I am going to be fabing up a new intake for my 2.5L I am building. It will have 4 - 38mm yamaha r6 tb's. What would be an optimum length for them not to sacrifice torque? I would mount them right up to the head but I feel I would loose way to much on the bottom end. What are your thoughts?
The motor is going to me boosted. And for those who are gona say you dont need that much air and it is a waste of time, this motor is going to have a 10k redline so I will need the air to get it up there.


best time so far 14.3 @ 101.1mph(no traction)
www.cnnmotorsports.com

Don't put the carriage before the horse. If you are going to make an intake setup like this, I'd suggest changing as few variables at a time in order to save time on debugging. Get a good multi-throttle body design ironed out first. One of the hardest parts of doing a multi-throttle setup will be deaing with irregular vacuum pressure. You will need to find a good place to put a MAP sensor. Make sure you pick a throttle bore that will produce good results, too. If you pick a bore that's too large, the slightest movement in throttle will change manifold pressure by a huge amount - the stock computer will NOT be able to deal with this. This type of sharp enrichment issue can be tricky to deal with even with a standalone.

2016 WRX STi Limited (current)
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1991 GVR4 #1933 (sold)
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do it like the 4g63 magnus intake, put a silicon connector in between the runners so you can just loosen the hose clamp and change the length around till you get the butt-o-meter screamin.

and yes getting a good vacuum source will be the hardest part.

RPW can make a quad throttle body setup for any motor for like 2200 bucks, and that includes a haltec

1998 dodge avenger 4 cyl AT
Mods are:
Not enough

I am going to be running the megasquirt controling fuel and spark. As for the throttle response the Tb's have a vacume feature that will make the tb bore smaller under vacume conditions. This is supposed to give it a smoother feel. As for the vacume signal I am going to link all the vacume lines together and go directly to the MS map sensor. Or I beleve the Tb's run off a map as they are so I can pull the map signal from there. Any Ideas on the runner length?
Also I am eliminating the stock ECU entirely.

best time so far 14.3 @ 101.1mph(no traction)
www.cnnmotorsports.com

No one can tell you what length runner you should run on your unknown setup, or even if it's known for that matter unless you do some fluid analysis, or more easily mess with some silicon couplers like mcgyvr said and either dyno test different lengths, or use the butt meter if it doesn't matter to you that much.

Joel Baldridge, ASE Certified Master Technician, Audi Certified Expert Technician