There are a few variants to Throttle Bodies(TBs), I have them in my G!!!
Basically, taking the astra G as an example, (but is the same for 90% of cars on the road)...Air enters via the airbox, travels along some tubing in to a plenum chamber, usually mottled on the inside so as to disturb airflow...This then enters "THE" throttle body (singular), across a butterfly, mixed with fuel. The butterfly is usually around 30mm in dia. and opens and closes with pressure on the throttle cable!
Throttle bodies, are the same principle, however, instead of having one throttle body with one butterfly, you have 4 throttle bodies and 4 butterflies, meaning the amount of air entering the plenum chamber can be split into 4. Each butterfly also has its own fuel supply! The number of throttle bodies depends on the number of cylinders, ie 4 cylinder car has 4, 6 cylinder car has 6, etc, etc! Some TB systems will have a direct filter on the end of each "trumpet", other systems (like mine) retain the standard air box, and ducting! The butterflies on TBs are usually around 35mm in dia. although 38mm and 40mm are also availble, the larger the dia. the more air entering the engine....
HTH, I thought I would take up less space than this!
So my 1.6 16v has one throtle body? or is that the case on the 8v? sorry to be dumb but my marte said that a throtle body is similar to a single point injection system, i.e an electronic carb, would that be right or wrong?
Your mate knows b*ll*cks!!!
Yes your 1.6 16v has one throttle body, so does the 2.0 gsi turbo, you may of mis read me before when i said I had TBs in my G, thats because I paid for them to get there!!!!!!
Every car has a throttle body of some discription, your friend is getting muddled up with single and multi point injection! You, my friend, have mulitpoint injection i.e. 4 injectors, a 1.2 8v corsa has sinlge point injection, 1 injector! Got it!!
Lotus which throttle bodies did you go for on your G, Dbilas?
Also what engine have you got and what would you say the performance/power gains are?
sort of understand, but If i was to get TB's instead or having just a TB, would I have an increase in power?
Yes definately, should be around 25bhp min increase, theirs a nova around my area thats running them and it beats evos off the line!
The throttle body is a flap valve, with a resistor to tell the ECU how wide open the valve is. Sorry to correct Lotus, but the plenum chamber or surge tank as the japs call it on their cars is the large manifold section after the throttle body.
When people talk about fitting aftermarket throttle bodies they mean 4 or more, depending on the number of cylinders, which supply each cylinder with their own throttle valve and injector. This improves the airflow, allows the tuner to use a tuned length trumpet to optimise the frequency of resonance of the intake charge and enhance the scavenging effect of the exhaust system (lost? buy a book on engine tuning, it is too complicated to explain here )
Your friend is half right about a throttle body acting like a carb, in the simplest sense, but you have metered injection of fuel by the ECU, whereas a carb is just a 'dumb' system, based on airflow and manifold vacuum. The ECU meters fueling based on ambient temperature, cam timing, ignition advance, manifold absolute pressure, knock sensor, lambda sensor signals . . . .
Thanks steve, I noticed my error but couldnt be bothered to alter it!!!!lol
I have dbilas TBs, which are great from an insurance point of view, but admittedly dont offer the best gains! I have had a LOT of engine work done to my car, and the maximum cold run figures i've seen are 192bhp
I have a 2.0 sri, superchip (prob doesnt help!!), fast road cams, stage 1 head, lexmaul exhaust manifold, steinmetz cotton gauze filter, water wetter cooling system! The list goes on.....alchol spray injection....i think thats about it!!! If I ran pure TBs, like from QED, i could expect around 215bhp prob!
Very nice! Wish mine was running the Dbilas TB's which it should be now!
You have a much better engine to modify than me, simply for the fact of the amount of parts available, everyone seems to do parts for the 1.4/6 and 2litre but miss out the 1.8!
Admittedly its not a good engine to mod but would still be good to do up.
Whats the reliability like with the throttle bodies? I thought water injection was just for turbo cars?
Also any performance figures?