Bike FI like car FI?

[Itchy]

The other thread about economic riding.

Anyway my last car before the current one was carb.

Therefore coasting down hills saved petrol. As the revs were lower and there were less sucking from the cylinders on from the carb.

I did this with my newer FI car. I was told no need to do that! modern FI cars stop injecting petrol into the cylinders if they are being spun around by the car say going down a hill as such you can leave the clutch out and it will be more economical.

Does motorbike FI do that?
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[stevo as b4]

I'd be very surprised if bike EFI systems did not do the same TBH. How else are you going to protect the catalyst from overheating if you shut the throttle on a long downhill from the heat from the unwanted fuel being squirted in?

There is normally a set list of parameters for overrun fuel cut off in car's such as:
Engine coolant temp must be over XX degrees
Engine speed must be over XXXX rpm
The throttle must have been closed for XX seconds
And sometimes road speed inputs are used as well. There's no point cutting fuel if the car is going 10mph-20mph-5mph every few seconds in traffic etc.

Bikes will be similar I would guess.

[Nemo]

If fuel was injected into the cylinders while engine breaking, there would be more hydrocarbons (un-burnt fuel) which would upset greenpeace because of pollution.

It is also the higher hydrocarbon produced which would damage the precious metals inside the catalytic converters.
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[Andy9934]

As I understand it, you are correct in that FI uses no fuel if the accelerator is not down (except maintaining idle).

With that said, it is up to you to decide whether any additional saved fuel is worth it once you consider the potential value of the momentum you may be losing due to engine braking.

Personally unless I want to slow the car down I will drop the clutch rather than putting it in fifth.

I am no manner of expert though and will be keen to have my errors pointed out as I'm sure there will be some in this post!
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[TallPaul_S]

Correct, most new cars have a current mpg readout on the dash - with no throttle, slowing down and in gear with the clutch up, they'll read "-----" which means you're using zero fuel.

Idling will use some fuel as the engine has to in order not to stall.

Engine braking not only saves fuel but also saves wear on your brakes. Technically, if you had a long enough hill, you could drive for an infinite distance with the engine running, the same as rolling with the engine off.
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[EazyDuz]

Do any FI bikes have an OBD port like most cars? If so you could hook up a bluetooth adaptor and download the Torque app and see for yourself what mpg you get when rolling down hill.
In my car using the above, in 5th downhill the mpg jumps to 255 (which i believe is just the maximum the software will display for some reason) but it will only do this when warm and has been rolling for a couple of seconds.

However, coasting in neutral down a hill it displays anywhere from 120-240mpg (depending on speed) so coasting in neutral is usually more economical as you roll further.
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[G]

[Kickstart]

Hi

Suspect it is quite variable. Also suspect it is one thing that changes as soon as someone puts on a power commander to try and smooth the throttle out.

My old Alfa 33 would cut the fueling when slowing, above certain rpm. Seemed to be done quite crudely and gave quite a jerky throttle response in normal use (not a problem when thrashed, and it tended to encourage that behaviour anyway).

It will save a bit of fuel, although it is increasing engine braking at the same time. Also possibly saves on emissions a bit.

All the best

Keith
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[Nemo]

Modern bikes have diagnosed diagnostic ports (early FI bikes had a connector block you short out and count the red flashes on the dash).

However where modern bikes have these ports, manufacturers have their own ports, it's only triumph that use OBD2.
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Previously owned: Kawasaki KH125, Suzuki GP125, Suzuki GX 125, Honda CB125 TDC '83, Honda ntv 600, Kawasaki ER5, Kawasaki ZZR600, Aprilia RSV 1000 Mille
Now own: Ducati 848 evo

[MarJay]

They do. There is a thing called 'transport time' which is the time it takes the fuel to get from the injector into the combustion chamber where it is ignited. This time causes the 'hesitation' you feel on many injection systems. Some bike injection systems deliberately fuel on a closed throttle to alleviate this, but the only one I know that does it for certain is on the Buell XB models. Most bikes don't do this IIRC.

So yes, most bikes do indeed stop fuelling on a closed throttle when engine braking.
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[Taught2BCauti...]

If your engine has a 'TPS' (Throttle Position Sensor) hooked-up to the ECU, it will almost certainly cut fuel delivery at the closed position. If the ECU has to rely on the 'MAF' (Mass Air Flow) sensor alone, it probably won't.

I have found this to be a problem when converting cars to run on gas, where the LPG ECU can't make sense of the data from the TPS, and have had to add a micro-switch to detect when the throttle is closed.
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[lihp]

[stevo as b4]

I agree. The PC is supposed to leave all std ECU functions alone, like overrun fuel cut off, cold start maps, safety features like knock sensing, rev-limiting etc. At least I would expect it to, and most car piggy back ECU's are configured this way.

The real change from std is that they intercept the signals that control injector pulse width and add or subtract a percentage probably up to 20% more or less give or take at various throttle positions and load sites.

The newer PC3's etc also have some control over ignition advance retard in a similar way, but the limits are probably say around 10degrees advance or retard, so that it's not possible to program the unit to quickly destroy an engine or render it un startable with ridiculous values.

There will always be physical limits on what can be achieved regarding fueling changes, depending on the fuel pressure supplied and the duty cycle of the injectors, that are they not sized as std to run at about 75-80% of the max duty cycle?

[Kickstart]