So in this video you will see me in 5th gear WOT around 3k rpm, and my boost fluctuating around +/- 3 psi at any given value. I am fully WOT, pedal smashed and the boost will rise and fall. What is going on guys? I feel like this is not a normal thing.

I have invidia cat back exhaust, 15% reduction pulley with new belt installed about 15,000 miles ago and a custom massive filtered short ram intake. 1 degree colder ngk iridium plugs, and ngk 9mm wires. As far as performance parts go. And 256k miles on the car. I wonder if this is my belt tensioner but before i go and replace it i wanted some input, like, as to whether i just needed the bushings or should replace the entire assembly and maybe if any of you thought of anything else to check out.

 

Get an analog gauge.

 

Well I have A 1/4 of a million miles so should I spend 200$ on a new tensioner assembly or buy an analog gauge? I thought aem made good products. My turbod Suzuki always read between 11-13 with a hall man manual adjustable boost controller and I always thought it's fluctuation was either in that controller or my weak 3 psi wastegate spring.

 

I would go tensioner if you have never done it. Check for leaks too around intake areas where it connects start with boots at that odometer reading.

 

I did replace the intercooler rubber boots, but have not done the gaskets on the horns.

Anyone got an exploded diagram of the intake piping so I can see how many gaskets there are and know what to order?

 

Besides the gauge freaking out, are you noticing power issues or fluctuation of SC sound, noises from belt or tensioner ?


If not, the electronic sending unit for the gauge is probably kaput.

 

do you have a restrictor off the T where you read the boost? Even my analog gauge would rattle unless I put a restrictor between the vac line and the gauge.

 

I teed in between the intake manifold and fuel pressure regulator. It's 1/8 npt fittings. By chance do you have a link for this part so I know what to order? It's worth a shot! I don't have any restrictive as of now. I remember a similar issue with my Suzuki I couldn't get it to boost past 3 psi until I swapped 1/4" hose to 1/8" vacuum hose on my wastegate. So I believe it in this case. I'll order and try it!

 

Unless I hit bumps, no the supercharger whine is pretty consistent I suppose. I have a loud exhaust though so it's hard to hear. Do you guys think that an obd 2 scan gauge reading the boost would be as accurate as they get since it's right off the map sensor? Because I have one and I could use that. So my question is if I use my scan gauge II and still see fluctuation then to tackle the belt tensioner.

 

Try this site to get the part #'s and diagrams for your MINI:
http://www.realoem.com/bmw/

If you look at the top of the belt tensioner "gauge" (metal bar with holes), do you see at least one hole protruding thru the top?

On a 15% reduction pulley, the r53 should be around 15psi... the max boost is 12psi from your video; so not only is your boost not consistent, you're also running a little low.

Are you getting any DTC codes? Do a pressurized test for leaks in your system.

 

I won't damage seals doing a leak test? Is it okay to do it on the throttle body if I just put to run position and a brick on the pedal? Also that video is low-mid rpm i didn't go past 3300 rpm. At around 4500 I usually at 15 but by redline in 2nd or higher gear after I have had a previous wot gear and shifted fast I can spike to 18 psi around 6k rpm but from my understanding superchargers should be instant boost all the time? I have what I need to do a pressure check I just hope it's bad enough to hear it at least. This cars so cramped I couldn't possibly be in there squirting soapy water and looking at all seals. Thanks for the link and info!

 

You are worried about damaging the seals on you car but not about BLOWING UP YOUR MOTOR...idling at redline using a brick....just made my day!!

 

If your boost is going up and down so much...i'm betting it is a bad part (imo) a bad install.....
One tip..check your ground wires on the install...i'm betting you have a bad ground wire from the guages behavior... A test with a multimeter will verify this...and no risk of BLOWING UP YOUR MOTOR.

 

Wait, blowing up my motor because a bad ground to my gauge?

 

Not from THE guage...but from using a BRICK on the gas pedal as you stated before in neutral...while looking for a boostleak...idling at high rpms..like typical upper road rpms without a load is VERY HARD ON A MOTOR.
Simply put...I think the guage is an issue cause you would see performance issues in the real world with such variability of boost.

 

+1, if your not seeing noticeable performance differences, you're most likely looking at gauge issues.

And yes, high rpm's in those conditions, especially prolonged, it's bad for your engine, engines are designed to be used under a load, esp. at higher rpm's.

 

So I going to try this restrictive and look at my gauges ground. Then try a new tensioner and belt. Also I did not say with the engine on. I meant with it in run position but not cranked on. I am laughing hysterically you all thought that's what I was going to do lol. Come on I took a Suzuki Aerio that ran 19s and made it run 13s give me some credit! I've never boost leak checked a supercharger before. On my Suzuki I would put the coupler onto the pipe that came off the turbos compressor wheel charged side. Otherwise it would look pressure past the seals in the turbo and bubble oil in my pan. So that is my concern with the supercharger I do not wish to damage it!

 

FYI, I had two of those gauges.....Each one only lasted a year, POS IMO and waste of money. Both cases it was the sending unit which is mounted in the engine bay.

For last 4+ years I've been using an analog gauge as mrbean suggested already. It's not all that more difficult to install, just extend the boost line hose thru the firewall....

 

I am going to replace the tensioner since that is known to be an issue anyway and with the mileage I have on her. I bought her with 236k miles and a lot of parts were capute. So things been replaced as needed. Right now I been saving for a clutch and new axles as my cv boots are shot and my axles just fall out when I unbolt the lower strut mount. :(

 

Like everyone else is saying...I'd say you have a bad gauge or sending unit. Or a wiring issue......

 

I had purchased the JCW gauge cluster, it came with a T with a restrictor in one of the connections.

However, this was not enough in my case, still rattle. Went to an O'Reilly and bought a coupler with a restrictor built in. Fixed the problem.

When checking in this way, have a friend record it while you accelerate in second or third or whatever is necessary on a freeway on-ramp. Not sure if an engine with no load would build much boost or give a reading that is meaningful.