Say you open your faucet to the max. Now replace your garden hose with a firehose and tell me which has the higher velocity water flow out the end. Or instead pinch your garden hose slightly..what happens? The water speeds up. All without changing the amount of water flowing in the hose from the faucet. It IS a delicate balance. You want the minimum size hose that can efficiantly flow the amount of water the faucet can put out. If you pinch the hose too much you just obstruct flow.
All these same ideas apply to exhaust. The higher your exhaust velocity, the quicker exhaust gases leave the cylinder head (allowing your engine to breathe easier, and make more power). Your engine is an air pump..faster air leaves, the faster more air can replace it. One reason LT's make so much power is because on top of flowing better than manifolds, they also greatly increase exhaust velocity and nearly create a vacume sucking the exhaust gas out your cylinder head.
Quote:
Originally Posted by Mark1si...
WTF??? Not trying to p!$$ you off but this statement makes no sense.
The garden hose change thing.... Water comes out the same volume same pressure. If you turn up the faucet (throttle body/manifold flow) you will get more volume. Pressure comes from a pumping station....(piston/compression ratio). Speed will slow down because the water (exhaust) has a bigger tube/hose to move in and can move freely. As far as waiting to get in and out is determined by the cam.
Im no expert I just had to add my .02 stock vette exhaust is what 2.5"? Listen to sound clips make up your own mind. Will you ever REALLY need 3"?
Say you open your faucet to the max. Now replace your garden hose with a firehose and tell me which has the higher velocity water flow out the end. Or instead pinch your garden hose slightly..what happens? The water speeds up. All without changing the amount of water flowing in the hose from the faucet. It IS a delicate balance. You want the minimum size hose that can efficiantly flow the amount of water the faucet can put out. If you pinch the hose too much you just obstruct flow.
All these same ideas apply to exhaust. The higher your exhaust velocity, the quicker exhaust gases leave the cylinder head (allowing your engine to breathe easier, and make more power). Your engine is an air pump..faster air leaves, the faster more air can replace it. One reason LT's make so much power is because on top of flowing better than manifolds, they also greatly increase exhaust velocity and nearly create a vacume sucking the exhaust gas out your cylinder head.
WTF??? Not trying to p!$$ you off but this statement makes no sense.
The garden hose change thing.... Water comes out the same volume same pressure. If you turn up the faucet (throttle body/manifold flow) you will get more volume. Pressure comes from a pumping station....(piston/compression ratio). Speed will slow down because the water (exhaust) has a bigger tube/hose to move in and can move freely. As far as waiting to get in and out is determined by the cam.
Im no expert I just had to add my .02 stock vette exhaust is what 2.5"? Listen to sound clips make up your own mind. Will you ever REALLY need 3"?
Go read Borla's web site it will explain what he's talking about.
I am not an exhaust expert, but one of the basic laws of fluid dynamics is that the sum of dynamic pressure and static pressure doesn't change, so as dynamic pressure (caused by velocity) goes up, the static pressure decreases. It is why motive flow fuel systems work, airplane wings lift, and why all sorts of other things we use everyday work how they do. Does this answer the debate, no, but there increasing velocity will lower the static pressure in the system. I am sure an engineer or physicist could crunch the numbers and tell you what the optimum relationship would be for each particular setup.
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CAGS delete, res delete, spoiler delete, Bosch Fusion, Taylor 409s, New Era intake, Optima Red Top, 50% tint, Mobil 1 everywhere and now Hawk HPS.
I am running the Kooks 1 3/4 with catted mids and over 600 hp with the mods in my sig. I really don't think they are holding me back from anymore power gains. Also there is a great exhaust video section which will help huge when picking headers and exhaust.
WTF??? Not trying to p!$$ you off but this statement makes no sense.
The garden hose change thing.... Water comes out the same volume same pressure. If you turn up the faucet (throttle body/manifold flow) you will get more volume. Pressure comes from a pumping station....(piston/compression ratio). Speed will slow down because the water (exhaust) has a bigger tube/hose to move in and can move freely. As far as waiting to get in and out is determined by the cam.
Im no expert I just had to add my .02 stock vette exhaust is what 2.5"? Listen to sound clips make up your own mind. Will you ever REALLY need 3"?
dude do a little more reading before going saying he dosnt know whats hes talking about... i would do alittle more research on this site
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Mods Kooks 1 3/4in LTS, no cats, Magnaflow exhaust, K&N CAI, Port and Polished stock throttle body, UD Pulley, 114/116 cam, dyno tune 387 rwhp 361 rwtq
Mark!si,
The size has EVERYTHING to do with the relationship between the static any dynamic pressure inside the exhuast system. It is one of the big reasons that headers are better than manifolds. With all equal length tubes, after one cylinder exhausts and it passes through the collector, its velocity (higher dynamic pressure) creates a lower static pressure and provides motive flow (venturi effect) to help speed the gasses out of the next cylinder to exhuast. So take a 2.25 and a 3 inch exhaust. In the 2.25 the gasses will be forced to flow faster than the 3 inch. This means that the static pressure in the exhaust system will be lower. Just like if you take a pressure reading on the top of an airplane's wing while in flight. The contour of the wing makes the air flow faster over the top than the bottom thus creating the pressure differential to make it lift. Obviously there is a point at which too small of a diameter of the exhaust will cause an loss of overall volume/time, but take your manifolds or headers off, get a tune that way and compare those numbers to the ones with your exhuast on, so by your theory with the unlimited diameter of no exhaust, you should pick up huge gains, but you won't because there is no decrease in static pressure caused by the velocity of the gasses in front of it.
All I am saying is that Marylandspeed has a VERY valid point and just because you don't know basic physics doesn't mean he is wrong.
Oh and Marylandspeed, thanks for swiching my order from the MAF to the Hawk HPS with no hassle, I appreciate it!
If a pipe narrows, the fluid/gas must flow faster, because of conservation of mass.
This is true to an extent... The fluid moves faster, however the volume of the fluid moving goes down as the pipe get smaller. What happens when a garden hose kinks? the amount of water decreases in volume, the speed at the kink increases but with less passing through in a given amount of time, and the hose previous to the kink expands due to increased pressure... There is a balance of size of piping and volume of air that the engine will release in a set time frame. It's similar to having boost stack on a F/I car, the engine is releasing the air faster than the exhaust can.
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Quote:
Originally Posted by Lothar...
All cams look the same, so just pick one with a cool name like "Inseminator" or "Burninator" or something.
2004 IBM M6 on Blue... 1 of 478... Stock for now...best E/T 13.34 @106mph with 2.07 60ft as of 3/1/09
2004 GTO Owner
