Sorry Wagn, but I disagree .
Sorry Andy I also don't think "a phenomenally low failure rate over thousands of pulley installations and millions of miles" means anything. Stating that a million miles have been driven, but all those miles are at the "front end" of the life expectancy of many cars, means nothing if you want to evaluate the long term effect on the engines. Rather, you need to see the millions of miles at the END of the life expectancy of those cars and compare them to stock cars. Since MINI has only been around for three years, I think you got a LONG wait to determine the true detrimental effects off too much boost.

That brings me to the following. I think all these numbers, (e.g., 15%, 15 +2 % crank pulley, etc) just confuse people because it tells you nothing about what is really going on. Its all about boost.

Just jump to the next post if this is too simple for you all but I need to understand it myself so I think ... simple If I get it wrong, I'm sure somebody will tell me I'm full of BS and thats OK, I'm human and can be wrong

Lets look at this from the engines perspective since the question is about "engine components" wear and nothing else. PLEASE CORRECT ANYTHING I SAY WRONG HERE

The combustion in the "engine" makes the power, NOT the "pulley". No bolt-on makes any power. They can "free up" power but not make any. The pulley merely drives the SC so its actually funny referring to the "pulley". Obviously, MINI decided it needed more HP from its itty bitty 4 banger in stock form. The Quick fix is lower the compression ratio and increase the boost (there STILL ain't no substitute for cubic inches). You can do that by adding a Turbo or adding a Supercharger, different mechanical solutions to the same end ... increasing the boost. Since VERY few cars are supercharged (Thunderbird? MR2, etc.) and MANY turbos abound, you got to wonder why MINI went with a supercharger ... prolly cheaper.

Now consider this ...

After testing, I would bet the MINI engineer picks a safe boost number. Then I suspect the lawyers and accountants got a hold of the numbers and dropped it. After all, MINI has fiscal responsibilties and has to worry about 50000 mile warranties. I am also sure they dont want the engines dying at 70000 miles, right out of warranty because that wouldn't look to good.

So now the engineers have a boost number and they BUILD a corresponding pulley size to drive the SC for the selected boost number. You can be reasonably assured BMW is right on the money or the cars wouldnt be sold. For argument sake, lets assume the MCS is perfectly safe at 14 pounds of boost (I dont care what the real numbers are nor the dimensions of a pulley part)

JCW comes along and says I'm "I need more HP so I'm going to kick up the boost to 15.8 pounds" It WILL be more stress on the pistons but they should last 50K easy. Cool. JCW manufacturs a different size pulley to drive the same SC harder. They also warrant under MINI.

Along now comes aftermarket vendors to jump on the bandwagon. They are in the business, just like MINI and JCW, of making money but dont really need to worry about 50000 mile warranties (except some are warranting for a couple of years now). They sell parts increasing boost from 17 - 21 pounds (in our example).

Clearly, these numbers are out of bounds of what BMW considered safe to warrant albeit the 15% is probably, statistically identical to the JCW.

So, when you say will a pulley "effect" an engine component?? It really means, if I increase the boost from 14 - 17 pounds will I effect the engine???

Of course you will. By definition it has to. Its more wear and tear. The question is ... by how much and over what time and conditions?

You will only know that answer when sufficient data points show at the "END" of the life cycle of the car .... not at the beginning. The cars have been around three years. Thats nothing. Come back with figures in five years with all the dead MINI engines and find the failure rates, if any then. But there is NO WAY you can determine failure rates, or mean time between failures, when not enough elapsed time has expired to get to the point where they do fail. Ancedotal data points mean nothing.

Look at it this way. Since we all have PCs or you wouldn't be using this forum, If you buy a new hard disk and the MTBF is 300,000 hours, I expect it to die, on average, in 300,000 hours ... give or take a bit on the normal curve. If I crank up the rotational speed of the disk (say from 5400 RPM to 7200 RPM), the MTBF will most likely go down ... but by how much? You can't just say "Oh, I've run my disk for 48000 hours and its fine" so what? You need to see a large enough sample of disks running at 300,000 hours, at the end of the life of the disks, to determine the change in failure rates.

