2 1/4" catback vs 2 1/2" any difference?

Scott W

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#1

• Nov 24, 2007

• #1

I have a dynomax super turbo cat-back system on my car right now. From what I know there are 3 hp gains to be made by going from stock to a 2 1/2" cat-back

1. aftermarket pipes are mandrel bent vs ford 'crush' bends

2. aftermarket mufflers flow better that ford factory

3. 2 1/2" piping vs stock 2 1/4"

since I have a 2 1/4" mandrel bent system with aftermarket mufflers already, would there be any significant hp increases to be made simply by upgrading the pipe size 1/4".

any help, opinions would be much appreciated.

P.S. I have read several times that dual 2 1/4" pipes are good for up to 300 hp, however I have also read that they are good for up to 550 rwhp. any idea?

many turbos are running a single 3" exhaust, which actually flows less than dual 2 1/4's, and I've read of 8 seconds passes on a single 3", making me think that dual 2 1/4's should be able to handle over 500hp.

 

Mustang5L5

That is…until I whipped out my Bissell

Mod Dude

Feb 18, 2001

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#2

• Nov 24, 2007

• #2

It's tough to say how many HP you will gain. It really is different for each vehicle. Only way to really be sure is to dyno test the car.

With that said, yes 2.5" is better than 2.25, but how much depends on your mod level.

 

Scott W

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#3

• Nov 24, 2007

• #3

I can't see there being a huge difference until you get into some pretty high horsepower numbers, at that point the 2.25" will be limiting.

 

Mustang5L5

That is…until I whipped out my Bissell

Mod Dude

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#4

• Nov 24, 2007

• #4

Well like i said, there are other factors. Headers? WHat type of H-pipe? We talking just a 2.5" cat-back with remaining stock exhaust?


Most people don't like to buy things twice. Having a 2.5" exhaust won't hurt performance. Who wants to buy a 2.25" now and then get a 2.5" later down the road? I don't even think many people make 2.25" cat-backs

 

Scott W

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#5

• Nov 24, 2007

• #5

I have MAC 1 5/8 unequal length shorty's. I just purchased a mac hi-flow h-pipe with cats (emissions), I already have a 2 1/4" full catback system on the car and just wanted to know if there would be any use in going with 2 1/2"

I run NOS, but only on the track, other than that I have a cobra intake, cai,maf,... I will be putting in a crate engine down the road, but even still that will only put out about 340 hp.

 

Mustang5L5

That is…until I whipped out my Bissell

Mod Dude

Feb 18, 2001

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#6

• Nov 24, 2007

• #6

If you ever replace the cat-back down the road, go 2.5", but i wouldn't spend the money now to change it out just for the size. Ford was still putting 2.25" diamter piping on the 310HP Mach 1's.

A 2.5" diameter pipe flows 23% more volume than a 2.25" pipe.

 

Fast63

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Sep 20, 2007

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#7

• Nov 24, 2007

• #7

don't waste the money

 

white99gt

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#8

• Nov 24, 2007

• #8

You might gain 1~3rwhp ,but even that could be a variance between dyno runs.

Unless you have extra money to blow or something happens to your current system ,its not worth it.

 

Scott W

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Nov 24, 2007

#9

• Nov 24, 2007

• #9

Yeah, i think your right. I just found a good article online where they took and 89 mustang and added bolt on and then dyno tested. They only saw 6.7 rwhp when they unbolted the stock cat-back and bolted on a Flowmaster 2-1/2" system.

Since I don't have money to burn, I'll be sticking with my 2-1/4" system. The super-turbos don't sound bad, and since I won't be seeing any hp increase what's the point

thanks again.

 

B

bcmbcmbcm

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Jan 29, 2003

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Nov 25, 2007

#10

• Nov 25, 2007

• #10

Scott W said:

I have a dynomax super turbo cat-back system on my car right now. From what I know there are 3 hp gains to be made by going from stock to a 2 1/2" cat-back

1. aftermarket pipes are mandrel bent vs ford 'crush' bends

2. aftermarket mufflers flow better that ford factory

Click to expand...

I was curious how much gain can be attributed to 1 and 2 above.

I have a 2.5 system, and kind of miss the higher pitched sound of the stock 2.25 system....point is....if someone is looking for an original sound AND performance gain, could a 2.25 system with mandrel bends, higher flowing mufflers, and higher flowing cats (like 2 cats instead of 4...) provide that?

I heard that noise levels increase dramatically when increasing the diameter of the pipe. At the risk of making this more of a 'talk' thread...is that true? If it is, wouldn't a 2.25 mandrel bent system provide low noise levels, quality tone (if the right mufflers are selected), and performance capability?

 

Mustang5L5

That is…until I whipped out my Bissell

Mod Dude

Feb 18, 2001

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Nov 25, 2007

#11

• Nov 25, 2007

• #11

Way too many variables to say that one change will make a particular sound.

It's true that larger diameter piping increases sound levels, but how much is something dependant on the muffler as well. If the muffler remains the same, in theory the 2.25" system will be slightly quieter...but there is no set formula to know how much.


Exhaust systems are like a box of chocolates as the old cliche goes. Every car is different, every HP gain is different.

 

bloopbloob

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Sep 27, 2006

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Alberta

Nov 25, 2007

#12

• Nov 25, 2007

• #12

save your money and time. its definitely not worth either right now...
i hardly noticed a difference with the exhaust setup i have in my sig, so i think your money would be much better spent elsewhere
i'd say headers would be a lot more of a benefit, or save up for some heads!

 

Scott W

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Nov 25, 2007

#13

• Nov 25, 2007

• #13

I've got the headers, nitrous (125hp shot), pulleys,maf,cai,drag radials,..... but I dont' think I'd have anything to gain, i might even lose some bottom end torque- but who knows - I've read the cat-back shootout articles, and the borla 2-1/4" exhaust outperformed several of the 2-1/2"s- in fact the 2-1/4 was rated as their overall winner. Unfortunatley they didn't test any other 2-1/4" systems to see how they'd rate.

The heads will come with my new crate engine. I currently have over 300,000 km's on the car and its still running strong even with stock heads, cam.....- especially with the Nitrous. I was just thinking ahead and was wondering if the 2-1/4" will be ok with the new engine- I feel confident it'll be just fine.

 

SVT32VDOHC

waiting for the next hack atta

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Nov 26, 2007

#14

• Nov 26, 2007

• #14

I agree with 2-1/4" tubing for now. It will be good until you make big boost or run nitrous.