Hi,
Been lurking for a while.

Got my Mini in March, changed the oil/filter, cabin air filter, new spark plugs, did a bunch of upgrades - aluminum coolant tank, engine air filter, tower strut brace with anti-mushroom plates, coilovers, and probably a few things I'm forgetting.

The car had 50k miles when I got it, about 52k now. Loving the car but now that I've had it a little while, I think I'm not getting the full JCW experience.

I haven't flushed brake fluid or coolant. I haven't changed the belt or tensioner, but I have the belt and the tool.

I have a little bluetooth module that connects to the OBDII port. It has a feature where it will time your 0-60 run. It starts when you press the gas pedal and I can watch the speedo to see that it stops at 60mph.

The best I've gotten, with DSC off, is 7.8 seconds. This is horribly slow since car magazines put the regular R50 at 7.7 seconds 0-60! Typically I just get about 8.2-8.3 seconds (flat road, no traffic, 80 degrees out, dry, not breaking any laws). It can't be driving skill because I was able to get 4.8 sec 0-60 in my Pontiac, which is what the car magazines said it gets. I learned to drive on a stick in the 80s, I ride motorcycles, so maybe a little is me but not THAT much different. I expect about 6.8 seconds on a JCW.

I don't care what you think about 0-60 times or if they're important. That's not the issue here. I'm not obsessing over comparisons or trying to get to 5.5 seconds or anything like that, I just think there's something wrong with my Mini because it seems to be slower than it should be.

Data: the tensioner has 1 hole showing about 2/3. That is, the hole is obscured about 1/3. Does this mean the belt is loose? Or does it mean the tensioner is inadequate/broken? Or both? If I'm doing the belt, I'll just do the tensioner if I need to, but I won't spend the $100 if I don't have to. What's normal? Should I just do the tensioner regardless?

Anecdote: my father-in-law has an '06 JCW R53 with 100k miles on it, and he says my supercharger whine is WAY louder than his, enough that he said I should get it checked out. I figured it was maybe because the convertible is just louder than the hatch. Afterwards, I pinned open the butterfly in the airbox for even more whine

He also said his Mini pushes him back when he accelerates, and mine definitely does not. My Pontiac is a different beast - a V8 - and that definitely pushes you back for a good while, so I know the feeling. Maybe it's just so much less that I don't really notice? Given the 0-60 times, I think there's a problem - the "pushing you back" should be there but less than a big 'ol 400hp V8.

I pushed on the BPV and it sprang right back to the stop. I can spend the time pulling it apart, even replacing it (it's only $100), but I don't have sudden power loss or issues at certain RPM/speed, just consistently not having a lot of power. The supercharger seems to kick in around 3500 rpm, with most noise around 4500 rpm. How would I zip tie the BPV while it's installed? I think that's the best test from what I've read, though, I really don't think that's it.

When I have the belt off, I can test the pulley to see if it's spinning loosely or turning the supercharger (smoothly but not freely).

It's still a fun car to drive, but am I really missing out on the JCW experience because something's robbing me of power?

Before I charge headfirst into the tensioner, should I do something else? Any other tests I can do? Anything else besides the belt and supercharger I should be looking at?


Second issue - yesterday, I noticed some splashes on the coolant reservoir cap. I reused the cap off the OEM reservoir. Is this just a simple cap replacement due to a bad seal on it? (the coolant looks green because my Mini is green. I used the correct blue coolant)

 

A loud SC and low performance may mean a worn SC that is not building boost. You could diagnose with a boost gauge to see if less than stock.

 

Thanks. I'll look into boost gages. Any recommendations for an inexpensive solution?

 

I checked my OBDII bluetooth reader and it has a vacuum/boost gage. I hadn't realized this because the other car I used it on was naturally aspirated.

No matter what I did, I couldn't get over 12.7psi boost (it puts a red tic mark at the max boost). A 2006 JCW should get 17-18psi. I went through all gears, several times, pushing it just before the red line cutout.

