Oyvind Ryeng
New member
In the 4-stroke-world the wideband oxygen sensor have become an irreplaceble tool for measuring the air-to-fuel ratio (AFR). Now, I come from the world of turbocharging and tuning/mapping Honda DOHC VTEC machines, and I am used to seeing an AFR of exactly 11.5:1 on a full throttle high RPM run combined with perfectly tuned ignition timing to extract the maximum efficiency possible; utilizing all of the injected fuel for neck-breaking acceleration. It's mostly thanks to the perfect tune that one can make 500 WHP out of stock S2000 F20C's, Prelude H22A's and ~350 WHP from the Civic's B16A and Integra's B18C. Without a good and close to perfect tune, these machines simply won't make this kind of power, and certinly not reliably. Many of these cars lasts for years at power levels exceeding twice and maybe even three times their rated stock output, and I give the credit not only to the stout Honda engines, but especially to the tuners that spend hours on tuning their fuel and ignition maps to perfection.
Now, I have read a lot on this and other 2-stroke specific sites, but I have seen nothing reffering to a wideband as a tool for measuring the AFR of the engine. The closest thing i have seen to a tuning-tool are Exhaust Gas Temperature (EGT) sensors, but they do not tell the whole story about what goes on inside the engine; far from it. Reading the plugs after shutting down the engine after a run; that's a good way to tell if everything is in order, but a wideband oxygen sensor will dramatically cut down the time it takes to inpect the plugs after runs trough the rev- and load-range of the engine. So seeing as how I am totally anal about tuning, I just can't bring myself to simply rely on "hear-say", "the general idea" and EGT's when it comes down to tuning the carburators on the 2-strokes we find in our beloved Yamahas.
So is there any way to use a wideband on a 2-stroke, or will the oil vapors in the exhaust clog it or cause an inaccurate reading?
Extra info:
Wideband oxygen sensors are heated and correct for temperature, they will read the right AFR no matter what the temps are. They measure the AFR in a linear fashion, and give out a voltage ranging from 0-5 Volts. "Narrowband" sensors (the kind found in most passanger cars are highly sensitive around stoich (AFR of 14.7:1). At 14.5:1 they can give out 0.1 Volts and at 14.9:1 they can give 0.9 Volts, just to give you and idea of how dangerously inaccurate these are. I suspect one will run an AFR of slightly under 11.5:1 on a 2-stroke. Too lean and it detonates/pre-ignites or seize the engine, too rich and it bogs and smokes.
Now, I have read a lot on this and other 2-stroke specific sites, but I have seen nothing reffering to a wideband as a tool for measuring the AFR of the engine. The closest thing i have seen to a tuning-tool are Exhaust Gas Temperature (EGT) sensors, but they do not tell the whole story about what goes on inside the engine; far from it. Reading the plugs after shutting down the engine after a run; that's a good way to tell if everything is in order, but a wideband oxygen sensor will dramatically cut down the time it takes to inpect the plugs after runs trough the rev- and load-range of the engine. So seeing as how I am totally anal about tuning, I just can't bring myself to simply rely on "hear-say", "the general idea" and EGT's when it comes down to tuning the carburators on the 2-strokes we find in our beloved Yamahas.
So is there any way to use a wideband on a 2-stroke, or will the oil vapors in the exhaust clog it or cause an inaccurate reading?
Extra info:
Wideband oxygen sensors are heated and correct for temperature, they will read the right AFR no matter what the temps are. They measure the AFR in a linear fashion, and give out a voltage ranging from 0-5 Volts. "Narrowband" sensors (the kind found in most passanger cars are highly sensitive around stoich (AFR of 14.7:1). At 14.5:1 they can give out 0.1 Volts and at 14.9:1 they can give 0.9 Volts, just to give you and idea of how dangerously inaccurate these are. I suspect one will run an AFR of slightly under 11.5:1 on a 2-stroke. Too lean and it detonates/pre-ignites or seize the engine, too rich and it bogs and smokes.
Last edited:
Junior
New member
11.5:1 is awfully rich for a 2-stroke, 12.5-13.0:1 is more the range you're looking for on a WFO pass, and you can get way up past 15.0:1 when you're off the throttle and decelerating.
widebands have been used in 2-stroke technology, many people use them on the dyno to measure AFR during the pull, and HIGH level motor's use them for engine management (we're talking bike GP's here)
on any "conventional" oil ratio, you wont get much life out of the sensor (with the sensors I've seen used anyways) the GP bikes count on replacing sensors before each race, and are running fuel
il ratios of 100:1 or more.
widebands have been used in 2-stroke technology, many people use them on the dyno to measure AFR during the pull, and HIGH level motor's use them for engine management (we're talking bike GP's here)
on any "conventional" oil ratio, you wont get much life out of the sensor (with the sensors I've seen used anyways) the GP bikes count on replacing sensors before each race, and are running fuel
il ratios of 100:1 or more.