Planet Minis

chrisc161076

Cyclerider,

Just go with both, if you've got the time that is. This will go through the theories of modifying stock parts and the mechanics of design of new parts.

Have you got a photo showing the side profile of your alu. rod verses the original?

cyclerider57

I will shorten the cylinder to match the standard 88 piston of my choosing. The piston will have to be modified as well.

I'm still working on the SOHC 4v for 52mm bore. I have talked with numerous companies about everything from billet cnc to creating casting molds for me. I am currently waiting on another quote from a casting company.

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cyclerider57

I don't have the time to dedicate to keeping two threads current.

Honda50.com Z50, CT70, ZB50 and Monkeybike tuning parts. has my public photo album.

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Brandonbmw

4 valve on an 88........... can i ask why you are doing this............... when the power isnt really much more than a +r

cyclerider57

I don't recall ever saying that.

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Brandonbmw

i remeber seeing a dyno somewhere another saying that. i wasnt quoting you sorry about that mishap. i was just curious to why yourrr choosing a 4valve. i think its awesome i jsut wanted to know the mechanical reasoning behind it lol

50rider340

that is sick i was hoping you were still working on that. Def keep in mind that if you get to produce that, ill be first in line to purchase one. Im assuming your trying to find the most cost effective price with it. That would be extremely impressive to have one made out of billet bling factor alone haha.

But back to what this thread is about. What would you be doing about the cam chain though having to shorten the cylinder? Wouldnt it become to short causing the chain to be to loose?

My brother went to an extreme i dont know if you read his thread. He took the 52.4 porcupine boyesen 69mm jug (from AHP), had it machined down to i think it was 65.4 to compensate for the pin height so the cylinder sat flush with the piston. At first he broke the first cam chain because it was to tight. So he spent the better half of a night with a chain saw file and filed the cam sprocket while counting each time. he ended up having enough slack that the chain wasnt to tight. In return he had a one off motor that no one else had. It ripped for what it was. Problem was he was useing a e22 head and now since moved to a tak super head so that motor is on the shelf now.

cyclerider57

With the same amount of development time given to either a 4v or 2v head. For most companies a 4v will perform better unless they have had no experience at all with them (IE: Why Harley-Davidson had Porsche "help" them with their V-Rod... don't be fooled, Harley had little to do with it. They still live in the 70s).

We are getting a little off track of the original thread but it is doing was it was supposed to... stirring technical information. A four valve head has greater flow area especially at low lifts. This means more power with less aggressive camshafts which helps many engine characteristics. This relates to why the valves are so big on my +R in this thread so you can look back over that so I don't have to type it again. Because the valves are considerably lighter and the lifts are smaller on a 4v it dramatically reduces the chances of valve float or seat bounce. A pent roof combustion chamber (typical for 4v) has better combustion properties and a more centralized spark plug (even if it isn't in the center) can provide better spark characteristics.

A lot of times when you cram huge valves in a 2v you end up with a lot of valve shrouding not only in the head but also along the cylinder wall. This hurts flow potential, in most cases a lot worse than the 2 flowing valves on a 4v conflict and disturb each other. Tumble characteristics are more easily developed in a 4v head as well. This is when the flow rotates around an axis parallel to the crankshaft. Swirl on the other hand (easier to create with a 2v) doesn't have as much of a benefit once the piston starts to reach tdc and combustion is about to start.

You want turbulence as the piston reaches tdc. Swirl is the charges characteristic to spin in an axis parallel to the cylinder bore. A combination of both is required for the best charge (ultimately the goal is to have peak combustion pressure around 14° atdc depending on the stroke, rod ratio, pin offset, piston design, etc). 4v heads also have a tendency to lend to a better port shape merely on how they have to be designed to allow flow to two side by side valves. You can have a single valve ported more effectively but normally design within the head limits this potential.

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The wise understand by themselves; fools follow the reports of others. Goodness speaks in a whisper, evil shouts. -Tibetan Proverb

cyclerider57

If I remember right, I talked with your brother about that build as he was doing it. I had shortened a porcupine cylinder not long before he did that project so we had some discussion.

I will be running a manual chain tensioner. The cam specs won't be out because I slot sprockets and degree cams in rather than trusting the stock holes. It won't be short enough to run a shorter chain but won't be so short as to cause too much chain slop.

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The wise understand by themselves; fools follow the reports of others. Goodness speaks in a whisper, evil shouts. -Tibetan Proverb

arlindsay1992

Man this is cool! I'm sure there are some people who will be asking for a price when the motor is finished. Do you plan to sell it or keep it as a trophy for yourself?

Motarded

What are you expecting out of this engine?

cyclerider57

I'll probably tear it back down and build something else out of select parts.

If I don't, it will be going in a billetware chassis I have sitting here with +2 swingarm, cut down sano forks, and motard tires on billet 10in wheels.

Everything is for sale for the right price... nothing of mine is cheap. I would never list a price. Someone would have to make an offer that I couldn't say no too seeing how I treat my engines like babies with all the care in the world as I build them.

I'd rather not quote a number at the moment but I'd be pretty happy with 13hp (on my dyno an out of the box 124SE had 13hp).

