RPM Fuel Injection System

[ribbert]

I also find it funny that a lot of the moto-journalists who get to test properly set up 70's - 90's superbikes always comment on how much more "rideable" these carbed bikes are, than some of the modern FI and fly-by-wire bikes. They almost always comment on the "linear" response to throttle inputs.

I wasn't going to wander into that but I agree entirely. There's also a nano second of delay with the FI that you would get used to if not for alternating with a carb bike. Same for the electronically boosted brakes.
The harder you ride in the twisties the more pronounced the difference becomes. The modern bike is quicker but the FJ has more feel at the controls.

Noel

[Pat Conlon]

There is a delay on our FJ's between the time you open the throttle plates and the time it takes the slide to raise up.
We are used to it, we don't even notice.

You will only notice this if you ever get a chance to ride a FJ that has flat slide carbs, with fuel squirters.

The RPM FI system is reported to have an immediate effect on acceleration, much like flat slides but faster.
The response of our CV carbs is slow by comparison.
Throttle response on our CV carbs can be measured in 1/10's of a second, on a FI system it's measured in 1/100's of a second.

Exponentially different, not even in the same galaxy.

[Troyskie]

It's fast Jim, but not as we know it......

[Millietant]

But, I wonder if that very slight delay works in our favour as everyday street riders, where the immediacy of FI works against our human senses (as opposed to the "enhanced" senses of top notch pro racers etc), making them feel jittery.

I really do notice that my FJ has a smooth feel to the throttle at small openings which makes it feel extremely "controllable". Because most of my miles on the RSV are track miles, I don't use the throttle in the same way - very little pootling around at low revs on track, so I don't really notice it as an issue.

Those are just a few of my thoughts - undoubtedly FI is the way to go for the future, in terms of economy, efficiency and reliability - but for old road bikes with carbs, replacemen doesn't seem like a value proposition unless the carbs are totally shot and a new working FI system can be had for a similar cost.

Now, for race engines - I can see it's a totally different picture.

[Pat Conlon]

Hey Dean, I know what you mean, that was exactly how I felt... "startled" when I rode the FJ with 39mm Keihin FCR's and a lightened crank.  Holy Shit.
I remember thinking that this bike does not care if you are having an off day, you HAVE GOT TO pay attention. 100% attention.
For sure I was not used to it. I'm not sure I liked it.

Is there such a thing as having too crisp of a throttle on a street bike?

I think so, at least for for my ability and skill level.

[fj1289]

Dean - in my experience with the fuel injection it is not "too sensitive" or "over reactive".  It is just nice and crisp.

Best way I can explain it - think of it reacting quicker, but with smaller, more precise fueling adjustments.   

All my tuning was done on the road and using conservative settings.  I can only imagine how nice it will be when the tune is optimized on the dyno and then tweaked for road use.   Ignition settings are the best gains with a well sorted EFI system - usually resulting in better fuel economy in cruise mode and better throttle response everywhere.  Overall horsepower gains depend on how well the original carbs were sorted.   

There is a lot of work that goes into making an EFI conversion run as well and reliably as an OEM type system.   That is Randy's intent for the EFI conversion — unfortunately it will require a lot of focused and dedicated work to get there - and a dyno is truly the proper tool for that endeavor. 

The other part of this is also as an eventual replacement for carbs once the Yamaha supply has dried up.  How many years until that really begins to be a factor?  Whenever it does occur, it will be nice to have a well sorted, easily supported alternative.

[Millietant]

Dean - in my experience with the fuel injection it is not "too sensitive" or "over reactive".  It is just nice and crisp.

Best way I can explain it - think of it reacting quicker, but with smaller, more precise fueling adjustments.  

All my tuning was done on the road and using conservative settings.  I can only imagine how nice it will be when the tune is optimized on the dyno and then tweaked for road use.   Ignition settings are the best gains with a well sorted EFI system - usually resulting in better fuel economy in cruise mode and better throttle response everywhere.  Overall horsepower gains depend on how well the original carbs were sorted.  

There is a lot of work that goes into making an EFI conversion run as well and reliably as an OEM type system.   That is Randy's intent for the EFI conversion — unfortunately it will require a lot of focused and dedicated work to get there - and a dyno is truly the proper tool for that endeavor.  

The other part of this is also as an eventual replacement for carbs once the Yamaha supply has dried up.  How many years until that really begins to be a factor?  Whenever it does occur, it will be nice to have a well sorted, easily supported alternative.

I understand what you mean, but I don't really have any experience of FI bikes other than my RSV - and it wasn't the smoothest at very low speeds/rpm' - which I (as a layman) put down to a combination of mostly it being a big V twin and slightly down to its FI being designed primarily for higher rev running (it's very snatch compared to the FJ).

