Anyone done this? Any problems?

I've been feeling like my JCW's boost has been kind of low - I see 13lbs max at wot, and it seems that most cars with pulleys get 15-16lbs, based on what I see here on NAM. I saw recently where someone posted that a car with a better flowing head will likely show less boost even though it's flowing more air and one of the techs at a shop also mentioned that to me today. I know that the JCW head isn't that much improved, but he said that even a small difference could make a noticeable difference in boost level.

SO, I'm thinking that I could jump up (down) to a 17% pulley and make up the difference - get a few more lbs boost and stay in the "normal" range.

Other than the sc spinning faster, would there be any issues with doing this? I wouldn't think so, as it's basically like doing a 15% pulley on a non-JCW, but it doesn't always seem to be that simple with these cars. :impatient

 

I had this very conversation with Dan at GrassRoots Garage today - Dan's a believer in 17% pulleys on JCW cars - I think he's done one or more of these. By the way - I put a caliper on a stock, JCW and 15% pulley today, and I personally know what the reduction percentage is on a JCW pulley. And it ain't 15% (or 14, or 13, or 12)...

 

So....what is it....?

 

hmmmm. Of course, is the reduction a measurement of the diameter or circumference? Eh, either way....

Thanks for the input. Good to know that someone's into it.

 

To open this can of worms - again - 10.4%

Sorry folks. That's the number. I did the math - twice. Then confirmed my math was right by measuring a 15% pulley - which calculated to be 15%.

Feel free to disagree - but post your caliper measurements of your JCW pulley (outside diameter of V ridges).

 

I have an 04 Mini Cooper S JCW car and have the 19% pulley and LOVE it!!!! I love the way the car pulls with the 19%. I also have other mods like injectors and GIAC computer remap, etc.. I know there will always be pros and cons talked about, but I just wanted to let you know my setup and tell you that the difference is awesome!!! Hope that helps.

 

Well, considering that the "extensively reworked head".... isn't, really, and that according to Scott at TX Speedwerks, the "short and stiff" JCW springs are really just.... short (I was told that they measured a 165 rate - same as stock MCS), a 10% reduction pulley seems par. :impatient

So maybe THAT's where my extra lbs of boost are, and I should just get a 15% pulley. If I get the Jesus head down the road - seriously considering it - then I may want the 17%.

 

Having seen JCW cars on dynos and on strips, I don't doubt that at all. 15% cars seem to be at least equal to any JCW car I've seen.

 

So, do you have the old basic JCW kit before the airbox/injectors upgrade? I presume, since you mention injectors as a separate mod.

 

Yes I have the old upgrade, no airbox or injectors upgrade. My car is JCW from the factory, then I added the alta intake, 19% pulley, GIAC, Bosch 380cc injectors, DT bypass valve, WEBB 3" exhaust, alta short shift kit, nology hot wires. My car is running 20 psi of boost. This car pulls!!!!

 

Peak boost doesn't mean much. It's hard to compare from car to car because different modifications will change your peak boost. For instance after installing the new head from RMW I LOST boost. But GAINED power. 17% pulleyed cars experiance issues with blower cavitation and belt breakage. For the 4-5 HP you MAY gain (Really it just overspins the blower and puts out more heat than anything) it's not worth breaking belts once or twice a year to me. To each his own though

 

Couple questions:

1) What is blower cavitation?

2) If a correctly sized, smaller belt is used, why would there be belt issues? The belt isn't travelling any faster because of the pulley.

And to phrase the question differently, for a given flow efficiency, is there any reason not to up the boost a few pounds as long as it's still in the somewhat mild range? I agree with you about a few more horsepower not necessarily being worth extra maintanance issues - my car is a daily driver, and I want it to be relatively trouble-free.

From what was posted above, it sounds like I would likely gain a noticeable (albeit small) bump in boost by just going to a 15% pulley. Since those are commonplace and don't seem to cause any problems, it seems that that might be worthwhile.

Again, I don't necessarily want to be making 20lbs of boost - I don't think our 91 octane gas can take it - but 15-16lbs would be an improvement from where I am now.


Oh, BTW, I was talking with Jan at AMVIV about getting more power out of my car without going nuts (I'm seriously thinking of doing the head swap in the future, though), and I'm planning on taking my car to him sometime in the near future for a GP flash and tuning. When I talk to him about scheduling a time, I'll probably discuss the pulley thing, too.

 

JCW pulley is 14.4% reduction according to Randy Webb ...

https://www.northamericanmotoring.co...2&postcount=15

How about going with an oversized crank pulley instead of changing the supercharger pulley?

 

I have had my setup for over a year and a half now and no belt issues or any other problems. I know this topic has been discussed many times on this website but I am just speaking from experience. My car is a daily driver, not brought onto the track, and I have had no mechanical issues. I am sure if my car was a track car, I would have had some issues already. Just giving my $0.02.

 

Good to hear your experience. Thanks - I appreciate the input. What octane gas are you running? Are you in CA, or someplace with better gas? One of my concerns with a big jump in boost like that would be detonation.

 

This gets me to about the same as if I had put a 17% pulley on my JCW. Been on the car for about a year and a half or so. Good extra boost in power (I still want more of course). No problems whatsoever.

 

I am in Pennsylvania. I am runnig 93 octane all the time.

