Clive and I have become good friends on this forum although we have never met in person. We chatted today/yesterday about this via PM and he said he is going to go for Toyota 45mm throttles.

I however agree with jmac and early this morning before he made this thread, I suggested the 43mm Toyota throttles as the guys on the VW forum had problems with power on their 2liter 16 valve ABF engines.
One guy didn't get good mid range power on 45's and decided to sell them and go to 43's.
His mid range was better, car was more drivable and he got a liiiittle extra power at top revs.

As mentioned to Clive however, these engines are using max 7000rpm, not a flowed head (although more valves) and something in the region of 276 cams.

Generally speaking the ideal choke size of a weber/dellorto is based on teh size/rpm range of the engine and what size choke is required to develop sufficient signal strength to allow decent fuel metering across said range. In simple terms they have to create a (albeit not massive) restriction of sorts, to manipulate the air velocity through them (and that causes the small pressure drop that gets fuel flowing). So not having ot worry about that, since fuel is delivered in appropriate amounts and somewhat effectively atomised/distributed by the ECU/injectors, you can go a little larger without any real loss.

What you'd ideally want to do is to run the engine with 40 then 45 (of course this costs a lot) throttle bodies on there, and dyno the engine and in particular look at the intake vacuum at peak hp/peak rpms and through from 2/3 to full throttle. Ideally you'd want to find hte size that just avoids any significant (in this case perhaps 0.75" Hg tops 0.25-0.5 more ideally) vac at full throttle. If you ran bigger tbs, it might get full VE with only 3/4 throttle. It wouldn't affect output per se, but you ideally want to just get it at full throttle, that want you can map from 1/2-3/4-full throttle well. If it makes full VE by 3/4 throttle, then even if you lift off the throttle a little, it won't drop power, and you have far less fine control over the output of the engine, which is vital for mid corner and corner exit especially

Having said all that I'd probably suggest trying 42mm if they actually exist, or if not, and it was between 40mm and 45mm throttles, I'd probably just give the edge to the 45mm - but that is speculation from me.

Check out my photos, lots of info in the comments. Throttle bodies are made by an ozzy company (efi hardware) and bolt onto weber/dellorto manifolds.

Its for a street UTE/Bakkie But i would say the engine is race spec. Running a 300 deg duratation. Alot of lift. Made peak power at 7800ish, i also got info that 45mm would work, what setup do you have?

What are you using the car for, is it for the road or track? 45mm throttle bodies on mine seem to work pretty good, despite some people warning me they would be too big.
I think carbs are different because you need a certain amount of air velocity to make them draw the fuel in. With throttle bodies the fuel is being forced in through the injectors so air velocity is not as critical.

Hey guys

Im thinking of swapping my Weber 40mm side's for a set of throttle bodies. My peak power is round about 7800. Is there a formula to work out what size would be optimum ? I know bou the application that works out carb choke sizes acouring to cc's and rpm. Can i use that as a guide or do you work it out diffrently ?

Thanks