THE SPORTS CAR ENGINE ITS TUNING AND MODIFICATION
THE SPORTS CAR ENGINE ITS TUNING AND MODIFICATION
*
COLIN CAMPBELL M.Sc., A.M.I.Mech.E., M.S.A.E.
SPRINGER-SCIENCE+BUSINESS MEDIA, B.V. '9 63
© COLIN CAMPBELL 1963 ORIGINALLY PUBLISHED BY CHAPMAN & HALL LTD. 1963
SOff COVER REPRINT OF THE HARDCOVER 1ST EDITION 1963
SBN 412 07470 2
ISBN 978-0-412-02740-6 ISBN 978-1-4899-7204-0 (eBook) DOI 10.1007/978-1-4899-7204-0
TO MY FATHER who tuned motor cars before
tuning was invented
Show me the mechanic who pops out his chest and announces 'I don't need any fancy gadgets to tune a car, all I need is to listen to the engine.' Show me this man and I will show you a }!_yjJer-ep,otistical DOPE.
ToM McCAHILL
Preface
I HAVE ATTEMPTED to write in one volume a textbook on the theory of automotive engine tuning, always with a bias towards the more highly developed type of engine as used in the modern sports car. Engine tuning is treated in its two aspects, basic tuning and supertuning, i.e. the modification of a stock engine to increase the power output.
A supertuned engine operates with a tighter margin of safety than a stock engine and a loss of basic tune can soon lead to overheating, even to catastrophic failure. With this in mind the major part of the book concentrates on the theory and practice of basic tuning. Chapters are devoted to the ignition system, to carburettors and to the methods used in 'trouble-shooting'. All of this is of value to the owner-mechanic, the garage man and the trainee racing mechanic. Supertuning is the subject of Chapters Nine to Thirteen. Here I attempt to take the magic out of supertuning. So many of the latest methods used in the British, German, Italian and American tune-shops are based on knowledge obtained in the engine laboratories of universities, colleges and commercial research institutions throughout the world. Much of this knowledge is available to all of us, if we take the trouble to ferret it out. From time to time throughout the book the reader will see references to experimental work of this kind. The final chapter is on the mechanics of modification. By providing practical hints on the ways and means of engine modification this chapter should help to preserve the balance between theory and practice.
I am especially grateful to the editor of Sporting Motorist for permission to reproduce certain material used in Chapters Four, Five and Six, which appeared originally in that excellent journal as a series of articles on carburettor tuning.
CoLIN CAMPBELL Racine, Wisconsin, U.S.A.
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Contents
Preface
CHAPTER ONE
General Principles TUNING FOR PEAK EFFICIENCY AND POWER; \-\'here does the power go? The energy in the fuel. Cycle efficiency losses. Combustion losses. Transmission losses. THE PENALTY OF POOR TUNE, SUPERTUNING: Making it breathe; make it efficient; making it reliable.
CHAPTER TWO
Instruments TuNING INSTRUMENTS; The dynamometer. Garage instruments: tachometer; vacuum gauge; compression pressure gauge; fuel pressure gauge; stop-watch; voltmeter and ammeter. SPECIALIST INSTRUMENTS. Battery tester; ignition timing light; distributor analyser; tach-dwell meter; coil tester; condenser tester; plug tester; exhaust gas analyser; stroboscope; cathode ray oscilloscope.
CHAPTER THREE
The Ignition System Ignition requirements. The primary circuit. The secondary circuit. Secondary voltage variations. The phenomena of the spark. Sparking plug and contact breaker gaps. Dwell angle. Ignition timing. Sparking plugs. MAGNETOS: principles; types; care and maintenance.
CHAPTER FOUR
Mixture Formation, Distribution and Carburation The mixture. The boiling point range. Mixture and power. Distribution. Formation of the mixture. Manifold design. Pressure losses by distribution. THE MIXTURE REQ.UIREMENTS OF THE ENGINE; Starting and cold-running; idling; part-throttle operation; full throttle; acceleration.
CHAPTER FIVE
Variable Choke Carburettors THE S.U. CARBURETTOR: Starting; idling; full throttle and cruising; acceleration. The HD type. The HS type. Tuning the S.U. carburettor. Vacuum gauge technique. Multiple carburettors. Tuning after modification. THE S.U. TWIN-CHOKE CARBURETTOR.
IX
vii
17
42
59
74
X CONTENTS
CHAPTER SIX
Fixed Choke Carburettors
WoRKING PRINCIPLES: Mixture compensation; starting; idling; full throttle; acceleration. THE ZENITH: Series VN; Series W. THE SoLEX: Type 32 Bl; Type B 28 ZIC-2; Type C. 35 APAI-G. TuNING THE SoLEX. Tuning after modification. THE WEBER: the auxiliary venturi. The Type DCO. Tuning the \Veber.
