Carb vs FI

[Dionysus]

What difference does it make changing from carb to FI on the nc30?

What would I need? Or how would I go about doing this conversion?

I tried searching but I couldn't find a thread that was dedicated to this type of thing. Unless my search was rather retarded.

Any and all comments will be appreciated.

[porndoguk]

the bank ballance!

with no disrespect you either need deep pockets or people in the know have a look through micheal ruhls post in the members bike section and see how much time, work, money and effort has gone into it!

[amorti]

In general, Fi will give a more precise dosing of fuel/air at any given revs, at higher pressure, finer atomized. This means you will get better fueling, and more power.

On the V4, as noted above, it's notoriously difficult to get right, because of the limited space and also the difference in fuelling between front and rear cylinders.

[phil x]

In general, Fi will give a more precise dosing of fuel/air at any given revs, at higher pressure, finer atomized. This means you will get better fueling, and more power.

On the V4, as noted above, it's notoriously difficult to get right, because of the limited space and also the difference in fuelling between front and rear cylinders.

Not strictly correct.
Carbs have some advantages over FI, simplicity & the fact that air is cooler/denser from carbs (ever heard of 'Carb icing' on FI?) because of this carbs can produce more power than a basic FI system
True, electronics on FI can produce more accurate fuelling over a greater range of situations.

Phil

[amorti]

In general, Fi will give a more precise dosing of fuel/air at any given revs, at higher pressure, finer atomized. This means you will get better fueling, and more power.

On the V4, as noted above, it's notoriously difficult to get right, because of the limited space and also the difference in fuelling between front and rear cylinders.

Not strictly correct.
Carbs have some advantages over FI, simplicity & the fact that air is cooler/denser from carbs (ever heard of 'Carb icing' on FI?) because of this carbs can produce more power than a basic FI system
True, electronics on FI can produce more accurate fuelling over a greater range of situations.

Phil

Carbs are indeed more simple, but only when they already work. If you've ever tried to get a tuned bike to work well, you will understand that taking 30 minutes+ each time to change jets or 20+ to change or shim needles is a PITA compared to changing a few numbers in an Fi table.

I don't think you understand what carb icing is. The fuel never really freezes, it just fails to atomise properly because of low temps. By definition you can't get this with Fi because the fuel has no chance to "freeze" - it is sprayed already finely misted from the high pressure injector. That's before I wonder how a CV carb with slide, needle and butterfly can possibly flow less A/F than a throttle body with only a butterfly in the way.

Also, it's near-on impossible to get "real" ram-air working properly on a bike with carbs. As your airbox pressurises, it gets more air in. So do you tune for high revs in second gear where the airbox is at low pressure (runs lean in 6th gear) or tune for high revs in sixth gear, where you sling more and more fuel in to compensate for the high pressure air, leaving lower gears running rich. Not a problem for Fi, which will have an air pressure sensor in the airbox and automatically correct the A/F ratio.

Frankly, if you can afford it, Fi is a far superior system. But therein lies the problem.

[phil x]

I'm not knocking the benefits of well setup FI, yes the infinate tuneability & accuracy of FI is a big plus - if you have the equipment to do it.
I guess I'm looking at it from a home tinkerers point of view as opposed to a motorsport, all the equipment viewpoint.

My reference to carb icing was to highlight the fact that reducing air pressure via the throttle & adding fuel through a venturi significantly reduces air temperature which therefore makes it more dense. You simply don't get anywhere near the same effect with FI, obviously this is offset by greater precision & control with sophistiscated FI systems.

Phil

[kevprojex]

Carbs are indeed more simple, but only when they already work. If you've ever tried to get a tuned bike to work well, you will understand that taking 30 minutes+ each time to change jets or 20+ to change or shim needles is a PITA compared to changing a few numbers in an Fi table.

I don't think you understand what carb icing is. The fuel never really freezes, it just fails to atomise properly because of low temps.

Also, it's near-on impossible to get "real" ram-air working properly on a bike with carbs. As your airbox pressurises, it gets more air in. So do you tune for high revs in second gear where the airbox is at low pressure (runs lean in 6th gear) or tune for high revs in sixth gear, where you sling more and more fuel in to compensate for the high pressure air, leaving lower gears running rich. Not a problem for Fi, which will have an air pressure sensor in the airbox and automatically correct the A/F ratio.

