The smart ones among you know the answer.

In case you don't................

a bit of edu-ma-cation for those who believe big pipes and big mufflers make a better faster car...

http://www.nsxprime.com/FAQ/Miscellaneous/exhausttheory.htm


.... Do Mufflers "Make" Horsepower?

The answer, simply, is no. The most efficient mufflers can only employ the same scavenging effect as a header, to help slightly overcome the loss of efficiency introduced into the system as back pressure. But I have yet to see an engine that made more power with a muffler than an open header exhaust. ..."


Exhaust headers..

in general, the best high-revving horsepower can be had with headers utilizing larger diameter, shorter primary tubes. Headers with smaller, longer primaries will get you
slightly better fuel economy and better street driveability.


Pipe Sizing

We've seen quiet a few "experienced" racers tell people that a bigger exhaust is a better exhaust. Hahaha… NOT.

As discussed earlier, exhaust gas is hot. And we'd like to keep it hot throughout the exhaust system. Why? The answer is simple. Cold air is dense air, and dense air is heavy air. We don't want our engine to be pushing a heavy mass of exhaust gas out of the tailpipe. An extremely large exhaust pipe will cause a slow exhaust flow, which will in turn give the gas plenty of time to cool off en route. ...

Unfortunately, we know of no accurate way to calculate optimal exhaust pipe diameter. This is mainly due to the random nature of an exhaust system -- things like bends or kinks in the piping, temperature fluctuations, differences in muffler design, and the lot, make selecting a pipe diameter little more than a guessing game. For engines making 250 to 350 horsepower, the generally accepted pipe diameter is 3 to 3 � inches. ...

sounds like the truth for sure ;),but not what alot of blokes want to hear i dare say!!

Unfortunately, we know of no accurate way to calculate optimal exhaust pipe diameter. This is mainly due to the random nature of an exhaust system -- things like bends or kinks in the piping, temperature fluctuations, differences in muffler design, and the lot, make selecting a pipe diameter little more than a guessing game. For engines making 250 to 350 horsepower, the generally accepted pipe diameter is 3 to 3 � inches. ...

wut.

Thats retarded

Its not random it's designed. Bend or kinks will have their own flow coefficient, the exhaust system will have a temperature fluctuation "map" which will change in temperature over rpm but maintain a similar shape. All of these things are measurable.

For a given rev range exhaust gases will be pumped out at a given rate in terms of velocity and volume (flow rate) and therefore it can be optimised. The use of programs like Aynsis have allowed this to become alot easier as they can simulate tests rather than have to physically build and test. What do you think race engineers are; muffler fitters from your local exhaust shop?

No offence but that sounds like a load of crap.

What, replacing stock muffler (which is very restrictive) on 3.5 TJ doesnt give you extra power? Cmon.... yes it wont make it into 10 second car but still the gain is definately there, people done dynos to prove it.

Title of the document: "Exhaust Theory"

Thats a nice theory they have there.. i'll stick to dyno graphs and 1/4 runs which PROVES some card do pull better numbers and times once exhausts are changed....

everyone on here says 2.5" is the "best" size for a stock or slightly mod'd 3.5L magna. why?..

remember when Dave (RPW) chucked a 3.5L magna, with 2.5" cat-bak on a dyno.. ran it.. took it off, changed the zorst to 3" cat back, ran it again straight away (same day, same dyno) and made more power? hmmmm


not argueing with the fact that no mufflers are the best mufflers though.. nothing will flow better than headers and nothing else after it....

everyone on here says 2.5" is the "best" size for a stock or slightly mod'd 3.5L magna. why?..

remember when Dave (RPW) chucked a 3.5L magna, with 2.5" cat-bak on a dyno.. ran it.. took it off, changed the zorst to 3" cat back, ran it again straight away (same day, same dyno) and made more power? hmmmm
.

yeah i have herd the exact same thing, my exhaust specialist, recently put a 3" system on a magna, N/A
and he said it worked really well.

No offence but that sounds like a load of crap.

What, replacing stock muffler (which is very restrictive) on 3.5 TJ doesnt give you extra power? Cmon.... yes it wont make it into 10 second car but still the gain is definately there, people done dynos to prove it.


Eh? Thats completely different. Stock 3.5 exec muffler is hideously restricted inside, with the pipework moving along the muffler 3 times before exiting the tailpipe. Power IS there to be made by replacing with a straight through Sports/VRX item. This particular thread is in regards to having a muffler and not having a muffler.

wut.

Thats retarded

Its not random it's designed. Bend or kinks will have their own flow coefficient, the exhaust system will have a temperature fluctuation "map" which will change in temperature over rpm but maintain a similar shape. All of these things are measurable.

For a given rev range exhaust gases will be pumped out at a given rate in terms of velocity and volume (flow rate) and therefore it can be optimised. The use of programs like Aynsis have allowed this to become alot easier as they can simulate tests rather than have to physically build and test. What do you think race engineers are; muffler fitters from your local exhaust shop?

