[theonewithin]

You do you Yaban.

[TZ350]

I managed a better torque curve with EFI presumably because with EFI I could more accurately set the fueling curve and achieve a closer to optimum Lambda throughout the full rev range.

@TZ350 Possibly, but one thing to watch for is ignition advance differences. You might already know that retarding the ignition around the hp peak, will make the exhaust temperature rise in the pipe, increasing exhaust gas speed in the pipe, which the engine sees as a shorter pipe because of the earlier resonance coming back, and so the hp curve hangs up for longer. Mike

Hi Mike, thanks for the thoughts. The back to back test was done without changing the ignition settings. The bike runs an Ignitec digital DC-CDI programmable ignition. Basically the test was done by just turning the fuel on to the carb or turning the power on for the EFI CPU. Both fueling curves had previously been tuned best as I could.

But you are right I could bend the curve with the ignition, a trick I often use to extend the over rev in the manner you describe. Anyway I have spent quite a bit of time trying to get the best out of both carbs and fuel injection and one thing for sure is that fuel injection is way easier to get wide open throttle fueling right.

Also watch that long "snorkel" on the end of the carburetor, as I found they have a way of restricting the airflow.

When I looked at TPS vis AirFlow through the throttle I was sucking air through the motor with a big vacuum cleaner. Probably not the most scientifically competent result but I was looking to get some idea of the relation ship to help me understand EFI maps.

[panpan]

Probably not the most scientifically competent result

No complaints, you have to start somewhere, and I've used vacuum cleaner motors before.
The best I saw out of a tuned TZ250 twin was 82hp, whereas a SGM 250 twin Superkart lump had 105hp at the wheels. That revved to 14000, and peaked around 12,500, on carbs though
I do think EFI has merit too, as engines are not linear in their demands. Some carbs set ups are very good, but in karting it was always a worry when racing that the fuelling was OK, and any slight mis-fuelling issues equalled detonation, which is no friend to a two stroke either.
Mike
PS Ignitech units are excellent, I use Eastern European stuff a lot, as they are so robust.

[PSIG]

... I do think EFI has merit too, as engines are not linear in their demands.

And that is my interest in this thread. Like you, I have tuned more carbs and mechanical FI than I could ever count; and one difference I have learned is that carbs can obviously be tuned to make awesome power, but of the multiple benefits to EFI is the ability for the system to respond to dynamic changes. While carbs can also produce equivalent power at any point on the dyno — and have for over 100 years — the tune is optimum on that day only, under those conditions and parameters, with that fuel load. Dynamometer comparisons will be effectively equal between any systems at static load points, but that changes once it's out in the wild where conditions also change, and dynamics come into play.

There is no need to get into the benefits of configuration options, ease of tuning changes, or altering event timing and responses ; as those and other advantages are obvious. This is not to say that EFI or specific systems are superior in all regards, and I will follow this thread with interest, as I expect each reader (including myself) to gain different perspective and value from the information. Keep going!

David

[Yaban]

You do you Yaban.

i do what ?

[Yaban]

PANPAN you look intelligent and you know what you doing i appreciate your comments.
Psig
You mix too much speeduino and technology...
Speeduino is the name of a board developed by noisymime that do an action.... I salute his work but it doesn't change the problem of a 2t fuel injected bike or anything else.....

Im just happy finally you admit that a carburetor do a great job too....

Just a last question about this build anyone reply...

Where you gonna spray the oil and how for lubricate all internal ?

[TZ350]

... benefits to EFI is the ability for the system to respond to dynamic changes. While carbs can also produce equivalent power at any point on the dyno — and have for over 100 years — the tune is optimum on that day only, under those conditions and parameters, with that fuel load.

Totally agree. 2T's are very finicky and carburetor tunes are only as good as the day (or hour) they are setup, any other day those settings can be totally inappropriate. It is why you see 2T people consulting their weather stations, RAD gauges, chicken entrails and crying quietly in the corner while endlessly fiddling with their carbs trying to find out why it is running so badly today when it was singing yesterday. Relating a bit of my own experience here I guess.

With a carb, the hot deal is to find your best tuning setup on the dyno, record the exhaust gas temp (usually around 650 deg C) and when you are at the track re jet to achieve the same exhaust gas temperature. Sounds fairly easy.....

With EFI and its ability to automatically adjust to changed conditions I expect that the engine will stay in tune all the time, whatever the conditions. Maybe the power will go up or down depending on whats happening but the engine will stay crisp whatever the day brings. EFI can be a whole lot more accurate, and remain completely accurate throughout the whole range. Whereas on the day with a carburetor you could be fiddling with all manner of jets, needles and slides to get the thing crisp enough to be competitive and then have to do it all again tomorrow. To bad if practice and setting up and qualifying is Saturday and it is only racing on Sunday with a big low pressure front rolling in.

[TZ350]

Just a last question about this build ... where you gonna spray the oil and how for lubricate all internal ?

Fuel/Oil is 20:1 pre mix and with the injectors in the "B" ports I was a little concerned at first about lubrication but the oil still seems to find its way around the engine Ok. Between track time and dyno time the EFI engine has done quite a few hours.

I was concerned about other things too, like less power because of reduced charge density due to the loss of cooling effect from the latent heat of evaporation of the fuel in the inlet tract and crankcase but that does not seem to be a real problem either.

[TZ350]

.
Really Happy. I am starting to understand how it all works and have got all the gauges working. Everything is dummied up and my calibrations are crap but for the moment it is just about understanding how to wire things and set up Tuning Studio.

With my previous EFI experimentation the system completely switched between the small injector to the big one so it was all small or all big and that seemed to work Ok. I will be interested to see how the Speeduino approach of running the small injector all the time and adding the big injector as required works out in a two stroke.

I have been able to simulate a multi tooth wheel and get sensible RPM readings. And a lot of things look familiar, like the pulse width and duty cycle is the same at various RPM that I recognize from my previous work with that other EFI system. So things look very promising.

The only thing I have not simulated yet is the fuel pump. With that other EFI system at "Key On" the fuel pump would run for a short moment to prime the system then turn off and wait until the motor is cranking before turning on again. I will wire in another LED to check to see how Speeduino handles it.

Very little wiring required out to the injectors Etc so putting it all on the bike should be easy.

The engine needs a re build, may take a couple of weeks to get sorted and back into the bike, then I am looking forward to having a go with the Speeduino.

I am not sure how I am going to handle the VE mapping but I am ... ... Very excited to be making progress.
.

[theonewithin]

Speedy handles fuel pump exactly the same as you have said.

However v0.4.4 doesn't have the hardware by default to run a pump via relay unless you have added a ULN to the proto area.