go team changfa!

[mobile_bob]

hope this link works, i thought you guys might like it

https://www.facebook.com/PerfectEdgeMotorsports/videos/1060620497294552/

bob g

[BruceM]

Love it.  They do haul ass!

[AdeV]

LOL!

There's a similar - if anything even more surprising! - one on YouTube I found the other day...

Fingers crossed, by the end of next week I'll have my very own 12hp Changfoid!

[glort]

I'd love to know what they do to them and i'm surprised they don't appear to be Turbo'ed.

Love the way the first one is blowing flames during the burnout.  Oh the EGT's!  Bet they replace pistons often!

The one in the 2nd Vid has a battery. Wonder why they have a battery on a diesel? Thing has no headlight so what it's doing I have no idea.  Maybe it's ballast??  :0)

[vdubnut62]

Glort, I don't think you can get the EGT's high enough on a naturally aspirated diesel to fry a piston. IIRC aluminum melts at around 1200-1400 F?
It does however, give me the heebie jeebies thinking about flywheel rim speed! That big thin flywheel would be like a ripsaw, and bunches of shrapnel if it "let go".
I personally would get a nosebleed and the perpetual s#!ts from going that fast on a sulky. I'm too Old, my Guardian Angel simply can't fly that fast.
Ron.

[BruceM]

I noticed they had fitted a ram air scoop on the air intake; at speed there's your low pressure turbo.  I expect rules limit turbos and many other modifications to keep it a working man's sport.

Looks fun, but like Ron, I would not want to be on the sulky.

[mobile_bob]

i am thinking i would want at least a flywheel laser cut out of mild steel, that would be easy enough i would think
and watching both videos, only small helmets for protection? wow

not even knee and elbow pads like a skateboarder?

talk about road rash!

be my luck i would have a brg seize up at just about the 1/4 mile mark!  that is on one wheel of the sulky!

maybe the guys are good enough to raise one foot up in the air and ride it out on the good wheel?



i would be fun to watch, at a distance of course!

bob g

ps. George B. thinks the one running against the pickup is a 185 series..
and i am thinking the battery is for running the radiator fan? or maybe they are electric start?

[Derb]

Awe you have to give those guys credit - Man they got stones!

[glort]

I noticed they had fitted a ram air scoop on the air intake; at speed there's your low pressure turbo. 

I actually looked that up for some hair brained scheme I was interested in years ago.  You have to travel at a surprisingly High speed to get any worthwhile positive pressure in an intake for an engine. I seem to remember 130 MPH being a startoff number. I also recall it does not matter how big your scoop is and channeled down to, the air pressure is still small and the same.
Not sure they would be doing 130 but the flared intake could stop the shearing and actual air starvation caused by an edged intake.  That bellmouth shape is not an accident. It's the most efficient shape for drawing air into an orifice from any direction.

Sure would be interesting to see what one of those things could do boosted. Spray of Water should keep the piston from blowing into the sump.  :0)

[BruceM]

Interesting, Glort.
There's also some interesting things going on in a carburetor with a intake horn that is of the right size and length.  Someone had fitted one on my '63 Skidoo 2 cycle engine and it's top end at high RPM was noticeably improved.  I don't know if these Changfa guys have tuned their intake but it's possible. Something about changing the pulsed, turbulent air flow to a more continuous flow, as I recall.  Nothing like adding a turbo, of coarse.

[mobile_bob]

hey guys take a close look at the beginning of the second video, the one that is up against the pickup

that one has a turbo on it! and is not the one in the beginning seconds of the video, the one with the big pulleys
and the air scoop.

the video still pic at the beginning has a turbo, and it is the one running against the pickup

does anyone else see it?  there is no air scoop funnel on that one.

bob g

ps. when it comes it ram air intakes an included angle of 7degrees is the max after which there is no further improvement or ram air effect.  having said that having the bigger bell doesn't hurt anything, and looks cool, but really has no added effect over an intake with a much smaller inlet pointing into the wind.

bob g

[glort]

the video still pic at the beginning has a turbo, and it is the one running against the pickup

does anyone else see it?  there is no air scoop funnel on that one.

