ESE's works engine tuner

[speedpro]

I've checked my MB100 engine and the slug of air clearly makes it about 60mm down the port and just into the flange

[AndreasL]

Good fun to see all this homemade LC cylinders.
To be a bit clearer about "the reasons" not to LC, the main two things is lack of time (I try to be realistic here. Not my strong part normally.) and that it would be nice if it was not to obvious that a lot of things was VERY modified.
Ideas of how to hide/camouflage a radiator on a simple 1957 moped is most appreciated. So in reality its just really bad excuses for not doing it...

Cooling only the head I have seen one guy doing to this specific engine with great success as well. (He made a billet one and runs it thermosiphon)
Thanks for all the good advice. I will have it in mind.

Frits,
You have a really clever frind I hear. I think his analysis of the real world is spot on.
Getting the owner of the bike to take it appart may be a bit hard. Not that hes not capable, but it runs so d**n good I think he vill leave it as is.
A great pitty, but I will tell him what you suggested.
Get a R/T or a 50SX for my old excuse for an engine is out of the question im affraid. 40x40 cylinder studs and every thing tiny tiny...not the best to start with. I will pause the old hat rant now Frits before you

[seattle smitty]

Hide the radiator, Andreas? Why?? Wear it with pride!! Or hide it the way it's done on cars, with a grille. Last night I saw a 1958 Edsel; now THERE's a grille for you!!

More seriously, does anyone know of a surface treatment (for Andreas' cylinder and head) that promotes heat dissipation? I think it was in the early Fifties that the Germans found that if they painted their cooling fins silver they had to increase the fin area by nearly 30% to get the same heat dissipation as they had got with black paint (flat black? gloss black? the article didn't say). Is there something better than ordinary high-temp black paint for this?

Meanwhile, Prof. Frits, yes that was very sloppy writing on my part (about "cooling" the slug of air/fuel, and about forgetting the relationship of surface area to volume as volume increases). One of the few useful things you can get out of a Liberal Arts major is the habit of editing your own work. The best profs insist on VERY careful editing, and each and every spelling error, typo, or grammar gaffe after the first one costs you one letter grade on your paper, before they start grading it on content.

(Here's a funny thing; my awareness of the relationship of volume to surface area, and surface cooling, originally came to me from reading about evolutionary zoology, you know, mice with (relatively) lots of surface and elephants with much less).

Has anyone had a ceramic coating applied to the interior of an expansion chamber? Does carbon stick to it and build up, as it does on un-coated pipes?

[Frits Overmars]

Meanwhile, Prof. Frits, yes that was very sloppy writing on my part (about "cooling" the slug of air/fuel, and about forgetting the relationship of surface area to volume as volume increases). One of the few useful things you can get out of a Liberal Arts major is the habit of editing your own work. The best profs insist on VERY careful editing, and each and every spelling error, typo, or grammar gaffe after the first one costs you one letter grade on your paper, before they start grading it on content.

I don't care about spelling errors and typos, let alone grammar. After all I'm a Dutchie trying to get by with English here and struggling with German on an other forum.
I merely wanted to point out that formulating correctly will help you think straight.

Has anyone had a ceramic coating applied to the interior of an expansion chamber? Does carbon stick to it and build up, as it does on un-coated pipes?

Yep, well, sort of. I've seen pipes getting treated internally with enamel and I'm not sure if that qualifies as ceramic or rather as glass.
I expect that there will be less build-up because the inner surface is smooth and possibly hot enough to burn off the carbon.

[seattle smitty]

Understood, sir! And thinking straight would be a novel experience for me.

Wobbly, I have a question for the pipes ace. A MOTORCYCLE question, for a change:

I hope you will explain this to me, because I have never got a response to this question anywhere else.

In the early Sixties, I was racing a 250cc Konig inline two-cylinder alky-burning outboard. The factory pipes in those days (and I still have them) look laughably crude and ineffective next to the modern-looking fat expansion chambers of several years later (our Seattle-area boatracers' term for expansion chambers in those days was "bounce-pipes"). Anyway, these early-generation chambers had a single-angle, very shallow angle diverging cone, which terminated in a nearly flat baffle (with a long, largish-diameter stinger). There was no parallel section at all. As you can imagine, with that almost flat baffle there was no doubt about where the pipe "came in." Of course, the poor little engine only made about 37hp max, so it didn't exactly jerk the wheel out of your grip.

By 1976, the year my Yamaha RD400C was built, those skinny pipes with their flat baffles were long-gone from racing, . . . but if you looked inside the chrome-plated shell of one of the RD400's factory exhausts, you found a pipe that was just like those ancient racing pipes: a single-angle shallow megaphone capped with a very flat baffle "cone." Yamaha, by 1976, knew a whole lot about pipes. Why did they pick that one (other than the fact that, being real skinny, it wouldn't likely be dragged on the ground much by ordinary riders)?? Was it because they wanted the rider to get a charge out of feeling the pipe come in (the flat baffle), without the power coming on so hard that the front wheel would loop over his head (the shallow diverging cone)?

