Individual throttle bodies in FI

So this is something i want to do in the future, what would be the best way to plumb this lot up.

1 throttle body per cylinder with a plenum attached to that with the pipework from the intercooler onto that.

Would it make any difference where the pipework connects onto the plenum chamber, on the end, centre'd?

effin love this

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Off topic but these are really nice too, FMIC, radiator and oil cooler all built into 1 nice package.

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You like a challenge then!
It will cost a fortune!!
Does look nice though!

I like to give people a challenge.

Whats the benefits and draw backs?

Slightly more power
Slightly better throttle response

Huge cost!
Get NOS. Better value for money!

What do they do when they FI a Type1/2 engine in a beetle or camper?

I assume you set up the throttle bodies as you would normally. I can see how this would improve throttle response. Would you need a greater boost pressure with 4 throttles opening at once?

throttle bodies give improved throttle response, FI gives improved throttle response. Add the two together and it becomes a pain to map.

Next individual throttle bodies where not originally designed for FI so you need to choose carefully which ones you opt for or you will get a boost leak you can never find out of the side of the throttle body butterfly shaft.

A correctly configured single TB with the right intake manifold will always perform the same at the top end as a multi TB setup.

The multi TB setup is ultimatelly restricted by the pipework leading to it so the real benefits are limited when fed by a plenumb chamber.

FI engines like to be fed of a big boost reservoir, the above setup does the exact opposite.

Long and short of it waste of money and space.

To put it into terms we can all relate to think of an air compressor in a workshop you got 2 identical 3hp compressor pumps one fitted to a 50litre cylinder and one to a 250litre cylinder.

You then switch both pumps on until both compressor gauges read 125psi. You connect an impact driver to the compressor with the 50litre cylinder and proceed to undo a wheel of a car, instantly you see the pressure gauge drop and by the time you are undoing the 4th or 5th stud the pump kicks in again to repressurise the cylinder. You carry on undoing the other 3 wheels and notice that at no point does the pump manage to repressurise the cylinder enough to switch of the pump. As the impact driver is using the same volume of air as the pump is creating.

Start the scenario again with all wheels back on the car to the same torque setting. This time the impact driver is connect to the pump with the 250litre cylinder. You start to undo wheel number one and notice a slight twitch in the gauge pressure but it remains constant whilst you are undoing wheel 1, you go onto wheel 2,3 and 4 during wich eventually you see the pressure starting to drop eventually maybe on the 4th wheel the compressor pump kicks in again to recharge, at which point you have finished the job and the cylinder will repressurise quickly back to maximum.

Long and short apply the same physics to an FI engine and you see that all this businees with twin plenumb chambers and running multi TB's all becomes pointless as the best way to feed the engine with maximum air is to have a constant pressure reservoir sitting behind the valves as they open. For this same very reason when you flow intake manifolds you'll find those with the biggest plenumb chambers have the most even flow distribution amongst all the runners.

Excellent! /\

And also, small plenums can affect brake servos too, smaller resevoir. Just aswell motorbikes on TBs and F1 cars don't have brake servos!

Are there any set rules with intake design? Such as plenum volume being a percentage of engine capacity and runner length etc?
I see so much conflicting info.
For example, the stock VR6 intake has long, balanced length runners and a large plenum....all things which are said to improve low end torque. And short runners and smaller plenums are said to improve top end.

Looking at this back to back plot of a normally aspirated VR6 using the stock intake and then the Schimmel short runner, I'm seeing the top end gains you'd expect, but I'm also seeing gains in low rpms! Where the stock intake has an advantage appears to be around 4000rpm, but it's short lived. All this intake stuff confuses the hell out of me!

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You can work out the optimum dimensions for the runer length vs diameter and where you want max power and torque to occur much the same as tuning exhaust runner lengths. These calculations are based on a relationship between cam lift and duration, cylinderheadflow at peak lift, bore and stroke, rpm and induction type.

Once you have that part worked out you come up against the next challenge which involves throttle response which is dictated to how quickly the air is delivered to the tuned runners. If going FI the volume of the plenumb chamber will directly effect how long it takes for the engine to respond to the turbo and how quickly you build boost. Keeping in mind that boost measurement is the air you are not using!
Bigger plenumb takes longer to fill so the engine will be considered laggy but once upto the desired pressure will retain it for a longer period. Whereas a smaller plenumb chamber will feel less laggy but the engine will run out of puff easier on sustained full throttle application where boost starts to drop of.

Cool, thanks for the explanation.

I suspect the law of diminishing returns comes into play with this kind of thing. It's all about reaching a compromise!

nissan pulsar and sierra cosworth both use individual threottlebodys i believe