CTTA PTER SEVEN
Testing and Tuning
The Importance of Testing. TESTING: The 11 Tests: initial roadtest; compression test; plug test; vacuum reading; battery test; coil and starter voltage; coil and condenser tests; contact breaker tests; fuel pump tests; mixture strength readings; valve clearances. TUNING: Tuning operations: valve clearance setting; sparking plugs; distributor; ignition timing; carburettors; final road-test.
C:IL\PTER EICIIT
Trouble-Shooting
Fault-finding with the vacuum gauge: valve trouble; induction leaks; broken piston rings; defective exhaust system. A short catalogue of troubles: bad starting; low speed misfires; high-speed misfire; overheating; fuel pump troubles.
C:IIAPTER NINE
Combustion Efficiency THE BASIC PRINCIPLES OF SUPER TUNING: Combustion efficiency. Mechanical efficiency. Friction and pumping losses. The compression ratio. Abnormal combustion. Knock. Other combustion abnormalities: rumble; pre-ignition; running-on. Combustion chamber shape: bath-tub head; wedge head; hemispherical head; ovrrht"ad inlet, side exhaust head.
CHAPTER TEN
Volumetric Efficiency
Definition. How to Improve Volumetric Efficiency. THE INDUCTION PROCESS: Inlet valve timing. Overlap. INLET VALVE AND THROAT DESIGN: The air flow rig. Flow calculations. Mean gas velo· city at valve throat. Mean gas velocity at valve seat. Carburettor venturi size. Valve seats. Valve throat and port design. Venturi ports. Curved ports. THE EXHAUST PROCESS: Exhaust valve si:te. EXHAUST VALVE THROAT AND PORT SHAPE.
91
129
149
170
192
CONTENTS
CHAPTER ELEVEN
Special Techniques MuLTI-CARBURETTORs: One choke per cylinder. Experimental measurements. Recommended pipe lengths. PETROL INJECTION: Port injection systems; Rochester/Corvette; Lucas/Jaguar; Mercedes Benz 300 SL. THE INTAKE AIR: Cold air intakes. .Forward ram intakes. RAMMING EXHAUST PIPES: Branched exhaust pipes. NEW IGNITION TECHNIQ.UES: Transistorised systems; electro-magnetic systems; piezo-electric systems.
CHAPTER TWELVE
Cams and Blowers SPECIAL CAMSHAFTs: Factory options and re-grinds. The cam profile. The actual valve motion. Spring surge. Cam-face wear. When to fit a high-lift camshaft. BLOWERS: The mechanics of supercharging: Vane type; Roots type; Centrifugal type. SuPERCHARGER TUNING TIPS: Heat rejection; Blowing through the carburettor; Carburation for blowing; The drive. TuRBOCHARC11NG: Corvair; Oldsmobile.
CHAPTER THIRTEE:\"
The Mechanics of Modification CYLINDER HEAD WORK: Compression ratios and how to change them. Measuring the clearance volume. High compression pistons. Machining methods. Work on the ports. INCREASING THE LIFE OF COMPONENTS: Crack detection. Shot peening. Balancing. WoRK ON THE VALVE GEAR: Push-rods. Tappets. Rockers. Springs. CONNECTING RODS, PISTONS. SPARKING PLUGS. EXHAUST VALVE MATERIALs: Exhaust valve troubles.
APPENDICES
Xl
223
254
275
1. Special Camshafts 298
2. Champion Engineering Racing Division Heat Range Comparison Chart 310
3. Suggested Maximum Torque Values 312
4. S.A.E. Horse Power 314
Index 317
List of Plates
(The plates are inserted as a section between pages 148-149)
I. Multi-carburettor synchronising gauge marketed by Rally Engineering The Rally Engineering device in use on a Sunbeam Alpine
2. Normal plug appearance Dirty plug
3. Oily plug Overheated plug
4. Broken insulator nose Flashover
5. Aluminium alloy head for the 'B' Series B.M.C. engine A special rocker cover
6. Kit for Stage-2 conversion of the Austin-Healey 'Sprite' and M.G. 'Midget'
Cast alloy cold air box for the 'Sprite'
7. Twin-choke Weber carburettor kit for Triumph Herald The TR3 and TR 4: racing engines
8. Exhaust extractor devices: the Alextractor S.A.H. oil cooler kit
9. The Judson supercharger kit for the 'Sprite' With the fitting of a Judson supercharger kit the Mercedes Benz
l90SL is transformed into a 'tiger'
10-15. The case history of a successful 3-litre Austin-Healey
16. The component parts of the Lucas electronic ignition system for an 8-cylinder engine with fixed ignition timing
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