ESE's works engine tuner

[aljaxon]

Al , you are making it all way to complicated for a shitbox road bike.
The skinny pipe has way too steep rear cone angles for a cruiser , and the FOS design is worse , but I guarantee that is overscavenging the hell out of the cylinder due
to the steep diffusers.
With the little info I have here is a super simple layout that will work , if the TL is correct from the other two designs.
The diffuser is simply divided into 2/3 - 1/3 lengths and the belly diameter a guess to get a shallow rear cone to fit easily.
I have no idea if the 15mm exit is correct for the projected bmep.

i built this pipe thanks Wobbly and just road tested it now (yet to try different jetting but seems ok) and using video speedo comparison it has the same accel as the thin pipe, but is ever so slightly slower acell than the fat pipe in the top 2 gears. fat pipe with its over rev to 10k can change up back into the power.

the fat pipe is still the best pipe yet shouldnt work and the rear cones are probably only for ornament?

all have same tuned length, thin stops revving at 8k, your pipe stops at 9k and the fat revs to 10k. all have exactly the same wobbly duct geometry built into the header.

i am stuggling to notice patterns of different pipe geometry in relation to on-road performance.

i am about to build 2 more pipes, one of them is an 80% thinner version of the fat pipe and the other i did take the liberty of tweaking your design by adding a 2 stage header and a 3 part rear cone which starts off shallow then steepens with each cone much like the fat pipe and maybe this initial first shallow rear cone is helping the over rev?

over rev was something i initially didnt want but have since realised with spaced out gears and only 4 of them it is essential.


for cruising purposes only all 3 pipes are a success.

[katinas]

I love it. Where can I get one? By the way, I drew a piston ported engine with a C port. Is t better? I have no idea.

Lohring Miller

Attachment 354359

With this nice scheme, maybe intake window can be opened in progressive way. Longest duration at the farthest wall of intake channel and shortest duration near C.
With more extended intake channel under A, although this will not increase the cross-section of the channel, maybe even longer duration possible without revers flow.

[philou]

"The diffuser is simply divided into 2/3 - 1/3 lengths"


This is the rule that "Jean Louis Millet" tells us.
the French exhaust specialist

[SwePatrick]

A little movie to get you going this late friday afternoon.
(i promise, it revs like a mother when i put some load to it)

[aljaxon]

so now the goalposts have moved in the quest for a perfect cruising pipe cos now it needs a bit of overrev to get me back in the power on changing up.

im guessing if i made your (wobbly) pipe design diffuser just one angle that would give me more overrev? cos it would be a steeper angle nearer to the header returning the wave quicker hence better at higher rpm

[aljaxon]

"The diffuser is simply divided into 2/3 - 1/3 lengths"


This is the rule that "Jean Louis Millet" tells us.
the French exhaust specialist

is there anywhere i can see some more of his "rules"?


the pipe that wobbly designed for my purposes demonstrates this percentage within 1 %

as i now understand the sharpest change of angle in the diffuser is where the amplitude will be highest. so not only is it about percentages but what angles they are and where in the diffusers length they occur.
nearer to header = higher up the rev range and vice versa.




has anyone ever designed a pipe that has an initial sharp diffuser followed by a very small angle mid maybe even straight? followed by a final sharp angled last difuser section? to try and enhance power at the extremes of the rev range ? in the process not sapping as much energy so there is loads left for the rear cone? as in the pic below.

the lengths and diameters are wrong but the angles are total and correct

[katinas]

is there anywhere i can see some more of his "rules"?







has anyone ever designed a pipe that has an initial sharp diffuser followed by a very small angle mid maybe even straight? followed by a final sharp angled last difuser section? to try and enhance power at the extremes of the rev range ? in the process not sapping as much energy so there is loads left for the rear cone? as in the pic below.

the lengths and diameters are wrong but the angles are total and correct

I'm not sure, maybe it's just a visual trick, but the first ring of the diffuser on YZR 500 2001 looks sharper for eye than usual.

