ESE's works engine tuner

[wobbly]

Here is my first thought.
The carb inlet length is still too long though, so you would have to try steeper exit divergence to shorten this up.

[F5 Dave]

what does page 58 (d) go on to?

page d: Crank balance holes have been filled. . . .
page e: . .. . 2mm higher in the new pistons. . .

erm?

[husaberg]

what does page 58 (d) go on to?

page d: Crank balance holes have been filled. . . .
page e: . .. . 2mm higher in the new pistons. . .

erm?

Oh sorry all the pages are there with the exception of the last added a page back (that was chassis related) This is how it is written sorry.
I guessed he was saying the balance holes were filled flush. and the piston gudgeon was moved 2mm higher both to lower crankcase comp? But not sure.

You could a write latter to the editor suggesting that there may be a piece missing in their August 1988 issue You could get a free subscription.

[Frits Overmars]

Frits, Wob, could you give us an insight, into how one can use the big volume of the crankcase effectively, in a high performance design? Would there be any rules connecting crank volume with ducts volume or pipe volume? I simulated two different ratios in EngMod, and the higher comp/smaller volume was up by 1+hp. Both with the same tfr duct volumes (~78cc). I did a hasty overlay of the pressure waves of the intake and exhaust:
The higher comp case caused the reeds to open less. Tfr pressure was higher from Ex open until just-before Tfr closed. Crankcase pressure was higher too. On the exhaust part, difference was mainly betweet Tfr open and close, both for cylinder and exhaust pressure - higher comp produced the higher pressure. Also, delivery ratio was much bigger in the high-comp, while TubMax was slighly less.
edit: I don't know whether I am missing something here, but EngMod kind of shows what you told us about 'pipe sucking from tfr ducts and that vol being important'. I run the same as above, with 1.45 crank comp ratio, to see a number of 30.4kw. Then, with longer TFR passages (new vol about 100cc), with 1.3 CCR it showed 33.2kw, while with 1.45 it rised to 33.6kw. I think it favorises a little the high primary comp ratios.

In order to take full benefit of a large crankcase volume you need free-flowing transfer ducts. That means: large cross sections, short gas column lengths and large time.areas. Of course I don't know which dimensions you entered into the sim, but am I wrong in thinking they may have been more restrictive than the Aprilia values?

A layman's (mine) view of the effect case volume has is that a larger volume has a smaller drop in pressure given any particular volume transfer up the transfer ducts. As it is the pressure differential between the cylinder and the case that causes the transfer flow having the largest possible pressure differential for as long as possible will result in the maximum volume flow possible. As with anything in pesky 2-strokes there is a trade-off and therefore an optimum value of crankcase volume given any particular application. You could go for smaller volume, higher compression, crankcases but that would only benefit initial transfer flow before the crankcase pressure dropped. However there may be some advantage in this setup with smaller transfer ducts if the energy in the initially rapidly moving mass in the transfer ducts could be used.Maybe.

You're not doing too bad for a layman. Skinny exhaust pipes, high crankcase compression and narrow transfers with timings over 140° were common in the sixties.
These factors were interdependent: the skinny pipes hardly produced any decent exhaust suction, so you needed the pumping action of the small crankcase volume. And because of the narrow transfer windows you needed long timings to get anywhere near workable time.areas.
Your final remark about using the energy in the initially rapidly moving mass in smaller transfer ducts needs some comment. The energy of a moving gas or mixture column depends on its mass and its velocity. In ducts with large cross sections the flow velocity does not rise too high because the crankcase pressure can drop fairly rapidly. In short, narrow ducts the velocity will rise allright, but the mass in the ducts will be small. And in long, narrow ducts the long plug of gas will resist acceleration and will only slowly come up to speed. Because long columns are such slow starters, the kinetic energy at the latter stage of transfer will only make up for what went missing at the initial stage.

Attachment 256967

This is what my ventori tube looks like, flow is from left to right, two ramps, leading ramp is 34 deg included and trailing ramp is 14 deg included angle. Could the flow be improved by making the leading edge ramp into an aero foil shape like the leading edge of an aeroplane wing as in your picture. It would certainly shorten up the tube and get the venturi point closer in behind the slide.

Yes, make it into a bellmouth. That will get you both a shorter unit and a better inflow. You might also consider putting the restriction in the bellmouth if your rules allow it. That would mean you can have a considerably longer trailing ramp (the widening can start right after the bellmouth, i.e. under the throttle slide). It also means that only the air, not the fuel, has to pass through the restriction. That way the total mass that has to be accelerated through the restriction, will be about 8 % less.