Does this point to the BPV? A supercharger that's dying? (lordy, I hope not; it only has 50k miles)

 

The stock S is about 10 PSI and since the JCW has a smaller pulley, the 12.7 would be logical. Where did you get information that a MINI has boost values in the high teens? Fiat yes, Mini no.

 

I got that idea from right here on NAM.

https://www.northamericanmotoring.co...boost-psi.html

"Quite a few folks install their own boost gauges, and some get their boost readings from devices which plug into the OBD port.

The stock standard S boost figure is 0.9bar (13.05psi) with 150 millibars (2.17psi) of over boost pressure.

The stock JCW boost figure is 1.3 bar (18.85psi) with 150 millibars (2.17psi) of over boost pressure."
https://www.northamericanmotoring.co...u-getting.html

This forum seems to indicate a JCW with a 15% pulley would get 15% boost... conflicting info! Another user said a bone stock R53 got up to 11.5% boost.
http://www.mini2.com/forum/first-gen...-question.html

This says regular R53 gets a max of 13psi.
http://www.mini2.com/forum/first-gen...lve-boots.html


It would seem to be that a non-JCW R53/R52 gets 12-13psi boost. I have a JCW. 12.7psi seems low. That's all I'm sayin'.

An R53/R52 with a 17% pulley sees a 17# boost, a 15% pulley sees a 15# boost, but there doesn't seem to be much on the stock JCW boost. JCW has an 11% pulley, but other enhancements, too, so maybe 13# is realistic? If so, then I'll leave well enough alone. Maybe coming from a 400hp Pontiac with 400ft-lb torque wrecked my "pushes you back" meter.

In other news, I got a new coolant expansion tank cap. Hopefully that resolves the problem there.

 

Your 2nd example was for a Gen2 that is turbocharged. The Gen1 are supercharged. The 1st thread reflects the 10 PSI that I noted. Unless your car has been tuned you are not going to see those high numbers.

Pretty sure that there is a recent post here that notes the Gen1 ECU will only allow up to around 19 psi. That post was from a guy that tracks his car and I would use his info before somebody else that does not. Last, using simple math, and I recognize that there are other factors, if the stock psi is 10 to 11 and the JCW has a 11% smaller pulley, the additional boost would be around another 1 PSI

 

To be fair, the second example doesn't say whether it's first or second gen. I do know that first gen are the only supercharged.

I don't understand why an 11% smaller SC pulley giving 1psi is "simple math."

However, upon further research with recorded video vs. user reports (YouTube vs. forum posts), it appears that 12.7 is probably in the ballpark for an R52 JCW.

I found this PDF of the California Air Resources Board saying the Sprintex supercharger has 13psi boost. https://arb.ca.gov/msprog/aftermkt/devices/eo/D-695.pdf

The consensus seems to be the 15% pulley is a 15% boost, 19% pulley is a 19% boost, and stock is 10-11% boost. I believe the forum posts showing anything different are modified cars.

12.7 seems to be correct based on what I can find. Can't find anyone that has a video of an R53/R52 JCW, unmodified, showing boost, however.

I believe this exonerates my BPV.

Back to the original question, I think my next course of action is replacing the belt and belt tensioner.

 

Your second example is in the Gen2 section, when I look at linked threads I usually go to the top and see what subforum I am in. It also talks about "over boost" and waste gate" that the Gen1 does not have. On the math, if the pulley is about 11% smaller than the speed of the belt would increase about 11 % and if you used the same factor on the PSI, 111% of 10 or 11 is about 1 PSI.

As your boost is about where it should be if the car has the stock tune, changing the belt and tensioner is not going to get you anything in more PSI. If the belt is cracked, I would change it and if you have no service records, I would change the tensioner as well. My vert had 46k on it when I bought it and I did the belt, tensioner, all fluids, crank sensor o-ring, water pump, tstat/housing and two PS hoses.

I also put a different cam, larger injectors and a tune. Very happy with the car, BUT, it is never going to match a rear wheel drive car for off the line times.

 

Oh, how about some pictures of the car?

 

What I mean about the simple math is that I don't know that boost is linear proportionally to the gearing change. Since a normal sized pulley gives 10-11psi and the 15% gives 15, the 19% gives 19, but the 11% doesn't give 11psi.

