Speeduino 2T EFI Project

[TZ350]

My wide band O2 sensor is in the end of the reverse cone near the stinger. A position at this end of the pipe seems to give much better results and sensor life.

With two strokes, air fuel ratios and O2 sensors there are two important concepts to keep in mind.

"Transfer Efficiency" how much air/fuel mixture that has been transferred to the cylinder and at certain rpm it can easily be greater than 100%, ie VE > 100.

"Trapping Efficiency" is how much of the transferred air/fuel is trapped and retained in the cylinder to be burnt. Often much less than 100% of the transferred mixture. So a fair amount of air escapes along with wet fuel.

The escaping air reads as lean mixture where as in fact the mixture may be correct or even rich. So when using a O2 sensor one has to always bear in mind what the RPM is. Off the pipe the mixture may be correct but the motor looks real lean, Lam 1.2 or so and at peak torque the same correct mixture would look like Lam 0.85.

With Av Gas on peak torque and WOT Lam 0.85 or air/fuel ratio 12.5:1 is the go.
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[TZ350]

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Staged Injection. Currently the Injectors are simulated by 12Volt LED's.
On my single cylinder two stroke I need to use staged injection and thought I had cracked it by connecting the primary injector to pin 1 (pin 1/2) and the secondary injector to pin 40 (pin 2/2).
Ticked staged injection and both injectors would light up and then I set the cells in the staged injection map to 100% to check the pulse width on the secondary injector running on its own at maximum load but it would not light up at all, neither of them would.
At anything less than 100% both would light but at 100 when only the secondary should be alight, it was not, neither were.
If anyone has any suggestions about how I should setup staged injection properly it would be welcome.
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...On my single cylinder two stroke I need to use staged injection and thought I had cracked it by connecting the primary injector to pin 1 (pin 1/2) and the secondary injector to pin 40 (pin 2/2).

No problem. It sounds like you have both primary and secondary injectors connected to INJ1 channel. Each injector channel has two pins for output, in order to carry more current through the little pins. So looking at the pin-out here, pin IDC1 and pin IDC40 are both connected to injector output 1 (INJ1). Wire your primary injector to both IDC1 and IDC40, and your secondary injector to both IDC2 and IDC39.

Before wiring it up, you can just enable Staged, input your RPM signal, and watch the Speedy LEDs for output in order to verify this with no injectors attached. Set for Automatic and increase the RPM signal and one set should brighten with RPM, then at the point the primaries are maxing-out DC, the secondary channel LEDs should begin to brighten as they engage.

It worked fine for me last time I tried it, and I assume it still does; but if things are not working as you expect I would load the Speedy Base Tune and set for your trigger and Staged in order to verify INJ output LED operation as I described. Once you know how it's supposed to act, then you can reload your 2S tune and look/test for similar operation. David

I will try David's suggestions tonight.

[TZ350]

Thanks David for the heads up. Posted the issues on github and Josh is looking at it. And it appears there is a software issue. I am looking forward to it getting sorted as I am very keen to move on from bench testing to actually running the Speeduino on the bike.

In this Carb vis EFI comparison they mention that the EFI bike had much more fuel in the tank at the end of the day than the carburetor version did:- https://dirtbikemagazine.com/friday-...-vs-injection/

The back story of KTM's 2S fuel injection efforts:- https://dirtbiketest.com/fresh-dirt/...lWDrXgwim9R.97

An Enduro 2S bike was successfully fuel injected here in NZ a few years before KTM:- look for GerbilGronk https://www.google.co.nz/search?rlz=....0.f4F0uIqeHPQ

I am into small 125cc 2S road racers and are looking to push a EFI two stroke past the 10k rpm 10bar BMEP barrier and because it can be modified to suit the needs of a high performance 2S I see the Speeduino as an effective tool for doing that.

Going past the 2S 10k 10bar barrier is like climbing in the death zone on Mt Everest. It is still just climbing only a little technically trickier. Once its been done I guess it will become common place. Can't wait to get the Speeduino and Bike back on the dyno.

[TZ350]

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Basic initial settings I used to get started.

[TZ350]

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All the basic settings to get single cylinder two stroke staged injection working.



Now that I have got my head around Speeduinos two stroke staged injection. The next move is to get a sample and hold crankcase peak pressure measurement system working. Where the crankcase pressure is sampled at a pre determined point in the cycle and the reading is then used as the MAP value for the rest of the cycle. By using the change in the difference between maximum and minimum crankcase pressures as a MAP value should hopefully work well with a VE table.

[pete376403]

Are you using the basic (free) version of TunerStudio or did you get the paid for version? I've got a Speeduino NO2C (small form factor for want of a better description) which wil hopefully end up on the KLR. BMW1200 throttle body, havent got a pump yet and next major will be the "bumps" on the flywheel (currently only 1)

[TZ350]

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Full paid for Tuning Studio version. And you will need a toothed flywheel. I suggest 24 or 36 with 1 missing tooth.

[TZ350]

Hi TZ350, I don't know if you remember the Bimota V Due, a tweak RGV250/Aprilia IIRC which had "direct fuel injection" Well it was overpriced and broke Bimota, but people are revisiting this 1990s bike, and a French company have transformed it using a different ECU, and revised injector location. I saw it and thought of yours (like OEM Bimota) and the newer better system. It apparently makes the bike so much more rideable and has a wider spread of power. Pics for reference...

