ESE's works engine tuner

[TZ350]

That is revving pretty high, the crank may(will) not last if you under gear it & let it spin out there too long.

Yep the crank expired Sunday.

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[F5 Dave]

Oh, sorry to jinx it (perhaps to the minute if it expired at post time of 10:48?), but as you know 2 strokes that sit for ages are a problem, big end could easily have had some rust forming that strips away the plating when used in anger. I'd be tempted to add a couple of degrees to the baffle to cut the power off earlier (didn't even see if it had a proper pipe).

I'm hoping to be able to ride again in September, maybe race Oct.

[TZ350]

but as you know 2 strokes that sit for ages are a problem, big end could easily have had some rust forming that strips away the plating when used in anger.

It had sat for quite a while. barrel/piston is ok and the porting work looks very professional. The rod was the old no slots kind so the replacement will have slots and better oilling. Thanks for the tip about the baffel cone. The pipe is home made but not of the standard of the rest of the bike.

I have a GP125 pipe to make too and another to design and make, allways more projects than time.

Have fitted and run the GP125 with a retarding RM125 ignition now (last night) so of to the dyno again to dial it in, more $$$$$.

Glad to hear you are healing up, it has taken such a long time.

.

[F5 Dave]

Yeah, no real progress until they put the plate in. Still should be good now.

[TZ350]

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Measuring the balance factor of our Suzuki GP125,s

The round bar is very nearly as good as knife edges.

Pic-1 Finding the counter balance by hanging washers of a hook attached to the conrod.

Pic-2 Determining the mass "C" of the counter balance.

Pic-3 Determining the mass "R" of the reciprocating weight.

The balance factor B = C counter balance mass divided by R reciprocating mass.

The balance factor is.......B = C / R

As measured by me, it turns out that the balance factor of:-

A standard Suzuki GP125 is 69%

A Standard Suzuki GP100 is 76%

A GP with alloy plugs in the counter balance holes becomes 58% for the 100 and 52% for the 125.

When we recently dyno'ed two of our bikes with cranks that had the same 69% balance factors. The RS frame vibrated much more than the original GP frame did.

For us this supported the notion that there is no one correct balance factor, as the right balance factor is the one that works with the frame that the motor is mounted in.

I think it was SS90 that said that the balance factor that works best in a high output 2-stroke will tend towards 50% as the rev's go up. And we found that, that pretty much happened. When we put alloy plugs in the crank balance holes to raise the primary compression ratio. As an unintended consequence the balance factors changed and become less 58-52% and the engines became noticeably smother at higher rpm.

I asked Thomas about this and he said that motors with a wider spread of power and that are operated over a wider rev range like the std GP engine tended to have a higher balance factor than ones with a narrower power band like our hotted up engines. That made sense when you look at the Kawasaki 250 & 500 4-stroke MX bikes that have a BF of 60% and the big 4-Stroke cruisers & sport bikes at 70+ %.

It seems that the wider the rev range the motor is going to be operating over the higher the suitable balance factor will be. Its easy to relate this to the Kawasaki 4-stroke 250 Mx bike, same revs but wider power band, and a BF of 60%.

I have a Honda RS125 crank to look at next, I suspect it will be 50% but for different reasons.

Anyone can open a free account with Scribed where they can download "Tuning for Speed" by Phill Irving. http://www.scribd.com/doc/15392252/T...rcycle-Engines

Phill Irving talks about CrankShaft Balancing and Balance Factors on pages 107 to 110 of the book which can be found on page 61 of the PDF.

The balance factor is C / R

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[Brian d marge]

How I balance my engines

from top of head

There is the point of change in motion , hard to determine , geometric ot moment of Inertia

anyway the wieght is slightly different , as the position is slightly different

So i machine up a lead weight that fits around the crank pin as close to the centre line of the pin as possible ( as the mass acts around the pin ) even that is a bit big as the mass of the lead wieght is away from the centre line ,,,of the crank pin

then press up the assembly run on knife edges ( i made a jig using bearings , to try and reduce friction loads ....) and it should come to rest in a different spot after the lightest of touches

thats just the way I did it

Stephen

[k14]

I have a Honda RS125 crank to look at next, I suspect it will be 50% but for different reasons.

Can you work the balance factor out for the RS125 by just weighing the parts of the crank (as you did in the above post) because it has a separate countershaft? Or do you have to weigh the countershaft too?

[TZ350]

Can you work the balance factor out for the RS125 by just weighing the parts of the crank (as you did in the above post) because it has a separate countershaft? Or do you have to weigh the countershaft too?

I was able to weigh the RS crank the same way and the crank itself came out at 50%. The counter balance also looks to represent 50%.

I don't have all the RS here but after looking at the H100. The way I think it works on the RS is that the counterbalance spins twice as fast as the crank.

I said the counter balance "represents 50%" as I don’t think it weighs 50% but because it spins twice as fast as the crank its inertial mass becomes 50% as it spins around.

This allows the counter balance to work with the crank top and bottom to cancel out the piston and then it cancels out the counter weight of the crank mid stroke twice a revolution.

So it goes something like this.

Top:- Cranks 50% plus Balance Shafts 50% going down together cancels the Pistons 100% coming up.

Mid going down:- Cranks 50% cancels Balance Shafts 50% as they are now pulling in opposite directions.

Bottom:- Cranks 50% plus Balance Shafts 50% coming up together cancels the Pistons 100% going down.

Mid going up:- Cranks 50% cancels Balance Shafts 50% as they are now pulling in opposite directions again.

To do this the Balance Shaft has to rotate twice as fast as the crank.

