ESE's works engine tuner

[husaberg]

I hesitate to compare ourselves in anyway to the great man, but Team ESE have only pretty basic hand tools to work with too.

I see huge parallels. Burt used a 30 plus year old engine Air cooled and all

[TZ350]

With a small amount of machining the outlet will fit nicely into the valve cover spigot reducing the overall length to wait for it ... 85mm!
Attachment 268152Attachment 268154Attachment 268156

Good effort ...... 85mm, I am mildly jellous .... ... Ok .. green with envy.

[TZ350]

I see huge parallels. Burt used a 30 plus year old engine Air cooled and all

I am about the same age as when he was going to Bonneville too.

[husaberg]

I am about the same age as when he was going to Bonneville too.

I was not mean enough to mention that

[Bert]

Rg50 does that by chance run the mineralli am6 cylinder?

Nope; suzuki special. crankcase reed like the old TS/DF/TF/RM... from what I can see they still make them in the TS&RMX 50s/80s...


its a little weird posting with my nickname; while everyone is posting about Burt...

[wobbly]

The tuned intake length testing I did with the reed engine was based on Dynamation sim results and as I have shown here before,involves combining the
case pressure ratio dropping below atma,at the same time as the intake length resonates with a + ratio at the reeds.
This opens them real quick,and fast,initiating intake flow early in the cycle.
Having around 135mm from bell to reed tips gives a good result centred around 12,000 rpm so works well on alot of 125s.
This tunes the intake to the 2rd harmonic from memory as it gives the best energy recovery over the widest range.
Using this approach on a 250 power unit gives really good gains ( making the length around 50% longer again ) and proves that the only reason the factories use 125 size carbs and manifolds
on these MX bikes ,is simply that there is no room.
Another pointer is that for example on the old TZ250 piston port.
If you are silly enough to remove the 20mm phenolic spacer fitted by the factory to "get some more top end ", all that happens is the the tuning range moves up past 12,000
and it is impossible to jet the thing at lower rpm.
Same with the tossers selling shortened carbs for the TZ350, simply throwing away a bunch of free mid power with no addition of any top end at all - the factory chose the big/long body Mikuni for a reason..

The RV scenario probably is working on the short 3rd harmonic, with less energy recovery, but also the very short length is mechanically desirable and reduces the deleterious effect
of the standing waves on the fuel delivery from the jets.

[dinamik2t]

The tuned intake length testing I did with the reed engine was based on Dynamation sim results and as I have shown here before,involves combining the
case pressure ratio dropping below atma,at the same time as the intake length resonates with a + ratio at the reeds.
This opens them real quick,and fast,initiating intake flow early in the cycle.
Having around 135mm from bell to reed tips gives a good result centred around 12,000 rpm so works well on alot of 125s.
This tunes the intake to the 2rd harmonic from memory as it gives the best energy recovery over the widest range.

Based on RS125 pressure graphs, with SPJ/short rubber, it is tuned on the 2nd harmonic -your memory tests great Wob. But intake pressure is a little after its '+' peak and dropping, when case pressure falls below 1atm -> in contrast with the + for the intake/- for the case, which seems to be the case for RVs and the 3rd harmonic.
The latter scenario though looks unachievable for a reed valver, unless a short carb and a zero length rubber is incorporated!

It's the point for best power spread in my files too. Intake flow starts very early!
However, intake length is around 150mm (for RS too).



edit: actually, on the RS graph, intake pressure wave is a little before its '+' peak (and rising), when crank pressure is at 0-. Sorry, I was mistaken by my pressure waves (I waver{r} too from time to time)

[RAW]

Just to head off on a different approach, is it possible to have to short of a intake length ? And if so how would one know, what type of characteristics could one expect to see?
Could it be desirable if mechanically possible to have the exhaust length / volume variable so as to achieve a desirable outcome?
With regards to the use of a power jet to switch off as a means to create a desirable overrun effect, what would one expect to see with a variable pipe length / volume, could one expect to see a power increase along with the ability to not have to use a power jet untill somewhere further up the RPM scale therefore having a greater increase in useable torque at what would have previously been the overrun rpm
The wealth of informative education within this forum is unprecedented, I now have a far greater understanding of the way a 2stroke works and as such the way I deduce and implement an idea has now become a thus far a successful one

Frits, wobbly and of coarse all of the others whom have shared there wisdom I have followed and implemented your teachings with a great personal success and relief, I now have a renewed energy to continue on within the racing scene.
A very much appreciated thanks to you all

[Frits Overmars]

Thanks for the flowers, RAW.
You can have an intake length that is too short in combination with intake diameter, intake timing, crankcase volume and desired rpm, in which case the engine will express its displeasure by blowing back some of the inhaled mixture. I prefer to shorten the intake length as much as possible and shorten the intake timing accordingly.
By varying intake length, intake timing or crankcase volume you can adapt the induction system to different rpms. I think the best way to adapt to low revs is to advance the intake closing; it will make for a docile engine with a clean, easy to set carburation.

Varying exhaust pipe length seems to be a far better way of increasing overrev than retarding the ignition or leaning out the mixture; it would be a waste not to utilize all inhaled oxygen. Varying the pipe length can also markedly lower the beginning of the power band.

[wax]

Thats a very interesting part of the thread, talking intake length . Is there a rule of thumb of tuned length for rpm.

