more supercharger talk

[gldgti]

would it help keep from munching the crank snout?(theoretically it should yes?)


-Owen

I like the idea of having it clutched, but it think this is more likely to cause crank nose issues than having the 'charger run all hte time.

reason is, when everyhting is in steady state, there is constant torque applied through the pulley coupling to the crank nose (assuming the engine runs relatively smoothly). Times when you have very large load on the crank nose are when there is changing toqure - particularly the application of toruqe (as opposed to reduction). there is a very large (maximum possible with whatever you are driving) torque applied through each part of the system when the load is accelerated from standstill. Clutched pulleys take up VERY fast - alsmost instantly - so the load of driving the supercharger is applied over a very short period of time.


An analogy i would make would be as if you were turning a large flywheel on a small shaft with your hands, from stopped. if you want to accelerate the flywheel quickly, (or to a high velocity in a short period of time, its the same thing) you would need to grip the shaft very tightly, and even then you may slip. On the other hand, if you accelerate it slowly, you may use less grip strength, and it is less likely to slip. Also, once the flywheel is going the speed you want it to, it takes little effort to keep it going at that speed.


It is forthis reason that on my AAZ, i try not to swithc the a/c on and off too often - either leave it on, or leave it off. also, i usually clutch in before switching the a/c on and off whilst driving, because there will be far less stress on the crank nose if the load is taken up to only 1000rpm so quickly, rather that a 3000rpm cruise.

I hope this makes sense :-)

[sawedoffgolf]

how much is a few bucks?

I looked for one while I was putting the motor together, but everyone wanted far too much money for one.

I can send it to you for $25 shipped.

[Turbinepowered]

I think by "clutched alternator pulley" he means the one-way clutched assemblies used to let the alternator/what have you "overrun" when you suddenly drop engine RPMs, reducing the back and forth shock on the crank nose.

[truckinwagen]

that is precisely what I was referring to, I think the shock load from acceleration would be small, as the supercharger would always be turning at least as fast as the motor.

there would never be a time that it is asked to accelerate the supercharger large RPM values from a stop.
the idea was, like the TDI alternator, to keep the load on the crank noze to one direction, instead of back and forth.

another question.
I have never actually played with a clutched alternator pulley, do you guys think it would be robust enough to take the loads of turning a supercharger?
the alternators load is minimal, I just wonder if if would be too much to ask of the pawls to drive the supercharger?

-Owen

[Turbinepowered]

another question.
I have never actually played with a clutched alternator pulley, do you guys think it would be robust enough to take the loads of turning a supercharger?
the alternators load is minimal, I just wonder if if would be too much to ask of the pawls to drive the supercharger?

Hmmm... good question.

I think I've seen one-way alternator pulleys for alt capacities of 200+ amps... @ 14v that's 2.8Kw, or ~3.8hp. Add in some for the efficiency of the system (75%, say) and you're up to a 5hp load at full charging output, then go from there with margins of safety and fudge factors. Say a minimum of 6hp load rating, probably more like 7-8?

Of course, I don't know what sort of power the supercharger is consuming to be driven...

[arb]

I think I've seen one-way alternator pulleys for alt capacities of 200+ amps... @ 14v that's 2.8Kw, or ~3.8hp. Add in some for the efficiency of the system (75%, say) and you're up to a 5hp load at full charging output, then go from there with margins of safety and fudge factors. Say a minimum of 6hp load rating, probably more like 7-8?

Of course, I don't know what sort of power the supercharger is consuming to be driven...

A 200a alternator is about 2900 watts = about 4 hp

The supercharger takes 10% - 20% of your HP to drive it http://auto.howstuffworks.com/question122.htm

So if it takes you from 100 hp to 140 hp, you'll be looking at 14 - 28 hp used to drive it. That's why they have a HD belt, usually cogged.

[truckinwagen]

the G60 takes remarkably little to spin, even at higher boost.

it uses a serp belt to drive it, and I have a 5 rib on it right not with no issues.

I would doubt if it took more than 10HP to turn it really.

if I can get them for as cheap as I think I can, I might just try it out and report back.

-Owen

[arb]

the G60 takes remarkably little to spin, even at higher boost.

10 hp ?  I guess only a dyno will tell (along with precise fuel consumption) before and after installing the supercharger. 7% parasitic drag would be amazing and surprising:-)

[truckinwagen]

well, at the moment boost is low, so it does not take much(as it is not working hard)

how much power can a 5-rib serp belt transfer?

[arb]

well, at the moment boost is low, so it does not take much(as it is not working hard)

how much power can a 5-rib serp belt transfer?

Very complicated answer... depends on what else it is running and how it is configured http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6V36-4P3M811-1&_user=613487&_coverDate=08%2F31%2F2007&_rdoc=1&_fmt=high&_orig=search&_sort=d&_docanchor=&view=c&_searchStrId=1200388410&_rerunOrigin=google&_acct=C000032038&_version=1&_urlVersion=0&_userid=613487&md5=9cd4e64deb7efc570eb1c2f7904e74ba

[truckinwagen]

darn, I was hoping there would be a simple answer like the "v-belts will transfer about 5HP"

nothing is ever easy.

I am tempted to try it and hope that there was a sizable safety margin worked into the pulley.

[truckinwagen]

probably true, there is very little inertia in the charger itself(oscillating mass is made of magnesium)

and under boost, I suppose the resistance would keep it from over-running pretty well anyway.

now all I need to do is find a smaller pulley for the charger that I can actually afford...

-Owen

[truckinwagen]

I think realistically all of this is going to have to wait until after my taxes come back anyway, I am down to the bottom of the barrel.

hopefully tomorrow I can get the timing moved one tooth so I can start driving it more regularly.

[truckinwagen]

I have one too, but the charger uses a keyway, so...
I was hoping that since the clutched pulley utilizes the treads to attach that it would go in the charger without needing the keyway.

-Owen

[truckinwagen]

well, it looks like the max RPM for a 12mm pump head I was looking at was for 5 cyl pumps, which means that a 4cyl pump should be fine to spin to somewhere in the 6500RPM range

not that I intend to take it that high very often, but it is good to know that there is a margin of safety to work with.

hopefully this afternoon I will get a chance to skip the timing a tooth and install the vw advance spring.

-Owen