txplayboy001 said:Any gasoline burning motor DOES NOT NEED BACKPRESSURE to operate correctly. No back pressure is the best. You just need to up your fuel to compensate for the increased air flow through the motor if you have less backpressure.
Sorry if this is off topic, but this backpressure myth gets on my nerves. :OT:
txplayboy001 said:Well, not really that, it just reminded me about a phone call I got last night. Spent an an hour arguing the physics of how an engine operates.
txplayboy001 said:Well, like I said, less back pressure = need more fuel
You take away back pressure, it causes a lean state.
Just like any other mods you do to your car, it will effect the way it runs. Every change you make needs to be compisated somewhere else, if the computer can not do it.
Exactly! It is the same principle behind induction components. If you go too big, you get "lazy" flow and it creates turbulance and a "pushing" action needed to get it out of the way. When things are sized accordingly and matched, then it is like syphoning, once it starts flowing, displacement equals replenishment and you get an automatic flow due to a vacuum created. This vacuum created by positive displacement instead of pressure created by laziness is what helps pull airflow/gases through the combustion system and ultimately through the exhaust.10secgoal said:I think the whole idea of backpressure thru exhaust is misunderstood. It's not the actually restriction on the way out of the exhaust that causes the low end torque. It's the scavenging of the cylinder gases caused by the vacuum behind the exhaust pulse infront of it. A gas pulse exits the header and enters the pipe. On the way out it creates a suction behind it. When the next valve opens, the gas is actually pulled out of the cylinder, rather than being pushed out ALL by the piston. If your exhaust is too big for the amount of gas exiting, it will not form a "seal" if you will. And if it doesn't, you now have no vacuum behind the pulse and no scavenging effect.
crunchie12268 said:Start talking to those ricer ppl and they will argue you to death about back pressure and there turbos..... I would think you need some back pressure to be beneficial but I don't know.
10secgoal said:I was running no pipes or mufflers for a while (nasty driveshaft problem took the both out ), which I would guess is as close to no back pressure as you can get. I went and put on exhuast and picked up et and 2 mph. I don't think and motor NEEDS back pressure, but because it doesn't need it to run right, that doesn't mean that adding some will not benefit the car.
I think the whole idea of backpressure thru exhaust is misunderstood. It's not the actually restriction on the way out of the exhaust that causes the low end torque. It's the scavenging of the cylinder gases caused by the vacuum behind the exhaust pulse infront of it. A gas pulse exits the header and enters the pipe. On the way out it creates a suction behind it. When the next valve opens, the gas is actually pulled out of the cylinder, rather than being pushed out ALL by the piston. If your exhaust is too big for the amount of gas exiting, it will not form a "seal" if you will. And if it doesn't, you now have no vacuum behind the pulse and no scavenging effect.
HISSIN50 said:also, about ricers. hmmm. putting a sewer pipe after a stock 1.5 inch pipe makes no difference - the stock pipe is still the bottleneck. i dont understand the fart can thing though myself.
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