Bike Carbs/Throttle bodies on an X14XE

[Dod]

I know Nova Bike Carb has his done but whats involved in the choice of Carb? I know Yamaha R1 Carbs are ideal, but why them as opposed to other Bike Carbs?

Also, what about ITBs from a bike? Reason I'm asking is I can lay lay my hands on this stuff rerasonably cheap.

[Southie]

I had bike carbs on the 1.4sr not my c16xe. ;)

[Stuart]

TB's ftw.

ok you need management, but then with the baby xe you still need management for the spark if you went to carbs only.

[Dod]

So in theory it should be staight forward so?

So what do I need to look out for with regard to size and which would suit my engine most?

[therealnovaboy]

a good way in gauging tb size is to go by twin carb choke size. eg 34mm choke on carb = 34mmTB. altho it is hard to find bike tb sizes less than 37mm and it is hard to choke a bike tb. so therefore it is easyer to find tb's suitable for 16v engines.

this is a rule of thumb. a car will still run with the wrong sized tb's but will mean power is produced at a different place and torque is compomised. therefore 40mm tbs can still be suitable for a 14xe but will have low bottom end torque untill enough air speed is produced through the tb. a smaller diameter tb will have beter air speed at lower rpm but come the higher rves will be a restriction. that is why working out where you want the power is as important as working out size.

[Dod]

So what'd suit the X14XE? 34mm TBs or larger? Its a Fast Road car if that helps decide? Also, when you say Choke size, is there a Choke on Baby XEs or should I just go for Car TBs instead of Bike TBs?

[therealnovaboy]

im not sure what size chokes people tend to use on carbed 14xe i would imagine between 36 and 40mm. in my opinion fast road cars are better with loads of torque. hp is over rated unless your sitting flat out/ high reves all day. thats why rally cars tend to have massive carbs because they are not pulling away from junctions/ below 4k often. therefore 37mm wouldnt be too bad as a starting point. tbs are mearly butterfly valves, in a tube. there would not be much differance in performance between jenveys and bike tbs if set up correctly.

[Stuart]

Dod, the chokes reffered to here are not the same as the "add extra fuel" choke for a carb on a cold start.

Basically you get a 40mm carb (eg a Weber) but it wont actually work at 40mm, you need to put an air pressure difference across the throttle plate to get the fuel to flow. So you speed up the airflow with a choke (google venturi effect) to drop the pressure.

eg Dans 1.6 8v engine was on T40's but running with 32 or 34mm chokes to get the driveability vs power about right.

TB's on the other hand have no choke as the injector does the work so there is no need to venturi it.

[Dod]

I think this is all going over my head and I'm getting into something I dont really understand. I'll get a bit more info and do a little more research on it all and try again.

[Stuart]

basically do you already have the car setup for injection? if so then imho go for the TB's. something around 40mm will be fine.

[Dod]

Yeah its up and running MPI at the minute. Bike TBs arent an option are they?

[Stuart]

and why wouldnt they be?

[Dod]

The fact that you cant choke them? My knowledge of them is pretty limited so I'm relaying on you guys for info.

So I need the TBs, Inlet manifold and a Stand Alone Management system, anything else?

[Stuart]

the choking is irrelevant for TB's

[tom reid]

Most bike carbs have a variable choke action that corresponds to throttle opening.
How much do you have to spend?, is the question.

[therealnovaboy]

ime sure some bike tb's have wax auto chokes. cold start can be set up with the ecu its just a matter of squirting some extra fuel in untill its up to temp. its exactley the same as a normal single tb mpi choke on the 14xe. the biggest problem you have for bike tbs is getting suitable injectors. this can be acheived by using a standard fuel rail built into the manifold and blanking off the injector holes.