Oh, what could have been = Honda's reversed engine EFI 2 Stroke 250r

[troybilt]

Founds this patent from 2000 doing a search on 2 strokes. This looks like what would have been the next generation TRX250r, instead we got the 400ex...

From the pics looks like an inverted reward facing exhaust fuel injected 2 stroke motor. Frame similar to 250r/400ex frame.

http://i74.photobucket.com/albums/i260/robltc/Honda%20Patents/EFI2stroke_Honda_250r7.jpg
http://i74.photobucket.com/albums/i260/robltc/Honda%20Patents/EFI2stroke_Honda_250r6.jpg
http://i74.photobucket.com/albums/i260/robltc/Honda%20Patents/EFI2stroke_Honda_250r5.jpg
http://i74.photobucket.com/albums/i260/robltc/Honda%20Patents/EFI2stroke_Honda_250r4.jpg
http://i74.photobucket.com/albums/i260/robltc/Honda%20Patents/EFI2stroke_Honda_250r3.jpg
http://i74.photobucket.com/albums/i260/robltc/Honda%20Patents/EFI2stroke_Honda_250r2.jpg
http://i74.photobucket.com/albums/i260/robltc/Honda%20Patents/EFI2stroke_Honda_250r1.jpg

[SilverLake250R]

Awesome info Troy! A real shame they abandoned that project...

[derby]

I think you are right troy. Even looks like the angles on a 250r frame, motor mounts, and lower linkage mount. I can't seem to figure out what is turning on the cylinder. Fig 2 & 3 #43

[troybilt]

Notice there airbox where the radiator normally is? Interesting configuration. I wanted to check into reversing a stock 250r cylinder not sure if it is possible or not.

[troybilt]

Just read in the wording that it had an electric start along with kick start.

[troybilt]

Derby, the patent describes #43 as an intake control valve. I this is what i actually patented. It was to solve fuel loss problems.

"Additionaly, the intake control valve 43 is rotatably fitted to the valve chamber 37. The intake control valve 43 is formed with an acurate rich mixture gas supplying recess 44 communicated with the rich mixtures gas supply passage 38 such that it may be opend or closed. At the same time, two pressurizing air feeding recesses 45 communicated with the pressurized air feeding passage 40 such that is may be opened or closed are formed at both sides of the rich mixture supplying recess 44."

[89trx250r]

I have been staring at these diagrams for an hour now in awe...Troy did you find any old stuff from Yamaha or were you only looking into Honda? Reason I ask is I wonder if someone at Yamaha saw these old Patents and said hey! The new yz450f dirtbike has a reverse motor with the intake on the front and the exhuast out the rear it is also efi...Only difference is its a 4 poke...

[troybilt]

I was actually just searching for information out there on expansion chamber design. rsss396 sent me this link to check out and I thought the "slippy" pipe was really cool so I was just seeing what other ideas were out there and came across this patent..

slippy pipe:
http://www.muller.net/mullermachine/docs/slippy1.html

[troybilt]

I'll do some searching and see if there is anything from yamaha or suzuki... This patent references a suzuki patent...

[troybilt]

Derby this is a good read on the rotary intake valve...

Honda's Rotary Intake Valve (http://www.google.com/patents/US6145483?pg=PA1&dq=masahiro+asai+honda&hl=en&sa=X&ei=hnh8ULGqE4W9yQHk94HQDA&ved=0CDIQ6AEwAQ#v=onepage&q=masahiro%20asai%20honda&f=false)

[bhatch21]

What is the catalytic converter looking stuff at 64 and 65?

edit: I see now, the exhaust snakes around under the seat to the muffler (65) and 64 is the coupler.

[wilkin250r]

I wonder how you can get away with a rear-facing exhaust, especially one that straight. Last time I did the rough calculations (years and years ago), I came up with an exhaust several feet long. If it was as straight-line as that photo shows, it would be hanging off the back of the quad by three feet.

Granted, we could easily reduce the stinger length from what we have now, the only reason for it's current length is to allow the muffler to be mounted properly.

[troybilt]

I've actually looked into it this a little Wilkin and visited with a couple builders about it. Apparantly it is possible to reverse a cylinder if you remachine the exhaust flange so it comes out more straight. But from a pipe stand point. Yes it requires a long pipe if you were to take a current 250r pipe and straighten it it would be about a 800mm - a meter long give or take. One thought I had was to corkscrew or tornado the pipe to get the length to work out. I think on this bike the pipe is straight but curves back, but you're right the business part of the pipe seems short... Its a good question I wish we could ask the engineers on the thoughts behind this bike and what happened to it.

