Fair weather rider
Okay thanks Woobly.
Here are the dimensions of a popular pipe for this type of engine that I measured last week and reproduced in engmod.
I know you don't have a crystal ball.
With the angles of this pipe for example can I point the front wall of duc A backwards as you recommend or else I will have to make a pipe with it more aggressive angles?
Forum whore
Yes I have a crystal ball , I believe the A port front wall pointed further back would work well if the pipe was modified.
33% and 67% are too long for optimum performance in a CVT.
Narrow the header angle to steepen the 1st diffuser and shorten the header - the amount you shorten the header closer to 30%, add this to the mid section.
Thus the whole diffuser is moved leftward to something around 30 - 64% with a steeper 1st section.
This adds a bunch of peak and upper front side - as would a 3 angle rear cone.
Ive got a thing thats unique and new.To prove it I'll have the last laugh on you.Cause instead of one head I got two.And you know two heads are better than one.
Forum whore
Anyone got a TD3 cylinder I could use to check what is possible going mental on it , adding reeds etc.
Please PM me if there is one out there.
Ive got a thing thats unique and new.To prove it I'll have the last laugh on you.Cause instead of one head I got two.And you know two heads are better than one.
Forum whore
Ok, time to put these bad boys to use.
After a bit of lathe work a 15:1 head by test (17.8cc) 0.75mm for 40m/sec max squish velocity at 9K rpm.
12:1 head vis
15:1 head. Bearing in mind that the motor is cold and there is a lot of oil and grease around the ring land of the piston.
Forum whore
.
Amal alcohol needles needed some modification to be used successfully in the Yamaha TD3 34mm Mikuni carbs.
This is a chart I made of the flow characteristics of a 6F9 Mikuni needle vis an Amal alcohol needle.
The curve on the graph is an un modified Amal needle at less than 20% throttle. The top line shows a modified Amal needle.
The shoulder on the Amal needle where the taper meets the parallel section at the top needs to be blended out other wise it obstructs fueling at low throttle.
This blending needs to be about where the curve touches the Amal needle in the picture.
The Amal Concentric needles are to short for the Mikuni 34's. So the clip needs to be silver soldered to the very top of the needle itself.
Otherwise the needle can pull out of the needle jet and hang the slide on full throttle.
I did this was work to help some racers get past seizing issues they were having at a time when the Amal alcohol needle was popular.
Unfortunately I don't have any further detailed notes on the rest of the setup for TD3's running Methanol.
Forum whore
Interesting, just what I proposed, butterfly in the exhaust reverse cone.Originally Posted by Frits Overmars
Its what I have in store for the AG100 twin piper.
Thats why I wanted a single reverse cone but it will be easier to make two, one for each pipe.
Im not sure I saw a dyno run with it installed?
No8 Wire Extraordinaire
I'm going to grumble again. That is a picture of a pressure gauge with a one way valve.
It is not a good indicator of compression ratio.
For example, and for giggles, I tested my 200cc dirtbike after planning the head. 193psi. It measured at something silly like 14.5:1. Oh dear. Took some metal out and was 13.4 after a couple of iterations.
Great. Same guage, still hadn't started the bike. 195psi.
Ohh I guess the compression ratio has gone up despite metal removed and measured.(spoiler alert, it hadn't).
Put the gauge in a box.
Don't you look at my accountant.
He's the only one I've got.
Forum whore
Maybe I should have pointed out more clearly the gauge was just an interesting shits and giggles comparison between 12:1 and 15:1 heads that had been CC'd using the measuring devices seen in the first photo.
EngMod-2T gives a calculated pressure of 167 psi for a 15:1 head.
Pretty much what I am seeing on my gauge so it is in the ball park. Reassuring, but you are right, I should not rely on the gauge, a CC ing test is best. Although the pressure gauge reading may come in handy later for trouble shooting.
No8 Wire Extraordinaire
That's what it is. I pulled it out last month to test a mates RS125 Aprilia roadbike which stopped running. 30psi. Clear what happened there. Course a finger over the plug could have told me that. Bit weird with electric only start mind.
