Im contemplating upgrading my supercharger to a 16 or 17% and was wondering if i do will i have to get a new tune.

 

nope...
Can run stock tune fine.that is why the pulley is such a popular upgrade.
later when/if you have many more "upgrades', a tune can begin to make sense to pull things together and get a bit more gain by optimizing the computer for the new bits!

 

sweet thanks im going to change supercharger oil soon and figured while i have it off might as well so it then.

 

I replaced my pulley with a 17% reduction one. It definitely made a difference. No tunes needed. My radio provided that (sorry- bad pun). Make sure you replace the belt with a smaller one.

 

Don't forget the required colder plugs. NGK 4285 are perfect.

 

The pulley kit at way motor works I'm ordering comes with pulley belt and colder plugs

 

Tip....get the puller...a universal puller DOES NOT WORK ON A MINI SC PULLEY...IT WILL BREAK IT. The pulley is hot set, and on tight. And the pulley mod is done 99% with the sc mounted....no need to remove it.

 

If you are not mechanically inclined have your mechanic put the kit in , I think my mechanic charged 100 bucks

 

A guy in town here has the pulley puller and said he would give me a hand removing it

I'm pulling supercharger off to change oil just gonna replace pulley cuz I'm there lol

 

I've been a helicopter mechanic for 16 yrs now and have been working on cars since I was about nine yes old shouldn't be an issue

 

If you want to be safe about it, you need bigger injectors and a tune for the bigger injectors. I don't care what people on here say, 15% on the stock injectors is pushing it and anything smaller than a 15% pulley is definitely too much. Look at the math. The stock 300cc injectors flow at an 80% duty cycle on the stock pulley at redline. That's around 9 pounds, depending on elevation, so they are flowing around 240cc. I have a 17% pulley, and at high elevation that makes 13.5psi. At lower elevation you would be in an even worse situation. To support the extra 4.5 pounds of boost, the stock injectors would have to run at more than 100% duty cycle. Lets say about 100cc of flow is used up below 0 psi. That leaves 140cc to push 9 pounds. That means for every pound of boost you run, you need 15.5cc of flow to push each pound. 15.5cc per pound times 13.5 pounds equals 209cc. With the 100cc already used up, that puts you at 309.5cc, or 103% duty cycle. That is not possible. Keep in mind that is at high elevation. You will make more boost at a lower elevation, therefore you will need even more fuel.

Another thing to keep in mind is the nature of fuel injectors. They aren't meant to flow at 100%. You will get a bad spray pattern, which results in an uneven, innefficiant burn. Not to mention it's super hard on your injectors.

Why do you think from the factory, they put 380cc injectors in the JCW? And if I remember right, that is an 11% pulley.

Just some food for thought for you. You wanna be as healthy as possible, you're gonna need larger injectors. Like I said, I don't care who has been running stock injectors on a pulley for however long, I don't trust it. Going lean can cause pre ignition which leads to detonation which makes for one unhappy motorist.

If you never plan on bigger mods, such as a big valve head or a stroker kit or a bigger sc etc... I would get the 380cc JCW injectors and have your mini dealership reflash your ecu with the JCW tune. Just my .02 cent. If you are an A&P and remember stuff from school still, this should all make sense to you

 

This should now get interesting

 

If I'm not mistaken stock injectors are 360 and JCW are 380 I wanna upgrade to larger eventually maybe in the 400 s range and I know I'll need a tune for that for now I'm going to go with the 17% pulley and everyone else even mini dealer say I'll be fine with it my next mod will be intake injectors and a tune

 

The stock MCS injector is 330cc. Many have used 17% pulley with no issues for many years. In theory Michael is correct. But has many have found out they are ok without larger injectors. But I would not be redlining it often either. I would still at minimum IMO get the JCW injectors to be safer especially if you like to redline your MINI.

 

My dealer says that they do not have access to the JCW tune if I got the 380 injectors and the 15% pulley. Just wondering if that was true or they don't know how to do it...plus is it even worth it to get the jcw tune?