I never have ridden the bike much, even after upgrading the shocks and other fixes usually applied to RDs. But the chrome shells over the factory pipes look pretty bad, so I thought I might weld up some new and possibly better pipes. I don't want any of the aftermarket pipes, because they are specifically "performance" oriented, whereas I am an old man who mostly just wants to go putt-putt down the road, seeing the sights. An old, garden-variety 4-stroke twin would be far more appropriate for my riding, but I'm a 2-stroke guy for better or worse.

So my notion was to come up with a pipe of the modern style, but a lot less hyper. A two or three-angle diffuser, but shallow angles, so that the center section of the pipe might be an inch and a half smaller in diameter than a pipe you would build for a wild young rider. AND this pipe would have a long, mild-angle baffle cone, one that specifically does NOT come on with a bang. I haven't worked it out on paper, but this pipe might not even have a straight section in the middle.

This is the pipe I would have, in my ignorance, supposed that Yamaha might have selected for the RD. Would you explain to me where my thinking is wrong here?

(P.S.-- Rather than making two pipes of this variety, I'll first try just one, coming out of a short-coupled 2-into-1 header. This has been very common in outboard racing; doesn't cost a whole lot of power, and does save weight that works against you when you throw the boat into a turn).

I am very eager to hear your answer!!!

[wobbly]

I did not know what was inside the Yamaha pipes of that period ( I simply took them off ) but I do know the history and dynamics of the same type of system in karting that was called a "plate pipe ".
This was used in direct drive applications starting early on with chainsaw derived engines, and later with the early versions of Yamaha KT100.
In this scenario what is needed is a wide flat torque band, with very low peak Hp number.
The instant you try to create anything like decent power the air cooled system becomes thermally limited and the engine suddenly power fades and detoes to death.

The shallow diffuser does not create much negative pressure ratio around BDC, thus does not overscavenge the poorly configured transfers.
In the chainsaw engine these were simply drillings in from the side with capping plugs pressed in to cover the holes.
The kart pipes did have a long parallel body that also formed a resonant chamber that suppressed noise ( high frequency ) but at a set point ( variable for differing tracks )
was a flat " reflector " plate.
This distance down the pipe of the plate would be the mean reflection point of a real rear cone setup.
Being a flat plate it did not have the effect that a convergent cone would have - that is a long duration ,low amplitude return wave that by its very nature has a detrimental effect
on power each side of the tuned length rpm, due to that long duration return pulse being incorrectly timed.
At low rpm most of the long return pulse is way too early, at high rpm most of the long pulse is way too late.

A simple flat flat plate returns a very short duration "ping " if you like that has limited effect, even at its tuned length due to its super low duration - and each side of the tuned rpm it has even less effect
than that you would see from a cone.
This system gives exactly what the direct drive kart engine, and the Konig needed to get out of turns at low rpm, but then also the ineffectiveness of the tuned length also allowed the engine
to rev well past its natural peak power rpm.

Lastly you mention a big stinger.
This is exactly the same scenario as we use in very fast jetski engines.
Again, to reduce the effectiveness of the pipes tuned length at low rpm we kill the pipes efficiency by dropping the system pressure with a big stinger.
This again reduces the amplitude of the wrongly timed reverse pulse - and the engine makes more power down low.
As it comes into tune we then dump water into the stinger with a solenoid controlled valve - thus the system pressure gradually rises back to the point where
it would be with a correctly sized bleed off pipe size.
The big stinger in the Konig and the Yamaha, would also reduce the flat plates tuned length effectiveness.

Kart engines later made much more power over an even wider band with a rear cone full of holes, surrounded by the main body or muffler.
When that volume behind the cone resonates with the forcing frequency of the port timing, the holes almost disappear.
This system called a Vevey pipe has an even wider, higher torque band above and below the natural tuned length than a flat plate or a "proper" cone could hope to achieve.
This is due to having 4 parallel systems that can be tuned to have different effects, the TL, the number of bleed holes and their position, plus the tuned volume behind the cone and the diffuser length.

[F5 Dave]

Dave, you have a really high-volume water jacket there; my notion was to keep the volume small and go for faster-moving water . . .

Actually I don't but it looks that way (esp the photo angle). The 'through' studs make the barrel square. The jacket is 10mm at most except around the ex where it is shorter but deeper to make about the same x section.

[seattle smitty]

Dave, the observation you quote from G. Jennings at the bottom of the post applies all too well to my own intuition . . . .

Wobbly, I remember those early kart engines (McCullough, West Bend, Homelite, Power Products), pretty sad designs by later standards, yet as I recall it, karting in this country was never bigger or more enthusiastic than in those days, the early to mid-'60s. One of the small side-benefits for a few of us outboard racers was the work the karters did with Tillotson in getting kits to convert those little pumper carburetors for use with alcohol, and they came up with some imaginative reed block designs as well. Later, as I mentioned elsewhere, when the karters started using more modern looking expansion chambers on their Italian and Japanese engines, some of them had sliding baffle-cones, adjustable in the pits (they couldn't easily slide the entire pipe, as outboarders can).

