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Duesenberg J-SJ

In Europe, the name Duesenberg is known just by a few car lovers and those few know just a little about it. On the other hand, it has long been legendary in the United States. Despite the name and the origin of its designers, Duesenberg cars had been constructed in America and nowadays they are very demanded by many of the great American collectors.

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The American dream


The fact that these cars are not acknowledged in Europe is due to a series of circumastances that has nothing to do with their real value (instead, the geographic distance and a separating ocean are already two good motives). Apart from the American nationalism, nothing can stop Duesenberg from being admired and considered one of the most extraordinary combinations of luxury, power and technology in the history of car-making.

August (Augie) e Frederick (Fred) Duesenberg were two german brothers with the mania for the mechanics who emigrated to the United States. In the 20’s, their racing cars started to be successful in Indianapolis, giving hard times to such opponents as Miller and Stutz. In 1924, they produced a passenger car called “type A”. It had an 8-cylinder in line engine with double over-head camshaft and 4 hydraulic brakes. In 1924, it was the only car with such a combination in the world.

In 1926, a famous American investor Erret Lobban Cord buys the Duesenberg brand with the intension of making it the highlight of his little car imperium. Cord gets Augie, who was too attached to the world of racing cars, formaly out of the way and orders a new super-luxury, super-strong passenger car from Fred and his reduced team. This is how the model “J” was born as the most powerful passenger car of the world.

Those of you with the good knowledge of the history of the brand know that the Duesenberg J would have never been made without Cord’s will and determination. Cord wanted an engine of remarcable dimensions with a racing typology, over-head camshafts and valves, and he also ordered a large chassis to be able to compete with the biggest and most luxurious European cars of the era.


The birth of J

The J was disponible in two versions of chassis with a different wheelbase, a long one (3.90m) and a short one (about 3.60m). But there are also two pieces of SJ (unofficially called SSJ), that belonged to actors Gary Cooper and Clarck Gable, with the wheelbase shortened to 3.18m. And you can also find a car with the wheelbase extended to 4m.
Despite being very robust, the chassis of the J was, along with the inflexible axis of suspensions, perhaps the weakest part of the car. The rigidity of this simple chassis was constantly put to the test as it had to support a unit over 5 meters long with the weight normaly exceeding two tons. The J had just the drum-breaks, even if equipped with an excelent hydraulic control, and they surely had hard times with such a heavy and strong car. While in 1929 these imperfections were still pardonable, in 1937, the last year of Duesenberg production, they presented a burden that could hardly be ignored in the face of already more advanced competitors.


The engine of the J: from the circuits to the street

The engine is the strong point of the Duesenberg J. It is a classical 8-cylinder in line of that period with the usual 2-4-2 crank gear. It has a displacement of 420 ci. or 6882 cc.; but the real rarity is the presence of two over-head camshafts commanding 32 valves or 4 valves per cylinder. The valve timing is accomplished by a big, quiet and reliable triplex chain.

In short, at the time the J was presented to the public, it was the only luxury passenger car with an engine of this type. The constructor declared the power of 246 Hp at 4500 revolutions. In the following years, there were many discussions about this figure and while some keep defending it, others say it isn’t credible. If you look at the post-war benchmarks and various testimonies it is safe to affirm that this figure was quite probably a little exaggerated. It is possible to estimate that the average horsepower of a new J was somewhere around 220 Hp. This figure, while being inferior to the originally declared one, was still far ahead the competitors.

The company’s fate was shaken by a tragic incident in 1932. Fred Duesenberg died in a car accident, while driving a new supercharged model of the J. This supercharged version of the J, the SJ, was presented to the public in the same year. The SJ was a super strong car that exceeded all its contemporary competitors by its top speed of over 200 km/h, but starting from this tragic incident, Duesenberg won’t make many steps forward. The dead of Fred caused a great discomfort and a definite stop to the evolution of the model J. The brand eventually disappeared in 1937...


The SJ: breaking the limit of 300 Hp

The Duesenberg SJ is one of the most fascinating cars in the history. like many of its competitors, it was produced in very few pieces (about 36) and has an inestimable value. The SJ was built from the standard “J” basically by adding a centrifugal supercharger and making few other modifications: its tubular connecting rods were instead of light alloy made of steel, it had different compression ratio, strenghtened clutch and hardened front suspensions. This was in outline the usual procedure of the factory but there never really existed two identical exemplars of the SJ.
All the SJ cars were custom-made according to the requirements of their buyers. There were for example at least 3 different types of inlet systems, with different carburettors and intake pipes, let alone the bodies that were heavily customized already in the J models by the choice of the coach builder.

