Does anyone know what boost pressure a blown ulster produced when new ?

Probably wrong but 5psi springs to mind

The absence of a boost gauge on the car as supplied to the public leaves us without contemporary reports.

Does Harrison give a number? My copy is packed away.

Julian Hunt's interview with Charles Goodacre about the blown car used on the Mille Miglia states "On test the car wouldn't pull more than 3500 .....The pressure relief valve on the blower had broken so Goodacre used an inner clutch spring, which gave 17 psi on a borrowed boost gauge".

I think I know what is being said here but my interpretation may be wrong. I presume the PRV spring had failed. Goodacre wouldn't have a huge choice of springs to play with in Italy but (if it were me) I'd be looking for something that blew off at about twice expected manifold pressure so 17 psi isn't silly. It was an extempore fix so near enough had to be good enough. I wonder exactly how he tested it? I'd use a spring balance since the valve area is roughly 1 square inch or a bit more?

I can only comment on a"used" Cozette on a modified engine and, of course, even then I can only tell you the pressure in the manifold which is obviously dependent on engine spec. Having said all that, if you see 5 psi in the manifold at 5000 rpm in top on a long straight, I'd say that might be right.
Or in other words, Dave, no!

I wonder if Gallays retain any figures from Cozette as to the expected pressure when driven on a lathe?
Regards,
Stuart

I thought,only a guess that it would have been 5 or 6 psi driven at engine speed.

Hi Dave, picking out the odd nugget from the Companion (which may, of course, be incorrect) it would appear that the blower ran at 0.88 engine speed (Bill Sheenan) giving 5 to 8 lb. boost delivering 33 BHP @ 5000RPM(engine).

Ian Mc.

Location: Shropshire

My blown engine on a Shorrock C75B gave 32.5bhp @ 5000rpm as tested on Stuart Rolt's dyno. The blower was run at about 0.85 engine speed. Tallies very closely with the figures above.

Location: North Yorkshire

A call to Reg Nice may elicit the information he ran his hill climb car for many years with an original Cozette. I have never seen any contemporary figures for boost other than the works cars were run at higher speed and hence presumably higher boost.

This link:- http://www.austin7racing.com/charles-goodacres-mille-miglia/ includes:-

The engine had a pressure fed roller crank, 6:1 compression ratio, a Solex carburettor supplied the mixture to a No 4 Cozette supercharger (built by Austins) blowing at 9 psi, and with magneto ignition by BLIC, 46 bhp was produced at 5,000 rpm. The maximum revs allowed were 5,800 and the engine ran on KLG 356 mica plugs

Location: Oxfordshire

How silly of me. I should have re read the whole article instead of just the bit I remembered. Thank you, Austin.
It's interesting that Austins (re)built the blower. I wouldn't have thought you could increase its efficiency, just the reliability - and they took a spare. They must have lacked confidence in M. Cozette!
I used to see 9 psi on one of my cars with the throttle well open but I can say with reasonable confidence that the camshaft design was partly responsible.

Regards,
Stuart

That was a works car built for one event, it wouldn't have been standard!

Even VE 9594, (factory supercharged car) had some works support in that they sent a "*******" gear to drive the supercharger faster. I'm sure when dad / current owner see this they may say more.

Location: United Kingdom

Standard 15 tooth drive gear,1:1. 14 tooth corrected tooth form,used by works 1.07 x engine speed I believe.

From a Massachusetts Institute of Technology lab test of a Cozette done in 1927 by a chap called Charles W Snow I can quote:

The results of this test tend to show that the efficiencies of this supercharger are rather low, that for best overall efficiency a discharge pressure of 6# / sq.in is best, but that, as may be expected,volumetric efficiencies are better at lower pressures. From the stand point of heating, high pressures are prohibitive, particularly when accompanied by high speed, although the fact is apparent from the data that the temperature is a function of the pressure almost solely, heat from friction being practically negligible.

Anyone who wants a copy can email me

Best wishes

Charles