ESE's works engine tuner

**peewee** · 13th June 2018, 10:20

Originally Posted by wobbly

Thanks Husa and Jan.
I have a new cylinder to test from TM (designed with the side ears right thru the spigot ) and i want to run it with exactly the Aprilia style steps first
then several versions with top/bottom steps removed with added material in the spigot.

dont say steps are no good now. i havent the patience or time to go back and change mine

**wobbly** · 13th June 2018, 11:55

Honda started the step debate years ago with their tune up sheet that said " do not remove steps from cylinder , this looses 1.5 Hp ".
They were right of course, but the next " step " was to add material to the spigot, that then became a matching oval to round transition " nozzle ".

In varying forms this is what I have been using forever , but when you have huge ears added to a 3 port, that extend the side ducts right down thru the spigot
to the header start , then because 2Ts are contrary bastard things I am not going to assume that having a matching spigot with no steps at all will be the best.
TM kart engines have never had anything but a plain oval exit - and I have seen all manner of variations , with a step only at the bottom, only at the top , and both ( like the Aprilia ).

But the dyno says that for a plain oval - the matching transition works best, as long as the spigot floor is parallel to the cylinder floor.
So now I have a new TM cylinder with the ears , and the correct exit area as well , I will have to test the combinations all over again.
Bastard expensive, time consuming , and frustrating, but when you are trying to out power the best in the world you cant leave anything on the table - or you get beat.

**RomeuPT** · 13th June 2018, 12:16

Originally Posted by wobbly

I suggest you look at the IAME piston,that has a 5* angled edge for around 7mm that then becomes a flat top.
This setup in a TM with a new insert ( with the plug alot closer to the piston and a very flat bathtub ) makes better power than the 4* TM setup ( same cc ).

I was drawing and thinking of the head design to use with the iame piston on my honda and read this and got a little confused.

The flat top radius Iame piston is meant to work on a toroid right? not bathtub shape chamber ?!
Since it will raise compression compared to a flat top and the same chamber, should I just take the some radius of the toroid to get more volume!?

thanks

**katinas** · 13th June 2018, 18:27

Some interesting things in this sketch of Honda NSR 2001/RSW 250 2009 GP engines.
Staggered reed block and longer conrod ( about 110 mm) on latest RSW (Aoyama), no steps cylinder/spigot, reed block angle on NSR ......

**husaberg** · 13th June 2018, 18:43

Originally Posted by katinas

Some interesting things in this sketch of Honda NSR 2001/RSW 250 2009 GP engines.
Staggered reed block and longer conrod ( about 110 mm) on latest RSW (Aoyama), no steps cylinder/spigot, reed block angle on NSR ......

Nice pics
I am not sure that going twin crank was one of Hondas better decisions.
I would hazard a guess it had more to do with trying to shorten the wheelbase than peak HP.
the NSR250s never followed the clear development path of the 500 with the inlet staying behind the engine until very late in the design.
They also sacrificed performance and weight with the Pro arm just for style and selling road bikes.

**wobbly** · 13th June 2018, 20:25

Romeu, the Iame isn't strictly a flat top, it has a 7mm wide 5* conical angle on the timing edge, then an almost flat top ( 1mm rise ).
Thus its a combination really of a dome and flat top.
I feel this is better than Yamaha had with a very small angled edge, then a flat.
Due to the flat top area of the piston the plug is already alot closer to the piston than would be the case with a dome.
So i have used a bathtub ( to get it even closer ) but yes if I was permitted to , i would drop the plug even more with a toroid.
In the KZ application I have already established that the bathtub is better than the normal hemi shape when using the stock TM 4* straight conical piston
but as the class rules mandate pouring 13cc down the plug hole , using a proper toroid isnt possible.

The Honda 250 had the matching oval to round transition spigot for many years before the 125 GP engine did , but to my knowledge they didnt discover the advantage of dropping the spigot centerline
to make the floor of the duct and the spigot co-linear.
I found that during the SKUSA CR125 spigot testing.

