comparing ferraris to falcons....
rofl

you would see more performance from ripping the injection out n bolting a holley n a blower to it.

efi can be a good thing, but in stock cars its not.

You can't compare induction on a sedan and motorcycle!! The torque requirements and gearing differ so much, and like my previous comment regarding V8 Supercars and Ferarri's being compared to the 4L falcon - a Motorbike engine is extremely high revving and hence suited to a short runner length, where a 4L falcon rarely sees beyond 3000rpm in daily driving and peak torque occurs only a touch above that.. compared to motorcycles which are up around 15,000rpm (correct me if im wrong, im not much of a moto expert).

the RB26 engine uses 6 40mm throttle bodies with a bolt on plenum chamber.

the rb 20 and 25 use a single tb

your pretty much right with the bike stuff, most of them have a redline of between about 9000 to 19000, not so right on grouping short runners with multi tb setups. Not sure if you did it intentionally or not.
Sure most of the one you see on hipo 4cyls are short to match the high revs
but there is no reason you can't set the runner length to suit the aplication.
some where in the range 10 to 13inches long would be a good trade off from out right peak power to bottom end grunt. if runs big cams and doesn't do much under 3000rpm already shorten it up to about 7 or 8 inches and let it make some power.

SORRY i thought it was rb25 (stupid me) i didnt read it properly.

I agree, basic rule of thumb is; The distance from the head of the inlet valve to the throttle plate needs to be approx the same length at the throttle blade to the trumpet tip. This is also dependent on the volumetric efficiency of the engine. In theory, the shorter the manifold the more power it makes in the upper rev range, but this is also dependent on valve timing, cylinder volume to throttle size etc. Ultimately the shorter runner length equates to more peak HP but you give up drivability and low end torque. All depends on what your gunna use it for. How good your tuner is will also determine how well it performs in the lower rev range.

My reason for mentioning the bike motors was to show how commonly the multi throttle body setups are in everyday use. The bike setups may also be an source for inspiration and components. Bike manufacturers searching for increased performance have commonly been using multi throttle setups for 30+ years. The peak torque figures with the bike multi throttle setups can easily be reached below 6000RPM. Ok.

The BMW M3 E46 with a N.A. 3.2L I6 (S54B32) develops 252Kw at 7,900RPM with 365Nm of torque at 4,900RPM using the multi throttle body setup so there is room to move with the induction system. Redline is 8000RPM.

The latest 4.0L motor is 313kW with 401Nm at 3,900RPM. Inlet runners look fairly short.

 

 

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just was flicing through and old street commodores mag today and saw there V6 Vengence project they tried multi T/B and initally lost top end power.. but it actually was quicker down the strip!!! ill see if i can find the follow up article for more info. something else to think bout.

that setup was 3 TBs into a common plenum, different setup to what we are talking about. the problem with that setup was they basicly cut the plenum in half to do it. in the end they went to bigger TBs and lost more topend but still went faster then they found the longer the the truppets they fitted the quicker they went until they had trouble luanching because it kept wheel spinning off the line.

- a Motorbike engine is extremely high revving and hence suited to a short runner length, where a 4L falcon rarely sees beyond 3000rpm in daily driving and peak torque occurs only a touch above that.. compared to motorcycles which are up around 15,000rpm (correct me if im wrong, im not much of a moto expert).[/quote]

the new Yamaha yzf-r1 has gotten around the problem of only having a short or long runner in length, with one that varies depending on the rpm giving it more power and torque through the hole rpm range. but I'm with you man if you do it make sure you share please. I think it would be the ultimate n/a mod