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Useful Technical Information-Assistance & Reference Formulas *************************************** How to Perform a Proper Plug CutSpark
plugs are the “window” that you look at the engine’s operating conditions at
anytime. If you know what to look at and how to interpret what you observe,
“reading”the ceramic insulators of the spark plugscan tell you whether it’s
lean or rich, whether its detonating or approaching These procedures work
the same for fuel injected, carbureted, or turbocharged engines. OK, now it’s to time do
this…if the plugs are to be read on-the-spot, then an extra set isn’t
necessary to take along. If the plugs are to be preserved for somebody else
to read later, then you’ll need an extra set of them along with your plug
removal tools. Find a nice straight
stretch of road at least a few miles long, after all, you are going to hold
the car for in 4th or 5th gear for a minimum of 30
seconds or longer. Accelerate to speed and
into the next to top gear, 4th for a 5-speed and 5th
for a 6-speed. Hold a steady throttle either at half or full (wide open) and
make a mental note of this since you should observe the plugs in both regimes. After holding the
appropriate throttle setting for 30-45 seconds, quickly switch the ignition
off as you simultaneously push the clutch in and shift into neutral. You are
trying to “cut” the engine off at that exact setting that you’ve held for
30-45 seconds without allowing it to drop to an idle. Engine & Performance Formulas Engine Displacement Cylinder Displacement: Bore X Bore X Stroke X .0031416 ÷ 4 = displacement Multiply this number by the number of cylinders to see total engine size. Enter data in millimeters. Horsepower Brake HP= Torque X RPM ÷ 5252 Example: Torque is 300 lb-ft X RPM is 4500 = 135000 divided by 5252 equals 257 HP @ 4500 RPM Drag Horsepower This is the amount of power required to move a car through the air. Drag HP = Frontal Area X Drag Coefficent X Vehicle Speed³ divided by 146000 Example: 18.5 sq ft X .40 X 170MPH³ is 4913000 ÷ 146000 = 249 HP This doesn't take into account rolling drag from the tires but gives a close idea about the power required for different speeds. Gearing is the other variable to consider. Vehicle Dynamics Speed = Tire OD" X Engine RPM X .002975 divided by the Final drive ratio Don't forget to factor 5th gear against the ring & pinion ratio Lateral Acceleration in g's = MPH² divided by acceleration of gravity (32.2 ft/sec/sec) X turn or circle radius Example: 50 MPH X 50 MPH+ 2500 divided by 32.2 X 100 = 3200 gives .7763975 g's for this 100 ft circle Conversions Centigrade = 5 X (Fahrenheit temp-32) divided by 9 One Newton-meter (Nm) = 1.356 ft-lbs One Newton-millimeter (Nmm) = 5.75 in-lbs Torque: SAE lb-ft = Newton Meters
Torque: Newton Meters = SAE lb-ft
CO-to-Air/Fuel Ratio Conversions
********************************************* Measuring Wheel Offsets Wheel/tire-to-fender clearance issues are more commonplace now due to the popularity of stuffing very wide tires into existing bodywork. To assist in minimizing fender rubbing problems, here is a guide to finding wheel offsets to ensure that your wheel-tire combination will fit inside your bodywork without rubbing. Backspacing is the dimension from the inner rim of the wheel to the mounting face and you will need to calculate this for proper fitment. 1) Divide your wheel's width by 2. This leaves you with the centerline of the wheel. 2) Find the backspacing by measuring the distance between the mounting face (where the wheel meets the hub) and the edge of the inner rim. 3) Suntract the backspacing distance from the centerline distance to find wheel offset. 4) Measure the distance between the mounting face on the hub to the fender. Use the measuring tape and a yardstick positioned vertically at the inner edge of the fender. 5) Measure the distance between the mounting face on the hub to the suspension. Use the measuring tape and a carpenter's square for accurate dimensions. Factor some extra space for tire clearance. 6) Measure the overall wheel width and with the above values, you can figure out what width wheel you can use and the offsets required for fender and suspension clearance. Please remember that you can mount several sizes of tires on a given wheel width so allow for that. Every tire manufacturer provides sectional and tread width values for every tire. 911
Fuchs Wheel Data
OBD-II Readiness Driving Cycle One of the most common problems with OBD-II cars ('96-0n) are smog test failures due to readiness codes not set and the ECU will test as "Not Ready". Here are some procedures for setting all 9 readiness codes in OBD-II ECU's. These "Diagnostic Trip" steps MUST be followed to the letter otherwise you will have to start all over again. Review these carefully so you can see what you will be doing before you begin. 1) Start cold engine and idle for approximately 2 minutes, 10 seconds. This checks secondary air injection and evaporative leak detection systems. 2) Accelerate to 20-30 MPH and maintain steady speed for 3 minutes, 15 seconds. This establishes closed loop oxy-sensor operations, response times & switching times. 3) Accelerate to 40-60 MPH and maintain steady speed for 15-20 minutes. This evaluates catalytic converters while oxy-sensor response and switching times are checked. 4) De-accelerate and come to a stop. Idle in gear for 5-6 minutes. This checks evaporative leak detection system. Remember: The diagnostic checks above will be discontinued if: 1) Engine speeds exceed 3000 RPM 2) Large fluctuations in throttle position 3) Road speeds exceed 60 MPH _____________________________________________ More information to come!
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