 

Blower cavitation occurs when the SC impeller spins so fast that turbulance on the tips of the impeller creates a shockwave and disrupts the airflow. When that happens, the SC doesn't push any more CFM's out. Your boost may shoot up 1-2 PSI, but that's from the heat, not from any additional air. More info on Cavitation in general

Belts breaking...People just seem to have issues past 15%. I don't know why. I'd also imagine that the closer the SC is to JCW, which I assume was tested and found to be safe, the longer your SC is going to last.

Generally speaking less boost is better (For engine service life). If you live in a state with 93 octane, you'll be better off than in a state like CA where we can only get 91. Again, I think JCW runs a 12ish% pulley, 3-4% isn't going to hurt anything. 7-8% may .

I was boosting 13-14 PSI before the head, i'd say i'm 1-2 PSI lower after (More free flow = less pressure/boost). I still don't have an official dyno, but if my car performs anywhere near where the other 4-5 cars have, I should be around 220-230 WHP on 91 octane with a pulley, intake, header, exhaust, and head .

Jan from RMW knows his stuff. I use him for everything. To be honest i've never asked him his opinion on the pulley issue, that'd be a great place to start, he knows quite a bit more than I do.

If you're dead set on getting a 17/19%, you'll probably have less issues with belts if you use an oversized crank pulley and a 15% SC pulley. That being said, Jan is against oversized crank pulleys, mostly due to the horrible manufacturing of most of them (Backing off and spiralling out of control in the engine compartment ).

 

I have immense respect for Randy. And before yesterday I believed this to be true. But I measured the old JCW pulley myself. So I'm a little confused. Maybe the old JCW pulley I measured is a one of a kind defective oversized JCW pulley. But it came off a JCW car, and it measures 10.4%. If it isn't one-of-a-kind, then there may be others that measure the same way.

I'd just recommend anyone with a JCW pulley, who is considering a switch, put a caliper on your pulley before you assume what anyone tells you (including me) applies to YOUR pulley. Cause I have seen it with my own eyes.

 

I kind of wonder if the JCW pulleys got smaller at some point. I was shopping for my car at the time that the JCW kit first came out, and in talking to my MA, who was pretty knowledgable about the cars - he owned one, and reading the literature available at the time, it was never mentioned that the JCW had a smaller pulley. The literature said that the kit had a different sc, but nothing about the pulley. Later on, they starrted touting the smaller pulley. I mentioned this to someone not long ago (probably at AMVIV), and they just shook their head and said, "Nah, it's (the JCW) the same blower and it's had a smaller pulley all along. That's where the extra power comes from." I wonder, though, if the early JCW pulleys might not be reduced quite as much as the later JCW pulleys. It's a possibility. But again, it's just a theory.

 

The SC change migrated over to all cars as of 2005 . I think they coated the vanes with ceramic or something. pre 05 cars didn't have this (Unless you got the JCW kit). I'm pretty sure all the kits have a pulley, I know there was a bit of a jump from the older kits to the newer ones, perhaps the old kits were 10% and the new ones are 14?

Everything i've heard said they're pretty damn close to a 15% pulley.

The head they added was more to justify to 5k dollar add on. They would have had a hard time explaining the 6k install to an owner for installing an intake, pulley, and exhaust . Pretty much any head flows better than JCW.

 

10%-14%. Yeah, that's what I'm wondering.

Yep, I wouldn't say that I'm sorry I got the JCW, but knowing what I know now, I'd pass on it and spend the money elsewhere. Probably just get the injectors and airbox, and do the head, pulley and exhaust from the aftermarket. If I do the mods that I'm thinking of, I'm not really going to have a JCW car anymore.

 

I don't knock the JCW kit because for some people it makes sense. I do think it's silly like you said to buy it them make modifications to it (Basically voiding the only reason you got it in the first place, for the warranty).

With 6k you could easily be at 230-240 whp :-).

 

After talking a bit to Danny at MiniCorsa today, they recently did a head on a 19% pulleyed car. He said it pulled great.

After a bit of talking (We didn't get into the belt issue, just cavitation) he seemed to indicate that with a head flowing better, the pulley *shouldn't* cause any issues with cavitation so long as the RPM is kept near stock, and you don't rev the heck out of the motor. I should see Jan in the next few days, so if I get a chance, i'll talk to him about it, Danny said that he thought Jan was Pro 19% now that he's seen one with his head.

He also indicated that he thought it would run slightly cooler because of the additional flow, and a lot of the heat generated occured from a head restriction.

If I get a chance I might try to run one for a few weeks once I get my RPM limiter bumped and see what it does to my torque curve .

 

I spoke with Jan this morning, and he mentioned that car. Said it pulled like crazy, and he's anxious to get some numbers on it to see what it's actually doing. We talked a little bit about pulleys. It seems that maybe a smaller pulley would do better with a higher flowing head because the extra airflow from the sc would have somewhere to go, rather than just shoving up against the intake ports and valves. If you're shoving lots of air, but it has no escape, then you're going to get higher boost. If the head can handle the flow, then shove more air through it. I still don't necessarily want maximum pulley action, though. At least not with a stock/JCW head. I'd really like to find out, definitively, what reduction the JCW pulley is that's on my car. Once I know that, I'd have a better idea of what a 15% or 17% pulley might get me.

I guess Jan's setting up a Dyno day next month, so I'm planning on heading down there for that. I'll see about getting the GP flash and then have him do some tuning on that and see where it gets me for now.