View Full Version : Why doesn't FI bikes need to warm up?

10-28-2008, 11:35 AM
I'm sure my next bike will be FI because I hate having to let my bikes sit and warm up on the slightest of colder days.* But why is it that you can start a FI bike and go and a carbed bike requires a warm up period?

10-28-2008, 05:42 PM
Same reason(s) a FI car can just get rollin and a carb'd car needs a little warm up time.

Gas Man
10-29-2008, 03:34 AM
Yeah its the carb not the motor that needs to be warmed by this mentality.* But it gets confused because it takes the motor being warm to warm the carb.*

Either way a start n go is not nearly as good as a nice warm up.* I don't leave on my bike till I can feel warmth on the top of the rocker boxes.

10-29-2008, 09:04 AM
Why dot he carbs need to warm first though?*

When I took my bikes to the new house, like 2 miles TOPS, I let them warm up a bit and then drove them to the new place.* They STILL where not warm enough to get smooth throttle response.* It was like 50 out that day.

10-29-2008, 09:07 AM
I think it has to do with the combustion temperature and flow of gas.

But even an FI should be warmed up.* i always warmed up my F4i before taking off. just my 2 cents.

10-29-2008, 11:17 AM
efi is computer controlled. the computer keeps the vehicle from stalling its tied into the *timing and efi

11-12-2008, 04:18 PM
Im a car tuner myself, so moving from a turbo FI car to a carbed bike has required me to move my thoughts on fuel delivery.* Here is a cool article about FI vs Carb* http://hemrickperformance.com/Carb.aspx * and some more- http://auto.howstuffworks.com/fuel-injection1.htm and some more

11-12-2008, 04:36 PM
Thanks boomer!

11-12-2008, 11:20 PM
Thanks boomer!

Did it actually help at all?* I showed that to my cousin and he got it after that, so i figure it must be a good explanation, to me its not the greatest, but it shows the problem that carbs have and how efi is so good, and most bikes are switching to it.

01-01-2009, 08:47 AM
a carbed bike that is jetted well will start and run as easily as a fuel injected bike . problem is that stock carbed bikes arent jetted for max power or even smothest operation . they are jetted for emissions standards . changing the jetting based on emissions to jetting centered on smooth ,clean operation will convert any cold blooded bike .M

01-02-2009, 05:11 PM
with no warm up whatsoever. Not good.

01-02-2009, 09:14 PM
True, and when a bike is still cold, fuel atomization is the main reason why a bike or car runs rough. Fuel takes a little warmth to better break up into smaller droplets for a better and more complete burn in the combustion chamber. Take for example an old car with a 4 barrel carb and aluminum intake. On a cold day, fuel can "puddle" on the intake floor during startup and idle, especially when the plenum and intake runners are of a large diameter or volume, which at idle means low velocity. Add to all this that with such cold air, you need more fuel to keep the engine running because of the denseness of the air, and if the choke isn't set just right, you can have too lean a mixture, and with too much pumping of the throttle, too MUCH fuel, you get stumbling and the like. With EFI, fuel is pressurized and sprayed in a much more efficient manner, being forced into smaller droplets, and the computer controls just how much fuel is injected at any given fraction of a second, depending on what readings it gets from the engine . I'm a huge fan of carbs in cars and bikes, and you can really dial em in with some effort, but for overall ease of use its hard to beat fuel injection. By the way, it's not that the motor doesn't still need to warm up, it just doesn't ACT like it does. It may be running smooth, but everything is still below it's optimum operating temperature. You should still take it easy on any motor until it has warmed up a little. I see guys take off on their bikes at like 9 grand after hopping on their bikes with no warm up whatsoever. Not good.

But it's cool to take off just take it easy right?*

Thanks guys!

01-03-2009, 09:36 AM
I'm assuming you're talking during normal riding season, so yea. I fire it up and let it idle for maybe a minute while I gear up, then I'm gone. Even when it's say 40 out, I still only let it idle for maybe 2 minutes, then I just take it real easy till the temp gage has moved a bit. Honestly, I'm not hard on my bike very often, as far as riding higher up in the revs goes.*