ESE's works engine tuner

[ajturbo]

May I make another suggestion !

I m not sure of the bike, and have a little bit of an idea of the tracks you run on ( would they be the same as Ruapuna kart track)

anyway that Dyno run is peaking at 12? do you even get to 12 on the tracks you run at ? , its the haul out of the corners

Id be moving that peak down to where you actually spend most of the time... and thermal efficiency

2 strokes have a nice chamber, but if the flow is separating anywhere along the path or out the exhaust, even separating IN the exhaust

your flow, what ever will get the mixture in there is looking good .... but if it isn't converted. its wasted, what are your Mach numbers for those ports? ALL ports , crankcase , transfer , inlet ?

Me I bumped up my BMEP and now have a mighty heat issue and its a toughy !

i am Enjoying this thread , but don't spend too much , that is real easy to do ,,only to say ,,,ooopps ( I think you know that ! ,,,,I am still too dumb to realise ,,,so continue to waste far too much money ,,,,,though it is getting better as I improve my simulation skills )

Stephen

so your talking about an engine that pulls like my buell (or a school boy if your like that) from way... way down low?...

[F5 Dave]

What I'd be concerned about is that the retarded ignition gets the revs pretty high for an old suzi crank. But clearly there would be a nice gain in a curve closer suited between the two.

[bucketracer]

Another handy rule of thumb for those who find working with Port-Time-Area irksome.

Bells book has some handy rules of thumb for port timings for the Ex, In and Trans but nothing for "Blow-down" the period between exhaust opening and the transfers opening.

I found this handy rule of thumb for blow-down in Gordon Blair's book "The Basic Design of Two-Strokes", and it is, that the number of degrees of crank rotation for sufficient blow-down time will be around the degrees of crank rotation it takes for the piston to uncover a 1/4 of the exhaust port window area.

So for wide bridged ports and ex ports with supplementary side ports the number of degrees required for blow-down will be less than for narrower higher single exhaust ports.

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[TZ350]

Thanks for that Bucket, if you can find it on the net I would love a link to it.

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[bucketracer]

Will see what I can find.

[TZ350]

What I'd be concerned about is that the retarded ignition gets the revs pretty high for an old suzi crank. But clearly there would be a nice gain in a curve closer suited between the two.

The crank is pretty beefy with high speed industrial twin row self aligning phenolic caged main bearings. A 22mm big-end (up from 19mm) and a Yamaha RD350 rod with oiling slots hand cut into it with a small slotting blade in a 4" grinder. The big-end itself is a RGV unit as is the little end.

But yes 11-12K is a bit much and way past what the teeny weeny 24mm carb can properly pass.

The inlet port time area for a 24mm carb and inlet port/timing combo worked out good for 9500 to possibly 10500 at a stretch.

My plan was to tune for 10500 or a bit less, some how its crept out to 12,000 and must be getting strangled by the carb.

Give me a day or three and I will do a Time Area Analysis of the ports and write up the chamber dimensions.

I figure if I could get it peaking at 10k I could possible keep the hp and have a wider power band.

The best bike so far in the Team ESE group is the GP that's been modified the least. 1.75mm of the barrel, and "O" ringed, RG250 chamber and KX80 ignition, no other changes. It would be interesting to compare time areas with it.

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[TZ350]

Save the stuffing around and go buy one of these http://www.ignitech.cz/english/aindex.htm

I hear you, I have even visited the sight and checked them out. I havent given up on my RM setup completely yet but I am starting to have my doubts.

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[bucketracer]

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The best bell mouths are those that are short and fat! http://www.profblairandassociates.co...mouth_Sept.pdf

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[TZ350]

Some interesting links and down loadable PDF's I came across while looking for Gordon Blairs book on designing 2-strokes.

Links

4-Stroke valve spring design
http://www.profblairandassociates.co...T036_Blair.pdf

Pneumatic vs Steel valve Springs
http://www.profblairandassociates.co...ngs_Vs_Gas.pdf

Acceleration testing of a 2-Stroke
http://www.2stroke-tuning.nl/media/a...dyno_blair.pdf

Tuning a cart engine exhaust
http://www.bkarting.com/tech-docs/expchmbr.pdf

Advanced 2-Stroke tuned exhaust design
http://www.freewebs.com/jsu_tiedosto...003exhaust.pdf

Intake bell mouth design
http://www.profblairandassociates.co...mouth_Sept.pdf

Designing a race 4-Stroke
http://epubl.ltu.se/1402-1617/2006/0...X-06099-SE.pdf

Small 2-Stroke direct injection retro fit.
http://www.envirofit.org/media_docs/...or%20Small.pdf

A look at the books ava for designing and testing engines
http://store.sae.org/catalog/powertrain.pdf

And I am still looking for Blairs Book.
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[bucketracer]

A whole bunch of articles from Gordon Blair in Race Engine Design mostly 4-Stroke, so more for the FXR boys.

http://www.profblairandassociates.com/RET_Articles.html

PS Gordon Blairs book on basic 2-stroke design refers to the returning pressure wave in the expansion chamber as a "Plugging Pulse".

