ESE's works engine tuner

[Frits Overmars]

neither of us should ask Frits for advice on this old junk we're fooling with.... It would be like asking Colin Chapman how to hop up your flathead Ford.

I like the comparison, although I feel much more alive and kickin' than old Colin does nowadays.
Of course I've been asked by classic-racing friends to take a look at their bikes. But it is usually frustrating; there's no material where you need it, you're not allowed to do what you deem necessary, and if you finally happen to generate some more power, the cooling system can't cope with it, so the bike seizes and I get the blame.
So no, thanks.

Using a drill press might be rough, but it was very effective at opening up the rear ports, I highly recommend it.

That's the way I attacked my first moped cylinder about a century ago .

[AndreasL]

One thing I should have said, Andreas, is that neither of us should ask Frits for advice on this old junk we're fooling with. He has stated that he has no personal interest in thirty year old 2-stroke tech, which you can easily understand. It would be like asking Colin Chapman how to hop up your flathead Ford. Frits directed me to the French "Pit Lane" site, and if you go there and work your way through the archived tech threads (I'll need to do this multiple times, taking copious notes), pretty much everything you need to know is there. When the tech masters like Wobbly offer us a tip or two in our efforts to make a silk purse from a sow's ear, we're lucky, and really shouldn't expect such favors. WE have to figure stuff out.

Totally agree smitty and as you say, fully understandable.
Thats why I try to post as general as possible so as many as possible can gain from the knowlage the gurus so kindly share with us.
So I'm more then happy that Wobbly gave me some directions to try out as a start and why this might be good. The rest is up to us.

Have read the RSA threads at Pit Lane but hear I need to lurk around some more. Thanks!

I like the compartison, although I feel much more alive and kickin' than old Colin does nowadays.
Of course I've been asked by classic-racing friends to take a look at their bikes. But it is usually frustrating; there's no material where you need it, you're not allowed to do what you deem necessary, and if you finally happen to generate some more power, the cooling system can't cope with it, so the bike seizes and I get the blame.
So no, thanks.

Not half the man in "my disipline of motorsport" compared to you Frits. Still people sometimes asks for advice etc etc. So I think I know what you mean.
No blame on you when I blow my engine.

One small question though if I may...
Since I use a "thermally unsound" engine I'm interested in how to approach the stinger/venturi in your baseline pipe calculations.
Fit a waterpump?
Or make the stinger the dimension sugested but without the venturi part?
EngMod tells me that the venturi gives some nice gains, but probably at the cost of the engine. (We have been warned!)
Guess that "Max Unburnt Zone Temp" and "Cylinder Temp" is the ones to look out for when trying different dimensions?
This baseline calcs have been very usfull to get me going so I owe you a couple of truckloads of

TeeZee, yes, something bad enough to feel comfortable its as bad as our own hacks would be nice. LOL

Thanks all for posting!

[Frits Overmars]

Since I use a "thermally unsound" engine I'm interested in how to approach the stinger/venturi in your baseline pipe calculations. Fit a waterpump?

Waterpump? From the description of your engine I gathered that it would be cast-iron and aircooled. But if it's watercooled, by all means fit a pump.
And as Wobbly pointed out, match the angle.areas for blowdown and transfer, and do not try to run higher revs than the blowdown is good for, otherwise spent gases entering the transfer ducts will rapidly overheat the cylinder.
Stinger-venturi: I can't give you a size. Just start big and work your way down, carefully watching the temperature. You may ruin a piston anyway, but you will get the experience.

This baseline calcs have been very usfull to get me going!

Glad to hear it; that was exactly my intention when I published them. Mission accomplished.

[TZ350]

Attachment 304983Attachment 304982

Using a drill press might be rough, but it was very effective at opening up the rear ports, I highly recommend it.

That's the way I attacked my first moped cylinder about a century ago .

Team ESE bringing you yesterdays technology today .....

