Any Theories - Carbs vs EFI

WMU_BRONCO

WMU_BRONCO

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Anyone have any theories as to why carbs get better fuel economy than EFI. If you go to fuelly.com and compare FZ1 Gen 1 to Gen II you will see that Gen 1 gets better fuel economy even though the Gen I is heavier. Also the Bandit 600 carbureted bike got better fuel economy than the following year EFI Bandit 600 even though the rest of the bike was virtually unchanged. It would be interesting to take a look at all bikes in the before/after they changed to EFI to see if the same hold true.
 
The gen 2 has larger bore intakes and a shorter stroke. This give you less torque at partial throttle, where most of the driving accrues. EPA interference in tuning is probably to blame for much of the difference. I had a fuel injected 87 BMW K75S which got excellent mileage. May be gen 1 riders are older and easier on the throttle. :rofl:
 
EPA interference is right on the mark...

With fuel injected bikes, that also brings in Catalytic Converters and such nonsense... with converters in place, the bike will get worse gas mileage. Compare a stock Gen 2 to a Gen 2 with cats removed, airbox opened up, flies tied / removed / replaced and a proper Power Commander with tune.. the modded bike will do much better in both terms of power and in terms of MPG.

A lot of the emissions stuff really brings about worse performance and fuel mileage. Here at work, we have a fleet of trucks. The smallest ones we use are Chevy 3500 diesels. We also have quite a few Ford F450's and F550's. On all of these trucks we were getting horrible fuel mileage. I talked my boss into doing some work on his truck... a more free flowing exhaust/intake, as well as deleting the whole EGR system. Not only does his truck get better fuel mileage and better power, there are also fewer problems. With the EGR system in place he had 2 turbos replaced under warranty because the EGR dumped all sorts of crap into the turbo and basically gummed it up with carbon. Now, with the EGR removed, there are no more carbon problems, the exhaust temperature is lower and he's gone from 16MPG to 23MPG... all in all it was about $1500 worth of work and parts, but the fuel savings when stretched across 18 trucks is staggering.
 
WMU_BRONCO said:
Anyone have any theories as to why carbs get better fuel economy than EFI. If you go to fuelly.com and compare FZ1 Gen 1 to Gen II you will see that Gen 1 gets better fuel economy even though the Gen I is heavier. Also the Bandit 600 carbureted bike got better fuel economy than the following year EFI Bandit 600 even though the rest of the bike was virtually unchanged. It would be interesting to take a look at all bikes in the before/after they changed to EFI to see if the same hold true.
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There are tons of factors that will determine fuel economy and it's not exclusive to carbs vs EFI

The Gen 2 FZ1 motor in itself is different in design, isn't it? It makes more power and has a much sportier nature than the Gen 1 based on my impressions. I thought they retained more of the R1's features for the Gen 2, including the gear ratios and such.

When the Bandit switched over to fuel injection, the motor was completely new. More power, more torque, water cooling, etc. It's hard to compare. The old Bandit was a wheezy old bugger that would move you along without any interesting characteristics. They tried to make the Bandit sportier and more powerful when they re-vamped it in 2007

va_rider is right with the emissions requirements as well, that plays a huge factor--it shouldn't be a detriment, though.

Auto engines today are making more power than ever before while still producing next to no emissions and offering good fuel economy; bike manufacturers are just not up to snuff yet. If you think about it, fuel injection has only just really become mainstream on bikes in the last few years--there's a lot of catching up to do.
 
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My guess is that you can get away with bores and strokes, huge cams, 5 valve heads and all sorts of other things with EFI. That stuff is real tough on gas mileage.

Beast
 
I think if you compare two identical engines with the exception of one being carburated and the other FI, the FI one will offer better mileage, emissions and drivability...
 
bigbaddave43 said:
The gen 2 has larger bore intakes and a shorter stroke. This give you less torque at partial throttle, where most of the driving accrues. EPA interference in tuning is probably to blame for much of the difference. I had a fuel injected 87 BMW K75S which got excellent mileage. May be gen 1 riders are older and easier on the throttle. :rofl:
Click to expand...

You are right. I didn't know the bore and stroke were changed. Thanks for pointing that out. The longer stroke on the Gen1 should result in more torque, and the longer stroke should also result in more burn time during the combustion cycle for better fuel economy.

Gen 1 Bore x Stroke 74.0 mm x 58.0 mm
Gen 2 Bore x Stroke 77.0 mm x 53.6 mm

And you are probably right about us old men being easy on that Gen 1 throttle.
 
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