[teriks]

I'm quite sure it's already been mentioned in this thread, but it might be time to re-visit Blairs piece on bell mouth's in RET.
Unfortunately www.profblairandassociates.com seems to be down, and the pdf is over the file size limit for attachments here.
I found a copy on scribd though: http://www.scribd.com/doc/57695028/RET-Bellmouth-Sept

[dinamik2t]

In order to take full benefit of a large crankcase volume you need free-flowing transfer ducts. That means: large cross sections, short gas column lengths and large time.areas. Of course I don't know which dimensions you entered into the sim, but am I wrong in thinking they may have been more restrictive than the Aprilia values?

I used 1.2 ratio for tfr passages and about 70mm for the curved length. Total window area ~1050mm2.
There wasn't that much difference though, because I didn't notice I used "passage volume included" in some tests and "passage vol excluded" in others. In conclusion, from 1.3 to 1.4 crank comp, difference was about +0.3hp and that might be even less if inlet length was fine-tuned too.
So, my mistake.

By the way, we use RSA engine specs as a reference, for pretty much everything here.

I came across a photo that reminded me of the rsa cylinder:
Says it's the cylinder of a 250 twin RVed, by Harald Bartol (the one on KTM gp) in 1981

[SS90]

Money can't buy this.

[bucketracer]

I have been doing a lot of the Team ESE’s dyno work lately and gaining a lot of experience while getting paid to make engine parts after school for the Team as well as making an income building a special engine or two for customers, now some of our engines are leading the pack.



Having done a lot of the work helping TeeZee develop his 31hp Bucket engine, the Team recons that I have a few clues, and a bit of talent and can now call myself a real industry insider with a bit of worthwhile tuning knowledge and experience...........

[kel]

[QUOTE=bucketracer;1130253449] ... getting paid to make engine parts after school for the Team as well as making an income building a special engine or two for customers, QUOTE]

I hope you're charging accordingly (dont accept that youth rate/work experience crap), considering last weekends annihilation of what was the GP field (less southerners) you can probably name your price.

[wobbly]

As we were talking about Yamaha and their lack of results here is an interesting story.
Harold did the CNC anemometric flow testing on the BSL cylinder for me that I had lithographed in plastic.
He showed me the dyno curves of his cylinder Vs Yamahas on the 125 when he was running their team with the Japanese rider Ui.
Yamaha wouldn't let him use his 50.2 Hp set-up on the bike - even though their cylinder only managed 44.

[rgvbaz]

[QUOTE=Frits Overmars;1130252231]

You guys' creativity with the language of Shakespeare never ceases to amaze me.



QUOTE]

Frits,

If you like creative use of the english language check out the profanisaurus here http://www.milkinfirst.com/dictionary/profanisaurus.htm

which comes from Viz here http://www.viz.co.uk/profanisaurus.html

Dont show your mother! it is a bit close to the knuckle

Dave

[husaberg]

I was at the old mans for tea tonight.
Whist the ladies were gasbagging.
I took a few pics of some cylinders out of the shed.
Bear in mind this is an interestingly modded 1960's Greeves cylinder,
Maybe at the time it was a common mod but i guess it was aimed more for relibility than for performance.Maybe grump as seen the inlet mod before i don't believe it could be factory
I was quite taken with the curvaceousness of the transfers the pictures are poor quality sorry forgot my camera and used my cell.

No pics but it also has the squarest top hat combustion chamber i have ever seen.

I found a AMC cylinder too which looks like the modded Villiers that i will post below.It is amazingly heavy compared to a comparable Villiers.
No pics as it has a stuck piston at the moment.

[husaberg]

This is a Villiers engine that has had the transfers modded in a way which resembles a Piatti AMC 2 stroke.
As it is not currently attached to a racing engine i guess it is/was not the most successful mod but it is different not the length of the piston skirt on the 59x72mm 197cc engine. Note the brass inserts on the piston. Again sorry re the quality of the pics.

Oh TZ i found a swag of 1960's kart mags i will email you the pics of the stuff you want.

[koba]

Dont show your mother! it is a bit close to the knuckle

Some of that IS Shakespeare

beast with two backs n. A strange grunting animal with 2 heads and 4 legs, commonly found in bus shelters after midnight.

[Frits Overmars]

....I came across a photo that reminded me of the rsa cylinder: Says it's the cylinder of a 250 twin RVed, by Harald Bartol (the one on KTM gp) in 1981

Here is the Bartol engine to go with that cylinder: