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Intake Size and Questions

Discussion pertaining to positive pressure E28s.
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Badger
Posts: 623
Joined: Feb 12, 2006 12:00 PM
Location: Whately, MA

Intake Size and Questions

Post by Badger »

I am building an intake . . . well I design it and my neighbor welds it. I read the corky bell book a couple times but im not sure how big i should make the plenum. Im going to cut the piece off which mounts to the head and fuel injector mounts off of the B35 intake then weld runners onto them and then a plenum. Bell states "the plenum volume should be a function of engine displacement - in general, 50 - 70%.

So i found online the 88 535is engine is suppose to be 3440cc, 92mm bore, 82mm stroke. So basically it is 3.429 liters or 209.321inches displacement. So do I build a plenum at about 60% of that volume? I will be using aluminum. thx for any info, im new at this.
altus22
Posts: 621
Joined: Feb 12, 2006 12:00 PM
Location: Norfolk, VA

Post by altus22 »

I read in a V8 engine book that the length and diameter of the intake and exhaust tubes tune the torque curve. I'll have to search to see if I can find that equation again. Do you know where you want your max torque to be?
bimmerboy
Posts: 390
Joined: Oct 18, 2006 7:06 PM
Location: United States

Post by bimmerboy »

larger diameter and short make for an higher power band. I don't know the math required to ball park the right diameter and length though.
Badger
Posts: 623
Joined: Feb 12, 2006 12:00 PM
Location: Whately, MA

Post by Badger »

I think i might go with med to longer runners b/c our engines make torque in low/med rpm's and dont really make power up high and it's goin to be a dd so i don't want to be driving it over 6k.
altus22
Posts: 621
Joined: Feb 12, 2006 12:00 PM
Location: Norfolk, VA

Post by altus22 »

http://www.wallaceracing.com/runnertorquecalc.php

After a quick search this is the best calculator I found. Good luck.
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