Ahh! Outstanding! Now I see the light!
Thanks man
-Dave

 

When I bought the wrx I thought that the boost gauge would be a good idea. Still do. I had the factory install the package. To my surprise, it comes with no data about calibration or interpretation.
I understand the psi and mpa relationship but still am at a bit of a loss with what those readings are actually telling me about the engine and my driving at any given point. Two examples: getting on a highway, I may accelerate hard, up to 6k rpm, the gauge reads .05. Getting sloppy climbing a hill, needing to downshift a gear, will see the boost climb to double the value, 0.1, at 2.5k rpm.
How can I use this data?

 

Thanks for the reply. That odd reading was what attracted my attention, 0.1 @ 2500. Understand, though that I was driving sloppily up a hill in 5th when I should have already shifted down. I have not tried to duplicate the reading. I will, later this week.
I guess my issue is simply being unsure of what use the gauge is. Other gauges in a car, or in an airplane for that matter, provide a baseline reading from which the operator can determine what is normal/abnormal. If my oil temp. is usually 70 degrees and I see it at 120 then I know that something abnormal is occurring. I don't have that facility (yet) with the boost gauge; it seems like I should be able to use it for something like seeing whether I am driving efficiently in a particular situation or just in general.

 

Well, I'm suprised that you had full boost at 3500rpm in 5th gear.. But FYI if you put in less than 55% throttle the computer will only give you .05 MPa.... Once you dip into the throttle past 55% you will see .1 MPa provided you have enough RPM. As you spend more time behind the wheel you will become accustomed to what is supposed to be happening with the boost.
-Dave

 

Thanks for the replies to my questions about the gauge. You have been way more help than Subaru( though, to be fair, it was a Subaru CS guy who directed me here.)

 

Just a follow up to my original note about what I thought was an odd reading on the gauge(0.1mpa @ 2500 rpms in 5th). Understand that it takes sloppy driving to produce this reading - but enough folk thought that I meant 3500 rpms that I began to think that I had misread the gauge. Doing this was all part of an experiment in finding out what the numbers on the gauge meant in terms of efficient driving.
Approaching a medium hill in fifth gear at about 2500 rpms, I did not downshift as the revs fell. Instead I stepped hard on the throttle( similar to what you would do if you were driving an automatic ). Revs were at 2300 or so; the boost popped up to 0.1 as the engine moved through 2500. The boost dropped to normal levels directly after that peak. The next hill, I did the same in 4th. Same result, except that the boost drops off more quickly due to quicker acceleration onto the power curve.
What I learned is, I guess, pretty obvious - lots of boost in high gear at low rpms is sloppy driving. A worthwhile experiment would be to record boost pressures in similar circumstances with gears 1-2-3. It's all data.

 

Do you have an EGT gauge? If so this test would result in high egt and probably detonation as well, especially if your car is tuned. As you said this is poor driving as you are heavily loading your engine - although I would expect the boost levels you are seeing. Bottom line, don't do that.

 

It is very sloppy driving to leave it in a high gear for a hill climb while accelerating. You are putting a lot of undue stress on your engine this way, and increasing your EGTs and possibility of detonation significantly. However, if you need to gain just a couple MPH on the highway when you are a little slower than you would like it's not a big deal - just don't do WOT runs in 5th gear if your car is tuned.