I've heard of a few people using bike carbs on their car engine, but what does this actually do? I have to ask now because my tutor at college
wants to know (after we did carbs and injectors last week).
From what I understand you'd be getting a mix of double fuel to air... although I've no idea how that's beneficial to anyone except
BP.
(Btw if this should be somewhere else please move it thanks)
I think most people use bike fuel injection because of cost.
Jenvey bodies can cost a couple of thousand pounds.
You can buy bike throttle bodies/injectors for £100-200 and buy aftermarket controllers for a few hundred more
people use bike carbs as a cost effective alternative to upgrading to twin 45's or the like. there is also a school of thought that they actually perform better, giving smoother running, better idle etc than webers.
Because they are cheaper and flow more than car carburettors. Why would you be getting double air to fuel ratio? They are all balanced and tuned.
Don't understand what you mean by "Mix of double fuel to air"
Most petrol engines run on air to fuel ratios of around 13:1 and all carbs are set up to provide something like that, never 6.5:1.
Well the Llambda (sp?) ratio is 14.7:1, but seeing as cars with fuel injection already do this, and carbs are having their attempt at getting that fuel mixture before it gets as far as the injectors... I'm trying to understand how they actually work because a carb mixes fuel and air, but so do the injectors. If carbs are set up for this is what I'm thinking correct or do the carbs not let fuel in and are just used for the air control?
you either have carbs OR injectors not both.
If you are home brewing your fuel system, it is easier to use carbs because they require no electronics. on the other hand if you can build your own
fuel injection system then you don't need carbs
Bike carbs are modular, as are bike throttle bodies if chosen correctly.
This makes it very simple to have a setup with one choke per cylinder, just like webers / dellortos.
The fact that they are modular means that spacing to suit the car engine is also very simple.
Regarding carbs, they are mostly variable venturi (sort of like an SU, but more like a Stromberg because of the diaphragm).
This makes them more tunable than a fixed venturi carb like a weber where you need access to lots of chokes to get it right.
With the variable venturi, it will pretty much open as much as it needs to and the tuning is all done with the jet and needle.
With the throttle bodies, as said previously, they're cheaper than Jenveys is the only advantage.
quote:
Originally posted by Ninehigh
From what I understand you'd be getting a mix of double fuel to air... although I've no idea how that's beneficial to anyone except BP.
Ah so it's an alternative not an addition?
quote:
Originally posted by Ninehigh
Ah so it's an alternative not an addition?
The other thing that occurs to me is if someone has suggested using a set of bike carbs as throttle bodies. You make up a manifold with injectors and use the carbs without any fuel supply to control the air flow. I am not sure how well that would work with vacuum slide carbs though, I suppose you could fix the slides fully open and just use the butterflies. Would that save much money over just getting some bike throttle bodies?
quote:
Originally posted by Toltec
The other thing that occurs to me is if someone has suggested using a set of bike carbs as throttle bodies. You make up a manifold with injectors and use the carbs without any fuel supply to control the air flow. I am not sure how well that would work with vacuum slide carbs though, I suppose you could fix the slides fully open and just use the butterflies. Would that save much money over just getting some bike throttle bodies?
yep its been done mate of mine with a indy zetec has bike carbs for the throttle bodies just fix the slide in the up postion
quote:
Originally posted by Toltec
The other thing that occurs to me is if someone has suggested using a set of bike carbs as throttle bodies. You make up a manifold with injectors and use the carbs without any fuel supply to control the air flow. I am not sure how well that would work with vacuum slide carbs though, I suppose you could fix the slides fully open and just use the butterflies. Would that save much money over just getting some bike throttle bodies?
choke size is a compromise on fixed choke carbs (weber etc.) small for low down control big for power. bike carbs have variable choke in an attempt to
equal out the air speed over the jets and gives better low down control. yet a large choke size for power.
old stromgberg carbs were called CV carbs constant velocity. SU carbs same principle different approach.
HTH
woolly
Most people fit bike carbs because
1) they're cheap
2) they flow well
3) they're easy to adjust (shim the needles and job's a good'un [usually] )
4) they can be easily re-spaced
The reason they are quite good for converting into TBs is the above and that they don't have a fixed choke in them (unlike say Webers) so you
don't get the same restriction. With EFi after all, you don't need a choke to create the pressure change needed to atomize the fuel.