ESE's works engine tuner

[adegnes]

Yes floating the crank, normally desirable, is a bad idea in this case. Or rather, the single variator is a bad idea (it's French, you know...)

How about floating just the bearing on the opposite side of the variator, a good compromise, or still bad?

[wobbly]

In many engines floating one side, with a roller or relieving the journal is all that is possible as the drive gear
is held between the bearing and a locknut.
Floating one side allows the crank freedom of movement as the case/bearings heat, up so works fine.

I think that the rotary valve port shape with a wider top and straighter sides is an advantage where the vertical height is limited
by the valve diameter, as it gains area needed to correct the STA.
But rule 1A in any situation is to make the width as narrow as you can,this reduced "port angle " if you like means the valve spends less time
partially covering the port and disrupting flow for the same open/close timings.
Angling the carb will help flow as well by straightening out the duct.

[adegnes]

In many engines floating one side, with a roller or relieving the journal is all that is possible as the drive gear
is held between the bearing and a locknut.
Floating one side allows the crank freedom of movement as the case/bearings heat, up so works fine.

I think that the rotary valve port shape with a wider top and straighter sides is an advantage where the vertical height is limited
by the valve diameter, as it gains area needed to correct the STA.
But rule 1A in any situation is to make the width as narrow as you can,this reduced "port angle " if you like means the valve spends less time
partially covering the port and disrupting flow for the same open/close timings.
Angling the carb will help flow as well by straightening out the duct.

Thanks! I'm maxed out heightwise, so the wider top might be a good idea then.

[AndreasL]

Halfway through the thread for the second time.
So much information at such hi level. Great!

I'm "stuck" with a very old design, 50cc moped engine, (Single exhaust, 2 crap transfers and piston port inlet.), I will have a go at improving it with the information gained here.

So for a start I'm planing to use the rule of thumb of 90% ex port duct, minimal squish clearance, around 190/130 ex/tr etc etc. Trying to keep it simple. It will be difficult enough anyway.

What I have tried to find is some baseline info like the above for how to direct the transfers when only having one per side.

I also would appreciate any thoughts about piston port timing. I have come across all between 140-200* and I guess this is as old as the piston port it self.

I have been able to balance my STA:s in EngMod and get some (to good) results using the "low and wide" rute and pipes based on Frits formulas, but I feel I need some better knowledge/rough guidelines before I continue.

Thanks in advance.

/Andreas

[TZ350]

Page 130 links list to go here ...

Racing at Greymouth

You will have to follow the link back to the original post to find the Video link, well worth a look to see Team GPR in action.

Last of Scott's Greymouth vids. Got the one view only of the third race.

Masterblaster in the wet, and it gets wetter...

Race two. Greymouth, Scott's bike leading the way, almost all the way...

Here's that first race again, this time looking back at a wet Greymouth. Getting wetter as the race goes on!

Greymouth racing 2014. First F4 race looking forward from Scotty's bike.

Pretty amazing times there , you and Dennis would have been in top 5 in P82

GPR engines 1st and 2nd. Good work

http://www.mylaps.com/en/events/1092929

Quite cool that they sand blast all the road markings (white and yellow lines) pre-event to ensure some grip in case of rain.

BOB ... battle of the Buckets.

This thread needs more good stuff, so untill somebody posts some video, here one we made earlier

Video from yesterdays F4 cup, filmed from GPR bike no 11

Anyway here is the first 15min of the BOB , Riding with Mr BucketRacer

[husaberg]

Halfway through the thread for the second time.
So much information at such hi level. Great!

I'm "stuck" with a very old design, 50cc moped engine, (Single exhaust, 2 crap transfers and piston port inlet.), I will have a go at improving it with the information gained here.

So for a start I'm planing to use the rule of thumb of 90% ex port duct, minimal squish clearance, around 190/130 ex/tr etc etc. Trying to keep it simple. It will be difficult enough anyway.

What I have tried to find is some baseline info like the above for how to direct the transfers when only having one per side.

I also would appreciate any thoughts about piston port timing. I have come across all between 140-200* and I guess this is as old as the piston port it self.

I have been able to balance my STA:s in EngMod and get some (to good) results using the "low and wide" rute and pipes based on Frits formulas, but I feel I need some better knowledge/rough guidelines before I continue.

Thanks in advance.

/Andreas

Both Frits and Wob have given out very good pipe designs
Here (Later)
http://www.kiwibiker.co.nz/forums/at...4&d=1413021861

[TZ350]

Heres some pics of this contraption of mine, if anyone's interested.

It's a Peugeot Spx 103, a bit modified. Naked

Attachment 304726

Previous version of the engine

Attachment 304734

I like your bike ...

New engine in progress, went from this:

Attachment 304735

To this:

Attachment 304736

In two evenings with a dremel, without the aid of beer, a feat I'm quite proud of.

I know how hard that is, I had to use a die grinder with carbide bit, took me most of a week to make the fins and cut the transfers out.



12mm alloy base adapter plate to mount the cylinder and under cylinder copper cooling fins.

Ventilated the cases a bit so will bog them up with Devcon F aluminum putty. Std practice on our other motors.

