ESE's works engine tuner

[SwePatrick]

Yes, very similar =)

here´s a video of what happens when adjusting.

https://www.youtube.com/watch?v=STrAI5Xz0vw

[ken seeber]

TZee you got me interested, particularly when I should be doing other stuff.

Ultimately, under most conditions, we possibly want an engine that has combustion every cycle, certainly eliminating the “ring…ding” nature of a carb’d 2 stroke under light load.

At Orbital, I remember at around the mid 90s when we first fitted the OCP system to a 50 cc Piaggio scooter. This used a 2.5 cc compressor that was driven by a spring loaded piston that was actuated via a roller running on an eccentric on the outside diameter of the engine crank, ingesting its air (and oil) from the crankcase. Once satisfactorily mapped, the thing combusted every cycle. To me it was almost annoying, especially at idle, in that it sounded so busy compared to a (misfiring) carb engine at the same speed.

Anyways it is clear, that a 2 stroke can be fuelled to provide reliable “cycle to cycle” combustion under all load & speed conditions, in this case with direct injection (no air flow measurement, just TPS).

Back to a carb engine, what happens when an engine isn’t going “ding”, when the engine is well off the exhaust providing any useful tuning effect, say at idle. Assuming a reed valve engine, one would think that the air/fuel charge per cycle would be very consistent. So, if we are pumping this repeatable air/fuel mass into the upper cylinder every cycle, why does it misfire?

Possible reasons are:
1. The fuel entry into the cylinder could be so stratified (due to low gas velocities) that the majority short circuits out the exhaust. This continues until the percentage of fuel increased until such time that as combustible mixture is present at the time of ignition. Then the “ding”.
2. That the exhaust gradually cools, altering the timing of a possible positive/negative pulse.
3. Ring leakage is such that the pressure in the cylinder, under non firing conditions, is less at EPO than EPC, back flowing some exhaust gas diluted charge in the cylinder.
4. Dunno
5. Dunno etc

Considering point 1. it could be argued that the scavenging gas flow from the injected B ports would take a shorter path out to the exhaust than say the C port, which one could imagine in the Schnurle scaving system would have the longest path. So, it’d be interesing to inject into this alone rather than the B ports.

As an aside, if we are dumping all this nice combustible mix into the exhaust for a number of cycles, why don’t we get a decent bang in the exhaust, similar to a “key bang” in a 4 stroke car, most usually blowing the muffler to bits. Dontchaeverrememberingdoingthisparticularlyinsomeo neelsescar???

I do recognise that this is a bit away from the sub 25% control problem, but there are some commonalities.

[husaberg]

TZee you got me interested, particularly when I should be doing other stuff.

Ultimately, under most conditions, we possibly want an engine that has combustion every cycle, certainly eliminating the “ring…ding” nature of a carb’d 2 stroke under light load.

At Orbital, I remember at around the mid 90s when we first fitted the OCP system to a 50 cc Piaggio scooter. This used a 2.5 cc compressor that was driven by a spring loaded piston that was actuated via a roller running on an eccentric on the outside diameter of the engine crank, ingesting its air (and oil) from the crankcase. Once satisfactorily mapped, the thing combusted every cycle. To me it was almost annoying, especially at idle, in that it sounded so busy compared to a (misfiring) carb engine at the same speed.

Anyways it is clear, that a 2 stroke can be fuelled to provide reliable “cycle to cycle” combustion under all load & speed conditions, in this case with direct injection (no air flow measurement, just TPS).

Back to a carb engine, what happens when an engine isn’t going “ding”, when the engine is well off the exhaust providing any useful tuning effect, say at idle. Assuming a reed valve engine, one would think that the air/fuel charge per cycle would be very consistent. So, if we are pumping this repeatable air/fuel mass into the upper cylinder every cycle, why does it misfire?

Possible reasons are:
1. The fuel entry into the cylinder could be so stratified (due to low gas velocities) that the majority short circuits out the exhaust. This continues until the percentage of fuel increased until such time that as combustible mixture is present at the time of ignition. Then the “ding”.
2. That the exhaust gradually cools, altering the timing of a possible positive/negative pulse.
3. Ring leakage is such that the pressure in the cylinder, under non firing conditions, is less at EPO than EPC, back flowing some exhaust gas diluted charge in the cylinder.
4. Dunno
5. Dunno etc

Considering point 1. it could be argued that the scavenging gas flow from the injected B ports would take a shorter path out to the exhaust than say the C port, which one could imagine in the Schnurle scaving system would have the longest path. So, it’d be interesing to inject into this alone rather than the B ports.

