I recently installed a boost gauge and it displayed 12 psi. I have a 15% pully and thought I should have around 15 psi boost. I live in denver and on my old car (turbo) boost was lower here than at sea level. Is this going to be the same senario with my s/c or am I going to need to start looking for a boost leak?

 

Anyone?

 

Sorry...I cannot really help you on this one, but I believe that it would be the same...Psi is Psi whether it be turbo or s/c...but get a second opinion on that one I don't want to give you false info...

 

12 psi at full boost at 5000ft is pretty good. That's about what I get here in Albuquerque which is about 5000ft.
I once confirmed this with Randy Webb (he mods minis in the Denver area.)

 

Sweet! the Dr. confirms it

 

I just had Randy Webb install a 15% on mine last night. I saw 13-14 PSI max here in Denver but that was in a higher gear, higher engine load, and WOT.

 

Much appreciated guys, this is good news. It should be intersting to see what its at when I go to the Pikes Peak rally.

 

You will see lower boost at altitude in a car with forced induction yes. Some turbo systems will compensate for said boost loss by boosting more (Depends on the car). Superchargers output the same amount of air though regardless of the altitude (No adjustability). The thinner air accounts for the actual pressure drop.

In planes, the whole reason behind turbocharging is to maintain power at altitude. The actual power increase is very minimal (usually 10 HP or less).

 

Matt:

I agree, make sure you have ample (5000+) RPM to be w/in the Superchargher's max effeciency range but also w/ the engine under a load. Such as pulling a long hill on West bound I-70 going into the mountains out of Denver. Cold temps will show higher boost than you would see in the same conditions on a hot summer day.

Don't get too worried about max boost. A Mini w/ stock intercooler & 15% Pulley was equal to my car when I was running a stock pulley w/ Laminova Intercooler. Higher boost w/out proper intercooling is like eating soup w/ a fork. You will realize 1% HP per 6 degrees temp change. Keep the IC cold between races w/ a bag of ice or ice water, don't let it heat soak from the engine temp.

Stock intercooler in autocrossing conditions removes about 20F, at highway speeds, 50F. The Lamiova pulled 165F on the Supercharged R53 Mini & 220F on a Turbo WRX & 1.8T VW autocrossing / street driving tests.

We tested a Mini w/ 19% Pulley / stock IC & the ignition timing was retarding 7 degrees. Same car after Laminova IC was added, the ignition advanced 7 degrees, for a 14 degree delta. More spark advance & more fuel regulated by the computer were due to the intake boost/temp sensor reading cooler temps.

Now contrast that w/ higher boost but having the computer back off the timing & fuel due to hot air temps.

Four years ago I watched a 16 year old driver in a Mini w/ not much more than a 15% Pulley get like the 6th fastest time in an Autocross held at Coors Field Parking lot in Denver during a BMW club sponcered race. Driving technique & superior handling of the Mini had more to do w/ his amazing time.

The look on some Vette club drivers faces when this kid wasted them was priceless. That was when I started wanting a Mini (okay & wishing I could be 16 again)!

My 2 bits,

Mike

PM me &/or to get my cell phone # if you want to discuss further. Brian said to tell you Hi.