[seattle smitty]

Andreas, I have a '73 Yamaha 125 MX cylinder, bought new that year to turn into a racing outboard motor. Since we have a whole lake full of cool water that we can ram (usually not pump) into our engines, we actualy are able to over-cool some engines, as bikers and karters cannot. One of the decisions to make was how to shape the waterjacketing that would surround the cylinder after I milled off the air-cooling fins. You have what's left of an upper and a lower fin to form the outer edges of the waterjacket, which you creat by shaping a piece of 6061 sheet aluminum that wraps around these two stubs of fins, TIG-welded. That's pretty straightforward and obvious. What is less so is the stubs of the in-between fins; when you ran your milling cutter around the cylinder, cutting away the fins, what's left of them are all the same length because of your straight-sided miling cutter. Now, what do you do with these in-between fins? Of course you make notches or holes or whatever to get the water to flow through all of them . . . but do you really want them at all? These mostly milled-off fins still provide a whole lot of surface area in a water-cooled context. My thinking was that they would be TOO effective, given that steady supply of cool water a boatracer has, so I took a grinder and rotary file and removed most of those intermediate fins. I did leave them alone in the area around and above the exhaust port; in fact, on all my outboards I set up the water inlet(s) so as to flow the coolest water over the exhaust port area FIRST to scrub away steam bubbles.

Or I should say, that's the way I USED TO do it; haven't done any of this in decades. But I'm giving it all one more shot.

But if you do decide to convert to a water cooled system, you don't have a lake full of cool water, but a closed system of limited capacity which will get pretty warm. So in your case, you might need plenty of surface area left inside your waterjacketing.

When some of us outboarders were fooling around with this, all with early '70s piston-port or reed induction Yamahas, somebody cast up some water-cooled heads that we all used (though I also made a couple of heads from billet). It was soon found that you could get enough cooling to run the engine hard by cooling either the head alone or the cylinder alone; you didn't have to cool both. My feeling was that the cylinder is where the piston sticks, and the head is where the power is made, so if I'm only cooling one, it will be the cylinder. I could have used my water-cooled cylinder with the factory aircooled head . . . except that we were burning methanol, and felt that to take full advantage of that fuel we wanted a tighter combustion chamber. I started trying to weld up a factory head, but maybe it had a bunch of zinc in the alloy because I made a mess of the job. But again, in YOUR case, I think you'd want to make a water-cooled head AND cylinder, if you go that direction at all.

Compare notes with TZ350, who is experimenting with ducts and baffles for his air-cooled machine. Of course, his is a racer; ducting won't help if you get stuck in a traffic crawl. I still like my idea (pride of authorship?) of welding some fins on the header pipe of the exhaust to add surface area and cool the slug of A/F that is drawn out into the header until it is shoved back into the cylinder with the reflected wave. It was pointed out that this could cost a little power by cooling the exhaust gases. Maybe so, but you can't win a race if you don't finish. I'm thinking that the header needs this minor amount of cooling, while the rest of the pipe, downstream from the header, should be insulated with a ceramic coating. The large-diameter areas of an expansion chamber are surely where the major heat loss occurs.

[Grumph]

Stinger/Venturi size - I can't give you a size guidance either but I can tell you that going down in .5mm increments shows improvement very quickly. It shows on the plug very quickly too. Once judgement shows you may have gone too far - and if you've been lucky/experienced enough to catch it before damage is done...Then very much smaller increments of size come in.
Without a dyno or instrumentation going smaller than the last safe .5mm step is not worth it.

[AndreasL]

Thanks Frits.

Sorry for confuce you with the water.
Its all cast iron and aircoold here.
Thought the correct answer to ALL questions about aircoold engines was "Get it watercoold!"

As for a fixed number for the stinger I understand that cant be given. I will watch my temps trying different venturis.

Realise I need to find some more information regarding how to quantify blowdown (STA?) in relationship to rpm to have a better feeling for when its running out of steam. Probably this can easily be seen in EngMod when knowing what to look for. More to study. Nice!

[wobbly]

Once you have a well functioning sim of your engine and have run the Turbulent Entrainment model for your combustion Wiebe parameters
the data feedback from TubMax is super accurate.
Getting the advance and stinger dimensions on the money to have this figure sitting on mid 900*C without WARNING - DETO - WILL ROBINSON screaming at you from the screen.
It is good enough to take those numbers direct to the dyno in the knowledge it wil not explode as long as you are watching the instrumentation religiously.
But - there are some very old guidelines that still work remarkably well today.
Take as an example the RG50 T port cylinder I am working on at present.
It has a 75% duct exit area at the flange = 24mm oval area.
Take 0.58 of this diameter and we have 14mm, what is in the sim right now - 13.7mm with 18Hp at the crank.
Thankyou Kevin Cameron.

[peewee]

hey guys i thought maybe this was discussed somewhere before but i dont remember. if you were to make a inline twin with reed block in the front of the case and turn the cylinders backwards, would it be best to have the crankshaft also spin in reverse so the rod and crankwheels are going the same direction as inlet flow or would it make much difference which direction the crank rotates ?

if the top of the crankshaft was shielded (just a slot for the rod), would that make any difference in which direction is best for crankshaft rotation ?

