New ESR torque exhaust flange

[450madman]

Is it possible to not lose any top end by reducing the I.D. of the exhaust flange?
A tech or salesman at ESR swears I won't lose any top end, but I will gain quite a bit on bottom. He says Eddie has tested it out himself.
I just think there would have to be loss somewhere???
The ESR torque flange measures .140 or 9/64" smaller than the oem flange.

[FL-R]

How much are they?

[450madman]

$48

[Burns310r]

Nothing is free in this world. I will tell you that. In order to gain bottom, your going to have to sacrifice somewhere else.

[FL-R]

Very true, I don't spend a lot of time wot, my racing is in the tight woods, so this may help. Any idea if it actually works

[schuckie0920]

i think it would be a restriction and actually hurt performance you will lose some on the top end but i really dont think you will gain any bottom end at all

[Burns310r]

A smaller diameter intake will increase torque by increase the inlet velocity. But im not sure if the effect is the same on the bottom end.

I would see this affecting scavenge some as the pulse wave travels back to the engine.

[mx91a]

Might be good if you cut your exhaust port too high/wide to gain back some velocity at low RPMs but I definitely see it restricting flow and raising EGTs on the top end. My ATC Paul Turner Type 6 exhaust pipe has a smaller header diameter than normal and made great low end power but nothing up top.

[redred55]

We ran a form these in the early 90's on our LRD 265's. LRD made a "stuffer" that actually slid in the flange to reduce its I.D. I think I still have one laying around.

[addictedtomud]

I bought a setup like this from Denton Racing years ago, and it consisted of a kit with a "torque stuffer" exhaust flange and a super thick reed spacer (maybe 5/8"?). Was supposed to increase bottom end, and I paid like $80-90 for it. I don't recall noticing too much difference, because I ended up biting the bullet and getting a big bore shortly thereafter....

[450madman]

Web site says its's designed for the 310 & 330 big bores, but the guy at esr says to use it on 310 & smaller. Screw it, i'm going to bore it out to factory specs. Thanks guys!

[Motofool250r]

in the automotive world we have found some increases by using a smaller exhaust flange to create some back pressure, in fact most headers are a tad smaller then the real exhaust port size to accomplish a few things stop the exhaust wave reverberation i believe is the term they used, been a while.

but the idea was to increase the velocity of the exhaust gas, we were doing this on turbo charged vehicles though not non turbo or 2 strokes.

[C-LEIGH RACING]

Think about this.
The pipe, how it functions, has a pulse wave that travels out from the exhaust port into & threw the pipe out to the end of the pipe, then turns around & returns back to the exhaust port.
That pulse wave, is bouncing, reflecting from one side of the pipe to the other as it is traveling out to the end & then back.
The wave, travels at 1700 fps bouncing from one side to the other & the speed does not change.
In order for that wave, to travel out into the pipe to the end & then return back to the cylinder in the proper amount of time to match the porting, how that pipe is built, the ID sizes of each section of the pipe, the length of those sections & their angles, are all made to make the wave travel at a certain amount of time.
Like if you could see the wave as it was traveling inside the pipe, it would bounce from one side to the other, but if the section the wave was traveling in was only 3" across & then another section was 6" across & the wave is traveling at 1700 fps constant, then you know it would take longer for the wave to travel in the 6" section than it would in the 3" section, so everything about how a pipe built, how it is shaped, has something to do with controling the speed of that wave travel.
The speed of that wave itself never changes, 1700 fps, but that wave would take more time to bounce from one side to the other, in a section was 2 foot across as to a section only 1 foot across.

Now, that new exhaust flange piece is smaller on the inside, where the wave has to travel, so what effect is it having on that wave.
Wave dont have as far to travel, right.
Think about it.
Neil

[Honda 250r 001]

The wave would have a shorter distance to travel, making it get to where its going quicker. Correct? And that causes more power down low? But what about up high? When the wave has a shorter distance to travel, does the powerband sign off sooner?

Have you ever heard of a desgin like this Neil? Or believe it would make enough difference to be worth the money?

[rk88r]

I'm a little confused on that also. A faster return wave should favor higher rpms. Idk Niel has forgotten more about motors than I know.

[bsmith106]

I believe the temparature of the pipe affects the speed of the sound wave in the pipe. About ten twelve years ago artic cat sno pro 440 race sleds came with a button on the handlebars to retard timing on the start line to get the pipe up to operating temp before the holeshot. Not sure how many years they came that way. Many things contribute to pipe temp, jetting, ignition timing, port timing, stinger diameter and pipe volume etc. As far as this manifold goes it will change things but better or worse will be specific to your setup imo.

[C-LEIGH RACING]

When you look at a pipe, all the different shapes, lenghts of each section & overall full lenght of the pipe build, it is built like it is to control how fast that wave travels inside of it out to the end & the return back to the cylinder.
Understand, that a pipe that is built long, is for lower rpm ranges of output, where as a short type of build is for high rpm.
High rpm, everythings got to happen real fast, so that wave has to travel out to the end & then return back to the cylinder real quick.

Heat in the pipe, does have an affect on how the wave travels threw the pipe.
The wave travel speed itself, never changes from 1700 fps, but the heat can make the wave flow easier kind of like the pipe build has changed & can speed the wave flow up.
Heat, inside the pipe has an affect like the pipe has been shortened.
You can take some exhaust wrap, wrap a section on the pipe causing that section to heat up & hold heat & cause that one section to act different. Not a great amount of change, but just enough that would show while testing.

That smaller bore exhaust flange, would cause some change threw a bit more heat & shorter wave travel time, so would to some extent change the pipe build, not much but some.
Neil

[bsmith106]

Good info. Yeah I remember reading one of the affects of high rpm retard is that it heats the pipe shortening it's tuned length for better overrev.

[C-LEIGH RACING]

I could stand corrected bsmith, but on the sleds, you listen to those race engines out on the course how high rpm they are. They are constant in the higher rpm ranges, so that means the portings got to be high rpm output & for the pipes to work right with that porting, that heat kind of fakes out the pipe build just a bit to match the porting a bit closer so the engine wont bog off the start gate.

Another thing about those sleds, for every one dollar spent on performance modding the engine, at least two or three dollars more is spent on clutching to get it to match the engine.
One simple change to those engine performance wise & changes need to be made to the clutches to match.
Same is true with the automatic mini quads, just takes some dads longer to figure it out.
Neil

[bsmith106]

Clutching on sleds is key. Get it wrong and your essentially riding in the wrong "gear" all the time. Not sure what their port timing runs but the 440 race sleds were wound pretty tight. Some friends sleds were clutched to engage @ 6200 and shift @ 8800rpm, pretty narrow range. In 2008 they switched to 600s.