True tunned pipe length

[FurryOnTheInside]

These values are a starting point for proper pipe length (tunned) to the engines actual exhaust port timming and rpm.
First we need to know the exhaust ports open duration in degrees.Messured from deck to top of window.We'll start with the stock generic or older 38mm stroke and 85mm (short) rod @ .7 crown to deck.
height of window druration wave speed rpm length
28mm = 140.66 x 1,700 divided by 8,000 = 29.89"
27mm = 147 .48 x 1,700 8,000 = 31.33"
26mm = 154.10 x 1,700 8,000 = 32.74"
Now since I've yet to see a stock exhaust port higher than 26mm that should cover it,So we will move on to the stock 40mm stroke 89mm rod (long) also @ .7 crown to deck height.
28mm = 149.99 x 1,700 8,000 = 31.87"
27mm = 156.21 x 1,700 8,000 = 33.19"
26mm = 162.29 x 1,700 8,000 = 34.48"
Now we can look at a modded generic or older 38mm stroke and 85mm (short) rod @.7 crown to deck.
25mm = 160.54 x 1,700 10,000 = 27.29"
24mm = 166.84 x 1,700 10,000 = 28.36"
This is as far as I will go here since I can't recomend going above 24mm due to loss of torque.
We will now look at a modded 40mm stoke and 89mm (long) rod @ .7 crown to deck height.
25mm = 168.25 x 1,700 10,000 = 28.60"
24mm = 174.10 x 1,700 10,000 = 29.59"
The rpm used here is not the final rpm rather the peak rpm before power starts to fall off the rpm may still climb above this point depending on the type of pipe used.Next we can look at the chamber area's and cone angles to help determine the best style or type suited to the aplication. I will try to get to that soon as this takes me awhile to put up here LOL.

Great post, thank you StreetRyderz!
I can get a decent idea of what I can try; and, because I will ultimately need something that fits on my bike even if it isn't the perfect size, whether what fits will likely have any benefit and be worthwhile trying out.

 

[gary55]

Yes exactly that.

Cool and thanks for going through all that again.

 

[Steve Best]

i use two stroke wizard. always given me working results. i did prefer version 3 to version 5, and tried the "duel power" on one pipe with fairly inconclusive results. maybe on my NSR150 when i rebuild it (again...) plus finding which percentage of open space mesh is ideal... what hole size/shape, etc. plenty of variables to stuff around with.
<SNIP>

Glad to hear from you! You have been missed...

 

[Street Ryderz]

Well sorry it's been awhile since last post on this topic but my pipe designer will not save to the computer --? WTF ?.Any way it only lets me print it so I printed out the pipe diamentions and thought I could take a pic and post that well that doesn't work so well you cant read it LOL.

 

[Street Ryderz]

I'm in talks currently to have an actual exhaust company make a run of pipe's for our bike's for the go fast guys and street performers LOL.anyway this will be engineired and designed by a friend and manufactured by his company if I can do a small run,So i'm doing the market survey currently and curious how many folks on here would be interested in a Quality bolt on pipe that will actually work?

 

[HeadSmess]

y'know, when i was listing dimensions, i went to the effort to actually write them down so they could be easily read rather than squinting at a blurry picture with no contrast...

if they can make a pipe that looks a bit like this one... then it isnt going to be cheap.

yes, at some point it progressed to steel. and yes, it worked, and yes...i got quoted something like $400 to lasercut all the parts. i never tried for a second quote... then factor in a good 8 hours labour... maybe one day i will get a plasma cutter on a cnc bed, but until then...making pipes is economically unfeasible.

why the hell is it so hard to find pictures ive already used as attachments elsewhere? i had everything from the paper templates to the final product...theres even a lousy video somewhere!

oh wow. the giant! that was a long time ago!

 

[Steve Best]

It may be cheaper and easier to hydroform with a pressure washer as shown in this video:

 

[HeadSmess]

indeed. i made a few trials experiments with my nsr but gave up...

if you can bend the edge of the profile first, before welding... it works. just laying them together and welding never really pops out right.

shame i didnt have a tig welder at the time.

you need the right steel and thickness to prevent the crinkling, and ideally you will still make it in a few sections just like any factory pipe is made. take a few trials to get the dimensions correct. started on crunching the numbers to get the right profile off the bat, taking half the circumference on a given curve, the curve will tighten up. it got hard once i started factoring in the taper!

at which point, my head exploded. i hate number crunching!


but i do like giving up

 

[Steve Best]

I have made coned pipes, but not as many cones as you show. Used brazed, gasweld and TIG construction. TIG is the way to go. I used mild steel with few problems. Lasted for years and rust was not a problem. It is a lot of work.

I haven't made a pressure formed pipe. I'm guessing it will take several tries to get it to bend right, even if good at math and geometry. The beauty I see is once the pattern is discovered, making further pipes or changing the tapers is easily done.

 

[FurryOnTheInside]

haven't made a pressure formed pipe. I'm guessing it will take several tries to get it to bend right, even if good at math and geometry. The beauty I see is once the pattern is discovered, making further pipes or changing the tapers is easily done.

Can you prototype it using waterproof fabric and a domestic sewing machine?