Interesting about exhausts and VTEC...
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The Beer-man
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Interesting about exhausts and VTEC...
I was reading about Flowmaster's new axle back for the 05 Mustang and they admitted to little or no performance gains. This was their reasoning:
"Mclelland explained to us that modern engines, especially those with variable cam timing like the '05 Mustang, are not going to respond to a reduction in backpressure like older engines do. This is largely in part due to the variable cam timing and wide lobe separation angles used on modern cams. As a result the exhaust system plays very little role, if any, on scavenging and drawing the intake charge to the cylinder. It is no surprise then that we saw no significant power gains on the dyno. The factory '05 mufflers apparently flow well enough to support as much as 425 horsepower. Once you add a blower or increase displacement is when you'll see some gains from the less restrictive Flowmasters."
This is probably why our cars don't respond well. I even watch an episode of Tuner TV and they put and exhaust on an RSX Type-S and lost 5whp! Maybe this has something to do with it.
"Mclelland explained to us that modern engines, especially those with variable cam timing like the '05 Mustang, are not going to respond to a reduction in backpressure like older engines do. This is largely in part due to the variable cam timing and wide lobe separation angles used on modern cams. As a result the exhaust system plays very little role, if any, on scavenging and drawing the intake charge to the cylinder. It is no surprise then that we saw no significant power gains on the dyno. The factory '05 mufflers apparently flow well enough to support as much as 425 horsepower. Once you add a blower or increase displacement is when you'll see some gains from the less restrictive Flowmasters."
This is probably why our cars don't respond well. I even watch an episode of Tuner TV and they put and exhaust on an RSX Type-S and lost 5whp! Maybe this has something to do with it.
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well, I've been saying that our cars are tuned well from the factory all along, but no one ever listens.
Technology has evolved so much that I don't find it surprising.
Technology has evolved so much that I don't find it surprising.
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Originally Posted by CivicsRdBest
well, I've been saying that our cars are tuned well from the factory all along, but no one ever listens.
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Rep Power: 279 umm... if you've been into tuning 4 cyl cars for awhile... you'd know that this loss is directly related to backpressure. our engines actually NEED backpressure. not as much as a sport or dirt bike.... but they need it. this is why on a a NA small engine 2.25" piping is best, you get better flow (for when you put on intakes and headers). the 3" potato shooter exhausts like the A'PEXi N1 do lnothing or actually hurt performance on our cars unless there is both more air as well as fuel flowing through the motor.
a turbo car benefits from as little backpressure as possible, on the other hand
a turbo car benefits from as little backpressure as possible, on the other hand
lol, the reason why that mustang didnt see any gains is cause the muffler was axle-back. CHanging only the axl-back will only make the sound. I have greddy 2.25 piping and I noticed a difference when i took it off and on.
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Rep Power: 400 in general the less backpressure the better, but honda has a tendency to make the stock exhaust very close to the optimal flow CFM and backpressure.
aside from that, it has nothing really to do with it being a 4 cylinder. when an engine is made, the manufacturers DEtune the engine to a specific horsepower. The amount that american cars are "detuned" tend to be greater, to keep the car within their specs, since their manufacturing tolerances are not as good of quality as the imports.
aside from that, it has nothing really to do with it being a 4 cylinder. when an engine is made, the manufacturers DEtune the engine to a specific horsepower. The amount that american cars are "detuned" tend to be greater, to keep the car within their specs, since their manufacturing tolerances are not as good of quality as the imports.
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Rep Power: 0 LoL...interesting, I was just explaining to my friend to day why I wasn't going to get the hyper madaleon for that exact same reason. Lost in tq and probably not much gain in hp because of how the stock diameter is near the most efficient size. Unless I'm boosting theres no increased flow, an aftermarket exhaust won't help except sound good.
I love the tanabe hyper thouse it sounds soo good....now I have a reason to boost or swap.
I love the tanabe hyper thouse it sounds soo good....now I have a reason to boost or swap.
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Originally Posted by LogicWavelength
umm... if you've been into tuning 4 cyl cars for awhile... you'd know that this loss is directly related to backpressure. our engines actually NEED backpressure. not as much as a sport or dirt bike.... but they need it. this is why on a a NA small engine 2.25" piping is best, you get better flow (for when you put on intakes and headers). the 3" potato shooter exhausts like the A'PEXi N1 do lnothing or actually hurt performance on our cars unless there is both more air as well as fuel flowing through the motor.
a turbo car benefits from as little backpressure as possible, on the other hand
a turbo car benefits from as little backpressure as possible, on the other hand
Back pressure in an exhaust system is evil. Period. You have to design the exhaust for optimum exhuast velocity, and a variety of other factors. A 2 stroke dirt bike engine exhaust is a completely different animal.
