ESE's works engine tuner

**speedpro** · 20th March 2009, 19:59

Originally Posted by TZ350

It could be said that the transfer ports deliver the spread or range of power while the tuned pipe balances the delivery and availability of that power.

This is another thing I have played with on the dyno. I actually devconned up the boost port then dyno'd the engine. From memory it still made the same peak power but got real peaky. I then cleared the boost port amd devconned the main transfers and dyno'd again and then same procedure with the auxilliary transfer ports. I was surprised at how little differance it actually made. Having said that the engine was a troublesome wee thing it's whole life so it may not have been the best test subject.

**Pudding** · 20th March 2009, 20:05

I have been following this thread, and found it most interesting.

**SS90** · 20th March 2009, 20:38

Originally Posted by speedpro

This is another thing I have played with on the dyno. I actually devconned up the boost port then dyno'd the engine. From memory it still made the same peak power but got real peaky. I then cleared the boost port amd devconned the main transfers and dyno'd again and then same procedure with the auxilliary transfer ports. I was surprised at how little differance it actually made. Having said that the engine was a troublesome wee thing it's whole life so it may not have been the best test subject.

This is where it get really hard.

While there is significant power to be made, just small "errors", (a few degrees off), will have not so much catastrophic effects, but generally, you will see no gains, and can't figure out why.

Obviously, if you have a different set of auxillary ports (boost ports etc), the scavenge pattern that is best for your engine is vastly different from one with out (as they all must work together (or "match")

This is from Eric Goor.....,

Now the transfer ports are uncovered at about 120 degrees after TDC. The scavenging phase has begun. Meaning that the unburned mixture gasses are flowing out of the transfers and merging together to form a loop. The gasses travel up the back side of the cylinder and loops around in the cylinder head to scavenge out the burnt mixture gasses from the previous power stroke. It is critical that the burnt gasses are scavenged from the combustion chamber, in order to make room for as much unburned gasses as possible.

THAT IS THE KEY TO MAKING POWER IN A TWO STROKE ENGINE.

The more unburned gasses you can squeeze into the combustion chamber, the more the engine will produce. Now the loop of unburned mixture gasses have traveled into the exhaust pipe's header section. The gasses aren't lost because a compression pressure wave has reflected from the end of the exhaust pipe, to pack the unburned gasses back into the cylinder before the piston closes off the port. This is the unique super-charging effect of two-stroke engines. The main advantage of two-stroke engines is that they can combust more volume of fuel/air mixture than the swept volume of the engine. Example: A 125cc four-stroke engine combusts about 110cc of F/A gasses but a 125cc two-stroke engine combusts about 180cc of F/A gasses.

Like I said in much earlier posts, scavenge patterns are where modern two stroke developers are putting their research..... As not only does it make more power, it is also more efficient, and much lower in pollution.

Has anyone heard of the Aussie company orbital?

KTM have, and I hear that soon they will use their latest design, you can get a brief view of it here

http://www.orbitalcorp.com.au/orbita...torcycle2s.htm

Sadly, it doesn't go into to much detail, but the basics are, air is injected into the cylinder, BEFORE fuel is (to clear the cylinder), therefore obtaining a more "scavenged cylinder"

This is the best I have found on the BASIC system, like I say, their latest developments are pretty well kept secrets.

http://www.envirofit.org/direct_fuel_injection.html

**speedpro** · 20th March 2009, 21:10

I've been to the plant in Perth and had a look around. Very interesting place. Their OCP technology is already licensed to companies round the world, like Mercury marine. It's very good on the emissions front allowing the nice simple good ol' 2-stroke to do good.

**SS90** · 21st March 2009, 04:49

Originally Posted by TZ350

Waste heat to the cooling system is my current focus and I am interested in the practicalities of your cooling arrangements.

Do you think the shorter exhaust port tract on the Scooter reduces the heat takeup into the cooling system? The mean length of the GP125's exhaust tract is about 55mm long.

I would find it useful to know a Scooters head temperature and lower fin temperature measured near the exhaust after a good run, as a comparison. Would you measure it for me?

Because of your enthusiasm for crankcase compression ratios, induction resonance and unmasking the transfers I have become interested in looking at it again to see what more can be done with the GP.

But any practical work will have to wait for a little bit until I get to strip the motor for some gearbox maintenance that needs doing. Because of a damaged clutch nut thread I need to replace the main shaft.

.

At the risk of being labeled a Teacher again, I will just summate all the points I have raised in this thread, as these are all things that are required to keep an air cooled tuned two stroke running at reasonable temperatures...

