ESE's works engine tuner

[lodgernz]

Looks even more impressive(and confusing) after meassuring the port timing of this cylinder. Out of the box, 39.3mm stroke, I get 180° exhaust and 121° transfers! What?!

16.5hp from a fifty with that low durations?!

With those huge auxilliary exhaust ports and the conservative timing, it's going to have very good blowdown STA. As Frits and Wobbly have been saying for a long time, this is the most significant factor in an engine's performance. I'm guessing that's why it can rev so high to make that incredible power.

I don't suppose the make a cylinder for the NSR50 do they?

[chrisc]

Looks can be deceiving, it's just a built in silencer on a "normal" rear cone. Performance is good though
Can't use the absorption type silencer in this kind of racing, the fuel is regulated to 80% Methanol + 20% Castor oil so the packing would be drenched in no time..

I'd be very interested in seeing how you built the internals of that silencer if you were happy to share.
Thanks for posting the photos. I love seeing where else 2 strokes excel in this world.

[adegnes]

I don't suppose the make a cylinder for the NSR50 do they?

They only make it for their own engine, the m50.
But where there's a will there's a way!

[peewee]

hey guys i know you dont want to see this old junk but i have to show it anyways . spent yesterday and today attempting to weld the back corners. it dont look real great but it should be fine after i dress it up. i had a hell of a time as it was the worst cast shit ive ever seen. pin holes all over and 20yrs of oil soaked in. those old yamaha cylinders weld like a dream compared to this one

[seattle smitty]

Peewee, you might know this, but don't ever clean up an aluminum casting by glass-bead-blasting if you plan on welding on it, or if you do, go over the to-be-welded area with a rotary file and skim off a little metal. Some of the glass bead will imbed itself in aluminum, and will drive a welder nuts; you can see the shiny bits under some magnification. Piston ring manufacturers have put out bulletins warning against cleaning up old pistons with glass-bead. (Have I said this here previously? Probably several times!).

[wobbly]

Here is the STA analysis of the M50.
About as accurate as the drawings allow, but shows that the Blow STA is on the money, the transfers too small - but as they flow so well
in the right directions this is not holding back the power production badly.

[adegnes]

Here is the STA analysis of the M50.
About as accurate as the drawings allow, but shows that the Blow STA is on the money, the transfers too small - but as they flow so well
in the right directions this is not holding back the power production badly.

Thank you! Means alot that you took the time!

[Larry Wiechman]

Here is the STA analysis of the M50.
About as accurate as the drawings allow, but shows that the Blow STA is on the money, the transfers too small - but as they flow so well
in the right directions this is not holding back the power production badly.

So, this engine needs an additional 21% exhaust port area to meet the targets?

[wobbly]

Ha Ha, sorry not even close.

The Exhaust STA is basically a redundant measurement.

As it has been alluded to in many pages here, reducing the Ex duct volume,by lifting the floor and filling in the bottom corner radii at
the port face has a way positive more effect - due to the velocity increase and a reduction in A port short circuiting.
Same effect at the duct exit into the header, where the rule of thumb for a 3 port is 75% exit area of the total port effective, works a treat.

Its the combination of the Blowdown STA and the Transfer STA ( modified by the discharge coefficient created by the duct shape and the port orientation )
that sets the power making potential of any 2T setup.

Forget what Cameron and Blair etal said in the literature last century, and take heed of what Thiel found in the dyno cell.

[adegnes]

Here is the STA analysis of the M50.
About as accurate as the drawings allow, but shows that the Blow STA is on the money, the transfers too small - but as they flow so well
in the right directions this is not holding back the power production badly.

All the ports are actually about 1mm higher than what I managed to show in my crappy portmap, they're nice and symmetrical to
Seem's to be a well made little cylinder - maybe I should leave those transfer ducts alone for now, in fear of screwing up the "harmony". I was going to widen them 5mm.


Could someone share how they manage to get an accurate port map? I obviously suck at it, though bad equipment has to take part of the blame.
Do you use graph paper when you trace the bore? My graph paper was too stiff to use.

[teriks]

I'd be very interested in seeing how you built the internals of that silencer if you were happy to share.
Thanks for posting the photos. I love seeing where else 2 strokes excel in this world.

Sure, it's nothing fancy. Need to get to my home computer to get the drawings, so might take some time.

[wobbly]

Well the port heights seemed fine in that the stroke length of 39.4 works on the graph paper as the height from tdc
down to the bottom of the EX measures right on that.
So the EX timing at 23mm = 92.5 atdc = 175 duration, lift it 1mm = 22mm = 89.5 atdc = 181 duration.
But we need alot more accuracy with the transfers as lifting them all 1mm makes them way too big.
You should use a long stroke dial gauge sitting on the piston, zeroed at tdc.
I took the transfer widths off the radial angle diagram, as this is the most accurate.
You do realize that using graph paper in the bore and doing the old "rubbing " thing doesn't give the true chordal widths, and that the chordal widths are
also not the actual " flow " widths needed.

[adegnes]

Well the port heights seemed fine in that the stroke length of 39.4 works on the graph paper as the height from tdc
down to the bottom of the EX measures right on that.
So the EX timing at 23mm = 92.5 atdc = 175 duration, lift it 1mm = 22mm = 89.5 atdc = 181 duration.
But we need alot more accuracy with the transfers as lifting them all 1mm makes them way too big.
You should use a long stroke dial gauge sitting on the piston, zeroed at tdc.
I took the transfer widths off the radial angle diagram, as this is the most accurate.
You do realize that using graph paper in the bore and doing the old "rubbing " thing doesn't give the true chordal widths, and that the chordal widths are
also not the actual " flow " widths needed.

Thanks for the tips! I'll be back with more accurate numbers!

[Frits Overmars]

The Exhaust STA is basically a redundant measurement....Forget what Cameron and Blair et al said in the literature last century, and take heed of what Thiel found in the dyno cell.

Some more reading on the subject: http://www.kiwibiker.co.nz/forums/sh...post1130292202

[Frits Overmars]

Could someone share how they manage to get an accurate port map?

There is no such animal. Port maps are only accurate to the nearest millimeter which is not nearly good enough, they show distorted port widths and no directional or axial angles at all. Port maps are fine for establishing the number of ports, and not much else.