2-stroke fuel maps

spadodi · Post by **spadodi** » Tue Feb 28, 2006 9:00 pm

Im thinking of trying megasquirt on an EFI 2 stoke. Is there anyone having sucess with this? Is it going to be harder than a 4 stroke?
Just looking for some input before I get in too deep.
Thanks

aerowerks · Post by **aerowerks** » Tue Feb 28, 2006 10:26 pm

Well, for one you cannot use O2 sensor to tune, oil in exhaust destroys the sensing element within seconds. You will have to use EGT sensor and tune by exhaust temps. Are you thinking about using premix or separate oiling injection (some two strokes do that). It would be easier to use separate systems. Tuning process itself should not be any different than that for a four stroke, but start on the rich side and lean out. Check the plug frequently for color. Lean running two stroke will melt down very quickly so be really careful.

djandruczyk · Post by **djandruczyk** » Wed Mar 01, 2006 6:05 am

aerowerks wrote:Well, for one you cannot use O2 sensor to tune, oil in exhaust destroys the sensing element within seconds. You will have to use EGT sensor and tune by exhaust temps. Are you thinking about using premix or separate oiling injection (some two strokes do that). It would be easier to use separate systems. Tuning process itself should not be any different than that for a four stroke, but start on the rich side and lean out. Check the plug frequently for color. Lean running two stroke will melt down very quickly so be really careful.

Then how come mazda rotaries can run with an O2 sensor as they have oil injection ??

I can see that an O2 sensor can't be used in something like a lawn mower or probbaly an old dirtbike as they run rather large ratios of oil to fuel, but for a car or a fairly modern 2 stroke I don't see why it wouldn't work even with somewhat shorter life.

What about all those cars that burn oil due to wear are tear? those O2 sensros are still working and reading. (and this I've PERSONALLY verified with an OBDII scantool in realtime)

whittlebeast · Post by **whittlebeast** » Wed Mar 01, 2006 6:33 am

Check my sig below. Goto Ford MAF and huge injectors run with extra 026h4 I have 800cc injectors on a 400 cc cylinders. We can have you hammering by the weekend.

AW

aerowerks · Post by **aerowerks** » Wed Mar 01, 2006 10:19 am

djandruczyk wrote:Then how come mazda rotaries can run with an O2 sensor as they have oil injection ??

Because mazda rotary doesn't run a 40:1 gas-oil ratio, but closer to 2000:1.

Read the Innovate LM1 recomendations, you'll see. I suppose a narowband O2 sensor might last for a while. The question would be on how the reading changes as it deteriorates.

Either way, I believe that tuning two strokes by EGT is more reliable.

jcorsaro · Post by **jcorsaro** » Wed Mar 01, 2006 10:25 am

I have had good luck using a wideband O2 for tuning a two-stroke. I am sure the sensor will not last nearly as long as it would in a 4-stroke application, but certainly long enough for many hours of tuning. They are heated hot enough to burn deposits off. The motor never ran vey well leaner than stoch (14.7:1) according the wideband O2, probably because of the excess hydrocarbons from the oil and un-burnt gas.

aerowerks · Post by **aerowerks** » Wed Mar 01, 2006 10:41 am

That is the other problem with O2 sensors and two strokes. The sensor doesn't measure concentration directly but indirectly by partial pressure so if there are any (oil) vapors in exhaust gas, it will read richer than it should.

whittlebeast · Post by **whittlebeast** » Wed Mar 01, 2006 2:04 pm

The water in the pipe, locating the 02, oil in the exhaust and last but not least the raw fuel in the pope right before it gets jambed back into the cylinder...I did not even try an 02

All my problems went away when I mounted the MAF

AW