any one runnng 4" exhaust system?

[welshbuddy]

is there any one running a 4" exhaust system? catback into single exit?

 

or would there be a power loss moving from a 3" system to 4"?

 

cheers

[Tricky-Ricky]

A larger dia exhaust on an N/A engine will change the reversion characteristics of the exhaust and loose you both power and torque,

Its also one reason why people don't get the expected performance increase they thought they would when changing to non specific design, the same also applies to decats, as the std exhaust its designed/tuned to take the cats into the equation.

But most of the time people don't notice the difference as the extra sound makes you think its more powerful anyway, most exhausts for N/A cars are not even developed with power increase in mind, just louder/better sound.

[andybp]

3" single pipe is good to about 350 BHP N/A

Edited July 6, 2014 by andybp

[GMballistic]

Why would you want a 4" cat to back system??

 

I had a 3" straight through system on my turbo JDM Impreza which was more than good enough ~ from what I've seen/read people who have gone FI on their Zeds have only ever gone to 3".

 

Maybe I'm missing some but still I've never heard of anyone using 4" systems.

[Anth4130]

All my turbo cars have been 3" systems... may of had a 4" tip?

 

[Tricky-Ricky]

3" single pipe is good to about 350 BHP N/A

 

A 3" exhaust on a turbocharged engine will be good for at least 750BHP, so its not likely to limit an N/A engine,

An N/A engine needs an exhaust system that designed around the engines pulse characteristic's, whereas a turbocharged

engines biggest restriction is the turbo it self, so anything you can do to make the exhaust after the turbo flow more freely will help power,

so doing the same to a N/A engine will just result in disappointment.

[CJRamze]

You'd lose power, it'd look snazzy but you'd have the slowest zed out there.

[Jetpilot]

3" single pipe is good to about 350 BHP N/A

 

A 3" exhaust on a turbocharged engine will be good for at least 750BHP, so its not likely to limit an N/A engine,

An N/A engine needs an exhaust system that designed around the engines pulse characteristic's, whereas a turbocharged

engines biggest restriction is the turbo it self, so anything you can do to make the exhaust after the turbo flow more freely will help power,

so doing the same to a N/A engine will just result in disappointment.

 

I personally wouldnt agree with that, i ran a 3" system on my Rx7, it was running 450bhp on low boost, over 500bhp on high boost, still only 1.1-1.2 bar, i swapped to a 3.5" system, the turbo spooled quicker and result in a few more bhp, had i gone to 4" i would have noticed similar improvement again

 

http://www.exhaustvideos.com/faq/how-to-calculate-muffler-size-pipe-diameter/

[lmc]

3" single pipe is good to about 350 BHP N/A

 

A 3" exhaust on a turbocharged engine will be good for at least 750BHP, so its not likely to limit an N/A engine,

An N/A engine needs an exhaust system that designed around the engines pulse characteristic's, whereas a turbocharged

engines biggest restriction is the turbo it self, so anything you can do to make the exhaust after the turbo flow more freely will help power,

so doing the same to a N/A engine will just result in disappointment.

 

I personally wouldnt agree with that, i ran a 3" system on my Rx7, it was running 450bhp on low boost, over 500bhp on high boost, still only 1.1-1.2 bar, i swapped to a 3.5" system, the turbo spooled quicker and result in a few more bhp, had i gone to 4" i would have noticed similar improvement again

 

http://www.exhaustvideos.com/faq/how-to-calculate-muffler-size-pipe-diameter/

 

 

+1

I ran a 4" system from turbo back on my rx7 helps the turbo spool faster.

There are plenty of people that run 5" systems on turbo cars

[Tricky-Ricky]

3" single pipe is good to about 350 BHP N/A

 

A 3" exhaust on a turbocharged engine will be good for at least 750BHP, so its not likely to limit an N/A engine,

An N/A engine needs an exhaust system that designed around the engines pulse characteristic's, whereas a turbocharged

engines biggest restriction is the turbo it self, so anything you can do to make the exhaust after the turbo flow more freely will help power,

so doing the same to a N/A engine will just result in disappointment.