Yep, You're right!  Can't see/ make it out on the vid itself but would certainly explain a lot. Diesels without turbos suck for vehicular applications.
I was only saying to a friend of mine hours ago that i'd like to put a turbo on the little Kubota tractor I want to get.  Don't think it would do much for power but the look and sound would be worth every penny of the cost of having a manifold made up or the plates cut to fit.  get rid of that side exhaust and put a stack on the thing. Might as well, that stupid ROPS bar is going to catch on any low tree anyway.

I used to play with 2 Stroke lawn mower engines in years gone by. Started out building one for a mate for his kids Go kart. He never used it so I put it back on a mower and the thing was awesome. I bought a book on 2 stroke tuning and it was great. So many tips and tricks on how to do it right and I started developing the engines more and more.
The factory rating of the engines was 3.2 HP@ 3800 RPM. Mine did over 12 hp @ 12K rpm and that was mid way through my playing and got a lot better after that.
Stock carb was a 10MM I went to a 24mm and it used every bit of it.  Shaved the heads radically, something like about 7mm.  Ran over 13:1 compression but didn't seem to detonate for some reason.  Didn't do much with expansion chambers as I had no way to make them and bike shops wanted stupid prices for the things even if beat up and old.  I did play with some long straight through pipes and seemed to get a bit of a draw through effect with them but that was limited increase as it was just clearing the old gas not forcing the charge back in like a true power pipe.

None the less, the things fairly howled. The timing was fixed with no advance but I filed the clots out on the coil as far as I could take them and ran that for timing and that certainly helped.  One of the hardest things at first was the carb jetting. I got a Mikuni carb off a 250 cc Bike ( mower engine was 160cc) and couldn't get the thing right. I thought the mower engine would take far less jetting than the bike but in fact it was the other way which amazed me. The mower wanted a heap more fuel even though it was a much smaller engine.  The ideal seemed to be between 2 jet sizes which isn't much but in the interests of longevity I always ran the thing on the fat side.

Another thing I learned from the book with fuel was there was no standard oil mix.  It basically said run the oil till it dribbles out the pipe, back it off just enough so it doesn't and that's it. More oil you use the more lubrication you get.  And this seemed to hold true. Despite doing stupid things with these engines, I never blew one up and in fact got better longevity out of them than one would expect in stock form. If I was running them lightly, I'd use the stock 25:1. For mid sort of loading i'd drop that back to 20:1 and when I gave the things hell it would be 16:1. If you ran them hard at 16 they would be fine. if the next job was light and if you ran them without much load even at high rpm, they always Dribbled.  I always used good Bike or outboard oil in the things. Mower 2 stroke is just garbage.  Also ran them on a good rich mix of veg oil which I deliberately had running out of the pipe and that seemed to work very well. Of course my favourite ( and most expensive of course) was the good old fashioned Castor R.  Castrol Castor oil. The smell of that took me back to younger days at the speed way.  I got some methanol, rejetted the carb and ran the thing on the meth/ castor mix just to get the authentic racing smell.

I remember a neighbor coming home one day when I was out mowing and couldn't believe the smell of racing which he also was familiar with was coming from the mower and how I had it set up.  He said he had heard the thing before but thought I was riding my Harley round the back yard or something.  Don't ask me how he thought they sounded the same, guess he just didn't take the thing for a lawnmower.
Another trick i learned from the book was to chamfer the piston skit. Instead of having a sharp knife edge that scraped all the oil off the piston wall, I'd just grind about a 45o Bevel about 3mm deep around the skirt. The idea was that this would allow the piston to ride up on the oil film particularly on the thrust side of the engine rather than scrape it off and give more metal to metal contact.  Seemed logical in theory and to work in practice real well. I also do that slightly on 4 strokes. same effect, get the oil between the piston and bore and the oil rings will take care of any excess that the piston shouldn't be scraping off anyway.

