...is this like changing the oil without changing the filter?

Here's what I'm getting at: I've read the threads about upgrading the sc pulley with and without the crank pulley upgrade (it seems about half do both and the other half only upgrade the sc pulley) - don't think anyone has just upgraded the crank pulley and kept the stock sc pulley. Here's what I am really trying to wrap my brain around:

1) is the reason to upgrade the crank (say to 2%) when upgrading say to a 15% sc pulley more about power to alternator and electrical components rather than additonal boost/power/ooomph with the sc upgrade?
2) upgrading sc pulley without crank - does it really affect anything? is your alternator gonna die sooner? last longer? more battery drain?
3) is it more a weight issue then boost or electrical (aftrmkt crank <1lb vs oem almost 6lbs)?
4) finally, regardless of what decision one makes about upgrading the crank when upgrading the sc pulley - does it make any sense to upgrade the sc pulley if you're not also going to replace the plugs/wires and re-tune the ecu (in the case of an MCS with full exhaust and CAI)? Sorta like gross power is to sc pulley alone as fine tuned power is to sc pulley and ecu tune????

 

The SC pulley does not interact with the crank pulley very much. If you were to slow down the belt with a crank pulley, you would only be slowing the SC by about 2% - hardly a big deal.

There is really no good reason to change the crank pulley, and at least one reason not to do so. The 2% reduced drag from the alternator, etc. is only noticeable when revving the engine in neutral. It will not make the car go noticeably faster, and will underdrive the electrical components unless you spend more time at higher RPMs and perhaps set your idle RPM higher during an ECU tune.

Controversial issue: The reason not to use a smaller crank pulley is that none of the aftermarket crank pulleys have a vibration damping core, and the lack thereof could damage the engine. (You will hear a lot of people say it doesn't, but BMW put a damper in there for sound engineering reasons).

Yes - a 15% pulley makes sense, and you can do it without requiring an ECU tune, but it is a good idea to change the plugs at the same time. You can get more power when you do a tune later.

The main difference you will get from a pulley alone is to lower the power-band to a more usable range.

 

Except %2 in this case seems to refer to an overdrive crank pulley, which would spin other components faster.

In any event the first paragraph still applies just in an opposite fashion, so now you might be messing stuff up by over spinning it times.

So, i'll go through and add my 2c.

1)As rick said, you can swap the crank or the SC pulley in any way you want without having to make serious changes. By this I mean, you could go ahead and +2% crank pulley and not really have to worry about the alternator, AC compressor or SC and then be done with it. Likewise you can slap a -15% SC pulley on there and do only that and not have to worry about anything.

2)See number 1. In theory put on a smaller supercharger pulley results in overspinning the SC when you start to near redline, which in turn would shorten its life. However for the last two years I have spent on NAM I havent seen any sort of trend showing a smaller pulley causes early SC failure, it's really not something wirth worrying over as your waterpump will likely eat its internals first (which it would have done stock).

3) If you get a crank pulley thats the same size as OEM it is entirly a weight thing, its a little bit like adding a lightweight flywheel in the regard.

4) Colder plugs arent a bad idea, but you dont have to get them. The same thing absically applies to a tune, except here getting a tune could net you anywhere from 3-20 HP among other things.

 

Um, I think that people generally use an UNDERdrive crank pulley, to reduce the load on the engine, not an OVERdrive pulley, which would increase the parasitic load...

 

Well, actually most crank pulleys are overdrive (2%) which do spin the SC faster, to give a 15% pulley an *almost* 17% effective increase in SC speed.

I've never heard of anyone putting an underdrive crank pulley on, but I stand to be corrected.

 

The enthusiasts for every other car I've ever seen use Underdrive pulleys, to reduce load from the alternator, A/C, and water pump.
http://www.unorthodoxracing.com/prod...y&CATEGORYID=2 - and -
http://www.marchperf.com/underdrive2.html

I must confess to being amazed the one would use an overdrive crank pulley on a MINI to do something that a smaller SC pulley would do just as well, without increasing the power lost to the alternator, and at no additional cost.

Seems to me that's going the wrong direction.

Also, as a price-performer, a 2% overdrive pulley would be a poor choice. It seems to be the consensus that a 15% SC pulley will yield about 12HP (with a tune). A 2% faster crank pulley would cost about the same $ as a SC pulley, require about the same amount of shop-hours, and get you maybe 1.5HP, which is probably not reliably measurable, and certainly not noticeable on the butt-dyno.

If you have to have that extra 1.5, use a 17% pulley, at the cost of high-end power when the SC is running beyond it's most efficient speed, and accelerating belt wear.