I do know that I much prefer the FI in our cars now to the old Twin SU carbs my MG's had in the 1970's

[JPaganel]

I also find it funny that a lot of the moto-journalists who get to test properly set up 70's - 90's superbikes always comment on how much more "rideable" these carbed bikes are, than some of the modern FI and fly-by-wire bikes. They almost always comment on the "linear" response to throttle inputs.

I now have three FI bikes of different generations.(Ok, one is my wife's) Analog from 1986, early digital from 1996, and a relatively recent from 2003. There is nothing non-linear about their throttle response.

Seriously, how can the tiny digital increments be less linear than having distinct circuits in the carb?

I could see this being a complaint against some very early FI systems, but on a modern one it just makes no sense.

I wasn't going to wander into that but I agree entirely. There's also a nano second of delay with the FI that you would get used to if not for alternating with a carb bike.

I don't know what kind of FI you have dealt with, but on all of the ones that I know it is exactly backwards from that. There is no delay, especially compared to my FJ and XJ with their CV carbs. Switching from one to the other I have to be more careful on the FI, as it reacts immediately.

There is a delay on our FJ's between the time you open the throttle plates and the time it takes the slide to raise up.
We are used to it, we don't even notice.

You will only notice this if you ever get a chance to ride a FJ that has flat slide carbs, with fuel squirters.

The RPM FI system is reported to have an immediate effect on acceleration, much like flat slides but faster.
The response of our CV carbs is slow by comparison.
Throttle response on our CV carbs can be measured in 1/10's of a second, on a FI system it's measured in 1/100's of a second.

Exponentially different, not even in the same galaxy.

Exactly.


Also, FI systems are tons safer than having carbs which spill gas when tipped over. Pretty sure that if the FJ I wiped out on was FI, it wouldn't have burned down.

[ribbert]

Also, FI systems are tons safer than having carbs which spill gas when tipped over. Pretty sure that if the FJ I wiped out on was FI, it wouldn't have burned down.

Whoa, no one is suggesting carbs are better than FI. The discussion merely talked about the benefit of converting a bike with existing carbs to FI was not significant enough to warrant the expense. It then dfrifted on to some subtle differences in feel.

Maybe by the time I'm Pat's age I'll know what he know's, in the meantime I'll defer to his experience on the subject.

Noel

Noel

[fj johnnie]

 Having read all the replies regarding input reaction of carbs vs FI I am reminded of the difference between two of my dirt bikes. I own a 2009 WR 250 and a 2018 WR 250. At the start, I was startled at the jumpy throttle of the 2018 bike. I was a little concerned to say the least, as I ride trails almost exclusively . It was unnerving and I thought it too responsive. I even purchased the Yamaha power tuner to soften the response. My thought was to ride it for 4-500 kilometers first and once I really understood it, to fiddle with it, making it less jumpy at low speed. What happened was, I went back to the 2009 bike and could not believe how slow the throttle response was, and how much input and effort it took to gain any speed at all. So what really happened is the 2018 bike reprogrammed my wrist and now that I'm used to it, it is much easier to ride than the 2009. when any of us try something new the slight input changes are immediately felt and they don't always feel good. However, over time as we become accustomed to it, the real benefits are realized.

[Pat Conlon]

Maybe by the time I'm Pat's age I'll know what he know's, in the meantime I'll defer to his experience on the subject.

Hey Noel, buddy boyo, I have a feeling we are close to the same age...just a feeling.

I never rode the RPM FI bike so I have no experience with FI on a FJ, Chris and Randy know, I do not.
I have had experience with factory FI on other bikes, most have been great, except for that first year 2014 FZ09 which was not so good.
Embarrassing that Yamaha let that new bike out in the market with a tune like that, although it made Dynojet very very happy with the sales of their Power Commander.

[Country Joe]

Pat,
Another bike that Yamaha released before it was ready for prime time was the early 2nd gen. FZ1. The low speed throttle response was terrible, I noticed it before I managed to get out of the parking lot on a test ride. The 2006 was generally acknowledged as being the worst, but later years were still afflicted with it to a lesser degree.  It spawned the creation of several different "fuel cut eliminators" to bandaid over the problem, eventually they fell out of favor due to better reprogrammed ECUs becoming available. It seems that some manufacturers are better at creating flawless fuel injection programs than others.

[Pat Conlon]

Thanks Joe, yea, there is something to be said about the advantage of offering a FI kit with a fully programmable aftermarket ECU vs. futzing around with a factory hard coded ECU with tuning flaws, and then needing to correct it with band-aid piggybacks.

[ribbert]