3" exhaust and why?

[Memphis 05]

Looking into to who has run 3" exhaust and what was the good and bad things about it...

I've got a Procharger setup on forged motor making good power. I am upgrading from the P1 to the F1A.

Just wanted to see what others have experienced with this application....

 

[Greg Hazlett]

I am upgrading my LT's and mid pipes from 1 5/8 to 1 3/4 and a 3" off road X; I am pushing 800 hp-guestimate based on my 1/4 mph-and in talking with people they think the larger headers/pipes will help the car breath better.

I was told-and it makes sense-that if air is going in at 20 psi with FI it will be coming out 2-3 times the input so that 20 psi would be 40-60 psi so the better that air can get out the better.

 

[JeremyH]

Magnaflow 3", less back pressure with the turbo setup.

 

[KillrStang]

Jeremy dont you need a little back pressure to help spool the turbo or is that only relative to pre turbo exhaust

 

[JeremyH]

No, not after the turbo, open downpipe would be idea, correct its relative to the turbo the turbine housing itself will create the back pressure already. It's back pressure after the the turbo that you want to minimize, it can slow the speed at which exhaust exits the turbine housing in the upper rpms when in boost, thus slowing it down and hurting performance. More important than the tubing size increase is the type of muffler you run, you dont want chambered mufflers with a turbo setup for this reason.

 

[matt06]

I am upgrading my LT's and mid pipes from 1 5/8 to 1 3/4 and a 3" off road X; I am pushing 800 hp-guestimate based on my 1/4 mph-and in talking with people they think the larger headers/pipes will help the car breath better.

I was told-and it makes sense-that if air is going in at 20 psi with FI it will be coming out 2-3 times the input so that 20 psi would be 40-60 psi so the better that air can get out the better.

not trying to sound like an ass but is 1/8" really worth buying new lts or do you just need them for the 3" x to work? or is there really that much of a gain?

 

[Memphis 05]

I forgot to mention that I have JBA LT and a X pipe... with exhaust cut outs for the track....no cats....

With that said... will that F1 need the rest of the pipe for everyday driving...

If so, what systems is good.???

 

[RideThePony14]

i found a 3" system with off-road x-pipe and catback on ebay from NXT-Step performance. Got a great price on it but i didn't really need 3" exhaust as i only have some bolt-on mods. The only problem i see with having a 3" exhaust is that when i lower my car, my x-pipe will be prone to scraping, so keep that in mind.

 

[HellsBells]

The only problem i see with having a 3" exhaust is that when i lower my car, my x-pipe will be prone to scraping, so keep that in mind.

Yeah, that extra 1/4" is really a huge difference in terms of ground clearance...

 

[Greg Hazlett]

not trying to sound like an ass but is 1/8" really worth buying new lts or do you just need them for the 3" x to work? or is there really that much of a gain?

I thought the same thing until it was explained that differnce is in diameter....and we do other little things like 3 or 5 angle valve jobs, upgrading a TB from 55mm to 60mm or larger so we will see if it helps..I can't see it not helping esp at the power level I am at; plus my car is built for the big end where the larger collectors should see good gains.

 

[nyuk98GT]

The increase in area is about 16% by going from 1-5/8" to 1-3/4" header tube. This means that the velocity drops by 16% and the pressure drop decreases by about 35% (since pressure drop or resistance is proportional to velocity squared). Or, the flow can increase by 16% without any increase in backpressure. To summarize the nerd-speak, a small difference in diameter can make a big difference in flow.

Chris

 

[Greg Hazlett]

^^ thanks! No where near smart enough to figure that out, glad you are!

 

[KungFuHamster]

The increase in area is about 16% by going from 1-5/8" to 1-3/4" header tube. This means that the velocity drops by 16% and the pressure drop decreases by about 35% (since pressure drop or resistance is proportional to velocity squared). Or, the flow can increase by 16% without any increase in backpressure. To summarize the nerd-speak, a small difference in diameter can make a big difference in flow.

Chris

Boyle's law?

 

[one eyed willy]

not trying to sound like an ass but is 1/8" really worth buying new lts or do you just need them for the 3" x to work? or is there really that much of a gain?

that 1/8th inch is the round diameter, which makes it way bigger of a difference than it really sounds.


i have 3" magnaflow.....love em. car spools much better than with the 2.5 i had before.

 

[matt06]

thanks for explaining that guys, makes sense now. guess ill throw it on the list of stuff to buy at some point lol

 

[Department Of Boost]

I'm kind of in the same boat. This winter I'm plopping a 3.4L Whipple on the car and looking for some pretty big numbers. Right now I have 1 5/8 Kooks LT's (well short LT's to be exact), 2.5" X and 2.5" tails and Magnaflow Magnapacks.

I would like to go 3" and have plenty of clearance (A Watts link helps a lot with that). But I don't want to go any bigger with the primary tubes and I certainly don't want longer headers. I like being able to remove things like the transmission without touching the headers. Wrapping another set of headers is not high on my list either. And with my motor lowered in conjunction with the stock K-member (haven't seen a tubular one I would want to go around corners fast with) clearance is already tight.

The plan at the top of the list is to cut the existing ball collector off of the 1 5/8 headers, replace it with a 3" collector of some sort and run off the shelf 3" exhaust.

I was thinking of making an entire oval tube "NASCAR" style system for ground clearance/aerodynamics/oval tubing is cool. But there is a good chance at some point I will spin the car off the road course. If I tear the exhaust up I would like to simply order a replacement, not make custom stuff again.

I'm just not sure what to do. I would be pretty bummed out to go to all the trouble to switch to 3" and find out it was worth 40hp for example. 40hp, probably up top in the rev range to boot, not worth the trouble when you are playing with 800+ IMO.

If I saw a decent before/after test of 2.5-3" that made some gains I would probably take the plunge. But at this point doing it because "it should make more power" is tough to swallow.

Thoughts? Thoughts on putting 3" collectors on the 1 5/8 headers?

 

[dark steed]

that 1/8th inch is the round diameter, which makes it way bigger of a difference than it really sounds.


i have 3" magnaflow.....love em. car spools much better than with the 2.5 i had before.

Yes, a diameter increase makes a huge volume increase. If you double the diameter, you quadruple the volume!


Sent from my iPhone using Tapatalk

 

[Department Of Boost]

If you double the diameter, you quadruple the volume!

That's what I keep telling her!

 

[nyuk98GT]

Boyle's law?

Bernoulli's equation.

Chris

 

[HellsBells]

Bernoulli's equation.

Chris

Fettuccine's principle