Hi guyz,
Currently my car is on 17% Alta SC pulley, I search crank pulley thread and found out a lot of NAMers did combination of 15%+3% or 19%+3% or 15%+2%, etc. But not much on 17% + 2% :(

Just wondering is 17% +2 % combination alright for the reliability issue of my car?

Anyone got this combination, do you mind to give your opinion on that?
like:
1. performance? (like how much boost it increased?)
2. Reliability issue?
3. other thing you recognise that need to add after 2% crank pulley?


Thank you.
Looking forward to hear you guyz soon.

 

You may not get many awnsers here in this thread because its been beaten to death but ill give you some key points to consider before you get blasted with a inter-forum baslistic search function.

Keep in mind my experience is with a 15% and stock:

With any pulley you increase the speed of the supercharger at all RPMS assuming full throttle.
Per BMW the SC is rated at 100k before its worn out. Its not exact but driving style and other factors play into this as well. More importantly anything past a 17% at stock RPM range or mabye a lil more gets close to redlining the supercharger. Back to the 19% total reduction from what I understand you get alot of boost down low but its not as great up top because you are heating up the charge so much it does not actually translate into higher top end.

This will probably be enough to have some one chime in but to summarize what I read on here and how I understand it.

15% - safe and with other parts/tunning can get you a high performer with reliability
17% - mabye just as popular as 15% but some of the top tuners here rather go 15% due to SC efficiency/heat/less room to bump up the rpm durring tune.
19% - I believe the belt slip issues have been resolved by now and there is a fair amount of people running these. The 19% will give you way more boost down low than any of the other pullies and its linear to a point. But from what i understand if you go above lets say 6k you run the risk of SC problems? Also that 100k BMW rated milage for it using backyard math becomes 80% mabye less I dont know.

My opinion:
Since my car is a work in progress and I do not plan on a pulley intake exh only I went with 15%. I plan on roughly 250whp & as much tq to go with it as I can. I dont think a 19% can get me there reliably. Think heat soak.

OH AND A BIG ALMOST FORGOT!..... INJECTORS you will need to research that too.

 

I'll give you some rough answers....

The 2% crank pulley causes the supercharger to spin 2% faster and move 2% more air. The 17% supercharger pulley causes the supercharger to spin about 20.5% faster (1/.83). Combined, the combination moves about 22.9% more air (1.02/.83), providing 22.9% more boost.

The supercharger spins about 22.9% faster, so it will wear out that much faster too. It's expected lifespan will be about 81.4% (1/1.229) of the stock lifespan. The crank pulley also drives the alternator, so at high RPMs you risk over-spinning the alternator and over-charging the battery. The car's water pump is driven by the two pulleys, too, so at high RPMs you could over-spin the pump. Water can move only so fast through the cooling system--spinning the pump any faster will cause cavitation and damage the cooling system. These issues won't come up under standard driving conditions, but if you drive hard, beware.... The added air in the cylinders will prompt more gas to be added (to maintain the air-fuel ratio), so your fuel economy will go down.

To avoid overspinning the alternator, you could install an alternator pulley that's about 2% undersize from stock. You may want to install colder spark plugs to better dissipate the extra heat produced by the supercharger. Bigger fuel injectors will ensure that enough fuel is supplied at higher RPMs. An ECU tune would be recommended in order to get everything working together properly.

I've learned a lot on this forum, but I'm by no means an expert, so if anyone has something to add or another opinion, please do so!

 

thank silkworm and wilhelmh,

yeah i need to find out what else i should do if i put the oversize crank pulley. I would like the performance.. but reliability of the engine is my first priority, I dun mind to spend on the money to install colder plugs, fuel injectors and ecu to match with the crank pulley.

Thank a lot

Is there anything i should add ?? or any brand of crank pulley that you highly recommended?


Thanks again

 

I run the 17% and the 2% on my car with no problems for the last 12,000 miles.

I did and will continue to change the belt every 6 months but that has more to do with me being **** than anything else.

 

I had a 15% and a 2% crank pulley. The big benefit of the crank pulley is weight savings. I would notice how the Mini got off of the line better with it.

If you are not running near to redline then over spinning doesnt happen. I found that I ran the engine at lower rpm during street driving due to increased low end torque. On the street the extra torque was nice coming out of corners.

The issue that I had was belt slippage on the track. Twice I had the belt break at the track which was both times I went to the track with the 15% and 2% combo. I did many track days with the stock setup with no problems.

What was really annoying was that the whole tensioner assembly broke. Not just the dampner and the spring coming out, but the cast bracket that holds the tensioner wheel broke both times and everything slammed in to the crank pully chewing it up.

I think that the issue is a substandard tensioner assembly that can not properly tension the belt once it has a few miles on it and has streched a bit. Then you add in the extra belt speed and the slighty smaller SC wheel with less surface and it all adds up to a slipping belt.

The tensioner wheels are cheapy two part pressed units with low quality bearings that don't provide even pressure on the belt. There are replacement wheels to address this.

Both times the breakage happend at the end of a long full throttle, near redline run through several gears. Once at Laguna Seca just before the Corkscrew and at Thunderhill a the end of the front straight.

You can hear the casting break at 41 seconds in this video.
http://www.youtube.com/watch?v=IJORAl6xHyY

 

Here is the pile of parts. As you can see the cast bracket snapped. It is a cheap rough casting. The tensioner wheels are cheap pressed steel units that have a groove down the middle and don't support the belt all the way across. The bearings are low quality as are the bolts and fitting so I'm sure they have excessive play. The dampner is weak with poor action and it leaks before long. Nothing here is precision and designed for high speed. Once the belt starts to slip it drags on the wheels and heats up and shreds. Then you lose power, but worst of all you lose the water pump, so you have to stop before the engine overheats and blows the head gasket.

