ESE's works engine tuner

[richban]

Huh ?

Indeed it isn't; not when you reduce the offset, which will increase the trail.

Funny. In my head is was the opposite as well. Maybe its a southern hemisphere thing or just people from Tauranga.

Well so far with the RGV project the main focus has been on the handling after riding one on the track. So now the frame will be sent to a secret location to have 2 degrees knocked out of the head stock. Also the swing arm will have a small amount of work so I can run a shorter chain. With bugger all budget this should transform the bike. I plan to run around 25-27mm rear sage and around 38mm in the front. This should have the bike running on track with 84 - 85mm of trail with a rake of 22.5 and shorter by 25mm from the massive 1380 it is now.

Well thats the plan anyway. Not sure what tyres I will end up with yet.

Edit: But the rubber will be stock profiles.

[F5 Dave]

.. . So now the frame will be sent to a secret location to have 2 degrees knocked out of the head stock. . . .

They probably told you they were going to section & weld. They told me about this really sturdy steel beam, about 15kph will sort out a degree, but if you're brave 20k will do a couple.

[Frits Overmars]

Shit I cant peek sideways at a lesbian without you looking over my shoulder Frits, dead right about the offset number - of course. Glad someone is awake.

I devour your every word, Wob

[wobbly]

If I could stand up, you would be keeping me on my toes.
Thanks for the help.

[richban]

To do a toroid properly you need to drop the plug tip to approx 6mm from the piston crown.
Means welding the chamber and counterboring the plug seat face.
Very difficult to do repeatable and accurately unless done on CNC.
I model the piston dome and the head shape in SolidWorks to generate a solid then I have an accurate curve the toolpath follows and a calculated volume.

Some pics of the Heads.

Somebody has had a go at one and machined one wonky then stopped. The other one is untouched but has big pits in the squish area. Should be fine after skimmed and squish machined in.

There looks like quite a bit of meat in the casting. Plug tip looks like is in the correct place already (The piston crown will be flush with bore). What do you think Wobbly?

[wobbly]

Yep, looks fine.
The flat squish area should have 0.1mm taper upwards from the bore edge.
As I found the piston will clip the inner edge first when the vertical gap is at the mechanical limit for the rpm.
This is the sort of shape you are after.

[richban]

Yep, looks fine.
The flat squish area should have 0.1mm taper upwards from the bore edge.
As I found the piston will clip the inner edge first when the vertical gap is at the mechanical limit for the rpm.
This is the sort of shape you are after.

Fab. Thanks once again. Now time to try model it up.

[F5 Dave]

What sort of gas will you run? Comm ratio expecting to run?

[richban]

What sort of gas will you run? Comm ratio expecting to run?

Avgas. Not sure, Whatever keeps the Squish velocity under the number Wobbly gave me. Going around in circles at the moment.

Looks like before I can design my head I need to figure the exhaust port timing. I had a play. Squish band width is 8.5mm and 0.75 squish. I need to measure up the heads again to see how much I need to machine of the top to get the inner dome diameter small enough. Now I see why so many people use inserts.

Learning all the time.

[Neal]

What squish area ratio are you aiming for ?

[136kg136ps]

Wob,would that 6mm plug tip to dome figure hold true in any bore size?

[richban]

What squish area ratio are you aiming for ?

50% at this stage.

[wobbly]

You dont really need the Ex timing to establish the head geometry, and yes the 6mm number seems to work with most " usual " combustion chamber geometries.
Avgas works with anything from around 192 to 202 Ex duration at around 15.8 full stroke.
Smaller bores or lower bmep setups can go 16.2, big bore oversquare or very high bmep like slightly less at 15.5, air cooled of course needs alot less.
As long as you hit the lower mechanical squish depth limit, then adjust the width to hit 38M/Sec MSV you will have good squish turbulence that helps the flame speed - reducing any tendency to deto
the end gasses.
That MSV number is meaningless in the context of all but hitting the head when within the normal rev limits, but as a guide it works every time.
The sharp bowl edge increases the flame speed, and a very deep angle away from that edge into the bowl is synergistic by pulling the turbulence further into the combustion space, again increasing the flame propagation speed,
over a wider band.
Pushing the combustion parameters this hard means a digital ignition is mandatory to balance the timing against the high peak cylinder pressure now being generated.

[G Jones]

As long as you hit the lower mechanical squish depth limit, then adjust the width to hit 38M/Sec MSV you will have good squish turbulence that helps the flame speed - reducing any tendency to deto
the end gasses.

I wonder if you would mind telling the method for working out the " lower mechanical squish depth limit" ? - is there a simple rule for that - or is it much more complex ?
Thanks

[wobbly]

No free lunch today except that its all been done before and in most cases a guide is available.
It depends upon the stroke length, the piston weight and the crank integrity.
Suffice to say that a 125 single will usually go down to 0.65mm when spinning to 14000
A 250 twin like the RGV with a single middle bearing will go 0.75 spinning to 12,000
A 250MX type with 72mm stroke is OK at 1mm spinning to 11,000.
But I stress again, as I dont want the Honda faggots off their forum abusing me that the NSR wont rev if taken below 0.8mm - the ignition has to be optimised
to work with a combustion chamber that is designed correctly, and does actually do what its supposed to.
A stock PGM simply wont cut it - but then we wont be using HRC parts, so they just cant be any good at all, as everyone should realise.