the 924 ran on this highball of fuel called M15, industry parlance that means nothing more exotic than a mixture of 15% denatured Methanol stirred in with 85% premium or regular gas. engineers in Zuffenhausen, always ready for a good challenge, began with an emphasis on the research and development of alcoholic fuels including the biological alternatives using beetroot, cereals, and sugar cane, but it was Methanol they fancied paying attention to most.
that year, the 924's 2,0 liter lump was laid out and configured to perform on this M15 by bumping up the compression ratio from 9,3:1 to 12,5:1, ECU maps were restructured, and the entire fuel system was gone through and stripped of any plastic componentry. the results were convincing; a bit more power (around 130hp), reduced emissions, and more economical but the participant behind the wheel couldn't be passive simply humming along to Udo Jürgens flowing from the Blaupunkt Köln, no; if he/she/it wanted to be green and switch the engine adjustment to run on the alcohol mix, they had to do it manually.
Porsche's advances in electronic engine management systems made it possible for the engine to calibrate itself since the air, fuel, and timing maps could compensate for use of either fuel when the manual switch was made. another concern was the limited amount of stations available that could supply M15 in the Federal Republic of Germany and other European countries. this meant that the engines had to accommodate not only M15, but regular and premium gas...keep in mind this is 36 years ago.
nevertheless, the tests conducted on the ten 924s were very successful; so much so that they totaled 650,000km with most of those piled on using M15. not surprisingly, three of them were still running as of 1986 each having covered 100,000km but mostly topped up with gas.
in true Porsche fashion, an evolution from the original must occur, this is where the 944 came in. when the test program with M15 came to an end in '82, a new one came into focus using M100 and what better way to start anew than with Porsche's fresh 2,5 liter in the 944?
like the 924, the entire fuel system needed a going-through replacing every plastic piece in the process since plastic does not play well with Methanol. compression ratios, combustion chamber shapes, ignition timing, and air/fuel ratios needed to adapt.
breaking these variables down, Porsche decided on an 11,3:1 compression ratio for the 2,5 liter, the squish areas including squish heights in the combustion chamber jibed with the configuration of the production engine, engine maps were bench tested tuning the ignition timing to ensure knock-free combustion, and air/fuel ratios were dialed in to ensure optimal lean mixture operation throughout a large range of the engine maps. so far so good, now for the leap in evolution from single-celled amoebas to a tadpole—automatic detection in fuel changes.
this simple but complex method of detecting one fuel from the next by their optical refraction meant that a dual-fuel engine would indeed be possible to perform in everyday conditions in an economical manner. there were, however, some things that needed to be addressed should this technology be pursued in the future. one would be increasing the resistance of the components in the fuel system, namely the fuel pump and fuel filter, cold starting below -15° C was another, that the driver must completely empty the tank when switching from Methanol to gas was an inconvenience that needed to be eliminated, and lastly; the sensor's inability to distinguish Methanol and gas when mixed together in the tank.
Porsche sought to address these issues, namely for the sensor to smarten up and allow a mixture of both fuels while still being able to transmit the differences to the ECU and configure the engine parameters to burn any kind of fuel mixtures with the utmost in efficiency. were all of these complexities worth refining to such a degree? judging by the increase in horsepower (Pe) and torque (Md) when studying the graph below, along with a decrease of emissions, one would have to say yes...and wouldn't it be marvelous for the internal combustion engine to soldier on giving us the aural delight we've come to expect from Porsche rather than the impotent hum of electricity?
immediately following the graph below, you'll find the information contained in the owner's manual for the Methanol 924 on its function, componentry, and specifications. many thanks must go out to Mike van der Weerd for graciously donating select pages of this manual that gives us an idea of what this special 924 was about.
Thanks ever so much Mike!
should you have any interest in acquiring this piece of history, please contact him:
sources: International Symposium on Alcohol Fuels Paris 20/23 1986, Gruden, D., Höchsmann, G. "Betriebsverhalten des Thermodynamisch optimierten Porsche (TOP) - Motors 924 bei Betrieb mit M15 Kraftstoff MTZ, 42, (1981), 4, http://sweinf.com, http://gasfreeearth.com
Messrs. Porsche is involved in the research project "alternative energies for road traffic," which is funded by the Federal Ministry for Research and Technology.
Have you decided to take an active part in this project after you have verified the technical deviations from the standard specifications of the vehicle and the test participation on the part of SNV (Study Group transport) any conditions.
Should any unforeseen technical problems on your vehicle, please, it is preferable that you consult your dealer.
A note on the specifics of your methanol vehicle is the guiding principle at every visit to the workshop. If anything is unclear, please, notify the VKG department to contact our customer service.
The supplement to the operating manual for your vehicle contains important information about the fully electronic ignition (VSZ). with which your vehicle is equipped. Please read the Supplement to the Manual before driving and ensure that it be read carefully.