I totally agree. Mandrel-bent pipework will always guarantee equal diameter through the entire length of the system.

also PMSL at the "muffler fitters from your local exhaust shop?" classic lol

Gremln, how much more power?

Are we talking 2%?

What was the difference in engine, air temp, oil temp, water temp, air humidity?

Also, you said cat-back exhaust - does this mean he did not have extractors?

Although I have not read the article, yes this is a 'theory', however it can easily be proven with maths, which most people who modify cars seem to not quite understand.

People always think bigger is better, care little about what an exhaust actually does, and care more about the noise and the 'oh my gawd bro i got a mad 3.e45u76349076" exhaust'..... :roll:

As for replacing a restrictive muffler with a less restrictive muffler and thinking it makes a difference....hrm, ever wonder why its called an exhaust system ? Replacing one item 85% down the line to make a difference is a little hopefull.

QUIET a few racers have said bigger is better indeed.

Sounds like a load of 17 year old HeekTIcCK civic driver crap. They think they know stuff. But really, they don't.

Gremln, how much more power?

Are we talking 2%?

What was the difference in engine, air temp, oil temp, water temp, air humidity?

Also, you said cat-back exhaust - does this mean he did not have extractors?

Although I have not read the article, yes this is a 'theory', however it can easily be proven with maths, which most people who modify cars seem to not quite understand.

People always think bigger is better, care little about what an exhaust actually does, and care more about the noise and the 'oh my gawd bro i got a mad 3.e45u76349076" exhaust'..... :roll:

cant remember power figures.. it was decent though....


As for replacing a restrictive muffler with a less restrictive muffler and thinking it makes a difference....hrm, ever wonder why its called an exhaust system ? Replacing one item 85% down the line to make a difference is a little hopefull.

mate, if your going to argue that changing a magna exec's rear muffler with a less restrictive muffler (as fitted to sports/vrx/ralliart etc) does nothing at all.. then dont bother commenting in this thread cause it just proves you no NOTHING about magnas and what exhaust changes affect them and how.... ever wondered why a magna sports and vrx has more power than the exec from the same year? do some research...

yeah its called an exhaust system .. the best system, for HP, is no system.. ie extractors a NOTHING else.... backpressure on a magna is a myth.. magnas arent 2 stroke dirt bikes

'But I have yet to see an engine that made more power with a muffler than an open header exhaust. ..."

DUUHHH!!!

yeah its called an exhaust system .. the best system, for HP, is no system.. ie extractors a NOTHING else.... backpressure on a magna is a myth.. magnas arent 2 stroke dirt bikes

backpressure on any 4 stroke piston engine is a myth.

although don't expect to go to a dyno and just drop your pipes for an instant power increase if you are already running a decent system. with less pressure for the engine to push through the engine will run more on the lean side of things which isn't always good. if the engine is tuned to run without an exhaust and then you go and put one on you will find your car running rich.

backpressure on any 4 stroke piston engine is a myth.

although don't expect to go to a dyno and just drop your pipes for an instant power increase if you are already running a decent system. with less pressure for the engine to push through the engine will run more on the lean side of things which isn't always good. if the engine is tuned to run without an exhaust and then you go and put one on you will find your car running rich.

magnas/4 stroke is what i meant yeh..

i agree you would need to tune to such a drastic change in your exhaust system

As for replacing a restrictive muffler with a less restrictive muffler and thinking it makes a difference....hrm, ever wonder why its called an exhaust system ? Replacing one item 85% down the line to make a difference is a little hopefull.


Please, you clearly don't know much about Magna's if you think this is the case :nuts:

I wasnt commenting on Magna's, but thanks for putting those words into my mouth :roll:

Since I know nothing.....

Can anyone hear show me a before and after dyno graph of a stock magna, with stock exhaust, that has just had the muffler replaced? Just interested in this :)

I wasnt commenting on Magna's, but thanks for putting those words into my mouth :roll:

Since I know nothing.....

Can anyone hear show me a before and after dyno graph of a stock magna, with stock exhaust, that has just had the muffler replaced? Just interested in this :)

refer to mitsu brouchers... 2003 exec and 2003 vrx.... rear muffler changed gave 8kw (at engine) increase...

been proven 10,000 times on here aswell.. with dyno runs and 1/4 mile runs..

gremlin, you gotta bear in mind that the 8kW increase was also to do with an ECU fiddle

gremlin, you gotta bear in mind that the 8kW increase was also to do with an ECU fiddle

was it really though????? i no this has been discussed a few times.. but was it ever confirmed that there is a difference between the tunes??

im not disagreeing just unsure if this is 100% the case..

have seen 3.5litre execs with rear muffler change running 14.8/14.9s as do stock vrx's etc.....

cheers

ECU and Cams aswell wasnt it?