 

so it's really sounding like this topic is so controversial (this thread, previous threads on the topic, etc) whereas there's fairly good understanding and acceptance of what not only a smaller sc pulley does, but what can be achieved (positive and negative) with the various sizes.

i guess at this point it's safe to that if you're just upgrading to a 15% reduction sc pulley without other significant changes to the motor, then the most sufficient (if any) upgrade at all to the crank pulley would be to a lighter weight aftermarket 0% pulley. but, honestly if you're looking to save weight with a mod like that, then you're overall goal - either in one big step or multiple steps over time -should be to reduce weight everywhere (lighter flywheel, rear seat delete, lighter wheels, lighter crank, etc etc). unless your lighter crank balances out an aftermarket addition that added weight to the car.

thanks for the posts old rick, dr phil, some guy...

 

My .02

Having 2 2005 MCS I can give you some butt dyno comparisons between the stages our cars are at. As well as some practical input on how "bad" an overdriven crank pulley can be to say your alternator. I will also chime in on harmonically balanced stock crank pulleys which are cast and lightweight crank pulleys which are almost all cnc machined billet. And why not throw in some metallurgy.

Butt dyno info:

Wife's car m7 16% sc, alta 0% crank, m7 intake, invidia exhaust
My car m7 16% sc, 2% crank, homemade version of m7 intake, stock exhaust

My car is quicker than hers because my supercharger spools up quicker with the overdriven crank pulley. Hers is faster top end because of 2 things. First exhaust (I suffer from more restrictive back pressure), second her sc can still create boost at higher rpms where my sc is spinning above max effectiveness (losing power to excess heat from higher boost levels)

As to a 2% overdriven crank pulley being bad for your alternator/electrics:
The windings in your alternator can vary by up to 5% efficiency in manufacturing.

Balanced stock crank pulleys are cast which is why they have to be balanced to compensate for inconsistency of the casting. Not an issue with billet cnc machined parts.

sc pulley selection out there is pretty varied in material. The Crank doesn't have large swings in temp thanks to the oil keeping the crank temp fairly constant. The sc does not have that luxury. steel and aluminum expand/contract at different rates the sc shaft is steel, an aluminum sc pulley can slip.

I've seen it so nobody go off because it hasn't happened to you.

 

that's interesting - i would think that her car having the full exhaust would allow it to breathe better on both the low and high end (especially given the same sc upgrade and both having CAIs). realistically, her exhaust should be good for 5-12hp, whereas the 2% crank pulley should be may 1hp. so, without putting this thread in jeopardy of dragracing violations (i don't even want to get into another spat with moderators again ) please elaborate on how you've arrived at your butt dyno results of your's and your wife's mcs - in other words, tell me that on some "sanctioned" strip you both drove each car side by side 0-60 etc

 

Actually, the stock pulley is stamped, not cast, and the reason for the harmonic damping core has nothing to do with balancing the pulley anyway. The purpose of the damper is to isolate the crankshaft from the pulsating drag and harmonic amplification at certain frequencies, created by the alternator, A/C and water pump. If the pulley was not damped, it could set up resonances in the engine which can damage it in the long run.

Reference the following article on the topic of aftermarket crankshaft pulleys at Dinan, which asserts: "This is a very dangerous product because this damper is essential to the longevity of an engine."

I'm willing to believe that the Steve Dinan knows a lot more about the topic than the vendors and distributors who sell crankshaft pulleys, or those who defend the product because they bought one...

My mentioning this will now generate a whole series of outraged posts from the same people who went off on me with threatening PMs the last time. Just to prime the pump, another quote from Dinan: "It is also important to understand that while the engine in a BMW is designed by a team of qualified engineers, these power pulleys are created and installed by people who do not understand some very important principles of physics."

 

The above post is so horribly ignorant and laden with speculation I want to throw up. This community is harmed by such propaganda.

OldRick will certainly never acknowledge that many Honda 4 cylinder engine do not use an external crankshaft damper, nor will he acknowledge that Dinan has rooted their article in the inherent weaknesses of cross-plane V-8 and inline-6 engine crankshafts, not extremely short inline-4 crankshafts. He is willing to put his trust in a company that fails to provide useful aftermarket products with any signifiacant gain, and yet he is unwilling to listen to the very people that personally know the chief engineer of the Tritec engine and listen to the breadth of experience far beyond his narrow and untrained perspective.

The reason OldRick gets the technical community of NAM so enraged is because he fails to understand his assertions are based in faith, not math, experiments, or data.


