They also need to be balanced and that requires a man air meter for each throat.
Really, it's a huge pain in the ass for a slight gain at peak and a bunch of loss across the board.
For all out race cars that love at high rpm most of the time? Great. Do it. Compared to a 2-bbl downdraft or similarly compromised solution it will make a noticeable difference.
In reply to Stefan (Forum Supporter) :
I can't say about Triumph but my experiance with Weber's on Jaguars should help. Properly set up on an XKE The Weber's are worth 15 extra horsepower. Yes that is all but 15 horsepower on a race car is a really big deal.
Surprisingly much of that is because with 3 SU's the inlet manifold has a S curve whereas the Weber's are a straight shot. Every time you change direction in an intake manifold you lose some horsepower.
The vary thing that makes a Weber such eye candy is what hurts it's power and increases tuning issues.
Look at the elegant simplicity of a SU at wide open throttle. The dash pot will be lifted up and all you will see is a tapered needle over a bridge and the butterfly.
Now look through a wide open Weber. Lots of stuff in the way. Yes it's a little more precise about putting fuel together with air and because of it there is potential for slightly better fuel mileage(?' !!!!?')
Where SU's do it with dash pot oil and springs(?) plus a tapered needle Weber's do it with jets and air correction and emulsion tubes
Not all Weber's result in extra power. On a V12 because the inlet manifold is so short. Weber's lose power compared to SU's. ( Zenth Stromberg 175 ) Group 44 got 450 horsepower from a relatively mild V12 using 4 HD8 SU's when they did a lot more work on the V12 the only way they could get the same power out of six 44IDF's is by lowering the engine 5 inches in the chassis to get a longer inlet manifold. They tried IDA's and again because they are longer they had to put a bubble in the hood that would potentially blind the driver.
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