 

2% crank won't hurt anything else operating on that belt. it would be like driving in 5th instead of 6th. more RPM right?
Colder spark plugs won't do anything either. The added supercharger heat has got to be hard to measure when compared to normal compustion temps. Maybe an intercooler mist spray or a different intercooler would be better for that.

 

i see ... thanks mcleonard,

I do not know much about car stuff.. just would like to ask what is dampner? is that part of the suspension>?

 

Colder Sparkplugs help prevent detination. The Mini will pull timing and this prevents that to some extent. 2% on the crank would be more rpms on the supercharger/accessories just like a SC pulley same effect.

 

If you look down to the SC pulley (Search the forums for pics or check the how to section) The part that has the black spring is the tensioner. The Dampner is part of that tensioner and basicly does the same thing a suspensions dampner does. In the pictures of the parts above the dampner is that black rod with a circle on each end.

Oh also there is a vendor or vendors that sell a cable that prevents your crank from getting mangled in the event of belt failure. A cheaply priced peice of mind if you ask me.

 

The tensioner stop is meant to prevent the spring and tensioner wheel from slamming in to the crank wheel. I had a tensioner stop in place the second time this happened. It didn't help since the casting that the spring and tensioner wheel were bolted to broke off.

Before I would go back to the track with a modified pulley setup I would consider installing a replacement dampner and replacement tensioner wheels. There are precision wheels available. They aslo come in 5mm over size to increase tension.

Belt tension is critical and the belt can stretch so you want to replace the belt often and buy the best belt you can get. Also make sure the belt is properly sized. It should be as tight as possible. The second time this happend to me the belt only had a couple of thousand miles.

 

Is that necessary to put the cable ?

silkworm, did u put the cable on urs ?

 

the cable stops the spring from pushing the tensioner wheel in to the crank pulley in the event that the belt breaks, so it is cheap insurance against this damage to the crank pulley, however in my case it didn't help since the tensioner arm broke and everything fell on to the pulley.

 

Just my two cents. The 15+2% is a GREAT combo and it is by far our most popular option for folks right now. Gets the benefit of the added boost and lesser weight on the rotating assembly. Belt wrap is better, etc. etc.

Going to the photo of the damage above, has little to do with ANY pulley selection and far more to do with the OEM part failure (regardless of pulley selection.) I agree whole heartedly that the benefits of the tensioner holster to keep it from damaging the crank pulley is a very good choice!

Again just my two cents!

 

Hi adam,
Thanks for the suggestion.
Currently my car is fitted with 17% supercharge pulley, so if can i would avoid buying another 15% supercharge pulley.

Adam,
do u think 17% plus 2 % is good ? in the sense that reliability issue and performance but mainly in reliability issue. I was thinking of getting the 2% from Alta. So i just want to heard you as specialist in mini advice..

Thanks

 

Thank you! I missed that you had the 17% already. If you have that, then to get the extra benefit of the lighterweight crank pulley, then just get the 0% ALTA crank Pulley. This will give you the same net results as the 15+2%. The only difference is you will have the same belt wrap as you have now. But from a monetary and PITA standpoint it is far easier to replace the crank pulley than BOTH the crank pulley and S/C pulley.

I would shy away from the 17+2%. Too much and a sacrifice to reliability.

Thanks again for asking!

 

Ah... ok ok .. thanks adam.

I think i browse the items in alta website and will place order with the items i want included the crank pulley.
Because i from Australia so is it better to order all in one instead by one by one .. :D

Thanks again adam

 

No problem! Thank you for the business!

It is LESS expensive to ship items in one package than several little packages over time. Just let me or my staff know what works best for you and we will get you a competitive quote!

Thanks again!

 

I am an aggressive driver and i like to rev high. I've had no problems with a 17% for over two years, but now my belt snapped causing damage to the crank pulley, and i bought a 2% crank pulley. Does that mean I can't redline reliably anymore? :(:(

I also live in australia, and the local ALTA resaler said ALTA don't sell a 0% lightweight crank pulley???

 

+1

 

I haven't seen evidence for the actual effects of running a 2% crank pulley, and spinning the supercharger faster, only speculation. It will only be spinning faster than the previous upper limit at redline. Can you really sustain redline for long on the street? I doubt that bursts to redline will hurt anything, even down a straight on the track you are only at redline for a few moments. When I had a 2% pulley I drove at lower rpms on average since the engine had better low end torque. The alternator limits over charging of the battery and batteries can handle a bit of overcharging anyway. The problem with overspinning the alternator dates back to before modern electronics. As far as cavitation and overheating I would be surprised if that occured with the 20% or so over spinning that would happen at redline. Cavitation if it occurs will lead to reduced cooling, not to an explosion or anything like that. So watch the temp gage since obviously overheating would eventually cause problems.

 

I've started to notice higher coolant running temprature immediately after installing my 17%!!!!

 

Further to the discussion taking place...

I currently have a 3% crank pulley installed + the 5% reduction pulley on the alternator.

I am thinking of returning the crank to a 0% lightened pulley, and adding a 17% sc pulley.

Is there any problems with leaving the 5% reduction alternator pulley on? Or schould that also be returned to stock?

Cheers

Roland

 

Thanks for the answer McLeonard, sets my mind at ease...

Hey auscoops, i was just reading your post about 3% pulley on mini-mods

Which size SC pulley are you running?