ESE's works engine tuner

[Frits Overmars]

...those old, short, piston-fed boost ports are nowhere near as effective as a modern full-length C-port fed from the crankcase area.

That is true if you look at transfer flow. But from a cooling perspective, scavenging through the piston does help.

Suppose you take a modern (okay, Aprilia) cylinder with full-length C-port, AND have a hole in the piston, at the old location under the crown and ring, flowing into the side of the C-port, roughly halfway up. Would the very good flow and velocity of the modern C port draw strongly from that hole, and really have a good effect on piston cooling.

It might work, and it might help cool the piston. But at the same time it would raise the average temperature of the fresh charge, so it would be useful only if piston temperature is a limiting factor in that engine.

And if this would work to good effect (piston cooling) on an Aprilia or similar cylinder, could it not be even better if applied to Frits' FOS concept, with its ring of transfer ports? Maybe you could have two or four holes (in a piston structurally designed for them) each one feeding one of two or four transfers, creating a cooling outflow under the piston crown.

Theoretically, yes. But where should I put those holes? They must not run over the exhaust windows, which leaves only the areas fore and aft (the exhaust ports are on the right and left sides). But mid-fore and mid-aft there are no transfer ports because I reserved those areas for the piston to lean against, and for the ring gap.
The picture of the cut cylinder below shows the available areas for piston cooling windows in red. But I'm not sure whether I want to make four holes in a piston that will be very highly stressed once the rpm potential of the FOS porting system is fully exploited.

[Frits Overmars]

That reminds me ages ago I said would post some pics of the TD1C Port slots. No use these days, but more for giggles.

Giggles indeed: I wonder if they really fitted that cylinder upside-down back in 1967.... .

[TZ350]

Okay, I have an idea. Maybe old-hat, but I haven't seen it discussed:

In the early era (MY era) of loop-scavenged 2-stroke bike motors and outboards, the boost-port (or as it is now called in discussions of more modern engines, the C-port) was not very wide, and was VERY short in length because it had to fit above a piston-ported intake tract. It was fed from a small matching hole in the piston, close to the crown and just below the ring. Nobody expected more than a small contribution to power, but it was thought that any A/F mixture flowing through the piston, under the crown and out the hole and into the boost-port should have a cooling effect on the piston crown. To what extent this was actually true, I don't know. Some people theorized that as the piston slowed as it approached bottom-center, whatever mixture that was trapped inside the piston tended to be accelerated out of the bottom of the skirt, so that there really was not much in the way of A/F remaining in under the piston crown for the boost-port to access, or to cool the crown. (FWIW, my personal experience with these very short, piston-fed boost-ports came from my 1963 FA Konig 250cc racing outboard).

However, I wonder if a combination of old and new could be better yet. Suppose you take a modern (okay, Aprilia) cylinder with full-length C-port, AND have a hole in the piston, at the old location under the crown and ring, flowing into the side of the C-port, roughly halfway up. Would the very good flow and velocity of the modern C port draw strongly from that hole, and really have a good effect on piston cooling (any power effect of accessing mixture trapped under the crown would be incidental, piston cooling being the chief motivation).

I have been working on that C port piston hole and proper transfer duct combo for direct cooling of the underside of the piston crown and would be interested in other peoples experiences with the idea too.

Attachment 289789

I am trying to get the injected fuel to squirt up inside the piston crown for cooling of the piston top from the underside and better fuel vaporization.

I am hoping the EFI system will give me more under piston cooling and by being able to control the fueling more accurately some reduction in detonation during over rev (13,000 + rpm). With the carburetor set up, over rev and part throttle deto is a real problem.

Attachment 289786

Attachment 286286

The boost port is mostly cut into the crankcase on the magneto side.

Attachment 286283

The magneto side needs gluing up here, I didn't bother with the carb crankcase side as you hardly cut into it.

Attachment 286287

The original boost port was just a trench in the rear wall of the cylinder, now its more or less a proper port and duct.

Attachment 286288

[peewee]

The RD400 based rods are narrower,thus would need spacing with another washer if used in a Banshee/RZ based crank.
I use rods that were made to my specs by Wiseco after they were fired by Kurt of Hotrods.
They had an international marketing exclusive deal, that Wiseco typical of them botched completely.
Not long after the deal collapsed, the CEO that had caused all the drama was fired, and I ended up with a box of really good sample rods
with no identifying markings, but they were made by Taiwans best rod/crank maker Shunchi.
At the same time I got some Peek coated flat race cages done to go with them.
Cheap and bulletproof and plug and play - the best combination known to man.

ill let you know which direction i go. not sure i want to tie up $500 on rods if $250 will get the job done just fine. but still kicking around ideas. appropriate thickness washers are easily available as several other engines used them, if i decide to use a slightly thinner rod.

do you have complete sets of unassembled crankwheels also or just the rods ?