Also along pipe theory, has anyone ever done a 1 into 2 pipe? I know the banshee there is all kinds of 2 into 1 pipes. My thoughts were if you did 2 pipes with a "Y" shaped exhaust port, (cost and actual ability to make such a pipe aside :D ) Could one to 2 different tunes for each pipe? basically one side would be a low end pipe and the other a more top end pipe? Both would be about half the volume. Just a random thought I had. Can't say I've read or seen anything that has such a design. I like talking about the theory.

[KM250R-BDTM]

At Selvy’s Performance we built a reverse cylinder 250R and a reverse cylinder Banshee. The 250R was finished and saw almost zero testing, however; the Banshee saw Sand a few times. We (Rob) made ‘Straight Pipes’ and the thing screamed…couldn’t keep it together.

The Straight Pipes made a huge impact on Pipe design & performance as well as tuning.

Building a 250R with a reversed cylinder and a ‘Straight Pipe’ is a side project I would love to follow through to the end this time around.

[troybilt]

Originally posted by KM250R-BDTM
At Selvy’s Performance we built a reverse cylinder 250R and a reverse cylinder Banshee. The 250R was finished and saw almost zero testing, however; the Banshee saw Sand a few times. We (Rob) made ‘Straight Pipes’ and the thing screamed…couldn’t keep it together.

The Straight Pipes made a huge impact on Pipe design & performance as well as tuning.

Building a 250R with a reversed cylinder and a ‘Straight Pipe’ is a side project I would love to follow through to the end this time around.

Well I've got 1 or 2 more frames that I want to do this project with, I'd be on board!

[Rich250RRacer]

I seem to remember Honda having an actual running version of this motor in a prototype CR250 back in the '90s. It was direct injection but I don't believe it wasn't reversed.

[Rich250RRacer]

Check out this article.

http://www.motocrossactionmag.com/KTM/News/REVERSE-CYLINDER-EFI-TWOSTROKE-OSSA-IS-BACK-With-A-3802.aspx

[zedicus00]

in a dark hole in the basement of the R&D labs there are some grey skinned looking builders poking and prodding the designs we know as 2-strokes. no big name willing to release them onto the world first, but no big name willing to give up development for fear of being left behind in case one of their rivals should nut up and release something. the good news, its out there, the bad news, i do not know if it will ever see the light of day. the people who are deep enough in the industry to know the answer to that are not allowed to talk about it publicly.

[troybilt]

"...where we're going we don't need roads..."

[troybilt]

Originally posted by Rich250RRacer
Check out this article.

http://www.motocrossactionmag.com/KTM/News/REVERSE-CYLINDER-EFI-TWOSTROKE-OSSA-IS-BACK-With-A-3802.aspx

Check out the pipe, I didn't see an expansion chamber on there some sort of collector.

I've been reading about direct air injection 2 strokes. no expansion chamber needed there either.

[C-LEIGH RACING]

There was a Banshee raced TT with us in the late 80s, had the cylinders turned around.
Carbs out front & pipes right through the frame out to the rear of the fenders then stingers curved around & the silencers straight out each side.

Rider did right well, little better than mid pack finish, but if any body knows a banshee frame like I do, would know he did real good to finish where he did with that ill handling thing.
Banshee got plenty of power, but aint worth a dang except in a straight line.
Neil

[wilkin250r]

Originally posted by Rich250RRacer
Check out this article.

http://www.motocrossactionmag.com/KTM/News/REVERSE-CYLINDER-EFI-TWOSTROKE-OSSA-IS-BACK-With-A-3802.aspx

Trials bikes are different. They have a fraction of the horspower a motocross bike does, and they run at rather low revs. They don't use expansion chambers because they need a very linear power delivery, and because they simply don't need the horsepower. I think most trials bikes are something like 10-15hp at best.

[ikas]

Picture of a ossa enduro bike.

http://www.mxreview.se/motoimages/ossa-enduro.jpg

[troybilt]

Look at those Ohlins forks and hand coned exhaust, that is the definition of high end right there... nice post!

[fx4pitrone]

Wow.. that is awesome!

[triplejay30349]

this looks to be another step in the right direction.

http://www.youtube.com/watch?v=Y91Jms6MyCY&feature=related

[wilkin250r]

I wonder about all those bends and twists in the pipe, though. I wonder if you could get better performance if your pipe was basically straight.

What would be the benefits of a reversed cylinder?

