ESE's works engine tuner

[wobbly]

Its impossible to make a statement with any meaning such as " for 8500 rpm the transfers should be open" - as I said, the angle area varies hugely between a short stroke Vs a long stroke, so any calculation must involve all of the elements of the design to achieve any accuracy at all.
There are several programs available now that can point you in the right direction, reading 30 year old books is OK for background info only.

The port floor geometry is super critical for any high performance application.
Fuel/air in the duct is forced to follow the outer wall ,no matter what,but the short turn radius and the floor exit angle combine to keep the flow column "coherent".
When the inner shape is not matched correctly the flow detaches very early, creating huge amounts of turbulence,this ruins the scavenging streams directional control,and as an aside it then also looses contact with the piston face.
Keeping the piston cooler is just a by product of the fact that the transfer streams are kept attached to the inner wall - when they dont everything turns to shit.

Re the PV clearance - I dont know who told you that it isnt critical but thats bullshit.The PV face should be as close as you can get it without snagging the bulging ring face.
Much more than around 0.5mm and you start to loose effectiveness with too much blowby.
This is the whole reason that curved and multi blades were developed, to keep the PV edge as close as possible to the piston during its whole stroke length.
In the RGV you have to modify the valves a heap to get them to work at all.

Edit - please dont take any of my remarks about 2T technology as personal attacks on anyone's knowledge on the subject.
Its just that reading Bell, or Cameron and even much of Blairs early stuff is like swatting up a Tube Radio Repair Manual, and then trying to design a Mosfet power amp.
Even the basic CAD type programs that use STA as a basis for getting the ports in the right place for the rpm,power needed and swept vol are hugely better than the old references.

[TZ350]

Even the basic CAD type programs that use STA as a basis for getting the ports in the right place for the rpm,power needed and swept vol are hugely better than the old references.

A handy (and cheep $16 USD) Porting Calculator from:- http://www.porting-programs.com/ it is based on Blairs and Jennings work. Use the Blair data for STA and blowdown required for a selected power output.

Kel gave me this link to a very interesting book. www.prme.nl/download/engine-1.pdf

The decade pages from p80 have link collections, links to Jenning and Bells books can be found there somewhere.

[ac3_snow]

The port floor geometry is super critical for any high performance application.
Fuel/air in the duct is forced to follow the outer wall ,no matter what,but the short turn radius and the floor exit angle combine to keep the flow column "coherent".
When the inner shape is not matched correctly the flow detaches very early, creating huge amounts of turbulence,this ruins the scavenging streams directional control,and as an aside it then also looses contact with the piston face.
Keeping the piston cooler is just a by product of the fact that the transfer streams are kept attached to the inner wall - when they dont everything turns to shit.

Cheers for the explanation re. the reasons for port angles etc Wobbly. Very helpful.

[Bert]

rather off topic, but enjoy:
http://rmdmotors.com/kenny-roberts-collection/

If only lotto would roll out the right numbers

[cotswold]

rather off topic, but enjoy:
http://rmdmotors.com/kenny-roberts-collection/

If only lotto would roll out the right numbers

I checked out the price on this little beauty
http://rmdmotors.com/1980-gp-bike-kreidler-van-veen/

1,350,000.00 JPY = 20,218.57 NZD

Bit much to bucket ?

[F5 Dave]

ahh the tyre's flat, knock em down a bit.

Even Husaberg would have trouble justifying that as bucket legal. But yeah hella cool bit of classic kit. Tyres are a bit frightening.

[husaberg]

.

Even Husaberg would have trouble justifying that as bucket legal. But yeah hella cool bit of classic kit. Tyres are a bit frightening.

I thought we had kissed and made up

[TZ350]

Trying to make sense of my last few dyno sessions.



Blue line, the cylinder with side exhaust ports might be 30hp but its not a very appealing curve compaired to the conventional Suzuki GP125 cylinder.



Running the Vtec improved the carburation and curve but the extra inlet length of the Vtec seems to have knocked back the over rev.



In back to back tests the soft close rotary valve seems to give a little more power and improved the over rev, we noticed this with our other engines too.




Both are Vtec soft close. Red line is the 24-28 sticking out the side carb arrangement, Blue line is the 24-38 tucked out of the way arrangement.

In trying to get the carb tucked in, it has realy upset the curve. There was also another problem, where as I could open the 24-28 up fully at nearly any rpm the 24-38 would stall unless the rpm was 9k or more and I had to be carfull with the throttle to get a good run.

The 24-38 arrangement has more over rev but dropped power every where else. This must be due to the different inlet arrangements. So I figure if I can loose power then by some carefull work I can recover it and may be use the inlet system to fill in the 6-7k rpm area too.

The straight inlet seems best but with the Keihin carb its quite long and the inlet tuned length is to long and the carb sticks out to far. I think the next move is to try a straight inlet with a much shorter Kart pumper carb.

If it wasn't for the 24mm rule, I would actually try something suggested to me by Sonic_V, two carbs with different inlet lengths.

[richban]

Very cool. The last graph 28hp looked really good. Great spread of power really across that range. Looks quite rideable. You would no when to change gear with that big drop anyway. Are there any down draft carb options you could try. Might give more carb position options.

[wobbly]

I think that you are beating a dead horse a bit trying to get a big positive result from intake tuning.
The short pumper carb being able to be run "updraft" was one reason I suggested it.
The rotary valve setup needs the flow to enter the case, moving upward over the crank - not downdraft.
As the wave action in the Exhaust is WAY more powerful, then the result from a PV or a ATAC setup will get much more dramatic results, relatively easy to implement as well..

[F5 Dave]

Its funny I was just thinking the other night about this thread. For the how many pages & pages the main point that has had little discussion is pipes.

[kel]

For the how many pages & pages the main point that has had little discussion is pipes.

inlet or exhaust?

[F5 Dave]

crack

[TZ350]

For the how many pages & pages the main point that has had little discussion is pipes.

My interest at the moment is elsewhere



But if you can get Chambers to talk he could tell you about what he is up to.



I see he has lowered the bike to its max and made a mockup of the planned pipe.



And checking for clerance on the front tire.

[F5 Dave]

Hmm, yeah he may need to run a heavier spring. Not sure that gasket pipe technology has been explored before so I salute you, although I can confirm that my bent wire donuts on No.8 didn’t hold further promise so were dropped early in development, but useful for learning how to snake past linkages on bigger bikes.

Yeah that pipe is pretty awkwardly positioned, but most MX bikes are worse. Best to strop the front down & assume there will be additional bending in the frame & forks, although in the RS’s case that will be sod all. On a suzi GP125 as she came its probably a good ½” or more.