Quote:
Originally Posted by rldzhao
I have a question for all the experts: 
How does the additional power (be it +100, 200, or more hp) affect the life, reliability, and driveability of the engine and the drivetrain?
In other words, is it sound to subject engine internals (crank shaft, connecting rods, pistons, etc) designed for much less power and torque and transmission components through significantly higher stress and strain?
Thank you. |
Short answer: It does reduce the effective lifespan of all those components.
BTW: The most vulnerable internal engine part of them all...are the rings.
By bolting a forced induction kit onto an engine (that was originally built to be naturally aspirated), I think (or hope) most consumers understand that the life expectancy of these components is going to be reduced. (even under ideal circumstances)
If the M3 owners don't understand that... then shame on them for being a little too naive.
Now the wear factor of going FI on a naturally aspirated engine isn't proportional. (historically speaking)
The life expectancy of your engine is not going to be reduced by the 50% simply because you increased the horsepower and torque by 50%.
It's not that cut and dry...
BMW engineers build in some safety margins into these internal engine parts, so you may end up reducing the life span by 20% which will still be well over 100,000 miles on the average M3.
Now, these numbers are pure speculation on my part, since no long-term data is actually available to answer this specific question.
I am basing this estimate on what I have seen over the past 15-20 years. (anecdotal evidence)
No good verifiable records are kept on these FI cars, since they usually change hands three or four times before the odometer hits 100k.
That makes it incredibly difficult to know exactly how much the engine's lifespan is actually being reduced. (by going FI)
I
can tell you this much...
The LINEAR power output of a centrifugal supercharger (like the Vortech) will have a less profound effect on the engine internals. (since MAX BOOST is only achieved at rpms levels near redline)
Since the boost is tied to the rpm of the engine with centrifugal superchargers, the S65B40 will spend very little time at maximum boost. (in between shifts) And even then...the boost pressure necessary to make that 50% power increase (in this car) is a drop in the bucket vs. other supercharged cars. (thanks to the efficiency of S65B40 V8 engine and four Double-VANOS camshafts)
Bottom line the engine is not going to implode because of the increased stress on the engine transmission or drive train components in 20,000 if that's what you are worried about.
From what I have seen, the few stress related failures have occurred in BMW cars that were trying to effectively
double the stock hp and torque output of the car. Most of those vehicles were E36 and E46 M3 turbocharged BMW's. (where the power comes on much faster in a more violent and aggressive manner)
Cylinder pressures, stress, and heat builds so quickly inside the engine...that wear is always going to be a concern for turbocharged cars. (much more that it would for a centrifugal supercharged car)
This is assuming both cars have perfectly tuned FI software.
Again, only a naive person thinks they will get exactly the same life out of the engine with a 50% increase in power.
That little 'detail' simply comes with the territory...
That shouldn't scare anyone off going FI, since this has always been the way it works.
In fact,
it's less of an issue now, due to all the engine and forced induction hardware innovations over the past 10 years.
For the record...
Poorly engineered forced induction hardware componants, or poorly executed forced induction software files have destroyed far more engine parts than the 50% increases in power output.
Just my .02