MicroSquirt.com read only forum (Jan.15,2018)

It's a 2 stroke 440 cc Liquid cooled with 2 carbs single into a single exhaust. It's a premix sled which runs 32:1 fuel to oil. At the moment it's got no tachometer or speedometer, so I've found a gauge which I can have do Tachometer, water temp, and Narrow band air fuel ratio. From what I've read on the microsquirt knowing AF ratio while tuning is extremely helpful.
I plan on installing at the minimum a Tachometer and O2 gauge. Once I've installed the gauges I would then dial in the jetting so that I know what Air-Fuel ratio to aim for once I convert the sled over to EFI.

My question: Will a narrow band O2 gauge do what I need for tuning, or should I get a wide band O2 gauge?

Thanks,

A wideband is always better than a narrowband, as they give better AFR info and are faster acting. A wideband sensor needs a controller, to switch the heaters on, calibrate etc etc, but they do have other output options. Depending on your gauges narrowband input requirements, you might get this to interface with the wideband sensor/controller, and give you readings to interact with.

Obviously, two stroke oil will affect your sensors' sensitivity with time, but reading your post you talk about carbs and jetting, so are you using the Microsquirt for ignition only

EDIT, OK I get it now, you're looking at grabbing the AFR info from your carbed engine, and applying this to your EFI AFR table modelling. I wouldn't bother just look at the AFR targets for a four stroke. Bear in mind too you'll need a richer start to get the engine running from cold (affects WUE etc), and that target AFR will be lower than the four stroke set up, as this is actually a little higher in reality, because the oil "dilutes" the available fuel by the ratio mix. Simplistically, if you were seeing for 14.7 on your gauge you would be running approx. 3-4% weaker.

PS I always took the head off and looked at my engines for detonation/richness etc. One of the nice things about two strokes, was simpler cylinder head removal.

Yes, I was planning on getting AFR values from my current carbs. I will definitely take a look at the 4 stroke AFR table.

Also, do I have to run a battery to run the Microsquirt ecu or can I get around using a battery? This is not a life or death but the sled doesn't have elec start, and I was thinking if I can get around using a battery it would be nice.

I don't know how fast the uS comes up - you might be able to pull start it. I think the biggest problem you'll have is the 'priming' pulse - the pump comes on for 2-3sec, then the injectors give a little tap to clear the air. Since the system tries to do this every time on start-up, several start attempts could leave you with a completely unknown amount of fuel in the intakes.

I think you'll need a small battery.

That's what I was thinking, I start with a battery. Once I've got the sled running properly I will try it without, and see if it works.....I'll still use battery-less components, though.