 

I personally wouldnt agree with that, i ran a 3" system on my Rx7, it was running 450bhp on low boost, over 500bhp on high boost, still only 1.1-1.2 bar, i swapped to a 3.5" system, the turbo spooled quicker and result in a few more bhp, had i gone to 4" i would have noticed similar improvement again

 

http://www.exhaustvi...-pipe-diameter/

3" single pipe is good to about 350 BHP N/A

 

A 3" exhaust on a turbocharged engine will be good for at least 750BHP, so its not likely to limit an N/A engine,

An N/A engine needs an exhaust system that designed around the engines pulse characteristic's, whereas a turbocharged

engines biggest restriction is the turbo it self, so anything you can do to make the exhaust after the turbo flow more freely will help power,

so doing the same to a N/A engine will just result in disappointment.

 

I personally wouldnt agree with that, i ran a 3" system on my Rx7, it was running 450bhp on low boost, over 500bhp on high boost, still only 1.1-1.2 bar, i swapped to a 3.5" system, the turbo spooled quicker and result in a few more bhp, had i gone to 4" i would have noticed similar improvement again

 

http://www.exhaustvi...-pipe-diameter/

 

 

+1

I ran a 4" system from turbo back on my rx7 helps the turbo spool faster.

There are plenty of people that run 5" systems on turbo cars

 

 

 

May apply to a rotary due to they need scavenging effect to work effectively, but in general a 3" exhaust will be fine for your std configuration turbocharged combustion engines, i ran 550BHP on my Supra with a 3" exhaust, and know plenty of others making far more power on a 3" exhaust, and others running in excess of 1000BHP on a 4". system.

 

But in any case i think you guys have misunderstood my point, i was mealy saying that on a N/A engine a large exhaust was not necessary, and indeed contrary to making power, whereas a turbocharged engine needed a large sized exhaust.

So the 750BHP was a genaralisation.

[andybp]

we seem to have gone off track here this subject is far from a simple big is good small is bad

a single 3" system on a mildly tuned n/a z will be a good compromise between not being a restriction to the flow and maintaining exhaust gas velocity

in a turbo engine you generally want as little back pressure as possible in the system so big is usually good

you probably can make 750 bhp on a 3" system but that doesn't mean it's not restrictive therefore inefficient

sadly this is not a simple subject and i'm sure someone will tell me i don't know what i'm talking about

[Jetpilot]

3" single pipe is good to about 350 BHP N/A

 

A 3" exhaust on a turbocharged engine will be good for at least 750BHP, so its not likely to limit an N/A engine,

An N/A engine needs an exhaust system that designed around the engines pulse characteristic's, whereas a turbocharged

engines biggest restriction is the turbo it self, so anything you can do to make the exhaust after the turbo flow more freely will help power,

so doing the same to a N/A engine will just result in disappointment.

 

I personally wouldnt agree with that, i ran a 3" system on my Rx7, it was running 450bhp on low boost, over 500bhp on high boost, still only 1.1-1.2 bar, i swapped to a 3.5" system, the turbo spooled quicker and result in a few more bhp, had i gone to 4" i would have noticed similar improvement again

 

http://www.exhaustvi...-pipe-diameter/

3" single pipe is good to about 350 BHP N/A

 

A 3" exhaust on a turbocharged engine will be good for at least 750BHP, so its not likely to limit an N/A engine,

An N/A engine needs an exhaust system that designed around the engines pulse characteristic's, whereas a turbocharged

engines biggest restriction is the turbo it self, so anything you can do to make the exhaust after the turbo flow more freely will help power,

so doing the same to a N/A engine will just result in disappointment.

 

I personally wouldnt agree with that, i ran a 3" system on my Rx7, it was running 450bhp on low boost, over 500bhp on high boost, still only 1.1-1.2 bar, i swapped to a 3.5" system, the turbo spooled quicker and result in a few more bhp, had i gone to 4" i would have noticed similar improvement again

 

http://www.exhaustvi...-pipe-diameter/

 

 

+1

I ran a 4" system from turbo back on my rx7 helps the turbo spool faster.

