Steve Cattaneo

Nicole,

A friend of mine has a late model MB diesel car that had an engine drivability problem, he took it to a Mercedes dealer five times for the same problem, the shop Forman told him they have no experience with diesels , an independent MB shop fix the car. MB paid the bill.

Steve Cattaneo

Bigs,

Porsche had no experience in building V8 water cooled engines, there engine expertise were air cooled, Mercedes in the 1950s had aluminum block water cooled engines running in there racing cars.
While the factory was officially out of racing in Europe, the SCCA welcomed the 300SL roadster into its D Sports class in 1957. They weren't allowed to run in production classes yet because of low production volume, so Mercedes-Benz's powerful racing impresario, Rudy Uhlenhaut, built two special ultralight cars for American racer Paul O'Shea.
These ultralights, with aluminum blocks, drilled suspensions, aluminum bodies, tanks and steering columns, magnesium bell housings and everything else superfluous, were the only two cars ever called 300SLS (it's the same old story; only two were built, but eight survive). O'Shea raced them nationally and won the class handily in 1957.

Another fleet of 450SLC 5.0s finished 1-2-3-4 in the 3,500-mile Bandama rally in December, 1979. These were the first V8, automatic-transmission cars ever to win an FIA rally.
The 450SLC 5.0s were special lightweight 300-bhp 5.0-liter V8 versions of the 450SLC for Group 4, with aluminum engine blocks and reinforced chassis. In 1980, the factory modified them still more, calling it the 500SLC, and ran all season without a win until the last event of the year, the 3,200-mile Ivory
The 928 auto transmission was made by and built by Mercedes, page 15 in the Porsche 928 performance portfolio book. I read some were, I don’t remember were, Mercedes accused Porsche of copying there V8 engine design. See page 20 of the Porsche 928 performance portfolio book
Porsche did improve MB engine design, the spider intake is one and the variably intake on the 32valves another, the use of the timing belt instead of a chain and some other changes.

bigs

Steve -

Interesting info. Thanks. Wonder what the advantage of a timing belt is over a chain? Seems like the belt is the shark's soft underbelly.

nine-44

I'll chime in here if you guys don't mind. The debate has been chain vs belt over on the 944 boards a few times before. Seems that a chain will not allow enough slack for the expansion rate of an all aluminim motor, the belt was the route they chose to deal with this isssue. I'm sure with R&D, they could have come up with an active tensioner for a chain design. I'm sure cost was an issue(more so with the entry level 944 series) and the belt was chosen.

Personally, I feel, if there was as much time money and effort put into the 944 series as the 911 series, it would far surpass it. The 928 with basicly twice the motor as the 944, would have been flat out murderous! But, with the 911 being Porsche's roots, flagship and "baby", the lesser cars were shipped with hand-me-down and acceptable technology, not further work needed to sell them. Don't get me wrong, they did build a great motor(or half of a motor for the 944), they just didn't go for full potential on a lesser priority than the 911. I just wish they had!

nine-44

While I'm thinking about it, when I worked for a P-car dealer. One of the techs was saying that a 928 motor will "grow" as much as 3/8"-1/2" measuring from cam to cam from heat expansion. I don't think a chain would like that much at all. My guess would be snapping the ends off of the cams as a result.

Adrian

The All-aluminium V8 was an American invention (the V8 itself being credited to the Americans as well in 1915 with the first running examples made circa 1923).
Ford produced these all-aluminium V8s in very large quanties during WW2.
Post war the all-aluminium design was enhanced by many companies. MB are mentioned above and joining this list is Ford again with the "Indy" DOHC All-aluminium V8 that was also fitted to the first two Ford GT (GT40) prototypes. There are many other examples.
All-aluminium V8 engines were used in series production cars such as the Sunbeam Tiger and Aston Martin DB6 and Volante during the 1960s and these engines were not based on the Buick designed all-aluminium V8 engine which appeared in the Rover, Triumph Stag and Range Rover to name just three.
All-aluminium V8 racing engines were produced by companies such as Repco (DOHC-1960), Datsun and Toyota (SOHC version 1967 and DOHC version 1968).
The timing belt design idea for the Porsche V8 used in the 928 according to Karl Ludvigsen came from the Chevrolet Vega V8 engine.
The first V8 design penned by Porsche KG shows up in 1948/49. Anyone familiar with Porsche design activities in the 1950s and 60s will know they brought in many engines from other companies to see how things worked. In fact it was even considered in circa 1960 to outsource the engine manufacturing to other more established companies.
Whilst Porsche KG concentrated on flat fours, sixes, eights and twelves they were always looking for improvements and changes.
The first front engine rear transaxle concept and its first practical application can be traced back to the USA in 1936.
There is a solid argument that the Porsche KG decision to use the front engine rear transaxle design came from the original VW design that morphed into the 924 which went to the market before the 928.
Transaxles of course were nothing new and had been in use since the 1950s. One of first automatic transaxles (2-speed) was developed by Ford USA for the Ford GT (GT40) in 1965. They raced it as well.
The actual Porsche 928 itself is very unique, but its engine and transaxle transmission are derivatives of what had come decades before.
Derivative does not mean directly copied, but the 90 degree all-aluminium V8 was not invented by Porsche KG, nor was it new, not even in 1971.
Ciao,
Adrian.

