Gary Cooper's 1935 Duesenberg SSJ

  • Bob Roller
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05 Jun 2013 11:16 #25340 by Bob Roller
Bob Roller replied the topic: Cooper SSJ
I have that 8-87 issue of SIA and think Iread in the specs on that car that it had a compression ratio of 8:1. Is this an 8:1 ratio PLUS the supercharger or an equvilant figure? Seem to me the high compression plus the supercharger would create an extreme ratio that could blow head gaskets or even the engine. Anyone have any opinions on this?

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05 Jun 2013 13:10 #25341 by silverghost
silverghost replied the topic:
Bob~~
I do not know the actual real answer to your compression ratio question for this SSJ~~~~ especially without the added-on supercharger boost pressure.

But that figure seems very high, with or without, that added supercharger pressure given the octane of the fuels generally available around in this 1930s time period .

It was not until after WW II that higher octane fuels were made widey available to the general public that could actually handle those compression ratios you have mentioned in my opinion~~~
These higher octane fuels were developed during the war in order to get more horsepower out of war aircraft, PT boat, and Sherman tank air cooled engines .
As the war years progressed supercharger boost pressures & compression ratios got higher & higher to increase engine horsepower, speed, & overall engine performance.

This email address is being protected from spambots. You need JavaScript enabled to view it. BRAD HUNTER Huntingdon Valley Pa/Ocean City NJ 215 947 4676 Engineer & RE Developer Brass & Classic Auto, Antique Boat, Mechanical Automatic Music Machine, & Jukebox Collector

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05 Jun 2013 15:35 #25343 by landmark
landmark replied the topic:

silverghost wrote: Bob~~
I do not know the actual real answer to your compression ratio question for this SSJ~~~~ especially without the added-on supercharger boost pressure.

But that figure seems very high, with or without, that added supercharger pressure given the octane of the fuels generally available around in this 1930s time period .

It was not until after WW II that higher octane fuels were made widey available to the general public that could actually handle those compression ratios you have mentioned in my opinion~~~
These higher octane fuels were developed during the war in order to get more horsepower out of war aircraft, PT boat, and Sherman tank air cooled engines .
As the war years progressed supercharger boost pressures & compression ratios got higher & higher to increase engine horsepower, speed, & overall engine performance.


Hello,

I would guess that for a power output of 400 bhp @5000 rpm an uncharged J-engine (equiped with 4 single carbs) will need a compression-ratio of 9.5:1 or higher. So I think the (mechanical/static) ratio of 8.1:1 for the supercharged SSJ will be right.

I am not an expert, but I have read (can't remenber the source) that in the 1920ies and -30ies, it was not unusual that fuel was mixed with some ethanol. The Octane-number of pure ethanol higher than 100 (108?). So a mixture cold have had an octane-number >90

Here I have a link to that data-sheet Bob Roller is talking about <!-- s:wink: --><img src="{SMILIES_PATH}/icon_wink.gif" alt=":wink:" title="Wink" /><!-- s:wink: -->

http://images.hemmings.com/wp-content/u ... 5_1000.jpg

The question is, how much pressure the supercharger is able to produce. I don't think that the charger-construction is able to produce a very high pressure, but I don't know it.
Maybe someone knows more about that and like explain it.

Cheers

Matt

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ist selten ganz besonders gut

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05 Jun 2013 15:54 #25344 by silverghost
silverghost replied the topic:
Looks like I may be wrong here ~~~? ?

Are we talking about 4-8 PSI supercharger boost in addition to that 8.1:1 normally asperated piston/combustion chamber compression ratio ?

OR~~~
Is that ratio With the supercharger boost already factored in ?

That would make a BIG difference !

Do these model "J" superchargers have a safety anti-backfire control pop-off valve~~~?

I had thought I had once seen, many years ago, a model "J" engine in my general area where one of the aluminum intake manifold aluminum pipes had exploded & blown-apart like a grenade due to a leaking, or stuck open, intake valve and the resulting backfire explosion pressure ?

This email address is being protected from spambots. You need JavaScript enabled to view it. BRAD HUNTER Huntingdon Valley Pa/Ocean City NJ 215 947 4676 Engineer & RE Developer Brass & Classic Auto, Antique Boat, Mechanical Automatic Music Machine, & Jukebox Collector

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