Frankly, if you can afford it, Fi is a far superior system. But therein lies the problem.

I dont think you can better the feel of a well set up bike running on carbs , i have rode and owned lots of different types of bikes both fi and carbs, modern fi bikes are alot better now than early systems, early fi bikes are snatchy and some are utter shite at low rpm a lot worse than any bike fitted with carbs !!. modern 8 injector fi systems are a lot better but it would cost a small fortune to build a system to equal the feel and performance.

Its not impossible to get ram air to work , zx9r, zzr1100, r6(early) zx7r,zx6r etc plus many more race bikes nc30s nc35 etc fitted with ram air, you have to apply air pressure to the float bowl vent tubes to add air pressure above the fuel in the float bowl chamber to equal the pressure in the venturi or the fuel will not flow up the main jet and emulsion tube. speed or gear makes no difference to fueling

Carb icing is when the moisture in the air freezes not the fuel, it would have to drop to around -60 deg for fuel to freeze. Carb icing could happen at very small throttle openings on a very cold damp winter morning and thats about it , i have never had it happen me and have never heard it happening to anyone,every bike i have owned i have thrown the heating system away, once the engine is warmed up heat is tranfered to the carbs anyway.

[amorti]

I dont think you can better the feel of a well set up bike running on carbs , i have rode and owned lots of different types of bikes both fi and carbs, modern fi bikes are alot better now than early systems, early fi bikes are snatchy and some are utter shite at low rpm a lot worse than any bike fitted with carbs !!. modern 8 injector fi systems are a lot better but it would cost a small fortune to build a system to equal the feel and performance.

Its not impossible to get ram air to work , zx9r, zzr1100, r6(early) zx7r,zx6r etc plus many more race bikes nc30s nc35 etc fitted with ram air, you have to apply air pressure to the float bowl vent tubes to add air pressure above the fuel in the float bowl chamber to equal the pressure in the venturi or the fuel will not flow up the main jet and emulsion tube. speed or gear makes no difference to fueling

Carb icing is when the moisture in the air freezes not the fuel, it would have to drop to around -60 deg for fuel to freeze. Carb icing could happen at very small throttle openings on a very cold damp winter morning and thats about it , i have never had it happen me and have never heard it happening to anyone,every bike i have owned i have thrown the heating system away, once the engine is warmed up heat is tranfered to the carbs anyway.

I also like the feel of carbs, but then the only Fi bike I have owned was a 955i (first gen Fi!) Daytona. That was bloody awful under about 3k rpm.

I'd forgotten about that generation of Kwaks, being a Honda man myself. My bad.

I had a 600 Divvy and that carb-iced like an absolute bastard all the way through the two winters I had it. The carbs were very much open to the elements from underneath so the engine didn't warm them much and the electrical heater system either didn't work or was garbage by design. After a motorway stretch (every morning) they would ice as I got to the slip-road. Every time. It was exactly like when you run out of fuel and very dangerous. I discovered that adding about 1/3 litre of IPA (or surgical spirits works too) into a tank of about 20 litres of fuel cured this problem. I read up on why, but it was years ago and I've forgotten.

[Nickd]

I have a fair bit of experience tuning FI on Honda cars, and of working with carbs.

The big difference is the ability to tune every part of the throttle position and rev range. Carbs are reasonablty simple to tune at WOT, but the lack of adjustability in fuel supply makes it difficult to make a carbed engine perform everywhere, relative to a FI map with 250 or 500 rpm increments on the rpm side and 10-15 columns for tps/pressure for a nasp engine, and considerably more for a turbo engine.

[mruehl34]

For a road bike i will not make it. To put a fuelinjection on a small V4, but when you often ride it on a track a fi is better. I don´t want to change jets everytime in the box, i want to ride my bike. The FCR carbs made ​​a lot of work to find the right setup. We live in the 21st century, so i decided to build my bike with a fuelinjection. But you can not put any system on the engine and it runs. It´s a lot of work.

Michael