Every Formula Youll Need 


Went to a tech lecture here in so cal put on by Oscar Jackson of Jackson
Racing, and Doug from Hondata (forgot his last name, but he was one of the
big dogs there) Well anyways, we got a big stack of papers and one of them
had a list of all important formulas for determining just about everything
for our cars. So take a gander and print this out and keep it with your
tools and stuff, cause i know this will come in handy for all of us here in na tuning. (btw, if there is anything wrong with the formulas, dont blame
the messenger)

- Rod ratio = Center line to center line length of rod / Stroke 1.74 or
greater is most desirable for racing.
- Air temperature = every 7 degrees F > 60 degrees F = 1% loss in
horsepower
- CI displacement = bore x bore = ____ x .7584 = _____ x stroke: divide by
.061 for CC x number of cylinders
- Compression ratio : Volume of the cylinder , piston dish and head dish and head gasket from top to bottom of stoke, divided by the head , piston, and
headgasket volume or: bore(in) x bore(in) = ____ x stroke(in) = ____ / .061
= cc of cylinder + head cc + piston cc + headgasket cc) / head cc +
piston cc + headgasket cc) = compression ratio 
- Piston speed in fpm = stroke(in) x rpm / 6
- Piston speed desired = 5800 fpm or less
- Horsepower = rpm x torque / 5252
- Altitude effects on horsepower: every 1000 ft above seal level = 3% loss
in hp
- Engine cfm approximation: RPM x C.I displacement / 3456 = approx. cfm.
Example: Civic 1.6L = 97 C.I. x 7200 rpm = 698400 / 3456 = 202 cfm.
- Calculation of cfm from horsepower: HP x .5 (BSFC) = ____ lb. per hour of
fuel x 13.2 air/fuel ratio = ___ lb. air p/hr / 60 min p/hr = ___ lb. p/min
/ .07 = cfm. Example: Civic 1.6L = 127 hp x .5 = 63.5 lb. p/hr fuel x 13.2
air/fuel ratio = 838.2 air p/hr / 60 min/hr = 13.97 lb. p/min / .07
(conversion fo cfm) = 199 cfm
- injector flow increase vs. fuel pressure increase: The square root of new
fuel pressure / original fuel pressure x the original fuel injector flow =
___ new flow in lb/hr. Example: 1.6L Civic with auxillary FPR. Take the
square root of 70 psi (new FPR setting) / 40 psi (original FP) = 1.3229 x
24 lb/hr = 31.75 new flow rate in lb/hr
- Injector sizing for hp: Desired hp x .5 (BSFC) = ___ lb of fuel pressure
required for desired hp / ___ amount of injectors = ___ lb. per injector x
___ duty cycle = lb. p/hr per injector
- Fuel pump or injector horsepower capability = Pounds p/hr at fuel
pressure desired x 2 = HP capability
- Gallons p/hr to pounds p/hr = ___ gallons x 6 = ___ lbs. p/hr
If you have any others please post em up on here, as i think we can get a
really good amount of usefull formulas, and this would really be a big help
to all who do the owrk our selves and build motors...
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