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The Beer-man
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Originally Posted by 4drcivic2k1
That sir, is incorrect.
Back pressure in an exhaust system is evil. Period. You have to design the exhaust for optimum exhuast velocity, and a variety of other factors. A 2 stroke dirt bike engine exhaust is a completely different animal.
Back pressure in an exhaust system is evil. Period. You have to design the exhaust for optimum exhuast velocity, and a variety of other factors. A 2 stroke dirt bike engine exhaust is a completely different animal.
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What engines need is low backpressure, but high exhaust stream velocity. A fast-moving but free-flowing gas column in the exhaust helps create a rarefaction or a negative pressure wave behind the exhaust valve as it opens. This vacuum helps scavenge the cylinder of exhaust gas faster and more thoroughly with less pumping losses. An exhaust pipe that is too big in diameter has low backpressure but lower velocity. The low velocity reduces the effectiveness of this scavenging effect, which has the greatest impact on low-end torque.
Low backpressure and high exhaust stream velocity can be achieved by running straight-through free-flowing mufflers and small pipe diameters. The only two exceptions to this are turbocharged engines and engines optimized for large amounts of nitrous oxide. Both of these devices vastly increase the exhaust gas volume and simply need larger pipes to get rid of it all.
So yes, some back pressure is needed...
What engines need is low backpressure, but high exhaust stream velocity. A fast-moving but free-flowing gas column in the exhaust helps create a rarefaction or a negative pressure wave behind the exhaust valve as it opens. This vacuum helps scavenge the cylinder of exhaust gas faster and more thoroughly with less pumping losses. An exhaust pipe that is too big in diameter has low backpressure but lower velocity. The low velocity reduces the effectiveness of this scavenging effect, which has the greatest impact on low-end torque.
Low backpressure and high exhaust stream velocity can be achieved by running straight-through free-flowing mufflers and small pipe diameters. The only two exceptions to this are turbocharged engines and engines optimized for large amounts of nitrous oxide. Both of these devices vastly increase the exhaust gas volume and simply need larger pipes to get rid of it all.
So yes, some back pressure is needed...
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Rep Power: 0 I get bugged by a lot of exhausts on 4bangers anyways. Unless your boosted or something, they sound like bees in cans. Most of them, not all, but 95% sound like a** that I see. My turboback exhaust has very little sound, you only hear spooling loud as hell, and the BOV. Its got a quite stock 300z type sound for the exhaust, very very clean.
I felt a little gain from my catback exhaust before boosted. It wasnt bad, but probably 1-2 hp if that. more of a butt dyno. Now when I hit 0spi, it hauls so much more than any intake or exhaust would do, and I probably only get like a 10 hp gain at 0. feels more like 30 compared to an intake. lol
I felt a little gain from my catback exhaust before boosted. It wasnt bad, but probably 1-2 hp if that. more of a butt dyno. Now when I hit 0spi, it hauls so much more than any intake or exhaust would do, and I probably only get like a 10 hp gain at 0. feels more like 30 compared to an intake. lol
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Rep Power: 812 it's basic engine mechanics. Backpressure is a restriction on the engine. Now it is okay to say that adding a larger piping exhaust doesn't help power because the stock setup is already big enough.
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umm... if you've been into tuning 4 cyl cars for awhile... you'd know that this loss is directly related to backpressure. our engines actually NEED backpressure. not as much as a sport or dirt bike.... but they need it. this is why on a a NA small engine 2.25" piping is best, you get better flow (for when you put on intakes and headers). the 3" potato shooter exhausts like the A'PEXi N1 do lnothing or actually hurt performance on our cars unless there is both more air as well as fuel flowing through the motor.
And no, im most cases the stock exhaust piping isnt large enough, its there to help emissions and be quiet, and cheap.
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Rep Power: 812 not always the case. My kami 4-1 header with huge ports gave me alot more low/mid and almost no hi end power. I'll have a dyno in a few months to prove it, because there's definately a difference.
this is why i'm putting a DC5 ITR muffler on to replace my tanabe racing muffler. 2.25" piping, HP header, megan downpipe, and ITR muffler = quiet but decent gains for my n/a d17. i'm sure by swapping the two muffler's i'll gain some mid range.
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Originally Posted by gearbox
not always the case. My kami 4-1 header with huge ports gave me alot more low/mid and almost no hi end power. I'll have a dyno in a few months to prove it, because there's definately a difference.
There is more to header design than 4-1 or 4-2-1, as demonstrated by Gearbox.
