THE FOUR LITRE ENGINE STORY PART 3 IN PROGRESS
As promised in part two, I will tell the story of the attempts by the Ricardo test engineers to put the 4 litre engine to right.
Ricardo test log book job no. C665c
The small hard bound booklet contains the following information;
Engine VA4092 BM7860
Carbs 2 SU 42 mm
Arrival date 8th June 1931
Choke diameter for 220 ft / sec @ 2300 Rpm = 30.8 mm
06 / July / 1931. Old type cylinder block and cylinder head fitted.
12 August 1931. new camshaft fitted Drg C 305.
20 August 1931 Last entry in log.
ACCOUNT OF THE TESTS ( Taken from the handwritten reports in the file ).
Section 1. Experiments to improve the power output.
The tests fall naturally under two main heads, and have been so dealt with in the description which follows: In the first place experiments made with the express purpose of improving the power output are described and then follows an account of the tests made in relation to pre-ignition.
Preliminary running.
The engine had been used for acceleration tests at Brooklands and the first power curve obtained at these works was with the engine in the same condition as when used for these tests. The compression ratio was 5.4. Two 42 mm SU carburettors were used and with the control common to both carburetors set at “ normal “ the maximum BMEP was 94 lbs/sq.in at 2100 rpm; adjusted to give the best performance the maximum BMEP was only 100 lbs/sq.in at 2100 rpm and the torque curve fell off badly at low speeds.
A motoring loss test from 1100 – 3000 rpm showed that the losses were normal, the friction MEP being 26 lbs/sq.in at 2000 rpm.
Valve opening diagrams were taken and the timing was found to be as follows:-
Inlet opens from mask 19 degrees late.
Inlet closes in mask 46 degrees late.
Exhaust opens 66 degrees early.
Exhaust closes 15 degrees late.
This concluded the preliminary work on the engine and for subsequent tests it was arranged to control the mixture strength of each carburettor separately.
Now follows a series of tests and to make the results more interesting I have cut out a lot of the technical detail.
Test 1. The Ricardo engineers conducted a test with the mixture of each carburettor controlled independently to give maximum power output. This resulted in a 3% increase in maximum power, but as before, the power falling off badly at low rpm.
Test 2.
To try and account for the low torque the test engineers conducted a test similar to test 1 but
As promised in part two, I will tell the story of the attempts by the Ricardo test engineers to put the 4 litre engine to right.
Ricardo test log book job no. C665c
The small hard bound booklet contains the following information;
Engine VA4092 BM7860
Carbs 2 SU 42 mm
Arrival date 8th June 1931
Choke diameter for 220 ft / sec @ 2300 Rpm = 30.8 mm
06 / July / 1931. Old type cylinder block and cylinder head fitted.
12 August 1931. new camshaft fitted Drg C 305.
20 August 1931 Last entry in log.
ACCOUNT OF THE TESTS ( Taken from the handwritten reports in the file ).
Section 1. Experiments to improve the power output.
The tests fall naturally under two main heads, and have been so dealt with in the description which follows: In the first place experiments made with the express purpose of improving the power output are described and then follows an account of the tests made in relation to pre-ignition.
Preliminary running.
The engine had been used for acceleration tests at Brooklands and the first power curve obtained at these works was with the engine in the same condition as when used for these tests. The compression ratio was 5.4. Two 42 mm SU carburettors were used and with the control common to both carburetors set at “ normal “ the maximum BMEP was 94 lbs/sq.in at 2100 rpm; adjusted to give the best performance the maximum BMEP was only 100 lbs/sq.in at 2100 rpm and the torque curve fell off badly at low speeds.
A motoring loss test from 1100 – 3000 rpm showed that the losses were normal, the friction MEP being 26 lbs/sq.in at 2000 rpm.
Valve opening diagrams were taken and the timing was found to be as follows:-
Inlet opens from mask 19 degrees late.
Inlet closes in mask 46 degrees late.
Exhaust opens 66 degrees early.
Exhaust closes 15 degrees late.
This concluded the preliminary work on the engine and for subsequent tests it was arranged to control the mixture strength of each carburettor separately.
Now follows a series of tests and to make the results more interesting I have cut out a lot of the technical detail.
Test 1. The Ricardo engineers conducted a test with the mixture of each carburettor controlled independently to give maximum power output. This resulted in a 3% increase in maximum power, but as before, the power falling off badly at low rpm.
Test 2.
To try and account for the low torque the test engineers conducted a test similar to test 1 but
SORRY ABOUT THE DELAY IN COMPLETING THIS ARTICLE. I NEED TO GET SOME COPIES OF THE ENGINE TEST RESULTS FROM RICARDO BEFORE I CAN DO THIS.