Throttle Bodies

[gncgray]

Afternoon

 

I have just found out that you can use bike throttle bodies. Are these different from bike carbs? I am using a new Zetec so carbs are out the question. These are a cheaper option from Jenveys which I have seen for over a grand

 

Could I use any big bike throttle bodies and just buy a Zetec manifold with some silicon hose to join them?

 

Sorry for all the daft questions.

Graham

[ibrooks]

A throttle-body is a throttle body so in theory yes you can use some off a bike. Since throttle-bodies don't have float chambers and resevoirs like carbs do they are also less sensitive to being mounted at the right angle than a carb and therefore more versatile.

 

There are always going to be problems like some daft bracket that serves a vital purpose on the bike but just gets in the way of something in your car and maybe some part of the cable linkages that are on the frame on the bike but you don't have on your car but you can come across the same things with a carb (be it from a bike or a different car).

 

One throttle-body specific problem is injectors. Your fuelling will be managed by a brain of some sort. It needs to be told how much fuel to put into the engine at any given time and it will have been told what the flow rate of the injectors is. A simple bit of maths on it's part let it work out that for the necessary amount of fuel it needs to hold the injector open for X milliseconds. To add more fuel you hold the injector open for longer. Thing is that you only have so long whilst the cylinder is on the intake stroke to get the fuel in after which you are squirting more fuel at the back end of a closed valve. To get around this you fit "bigger" injectors which have a higher flow rate and can shove in more fuel in a shorter time. Now this is all basic throttle-body/fuel injection theory but where it becomes relevant for bike throttle-bodies is that they don't necessarily use a standard fitting of injector. This means you suddenly don't have the same sort of choice when it comes to picking the right size for your engine which is likely to have very different characteristics to the bike.

 

Do some research to find ones that are an easy retro-fit and see if you can find some that use a relatively common type of injector so that you know you will be able to get the thing running right if the standard ones won't do the business.

 

Iain

[Guest boggybogstar]

I used a set of GSXR1100 TBs on mine which gave me 176bhp.

 

Gives exactly the same performance as Jenveys at a fraction of the price

[gncgray]

A throttle-body is a throttle body so in theory yes you can use some off a bike. Since throttle-bodies don't have float chambers and resevoirs like carbs do they are also less sensitive to being mounted at the right angle than a carb and therefore more versatile.

 

There are always going to be problems like some daft bracket that serves a vital purpose on the bike but just gets in the way of something in your car and maybe some part of the cable linkages that are on the frame on the bike but you don't have on your car but you can come across the same things with a carb (be it from a bike or a different car).

 

One throttle-body specific problem is injectors. Your fuelling will be managed by a brain of some sort. It needs to be told how much fuel to put into the engine at any given time and it will have been told what the flow rate of the injectors is. A simple bit of maths on it's part let it work out that for the necessary amount of fuel it needs to hold the injector open for X milliseconds. To add more fuel you hold the injector open for longer. Thing is that you only have so long whilst the cylinder is on the intake stroke to get the fuel in after which you are squirting more fuel at the back end of a closed valve. To get around this you fit "bigger" injectors which have a higher flow rate and can shove in more fuel in a shorter time. Now this is all basic throttle-body/fuel injection theory but where it becomes relevant for bike throttle-bodies is that they don't necessarily use a standard fitting of injector. This means you suddenly don't have the same sort of choice when it comes to picking the right size for your engine which is likely to have very different characteristics to the bike.

 

Do some research to find ones that are an easy retro-fit and see if you can find some that use a relatively common type of injector so that you know you will be able to get the thing running right if the standard ones won't do the business.

 

Iain

 

Thanks for that, I really appreciate you time.

 

Could you use the injectors that come with the lump. As they will be big enough for the fuel?

 

Graham

[ibrooks]

Depends on whether they'll fit in the hole where the injector comes out of on the throttle-bodies you get. As with the original question the answer is "maybe" - depends on all sorts of other things.

 

In your position I'd be speaking to Tony as it sounds like he's done it already. Assuming he's using the same engine he can tell you if the gixer 1100 injectors were OK out of the box or whether he had to source others and whether they are easily available.

 

Iain

[Guest boggybogstar]

Graham

 

PM sent

[Guest loopyonion]

When it comes to injector data, look up a website called witchhunter.com

 

they have all data on every injector by part numbers, impedence and flowrates. Also, some good calculators.

 

Sorry I can't post a link right now, the iPhone is quite limited!