[husaberg]

Giggles indeed: I wonder if they really fitted that cylinder upside-down back in 1967.... .

Never noticed that lol, back to front....
In addition to your answer above to smithy, the area above the gudgeon on the modern cylinders is rather smaller than the older designs like this below. That has acres of real estate available above the pin and on the cylinder walls (An old Greeves Silverstone. )
I note also all the older style pistons have the gaps either side of the windows rather than the middle of the c port although not sure if it would matter or not.



Smithy compare, this above, to some of the space available these various Aprilias (below)


Ps as I have already pm'd Pewee I think the KTM200 rod would be a good start as it is 118mm long and seems to be Yamaha sized.

[seattle smitty]

[QUOTE=Frits Overmars;1130798068] It might work, and it might help cool the piston. But at the same time it would raise the average temperature of the fresh charge (end quote).


I keep forgetting you guys run gasoline. Why don't you switch to real racing fuel? Gasoline is for cleaning parts.

Frits, I sure have a hard time wrapping my pore 'ol brain around that damned engine of yours!!


Husaberg, thanks for the enlightening photos, as always (though I wish you had one with the short little boost-port above the piston-port intake, like I was describing), but it's SMITTY, two t's, not "Smithy." Smitty is the traditional American form, while I understand Smithy is the Brit and dominions style, yes?


Back to Frits, how do you think about the trade-off between a cooler A/F charge being more dense versus having a warmer charge that keeps the fuel in suspension better, with less in the way of big ugly drops of liquid being slung off the upper edges of the ports? Car guys think about this a lot, HEAVY liquid fuel being slung out of the less-heavy air against the outside turns of the runners and ports. When I was young and dumb and handsome, and racing with methanol blends, my notion was that ideally I wanted cool, dense air getting mixed with fairly warm fuel.

(I should have stated an additional advantage of my idea, that it should lubricate the small-end bearing better than usual).

[husaberg]

[QUOTE=seattle smitty;1130798210]

It might work, and it might help cool the piston. But at the same time it would raise the average temperature of the fresh charge (end quote).


I keep forgetting you guys run gasoline. Why don't you switch to real racing fuel? Gasoline is for cleaning parts.

Frits, I sure have a hard time wrapping my pore 'ol brain around that damned engine of yours!!


Husaberg, thanks for the enlightening photos, as always (though I wish you had one with the short little boost-port above the piston-port intake, like I was describing), but it's SMITTY, two t's, not "Smithy." Smitty is the traditional American form, while I understand Smithy is the Brit and dominions style, yes?

the Greeves pic I posted has one.

Ah, when I put my forehead against the screen, I can see it; sorry.

click on it a few times it gets bigger........

[seattle smitty]

Ah, when I put my forehead against the screen, I can see it; sorry.

[richban]

Hi Guys

As some of you know I have been developing my 300cc NSR. Next weekend see's its first proper racing at Hampton downs. Its going really well except the pipes are cracking and braking all the time. They are SS no surprise. They really do cool very quickly and obviously heat fast as well. I was wondering if lagging the pipes for the first 300mm is a good idea to keep a bit of heat in there and not let them cool so fast. Will this help with the cracking yah reckon. Also could it help with throttle response. The pipes are the next thing to come but will not be made till after xmas.

Any bright ideas welcome. Cheers Rich.

[mr bucketracer]

Hi Guys

As some of you know I have been developing my 300cc NSR. Next weekend see's its first proper racing at Hampton downs. Its going really well except the pipes are cracking and braking all the time. They are SS no surprise. They really do cool very quickly and obviously heat fast as well. I was wondering if lagging the pipes for the first 300mm is a good idea to keep a bit of heat in there and not let them cool so fast. Will this help with the cracking yah reckon. Also could it help with throttle response. The pipes are the next thing to come but will not be made till after xmas.

Any bright ideas welcome. Cheers Rich.

years ago on pre 95 rs hondas guys used to put beads of high temp red silacon around the chambers to take the zing out of them to stop cracking , the promblem was the rubber mounts but it did work not to bad but looked crap

[speedpro]

I'm not sure how the SS works as I've never had a SS pipe. As with nearly everything I've owned, if the pipe was cracking the cure was to mount it so it was free to move around while still supported. You probably already on to that idea.

