Ok so I've read a lot on here about back pressure and I seem to be getting mixed opinions. My question is if a loss of back pressure can hurt the performance of the car. I have stock manifolds, O/R Prochamber, and straight pipes, So I really have hardly any backpressure. Is this hurting the car in any way? Thanks for the help guys

 

You want some backpressure to maximize low-rpm torque. With no back pressure, you lose some low-rpm torque, but gain some high-rpm horsepower. If you don't mind revving a lot to get to the peak power, the backpressure doesn't matter. However, if you want low speed torque for daily driving and quick sprints, then keep some backpressure in your exhaust.

 

I've always been of the mind that back pressure hurts more than it helps (if it helps at all) since the engine has to push the spent charge out of the engine, nobody (and I mean nobody) has ever been able to offer a satisfactory answer as to the reason why back pressure is beneficial.

A really good exhaust system can alter the torque curve of an engine by changing the scavenging characteristics of the exhuast (thats about as simple as I can say it since a good exhuast system might not really be over scavenging the exhaust).

 

Back pressure is critical in two cycle applications where you don't want your fresh charge to escape the piston port before it closes. Outboard Marine Corporation perfected the loop-charged 70 hp three cylinder engine in about 1968 or so, and the pulse of one exhaust would re-pressurize the next piston to get an over-ambient fuel charge, as the piston first covers the intake and then the exhaust port.
In the four cycle engine, you always want minimum back pressure, providing you don't fool the computer. The catalytic converters have sensors on both sides of them, and perhaps with too little exhaust pressure, these sensors aren't reading quite correctly, but this is a big guess.

 

Did you stay at a Holiday Inn? ....just kidding Your right about back pressure but having sensors that dictate proper exhaust mixture can make emissions testing a PIA.

Hey Gearhead,I have an avavtar for you.VVVV

 

thats awesome

 

I've read that back pressure is also important to keep your heads at consistant operating temp...

 

Thank you; great avatar too. Yes, I did stay at a Holiday Inn Express last night!

 

Short of running the engine w/o exhaust system or headers, there will always be some amount of back pressure to push the exhaust charge as it were thru all the tubing, bends, chambers and catalytic converter. Back pressure magnitude is further complicated by the reversion shock waves running back up the exhaust system. Its safe to say more back pressure is harmful for performance, not sure that is so true of less.

 

I have LT's and O/R H. I did loose alittle torque down low, but it is only noticeable from a dead stop in the bottom of first. Other than that it feels stronger every where else. The gains in my case heavly out weigh the down side.

 

I bet that had more to do with tube length than back pressure.

 

You may have a pinched nerve or bulging disc. Surgery is your best option to relieve the pressure

 

Back pressure is not needed for speed. In a race you would never be powerband where the low torque applied and the added top range hp would help the car more.

 

My main concern, was that I didn't want to lose low/mid range torque. So I ended up getting a MAC prochamber with high-flow cats, in which I've noticed a substantial increase in both low and mid range torque. However I don't know if the increase is mostly from the prochamber, or from the high-flow cats. But I would probably guess that it's from both, although more than likely because of the prochamber itself

 

You want some backpressure.

 

rule number one of the scientific method ... only change one thing at time

If you change two or more things at once, you can only speculate what did how much or little.

 

What would performace on Dyno be with open headers? All things equal with cats, muffler, over axle pipes, and then without. What is difference on a Dyno. Wouldn't that be your answer?