No backpressure = good?

[MyEclipse5]

i read ahiwle ago that on a turbo car, the less backpressure the better. but when i went to a local shop they said "well i wouldn't run open DP because you need bakcpressure otherwise youll end up losing horsepower", of course those are the same guys that said "Eclipse eh, you can push a good number of boost on that lil turbo of yours, prolly up to the 15's" to which i replied, "15, i know people who have ran 20+ and are running 11's in the 1/4" he got bigeyed like he didn't believe me

So is it better to run with no backpressure on Turbo?

 

[WhiteTsiAwd]

Well the best exhaust on any turbo car, is no exhaust. Which means no back pressure.

 

[kpt4321]

Backpressure is never good on any car.

 

[MyEclipse5]

So when i go back and argue with the morons ill be right?

I told him after awhile ill get a boost controller, and hes like "o yea thatll give you a lil umph" like i was some 10 year old, wtf im not retarded








DUUUURRRRR

 

[kpt4321]

Yeah. They will tell you that a car (NA) loses power when you take the exhaust off, and that therefore it needs backpressure. You can then tell them that backpressure is merely an unwanted side effect of an exhaust that allows for proper scavenging.

 

[Chuck_3]

now im confused....becuase at school we ran our n/a car with open headers then we added a collecter to each side and gained both horsepower and torque and my instructor said you need some backpressure

 

[MyEclipse5]

now im confused....becuase at school we ran our n/a car with open headers then we added a collecter to each side and gained both horsepower and torque and my instructor said you need some backpressure

On a N/A car you do(from what i know)

on Turbo you don't

 

[kpt4321]

WRONG.

Backpressure is never ever good. Never ever.

If you run straight open headers, you will not get proper scavenging, especially at lower engine speeds. Therefore, you need to run some kind of exhaust (such as the collector, as you mentioned) for the engine to make better power under the curve.

Where did you gain horsepower and torque? Peak, ro at lower engine speeds? What did the power curve right before redline do? I bet you lost power at very high engine speeds, if you were revving the car high enough.

 

[boostedinaz]

On an N/A car you need exhaust that is tuner for the car if you are trying to extract the most HP out of it. Most the time it will be just a short amount of open pipe, but it will have no back pressure. Most the time when people do a test on a car they take a stock, weak ass small block and just lop off the exhaust. I lost power, see backpressure is better. Nice test. If you went and played with it and made pull after pull you would endup gaining a little bit of power in the curve somewhere. Peak power is not the way to judge things unless you own a Supra.

Michael

 

[Chuck_3]

a restrictive exhaust reduces performance by making the engine work harder to force exhaust gasses out of cylinders, and the engine cannot scavenge tuned exhaust gas out of the cylinder efficiently (leaves the exhaust gas in the cylinder to dilute incoming air/fuel mixtures and rob your engine of horsepower). also reduced backpressure tends to reduce combustion chamber contamination levels, which in result you get a quicker air/fuel burn.

scavenging = allows the exhaust (vacuum) pulses to interact with each other to reduce back pressure right?


i understand what you were saying about the open headers...would that cause reversion? i cant find the dyno chart for that run but i am pretty sure we kept gaining torque and hp at either 5500 or 6000 when we were cut off. but i will get back with the info once i find it im goin through all my lab work right now