As an aside, if we are dumping all this nice combustible mix into the exhaust for a number of cycles, why don’t we get a decent bang in the exhaust, similar to a “key bang” in a 4 stroke car, most usually blowing the muffler to bits. Dontchaeverrememberingdoingthisparticularlyinsomeo neelsescar???

I do recognise that this is a bit away from the sub 25% control problem, but there are some commonalities.

Have you seen this one Ken
its a tiny high ultra pressure pump.
https://www.popularmechanics.com/car...tors-15682450/
https://news.engin.umich.edu/2012/09...sions-in-asia/
have a look at the fuel spray

kind of reminds me of a hilborne system only electric
http://www.freepatentsonline.com/20140117121.pdf

[SwePatrick]

I mentioned earlier to raise heat in the head with methanol.
This is my coolant scheme:



Original waterpump(increased flow) is drawing cool water from radiator as it should.
It is pumping the cool water into the cylinder above the exhaustduct in a 20mm line.
Then purple line is 12mm and is going directly to the radiator.
The red 12mm line from the head is controlled by a 90c thermostat, and then flowing into radiator.
The cylinder has restricted flow in the deck so there are a smaller flow than std going through the head.

If it is working?
Dunno yet, i´m testing clutch back and forth to get some baseline of what´s working.
Later this week i´m guessing i´ll put it on the dyno.

[lohring]

i wish there was more info about nitro in 2t engines. oil content in rc fuel ranges from 10%-22%. i havent figured out why. maybe parts last longer with more oil. ive been mixing 30% nitro, 16% oil, 54% methanol. if i lower the oil to say 12% and raise the methanol to 58% i wonder if i would gain power. maybe the engine would wear out faster. i dont know

I've been racing model boats a long time. In 3.5 to 15cc glow ignition engines we run 50 to 60% nitro with around 20% synthetic oil. Castor oil doesn't mix with high nitro, but castor/synthetic blends are also used. The oil is more for sealing the ringless pistons than for lubrication. Record setting engines often run up to 80% nitro. Other exotic chemicals like propylene oxide have been added in small amounts in the past. Raising the nitro % requires different head volume and some pipe length adjustment. It doesn't increase the rpm, but the boats can run bigger props at the same rpm. As was pointed out before, the nitro increases MEP and therefore torque.

In 26 to 36cc spark ignition, gasoline engines it was found that doubling the recommended oil mix increased power. Again, I suspect most comes from improved sealing of the single ring piston. By the way, it was common with older style 2 ring pistons to remove the bottom ring for more power.

We did a series of dyno tests on a 26cc engine with various fuels. See below. We found that it was hard to beat the standard pump gasolines even with added nitro and/or ethanol and methanol. Nitro mixes very well with ethanol containing "gasoline". Even Coleman fuel at 50 octane ran well. The reason was we didn't/couldn't change the combustion chamber volume, pipe, or ignition timing. All we did was richen the needle settings for peak power. Methanol and nitro fuels have a lot lower exhaust temperatures and need a different pipe. Nitro burns slower and probably could use more advance. The compression ratio of these industrial engines with one piece head and cylinder designs already have too low compression ratios. Head button engines have more power out of the box. We ran some nitro/methanol fuels in a head button engine briefly. The engine ran fine on 15% nitro, but burned off the plug electrodes on 40% nitro. Again we didn't try to optimize the engine for the different fuel since the race rules specify "gasoline". We did run VP's U-2 for record setting. That fuel was pretty far from pump gasoline.

Lohring Miller

[Nath88]

At Orbital, I remember at around the mid 90s when we first fitted the OCP system to a 50 cc Piaggio scooter. This used a 2.5 cc compressor that was driven by a spring loaded piston that was actuated via a roller running on an eccentric on the outside diameter of the engine crank, ingesting its air (and oil) from the crankcase. Once satisfactorily mapped, the thing combusted every cycle. To me it was almost annoying, especially at idle, in that it sounded so busy compared to a (misfiring) carb engine at the same speed.

I think that at closed throttle, with only the crankcase pumping, on each cycle a relatively small amount of air and fuel enters the cylinder, it's then mixed thoroughly with the exhaust gas by piston movement. It can takes a few cycles before the concentration of fresh mixture to inert exhaust gas is high enough to allow combustion.

What I found is that at closed throttle the intake vacuum doesn't vary much with RPM, so the pressure across the throttle plate and throttle orifice are both constant, therefore you get a constant flow rate with respect to time. So at higher rpm you'll see a lot more missed cycles than at idle, but the time between dings is not that different.

