auto math

broken_joke

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Nov 24, 2004

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carriere, ms

Jun 12, 2005

#1

• Jun 12, 2005

• #1

are these formulas good to go by in figuring out which parts to get? or are they to conservative?

cfm= hp x 1.6
for throttle bodys

Injector lbs./hr. = horsepower x BFSC/number of cylinders
for injector sizing

the bfsc part ot the equation has been different at several sites. some sites use a bfsc of.45 or .50 n/a and .55 or .60 values forced induction. which values should be used for n/a applications?

 

B

bimmertech

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May 3, 2005

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merriam, ks

Jun 12, 2005

#2

• Jun 12, 2005

• #2

.50 bsfc for n/a. the injector size is merely ballpark, there is another equation for fuel pressure and how that "changes" injector size. this should be used to ballpark your pressure, but track tuning should be used to optimize settings

 

broken_joke

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Nov 24, 2004

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carriere, ms

Jun 12, 2005

#3

• Jun 12, 2005

• #3

what do you think about the formula for figuring cfm needed by the motor? i found that formula last night and thought it would be good to get some feedback on it.

 

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bimmertech

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May 3, 2005

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merriam, ks

Jun 12, 2005

#4

• Jun 12, 2005

• #4

that cfm equation is for carb size i believe, which is a whole lot diff than t/b air flow. just ask your cam/engine builder for a reccomendation on t/b

 

broken_joke

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Nov 24, 2004

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carriere, ms

Jun 12, 2005

#5

• Jun 12, 2005

• #5

alright, thanks

 

Joes95GT

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Jan 23, 2003

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Delaware

Jun 12, 2005

#6

• Jun 12, 2005

• #6

All of those formulas, IMO, are bogus.

I've screwed around with a few dyno tuned cars, that had their horsepower and torque numbers "maximized" on a dyno. With this, the "best" A/F ratio is sustained, and is taken to be the "optimum" A/F ratio...

EVERY single one of those cars benefitted at the race track by dumping more fuel into it (all EFI cars).

A dyno is just like those formulas. It will give you an "around-about" figure, but it isn't to be taken for gospel.

Joe