The J was a big and heavy car. The additional centrifugal supercharger surely didn’t add much to its drivability but it made the car stronger and faster. It is again hard to tell how precise is the declared horsepower of 320 Hp at 4700 revolutions. The maximum speed could exceed the 200 km/h. This mainly applies to lighter short wheelbase models but it is not hard to find reports about long wheelbase models surpassing 210 km/h. The aerodynamic efficiency surely was not very favourable factor for such a giant as the J that had little to envy in its impressivness and dimensions to such road cruisers as Hispano Suiza V 12 o Maybach Zeppelin.
As far as the supercharging is concerned, experts on this subject exressed some considerations starting from the fact that the efficiency of centrifugal superchargers of this era was not very high.

In a more profound analysis we can say that the centrifugal supercharger of SJ models is basically an impeller placed between the carburettor and the engine. It collects the mix of air and gassoline and blows it into the intake pipes. The main problem lies in the fact that the impeller is powered directly by the drive shaft and so a big part of the power generated with the help of the supercharger is absorbed by the supercharger itself. Here, you can be tempted to make a logical conclusion that the horsepower declared by the factory is again not trustworthy... But it is just partly true and this problem can’t be settled so easily.

Some SJ models probably couldn’t even make 300 Hp, while others were able to heavily exceed this value. It wasn’t though the presence of supercharger that made themain difference but the whole feeding system that, as we already mentioned, could remarkably differ on each model. The compression ratio played its important role as well. And while the car of Ab Jenkins, made to beat the records, had a ratio of over 7:1, which was a really high figure in these times, the normal Js had the ratio lower then 6:1.

The decisive factor for boosting the power of an engine of J or SJ was almost certainly the use of two carburretors (or one special carburetor) and the choice of a high compression ratio that could vary a lot, as we have just seen.
This is also a part of Duesenberg charm. There is always a chance to find a surprise under its bonnet and every car, every engine has its own personality and own story...


The SSJ models

Just the concept of a special SJ is already astonishing as it represets a sort of rarity of rarity and yet there are models of SJ with the horsepower close to 400 Hp!
The most famous of them are surely the two SSJ that belonged to the actors Gary Cooper e Clark Gable. The inscription SSJ (same goes for SJ) has never been officially used by the company but it eventually became commonly used among the car lovers. The second “S” stands for “short wheelbase” and, as the metter of fact, the two SSJ cars are the only Duesenberg to have a chassis with the wheelbase shorthened to 3.18 m.
The two cars have survived up to these days almost in their original form. Both are rendered in two-colours, the one of Cooper in 2 shades of gray and that of Gable in gray-red.

The engine of both SSJ models is equipped by inlet ports of a special shape called “ram’s-horn”. Although they are an important characteristic of the SSJ, the ram’s-horns were also used in other models, for example in the white one shown here on the side. Unlike the normal port, the “ram’s-horn” is composed of two ports and each of these then splits in two again. And if you add the use of two special carburettors, you will get the complete masterpiece.

Perhaps the first model equipped by this device was the so called “Mormon Meteor”, the record-breaking car prepared for Ab Jenkins by August Duesenberg in 1935. Jenkins set a record, unequalled untill 1951, by driving this 400 Hp beast for 24 hours at the average speed of 135.57 mph. In theory, all the SJ models sold after 1935 should have the “ram’s-horn”. “Mormon Meteor” had the horsepower of 390-400 Hp (measured in the benchmarks in 1935) and is considered the most powerful Duesenberg ever constructed.
It is likely that the two SSJs are close to 400 Hp as well. All the SJ models with “ram’s-horn” probably have the horsepower far above 300 Hp.


JN and SJN

Here again the factory did not officially use the inscription JN, but it became commonly used to distinguish 10 particular cars produced in 1935 by an American coachbuilding company Rollston. All JN models have a wider body whose main mass doesn’t rely as usually on the longitudinal frame membes of the chassis but it covers them and descends down to the side footboards. Their smaller 17 inch rims present another distinctive element.

This is the list of existing JNs: 3 models of convertible coupè, 3 convertible sedans and 3 sedans with a long wheelbase. It seems that only two convertibles left the factory as SJ and these are usually called SJN.
All three sedans were model J, but it seems that a supercharger has been installed on one of them just before the war by no one else but Augie Duesenberg. It is likely to be the case of the white-red car shown on this page.




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