Originally Posted by 5.0THIS

I'm really trying hard to be as nice as possible to you, but in short, you have no ****ing clue what you're talking about. This is Colorado bud, our ambient air pressure is right at 12 psi, not the 14.7 you see at sea level. All dynojets utilize standard correction factors, and up here, a 1.2-1.25 correction factor is very common, even in the winter. And in case you dont understand that.. it means that the dyno takes the actual recorded numbers and multiplies them by the above correction factor. him running 7.5 psi of boost up here is the equivalent of running about 4.5-5psi at sea level (in terms of absolute manifold pressure). A boosted LT1 running 4.5psi at sea level making 375rwhp ish, is perfectly realistic.



Actually, supercharged cars suffer equally as bad as normally aspirated cars at altitude. They will have just as much less absolute manifold pressure as a NA car, as the blower isnt spinning any faster to make up for the lost pressure. Supercharged cars merely have an easy way of making up that lost power, by pullying up the blower. As for turbo cars, they do suffer, some more than others. It can depend in large part on the type of boost control system that is utilized. It can also vary depending on how close to being maxed out a turbo is before altitude. If you have a turbo maxed out at sea level and bring it to altitude, it will suffer equally to an NA car. From what I have seen from local turbo guys, a factory turbo car might see ~5-8% loss overall, give or take.

Originally Posted by Sparkz28ss

maybe I like to give Jakerobb a hard time

Originally Posted by Sparkz28ss

first...... dont "try" to be nice to me...I dont give a **** if you are "trying to be nice".....all you had to do is explain it to me..not talk to me like Im some dumb****...maybe I like to give Jakerobb a hard time,or maybe I didnt take more then 2 seconds to think about it...... so...my bad....go get ****ed or something

Originally Posted by Kredz28

let the flaming begin
Cant wait for 5.0's response...i can tell this is going to be a good thread

Originally Posted by mgray

So, the boost gauge reads positive boost pressure in terms of measured barometric pressure upon its start, vice an absolute pressure calibrated at manufacture? (no need to be short with me; I am simply asking a question. )

Originally Posted by mgray

Yes, I am also told the map sensor measures barometric pressure before start. Some cars have a separate sensor for this function.

What I am concerned about are analog gauges. If the absolute manifold pressure is given as (barometric+supercharged pressure), the gauge displays supercharged pressure because barometric pressure is the tared zero. At barometric pressure, the gauge displays zero boost/vacuum (the gauge's calibrations will usually have a large zone for zero to account for changes in barometric pressure). Since the gauge, itself, is reading absolute pressure, and the printed calibrations make the displayed pressure relative, for an accurate reading, the display needs to be calibrated to barometric pressure. If a gauge reads zero at 14.7, and each calibration of measure is accurate (meaning a change of 1 psi on the gauge label correlates to an actual change of 1 psi, not 1.2, 1.22, 1.223 etc) then at 12.1, 7.5 psi of displayed, supercharged pressure, is actually 10.1 supercharged pressure.

The digital gauge, mine at least, measures absolute pressure as well. However, upon start, the barometric pressure is set to zero. With any changes in barometric after an off-on cycle, the gauge is effectively calibrated. Of course, this does little for going up and down a mountain. For some reason, I am not worried about this.

The question becomes, is the gauge calibrated to zero correctly? And, are the calibrations between each integer accurate? Even if the gauge is tared to barometric pressure as zero, the manufacturer might have averaged tolerances (scale changes) for barometric pressure changes in each calibration of pressure and vacuum.