Thanks Panpan, great pictures of the Bimoto injectors. I have previously tried both positions and for a relativly high performance 2S like the Bimota from my experience those positions will prove inferior to the direct down the B transfer ducts with the primary through the C port. Anyway, for what its worth that has been my experience.
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[TZ350]

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Interestingly and to my surprise I have managed as much hp out of the original GP125 air cooled cylinder as I have recently out of the engine after it was fitted with the NSR cylinder.

You have an ancient GP125 fitted with a Honda NSR125 top end?

Yes, 1980's Suzuki GP100 commuter fitted with a NSR250 cylinder, crank de stroked for 110cc. The spacer in the middle is so the 5 speed gearbox can be replaced with a 6 speed TS125 unit.

An ancient GP with everything plus fuel injection..... 31 RWHP

[TZ350]

Staged injection looks Good. Next move is a crankcase pressure sample and hold pseudo MAP value.

[TZ350]

Hi TZ, I'm glad somebody else is trying the Speeduino 2T route. I am in the process of building my system, using a V4.3 board. It's funny how you're using a NSR250 cylinder as that's the engine I'm hoping to convert. I am trying to follow GerbilGronk's method of using transfer port injection, except I plan on using all four A&B transfers.

I have had no trouble making power with EFI and a single NSR250 cylinder for 125cc. The injectors I used were:-

Primary injector, is one only 38 g/min about 50cc/min in the C (boost) port. Very important to have a small as possible primary injector for widest range of tun-ability. Anything bigger and the injection squirt was not able to be dialed down low enough for correct air/fuel ratio at low load small throttle settings.

I found a single primary 60 g/min about 80cc injector was to big to get correct low load A/F. so for the NSR you are pretty much stuck with a single primary injector.

Secondary injector is two 128 g/min injectors in the B transfer ducts for a total of 256 g/min or about 340cc.

Primary plus secondary is about 390cc total.

With 2S and EFI, for tun-ability you must use the smallest injectors possible.

The four B plus A transfer duct injectors are a great idea but it will not be easy to put a secondary injector in the A transfer duct behind the NSR's Power Valve pulley. This would be more achievable on 250 or 350 single where there is more working space for four injectors.

I found it difficult (actually impossible;e) to weld completely around the injector plug so I just welded the easy to get to part and then used Devcon F Aluminium Putty to seal where I could not reach with weld.

[TZ350]

I too have been thinking about the problem of 2T airflow measurement as realistically the engine has two distinct characteristics i.e. either in the power-band or out of it and as you say the pipe is the key.

Hi DaveyB, its great to have someone else working on this too.

I am still pondering how the air that is sucked into the pipe and then pushed back into the cylinder can be measured.

I would not worry about accounting for the spilled air that is pushed back into the cylinder because it can be accounted for with the injection table at injection time because the spilled air will be consistent. Consistent big, or consistent small . It can be accounted for by the table when the engine is on the pipe and when it sort of is and when its not.

[TZ350]

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Measuring the Pressure in the Exhaust Pipe.

I have tried this and found that the pressure at full power is slightly less than the pressure at idle.

Easy to understand. A negative suction wave passes the measuring point and the wave is reflected back but with reduced strength as a positive pressure wave. The greater the strength of the suction wave the lower the average. But the average between big or small is not that much different.

The only way to make a measurement that can determine a meaningful difference between high or low energy waves is to make the measurement at a set time in the cycle.

For a 2S we need to be able to take an instantaneous reading at a set crank angle.



Data logged with the Ecotrons software I was using at the time. Data recorded during a WOT dyno pull.

White line is TPS, Brown is RPM topping out at 12500 RPM and the Yellow line is a MAP reading. It did not matter where I measured it, in the crankcase or 100mm, 250mm, 500mm down the pipe or at the mid dwell section of the exhaust I always got the same result.

Pressure dropped slightly when I opened the throttle and started making power. In a 2S the pressures measured by a MAP sensor at idle is close to ambient and the average pressure drops slightly when the the throttle is opened. All a bit different to what you would expect from a 4S's MAP reading.

The reason the yellow line is so flat is because it is reading the average pressure. To get a useful 2S MAP reading it would have to be instantaneous and taken at a set crank angle, not over the whole cycle like it usually is in a 4S.

[TZ350]

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Although the pipe is doing the work there is no real reason to make the measurements there. The pipe is like a hammer and all we need to do to know how effective it is being is by measuring how far the nail is driven in with each blow.

Measuring the changes in peak crankcase pressure at a set crank angle is enough to know how well the pipe is working.

[TZ350]

What kind of readings do you get between the throttle plate and the crankcase valve - instant or average?

I have not tried that myself as I expect it does not give useful results and is not at all like a 4S would be.

From the Ecotrons Manual:- ""As you know, 2-stroke engine does not have much meaningful manifold pressure to be used as air charge detection. In this case, you only need to tune the "TPS based Load Mapping" table.""

Unfortunately the "TPS based Load Mapping table." or Alpha-N is not enough either when venturing into the 2S death zone.