[zedicus00]

the bends can be helpfull in a 2-stroke pipe. one of hondas GP bikes had what looked like several feet of exhaust S curved under the subframe before exiting in a tiny stinger. its all about back pressure and wave return at ideal RPM.

direct injection makes it easier to tune and get a broader range of 'jetting' allowing cleaner running and more power. but the expansion chamber will always be needed on a 2 stroke. UNLESS they went to a valved 2-stroke like the old Detroit diesels.

[bhatch21]

Originally posted by zedicus00
... but the expansion chamber will always be needed on a 2 stroke. UNLESS they went to a valved 2-stroke like the old Detroit diesels.

I thought that too, but look at 2-stroke outboard motors. They have no expansion chamber. I have a 2.5L EFI V6 2-stroke Mercury rated at 240hp. It has 2 exhaust manifolds like a car that exit in a 3-4 inch diameter rubber hose that goes directly to the muffler.

[zedicus00]

it will run, just not truly ideal, but there are times when the space is more important, plus with all of the other tech in those mercs, the chamber was less important.

tuned pipes would gain substantially on something like that. but you would be sitting next to the expansion chamber and you would never be able to have a conversation with anyone else in the boat.

[rk88r]

A center dump pipe might be useful for fitting a pipe in a reversed cylinder motor.

[wilkin250r]

Originally posted by bhatch21
I thought that too, but look at 2-stroke outboard motors. They have no expansion chamber. I have a 2.5L EFI V6 2-stroke Mercury rated at 240hp.

Yeah, but do the math.

Start with a realistic number for your modified 250cc engine, let's put it at 40HP. (There are some faster and more powerful, but 40hp is a very realistic and rideable number.) If you have 6 of them to be equivalent to your 6-cylinder outboard, you get to the same 240hp, conveniently.

But the displacement on six 250cc cylinders is only 1.5L. That's only 63% of the displacement size of your 2.5L outboard.

Or to make it easier to compare, your 250r is putting out 0.16hp per cubic centimeter, while your outboard motor is only putting out a measly 0.096hp per cc. That's worse than a 4-stroke, at least they get a little over 0.10hp per cc.

[dunatic]

Originally posted by KM250R-BDTM
At Selvy’s Performance we built a reverse cylinder 250R and a reverse cylinder Banshee. The 250R was finished and saw almost zero testing, however; the Banshee saw Sand a few times. We (Rob) made ‘Straight Pipes’ and the thing screamed…couldn’t keep it together.

The Straight Pipes made a huge impact on Pipe design & performance as well as tuning.

Building a 250R with a reversed cylinder and a ‘Straight Pipe’ is a side project I would love to follow through to the end this time around.

Those have been built many times. They are often called "Crankensteins"

[dunatic]

reverse technology (http://www.motocrossactionmag.com/Main/News/...ENGINE-DESIGNS-7056.aspx)

[dunatic]

Originally posted by dunatic
Those have been built many times. They are often called "Crankensteins"

http://www.youtube.com/watch?v=2yvOI9sDTBo

[bhatch21]

Originally posted by wilkin250r
Yeah, but do the math...


Yeah, I understand your comparison of hp vs. engine cc. My point was that I have a stock, EFI 2-stroke that makes decent power without an expansion chamber.

Now, the modified 2.5l Mercury motors are used in F1 racing boats. They make 400hp, or .16hp/cc. I don't think they have an expansion chamber either.

[zedicus00]

expansion chambers like we know today are fairly new technology. heck even the kawasaki h2 didnt really have an expansion chamber on the stock exhaust system.

2-strokes don't NEED an expansion chamber to run, they do NEED an expansion chamber to make peak efficiency in ideal RPM's.


or a partially valved engine like the diesels. 2-stroke diesels would be the way forward to to the difference in fuels, i think anyway.

[KM250R-BDTM]

In 1986 a reverse cylinder Honda 250R and a 1987 the reverse cylinder Banshee was unique and a first. These two models had not “been built many times” before…they were one of a kind model for each and a first at Selvy's Performance.

[destey]

why didn't they continue with 2 stroke technology?

[jcs003]

im sure a "straight pipe" design could make peak horsepower. what is needed is internal chambering/baffling to create the backpressure necessary to allow the two strokes constitution to be harnessed. the problem is alot of R&D would be needed. plus, the pipe would be difficult to build.

another thought would be a "reed" type baffle in the straight pipe chamber that changes based on rpm...

[Ex_Rider43]

Good find for sure !