1) scavenge patterns, get them correct for your engine, and not only will it make better power all through the range, it will also dramatically increase cylinder efficiency.

2) Compression Ratio, don't go too high. Gordon Jennings has an opening chapter called "Fundamentals", in there it talks of "flash horsepower engines", where the compression ratio is too high, so that for a few dyno runs (or laps) it goes like hell, but sharply drops off, and end up for the rest of the race having less horsepower than other competitors.

With respect, I think you engine falls into this category.

3) Correct primary compression. We have dwelled on that enough!

Remember that because you have such large port time areas, you already have a heat problem!

The high horswpower engines that I build run quite low cylinder compression, due to the fact that the first stage of devlopment showed me that what I gained when the engine was cold, I more than lost when it was hot......

You will find that high tuned scooter engines run quite low cylinder compression, and primary compression in the vicinity of industry norms.

You asked what temp one of my heads runs at.....using a lazer pointer tester, it reads 86 Deg.

This is because of the lower cylinder compression, as well as the scavenge pattern I use, rather than the forced air cooling. I assure you that a "normal" motorcycle engine, getting a clean stream of air, that is unhindered at the point of exit for the hot air (like a small frame Vespa) is far better at displacing heat.

I have attached 2 pics, the red one is a totally origonal 125cc Vespa cooling shroud, the green one is a 25 Horspower tuned engine....they have the same shroud, the tuning one has a ligher cooling fan/flywheel (for it's obvious benifits)

My opinion, if it holds any value to you, is not to worry about trying to increase the cooling ability, that's just treating the symptom, get your motor to run more efficiently (and thereby cooler), in doing so you treat the cause.

Some really clever guys build 23 plus horsepower 133cc CAST IRON disc valve engines, that are damn near indestructable... they don't have heating problems, mainly because they use the methods I have out lined here.

This is only written to help, not to ridicule, I hope it comes across that way, as that is how it is intended.

I also downloaded this on you tube just for interest...

http://www.youtube.com/watch?v=enDo5V82Oo8

**TZ350** · 21st March 2009, 06:58

Thanks for the reply.

From SS90’s post :-

2) Compression Ratio, don't go too high. Gordon Jennings has an opening chapter called "Fundamentals", in there it talks of "flash horsepower engines", where the compression ratio is too high, so that for a few dyno runs (or laps) it goes like hell, but sharply drops off, and end up for the rest of the race having less horsepower than other competitors.

With respect, I think you engine falls into this category.

The high horswpower engines that I build run quite low cylinder compression, due to the fact that the first stage of devlopment showed me that what I gained when the engine was cold, I more than lost when it was hot......

TZ350:- This is the Taupo experience.

From SS90’s post:- You will find that high tuned scooter engines run quite low cylinder compression, and primary compression in the vicinity of industry norms.

TZ350:- What corrected cylinder compression ratio would you expect to work in my GP? What works in tuned Scotters?

I built the motor and pipe modelled on Gordon Jennings description of what could be done with an early RM125 and the cooling improvements based on the known heat load in the cooling system and ideas from air cooled aero engines.

…………………………………...

A couple of interesting lines I copied from an automotive engineering book and posted earlier.

"Engine cylinders must be cooled to maintain a lubricant film on the cylinder walls and other sliding surfaces. The cylinders, heads, pistons and exhaust valves are cooled to prevent combustion knock or destruction of these parts due to over heating.

The heat removed from the engine by the cooling system is 25% to 35% on full load and may run as high as 40% on one third load.
An increase in speed reduces the heat lost to the cooling system.

60% of the cooling flow is directed to the cylinder and 40% to the head. The permissible compression ratio and output of air cooled aero engines depends on the efficiency of cooling of the cylinder head and have long fins 25mm to 50mm closely spaced 2.5mm to 5mm."

Interesting especially the close spacing of the fins.

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**TZ350** · 21st March 2009, 07:33

Originally Posted by speedpro

As an experiment last Saturday at the track I held the throttle so that the carb was only part open, effectively creating about a 24mm venturi. The motor melted due to pumping losses, or something.

From a couple of lines that I posted earlier.

"The heat removed from the engine by the cooling system is 25% to 35% on full load and may run as high as 40% on one third load. An increase in speed reduces the heat lost to the cooling system."

For the fuel consumed, less energey removed from the motor as work and more as waste heat to the cooling system.

Speedpro could this be what happened?