There are plenty of people that run 5" systems on turbo cars

 

 

 

May apply to a rotary due to they need scavenging effect to work effectively, but in general a 3" exhaust will be fine for your std configuration turbocharged combustion engines, i ran 550BHP on my Supra with a 3" exhaust, and know plenty of others making far more power on a 3" exhaust, and others running in excess of 1000BHP on a 4". system.

 

But in any case i think you guys have misunderstood my point, i was mealy saying that on a N/A engine a large exhaust was not necessary, and indeed contrary to making power, whereas a turbocharged engine needed a large sized exhaust.

So the 750BHP was a genaralisation.

 

No didnt misunderstand

 

A car will happily run the figures you quoted on 3" exhausts, but you will get better gains from a larger exhaust as the chart suggests

Edited July 6, 2014 by Jetpilot

[Tricky-Ricky]

_{we seem to have gone off track here this subject is far from a simple big is good small is bad}

_{a single 3" system on a mildly tuned n/a z will be a good compromise between not being a restriction to the flow and maintaining exhaust gas velocity}

_{in a turbo engine you generally want as little back pressure as possible in the system so big is usually good}

_{you probably can make 750 bhp on a 3" system but that doesn't mean it's not restrictive therefore inefficient}

_{sadly this is not a simple subject and i'm sure someone will tell me i don't know what i'm talking about}

_{3" single pipe is good to about 350 BHP N/A}

 

_{A 3" exhaust on a turbocharged engine will be good for at least 750BHP, so its not likely to limit an N/A engine,}

_{An N/A engine needs an exhaust system that designed around the engines pulse characteristic's, whereas a turbocharged}

_{engines biggest restriction is the turbo it self, so anything you can do to make the exhaust after the turbo flow more freely will help power,}

_{so doing the same to a N/A engine will just result in disappointment.}

 

_{I personally wouldnt agree with that, i ran a 3" system on my Rx7, it was running 450bhp on low boost, over 500bhp on high boost, still only 1.1-1.2 bar, i swapped to a 3.5" system, the turbo spooled quicker and result in a few more bhp, had i gone to 4" i would have noticed similar improvement again}

 

_{http://www.exhaustvi...-pipe-diameter/}

_{3" single pipe is good to about 350 BHP N/A}

 

_{A 3" exhaust on a turbocharged engine will be good for at least 750BHP, so its not likely to limit an N/A engine,}

_{An N/A engine needs an exhaust system that designed around the engines pulse characteristic's, whereas a turbocharged}

_{engines biggest restriction is the turbo it self, so anything you can do to make the exhaust after the turbo flow more freely will help power,}

_{so doing the same to a N/A engine will just result in disappointment.}

 

_{I personally wouldnt agree with that, i ran a 3" system on my Rx7, it was running 450bhp on low boost, over 500bhp on high boost, still only 1.1-1.2 bar, i swapped to a 3.5" system, the turbo spooled quicker and result in a few more bhp, had i gone to 4" i would have noticed similar improvement again}

 

_{http://www.exhaustvi...-pipe-diameter/}

 

 

₊₁

_{I ran a 4" system from turbo back on my rx7 helps the turbo spool faster.}

_{There are plenty of people that run 5" systems on turbo cars}

 

 

 

_{May apply to a rotary due to they need scavenging effect to work effectively, but in general a 3" exhaust will be fine for your std configuration turbocharged combustion engines, i ran 550BHP on my Supra with a 3" exhaust, and know plenty of others making far more power on a 3" exhaust, and others running in excess of 1000BHP on a 4". system.}

 

_{But in any case i think you guys have misunderstood my point, i was mealy saying that on a N/A engine a large exhaust was not necessary, and indeed contrary to making power, whereas a turbocharged engine needed a large sized exhaust.}

_{So the 750BHP was a genaralisation.}

 

_{No didnt misunderstand}

 