I'm not looking for more PSI, I was wondering if it was too low. There's a lot of misinformation (or just missing information) about what it should be. I think my boost is fine, I'm not trying to get more, I'm trying to make sure it's right!

I went out and drove my Mini hard yesterday, with some strong 3rd gear revs up to the red line (but not into) and I got a peak boost of 13.4psi. Typical is high 12.x, though.

Then I found a deserted dead end street (I live on the edge of town by a bunch of farm land) and did a few 0-60 runs. Still couldn't get better than 7.8 seconds. I think launching is killing my times. With DSC on, I run into the throttle cutout, and with DSC off, I spin the tires too easily. Maybe it's the driver, not the car :(

The prior owner left some records, but didn't see anything about the belt tensioner. He didn't do anything but drive it, didn't know about the supercharger whine (never got it over 4000rpm), he was just an old dude that loved to go out for a Sunday drive with the top down. The strut tower mounts were cracked BAD, so bad that that I put coilovers in right away and was afraid to drive the car, but he had no idea (one tower was slightly mushroomed and the other wasn't at all). The power steering reservoir was coated and sticky, I replaced the o-ring and it's been fine since, but he had no idea.

I need to clean up my green machine but I'll put some pics up soon.

I have the belt and the tool, but I put it off because I only want to tear it apart once, so I'll get in there and do what I have to do without repeatedly tearing it apart. I might go ahead and change out the crank pulley and tensioner pulley while I'm in there since they're a common fault. And if I'm doing the crank pulley, I'll do the crank seal while I've got it off. I'd love to do the fluid damper but this is starting to add up and I'm not looking to jack up the performance over factory JCW.

Any other pulleys or service I should do while I'm in there?

Later this year, I'll do the rear sway bar and adjustable camber in the rear. I'm waffling on the 22mm or the 25mm.

Oh, and I replaced the cap on the coolant expansion tank, but there's still fluid coming down from it after hard driving. The car doesn't seem to be running hot (the OBDII app has a digital temp gage), though it's been hot as stink here in Sac-town - it was around 108F first time I noticed the leak from the cap, and it was 105F when I noticed it again. It wasn't a problem when it was down in the 70s and 80s. Maybe I should just replace the thermostat and housing? And I should go get the coolant flushed because I'm sure it's never been done. I have a friend that co-owns a BMW specialty shop and they service Mini's, of course, but he's always busy (never buy a BMW unless you like dumping SERIOUS cash into my friend's pocket).

 

I hear you on the math, said there was other factors. With the Mini, I'm not into 0-60 times, sold my LS3 vette and kept the Mini. The Mini is more fun to drive. On the cap, either the seal is bad due to the age, or your engine is getting hot.

If you put the car in front service mode, the crank o-ring, water pump and tstat would be logical with the age of the car.

Minis are built for twisties.

 

The reason I'm focusing on 0-60 it is that it seems that something isn't right with the car, I have this suspicion that the power isn't what it should be, and I'm looking for a metric to prove that out (or disprove it).

I've taken the Mini up to my favorite twisties in the foothills many times. These are the places I used to take my motorcycle, and the Mini is just as fun. Quite frankly, that was the primary motivation for buying the Mini, plus it's easy to work on, the purchase price is cheap (used), there's massive parts available, and there's still a thriving community.

 

Did you do a compression test? And perhaps stupid but did you do a dollar bill test?

 

No and no.

I had never heard of a dollar bill test, just Googled it, will test later tonight.

I've always wanted to get a compression tester, this is as good a reason as any, and I found one with over 300 reviews at 4.5 stars on Amazon for $17, and a $5 coupon to boot, so why not spend $12 and add it to my garage?

 

You have not noted any skipping so thinking the valves are not burnt (the dollar bill test will prove right or wrong) but as you said the previous owner may have neglected the engine coolant, it may be that they also neglected the oil and perhaps the cylinder walls are worn.

Let us know what you find after the compression test assuming the dollar bill test goes well.