History - 917 "genes" in the 914 2.0L, The Porsche Racing Dept Engineering input Options

[Tom_T]

UPDATED 12/21/09 & (IMG:style_emoticons/default/santa_smiley.gif) to all!

While the 917 is not strictly 914, it is historical info from the period & definitely original info. from the factory & race drivers of the day. And the pay-off for the link after this "shameless hook", is the info in the thread of how an Engineer from the Porsche Racing Department was able to make the lowly VW 1.7L 4 banger into a respectable "Porsche-bred" 90-100 hp 2L engine - when VW thought it was impossible to go any bigger & had been max'ed out at 1.8L (+/- 200% - recall it started in the 1930's VW as only about 900 cc).

See the videos at the link below, & also peruse the additional clips at the sidebar after viewing this one linked below, including those linking to racing 914/6's.....

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If you like racing and the sounds of Porsches, you will love this video:


YouTube - Porsche 917
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Enjoy! Courtesy of our local PCA-OCR membership chair! (IMG:style_emoticons/default/biggrin.gif)

Then read the lively discussion on the link between the 917 & 914-2.0 engines, of which even the "Master of 914 O&H" was not aware! (IMG:style_emoticons/default/biggrin.gif)

...Heck! - even I'm learning stuff I didn't know from others of you out there, which I always do! (IMG:style_emoticons/default/biggrin.gif)

[eitnurg]

Undoubtedly different, but not the reason. A boxer has a seperate crankshaft throw for each cylinder, so each pair of opposed opposed pistons are at TDC and then BDC etc simultaneously, like clapping hands. An inherently well-balanced design. A vee has a common crankshaft throw per pair of cylinders, which at 180° are directly opposed, so when one is at TDC its counterpart is at BDC. Not well balanced at all, but it does gain a shorter crankshaft, useful if dimensions have to be kept tight.

[Tom_T]

Undoubtedly different, but not the reason. A boxer has a seperate crankshaft throw for each cylinder, so each pair of opposed opposed pistons are at TDC and then BDC etc simultaneously, like clapping hands. An inherently well-balanced design. A vee has a common crankshaft throw per pair of cylinders, which at 180° are directly opposed, so when one is at TDC its counterpart is at BDC. Not well balanced at all, but it does gain a shorter crankshaft, useful if dimensions have to be kept tight.

An important feature to be inherently balanced in a 4-6 cyl engine when opposed, less so a problem with more cyls. to balance things out overall in 8, 10, 12, 14 & 16 cly racing engines - not to mention that racers are more forgiving of vibration than in a passenger/street car for general consumption.

The "180 vee" would allow for more cyls. to be crammed in a particular crankshaft & case length as you noted.

So Mezger's thinking on approaching the engine design on both this 917 racer, & on boring & stroking the H-4 914-2.0 were similar, in that he had to squeeze crankshaft modifications in to accomplish the increased displacement in both cases - if applied in the 90 degree opposite axis in each case (per the quote which TC posted above).

From an engine engineering perspective, is this approach of Mezger's similar to what folks like Raby, FAT Performance, etc. are doing to gain stroke & displacement in the up-built Type IV's, or are they doing it purely based on increasing the bore? (IMG:style_emoticons/default/confused24.gif)

In either case, it's important to note that Mezger opened up a whole new era of expanding upon the H-4 engine's displacement & performance by applying Porsche's racing technology to the lowly VW 4-banger!

IMHO the better materials in bearings, etc. & smaller crank created a smoother & more reliable engine as well, since the 2.0's tend to last longer between overhauls than do/did the 1.7/1.8 "standard" type IVs.

I got about 150k out of my 73 2L & could've eked another 20-50k out of it (according to my mechanic Hans), whereas all my buddies with 1.7's back in the day would be rebuilding at 100-120k, as my mechanic Hans always reminded me over the years.

I think it was also due to the fact that the little HP & Torque increase of the 2.0 over the 1.7 made it so that you didn't have to work the engine quite so hard to drive it like a Porsche.