Don't you look at my accountant.
He's the only one I've got.
Forum whore
I could not have said it any better, not even in Dutch.
I've noticed that some people find it easier to work with lengths rather than angles. That is why I'm considering a graphic representation in which, instead of the various axial angles of the transfer ports, their positions and target points are expressed as percentages of the cylinder bore.
This may also be helpful in drawing the desired flow paths on a piston dome.
Like the man said, I'll be back.
Forum whore
Just an interesting factoid for those fiddling with butterfly things in the rear cone.
This setup was used in direct drive karts ( chainsaw engines ) many years ago but they had a simple fixed flat plate @ 50% area about 1/2 way down the rear cone - this was called a plate pipe ( funny that )
These were quickly replaced by the "new" technology of having a series of perforations spaced radially down the rear cone, within an enclosed muffler tube that was simply an extension of the mid section.
This methodology has been standard fare on kart pipes for 30 years.
Even today this is used in several direct drive International classes.
When it came to modelling the things in EngMod , the assumption ( wrong ) was that there were two functions involved.
Firstly was that as the bulk flow thru the pipe increased the effect of the holes gradually reduced , and the volume of the parallel " muffler " tube would resonate at a particular rpm , effectively then
making the holes disappear.
Thus the return wave was smeared out in amplitude at low rpm , reducing the effect of the pipe being too short down low, and causing the return wave to arrive at the port too soon.
But then a customer , working for the Tony Kart factory , bought the TFX system and it became clear this is not how it works. ( Frits is now using this same piece of gear ).
At low rpm the rightward wave is transmitted thru the perforations , and is reflected back , at a much longer TL by the flat plate at the end of the " muffler " tube - well past the rear cones exit hole.
Then at high rpm the tubes resonance effect overcame this , and the holes do virtually disappear.
Neels changed the code to reflect this new line of thought , and boom , we had way better correlation with the TFX results.
The system works unbelievably well , in situations where the crank is connected directly to the load - be that a wheel or a propeller.
And is KISS to the extreme.
Ive got a thing thats unique and new.To prove it I'll have the last laugh on you.Cause instead of one head I got two.And you know two heads are better than one.
Forum whore
There must be some compromises?
Hardcore Biker
After a 12 months hiatus, no, not jail or anything like that, I now have the opportunity to get into some 2 stroke stuff again. This is before we’re all forced to be 100% electric from 2035.
So, it’s back onto DCI (Direct Cylinder Induction). However the previous one, which ingested into the A ports, this version will be into the B ports. Why? Well going thru the A ports meant that at TDC or so, the DCI intake also communicated with the crankcase, offering both crankcase piston port induction plus the DCI function. So it didn’t really tell me whether it actually worked or not as a pure DCI. Even if it did, the poor old pressure waves in the passage would have got confused and possibly self-cancelling…dunno.
Anyways, as it turned out, the B ports were always covered by the piston skirt (see pic of skirt with some trial coating), other than when at BDC. So, it’s obvious, to give it a go with the A ports feeding the cylinder via the standard piston port inlet system.
As previous, will weld on aluminium blocks (still need to be drilled and tapped) after fixing to the with the little fixture plates shown and then, with Devcon F, fill all the gaps etc such that I can create a direct passage to the B ports, blocking off the original B passage to the crankcase.
Intend to leave the port timing as it is, nominally exh 178, transfer 120 & inlet164 durations. The B ports of the liner can be seen in the pics.
Would be interested in any thorts on the poughts in terms of their entry angle if this could be improved. Easy to do when the liner is out before the welding takes place.
"Success is the ability to go from one failure to another with no loss of enthusiasm.”
Hardcore Biker
Couple more pics....seem to be limited to 4 max.
"Success is the ability to go from one failure to another with no loss of enthusiasm.”
Anorak
5,but it spits out repeats....
Kinky is using a feather. Perverted is using the whole chicken
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