ESE's works engine tuner

[ken seeber]

Now, this looks interesting....

[jfn2]

Wobbly
Thank you for the explanation on the case pressure dip at EPO.
Also for the info on the reed stuffer. I was a little confused there.
I need to make 2 stuffers and want to get started on the right foot.
I would like to ask your thoughts on Boyesen's dual stage reeds for MX bikes? And how they compare to the V-force reeds.

[Vannik]

Some first order results of comparing a Banshee sim with measured traces. Some comments:

1. The sim model is currently a very rough approximation of the real engine and even more so with the pipe, I have no idea what the Toomey T6 looks like.
2. The porting is mostly based on the RZ350 model, until somebody supplies better.
3. I digitized the traces Nitro posted and then used a small amount of smoothing, getting csv files will be better.
4. For some reason I had to shift the inlet trace by 45 degrees to get alignment between the sim and measurement.

[JanBros]

Now, this looks interesting....

Am I the only one who has no clue what this is ?

[wobbly]

Neels , the RZ and Banshee ports are essentially the same bar no PV in the quad engine , but there are two series of RZ with 1mm difference in EPO , no idea which casting Yamaha used
for the quad.
As the pipe dimensions are super critical to the waveforms shape , I dont think we can safely make any coments about how good or not the sims predictive strength actually is,
until we have apples for apples.
And the differing position of the inlet sensors must be responsible for the angular displacement.

JanBros, yep the cylinder is on the dyno , waiting for a printed cover plate to do a twofold test cooling the outside of the transfer ducts , and then adding cooling and a water entry over the outside of the boost port.
I did a dyno run some time ago where all the cold water was directed into the cylinder over the boost port , cooling the transfer tops , then the Axhaust duct , then into the head.
That added 1 Hp , so I am hopefull this test will show the way for future cylinder designs.
Jan picked up 1/2 Hp simply by cooling the inside turn of the transfer ducts , this should add even more.

Edit - the Boyesen reed blocks have very very good stuffer shapes , especially for bent manifolds , but sadly the two stage reeds do very little good in relation to using a VeeForce.

[ief]

From what I can gather, same as first model ypvs except for the exhaust port hight, 29,5 vs 27 mm from top.

52 hp @ 7000 rpm vs 59 @ 8500 according to yamaha.

(edit: ypvs date seems to differ from site to site, think this is the right one)

[jfn2]

Wobbly
As you replied: "the Boyesen reed blocks have very very good stuffer shapes , especially for bent manifolds , but sadly the two stage reeds do very little good in relation to using a VeeForce."
Is this because of the increased tip area with the V-force? The reason I ask this is what if you increased the tip area on the boyesen dual stage reeds by adding a third reed on top of the second reed, or a fourth or even a fifth. I had my first reed setup from Boyesen back in 1970 when he brought out his reed system for the Husqvarna bikes. And he showed me a 3-tier reed and I also saw a 5-tier system in the back of his shop he was working on for a Maico. He didn't comment on them back then but he said he was working with some factory riders with the 3-tier system. I didn't have use of or even have a dyno back then so I cain't say for sure how well it worked but I built a few 3-tier systems and they worked very well for me. I ran them in bikes and snowmobiles. I did have a snowmobile engine dynoed back in 1972 with good results but I changed a few different things at the same time. Since the snowmobile engine was a cvt drive with clutch engagement at about 6500-8500 rpm I don't think the 3-tier reed system helped much. Your thoughts on 3 -4 tier on a v-force reed setup? Also a stuffer in a v-force setup?

[wobbly]

The VeeForce concept is somewhat more complex than just much larger tip area , but for sure its a big contributor.
Its other area of improvment is that due to the increased tip area , for the same flow rate / pressure drop thru the system much less petal lift is needed.
Thus less flow energy is used to achieve the curtain area needed to see the same pressure drop/flow rate across the block.

