Ok sick fox.lets just all run around with open headers. Why try to figure out a cool exhaust when you can just uncap it
Seems like the video covers that but I would guess at about the 500 hp levelHow do you determine when you need to step up your exhaust diameter.
I think terms might be interchanged a little here and there, but from everything I know, back pressure is a resistant pressure inside a system. Basically, a pressure force on the exhaust side that must be overcome by the expelling exhaust gases, which is not beneficial to making power.
Some back pressure does increase velocity
which can benefit low end torque on a poorly designed exhaust, but you lose any HP benefit.
The beneficial aspect of a tuned exhaust is not the exhaust "drive pressure/back pressure", but the sound wave that bounces back
that can be utilized to create a low pressure area by the open exhaust port to help suck in fresh fuel and air into the combustion chamber (increasing VE).
Or maybe I'm just stupid?
I didn' say I've never done it. It' actually pretty fun. But i wouldn' do it everydayOk sick fox.lets just all run around with open headers. Why try to figure out a cool exhaust when you can just uncap it
Excellent answer.Not the way I understand it, nor the way the video described it. You are describing resistance in you explanation, not back pressure, otherwise, agree.
Yes, not to be confused with resistance tho... and velocity is more dependent upon diameter of exhaust pipe. The back pressure you describe here is what you state in your last sentence.
Not sure about that... honestly, I have no idea... sounds right to me. ???
That wave that bounces back is known as back pressure.
100%
I don't think so.
Back pressure is not resistance, is the returning pressure that needs timed appropriately to match up with your desired power making window...
Resistance is just that, and as far as I know, the less of it the better.
Velocity will be determined first by the engine combination, but, then pipe diameter is used to dial the velocity in... pipe length is used to time the back pressure.
Here's a really interesting phenomenon I found on accident with my car.
I had Flowmaster 2 chamber mufflers on it... car has a nasty (for the street and 91 octane) solid cam in it. Car is n/a.
I started doing research about exhaust, and what nasty n/a cams really need.
Found out, the nastier the cam, the more it wants/needs/will benefit from - a straight through muffler.
Swapped in same size mufflers but with straight through design.
Prior, the car would pull to 7200rpm with ease.
Now, it screams to 7200rpm... betting it wants 7500rpm now.
Both my engine builder, and I "feel" the car is stronger above 4500rpm... pure butt-o-meter, but, if it's enough to "feel", there's gotta be a difference.
These - I am not surprised about.
No tuning changes have been made to the car.
Here's the accidental findings...
Prior the muffler swap...
It absolutely hated life below 2000rpm, and really wanted 2200 and up just to run right. and idled around 1200rpm.
Car will run along at 1750rpm now, and will lug as low as 1500rpm... prior the muffler change that was like asking to be bucked through the windshield.
Car now idles at 1050rpm.
Might be time to re-tune.
Had no idea mufflers would help the drivabilty... didn't see that coming.
Not the way I understand it, nor the way the video described it. You are describing resistance in you explanation, not back pressure, otherwise, agree.
Yes, not to be confused with resistance tho... and velocity is more dependent upon diameter of exhaust pipe. The back pressure you describe here is what you state in your last sentence.
Not sure about that... honestly, I have no idea... sounds right to me. ???
That wave that bounces back is known as back pressure.
100%
I don't think so.
Back pressure is not resistance, is the returning pressure that needs timed appropriately to match up with your desired power making window...
Resistance is just that, and as far as I know, the less of it the better.
Velocity will be determined first by the engine combination, but, then pipe diameter is used to dial the velocity in... pipe length is used to time the back pressure.
Here's a really interesting phenomenon I found on accident with my car.
I had Flowmaster 2 chamber mufflers on it... car has a nasty (for the street and 91 octane) solid cam in it. Car is n/a.
I started doing research about exhaust, and what nasty n/a cams really need.
Found out, the nastier the cam, the more it wants/needs/will benefit from - a straight through muffler.
Swapped in same size mufflers but with straight through design.
Prior, the car would pull to 7200rpm with ease.
Now, it screams to 7200rpm... betting it wants 7500rpm now.
Both my engine builder, and I "feel" the car is stronger above 4500rpm... pure butt-o-meter, but, if it's enough to "feel", there's gotta be a difference.
These - I am not surprised about.
No tuning changes have been made to the car.
Here's the accidental findings...
Prior the muffler swap...
It absolutely hated life below 2000rpm, and really wanted 2200 and up just to run right. and idled around 1200rpm.
Car will run along at 1750rpm now, and will lug as low as 1500rpm... prior the muffler change that was like asking to be bucked through the windshield.
Car now idles at 1050rpm.
Might be time to re-tune.
Had no idea mufflers would help the drivabilty... didn't see that coming.
So on a truck they say dual chamber for the acupressure low end but what you just said about getting bottom end out of a single chamber muffler makes me wonder? I dont expect a truck answer on here just a comment. I' sure you all have trucks.most men doI didn' say I've never done it. It' actually pretty fun. But i wouldn' do it everyday
Anyone that doesn't know Grumpys Toy needs return their man card.I also new a old guy that ran a 1 1/2 pipe from the center of the cross over pipe to the rear. It was kinda a automatic dump. Looked weird seeing three pipes out the rear. Car was real well known at the salt lake city dragway. Grumpys toy was the cars name. He had been running that set up since the 70's. That man was a true street racer. We took his money though. Lol There's a old timer story for ya
Keep in mind it's the sum of all the parts that gives you what you want. Just changing a muffler on your truck likely would do little to nothing for torque, long tube headers will help the low end torque even if nothing else is done, stock induction, stock exhaust,So on a truck they say dual chamber for the acupressure low end but what you just said about getting bottom end out of a single chamber muffler makes me wonder? I dont expect a truck answer on here just a comment. I' sure you all have trucks.most men do
We're on the same page. Thanks for the additional education.cleanlx, you definitely understand physically what is happening, and this is semantics, but the pressure waves reflecting back and forth in the exhaust, and also in the intake, are not "back pressure." They are known as helmholtz resonance waves. There is a lot of math that comes down to adjusting length and diameter of your primaries to target a specific rpm band. However, "backpressure" works against resonance tuning and scavenging. It is just basic exhaust air pressure before the effects of resonance tuning and scavenging, and it is always bad. The smaller the pipe and longer the pipe, the more back pressure. At least, that is my understanding of the semantics of all of it.
When it's not loud enought with that lumpy camHow do you determine when you need to step up your exhaust diameter.
Not sure about that... honestly, I have no idea... sounds right to me. ???
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