AFR limits

[Phat Cat]

I installed a Koso X-2 gaude on my 12 M1100t and it is great. I can set the AFR limits on the gauge and a warning light will come on if it is past the limit. I am kinda new to the 4 stroke turbo scene and new to the AFR gauge. Running an Evo super chute kit. Always use 100LL avgas and set on the 310 hp setting. anyone know a baseline of rich and lean limits to look for? Thanks.

 

[Merc63]

I'd say you would want to be targeting 11.9:1. Anything leaner than 12.5:1.

Depending on your fuel system, fueling is going to be jumping around a bit and tripping the alarm constantly.

i wouldn't want it richer that 11.5, but richer is not as bad as lean.

 

[Phat Cat]

Thanks Merc.

 

[samsquatch47]

4 strks can run as lean as 14-16:1 cruising down the trail at a low load situation without any problem. If it's running at 11.9:1 in the midrange you're just wasting fuel. Merc's numbers are right for WOT but idle is good around 13:1 and like I said cruise can be way leaner without hurting it.

 

[Merc63]

Ouch 16:1 crusing, I would stay far away from that. Good way to create way too much heat. Stiochometric for pump gas 14.7:1.


my numbers are wot. Cruise Id say 13.5:1 to 14:1.


part throttle 13:1

who cares about burning a bit more fuel if it's easier on your engine.



Ideally you you want to throw the machine on a dyno and make fueling and timing changes while doing pulls and watching power. Every engine is different.

 

[samsquatch47]

"As lean as 14-16" which I meant may see that is ok and it is. Ask Neil owner of Boost-It. By low load I don't mean cruising across a field. I mean those times when the groomed trail to the alpine is so smooth you can cruise with the boost gauge in vacuum or slightly down hill. As soon as the boost gauge goes into a + it should then add fuel. If the engine is hardly working there is no need for hardly any fuel. These were numbers off my race gas turbo Nytro with boost-it fuel system. Which in a no boost situation does nothing. Thus the sometime 16:1 is from the stock Yamaha ECU. Those japs know what is safe and what isn't. The Dyno has nothing on how your sled actually runs in real world situations. Throw an AFR on your stock gas truck and you would be blown away what the ratios are at low load .