I understand the part about the shallow diffuser, though I had not related it to the tiny Mac ports, which makes sense. But my RD has far better ports for a pipe to draw through, as you have no doubt proved to many RD-owning customers. You also suggest that one of the constraints on the factory in designing a pipe for a production street bike is that it has to be extremely reliable, and not ever operate anywhere near the onset of detonation. That also makes their choice of that pipe seem more reasonable, as does the reason I thought of, ground clearance.

But I still don't quite grasp the reasoning on the flat baffle. Everything else on the pipe gives a wide, flat powerband, as you'd want (or anyway, as I want) in a street-only bike. But the flat baffle has a narrow effective range. I would have guessed that a long-duration baffle (i.e., a long-taper cone) would go well with a long-duration diffuser. But I'll read your answer a few more times, and maybe I'll see it. I've been reading a ton of info from the Aprilia designers on another site, and there have been a few assertions by them that only made sense to me after I had gone back days later, read them again, and again, and finally had my "Aha" moment of clarity.

Anyway (hoping my description was reasonably clear), what's your reaction to my basic idea for a new, mild pipe for my RD? I'll build in some adjustability of lengths for testing, then finish-weld to whatever configuration seems to work best (or least badly!!). I'll put a somewhat bigger diameter stinger than you'd use for racing, to keep the piston cool. And it will be muffled. I don't know why I didn't finish this thing long ago, because I made the header and cut out and rolled some of the cones. And I did a pipe like this, as single pipe, for another guy with a little RD125 basket case bike. He seemed to like the result, but he had never ridden the bike with the stock pipes, and had even less riding experience than I do, so his opinion didn't carry much weight (his pal did the jetting and retiming for him).

A couple of things on this job: I have to do a little engine work anyway, so I'll get the squish down to about .85mm to avert any detonation. I'll keep the little factory carbs, though I might try using just one, with a 2-into-1 intake, for simplicity and an easy-going wide powerband.

I won't be inviting any other RD owners to look at my alterations; they'd denounce me as a pussy, and have no more to do with me!!

(EDIT) So far, googling gets me nothing on Vevey pipes. I'd like to see a photo or drawing, maybe it's something I can use. Got a link?

[AndreasL]

Smitty, will be interesting to see what you come up with.

I'm in no way an expert (as you already know) but I would try to get a little tighter on the squish.
0.7 can't be a problem with the kind of revs you will be using?
One carb might sound simpler at first and might work perfect for your application.
But doesn't it get a bit complexed in a 2t twin with the intake pulses from one cylinder mess up the jetting? I don't know, that's why I ask. Old 2t cars did run single carb 2/3 cylinder engines when thinking about it. Hmmm

For me I have always looked at one throttle per barrel as a great plus. But nothing more then car related 4 strokes to base that opinion on.

[seattle smitty]

Google "konig 4-cylinder," the Images section, and see no end of weird configurations. Dieter Konig built engines both for outboard and sidecar racing. He also built some motors for ultralight aircraft, eventually was killed in one.

[wobbly]

The problem with a long slow angle rear cone is that it returns a pulse ( though of low amplitude ) over a very wide band.
Thus in effect it "affects " the engine even more when well outside the tuning range of the mean reflection point than a shorter steeper design.
Taking this concept to the extreme, a flat plate "works" over a super narrow range ( and even then its not that effective due to the super short duration period )
and does virtually nothing outside the TL rpm.
Here is a pic of a "Vevey" type pipe as modelled in EngMod, and this system works supremely well in exactly the scenario you are looking at.
I made several for Yamaha fan cooled engines used in small aircraft, with a 2:1 header - tuned to just 6000 rpm.
They need a very wide torque curve to enable them to spool the prop up, and then overev when needed.
A very similar end use to pushing a prop thru water, and having trouble reaching planing speed.
Also a pic of the drone pipe as I called it - with a nice stainless racebike pipe for comparison.

[F5 Dave]

Google "konig 4-cylinder," the Images section, and see no end of weird configurations. Dieter Konig built engines both for outboard and sidecar racing. He also built some motors for ultralight aircraft, eventually was killed in one.

Google Kim Newcomb; an employee at Konig who put one in a GP bike. . eventually was killed on one.

ps you'll doubtlessly have to machine the chamber as it will be too small when squish correct. 2-1 carb will have a long manifold. Some kits exist for Banshees but diff to early RD & why?

[AndreasL]

1kg of red Vinamold arrived today. Will last for every possible duct I will ever want to mould.
Will be interesting to see how bad especially the transfers are.

[wobbly]

The RD stud pattern went back to first R5 twin and was used on all subsequent RD versions - ending in the 400 that had an identical case but bigger flywheel diameter
to take the 62 stroke..
The Banshee is based on the RZ - stud pattern is completely different.
The RD400 stock head has super low compression, dropping the squish to even 0.7 will still be safe as houses on unleaded, trouble is the squish angle is
all wrong so this needs to be corrected as well to do it properly.

[husaberg]

(EDIT) So far, googling gets me nothing on Vevey pipes. I'd like to see a photo or drawing, maybe it's something I can use. Got a link?

They get a mention in the bellbook can't remember what though.....