To the OP:
Changing the supercharger pulley changes its ratio, and thus it's displacement per engine RPM. Most supercharger pullies for the MINI are in the 15% to 19% size reduction range. This smaller size increases the overdrive of the supercharger, making it spin faster for a given engine speed. This offers greater airflow, more boost pressure, and more power. Some opt to compound this ratio by adding a larger crankshaft pulley. Changing the crankshaft pulley is a wholly separate decision, which as you've seen is wildly blown out of proportion by OldRick.

The crankshaft pulley is a multipiece assembly that acts as a minimal damper in quenching some leftover noise/vibration/harshness that engine mounts and insulation didn't take care of. MINI used several different crank pulleys over the years. 2002-2004 Cooper S's used a medium weight damper that had lots of reliabilty issues, so in 2005-2006 the Cooper S used a lighter weight pulley that improved engine revving response while bringing reliability back and keeping NVH in check. The Cooper uses a light weight damper pulley also of a different design to fit the Cooper serpentine belt system.

All aftermarket crank pulleys are un-damped, or "solid". This means they offer no NVH damping. By nature, they're also very lightweight, and offer very quick rev response, at the expense of some NVH transmitted around the car. The engine isn't creating any more vibration, its just that you'll feel more of it.

There are a few out there, like OldRick, that claim an un-damped pulley will cause all sorts of mayhem and death & destruction. Yet, they will be unable to provide any proof of this, only your hand in faith. There is a possibility an un-damped pulley may minutely shorten the life of the oil pump or valvetrain, but this also makes assumptions regariding your flywheel/clutch setup as well as full-load long-term operating speeds below about 1500 RPM, where engine resonance occurs and also firing pulses become relatively far apart, creating transients in the accessory and timing chain. A possibility, but not definite or even confirmed, even with MINI's now working on 7 years old.

If you're new to MINI modding and aren't sure how deep you want to get, opt for a 15% supercharger pulley with a shorter NAPA 060535 belt and Brisk BR14YS spark plugs [which are a colder heat range than stock, which adapts for the greater power] and you'll be golden. There's no need to worry about engine management, as the ECU uses MAP, which by nature adapts to higher boost pressures. No ECU tune or other hardware is required. Other hardware, like exhaust/intake/cams/porting will help power, as will an ECU tune, but none are needed to make a supercharger ratio change effective.

 

As expected, Ryephile, who sent me physical threats via PM last time, is the first to chime in.

He, of course, is a vendor of these products and has yet to cite any credible evidence that the physics of a 4-cylinder engine is different in kind, rather than in degree.

Believe whom you wish. I have no interest in responding to him again, and if he sends threats again, I'm hopeful that the new management will respond.

Oh yeah, and I have never heard from any other "enraged" members of the "technical community".

 

I'm a vendor? You're about 4 years behind the times. Cars are just my hobby. My only agenda here is to dispel the BS and push the performance envelope forward with clear logical thought, not faith-based propaganda. Faith is fine for personal life, but it is obviously too emotional for those not educated in automotive systems.

 

BMW is a company who must protect themselves from damages and still make a buck at the same time. This is why I believe they went with a harmonic balancer on the engine in the first place. They want to make sure they aren't having to replace engines in cars. These are the same people that also say the Eaton supercharger is only good for 100K miles, but we all know that Eaton themselves says it can go longer. I've gone a little over 22K miles on my car with a 15% reduction s/c pulley and a 2% oversized crank pulley with no problems. I think I would go with what the original designers of the engine say, versus what BMW says. After all, BMW wasn't too happy with this engine originally anyway. As a diesel engine mechanic/generator maintenance guy for the Air Force, I've seen some crazy engine designs in my time. Some of the generators we use have John Deere turbo charged 4 cylinder engines on them. Guess what?? No dampening on the crankshaft pulley. These things are highly reliable and with the load stresses placed on them, we've never had any engines go out. So, for the OP's question, no you don't have to have both pulleys on there. It's just a matter of choice. Just let it be known that there are guys on here running 17% s/c pulleys and 2% oversized crank pulleys with no problems what so ever, if that eases your mind any.

 

I might even agree with this, if there was any evidence whatsoever that the Tritec development TEAM (not an individual) agreed with you. So far, to my knowledge, no-one on the forum has ever presented anything aside from fourth-hand verbal hearsay that this is correct, and we all know how accurate that is.

The fact that some 4-cylinder engines do not come with a damper is totally meaningless, and says nothing about our engines. The statements by some owners that "My engine hasn't blown up yet," are equally meaningless and prove nothing.

