipes are still avail? I was told changing piping may take out some of the rasp I have with my recent axleback change, but not finding any 3" cat back to axle back mid pipes avail.

No, nothing to back up my claims, no dyno numbers, my car has never been on a dyno and I will probably never get it to one. BUT, that being said, if Rick at Kenne Bell says that boost is restriction and I assume restriction is going to reduce performance, then reducing the restriction must increase performance? I lost 1.5 to 2 lbs. of boost (restriction) by going to the 3". <<<Now, that being said, I am now working a deal to replace my Shelby installed 2.8 KB with a 3.2LC, which will then add back boost and additional HP.......I guess with the 3" I can now afford to add back some boost and HP while still staying on plain old 93 octane fuel. I am told that "if" I choose to reuse my 2.8 Super Snake pulley on that 3.2LC, I will be in the 19psi range and need to think about a fuel booster (Torco, etc.) with my 93 octane street fuel.

...................and I don't look at anyone as being "That guy", this mod stuff can cost a lot of money, and no one wants to throw money away for no gain. I am assuming the engine spinning up quicker means that it is more free, which usually means better performance, and my car does perform better from a drivers seat experience.

R

 

[PM-Performance]

I gained 38RWHP doing LTH and 3" exhaust on my 2010......thread here

https://www.svtperformance.com/threads/added-long-tubes-gained-hp-but-lost-torque.1027921/

I'd venture to guess your gains were more from the Long tubes than the piping change.

 

[Robert M]

I gained 38RWHP doing LTH and 3" exhaust on my 2010......thread here

https://www.svtperformance.com/threads/added-long-tubes-gained-hp-but-lost-torque.1027921/

It would be nice to have an owner who installed LTH on their oem 2.5" and see what their gains were......then it takes the LTH out of the equation and compares 2.5" to 3.0" gains only.

Ford did upsize the oem exhaust at the 550HP level to 2.75".......I would guess that the SVT engineers felt there was a performance gain with the larger exhaust piping? Many/most owners on here are wayyyyy past the 550HP level.

R

 

[PM-Performance]

No, nothing to back up my claims, no dyno numbers, my car has never been on a dyno and I will probably never get it to one. BUT, that being said, if Rick at Kenne Bell says that boost is restriction and I assume restriction is going to reduce performance, then reducing the restriction must increase performance? I lost 1.5 to 2 lbs. of boost (restriction) by going to the 3". <<<Now, that being said, I am now working a deal to replace my Shelby installed 2.8 KB with a 3.2LC, which will then add back boost and additional HP.......I guess with the 3" I can now afford to add back some boost and HP while still staying on plain old 93 octane fuel. I am told that "if" I choose to reuse my 2.8 Super Snake pulley on that 3.2LC, I will be in the 19psi range and need to think about a fuel booster (Torco, etc.) with my 93 octane street fuel.

...................and I don't look at anyone as being "That guy", this mod stuff can cost a lot of money, and no one wants to throw money away for no gain. I am assuming the engine spinning up quicker means that it is more free, which usually means better performance, and my car does perform better from a drivers seat experience.

R

Yes, boost is a measure of restriction. Less boost and same/more power, sure that is better. I dont think these work quite like turbo cars with changes like that. Yea long tubes and no cats make a pretty big difference, but piping I do not think makes that much difference.
But they are correct. I mean that is kind of the point where guys get with these big blowers on non supported setups that are to make bigger power. They just bolt on a big blower with a big pulley and makes the same power as their smaller blower with smaller pulley. Remember that convo we had about the KB with big pulley vs VMP's video talking about their 3R on a smaller pulley making the same/more power than the KB? It all goes hand in hand.
Turbo guys been doing this forever too. Its much cooler to say you make the same or more power than someone else on less boost. lol. Just up the size of your power adder and done deal!

 

[PM-Performance]

It would be nice to have an owner who installed LTH on their oem 2.5" and see what their gains were......then it takes the LTH out of the equation and compares 2.5" to 3.0" gains only.

Ford did upsize the oem exhaust at the 550HP level to 2.75".......I would guess that the SVT engineers felt there was a performance gain with the larger exhaust piping? Many/most owners on here are wayyyyy past the 550HP level.

R

On that same token I have made a decent bit over 700whp on stock 07-09 catback. I am curious if any power has changed from uncorking the setup from removing the stock mufflers, but my logic tells me its gonna be moot really.
But my background is turbo setups, though so I still have hope in this theory. lol

 

[Robert M]

Yes, boost is a measure of restriction. Less boost and same/more power, sure that is better. I dont think these work quite like turbo cars with changes like that. Yea long tubes and no cats make a pretty big difference, but piping I do not think makes that much difference.
But they are correct. I mean that is kind of the point where guys get with these big blowers on non supported setups that are to make bigger power. They just bolt on a big blower with a big pulley and makes the same power as their smaller blower with smaller pulley. Remember that convo we had about the KB with big pulley vs VMP's video talking about their 3R on a smaller pulley making the same/more power than the KB? It all goes hand in hand.
Turbo guys been doing this forever too. Its much cooler to say you make the same or more power than someone else on less boost. lol. Just up the size of your power adder and done deal!

^^^^..............and then adding to this, what about the I/C CFM flow?? Ford/SVT upsized the I/C flow from the 550HP M122 to the 662HP TVS flow level, how much restriction is there directly below the blower (in blow through CFM) with a M122 I/C and a TVS on top? or like mine, a M122 I/C and a 2.8KB on top? There is a reason why all of this stuff in the flow path is upsized...............Restriction.

R

 

[PM-Performance]

^^^^..............and then adding to this, what about the I/C CFM flow?? Ford/SVT upsized the I/C flow from the 550HP M122 to the 662HP TVS flow level, how much restriction is there directly below the blower (in blow through CFM) with a M122 I/C and a TVS on top? or like mine, a M122 I/C and a 2.8KB on top? There is a reason why all of this stuff in the flow path is upsized...............Restriction.

R

Yea, Id be more worried about getting a better IC core and larger coolant plumbing to it than exhaust piping. For the same money as an exhaust upgrade, you can send your core to J2Fab for a flowmod or just buy a Bigun core and will have much better results. Just my .02

 

[Radron2626]

Most people forget this is a dual 2.5” inch system. Most turbo applications are single exhaust applications. I know a few guys making 900/900 with just long tubes and axle backs. Everything else stock. Even a guy on here mentioned he was making 1000whp through stock mufflers. I think most the exhaust gains will be long tubes, and eliminating cats/high flow cats. Just my thoughts on it.

 

[Robert M]

Yea, Id be more worried about getting a better IC core and larger coolant plumbing to it than exhaust piping. For the same money as an exhaust upgrade, you can send your core to J2Fab for a flowmod or just buy a Bigun core and will have much better results. Just my .02

I agree with that, but it is all about flow, from the CAI to the end of the exhaust. Some of it costs more to mod and some costs less. Some of it realizes larger gains and some less. <<<That is a fact.

But I still question why the SVT engineers upsized the oem exhaust from 2.50" at the 500 and 540HP levels to 2.75" for the 550HP (and also used at 662). <<<That seems to be quite a costly redesign if 2.50 would have worked just as well?

R

 

[DutyCalls]

I'd venture to guess your gains were more from the Long tubes than the piping change.

Ya, sorry, I should have read your post more carefully.

On a side note....the outlet on the stock 2010 manifolds is only 2"...its amazing we get as much power as we do.