[Frits Overmars]

Why don't you switch to real racing fuel? Gasoline is for cleaning parts.

Yeah, and alcohol is for drinkin'. So what have we got left? Nitromethane? Or should we go straight to nitroglycerine? Or TriNitroToluene? Oh no, that's not a liquid. Hydrazine maybe?

Frits, I sure have a hard time wrapping my pore 'ol brain around that damned engine of yours!

And it's so simple. there is one bridged exhaust port, with its twin brother opposite, and there's just one shape of transfer port, not five different shapes as in conventional engines. Everything is symmetrical, which by the way ensures that the bore will always stay round and straight and not go banana-shaped as in present-day engines.

how do you think about the trade-off between a cooler A/F charge being more dense versus having a warmer charge that keeps the fuel in suspension better, with less in the way of big ugly drops of liquid being slung off the upper edges of the ports? Car guys think about this a lot, HEAVY liquid fuel being slung out of the less-heavy air against the outside turns of the runners and ports. When I was young and dumb and handsome, and racing with methanol blends, my notion was that ideally I wanted cool, dense air getting mixed with fairly warm fuel.

You only offer two choices for that trade-off; I prefer a third option: that the mixture is cool because all of the fuel is evaporated. That requires a carburettor delivering fine drops to begin with; then it takes some time and some stirring which is taken care of by the crankshaft, cooling the conrod in the proces. And finally it depends on the fuel. Unleaded petrol (gasoline for you 'Mericans) is pretty good. Heavy fuels like the toluene that was used in the first turbo-F1 era, are notorious. Honda even specified 85°C for the fuel before being injected.

I should have stated an additional advantage of my idea, that it should lubricate the small-end bearing better than usual.

It would, but I haven't seen small-ends suffering from scanty lubrication in a long time.

[seattle smitty]

(Quote Frits) Yeah, and alcohol is for drinkin'. (end quote)

(singing) "We never stumble, we never fall; we mix our drinks with wood alcohol." The "drinkin'" stuff is for mixing with parts-cleaner, Frits; I'm talking RACING fuel.

Fuels: FWIW, the driver of that Anzani (photo back on pg. 1038) and lots of other outboard racers from the Thirties through the Sixties usually ran anywhere from 20 to 40% nitromethane in the methanol, with a few other fractions, plus castor oil. What I wanted to tell you was that he did try hydrazine. He summed it up for me by saying, "You use half as much (as you would of nitro), but it costs twice as much." This was in the last days of open pipes. When he went to the "bounce-pipes" (what we called expansion chambers), the engine made about the same power without any nitro. And it was hard to successfully run much nitro in a bounce-pipe engine, so everybody got away from it, since it cost a lot and has other issues. About the only outboard racers who still "tip the can" (of nitro) are those who run in the antique classes, or still use old open-pipe engines in a couple of classes in local races.

All racing fuels have their pros and cons, but one handy thing about having no limitation on the fuel you can use is that the people running the race don't have to bother with testing your gasoline to see if you're cheating. Seems like a lot of bother for local club racing.

[seattle smitty]

Wobbly, or anybody who has tried this, tell me about expansion chambers made of aluminum, examples of which I saw on the French site. Since, I assume, they'd have to be made thicker than steel, does the weight savings balance the drawbacks? I assume the big drawback is heat-loss, but maybe that could be largely addressed with a ceramic coating. What alloy and thickness has worked (if any has worked)?

I had a friend in California long ago, John Alden, one of the top outboard engine-builders of the time, who wanted to try making expansion chambers of titanium . . . until the supplier quoted him a price for one 4X8' sheet. That ended that!

[Frits Overmars]

the driver of that Anzani... did try hydrazine.

Is he still alive? And what about the guys that breathed his exhaust fumes?

tell me about expansion chambers made of aluminum.... Since, I assume, they'd have to be made thicker than steel, does the weight savings balance the drawbacks? I assume the big drawback is heat-loss, but maybe that could be largely addressed with a ceramic coating.

Don't do it. There is no weight saving, aluminium (aluminum to you) pipes won't work without an internal ceramic coating, and they will crack despite the increased tickness. Aluminium does that.

I had a friend... who wanted to try making expansion chambers of titanium . . . until the supplier quoted him a price for one 4X8' sheet. That ended that!

Titanium works great for pipes if you use the right grade . But stainless steel is almost as good, cheaper and easier to weld.