Bike FI - why did it take so long?

[D O G]

Was pondering this on the way home. Why did it take so long for FI to become pretty much standard on bikes? It was pretty much universal in cars by the early 90's, but it took another 10 to make the same transition to bikes - why?

Now, I don't want the 'because it was easier to get carbs working well across the rev range' answer, because I know that. What I want to know is why that is the case.

What was the technical problems encountered with FI which held it up for so long?

Thanks!

[Faldo]

I don't think manufacturer's wanted to use FI, but emmision laws might of forced them. Perhaps?
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[Kickstart]

Hi

No real technical problems. BMW were selling fuel injected bikes in the early 1980s (as were Kawasaki), even ignoring the turbo bikes, and Bimota and Ducati were selling pretty high performance injected bikes by the late 1980s (and even Moto Guzzi were selling injected versions of their bikes).

Trouble is cost. Fuel injection costs far more. From memory the kind of difference quoted was £40 for a bank of 4 carbs compared to £150 for an equivalent fuel injection system (prices in bulk to a factory). Even now if I wanted to buy new parts for a bike at retail prices it would cost a fortune to do it with fuel injection even compared to some top of the range flat slides (let alone some of the budget Mikuni RS flat slides).

When carbs work pretty well on a bike (small cylinder, high gas speed, individual carb per cylinder) there was little point in adding a fairly large amount to the final cost of a vehicle.

I suspect that they were largely forced into it to get round emissions rules.

All the best

Keith
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Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

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[Blau Zedong]

I think fuel injection is also much heavier than carbs which is a big no - no untill emissions legislation forces you that way.
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[D O G]

So in actual fact it is nothing to do with carbs being easier to get working well then FI, just a matter of cost and weight. Makes more sense to me.

[Kickstart]

Hi

Takes a pretty good fuel injection system to get better results than a decent set of carbs.

Used to be a pretty standard trick when tuning cars to dump the fuel injection and go to a pair of decent carbs. The Alfa 33s lost power when they went from having twin choke down draft webers / Dellortos to Bosch fuel injection (and that was a multi point fuel injection system, not a cheapy single point setup). From 118hp to 110hp on the 1.7 for example.

All the best

Keith
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Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[D O G]

So why is that then? Is it because carbs are 'self regulating' - i.e. fuelling reactive to the actual airflow, rather relying on a compromised map (can only have so many data points), which may have poor input data (due to poor sensors).

Are the FI jets not as good as carb jets either?

[Kickstart]

Hi

Old off hand comment was that fuel injection gave engines what they needed, carbs gave them what they wanted.

Reality is pobably more down to how bad basic fuel injection setups are. Single throttle bodies miles from the valves, tortuous intakes, restrictive air flow meters (or just using slow reacting MAP sensor based systems), no tuned length intakes. Add to that the difficulty in doing any kind of remapping for fuel injection (add ons like Power Commanders are pretty recent), except by burning a new chip (and even that is not always possible). They were pretty much designed to be cheap and run cleanly for emissions just strangely marketted as a performance thing.

Even worse are the psuedo efi Bosch K jetronic systems (basically use a balanced wedge in the air flow to just adjust the flow to some continuous injectors), which were used on loads of 80s cars (eg, XR3i, Golf GTI, etc).

All the best

Keith
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Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[the grim reaper]

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