Engine Failure Math - Am I Nuts?
 

Thanks Rick3000 for the parts manual,

I didn't have it either. I did find some fascinating information in it though: My 99' had its engine replaced at 8k miles. My Box was made in Finland and has serial number of 25718 (Production VINs skip 10001>20060). There were approximately 17-18k Boxsters produced in 1999; 14934 in Finland. My original engine serial number was 07803 replaced with a 99' engine numbered 24176. The engine numbers, from what I can tell, run serially. If that assumption is correct, there are at least 7k engine purchase/replacements in MY1999. Seems like a very high number but if someone from Porsche could confirm the engine production numbers then this is very telling. This may give an idea of paid-for and warranty engine placements. Of course, this replacement occured in 05/02 so some of those engines may have replaced 2.5L in 97' and 98' cars.

VIN INFO
BOXSTER 99 X 98XS6 00061>10000 M96.20
BOXSTER 99 X 98XU6 00061>10000 M96.20
BOXSTER (USA) (CDN) (MEX) 99 X 98XS6 20061>30000 M96.20 <--- Me
BOXSTER (USA) (CDN) 99 X 98XU6 20061>30000 M96.20
BOXSTER (BR) 99 X 98XS6 29801>30000 M96.20
BOXSTER (BR) 99 X 98XU6 29801>30000 M96.20

Engine INFO
BOXSTER M96.20 99 X 65X 00051>60000 6ZYL/2,5L <--Me x2


Food for thought!

Actually, Porsche produced 47,928 Boxsters between the yrs. '98/'99 (22,063) and '99/'00 (25,865). Porsche list these as cars produced in those calendar years, but does not identify them as model yr. - There were '98 and '99 MY produced in the first number and '99 and '00 MY produced in the second number. Production increased each of the early years so I think your number of '99s produced is maybe 1,500 or so low.

Engine serial numbers have no correlation to chassis VIN numbers. Though they may be sequential (maybe), that doesn't mean that all the replacement engines were of a certain 'run'. For example, of a batch produced, X number may have gone toward production and Y number to replacement inventory. That would mean that the replacment engines would have a hodge-podge of sequencing allowing no conclusion to be drawn. Nor is there any reason to assume the replacement engine were allocated FIFO (First In, First Out) - a 'late' serial numbered replacement engine may have been sent out while earlier numbered engines remained shelved - no way to say for certain. Also, certain #s may have been sent to PNA while others went to Asia for example... or may not have.

So far as engine replacement, there is no single factor here, but I believe the major one to be RMS failure, followed by engine porosity and liner failure (late '98 and early '99) while the rest are simply that portion of accepted mfg. defect.

Most informal surveys tend to support a 25-30% failure rate for RMS, and while that may 'agree' with your supposition, I think it's dangerous to draw any conclusion because Porsche is simply not saying, and likely never will.

I don't know how sound your logic is, but I for one don't think you're nuts. :cheers: