Air/Fuel Ratio #'s

[turbo800]

I'm just curious what AFR #'s you guys like to see on 4 strokes at different throttle positions and RPM? Idle, Mid-range cruising, WOT, etc


There is another thread on TY where some guys are stating they like to see high 10's at WOT. While this is my first 4 stroke, I am not new to turbos. I been running a turbo 2 stroke since '02. One comment was "we like to run them rich because of the lack of consistency of pump fuel". IMO, this is nothing more than a Band-aid approach!

So, if your running 10's at WOT on a 2 stroke, your pushing raw fuel out the pipe. I realize apples and oranges situation. A safe range for me/us on a 2 stroke has been 12.0-12.5 WOT, a bit leaner on the trail but less load 13.5, and idle very clean and lean around 15.0......lets hear your thoughts!

 

[BigFish BC]

11.5-12.5 wide open 13-14 mid & 14-15 idle a 4stroke wont run less than 11.5 very well at wot,it will start to miss,i have ran them this way for 16 years now without issue.seem to run the best at 12 wide open

 

[1500psi]

Ttt

I'm just curious what AFR #'s you guys like to see on 4 strokes at different throttle positions and RPM? Idle, Mid-range cruising, WOT, etc


There is another thread on TY where some guys are stating they like to see high 10's at WOT. While this is my first 4 stroke, I am not new to turbos. I been running a turbo 2 stroke since '02. One comment was "we like to run them rich because of the lack of consistency of pump fuel". IMO, this is nothing more than a Band-aid approach!

So, if your running 10's at WOT on a 2 stroke, your pushing raw fuel out the pipe. I realize apples and oranges situation. A safe range for me/us on a 2 stroke has been 12.0-12.5 WOT, a bit leaner on the trail but less load 13.5, and idle very clean and lean around 15.0......lets hear your thoughts!

Ever motor runs different, every fuel is different and it's different when going up and up in boost. This answer is best answered on the dyno for sure. My apex on c-23 made its most power at 11.9@18lbs, 11.6@22lbs 11.0@30 and 10.8@38lbs.

 

[turbo800]

11.5-12.5 wide open 13-14 mid & 14-15 idle a 4stroke wont run less than 11.5 very well at wot,it will start to miss,i have ran them this way for 16 years now without issue.seem to run the best at 12 wide open

Looks like our #'s are very close. What boost levels do you run?

Ever motor runs different, every fuel is different and it's different when going up and up in boost. This answer is best answered on the dyno for sure. My apex on c-23 made its most power at 11.9@18lbs, 11.6@22lbs 11.0@30 and 10.8@38lbs.

I'm seeing a trend here. With more boost/oxygen your able to make more power at a richer ratio. That is one scenario I hadn't fully considered...

 

[BigFish BC]

usually around 15-16lbs on my nytro but have run with the same a/fs up to 20lbs boost.

 

[CatRpillar]

Turbo newbie here - if you don't count cars.....

Do you guys use your EGT's to aid in determining the best AFR? What temps do you watch for? Also, how do you determine where your max power is besides using a dyno? Thx. Interesting thread.

 

[TRUEBLUEMAX]

Besides running on a dyno watching engine rpm is the best way to see power increases. The more power the engine makes the more rpm the clutch will allow.


Sent from my iPhone using Tapatalk

 

[turbo800]

Turbo newbie here - if you don't count cars.....

Do you guys use your EGT's to aid in determining the best AFR? What temps do you watch for? Also, how do you determine where your max power is besides using a dyno? Thx. Interesting thread.

Before AFR gauges became popular, EGT's were about the only live tuning option out there. You could still stop and read plugs/wash, but nothing else on the fly. On a two stroke EGT's can be hit and miss. I had a funky mid-range problem that would go from lean to rich in a split second, with carbs it was tough to tell what needed adjusted (needle, nozzle, main, powerjet, etc). I was getting spiking EGT's, so I would keep throwing more fuel at it, to the point it would cough and sputter and choking on fuel. Its interesting, cause on a two stroke you can actually force raw fuel out the cylinders under boost and into the pipe where it will burn. After so much fuel and rich ratio, I went the other way and started leaning it out. I with continued spike EGT's I thought I still had fuel burning in the pipe, it was actually lean and I smoked both pistons. Melted the exhaust side of the piston all the way down to the ring. Amazingly it would still run, til about the time it builds boost then it tries to die. My point, EGT's in my opinion are a good second opinion especially if your O2 sensor dies while your riding!

 

[1500psi]

Before AFR gauges became popular, EGT's were about the only live tuning option out there. You could still stop and read plugs/wash, but nothing else on the fly. On a two stroke EGT's can be hit and miss. I had a funky mid-range problem that would go from lean to rich in a split second, with carbs it was tough to tell what needed adjusted (needle, nozzle, main, powerjet, etc). I was getting spiking EGT's, so I would keep throwing more fuel at it, to the point it would cough and sputter and choking on fuel. Its interesting, cause on a two stroke you can actually force raw fuel out the cylinders under boost and into the pipe where it will burn. After so much fuel and rich ratio, I went the other way and started leaning it out. I with continued spike EGT's I thought I still had fuel burning in the pipe, it was actually lean and I smoked both pistons. Melted the exhaust side of the piston all the way down to the ring. Amazingly it would still run, til about the time it builds boost then it tries to die. My point, EGT's in my opinion are a good second opinion especially if your O2 sensor dies while your riding!

This is exactly correct, EGT's can only be trusted for cylinder temp differences not what the number actually is, if there's a problem either way lean or rich you can't trust it.. And yes it cost a lot of money to learn that lol

 

[1500psi]

Ttt

Not to mention I'm so sick of egt fittings and probe problems and wet Digatrons, avengers