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The wise understand by themselves; fools follow the reports of others. Goodness speaks in a whisper, evil shouts. -Tibetan Proverb

Motarded

If you make 13 hp. I will be very impressed. Good luck with this! I am looking forward to the results.

schofell84

any updates?

Kurlon

After seeing Toyota do it for efficiency, and Yamaha do it for mass centralization, and a lil power to boot, have you considered angling the cylinder up, so the bore centerline dips below the crank center? An angled spacer plate welded to the cases, a shorter cylinder, an external oil line to the head and new studs should do the trick?

50rider340

Interesting ide This would be a large amount of work for how much of a efficiency gain?


Btw cyclerider. Just a quick flashback to running boost. When you brought up the volume issue could that be compensated by running a dished piston and say an old style honda dome head. When I crunched some numbers the compression ratio would be more than low enough to run 93 pump gas and not worry about detonation. On top of that the volume in the combustion chamber is doubled when compared to any other set up. Is this what you meant by volume or are you dipping into the issue of the amount of CFM actually being drawn through the engine and it being very low amount? I just got this itch for boost hahah. BTW, i would steer clear of the blow through set up and fuel injection since one is a headache and the other is big money. I've scene/studied multiple draw through set up that worked very well on some rotary motors and a few v8's and would attempt this route.

The only other idea i was thinking about for a street application would be the asin amr500. Theres that one guy online that ran this on a cafe bike and achieved some very large hp gains with a lot of trial and error tho. The efficiency drops thought since the supercharger robs power unlike the turbo set up.

I saw that my brother brought up the cut down boysen cylinder. I'm kinda bummed since its just chilling and sitting on the shelf now. I gotta machine it down to 63mm and get it nikasiled to 52mm so i can run it with the takegawa head i have. It would look so darn cool haha.

Also what are your thoughts about the polini 4 valve. There 4valver ran a 107 motor. So 49.5 with a 52.4 bore. I was on the hunt for a while to scoop this. Came up short when everyone wanted like 1000 bucks to just get the head.

I still would love to get my hands on one.

bballard9606

kinda late on the thread but i just kinda skimmed thru it all.

from what i read what you are doing is awesome man. cant wait to see the outcome!!

im not real techy with motors and im still learning. this thread has actually taught me alot.

cant wait to see it!
keep up the good work.

cyclerider57

I'm not worried about efficiency and I still believe Yamaha is overplaying their system to make people believe it is such a major breakthrough. Like I've said, other companies have done crank shifting, offsetting the wrist pin in the piston, etc for numerous reasons. Yamaha quotes that having it offset allows for a straighter rod angle which in turn gives more force in the thrust direction instead of into the cylinder wall which they state reduces friction. This is true right after tdc but they don't tell you it also creates extra friction in other parts of the stroke as the piston is not a solid body, it can be seen to have the piston rock side to side four times through the strokes. They obviously did it for a reason because I can't see them doing it strictly as a ploy and friction reduction after tdc. With the trends of the Japanese companies focusing more and more on chassis development, they are actually doing things in the engine department strictly for the chassis group while sacrificing engine design. This has been done for years or we would have offset shocks with straight intake ports.

This is actually the correct strategy as sad as it is to the engine gurus. Think of the chassis only benefits it created in allowing chassis group to design flex in specific areas, creating a more centralized mass (Don't be fooled into thinking that Honda hasn't sacrificed power just for that, look at the crf250 when it had dual exhaust. That had nothing to do with power.), etc. By doing that it was also the only way they could get their concept of having a more downdraft style intake port. They had to have ample room for the chassis while keeping the port straight. Something had to be done or the port would be stuck into your steering tube unless it had a considerable bend. Overall I think the Yamaha engine is a great design but that opinion has nothing to do with an offset cylinder. Add horsepower and you go faster in a straight line, add handling and you go faster on the race track. The straights already go by too fast so the only way to truly have a faster bike is make it handle correctly.

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The wise understand by themselves; fools follow the reports of others. Goodness speaks in a whisper, evil shouts. -Tibetan Proverb

cyclerider57

When I said volume I was strictly talking about cfm through the system. It would take a good design to reduce friction enough to allow such a small engine to make a benefit. I haven't done a lot of looking into what they have available for small engines but I still believe it would take an engine specific design to allow for the benefits. If you were going to do work with combustion chamber don't forget you want the smallest surface area with the volume you're looking for to meet your compression ratio. More surface area means more area exposed to heat which means lower thermal efficiency. Don't forget to take into account that if your system is working correctly, you are increasing the compression and heat generated which means your dynamic compression will be much greater and would require a higher octane rating.

I've never worked with the polini head or even seen one in person so my opinions have to remain small. There are obvious things within the combustion chamber design that I don't like and would change but that is really all I can say as I don't have real information on it. I wouldn't really want one just because I have enough stuff going on but I think it has the potential to work really well.

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The wise understand by themselves; fools follow the reports of others. Goodness speaks in a whisper, evil shouts. -Tibetan Proverb

cyclerider57

I'll try to get more stuff to talk about up in the near future.

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The wise understand by themselves; fools follow the reports of others. Goodness speaks in a whisper, evil shouts. -Tibetan Proverb