%OP%PL64
%OP%TM1
%OP%BM1
%OP%LM5
%OP%HE/%H2%Z88 Users' Club Software Library%H2%/
%OP%FO/Z193//@P@/
%CO:A,12,70%%C%Z193  %H1%CAR PERFORMANCE ESTIMATE%H1% 

%H2%Introduction

This is a method for the estimation of car performance when frontal 
area, drag coefficient, mass, power and weight distribution are 
known. Some of the uses of the program are as follows:







%H2%Files

Z193A
Z193B
Z193C
Z193D
Z193E

%H2%Operation

type in INPUT.FILE.NAME or if Z193 <ENTER> ?  

datafile D  interactive <ENTER>?  


Vehicle Title ? 
aerodynamic constant Ca  if .02177 <ENTER>?  
transmission constant Ct  if .45 <ENTER>? 
frontal area A (ft^2) ?
mass M (tonnes)?
power P (bhp din) ?
coefficient of friction mu  if 0.9 <ENTER> ?
front wheels static load fraction  Pz1/M static ? 
(vertical centre of gravity)/(wheel base)  Zcg/WB  if .25 <ENTER>?  
front wheels aerodynamic load fraction  Pz1/M aero  if 0.5 <ENTER> ?
lift coefficient Cl  if 0.0 <ENTER> ?  

[]P
<>FL
DATA/Z193
'Load as plain text' Yes


%H2%Input data

Ca






Ct




A


















Cd




M



P




F R or 4




mu



Pz1/Mstatic



Zcg/WB




Pz1/M aero



Cl



%H2%Theory

In the derivation of the formulae the following assumptions were 
made:
 1. Linear relationship between transmission losses and power. 
 2.Rolling resistance is negligible.
 3.Proportions of power delivered at maximum speed and transmission 
losses relative  to max. b.h.p. are the same for all vehicles of the 
particular class.
 4.Manual transmission in relation to max. speed calibration.
 5.Constantly Variable Transmission  in relation to acceleration 
formulation. 
 6.Constant power during acceleration.
 7.Similarity of power train technology standards for all vehicles of 
the particular class.

The assumption of negligible rolling resistance is not ideal but can 
be justified by noting that at high speed, aerodynamic drag is 
dominant and at low speed, mass acceleration force is dominant. The 
assumptions of C.V.T. and constant power are justifiable because, 
although manual gearboxes contain discrete gear ratios, during 
acceleration the engine operates in a finite power band. The analysis 
assumes an average power within this band.
%CO:B,12,60%






1.Verification that published test performance is 
realistic
2.Performance estimation for cars not tested
3.Estimation of power or Cd.A
4.For cars with same Ca.A, estimation of performance or 
power.

                                                 

this document
program
example one - mini 1430cc               re-name DATA/Z193C
example two - ford sierra 2.0           re-name DATA/Z193D
example three - formula one racing car  re-name DATA/Z193E




option to specify data file name, default is DATA/Z193

option to RUN from existing data file, which may have 
been edited, or to RUN interactively
















if required, edit input data and re-run



Constant of proportionality for aerodynamic drag
This is based on tested max. speeds of a broad range of 
road cars and should typically be taken as 0.02177 . For 
a formula one car a value of 0.0196 was found to be 
appropriate: the variation of the value compared with 
that for road cars is not suprising as the two classes 
differ greatly. The method of deriving this constant can 
be supplied. Constant for power, gearing and weight 
correction This is based on tested acceleration of a 
broad range of road cars and should typically be taken as 
0.45

frontal area (ft^2)
In deriving the values of Ca and Ct, Cd.A values were 
taken from Autocar magazines dated 25 09 82 and 11 12 82. 
It can be difficult to obtain values of A for a 
particular car but if the max. speed and power of a 
variant are known, the program can be repeatedly RUN 
varying A until the known max speed is output, noting 
that it is only necessary to use a unit Cd of 1.0 during 
this process. Having obtained an effective Cd.A, the 
program can be used to estimate the effect of varying any 
of the input parameters for the car. It may be possible 
to obtain the value of A either from manufacturer's data 
or by measurement. A possible means of measurement is to 
photograph the car from the front, sum the area 
constituents by means of grid lines and scaling the 
result by means of a reference measure visible on the 
photo. Note that the visible parts of the tyres must be 
included in the area summation.

drag coefficient
This may either be obtained from manufacturer's data or 
Cd.A may be estimated in the manner described for A 
above.

mass (tonnes)
This must be an operational mass, typically including two 
adults, 1/2 tank of petrol, water and oil.

power (bhp din)
DIN is recognised as being a strict measure of power and 
the uniformity this provides is the principal reason for 
using it.

FWD RWD or 4WD
Drive configuration constitutes one of the parameters 
determining traction and therefore acceleration at low 
speeds.

road/tyre coefficient of friction
Traction parameter. For road cars a value of 0.9 is 
probably reasonable.

front wheels static load fraction
Traction parameter. Equivalent to front/rear weight 
distribution.

(Vertical Centre Of Gravity)/(Wheel Base)
Traction parameter. For road cars a value of 0.25 is 
probably reasonable.


front wheels aero. load fraction
Difficult to obtain. Will have negligible effect on road 
cars, use a value of 0.5

lift coefficient
Difficult to obtain. Will have negligible effect on road 
cars, use a value of 0.0
%CO:C,12,48%%CO:D,12,36%








































enter pipedream
file load command
file name
%CO:E,12,24%%CO:F,12,12%%CO:G,12,0%%CO:H,12,0%%CO:I,12,0%%CO:J,12,0%%CO:K,12,0%%CO:L,12,0%%CO:M,12,0%