2 stroke A/F ratios

[Modman]

What are you 2 stroke guys with wideband gauges seeing for A/F ratios when running, mainly in the upper throttle positions (2/3 to full). I am running close to 13.8 and plugs look OK. I know I know.... each sled is different blah blah blah, just wanting to see what others are running still.

I know 4 strokes are also different Shawn......

 

[TROLLCAT]

I'm intrested in using a/f gauges on my dragster do they need dc power or what up , or are they self contained,

 

[Modman]

I'm intrested in using a/f gauges on my dragster do they need dc power or what up , or are they self contained,

They need DC normally but if you are running them in your drag sled then I have run mine off a 9V battery, I think they would probably make it a few passes on a 9V, not sure, I only hooked it up for a couple mins but it did power it no prob. Depends on the gauge you run, if you get a DC one like Autometer, you just use a rectifier to convert the AC sled voltage to DC. I'm running the KOSO one, really like it but the no A/F sensors like lead in race gas so if you are running race fuel just be aware they don't last as long as they do in your car..... Do a search on here for "rectifier" and on another thread I posted up some pics and instructions on how to hook it up, they are very very simple to do. I'd search it for ya but I gotta go bath the kid.

 

[TROLLCAT]

I tried rectifier for the nos that didn't workout so good running 12 volt battery just did want hang more stuff on the battery , a/f and nitrous don't care about reading the nos just when I'm running on my secret mix of gas.

 

[dvst8r]

About 15:1 on cruise, and low to mid 13's on sustained wot.

Oh and I think it could stand to be richer on wot, probably mid to high 12s

 

[fatguy1]

I actually checked mine on the dyno.

I have a Koso as well, on the Dyno at WOT the peak HP jetting was 12.5 on the gauge. A little leaner (not burn down lean) was 13.1 . I was told that due to the pulse of the whole pipe deal with a two stroke that the high numbers a person see's at idle and part throttle are not really accurate...

 

[Modman]

I actually checked mine on the dyno.

I have a Koso as well, on the Dyno at WOT the peak HP jetting was 12.5 on the gauge. A little leaner (not burn down lean) was 13.1 . I was told that due to the pulse of the whole pipe deal with a two stroke that the high numbers a person see's at idle and part throttle are not really accurate...

Thanks guys, yeah I was just looking for comparative purposes to see what other guys were running. Mine's still a little fat, when I whack it she drops to high 12's but once it gets moving for a little while at WOT she creeps to high13's, low 14's. Plug check still shows I am slightly rich at these readings.

 

[shawnmcgr]

What are you 2 stroke guys with wideband gauges seeing for A/F ratios when running, mainly in the upper throttle positions (2/3 to full). I am running close to 13.8 and plugs look OK. I know I know.... each sled is different blah blah blah, just wanting to see what others are running still.

I know 4 strokes are also different Shawn......

Would 2smokes tend to read higher due to the greater amount of port overlap? Intake/exhaust open at the same time means more o2 passing straight through? Also the pipe reflects part of the inlet charge back into the cylinder, doesn't it? So the O2 sensor would need to be installed downstream of this? u/s of this point and it would tend to read higher?

Just trying to make you feel a bit better about that 13.8, you know 13.8 on 4stoke would be boom boom.

Take her to 14.5, just make sure your riding with a Yammi for the return trip!! :d

 

[DRD]

12.3, this is boosted though.

 

[sleliuk1]

13.0 this is no boost no NOS, dyno guy said 13 is where its at for 2 strokes. Plug/piston checks good. Plugs a nice brown, looks good and goes good!

 

[fatguy1]

Would 2smokes tend to read higher due to the greater amount of port overlap? Intake/exhaust open at the same time means more o2 passing straight through? Also the pipe reflects part of the inlet charge back into the cylinder, doesn't it? So the O2 sensor would need to be installed downstream of this? u/s of this point and it would tend to read higher?

Just trying to make you feel a bit better about that 13.8, you know 13.8 on 4stoke would be boom boom.

Take her to 14.5, just make sure your riding with a Yammi for the return trip!! :d

Yes, I would say every engine is slightly different, and it would somewhat depend on the location of your sensor also.

When I talked to some "expert" at Koso, he told me when they dynoed a ski-doo motor in their testing, it ran in the low 13's and never melted down/seized. They viewed that as normal running condition.

I bought my Koso from Bikeman and the dude there told me that my motor would make the most HP when the gauge read 12.5... Guess what, he was right!, we pulled the plugs and looked at them when it was in the 13's just because I was scared to seize/meltdown and it didn't look overly lean at all. So we kept jetting up till it it made the most HP and lone behold the gauge was reading 12.5.

Just my findings, take them for what you want.:d

 

[Modman]

Yes, I would say every engine is slightly different, and it would somewhat depend on the location of your sensor also.

When I talked to some "expert" at Koso, he told me when they dynoed a ski-doo motor in their testing, it ran in the low 13's and never melted down/seized. They viewed that as normal running condition.

I bought my Koso from Bikeman and the dude there told me that my motor would make the most HP when the gauge read 12.5... Guess what, he was right!, we pulled the plugs and looked at them when it was in the 13's just because I was scared to seize/meltdown and it didn't look overly lean at all. So we kept jetting up till it it made the most HP and lone behold the gauge was reading 12.5.

Just my findings, take them for what you want.:d

Fair enough, but yeah, each one is different. at 12.5 mine was falling on it's face and couldn't get out of its own way. dropped two mains and plugs are dark chocolate, EGTs reading 1200 vs 1280 last year at same elevation,a/f is about 13.5 now, could be better still IMO, going to go down 2 more sizes and see what that's like, if needed I will go back up again maybe one size.

 

[DRD]

Keep jetting down 'till it melts then go up two sizes.
I added one more piston to my wall of shame today, but it's out of a '70 399.

 

[fatguy1]

Keep jetting down 'till it melts then go up two sizes.
I added one more piston to my wall of shame today, but it's out of a '70 399.

I'm Tired of doing it that way, that's why I bought the A/F gauge.

 

[slomo]

13.8-15 mid and 12.2-12.5 wot i went with the 12.5 just for the safety 13 on mine starts to get hot runs a little too good and plugs start to really lighten up in color