En om nog even verder te gaan, stukje van Vortex:

Throttle bodies (and carbs) are basically sized to feed one cylinder. This makes sense, because only one cylinder is really filling at a time. So, in theory, the size of your individual throttle body plates should be the same as the plates in your single TB. For whatever reason (keeping the plenum filled? Fighting reversion effects? Making up for other poorly flowing parts of the system? I honestly don't know) shared throttle bodies wind up having to be somewhat larger. Look at some engines (aircooled VW are a good example) that use both single and multiple carb setups. You'll see that you don't wind up reducing the size of the throttles even though the air requirements of the engine haven't changed and you've doubled or quadrupled the number of throttles.

AFAIK, ITBs can have advantages single TB setups because A) you can tune each cylinder like an individual engine, B) because it's easier to adjust runner length, and C) you potientially have less restriction in the flow path.

On a related note, runner length tuning is not as simple as it might seem from reading vortex. Shorter does not equal better. Longer does not equal better. When the intake valve closes, the air that was rocking down the intake port and runners slams into it and heads the other way. When it hits the other end of the runner, some of it turns back. And it keeps bouncing like that until the intake valve opens, or all the inertia is used up. If you open the intake valve when the pulse is just getting to the valve, you squeeze in more air. The timing depends on how long the runner is, and how much time there is between intake valve closing and opening (RPM.) The shorter the runner, the higher the RPM must be to "catch" the pulse. But here's the trick: In order to catch the pulse on it's very first bounce, your runners have to be something over 40 inches long at 7000 RPM. It just won't fit in most cars. So if you shorten the runner, you can maybe catch the second pulse, which is weaker, but still good. That happens at about 19 inches. Still too long for most cars, and longer than most stock runners. So some guys make their runners 14 inches or less, and catch the 3rd pulse, which is even weaker, but better than nothing. If you make it shorter than that, the RPM where it "works" is edging towards 9000. Use this calculator to get a rough idea of what happens: http://bgsoflex.com/intakeln.html

I'm shooting for 19-21" runners from valve to end of air horn. This will give me a boost between about 6000 and 7500 rpm, and it will be a stronger pulse than those shorty intakes. To do it tho, I have to either run a Fox radiator over on the drivers side of the engine bay, make a "short" radiator so my runners can pass over the top, or snake the runners over to the side of the radiator. The Fox radiator is a mounting nightmare, and might not get enough airflow to make it a viable street option. The custom radiator will cost $850 from Ron Davis! So I'm trying option #3. The TBs will be mounted on a stubby manifold made from a stock 16v mani, then equal length pipes will be bent so they can pick up air from the passenger side of the radiator. I'll stick small airhorns on the ends of the pipes. It's not as good as a nice constant taper air horn, or straight runners, but it gets me clean, cool air, AND the runner length I want. *shrug* Remains to be seen how well it will work. If it sucks, I'll just make it into a super short setup like everyone else.


Als je op die link klikt kan je dus berekenen hoe je optimaal gebruik kan maken van die 'pulse' en hoe lang je inlaat dan moet zijn.