ECU and Cams aswell wasnt it?


your thinking of the ralliart motor (which had ecu tune and cams and more)....

exec to sports/vrx (of same year) had same cam and same ecu (tune i think was the same, others say it was changed)..

ECU and Cams aswell wasnt it?

ECU tweaks in the early TJ's lifter power to 150kW (from 147kW in TH). Then slight cam revision and tune further improved that to 155kW. The VRX's got a free flow rear muffler that pushed it further to 163kW (no change in tune or cams from 155kW version). That used to be the agreed stats here a few years back.

Phonic - as Gremln said, I must have been thinking of the ralliart :)

ECU and Cams aswell wasnt it?

railliart was only one with dif cams.

*edit* i was beaten

Any thoughts on this?

"Both VR-X and Sports are equipped with a new high power version of Mitsubishi's familiar 3.5 litre V6. This engine's maximum outputs are 163kW and 317Nm, versus the regular 3.5's 150kW and 300Nm. Yes, those latter figures are higher than before. Alterations to the single overhead camshafts of the V6 - minor changes to the timing and duration of valve opening, both inlet and exhaust - are the reason for the improvement."

http://www.carsales.com.au/reviews/2001/medium-passenger/mitsubishi/magna/mitsubishi-magna-vrx-3963

ers, next paragraph

"The additional 13kW of the VR-X and Sports engine comes mainly from a different, less restrictive exhaust system. The engine is damned good. It has punch - even in the automatic, even on dry bitumen, full throttle in first gear will overwhelm the available traction. There's smooth flexibility as well."

So it comes from a less restrictive exhaust system, or just a less restrictive muffler? Thats what I was asking lol

However the review claims the engine is slightly tweeked with adjusted timing of the intake and exhaust.....

the rear muffler is different, also when they brought out the TJ they no longer had the resinator before the rear axle, only the one behind the cat.

it's the exact same thing with merge collectors.. there is always room for improvement.. but you try convincing some ppl that..

hence why i run a 18deg tapered merge collector on my pacemekers and enjoy the broarder torque range :)

ECU tweaks in the early TJ's lifter power to 150kW (from 147kW in TH). Then slight cam revision and tune further improved that to 155kW. The VRX's got a free flow rear muffler that pushed it further to 163kW (no change in tune or cams from 155kW version). That used to be the agreed stats here a few years back.

that is what i thought, cheers

The cam and ecu changes in the early 3.5l sports models were adopted across the entire model range in the TJ/KJ. The only difference between the standard tj magna and the vrx/sports is the rear muffler. How much power did the 3" make over the 2.5"? Or more importantly, what was the torque difference?

flatshift, the only difference between exec and sports/vrx was the rear muffler. All ran 2.5" system

The guide said that mufflers do not make HP and they are right to a point, however replacing one that has a high resistance to air flow with one that has a low resistance to air flow will definatly increase the power made by your engine. But that is just it, if you removed the muffler you would make even more power again!

Stupid article anyway.

flatshift, the only difference between exec and sports/vrx was the rear muffler. All ran 2.5" system
Thats what i said. The 3" comment was in regards to the posts saying that rpw got more power with that over the 2.5". Thats not heaps clear when i reread my post...

oh i see, np :)

yeah i have herd the exact same thing, my exhaust specialist, recently put a 3" system on a magna, N/A
and he said it worked really well.

Mine did. Just had too much drone.

Does it really need that size though?,did it lose throttle response or bottom end?,how much did it increase power/torque by if at all?,im not having a crack,just curious is all!,i thought 2.5 " was plenty in N/A applications

Steve

I thought what the article was getting at was the muffler change didnt increase "engine output" , it just released more of what was already there, but restricted by the muffler......

thats exactly what i belive magtone - it's already there.. you need to 'unleash it' lol :)

I thought what the article was getting at was the muffler change didnt increase "engine output" , it just released more of what was already there, but restricted by the muffler......


agreed, why are u all fighting over stupid ****...

Your all wrong in saying they 'make' power, because they don't. The power is already at/in the engine! Do you know car keys make power, because when u put them in the lock, they turn on the engine...show me a dyno graph of before& after key please.

agreed, why are u all fighting over stupid ****...

Your all wrong in saying they 'make' power, because they don't. The power is already at/in the engine! Do you know car keys make power, because when u put them in the lock, they turn on the engine...show me a dyno graph of before& after key please.

what the heck are you smoking dude

what the heck are you smoking dude

it was more of a fishing comment...

but i tried to get a point across too - that the engine already has a power, by putting a muffler on, it doesnt make any power, it just liberates what was getting restricted before.

you're an idiot lol

you're an idiot lol


lol why :(

I honestly believe since changing my exhaust from cat back in my AWD being 2.5 back to genuine sports muffler, it has slowed the car a little.
There is someone else on here who has found the same as well.