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1995 Civic Coupe EJ1
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Discussion Starter #1
Doing some simple calculations a built D16Z6 w/ BC stg3

d16z6 - 1593cc x 7500(rpm) = 11,947,500 <-- displacement per minute

CBR954RR - 954cc x 11,250(rpm) = 10,732,500 <-- displacement per minute


Would this not mean i will be needing bigger throttle bodies to handle the displacement of the car engine? The 954 ITBs are clearly built for that amount of displacement, no? just thinking that this would cause problems/reduce potential.

I am no expert and could have something wrong (or not taken into account something)

enlighten me, thanks!
 

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you have to figure for Volumetric Efficiency. only forced induction engines get 100%+ cylinder volume filled. all NA engines will be under 100%, how much under depends on head, piston, cam......
 

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Its not all about flow. The diameter of the throttles could even be too big, even though the engine should theoretically flow more air simply because it will be functioning at a lower RPM.
Im not saying they are going to be too big, but Im certain they are not going to choke. Tuning the runner length will be key though. Youre probably going to end up investing in a few sets of velocity stacks and some dyno time before its right.
 

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you have to figure for Volumetric Efficiency. only forced induction engines get 100%+ cylinder volume filled. all NA engines will be under 100%, how much under depends on head, piston, cam......
You're right that VE is a big factor, but N/A engines can get well over 100% VE. Actually, VE typically references manifold conditions, so a forced induction engine can technically have less than 100% VE.
 

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Brokedick Millionaire
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you have to figure for Volumetric Efficiency. only forced induction engines get 100%+ cylinder volume filled. all NA engines will be under 100%, how much under depends on head, piston, cam......
wrong. You can get over 100% VE in our motors very easily.
 

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That calculation is assuming 100% VE at those specific RPMs. Unless you know the VE, that calculation is useless. From personal experience though, unless you're running a wild combination of parts in the motor, the 954 ITBs will suffice. They are 42mm each.
 

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1995 Civic Coupe EJ1
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Discussion Starter #8
orite guys cheers for info. il be fine with the 954's then :)
 

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Your calcs are off by 50% as it is a 4 stroke engine and only displaces its cylinder volume every 2 turns, not every turn. Having said that, the principle still holds as both figures are double and the relativity remains

I would be very surprised if some D series engines do not make over 100% VE at maximum torque. I know the 1989 Aussie Ford Falcon 6 cylinder made about 115% VE as it came from the factory.

As the D16 needs at 7500 needs to flow more air than the CBR at 11250, the CBR throttle bodies will reduce VE of the D16 at that rpm unless the throttle bodies are bigger than really required for the CBR. I don't have the data required for a proper comparison.
 

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Discussion Starter #10
Orite patprimmer, didnt think about that 1. Thanks for the feedback though! most people seem to think that the CBR's will be fine.

And as most practices prove, they produce great power gains.
 
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