Engine Drivetrain 1st Gen Cooper S Most liked posts in thread: 15% vs 17% Pulley

TOO FUNNY! :lol:

 

I hate you. But in a good way.

 

Sorry to drop in late...

one thing to keep in mind is that the efficiency curve of the SC is related to both RPM and pressure ratio. So if you have a head and/or a cam that helps the engine breath better (heck, even a header can drop peak boost because of better breathing), you'll drop the peak boost and regain some of the SC thermal efficiency that is normally lost by going to a reduction pulley on a stock head. Sorry for the long sentance.

I'm also not a big fan of the hard RPM limit interpretation on SCs. You go over that, yes you accelerate wear, but WTF, it's in a good cause! If you figure you're going to have to do your SC sometime, then the difference in SC life isn't so large that you're going to need more than one rebuild in the life of the car, so have at it and have fun! Spin away!

Matt

 

Great thread! Researching and this reminded me that my car is just over 80k miles, so I need to do a compression test before installing a 15% pulley.

 

I started reading into this and it hit exactly the question I was wondering... Still debating on 15% or 17%. Might do what suggested and compromise at 16%.

It was unclear but if you got a tune done, would installing a new pulley throw it off by a lot? I understand with anything you do, a re-tune is always BEST but would I me missing much if I didn't?

 

Yes it will throw the tune off, is it worth adding the pulley and getting a retune? Absolutely! !

15 or 17? It's all about heat, the faster you spin the SC the less efficient it becomes. If your on a stock head and track your car go with the 15. In a track session or a hard long run through the twisties where your keeping the car in the high rpm ranges the additional heat from a 17 will very quickly negate any additional HP that you were enjoying unless you have Meth injection or some way to remove the heat build up... 2 cents

 

ANY engine performance mod that significantly affects air or fuel flow will affect the tune.

 

Here is the best advise you can get. If you are having that much thought about which pulley to buy, 15%,16%, or 17%. Do yourself a favor and just get the 17%, if you get anything less you'll always be wondering what the next size up would have done for you, and always be considering changing it. Just go 17% to start and call it a day.

As for the tune, IF your car has been tuned and you change anything pulley, intake, exhaust etc you should get it retuned. This is why you shouldn't tune your car till your done modifying it.

 

Agreed, but I should still be able to feel the upgrade with the new pulley correct? Even if the car isn't tuned for it correctly? I plan on doing a re-tune after the pulley when ever it be comes available again, but I was just seeing how this would affect me in the mean time.

The car is mainly a daily driver, with some spirited runs. I spend most of my time below 5k rpm, I figured the 17% would benefit me and the occasional redline shouldn't be too damaging right?

 

Yes you don't need a tune to install a pulley, 90% of the pullied cars out there are using the stock ECU tune. I guarantee you'll feel a difference when you install a pulley, it's the most HP for your $$.
I've got pullies in stock when your ready.

 

Thanks for installing the 17% Way! I'm definitely glad I decided to just go for the 17%. Looking forward to the next steps when the time well mostly the money is right.

 

I put a 17% from a JCW pulley, if anyone wants to give it a spin lemme know, I'm in NorCal though. Also car not in top shape in need of a cat (cat is clogged?) new plugs and a tune, but still pulls strong. (plug and tune don't match mods)