PS: To improve the breathing and operation of the air intake side of the all-aluminium V8s an American racing icon Dan Gurney who worked with the English company Weslake and the American company Eagle deserves a lot of the credit. J.W. Automotive also did a lot of work in this area especially with the 302 and 351 size engines.

Dennis Wilson

Adrian,

Lots of great information and clarification. It is clearly obvious that a lot of the aluminum engine technology was around when the 928 engine was developed but, back to the original question, was the 928 engine a clean sheet design or was it a clone of a previously developed engine? Inquiring minds would like to know.

Concerning the front engine rear transmission design, the 61/62 Pontiac Lemans had that design before the 924 or Ford GT40.

Dennis

bigs

Somebody talk to me about the angle of the 928 V8. Is it not a 90 degree engine? And isn't that more of an angle than one generally sees in a V8? ...All for the purpose of being able to shoehorn that big engine under the hood and still keep the car low in height as I recall?

So, what about an even greater angle? Obviously you'd need more width in the engine bay to accomodate it, but are there any advantages/disadvantages from a mechanical engineering standpoint?

I mean, Porsche had so much experience with a flat 6, I wonder why not a flat 8?

Dennis Wilson

The 90 degrees refers to the angle of the rods to each bank. A larger angle would put the cam carriers into the wheel wells and a smaller angle would put them into the hood. The flat 8 concept could have worked but would have required a much shorter stroke/larger bore to maintain the overhead cams configuration. Also on the horizon was the 1973 US emissions standards which didn't favor (IMHO) the short stroke/large bore engines.

Dennis

bigs

Thanks Dennis. That's pretty much what I had assumed. But then...

The flat 6 of the 911 series works. And also produces solid power for those cars - and obviously falls within emission standards. I presume it must be more of a short stroke/large bore configuration as compared to the 928 engine. However, if that concept works for 911's, would it not also have worked for the 928?

Is there a difference between an engine being water-cooled as opposed to air-cooled that would result in a larger size requirement for a flat 8? (Of course, today's flat 6's are water-cooled.)

I'm just trying to understand what might have swayed Porsche engineers to opt for a V8 instead of the flat configuration they already had so much experience with.

Adrian

Dennis,
The Ford GT (GT40) had a mid mounted engine with the transaxle mounted behind it.
I would be interested to know more of the cars that had the front engine and rear transaxle design. If you find anymore please post them.

As for your question about a clean sheet design. What is a clean sheet design? The 928 V8 used technology and materials developed by others, which applies to all Porsche engines actually.
The actual inventors of the V8 engine, SOHC, DOHC, all-aluminium construction etc etc would all claim their designs are being copied.
Is the 928 V8 a clone of another engine? I really think you need to ask for an honest answer from the original design engineers, but my information suggests that to claim the Porsche V8 as unique or original would not be accurate. I would characterise the Porsche V8 engine not as a copy or clone, but a mixture of the best of the best design elements of the period. A bit American, a bit Japanese, a bit of this and a bit of that all combined together and Porscherised.
However, it is like many other discussions, I cannot provide documentary evidence to support what I have been told.

This is for Bigs,

V angles

The most-common V angle for a V8 by far is 90°. This configuration produces a wide, low engine with optimal firing and vibration characteristics. Since many V6 engines are derived from V8 designs, they often use the 90° angle as well, but with more complex cranks to even the firing cycle.

However, some V8s use different angles. One notable example is the Ford/Yamaha V8 used in the Ford Taurus SHO. It was based on Ford's Duratec V6 and shares that engine's 60° vee angle. This engine is used by Volvo Cars as of 2005.

