2.5" vs. 3" Exhaust

[1BadAss16CS]

Short video on the subject.

[ame]

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[LETHAL]

Predictable on a Hi-Hp BBC. May be a different story on many other combos.

 

[16s550]

So does this mean I'll ultimately lose power with my BOrla sport catback when I get higher in mof list? I know the Borla sport is a 2.5 catback.

 

[BmacIL]

So does this mean I'll ultimately lose power with my BOrla sport catback when I get higher in mof list? I know the Borla sport is a 2.5 catback.

You'll only be restricted by your 2.5" if you go FI.

 

[09jsw]

ARH said in their testing 3inch to 2.5 inch axle back yielded best gains NA

 

[16s550]

ARH said in their testing 3inch to 2.5 inch axle back yielded best gains NA

Interesting

 

[VTECSAUCE]

Hard to compare a 620 BHP push rod chevy motor to a coyote with varying mods. I'd like to know what would be more beneficial for a basic bolt on coyote. I feel like 2.5" would be smarter as it probably wont lose much and will be lighter than a full 3". I have roush mufflers and an x pipe currently but later I plan to do headers with a full cat back.

 

[09jsw]

Hard to compare a 620 BHP push rod chevy motor to a coyote with varying mods. I'd like to know what would be more beneficial for a basic bolt on coyote. I feel like 2.5" would be smarter as it probably wont lose much and will be lighter than a full 3". I have roush mufflers and an x pipe currently but later I plan to do headers with a full cat back.

I agree, a bbc with cnc'd heads will flow an insane amount.

 

[david borla]

There are a few reasons why there isn't one definitive answer to this, one of which is that it depends on how you drive.

If you drive most often at wide open throttle you might benefit from a slightly larger diameter than you would if you spend most of your driving time at RPMs less than wide open throttle.

For instance, I like low end torque. It's just the way I like to drive. Acceleration off the line matters to me and I try not to shorten the life of my motor by driving at high RPMs. I rarely, if ever, reach redline.

I would never want to trade in acceleration throughout the RPM range for a bit more power up top, but that's just my preference.

Many think that a larger diameter exhaust system will reduce backpressure but that's typically only the case at wide open throttle and peak horsepower. The reality is that larger diameter exhaust systems actually create backpressure throught the RPM range on cars that don't push a lot of air.

Typically you don't see the benefits of 3" until you exceed 550 HP and even then 2.75" may outperform 3" as a whole.

Be careful with peak horsepower numbers unless you drive at wide open throttle all the time.

 

[VTECSAUCE]

I agree, a bbc with cnc'd heads will flow an insane amount.

For sure. I have noticed a lot of comparing and contrasting parts on this forum in general but a lot of variables are neglected. A CAI is a good example. Ppl claim they make no power difference. On an otherwise stock engine this is true. Add a super charger and the stock intake will start to become a choking point. It all depends on your current and future modifications.

 

[SoCalTim]

Size = Matters

 

[2015MagneticGt]

There are a few reasons why there isn't one definitive answer to this, one of which is that it depends on how you drive.

If you drive most often at wide open throttle you might benefit from a slightly larger diameter than you would if you spend most of your driving time at RPMs less than wide open throttle.

For instance, I like low end torque. It's just the way I like to drive. Acceleration off the line matters to me and I try not to shorten the life of my motor by driving at high RPMs. I rarely, if ever, reach redline.

I would never want to trade in acceleration throughout the RPM range for a bit more power up top, but that's just my preference.

Many think that a larger diameter exhaust system will reduce backpressure but that's typically only the case at wide open throttle and peak horsepower. The reality is that larger diameter exhaust systems actually create backpressure throught the RPM range on cars that don't push a lot of air.

Typically you don't see the benefits of 3" until you exceed 550 HP and even then 2.75" may outperform 3" as a whole.

Be careful with peak horsepower numbers unless you drive at wide open throttle all the time.

You make me feel bad for redlining at least once daily on my 5.0 and all my past cars, haha. Never one motor issue though

 

[VTECSAUCE]

You make me feel bad for redlining at least once daily on my 5.0 and all my past cars, haha. Never one motor issue though

Me too. I'm used to driving my Hondas. They'd beg for the abuse. This car seems to take it well too, granted I don't feel the need to do so quite as much.

 

[david borla]

You make me feel bad for redlining at least once daily on my 5.0 and all my past cars, haha. Never one motor issue though

I didn't mean it like that! :doh:

Even "once daily" would not mean the majority of the time.

How much low end torque/power are you willing to trade for that one moment each day? Is it worth being slower all day with the exception of those few seconds when you reach redline? What if you're slow even with the revs on the way to redline? What if it's not until you actually reach redline that you see gains?

 

[Strokerswild]

People seem to forget that we're displacing a measly 302 cubes, and at a fairly tame power level.

Not much need for sewer pipes unless you're running a crazy FI build....and even then....

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