Combustion Chamber Design

FOR POWER AND RELIABILITY – A VERY LONG LEARNING CURVE

When Bill Bonner was the slide rule man at Weslake and Co, Harry Weslake would wander into the Drawing Office most days, and we would all discuss combustion, and airflow, ports, valves, piston shapes and more about combustion chambers.

In the opinion of many, Harry Ricardo and Harry Weslake were two of the greatest pioneers in this field.

Talking to Harry Weslake for an hour or two a day for several years was quite an honour, at the end of which one might suppose that there was nothing left to know on the subject.

Theorising is one thing, but Harry Weslake was not theorising when he designed the BMC ‘A’ Series cylinder head, and the ‘B’ Series. They had to work. They had a sound philosophy why they should work, and they did. BMC paid him 25p per engine for the royalty on his patent. He also designed the Jaguar XK cylinder head, which equally had to work, and did.

So faced with the absolute necessity of designing the Jaguar V12 Combustion Chamber to survive at 800 bhp, which had to:- a) have superlative combustion characteristics, particularly to negate the detonation, and b) have excellent airflow to achieve the power output, Bill Bonner sat down and wrote a paper on the subject of combustion and detonation, to crystallise his mind on the subject, and in the process he propounded new theories which explained all the evidence of burnt pistons and burnt heads, burnt valves and burnt turbochargers.

This paper was not intended for publication, but for our own use, and still is to this day, because the theories turned out to be sound, and  were embodied in the Jaguar V12 Combustion Chamber which was a resounding success.

The best power achieved from the Jaguar V12 was 830 bhp, 320 bmep, at which level the fuel consumption was 1 gallon per minute.

At the same time, we were developing the Ford Mileage Marathon engine and the same combustion philosophy still applied with an engine giving only 0.6 bhp, 134 bmep and sfc of 276gr/kw.hr.  Considering we took the world record up to a resounding 3802 mpg, if we weren’t the world’s experts on combustion, who was?

When we came to design and make the Bonner 5,8 litre V6 engine, all this technology had to be harnessed. Instead of 0.6 bhp per cylinder with the little Ford, or even 69 bhp per cylinder with V12, now we were aiming for 150 bhp per cylinder with the new V6, and we achieved it.

INTERNAL COMBUSTION IS SOMETHING WHICH YOU CANNOT SEE, BUT IT IS POSSIBLE TO PICTURE WHAT IS HAPPENING FROM 1 MICRO-SECOND TO THE NEXT, AND FROM 1 MICRON OF SPACE TO THE NEXT, AND THEN DEDUCE FROM EXPERIMENTAL RESULTS WHETHER THE PICTURE IS REAL.