With the orbital system you were probably achieving a stratified charge, 2.5cc of air premixed with fuel, in a small pocket not mixed with the exhaust gas. Injection at the top of the cylinder means the pocket would be concentrated at the spark plug, allowing for fire every cycle.

I've almost finished porting my cylinder, it'll be receiving Uncle Flettner's B port TPI system. I'll be intercepting the injection pulses from the Microsquirt ECU with a separate controller which will read TPS, RPM and MAP to roughly calculate airflow through the intake, it will then skip injection pulses as required until the cylinder has enough fresh air in it to support combustion. The idea is to induce the engine misfires instead of trying to react to them in real time.

It will also interleave the 2 injectors at low pulsewidths for extra precision and control the oil and fuel pumps.

The only problem I see is when the injector does fire, a very rich mixture will be delivered through the transfers at the bottom of the cylinder, hopefully it will mix with the cylinder mixture and be combustible.
Even if it takes an extra cycle or 2 to mix it at low throttle % it's probably not a big deal.

[TZ350]

it could be argued that the scavenging gas flow from the injected B ports would take a shorter path out to the exhaust than say the C port, which one could imagine in the Schnurle scavenging system would have the longest path. So, it’d be interesting to inject into this alone rather than the B ports.

I have recently tried these combinations.

C for idling and low speed/power and B+B for high power.
B+B for idling and low speed/power and C for high power.
B one side for power B the other side for idling and low speed/power.
From one side of the crankcase firing directly into the inlet air stream for idling and low speed/power, B+B for high power.
From one side of the crankcase firing directly into the inlet air stream for high power and C for idling and low speed/power.

piston at TDC

C for idling and low speed/power and B+B for high power seems to work best for me.

With the C port on its own for high power it seems to drown when fuel demand gets up. But C works very well for idling and low speed/power.

With C port injection it idles smoothly at 2,000 rpm and with a carb it had to be 3,000rpm .... .... another mystery.

[Myles]

In 26 to 36cc spark ignition, gasoline engines it was found that doubling the recommended oil mix increased power. Again, I suspect most comes from improved sealing of the single ring piston. By the way, it was common with older style 2 ring pistons to remove the bottom ring for more power.

Lohring Miller

How much is a doubled amount of oil for those engines?

[Flettner]

may i ask, you ethanol / methanol junkies, what reeds are you running?

[lohring]

How much is a doubled amount of oil for those engines?

The factory recommends 25 to 40 to 1. That's around 3 to 5 US fluid ounces per US gallon. We ran 4 ounces per gallon in the past, but now run 8 to 10 ounces per gallon. Higher than 8 ounces didn't improve power in our dyno testing, but might help the big end bearing live at over 20,000 rpm.

Lohring Miller

[lohring]

If you were asking me, our engines are mostly piston port with a few disk valve specialty engines. The small nitro engines all have rotary valves.

Lohring Miller

[SwePatrick]

may i ask, you ethanol / methanol junkies, what reeds are you running?

Oem Kawasaki KX250 with mods and Polini petals
New V-force is bad,, the petals are getting soft, the resin dissolves.

I tried a boyesen cage with polini petals, no good.
There´s no rubber coating so the petals lands so hard it smashes them.

[Flettner]

Oem Kawasaki KX250 with mods and Polini petals
New V-force is bad,, the petals are getting soft, the resin dissolves.

I tried a boyesen cage with polini petals, no good.
There´s no rubber coating so the petals lands so hard it smashes them.

thats the main reason I switched to the F9 RV engine from the DT360 I was using. Ethanol played havoc with the reeds on the DT.
But now with TPI I'm not sure what might happen?

[husaberg]

thats the main reason I switched to the F9 RV engine from the DT360 I was using. Ethanol played havoc with the reeds on the DT.
But now with TPI I'm not sure what might happen?

Pretty sure i have a 6 petal origional SS IT175 reed valve here Neil.
I can't say if the rubber coating will last though.
Pretty sure it will be the same bolt pattern.

[Grumph]

Pretty sure i have a 6 petal origional SS IT175 reed valve here Neil.
I can't say if the rubber coating will last though.
Pretty sure it will be the same bolt pattern.

YZ reed manifolds held up in 250 kart engines running Methanol/Toluene/Benzole blends. Aftermarket reeds didn't - so got changed frequently.
I believe the "rubber" is the same on all the yamaha reed blocks I've seen.