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**Pudding** · 21st March 2009, 08:41

Originally Posted by SS90

1) scavenge patterns, get them correct for your engine, and not only will it make better power all through the range, it will also dramatically increase cylinder efficiency.

"will also dramatically increase cylinder efficiency" by improved scavenging effectiveness and thereby "make better power"

Am I reading this correctly? Wouldn't this mean more waste heat to the cooling system or am I missing something? Please explain.

**Chambers** · 21st March 2009, 10:41

Originally Posted by SS90

My opinion, is not to worry about trying to increase the cooling ability, that's just treating the symptom, get your motor to run more efficiently (and thereby cooler), in doing so you treat the cause.

It seems people are hung up on the principal that: Make More Power = Make More Waste Heat.

Could you elaberate on "get your motor to run more efficiently (and thereby cooler), in doing so you treat the cause".

What do you mean by "more efficiently"

**TZ350** · 21st March 2009, 10:55

I am interested in the transfer streams that SS90 talks about.

The picture and quote are from an earlier post,

"A picture of my combustion chamber after Taupo. The wash from the transfer streams can be clearly seen. If anyone can tell me anything about their shape, I would be interested to know if they look right or otherwise."

I have been looking at the way the transfers wash the piston and head to determin their flow pattern.

When I get back to work Monday I will see if I can scan the relevant pages about Janti (transfer stream) patterns and post them.

Pics to make it easy for SS90 to tell me if this is what he is talking about or maybe elaborate on them or the head with a few scketches of his own.

I feel comfortable with 2-stroke theory, practical implimentation is the chalange.

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**speedpro** · 21st March 2009, 12:32

Originally Posted by TZ350

From a couple of lines that I posted earlier.

"The heat removed from the engine by the cooling system is 25% to 35% on full load and may run as high as 40% on one third load. An increase in speed reduces the heat lost to the cooling system."

For the fuel consumed, less energey removed from the motor as work and more as waste heat to the cooling system.

Speedpro could this be what happened?

.

I'm gonna have to work on my "piss taking" I see. Obviously a bit too subtle for most.
It's only the percentages that change as far as heat dissipation. At full throttle we may have say 1000BTU being dissipated in the cooling system assuming for simplicity that 3000BTU is being generated when the fuel is burnt & a 33% split. At part throttle the fuel burnt may only provide 2000BTU total but the % split changes so that maybe 40% is dissipated in the cooling system. 40% of 2000BTU is 800BTU so the cooling system is dissipating less energy than before. I've simplified this example and I don't know how the %s change but hopefully you get the idea. By reducing the throttle opening my engine does not get hotter, unless the %s are changed WAY more than I would expect.

A good point has been raised about compression ratios. Through vast combined experience of many fast bucket racers we think that depending on the actual air-cooled engine involved that 14.7-15:1 (swept+trapped/trapped) is about the max for good sustained power. My current MB is running at 15.2:1 and holds good power all day on any track. My new motor supposedly will be more efficient at trapping mixture in the cylinder and because of that, even with the water-cooled head, the compression ratio has been set at a lower value. I haven't relied on experience for the new motor as I think I got to where I could using that and went for "professional" help and advice. Time will tell if it was money well spent. Supposedly I should be able to dust Nigel good and proper as the same guy designed both our motors at the same time and we had our pipes laser cut at the same time, etc etc.

**TZ350** · 21st March 2009, 12:52

Originally Posted by speedpro

I'm gonna have to work on my "piss taking" I see. Obviously a bit too subtle for most.

Maybe not for everybody but you got me!

Thats right, more lost from less burnt probably wouldn't exceed less lost from more burnt for max power would it, could it?
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**TZ350** · 21st March 2009, 17:48

Two-Stroke Porting Software.

Plan your ports with this software using Jennings and Bells principles.

Porting Calculator and Port Analyser. $16.25 USD each. Paypal accepted.

These are based on Bell's and Jennings Books, makes it easy to apply their work to your motor. The program screen can be switched between Bell or Jennings and back again as you work.

Look at them here:- http://www.porting-programs.com/

I purchased mine over the net 8 months ago using Paypal and it was available for downland within hours.

Then when I claimed my free upgrade it to was quickly available.

Do go and have a look at his site:- http://www.porting-programs.com/.

.

**Yow Ling** · 21st March 2009, 19:37

Some stuff about fitting an aluminium sleve to an rz cylinder, not buckets but on topic. Its translated so it reads a bit spastic
http://au.babelfish.yahoo.com/transl...rUrl=Translate

original link http://www.geocities.jp/uda_vance/am-rz250r.html