I have seen plenty of references to "Supercharging" but that is the first time I have seen it referred to in any literature as a plugging pulse.

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[TZ350]

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Another from G Blair on 2-stroke direct injection. http://www.etsmtl.ca/zone2/clubs/qui...paper_2009.pdf

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[bucketracer]

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Lots of interesting Vid Clips of DIOSpeedDemon porting and developing his motor the Gordon Blair way.

http://www.youtube.com/user/DIOSpeedDemon

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[TZ350]

.
"The work by Blair, Kenny and others at QUB showed that the velocity of the gas across the width of the transfer port was virtually constant, but that the direction of the gas stream varied at all points in the cycle.

For a test cylinder, having a transfer port height of 12 mm the results were

Port open..Angle one Angle two
.......mm...(Horizontal)(Vertical)
Fully open
........12.....10.....14
........10.....10.....16
........8......14......19
........6......18......26
........4......21......33
........2......25......34
........0......-........-
where "angle one" is the horizontal divergence of the gas stream away from the port direction towards the exhaust port (Fig 10 ), and "angle two" is the vertical divergence of the gas stream away from the port direction upwards towards the cylinder head (Fig 11 ).

We see that the flow bends upwards and forward towards the exhaust port as the cycle proceeds and the piston rises to shut the port. In their experiments, Kenny, Blair et al tested six different transfer shapes, the best two are presented here. Shape "A" (Fig 12 ) gave the best performance at all rpm, but was only marginally (2% - 3%) better than shape "B" (Fig 13 ), which is very similar to the shape of most Japanese ports, and is more easily achieved adapting an existing cylinder than shape "A". "

Abstract taken from http://www.lortim.demon.co.uk/vsih/pistons.htm

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[Chambers]

The team ESE bikes are making enough power but the handling is letting us down and my bike is too hard in the back-end and bounces all over the place going over bumps.

I have a set of good shocks but no idea of the spring rate. So I have to figure out what they are so I can get some softer ones.

This is the setup I lashed together to measure how many Kg/center meter they are. The scales are preloaded to 10 Kg with the spring in place then the press is used to crank on another 10kg. The distance the spring collapses is measured under the 10kg load and with a bit of simple arithmetic we can workout the Kg/mm Kg/cm lbs/inc or whatever.

Tuti spent a happy couple of hours measuring all the springs we could find.

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[SS90]

As it turned out the power/torque curve with the retarding ignition was worse in every way compared to the fixed ignition except at over rev. I guess the amount of retard (about 15deg) with this ignition is too much to be able to get it right at both ends of the rev range.

The one exciting point is the 500rpm over rev at the top. I will try this retarding idea again with a unit that has less retard, maybe 5-7deg.
What I would like is the fixed ignition curve to 10,500revs then have the retard kick in for over rev to 12,000.

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I havn't found the same / similar results as this in my experience Teezee, so I have to think the same way as Sonic V.

The correct curve for any given engine really is different to the next.

As a VERY rough guide (gulp) I suggest that such an ignition curve would be good for chambers engine, with it's "non squish" head, and "old school" expansion chamber.

Because you have a "squish head", the curve you will end up finding suitable will be somewhat different for something, that for example, has a "non squish" head.

When I started looking at ignition curves, I spent a bit of time looking at what japanese manufacturers where doing in the early to mid eighties (when all the "new generation" stuff was made available to the public)

A good one to look at is the Yamaha RZ250R.

The cylinder head design is essentially the same as Chambers, and the expansion chamber is not to far removed either.

On RZ's (I can try and find the curve if you need it) the ignition curve is essentially the same as the one you have just tested.

And don't forget the RZ's had power valves..... the is a direct corrolation between high retard ignitions, older pipe designs,non squish heads and power valves.

The cylinder head design and the variable swept area/trapped compression is the main reason

The difference being that, because it is for a "road" bike, it runs 17 deg in the lower RPM, (better idle) and advances up to (I think) 25 deg at 7,000 and retards back to 5 deg at 11,000 (from memory)

Holding static at 25 until 7500 RPM would work just the same, albeit a crap idle.

My experience has shown that, when using a "squish head", while the turbulence increases with RPM (suggesting more retard is needed), it seemed that many other factors influenced the curve that best suited, and less retard that I predicted was required!

As SonicV pointed out, the exhaust pipe pays a BIG part in the suitable ignition curve, as does cylinder compression, head design,scavenge patterns and swept area (trapped compression)

I have found that because I get the best results (rideabilty wise) when I use non squish head design, the engines I build like quite a bit of retard (the same as you have on your test engine essesentially) and, as I have my own "fomula" for building 125cc two strokes, I know how to build an engine that benefits from such a curve.

With your engine, much like you suspect, I agree that more like 7 deg retard would be suitable (most likely).

In some parallel universe, where you HAD to run that ignition, you could build an engine that was more suited to that curve, but obviously it is sensible to try a different ignition!