My take on the basic dual petal Boyesen patented setup is that it looks way more effective than it actually works in practice - but can be alot better than the stock block it replaces.
Sure , in a MX scenario , having very soft petals on top , that open easily with very little pressure delta , you can pick up a bunch of good throttle response off the pipe.
The idea is then that the bigger , thicker petal , also opens at higher airflows to contribute to the upper powerband.
But what i believe happens next is that the soft petal does what soft petals do - go spastic at the first opportunity and badly affects not only the lift profile of the main reed , but also creates
a bunch of turbulence thru the whole system.
This is exactly what happens on the flow bench as you ramp up the feed pressure.
Also its impossible to get a really effective stuffer to work with the much smaller exit area under the top petal , and expect that to work properly when the main petal opens as well.

VeeForce make the same plastic block , and use it in a bunch of differing applications , with just a change in the stuffer/mount plate, to suit whatever shape occurs when the usuall rubber ears are cut off the rubber manifold.
So in many cases you can build a very effective custom stuffer by using one from a different model bike , cut them in 1/2 and using just one side ,put them back to back inside your chosen block.
Does a really good job of making a smaller , central round hole that can then be shaped to suit a setup like 35mm carbs on a Banshee alloy manifold fitted to an LC racebike.
A huge improvment in flow/power over the aftermarket Banshee setup , as well as an even bigger jump for the LC.

[TZ350]

[porttiming124]

Portiming124 - Bonjour mon ami . OK so if you are well versed in removing the chrome , and welding the ports or dividers , then that cylinder could easily be fixed.
If thats the case , then get rid of the A port step , lift the bottom outer corner of the Aux port , and as you say get rid of the second ring and move the top pin over the boost port.
Then epoxy up the duct roofs to get modern axial angles.
Depending upon the end use , it would be much easyer to implement reverse stagger , leave the A port low and lift the B , C port 4* of duration higher , like the Aprilia scavenging pattern.
And please dont put any solder in the cylinder except to check the squish.

I sent my cylinders this week to have the nichasil removed, I will receive them within 10 days.
During this time I am looking at the STA in engmod to find the duration of the transfers.
I see that with the optimized transfer width I can have less duration and even more

[porttiming124]

that reminds me i just did another set the other day. tough little buggers trying not to blow the corner edge off and you only got one shot to get it right. proffesional machinist in oregon united states fucked up my yami cylinders and punched them to 68mm instead of 66 but to make matters worse the left cyl bore vertical centerline didnt intersect the comb chamber center. no choice but to drop in sleeves and start over . the only good news is im back at 64mm

Hello peewee.
I'll have to relocate my pin like you.
Can you explain the prosedure please ?

[philou]

I don't know if it's allowed here.

A download link to an Italian book


https://welovevespa.weebly.com/uploa...il_2_tempi.pdf

[Muhr]

Hi everyone has spent the Christmas weekend trying to understand what benefits different shapes of bellmouth have at different air speeds. Is it something that someone has investigated and if so, what have you come up with?
Have come so far that I can see an improvement in cfd but feel skeptical that I will see any major improvement in dyno.
Anyway, I'm thinking of reworking a carburetor to get this tested.

[TZ350]

I can see an improvement in cfd but feel skeptical that I will see any major improvement in dyno.
Anyway, I'm thinking of reworking a carburetor to get this tested.

Don't be disappointed if you test a carb with improved CFD and don't see a corresponding increase in output on the dyno.

After my own carb experiments I concluded that the inlet was most likely not the restriction that is holding the engine back. I found most of my improvement by improving the "Transfer" and "Trapping" efficiency of the motor. Rotary valve, big crankcase volume, A ports angled higher than the B ports.

I spent a lot of time playing with improving carburetors as their size was class limited for me. The thinking was that a 24mm carb would restrict a 125cc two stroke to something less than 20 RWHP. On the dyno, after a lot of development I made as much as 32 RWHP with a 24mm carb and single exhaust port.

But I found my air cooled motor could not reject enough waste heat to make 32 RWHP sustainable on the track. 28 RWHP was sustainable and 22 was very reliable. Heat rejection issues probably explains why the factory 125cc air cooled road racers of the day were about 28HP.

[wobbly]

Prof Blairs take on a Bellmouth.
https://www.yumpu.com/en/document/re...air-associates