So in theory you get a 100% balancing of the engine but really its just a bit of clever push and shove. As the crank is still 50% out of balance and when it pushes side ways the counter balance shoves it back and then twice a revolution the two of them gang up on the piston and pull it back.

It looks like the engine is balanced but there are really a lot of stresses going on inside.

I am not sure how you would go about matching the counter balance shaft to the crankshaft without making some comparitive weight measurements and doing some maths that takes account of changes in inertial mass with changes in rpm as it would not be a simple 50/50 weight thing for the whole rev range.

As the inertial mass of the counter balance shaft will change more than the crankshaft does with changes in rpm. So I guess you tune the weight of the counter balance shaft to work best in the rev range you want to use.

The balance factor of the RS crank is C/R = 50% of the reciprocating mass.

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[TZ350]

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BMEP introducing some Science to comparing comparative engine performances.

Brake Mean Effective Pressure....Engineering Term & Method for Comparing Different Engines

You can take the performance of say a 125cc Vespa and compare its performance to any other engine whether they are 4-stroke, 2-stroke, supercharged, turbo charged, Diesel, petrol, nitro burning dragster and get a clear idea of whos engine is performing best.

BMEP-PSI = Average Cylinder Pressure in PSI

Two Stroke -- BMEP = HP x 6500 / L x RPM

Four Stroke -- BMEP = HP x 13000 / L x RPM

L = Displacement in Litres (80 cc = .08 Litres) (700 cc = .7 Litres)

So 27.1*6500/0.125*7800 = 180.7

BMEP of a 27.1hp 125 at 7800rpm is 181psi.

BMEP can be used to evaluate power claims be it at 7500rpm or 14,000 and 4 or 2-stroke.

Most air cooled 2-stroke engines will be lucky to better 135psi and water cooled 160 or so. A Honda RS is about 160 and F1 4-stroke race engines manage a bit over 200. So by doing the numbers on your engine (or any engine) you can get an idea wher your at in the development stakes.

An explanation of the expansion chamber design process proposed by Gordon Blair.
http://members.bellatlantic.net/~vze...es/expcham.htm

A very through treatment of 4-stroke engine design fundamentals by Gordon Blair. http://www.profblairandassociates.co..._to_basics.pdf

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[bucketracer]

Something for you TZ, I went looking for references to blowdown degrees required but got side tracked by this article on measuring ports, and I was particularly impressed by how they measured port angles.

www.kartweb.com/TechArt/2Stroke/chapter2.doc

[Brian d marge]

The BMEP in my Enfield is around the 90 to 125 psi cant remember off top of head

the problem is the the fuel conversion efficiency , modern cars are up round the 30 % my Enfield is around the 16 %

Then there's the heat and control of ...........

Stephen

[TZ350]

Well that was fun, an afternoon on the dyno with Gavin from Henderson motorcycles dialing in the RM retarding ignition. The idea was to have the ignition over advanced in the lower revs to pickup some extra torque and then retard back for max power as the revs went up.

Spent a happy couple of hours finding the sweet spot in the retard curve. Went about this carefully 2 deg at a time until we had maximized the power output. Interestingly again as the retarding ignition was dialed in I had to lean it out on the main jet, to get best power.

Turned out to be a total disappointment, but I really should not have been surprised. Especially as after a bit of thought I had started to suspect that an engine that originally got fatter and broader as its over advanced fixed ignition was retarded would not respond well to another over advanced ignition.

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. Didn't SS90 say that less retard than 15 and more like 5-7deg might be better? he could be right. The RM unit is probably better suited to one of the other ESE bikes that still has the large open no squish head like the early RM did.

Pic-1 Retarding ignition, curve "R"

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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[k14]

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

Best money I have spent on my CB. Still haven't had it on a dyno yet so have only been changing the timing by my own feelings. I can keep up with most of the FXR's down the straight on the CB now. Something I couldn't even remotely manage with the standard CDI.

[sonic_v]

Well that was fun, an afternoon on the dyno with Gavin from Henderson motorcycles dialing in the RM retarding ignition. The idea was to have the ignition over advanced in the lower revs to pickup some extra torque and then retard back for max power as the revs went up.

Spent a happy couple of hours finding the sweet spot in the retard curve. Went about this carefully 2 deg at a time until we had maximized the power output. Interestingly again as the retarding ignition was dialed in I had to lean it out on the main jet, to get best power.

Turned out to be a total disappointment, but I really should not have been surprised. Especially as after a bit of thought I had started to suspect that an engine that originally got fatter and broader as its over advanced fixed ignition was retarded would not respond well to another over advanced ignition.

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. Didn't SS90 say that less retard than 15 and more like 5-7deg might be better? he could be right. The RM unit is probably better suited to one of the other ESE bikes that still has the large open no squish head like the early RM did.

Pic-1 Retarding ignition, curve "R"

What I would like is the fixed ignition curve to 10,500revs then have the retard kick in for over rev to 12,000.

.

I would not give up on your ignition just yet. I usually find that the fitment of a retarding ignition usually requires a different exhaust pipe, particularly if the original is a touch on the short side. It strikes me that your engine is now working at revs that are too high for the exhaust port time area. A longer pipe that better matches your exhaust port time area and the new peak power ignition advance could provide big gains.

Would be interested to see your exhaust duration and exhaust system tuned length (piston to end of reverse cone). In fact whilst you are at it you should calculate your exhaust port time area.

I have used the rm80 ignition on different applications and it has worked well. However, at peak power speed have uasually had an advance of about 7 degrees. This requires the exhaust to be spot on to work. Judging by your description of the rm125 ignition, it sounds as if the two might be very similar.

[Brian d marge]

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