Doesn't that make no sense? you can't just take the word of Joe Smoe who says "Oh, I run 19 x 4 and its been fine for 5K miles". Why? Two reasons: its ancedotal data ... one data point (it could be a fluke) and its not a big enough sample size at the END of the life of the car. Since there are so few MINIs at the END of their lives, you have no data to mean anything.

That all said, this is all theoretical anyway.

As to WHY MINI didn't just change there base HP to a higher number by increasing boost, I'm pretty much convinced its soley marketing. You basically have a three model Tier Car Line sold in the US ... MINI Cooper, MINI Cooper S, and JCW MINI Cooper S. Three different prices, three different BHP figures, all in the same model line.
Its all about money. Follow the green ...

 

Chows4us - I'm with you on most of what you said, but I would point out one thing.

You assume more boost equals more effect on the parts. That may not be true. Boost will equal more pressure, but whether that causes an effect or not is not so easy to answer.

Let me explain what I mean. Sometimes things do have a linear relationship. More often the relationship is not linear. An example of a linear relationship might be applying more force to a rubber band. The more force, the more the rubberband stretches. In this case greater force does equal greater effect.

But consider pushing on a glass window. Greater force does not equal greater effect. The difference between five pounds of force and ten pounds of force might not have any affect on the window at all. But get to a certain point and the window will shatter. That's a dynamic effect! It's not linear though.

So back to the boost issue. Is it true that, as you suggest, there is a linear relationship between boost and effect? Or is it possible that there is an insignificant effect difference from, say, ten to twenty pounds of boost, and higher than that a dramatic effect occurs? (I'm just throwing out some numbers for the sake of illustration.)

 

I agree with what you just said 100%. If you look careful, I NEVER said the effect is linear. Rather, I said that would be "some effect". For all we know, the effect could be expontential in which case nothing might happen until, BANG, just like the glass, it breaks. We better hope the effect isn't geometric!

BUT, we will never know until enough cars get enough mileage on them to see. Anything else is just mere guesswork!

 

Your timeline is incorrect. JCW followed aftermarket tuners.

 

whatever ... it has no bearing whatsoever on the discussion (the JCW is Crap thread is here https://www.northamericanmotoring.co...light=JCW+crap)

 

Sure it does. The original post asked " I'm wondering why the MINI engineers made the choices they did. Theories?'

JCW chose to follow the trail blazed by american tuners.

 

OK, I stand corrected, vendors came first. It still moot because the issue being addressed in THAT post is :

"I doubt it [pulleys] makes engine components deteriorate faster."

Go read Wagns thread on Pulley problems for reference.

Since there is not enough data points, its all meaningless

 

Where is the exact information on this? JCW site says work on pulleys in 2002 with intro of mini. Where is your reference?

 

"We started developing the supercharger pulleys in the US before most all of the aftermarket, including the "factory" aftermarket - John Cooper Works" — Randy Webb

 

Typical.

 

It's all the data that is available at this time.

If results change, then (obviously) they change.

Saying otherwise is equivalent to crying wolf, as there's no evidence as of yet. And saying that current data cannot be used is rediculous, because that's all there is to go on at this point. And I'd be willing to bet in 2-3 years, you'd be saying the same thing, if things hadn't changed by then.

 

 

This thread has caused me to do some research:

One issue we have not discussed is RPM. RPM is MUCH more likely to cause engine wear and stress that will shorten the life of engine components than any other cause. Adding boost means you acheive the same result at a lower RPM. You could argue that this suggests a smaller pulley might actually LENGTHEN the life of an engine.

Another thing that has not been mentioned. We are not the first people to put smaller pulleys on cars. I cannot find any evidence on the web of any other cars that people believe have had the long-term reliability of their engines shortened by adding 4-6 lbs. of boost with a smaller pulley.

 

That is exactly what I am saying. Nothing more, nothing less. Glad you agree