[skako]

......................................

has anyone ever designed a pipe that has an initial sharp diffuser followed by a very small angle mid maybe even straight? followed by a final sharp angled last difuser section? to try and enhance power at the extremes of the rev range ? in the process not sapping as much energy so there is loads left for the rear cone? as in the pic below.

the lengths and diameters are wrong but the angles are total and correct

Hi Aljaxon,
I follow your tests and drawings. According to the description you gave, I adjusted your pipe drawing to LT= 820mm and Dmax = 83mm, for my 50ccm moped with piston-ported intake.
I compared the simulation and got a red characteristic graph.
My model is based on the FOS - pipe concept, which I slightly modified and after many attempts got a wider black graph.
I think that the FOS - concept is better suited for the 50cc class.

[aljaxon]

good to see that skako. i am using the wobbly duct on all the latest designs ive done and was told that the FOS pipe doesnt work well with that.

ive got 2 more to build - 1 thats a mod of a pipe that wobbly quickly and kindly designed that im currently testing
and another thinner version of a fat pipe with belly size 4.8 x ex port area. which shouldnt really work well but its the best pipe ive made out of 5 in the last few months.
once these are done and tested i might try something similar to that last design with the 3 degree main diffuser cos its easy for me to cut out the existing diffuser on an old pipe and replace it with another diffuser.
im stuck with the start and end angle but can mess about.

im only testing the pipes by changing jetting and leaving ignition alone.
i do fear that by keeping the ignition the same im not realising the full potential of some pipe designs.

i have video clips for each pipe and can compare them to see real world road performance which i now believe to have more value for my (mickey mouse) purposes than a dyno graph.

im gonna have a search on here and see what youve been up to skako to see what i can learn

[philou]

is there anywhere i can see some more of his "rules"?

he is dead.
it was paid internships with him mainly focused on construction

generally, the leak tube for 50cc is 16 mm

[skako]

Hi,
I tried to adapt the wobbly pipe, #39123, designed for aljaxon to LT= 825mm for my model.
I adjusted the pipe to have the same inlet for a better comparison.
I tried to keep the angles and dimension ratios as much as possible.
I was interested in how close I am to the characteristics of the wobbly pipe, which can be seen on the graph.
I assume that aljaxon could expect a similar characteristic on his moped at lower RPM.

[philou]

skako, you can test this one ?

Édit : 13 mm leak tube for 50cc o_0 it will break. the oil film in the cylinder will burn on the exhaust side

[Frits Overmars]

Hi,
I tried to adapt the wobbly pipe, #39123, designed for aljaxon to LT= 825mm for my model.
I adjusted the pipe to have the same inlet for a better comparison.
I tried to keep the angles and dimension ratios as much as possible.
I was interested in how close I am to the characteristics of the wobbly pipe, which can be seen on the graph.
I assume that aljaxon could expect a similar characteristic on his moped at lower RPM.

Skako, the 13 mm Ø restrictor in your pipe drawing corresponds neatly to the 13 crankshaft-kW (17,43 crankshaft-HP) in your power curve.
But as soon as the engine starts making more power than that, 13 mm Ø will be dangerously small.
As a rule of thumb the restrictor diameter should be at least 3,1* the square root of the crankshaft-HP. Also notice the comment in the FOS exhaust concept below.

[aljaxon]

he is dead.
it was paid internships with him mainly focused on construction

generally, the leak tube for 50cc is 16 mm

shame.
i use a 16mm stinger outlet on my aircooled 74cc kit and my ex port area is 25mm diameter equivalent and i find i do get quite hot under sustained high load.
i might try 17mm to see if temps come down.

[aljaxon]

Hi,
I tried to adapt the wobbly pipe, #39123, designed for aljaxon to LT= 825mm for my model.
I adjusted the pipe to have the same inlet for a better comparison.
I tried to keep the angles and dimension ratios as much as possible.
I was interested in how close I am to the characteristics of the wobbly pipe, which can be seen on the graph.
I assume that aljaxon could expect a similar characteristic on his moped at lower RPM.

out of the 5 pipes ive made since october for this bike the lower "fat" one is the best pipe. stupidly fat 4.7 x belly to ex port area. using the wobbly duct geometry to start things off. ive left the dims off the lower pipes first part but they are the same as the above pipe. the too sharp rear cone doesnt mess things up because i am told the energy has all been used up by the diffusers sharp angles. its annoying because when i stick to the "rules" i get a lesser pipe.