ESE's works engine tuner

[Martin1981]

How could ryger say that the engine has 70rwhp if it never was dyno tested?

[Muciek]

How could ryger say that the engine has 70rwhp if it never was dyno tested?

Yes Sonic, it was dyno tested. Yes Husa, he did have biscuits; they were chocolate-clad.

It was.Btw TZ any progress made with RGV cylinder?

[breezy]

You need to understand the real meaning of the term " choked flow " in relation to the 2T cycle first.
So read the paper I have attached, as this is the best I have seen on the science involved.
In reality most people have a misunderstanding of the effect,in that once the local gas velocity is sonic, no increase in VELOCITY can occur.
But , the mass flow rate CAN increase, under the conditions stated..
I went thru this exercise a while ago in relation to determining if sonic conditions occurred when using a nozzle in the Ex duct, or in the tailpipe.
Short answer is that if a normal sized venturi or duct/pipe restriction are used, the local velocity does not exceed Mach 1.
I found that in the sim ( where determining the local gas velocity at any point is trivial ) as soon as you approached sonic conditions, power went down dramatically.
From this I concluded that the energy required to create sonic flow is very high, and this appears to detract very quickly from the energy being used in the pipe for expansion,compression
and stuffing.
My logic may be faulty, but the end result of sonic conditions for sure are not.

And one small point in relation to blowdown.
Port stagger, front to rear, uses the remnant blowdown pressure ratio at the transfer opening point, to affect the scavenging regime.
Remember, no flow can occur until the pressure ratio at the port face goes negative, thus until the pressure in the duct exceeds the cylinder pressure, flow will stall, or in a worst case
it will be reversed back down the transfer that opens first.
This short moment in crankshaft rotation, is enough to affect the distance traveled by each transfer stream in turn,and is why a KZ2 engine needs the A port opening first - as with no PV
it needs the " natural " effect of that regime to widen the powerband.
An Aprilia on the other hand uses reverse stagger, with the B/C ports opening first, that has the effect of boosting peak and overev power by its change in the scavenging pattern, along with the bigger STA
available from the wide B port being high as well.

Thanks for reply, given me something to contemplate.

[FastFred]

Heck yeah. If you lightly centre punch the piston the divets will be the riding surface which will flatten over and you will effectively decrease the piston clearance so it will be like new.

You are on to it, knurling old pistons to take up the slack was the standard procedure back in the day. A knurled piston only needed half the clearance of an ordinary piston.

and

Welding rod is expensive, some JB weld should fix that right up if you are just putting it on the inside which is cooled by the gas should be fine.

Pretty sure TeeZee has already showin you can successfully glue the inside of a piston .....

Page 231

you can trust me.

Sure can ....

[wobbly]

Not only were Rolfs fingers tapping the paint cans, they were up teenage girls dresses as well.

[2T Institute]

Yes Sonic, it was dyno tested. Yes Husa, he did have biscuits; they were chocolate-clad.

what no almond speculaas ?

[peewee]

alittle more progress tonight. besides not being the greatest welder, maybe even the worst, what you guys think ?

[TZ350]

Looks good, I particularly like that you have deliberately learnt new skills from scratch so you can do this. The true Buckateer way.

Is this cylinder going to have a rasied exhaust port floor dam?

[ken seeber]

You are on to it, knurling old pistons to take up the slack was the standard procedure back in the day. A knurled piston only needed half the clearance of an ordinary piston.

Sure can

At Orbital, we used to centre pop new design pistons on a grid pattern, each centre pop creating a small mound of aluminium around the pop. Then it was run in an engine for a little bit at max power. Taken out, put on a Talyrond roundness measuring machine and the height of the mounds, relative to the surrounding surface was measured. Then, if the mounds were high, then a new profile was developed based on the profile of the heights. This was fed into a Takisawa camless piston turning CNC lathe and a new shape was produced. The goal was to be able to minimise the clearances for performance, durability and NVH reasons. Not completely perfect, but not too bad.


rolf harris was/is a total sleazebag and a knob jockey of the first order and all art awards etc that he seemed to gain in Perth (where he came from) have been removed. Hope he rots and soon.

[TZ350]

Optimising the piston profile that way, now that is very clever....

[wobbly]

When the cylinder has been soaked in 2T oil for years it impossible to get nice a TIG weld without contamination, no matter
how much you clean or acid etch the surface beforehand.
Here is a KTM250 I am doing for kart roadracing.

Re doing the piston shape - we finally got the shape right on the BSL by getting the pistons skirts HPC coated to give zero bore clearance.
Then ran them long enough for the hot piston shape to rub hard enough to wear away the coating.
This was then measured the same way as Ken did it with the results going back to Vertex to reprofile the next batch.
It took 3 goes before the shape of the new ( 59.6mm ) piston was perfect, as proven by the fact we could then warm up a new set with
one heat cycle in the pits - and then go race immediately - no running in at all.

[F5 Dave]

So are super karts now restricted to singles?

[wobbly]

No, there is a class for production 250 singles.

[peewee]

i learned alot just in the last few weeks. 90% of my troubles were gas coverage related. had tungsten sticking out to far, torch tilted to far etc. once i realized that, everything got alot easier. heavy dose of helium sure helped also . machine was set at 135amps and mostly i only needed 1/2 to 3/4 peddle. straight argon struggled to get a good puddle at 200amps floor boarded peddle

[sonic_v]

i learned alot just in the last few weeks. 90% of my troubles were gas coverage related. had tungsten sticking out to far, torch tilted to far etc. once i realized that, everything got alot easier. heavy dose of helium sure helped also . machine was set at 135amps and mostly i only needed 1/2 to 3/4 peddle. straight argon struggled to get a good puddle at 200amps floor boarded peddle

Are you using DC or AC?