It's worth noting that the 3-piece OEM damped pulley carries higher manufacturing costs than the aftermarket single-piece versions, and BMW would not have spent more on this unless they were pretty sure that it would pay off in fewer engine repairs.

I guess that other aftermarket vendors don't have to protect themselves against engine damage repairs, because they don't warrantee their pulleys against anything.

Dinan, by contrast, does actual research by actual engineers, and warrantees their products against causing damage to the car for the life of the original BMW warantee.

Go with what moves you - I prefer evidence and physics to unsupported opinions...

 

this is quite possibly the worse thread that i've seen on NAM. OP didn't have enough basic understanding of the workings of an engine to ask a question that could be answered. downhill from there....

 

i'm a firm believer in all opinions being openly discussed and fairly presented . i can't stand sitting and listening to a bleeding heart liberal talk about the war or p[olicys or whatever but in america it's his or her right. this last part is very dear to the heart . no one should be threatened for voicing their opinion in this country . if so maybe russias not so bad .

 

i would have to say that mach's question was a good one. i am in the process of rebuilding my engine and had almost the exact same question he had. although he does not sound like an engine designer, he basically had the same question that many other enthusiasts may have or have had. which when you search for things like this, albeit via google, or whatever, it may bring you here and help one determine which route they want to go. after all, that is the point of a forum, to bring other enthusiasts together and hopefully maturely discuss topics such as this. my guess is this has been covered a couple times now, saved in the archives of nam somewhere, but i would have to say, this post was essentially exactly what i was looking for to assist with questions i have with my engine rebuild.

i was actually thinking about going with an oversized crank pulley since i've already got it stripped down to the block and am boring it out and getting new pistons and so on.

but, after reading through the input on this page (which took some disappointing sifting, but you'll have that) it seems as if one would only do the crank pulley upgrade to squeeze the most out of what they've currently got. or to make those crazy HP numbers you see on some of the setups around here.

i have a 03 mcs and the following statement peaked my curiosity:

Quote:

Originally Posted by Ryephile

2002-2004 Cooper S's used a medium weight damper that had lots of reliability issues, so in 2005-2006 the Cooper S used a lighter weight pulley that improved engine revving response while bringing reliability back and keeping NVH in check.

i'm tempted to ask if this means it would make sense for me to get the 05-06 pulley for my car since i've got the original pulley off already for the rebuild. but to avoid any flare-ups, i may just PM some folks and get their take on it.

i think i've already convinced myself, that the upgrade does not bring enough hp for me to really need it. i'll shoot for a ported/polished head with oversized valves to help smoke the rubber off the tires

again, i think this was a great post by mach, since it was almost exactly what i was wondering as well. as always, thanks for the input guys!

 

If Steve Dinan knew so much about Mini products he should be aware that the Mini engine is not built by BMW. Just a tip there

Randy
M7 Tuning

 

The differences between the "newer" post-facelift mini crank pulley and the "older style" was mainly weight
02-05 = 7.2 lbs
05 onwards = 5.5 lbs

The MINI part number for the crank pulley is 11-23-7-514-461


Lightened (oversized) crank pulleys in themselves don't add much hp when compared to reduced sized S/C pulleys. I got a 8hp gain from a 2% crank pulley. However the main area in which you see a difference is that you get the added benefit of quicker spool up (similar to lightweight flywheel but less extreme).
Any discussion about crank pulleys seems to go down hill.... as for them causing problems and the whole harmonic balancer debate there are so many cars out there running lightweight crank pulleys with high milage on them.... where are all the blown up cars????
I run a 16%+2% on my car and like it but each to their own

 

nice! thanks d-man!

 

I think that it's been 4 years now whether the light oversized crank pulley is harmful to the engine but i have yet to hear who suffered one. It's a myth. I think that 15% pulley +2% crank is better than 17% pulley alone.

 

So, let's see, that would imply that you got 60HP from your 15% pulley, to go with it. (15%/2% = 7.5 x 8HP = 60HP) I don't think so.

 

When someone shows me ONE MINI Tritec engine that failed as a direct result of running without a harmonic damper and no other factors I'll believe it. If its my motor that goes first I'll be the first to tell everyone I was wrong (after Old Rick that is).

 

Ahh yes...the annual undamped crank pulley debate.

Must be getting towards spring when all the goats start feeling their oats again. Soon the Swallows shall return to Capistrano, bears will emerge from dens and wild flowers will grace our highway beatification projects. That is unless Punxsutawney Phil prognosticates an shorted winter we have 6 more weeks of this terribly tumultuous tiff.