Cross-plane and flat-plane

There are two classic types of V8s which differ by crankshaft:

* The cross-plane V8 is the typical V8 configuration used in American road cars. Each crank pin (of four) is at a 90° angle from the previous, so that viewed from the end the crankshaft forms a cross. The cross-plane can achieve very good balance but requires heavy counterweights on the crankshaft. This makes the cross-plane V8 a slow-revving engine that cannot speed up or slow down very quickly compared to other designs, because of the greater rotating mass. While the firing of the cross-plane V8 is regular overall, the firing of each bank is not; this leads to the need to connect exhaust pipes between the two banks to design an optimal exhaust system. This complex and encumbering exhaust system has been a major problem for single-seater racing car designers.

* The flat-plane V8 design has crank pins at 180°. They are imperfectly balanced and thus produce severe vibrations unless balance shafts are used. As they don't require counterweights, the crankshaft has less mass and thus inertia, allowing higher RPM and quicker acceleration. The design was popularized in modern racing with the Coventry Climax 1.5 L V8 which evolved from a cross-plane to a flat-plane configuration. Flat-plane V8s on road cars come from Ferrari (the Dino), Lotus (the Esprit V8), and TVR (the Speed Eight). This design is popular in racing engines, the most famous example being the Cosworth DFV.

In, 1992 Audi left the German DTM racing series after a controversy around the crankshaft design of their V8-powered race cars. After using the road car's cross-plane 90°-crankshaft for several years, they switched to a flat-plane 180° version which they claimed was made by "twisting" a stock part. The scrutineers decided that this would stretch the rules too far.

The cross-plane design was neither obvious nor simple to design. For this reason, most early V8 engines, including those from De Dion-Bouton, Peerless, and Cadillac, were flat-plane designs. In 1915, the cross-plane design was proposed at an automotive engineering conference in the United States, but it took another eight years to bring it to production. Cadillac and Peerless (who had hired an ex-Cadillac mathematician for the job) applied for a patent on the cross-plane design simultaneously, and the two agreed to share the idea. Cadillac introduced their "Compensated Crankshaft" V8 in 1923, with the "Equipoised Eight" from Peerless appearing in November of 1924.

One other thing Bigs, Porsche were building flat 8 (Porsche 908) and flat 12 (Porsche 917) racing engines long before they built a V8, but these Porsche engines were totally unsuitable to mount in the front of a car.
Emissions requirements in the USA were a major factor for Porsche going to the V8, as was the decision at the time that the 911 and its flat 6 was dead in the water and would be discontinued and replaced by the 928 totally.

Ciao,
Adrian.

Dennis Wilson

The problem was getting low end torque for the heavier 928. The 911's were lighter and had much less displacement in the early 70's. Also, the cat hadn't been developed yet so emissions were on the mind of all engine designers.

Dennis

Dennis Wilson

Adrian,

By "clean sheet" I mean that an existing drawing/plan wasn't used. i.e. Porsche started a new (clean sheet) on the drawing board. OK let's come right out with it. Did Porsche use the MB V-8 as a prototype?

Dennis

Adrian

Dennis,
That is a question you would have to ask directly and I doubt if you will ever get a direct honest answer. You might have to add a couple other names to your list as well, specifically the Datsun (concept only) and Toyota (racing only) all-aluminium V8s of the late 1960s.
Would it surprise me that a whole bunch of V8s were lying around disassembled and inspected at Weissach as they put pen to paper? Nope! That would be sensible, why try and reinvent the wheel?
Did they steal somebody elses plans? No I don't think so.
Did they purchase or were given stuff? Maybe. Will all be revealed and proven? I doubt it and who really cares?
Ciao,
Adrian.

Adrian

I cannot actually agree with your catalytic converter comments. The 928 had a very long design phase from 1971 to its release in model year 1977. The engine discussions being the biggest problem. Cats may not have existed in 1971, but they were installed on many cars before the 928 was actually produced.
Read up on some Mercedes engine history to get a feel for the dates and times. Mercedes switched to Bosch K-Jetronic in 1975 and starting fitting cats around the same time, maybe even earlier.
If I remember my history properly, the catalytic converter was invented circa 1972 in California and there may have been a US model of a Mercedes Roadster fitted with cats as early as 1973.
The Californian versions of the 911SC were fitted with 2-ways cats for model year 1978.
Ciao,
Adrian.