technical question fro Rodbolt?

[ausnoelm]

Back in the “old days” with a simple carb 2 stroke, , the timing advance is connected to the throttle, so, if you had a load (like towing) and applied too much throttle, the advanced timing could cause detonation (which is not a good thing) How does a “modern” EFI engine with an ECU take care of this? Does the timing electronically advance anyway, or is there some sort of air flow sensor that takes care of load compared to RPM and keep the whole thing running?

[madharchod]

the ECU adjusts itself with the air flow and gas requirements as the timing dosent change but the required rpm is determined by the prop size and load

[ausnoelm]

the load HAS changed, you are now (say) towing something, the prop is the same, because you didn't change that, timing MUST be adjusted as RPM increases. Not sure you understand what I asked.

[Sequoiha]

The ECM uses the throttle position sensor and the tach signal to determine load, throttle opening wider with little rpm increase = load and the timing changes.

[rodbolt17]

depends on the system.
NO Yamaha EFI setup yet monitors air flow.
that's the difference between mass air flow and speed density setups.
2 stroke Yamaha and HPDI use a TPS,intake air temp and crank position sensor to adjust ign timing and injector on time.
some 2 strokes use an O2 sensor for injector on time trim.

4 stroke EFI use TPS,CPS and a MAP sensor to determine engine lopad and the ECU adjusts timing and injector on time based on thoses inputs.

MAP is manifold absolute pressure, inverse of manifold vacuum.

[ausnoelm]

OK, kind of thought it must be something like that, so in effect, "lugging" an EFI engine is nowhere near as bad as with a simple carbed 2 stroke?

[boscoe99]

OK, kind of thought it must be something like that, so in effect, "lugging" an EFI engine is nowhere near as bad as with a simple carbed 2 stroke?

I would say that lugging a four stroke EFI is worse than lugging a two stroke carbureted, EFI or direct injection motor.

Most all Yams now days are four stroke. Much higher compression ratios than any of their two strokes. High combustion chamber pressures and higher combustion chamber temperatures, due to high compression ratios, coupled with lugging a motor and maybe a bit of bad gasoline, can cause catastrophic damage.

While two strokes may suffer from detonation I don't think it is as problematic in four strokes.

Might this be why Yam wants their four strokes turned to higher WOT RPM values? Here in the US Yam says to prop the motor to run at or near its redline value with the boat loaded.

[rodbolt17]

neither one of you gets it.

carbs rely on manifold pressure VS atmospheric pressure.
EFI is going to squirt a specific amount of fuel regaurdless.

both are stupidly simple but require a bit of knowledge and the ability to shift between the two.