[AndreasL]

Looking through my own notes from 28th of October (Yes, 5 days ago) I find the following recommendation posted by Frits:
"Blowdown: 8.72*mm^2/cc_tot/1000 rpm" <--- Me

But I must have got something wrong here or its just that the numbers are derived from the RSA and therefore not realistic to reach with a old engine?
Or maybe I have misunderstood it all together. Not the first time...

Thanks Wobbly, I really appreciate it.
Have not come to run turbulent yet but hope to get there soon.

EDIT: Sorry all others making post regarding watercooling and stingers. I did miss it somehow.
Watercooling, either the way smitty sugest (I have seen pictures of an old cylinder like mine having this treatment done in the 70:s), or going modern. But dont think this will ever happen due to a lot of reasons.

BUT after visiting a friends house last night and listening to a watercoold Stage6 R/T fitted to his old Zundapp I am tempted for something as brutal. I can only say WOW. 75cc, custom 44mm crank from Roffe (With the Derbi/Honda you know) and a tell tale reading of 15007rpm from the last outing around the block. Super low exhaust duration (167° when run 39mm stroke/85mm rod IIRC) and pulls from ~1rpm. Yes, STA is what counts but still its hard for me to understand how to get the needed blowdown etc with such low timing. A lot of users having hade great result with that one on all kinds of engines. If I had the time I would try to do a sim to see if its realistic or his tacho is reading way off. But nothing for Buckets I guess since its marked "Racing". Sorry for the detour.

[wobbly]

Running the crank backward will loose power in the gears needed to correct the rotation - more I would guess than any created by having
the "correct" flow rotation.
Having the flow running with the flywheel direction of spin is worth power but then so is shielding the intake flow from the wheels
when an "exit slot " is cut to radially direct the little boundary layer movement there is,up under the piston.

[peewee]

Running the crank backward will loose power in the gears needed to correct the rotation - more I would guess than any created by having
the "correct" flow rotation.
Having the flow running with the flywheel direction of spin is worth power but then so is shielding the intake flow from the wheels
when an "exit slot " is cut to radially direct the little boundary layer movement there is,up under the piston.

im not sure what your saying. if the reed blocks were mounted at the front of the cases, cylinders turned backwards, sheilded crankshaft wheels with slot for the rod, then i should be just fine with a standard forward spinning crankshaft ? thnx for the help by the way

[F5 Dave]

. . .

BUT after visiting a friends house last night and listening to a watercoold Stage6 R/T fitted to his old Zundapp I am tempted for something as brutal. I can only say WOW. 75cc, custom 44mm crank from Roffe (With the Derbi/Honda you know) and a tell tale reading of 15007rpm from the last outing around the block. Super low exhaust duration (167° when run 39mm stroke/85mm rod IIRC) and pulls from ~1rpm. Yes, STA is what counts but still its hard for me to understand how to get the needed blowdown etc with such low timing. A lot of users having hade great result with that one on all kinds of engines. If I had the time I would try to do a sim to see if its realistic or his tacho is reading way off. . ..

yeah a mate used to claim he saw 17,000. most cheapo ones are crazy at high revs and lose the plot by several thousand rpm.

[AndreasL]

yeah a mate used to claim he saw 17,000. most cheapo ones are crazy at high revs and lose the plot by several thousand rpm.

This was a KOSO one. Popular with the scooterkids but dont know for sure how accurate they are.
15krpm sounds high for this engine even if its full off nice bits. Anyway, it runs great trying to throw its rider of even in 5th gear.

[seattle smitty]

If one of "the many reasons" for not converting your cylinder is that it's cast iron, you could still mill the cooling fins down and braze the sheet steel wrapper to the periphery of the upper and lower fins to complete your water jacket. Actually, you only are milling down probably the top four fins; any fins below that are left alone. The first of those fins you left alone serves as the lower wall of the water jacket. At least, that's how I did it.

And don't paint over your brazed joints; you want to make sure everybody sees these weird homemade mods!! And then when you go for a ride on your scooter, wear a pair of those party glasses with the eyes in them that blink open/closed/open as you nod your head up and down, oh and mount a model airplane propeller on top of your helmet, spinning in the breeze . . . . Scooter riders and recumbent bicycle riders should be natural collegues.