[wobbly]

A pair of transfers is a nightmare.
I did an old 390 aircooled Husky and the only way to get any power at all was to reliner and divide the HUGE transfer pair in two.
And for sure you cannot even think about using Frits or my design styles for what is essentially a lawnmower due to the pipe overscavenging
the transfer system.
This means that at BDC a good diffuser ( read fat ) will create so much negative pressure ratio, most of the uncontrolled transfer streams will do a U turn and exit the cylinder.
When it comes to the piston port, the only approach I can see is to create a port as wide as you want, then use as little timing as is needed to match the STA
to the blowdown and transfer numbers.
These small size pistons can easily go 80% of bore with the Exhaust, so the limiting issue is going to be how much transfer you can create.
My first guess would be 60* back and 30* up, that at least will create some sort of loop effect for you.
Is it possible to get a reed into the inlet, then a boost port can be added and this works well, going all the way back to Kaden et al.

[AndreasL]

Thanks Husa.

I have tried some of that the last couple of days just to get to grips with "what effect what" of the pipe. Not easy and takes a lot of time. But interesting.

I feel that I would like to have the engine modeled a bit better in EngMod before starting to play around more with the pipes. Thus the question about transfers and inlet.

I know its its a interacting process but think I need to do first things first.

[AndreasL]

See that Wobbly posted an answer while I was writing the one above.

Thanks Wobbly, that was the kind of information I was looking for.
Will increase my trans angles from ~22° to ~30° and see what happens.

And as you say, trying tapered headers and fat bellys at this low timing and bad scavagening engine has not given the results I first thought it would. Why "slim and shallow" seems better makes more sense now.

For the inlet I have done exactly like you suggest and will continue on that route. Look at the STA:s and follow what the numbers say.
Really glad I got EngMod. Without a decent sim, one is totally lost! Now I'm still loost...but at a higher level.

So far i have used Yam12 for the transfers since I have almost no inner radius etc. All other models seems to be "to good" for my engine.

I have actually looked at how to build a case reed. But that is a long way ahead, making inserts and welding the cases etc etc. But can be done relativly easy. Need to get engine number one running first though.

Realise I might need to clearify my self when I stated " the rule of thumb of 90% ex port duct" in my initial post.
I refered to a exhaust exit duct/header area of 90% of the effective ex cylinder port area. Just to avoid any misconception.

Getting the ex port to 80% of cylinder bore might be tricky with the to close cylinder bolts and lack of material before hitting air. And as you say Wobs, getting enough transfer in to match the exhaust and blowdown capabilities wont happen without a boost port and reed I think.

Sorry if posting to long, I will try to keep it shorter in the future.

[seattle smitty]

Andreas, I hope you don't succeed in keeping it shorter, because I have many dusty boxes of disassembled old, crude, low-tech racing outboard motors from decades ago, with their two big transfers and skinny boost port, much like your engine, and I am here to listen to ways I might upgrade these old beasts as best I can. If I wanted to crack wise, a little, I could say I feel your pain, but in fact I think this kind of thing is a lot of fun. Especially fun when you don't have to guess at everything, but can get some general direction from an old hand like Wobbly.

[AndreasL]

seattle smitty, thanks for the support.

You are spot on except for the big transfers. On mine everything is tiny.
But still I might be able/have to get some inner radius in there for a better attached flow.
The transfer enter/exit ratio is also a bit high so this will be improved as well with some epoxy added.

I agree about the fun in playing with old out of date engines, (in)famous for being impossible to get ANY power from. Apply some modern technology and great ideas from the likes of Wobbly and Frits and it will be really interesting to see what results one can get. If I am able to transfer what the theory and simulations say in to practice with good enough quality.

Have to take a closer look at the flying boats you race. Sounds fun and very hard at the body.

[F5 Dave]

Which kind of begs the question; with so much to gain & considering the amount of crankcase work you have done; is it possible to carve another transfer behind the primaries? Even a drill hole up with a bore in has to be a better starting point.

Pictures show a Derbi GPR50 head grafted on?

[seattle smitty]

One thing I should have said, Andreas, is that neither of us should ask Frits for advice on this old junk we're fooling with. He has stated that he has no personal interest in thirty year old 2-stroke tech, which you can easily understand. It would be like asking Colin Chapman how to hop up your flathead Ford. Frits directed me to the French "Pit Lane" site, and if you go there and work your way through the archived tech threads (I'll need to do this multiple times, taking copious notes), pretty much everything you need to know is there. When the tech masters like Wobbly offer us a tip or two in our efforts to make a silk purse from a sow's ear, we're lucky, and really shouldn't expect such favors. WE have to figure stuff out.

[TZ350]

So far i have used Yam12 for the transfers since I have almost no inner radius etc. All other models seems to be "to good" for my engine.

Getting enough transfer in to match the exhaust and blowdown capabilities wont happen without a boost port and reed I think.

Yes I found that with EngMod too, and used Yam12. I would have liked a lower performance port simulation that more closely matched the poor port ducts I was working with on the GP cylinder.



Using a drill press might be rough, but it was very effective at opening up the rear ports, I highly recommend it.