NGM

OK For those that do not know me. I work in a shop we do DYNO Tuning. We have put many cars and trucks on the Dyno with many different motors and many different mufflers and exhaust systems. Not a single one lost torque with a more open exhaust. All of them gained torque across the entire power band. None of them detonated. I am not talking out of the side of my neck. I am talking frm real world expierence. If backpressure allowed more low end torque mufflers would come with vaccum cutouts so at idle it would be closed and and WOT they would open up.

kickinit

I wont give my resume then.

Its just another subject much like synethic oils, turbos and superchargers, dog boxes or hyds, much like alot of if but then again I dont care much. Never changes what I have done, seen and raced.

We all got opinions, and comes down to what the customer/owner likes and trusts best.

KIRT

Thanks For The Info Everybody. I'm Thinking That Maybe That Changing Exhaust On A Truck Is Not Much Different Than Changing The Pipe On My Dirt Bike. It Only Changes Where The Power Is Made.

Robotaz

There's no such thing as losing torque or HP due to backpressure. That is a myth. What is real is the fact that slowing the exhaust down by widening the pipe CAN reduce power. The math behind this is over my head, but I can tell you from calculus that if you take smaller and smaller slices of the flow and analyze them you will see that the affect of one slice in front of the other will determine it's ability to exhaust gases. If the slice of gas is not moving fast enough than it has less ability to "pull" the slice behind it. I'm not an exhaust expert so I can't put it into words, but I can promise you from years of physics classes that as you increase the speed of each pulse from a cylinder, the more it pulls the one behind it. It's almost like a reverse back pressure issue, in my own words. So you want a diameter that is big enough not to constrict the pulses, but small enough to keep the speed up. I can also tell you just from a scientific standpoint that the shorter the pipe is, the less you will have to worry about constricting it to keep the speed up. Never thought about it before, but I'm assuming that a sidepipe would be best for power and sound.

kickinit

I guess then its a good thing you never built race cars.

matstermind

Well said, thanks for dispelling this myth.

kickinit

Since some moron quoted this I had to say something.

I guess this would exclude
Ferrari
Lamborghini
Porche
BMW

Also detonation, that means you never had a single ROTARY with a straight pipe on your dyno also not many turbo charged cars either.

Yeah you can add a crap load of race cars, some I have raced and some friends that had them as well. Its actually very popular for high end/top end cars. Just to add as I mentioned in my very first post, it depends on motors and the car.

NGM

One of they guys that works in the shop has a Mazda Rx7 and its on the dyno quite often. The exhaust is very open onit. ITs loud as hell and it runs great. The last turbo vehicle we had on the dyno was Ernie Sims Twin Turbo truck. Yes we tune turbos and rotaries. We are installing a Turbo on our race car. We went from a supercharger to a turbo. We MIGHT have a clue as to what we are doing. This one is running open exhaust after the turbos.

kickinit

This can go on and on, but I would admit for what you have seen you can be right. I know for what I know and have seen I am right. Different experiences, produce different views. Otherwise we would all use 1 oil, 1 gas and blah blah blah. So I wont show my views anymore after this one.

I had a long write-up, but sometimes people have different views. Some people have done something once and think they know all, I deal with it all the time building aircraft, but thats just the way it is. Oh well......