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So what are Throttle Bodies ?
karlak - 7/4/11 at 01:49 PM

I am close to deciding on what to do with the engine side of my Car. Think I am changing the Pinto for a Duratec.

So, one thing to consider is how I am going to fuel it. I currently have Twin 40 Dellorto's running off the Pinto Mechanical Pump, so I guess these could be used on the Duratec, but I have read so much on this Forum about Bike Throttle Bodies.


Can someone explain what a bike throttle body is in simple terms and if I were to choose this method over Twin Carbs, what advantage I may see, as well as what I would need to achieve this- fuel pumps etc ?

BenB - 7/4/11 at 02:00 PM

Throttle bodies are designed to be used with fuel injection set-ups.
They are similar to carbs but are non-choked (you don't need the pressure differential created by a choke to cause atomisation- the fuel pump and the injectors do that).
Just to confuse things you can make TBs out of old carbs (though the choke does create an unecessary restriction).

BenTyreman - 7/4/11 at 02:43 PM

quote:
Originally posted by karlak
Can someone explain what a bike throttle body is in simple terms and if I were to choose this method over Twin Carbs, what advantage I may see, as well as what I would need to achieve this- fuel pumps etc ?


Advantages are that you don't have a choke and you have full control of the mixture over the entire operating range. You can have perfect WOT running and perfect lean cruising. The ECU will automatically allow for changes in air temperature and air pressure so they stay in perfect tune. In short, you should see an improvement in power and an improvement in MPG.

Requirements are a fuel pump of the correct pressure and a pressure regulator. I also use a swirl pot to prevent starvation round corners. This requires 2 pumps (one can be a low pressure carb pump, although I use 2 high pressure pumps). You will also need a return line from the pressure regulator back to the fuel tank. The motorbike fuel pump I use has an internal pressure regulator so I have a return line from the swirl pot to the tank.

Keeping some form of fuel injection makes sense on a Duratec as you will need an ECU of some sort to drive the spark plugs, unless you planned to fit a distributor.

nick205 - 7/4/11 at 02:45 PM

In the simplest terms, a throttle body is simply a housing, usually tubular, for a throttle butterfly which is a disc that rotates about a spindle to regulate the volume of air flowing throug the body and into the engine. The housing can also include a mounting/inlet for the injector so that fuel can be injected into the body and drawn into the engine.

Production cars set-ups typically have a single throttle body feeding an inlet chamber or plenum that distributes intake air to each cyliner. In this case the injectors are typically mounted on the inlet manifold just before the cylinder head inlets tracts.

Performance set-ups and many bike engines feature multiple throttle bodies, typically 1 for each cylinder allowing much greater airflow and control over engine fuelling.

Bike throttle bodies are popular due to their relative low cost over after market set-ups from the like of Webber and others.

Benefits over carb set-ups can include; smoother running, more power, greater efficiency, electronic mapping to change characteristics and so on.

Changing from carbs to throttle bodies/injection will require; high pressure fuel pump and fuel filter, swirl pot, return fuel line, some form of engine management system e.g. megasquirt and some rolling road time to set-up.

hughpinder - 7/4/11 at 02:45 PM

It basicaaly gives you fuel injection rather than carbs:

You need (thats different to a carb set up):
A high pressure pump.
A swirl pot (maybe - not necessarily essential, but injectors etc don't like to run out of fuel) - you can feed this with the existing low pressure pump.
Throttle bodies, injectors,loom(manifold to suit, air horns/air box/pelumn/air filter as for carbs).
Fuel pressure requlator (may be on fuel rail on throttle bodies anyway).
Return fuel line for excess fuel.
An ECU to run the injectors

Regards
Hugh

BenB - 7/4/11 at 03:33 PM

Bike TBs are also more popular because they're usually ITBs (individual throttle bodies) for optimum performance whereas quite a few cars have single TBs (ie one big one for all the cylinders).

stevebubs - 7/4/11 at 03:38 PM

Carbs - analogue
Throttlebodies - digital

Which do you prefer...twiddling screws and changing jets (carbs), or twiddling numbers on a laptop (throttlebodies)?

adam86 - 15/6/11 at 03:59 PM

Hi,

I found this thread very informative so thanks! So if you had a completely bog standard zetec engine (say 1.8L) with fuel injection, how much money would you be looking at to convert to bike throttle bodies (inc. rolling road time to set them up)? Am I right in thinking a lot of the above list could be scavenged from the exitsting fuel injection system? And how much of a change in performance would you expect to see?

Adam

whitestu - 15/6/11 at 05:11 PM

Performance and MPG from bike carbs and bike TBs will be pretty similar on a standard engine.

TBs and EFI really come into their own with a high state of tune.


Stu

[Edited on 15/6/11 by whitestu]

cliftyhanger - 15/6/11 at 05:46 PM

quote:
Originally posted by adam86
Hi,

I found this thread very informative so thanks! So if you had a completely bog standard zetec engine (say 1.8L) with fuel injection, how much money would you be looking at to convert to bike throttle bodies (inc. rolling road time to set them up)? Am I right in thinking a lot of the above list could be scavenged from the exitsting fuel injection system? And how much of a change in performance would you expect to see?

Adam


Rough guide, £500-£1500 depending on lots of stuff, but plus rollers time. Could be more, depends what needs making and so on.