[RAW]

Thanks for the flowers, RAW.
You can have an intake length that is too short in combination with intake diameter, intake timing, crankcase volume and desired rpm, in which case the engine will express its displeasure by blowing back some of the inhaled mixture. I prefer to shorten the intake length as much as possible and shorten the intake timing accordingly.
By varying intake length, intake timing or crankcase volume you can adapt the induction system to different rpms. I think the best way to adapt to low revs is to advance the intake closing; it will make for a docile engine with a clean, easy to set carburation.

Varying exhaust pipe length seems to be a far better way of increasing overrev than retarding the ignition or leaning out the mixture; it would be a waste not to utilize all inhaled oxygen. Varying the pipe length can also markedly lower the onset of the power band.

Understand the low revs advanced intake closing, if we were to use an engine configuration all seem to be magnetized to and of which all can see the layout of via various posts, the RSA / RSW 125.

If we were to turn the power jet of at say 12,700 rpm in the RSW / RSA engine to achieve our desired overrev, would it be prudent to alter a variable pipe length so as to raise the torque peak to a higher than previous rpm and follow up with the power jet at some later rpm than previous thus hoping to increase the overall Power of an engines forward propulsion, I'm perhaps misunderstanding this overrev phernomonom and it's link to ignition retard, the power jet lean out and increased pipe heat. as you stated the on set of the power band may also be lowered with a variable pipe, I suppose I'm looking at this with trying to achieve more useable power at the lower rpm range and also at the upper rpm threshold of which maybe in excess of 14,000 rpm

In my situation the lower rpm power I'm happy with, its the 6th gear long straights where it runs out of puff, that is untill several teaching were followed
120mm con rod
42mm carb
Shortened inlet tract
It's happy and fun now

[Drew]

On the GT125, I've come up with a way to reed feed it(trademark pending on that wee gem). Should I still aim for 130mm even though it's only feeding 67cc?

[Frits Overmars]

If we were to turn the power jet of at say 12,700 rpm in the RSW / RSA engine to achieve our desired overrev, would it be prudent to alter a variable pipe length so as to raise the torque peak to a higher than previous rpm and follow up with the power jet at some later rpm than previous thus hoping to increase the overall Power of an engines forward propulsion, I'm perhaps misunderstanding this overrev phernomonom and it's link to ignition retard, the power jet lean out and increased pipe heat. as you stated the on set of the power band may also be lowered with a variable pipe, I suppose I'm looking at this with trying to achieve more useable power at the lower rpm range and also at the upper rpm threshold of which maybe in excess of 14,000 rpm

With a variable header length you do not need to artificially raise the exhaust gas temperature, so you need neither the power jet nor the ignition retard.
The 50 cc engine with trombone pipe that I wrote about some time ago, runs strongly from 7,000 to 17,000 rpm without power jet and ignition retard.

Note: the power jet in the Aprilia RSW / RSA is gradually closed and the ignition is gradually retarded till 10° before TDC. These engines rev to 14,500 rpm. But I am convinced that with a trombone pipe they would function much better still.

[TZ350]

With a variable header length you do not need to artificially raise the exhaust gas temperature, so you need neither the power jet nor the ignition retard.
The 50 cc engine with trombone pipe that I wrote about some time ago, runs strongly from 7,000 to 17,000 rpm without power jet and ignition retard.

... a couple of recent videos from the Dutch 50 cc scene.
http://www.youtube.com/watch?v=mvV4x...feature=relmfu
http://youtu.be/0odVzSgufjk

It was designed and built by Richard Maas http://www.adriaanmeeuwsen.nl/team-pagina.html. Hopefully we will see it in action next monday.
And if I were you, I would make it go shorter with rpm .

after playing with EngMod2T again for a bit and with the exhaust port width reduced to a sensible 40mm (70%) and a few other tweeks with the Trombone pipe I find I can pretty much make the same power as before.

Attachment 262201

And it looks like a useful 5.5k power spread from 9-14.5K, with a 30+ hp peak and a virtually flat 2.5k spread across the top is on the cards using a Trombone pipe. If I can do it.

Attachment 262505

130mm Trombone Header

After playing with EngMod2T a bit more I found that the interesting thing about the pipe elements needing to stay within certain percentage limits is that when you reduce the headers length, like in the Trombone arrangement the overall tuned length also reduces so the headers percentage of the overall length does not get out of balance as quickly as you might think.

I am very taken with the Trombones possibilities and after using EngMod2T to simulate it, it looks like the Trombone is much better at extending a pipes upper range than plumping up the lower part of the torque curve below the pipes natural operating point.

So if you have an engine with a pipe good for 13K and a mechanical limit of 14 then its not much point in making a 13K trombone that can run 6K from 12 to 18.

After looking at the EngMod simulation results I think it makes better sense to discard my 13K pipe and design a pipe that’s a strong torque monster at 8K with the trombone effect extending its range out 6K to the engines 14K limit.



That’s the approach I am going to take when I make one of these for Beast-2.

A trombone and power valve combination would be even better.

[Frits Overmars]

....A trombone and power valve combination would be even better

...if you have trial riding in mind...
A (partly) closed powervalve will spoil the exhaust pulse and exclude true 180°-resonance, so you will never get a decent torque value.
I think the trombone alone will be a better choice. It will be easier to realize as well. Remember: KISS.