_{A car will happily run the figures you quoted on 3" exhausts, but you will get better gains from a larger exhaust as the chart suggests}

 

 

 

_{LOL!You both seem to be reiterating what i have already outlined.}

_{Anyway not having a Willie waving competition, and ignoring the conjecture from the countless exhaust size calculators available on the Internet, i was just trying to point out that running a bigger diameter exhaust that not been specifically designed to increase performance will likely result in a loss of power form an N/A engine, simple!}

Edited July 6, 2014 by Tricky-Ricky

[Bodyboarder81]

So can someone explain such exhausts as the invidia Gemini duel , which from my calculations is 2.5" per side ( so 5" in total) and why this is ment to gain bhp? ( after remap )

[Jetpilot]

Its not that straightforward, 2.5 x 2 does not equal the same flow as a single 5". You need to use pye r squared formula. Or just look at link I posted

 

Gains are minimal on a normally aspirated engine, so 2.5 inch is more than adequate, any larger and you would probably loose hp. A balance between flow and back pressure!

Edited July 6, 2014 by Jetpilot

[Richf]

3" single pipe is good to about 350 BHP N/A

 

A 3" exhaust on a turbocharged engine will be good for at least 750BHP, so its not likely to limit an N/A engine,

An N/A engine needs an exhaust system that designed around the engines pulse characteristic's, whereas a turbocharged

engines biggest restriction is the turbo it self, so anything you can do to make the exhaust after the turbo flow more freely will help power,

so doing the same to a N/A engine will just result in disappointment.

 

I personally wouldnt agree with that, i ran a 3" system on my Rx7, it was running 450bhp on low boost, over 500bhp on high boost, still only 1.1-1.2 bar, i swapped to a 3.5" system, the turbo spooled quicker and result in a few more bhp, had i gone to 4" i would have noticed similar improvement again

 

http://www.exhaustvideos.com/faq/how-to-calculate-muffler-size-pipe-diameter/

 

 

If the engine spooled quicker with a larger exhaust then that suggests the system was restrictive at that point in the rpm range , if that was the case the performance as the rpm rose would have gotten increasingly flat as the system struggled to evacuate the exhaust gasses

 

I assume that wasn't the case so something else must've been going on

[Rock_Steady]

you get all sorts of problems when changing bore size on a turbo charged car, boost creep, surging, depends on waste gate size, twin entry or not, if they are compatible. All these things can ruin flow or make it better depending on what kind of car you've got. It's a bugger. It's never certain that you'll get an improvement if you go bigger, it can just lead to surge or boost creep.

Edited July 7, 2014 by Rock_Steady

[WhackyWill]

I like this.

 

 

But would prefer this.

 

[maddog1982]

Im having a similar dilemma, my exhaust is on its last legs. To my mind I was going to try to get a 3 inch system as I would assume it would return a greater power increase after upreving? So far I can find the Cobra and Miltek that offer this. Miltek seems to quite and the cobra sounds amazing im just not sold on how the tail pipes attach plus I have seen some reports of the exhaust being slightly to long?

I have been thinking about the Blue Flame also but waiting on news to find out if this is available in non res and 3 inch. Are they any other exhausts 3inch that you guys know about? Assume the Y-pipe is 2.5inch on every system?

[Tricky-Ricky]

Going back the the original question about 4" exhausts on an N/A, and despite my attempts to explain the different theory behind why turbocharged engines are different to an N/A, and needed a lager exhaust, which turned into a "i know best" discussion, LOL!

 

As i said before if you want to change to an aftermarket exhaust, and you want it to help make more power with the help of other breathing mods and a remap, then do check to see if its actually been developed to achieve a power/torque increase rather than just made to a pattern design, as there is no guarantee that its will actually make any real difference, aside from more noise.

[Jetpilot]

"i know best" discussion, LOL!

 

Not at all, just from practical first hand experience and informative articles with back to back testing

 

http://www.modified....aust-test-tech/

Edited July 7, 2014 by Jetpilot

[Tricky-Ricky]