Cylinder Pressure

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David Morris
Posts: 837
Joined: Thu Feb 09, 2006 9:23 am
Your interest in the forum: Jowett Javelins since 1964. Now a Jowett Stationary engine owner and club member since 1964.
Given Name: David
Location: Sunny Bristol

Cylinder Pressure

Post by David Morris »

Hi All,

My Jowett Stationary engine has the Jowett two cylinder engine that is basically the same as those in the pre-war engines. Can someone tell me what cylinder pressure would be expected as 'normal'?

I have measured mine and they are equal at 50lbs/in. I realise that I only have the manual crank handle and, honestly, I wouldn't want much more compression as it's hard enough to crank as it is!

For comparision, on the Javelin the pressures were ususally around 125lbs/in, but I realise that this is with a much higher compression ratio and smaller pistons.

In a more realistic comparision, I understand that a Ford Model T, with it's 4:1 compression ratio, is usually expected to have a cylinder pressure of 40-50 lbs/in.

So, what can be expected in the Jowett engine? I would be very interested to have your thoughts?

All the best,

David
David Morris
Posts: 837
Joined: Thu Feb 09, 2006 9:23 am
Your interest in the forum: Jowett Javelins since 1964. Now a Jowett Stationary engine owner and club member since 1964.
Given Name: David
Location: Sunny Bristol

Re: Cylinder Pressure

Post by David Morris »

Hi All,

After a bit more research, I see that the compression ratio of the WP engine on my generator is 5.4 :1. I wonder what the compression ratio was in the Jowett engines used in per-war two cylinder cars and vans? Obviously, this will have a direct bearing on the cylinder pressures.

All the best, and thanks for any advice,

David
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