**Frits Overmars** · 13th June 2018, 20:42

Originally Posted by wobbly

The Honda 250 had the matching oval to round transition spigot for many years before the 125 GP engine did , but to my knowledge they didnt discover the advantage of dropping the spigot centerline to make the floor of the duct and the spigot co-linear. I found that during the SKUSA CR125 spigot testing.

Shouldn't that read raising the spigot centerline Wob?

**RomeuPT** · 14th June 2018, 00:13

Originally Posted by wobbly

Romeu, the Iame isn't strictly a flat top, it has a 7mm wide 5* conical angle on the timing edge, then an almost flat top ( 1mm rise ).
Thus its a combination really of a dome and flat top.
I feel this is better than Yamaha had with a very small angled edge, then a flat.
Due to the flat top area of the piston the plug is already alot closer to the piston than would be the case with a dome.
So i have used a bathtub ( to get it even closer ) but yes if I was permitted to , i would drop the plug even more with a toroid.
In the KZ application I have already established that the bathtub is better than the normal hemi shape when using the stock TM 4* straight conical piston
but as the class rules mandate pouring 13cc down the plug hole , using a proper toroid isnt possible.

The Honda 250 had the matching oval to round transition spigot for many years before the 125 GP engine did , but to my knowledge they didnt discover the advantage of dropping the spigot centerline
to make the floor of the duct and the spigot co-linear.
I found that during the SKUSA CR125 spigot testing.

Thanks

Yes I know its a combo of the two types, I have got the Iame piston and now need to design a chamber to suite, I think I will modify a NX4 stock chamber I have to more cc..

The spignot exit will be offset then?

**guyhockley** · 14th June 2018, 04:02

Originally Posted by F5 Dave

My T125 is a marvel of drilled pins, slingers and all sorts.

I'm away from my workshop at the moment, but I think Vic Willoughby said Helmut Fath used end fed cranks on Phil Read's TD2 for double the crank life.

**Tim Ey** · 14th June 2018, 04:40

Originally Posted by katinas

Some interesting things in this sketch of Honda NSR 2001/RSW 250 2009 GP engines.
Staggered reed block and longer conrod ( about 110 mm) on latest RSW (Aoyama), no steps cylinder/spigot, reed block angle on NSR ......

Oh My!
I totally love technical drawings of twostroke stuff!
Where did you get that from? Is there a chance that there might be more? :-)

Regards
Tim

**Flettner** · 14th June 2018, 07:59

this EFI project has an old school autolube, feeding into the end of the crankshaft. Shaft is hollow, crank pin is drilled ( carbide drill) so oil can be delivered direct to the bigend.
Cable operation will be connected to the power valve spool, not throttle cable.

**wobbly** · 14th June 2018, 08:56

Yes sorry Frits, with the spigot CL symmetric, the angle of the floor and roof of the oval to round transition are the same.
ie both steepish.
But if you lift the spigot CL upward, the floor angle straightens out - to where you can eventually make it co - linear with the duct exit.
In this case the roof angle from the top of the oval, out to the top of the round header entry, is VERY steep.
I am even starting to vaguely think this just might be like having a deto button in the header roof , the steep angle facing the pipe may shield the duct from infra red heat
or the floor shape promotes return flow up the ski jump - but retards it along the duct roof.
Who knows, not me - but as usual the dyno she dont lie.

**guyhockley** · 14th June 2018, 09:25

Originally Posted by Flettner

this EFI project has an old school autolube, feeding into the end of the crankshaft. Shaft is hollow, crank pin is drilled ( carbide drill) so oil can be delivered direct to the bigend.
Cable operation will be connected to the power valve spool, not throttle cable.

This design was supposed to run carbon pistons "dry" and use no oil, hence the oil-seals on the crank pin. Designed, and supposed to have been built by a bloke some consider a genius and others regard as "a bullshitting fantasist with no business morals". Don't think it ever made metal.