I remember one really hot engine I built. I changed the transfer ports mainly by widening and deepening them marginally and did do the risky thing of changing the  timing as I thought like everything else it would be plenty conservative.  I opened out the inlet port as far as I dare ( was an old barrel I honed the lip out of anyway and put oversize file back rings in)  and not only shaved the head as far as I could ( actually too much, filled a hole with lead) put a 30mm carb on it I got and made up a rather Gumby looking but effective reed valve setup.  This gave the thing a long inlet tract with a fair plenum area on the carb side of the reed valve.
A mate came over to visit as I was putting the thing together and he watched as it went from parts laid out on a white nappy on the bench to a running engine in about 45 min.

The thing fired right up but was like a hit and miss engine. Every time it fired at idle, it skewed the whole mower about 30o.  You could tell the thing had serious compression. I let it run a while then hit the throttle and it was like blipping a top fueler idle to flat out and back in about a second. I tried in on the overgrown test patch of lawn I was then keeping and the thing kept stalling.  Give it some throttle and it took off. It didn't like a half way measure, it was pretty much all or nothing. Peaky as all get out but but boy, the power was something.
I completed the test easily shooting the cut grass clean over the 6ft fence and came back to my mate. He still teases me about what I said to this day.  " It's a bit peaky, I think I took it a bit too far" He just looked at me and exclaimed, Nooo! ya think so? The thing is blowing a constant flame out the exhaust, ya really think you over did it a bit?"

That engine did become legendary though. A mate of mine having seen my previous creations came by a few weeks later and said he had a big clean up job on his mowing run and knew his Honda's weren't going to handle it. He asked if he could Borrow my ( improved) mower to slash it.  I said I have the perfect thing for you.  It cut this thick grass all right, the exhaust set fire to it a number of times as well but he let it go and just mowed over it on the next pass.  Reckoned he never used so much fuel in a mower on that amount of lawn but didn't care as the thing went straight through what would have taken him hours to slash with the brushcutter.
He said it was doing it so easy he thought he must have over estimated it so he got out his mower and tried it. He said he couldn't even get a foot into it before the thing stalled out. He had that mower for 3 years and gave it hell. He eventually brought it back when it started playing up and without much thought, I stripped it down thinking at very least the rings would now be shot and probably the bearings too.  I was amazed the thing still had hone marks right through the bore and the engine while clearly not being new, was still in excellent condition. the problem turned out to be the plug lead that had rubbed on teh cowling and was shorting intermittently.
Put another 8mm silicone car lead on it, buttoned it back up with nothing more than new gaskets and it ran for many years more till my mate used it as the sweetener when he demonstrated what the old piece of crap was and what it could do when he sold his run.  Was still running wildly then.  I always think that was testament to the piston chamfering and running plenty of good oil. 4 strokes wear out faster these days than the life that thing put in.

I had a lot of fun with those engines and cleaning out my shed the other day, I came across a load of bits and pices for them. I kept one good engine and some spares but have to get rid of the rest.  Haven't touched them in years and I'm into the diesels now rather than the 2 Strokes. So many people bag 2 strokes but it really is amazing what you can do with them. People bitch about them being unreliable and hard to start and all sorts of other things but if they don't start easy and are unreliable, you just don't have them set up right or they need rebuilding.  I have rebuilt Briggs and they are the greatest piece of garbage I have ever come across.
I also have some Chonda's and found them to be nothing but reliable, powerful and actually economical. I'd take any Chinese cheapy over a Briggs any day.

No, If I can get hold of some of those vertical shaft Diesels to use on mowers...... I can see it now.... 25:1 Compression, 12mm pump elements, Meth injection, Turbos, car injectors....  :0)