Let me answer your original question, how do you start BELOW sea level? It's called vacuum, creating lower pressure that way air is pushed in. If the air pressure in the engine (intake, combustion chambers) wasn't lower than atmospheric pressure, how would air get in? Air isn't sucked in, the weight of the air around you pushes it in.

That's why people have to wear space suit, otherwise you'd basically explode, and your blood would boil.

And actually, yes, you are idling at around -6 psi if you pull 12 inches of vacuum.

Of course you wouldn't be boosting at idle, the turbo isn't designed for that. some turbos are, actually.

 

The real argument I'm making though is that the boost guage is measuring the difference in pressure between the pipe and the atmosphere. It doesn't measure everything based on sea level pressure, otherwise it would read 5 psi at the bottom of the ocean (if you drained it obviously) and -3 psi at 1 mile high.

Plus, lets say we dyno the car at 8 psi up here and get 200 hp, then do it at sea level and get 225 hp. The difference is that more air is entering the engine at sea level; more air+more fuel=more hp. The increased total pressure at the port openings is what forces more air in. If 8psi up here was the same as 8 psi at sea level then the horsepower would be the same, but it isn't, therefore there is less air (meaning less pressure) entering the engine.

 

If you're talking about a stock gauge, forget it, those are garbage. Some gauges are calibrated for sea level. I'm not talking about gauges. I don't know how MY gauge is calibrated, and neither do you, unless you found it in the Factory Service Manual or called Mazda. it could be either way.

And no, you're wrong again on getting more air in. Like I said, you need to go over some physics, because you don't have a concept of what is really happening.

With your less denser air at 6000 ft, the turbo has to work harder to get to 8 psi as it does at a lower altitude. THIS is what creates power, not this special "more air." Go look up the formula PV=nRT, it's the ideal gas law, and it very roughly explains THIS.

Do you know what density is?

 

yes, and at the same temperature and pressure a gas is the same density.
More pressure is the reason why turbos make more power. There are two ways to make more hp: lower the resistance for the air entering the engine (porting), or increase the pressure so more air is forced in (a turbo). You already said yourself that the outside pressure is the only reason air enters the engine.
You do also realize that up at this altitude, the thinner air is easier for the turbo to compress.
PV=nRT does not explain flow characteristics for an engine, all you can do is use it to find unknowns in the equation.

 

or, you lower the temperature of the intake charge, the reason why water injection works...

 

how does that relate to this argument though?

 

well, you didn't state that in your *ways to make power*....

Why do you think a huge turbo makes more power at 8 psi than a stock turbo? It makes a significantly larger amount.

Your intake temps are higher, it's not a *different* pressure. psi is psi man. It's a standard UNIT.

 

Also, improving your timing, having a stronger spark will give you more power; lowering your unsprung mass can give you less drivetrain loss and give you more rwhp.

PV=nRT explains how GASSES work, if you understood the equation you would understand your original question and the concept you can't figure out

You have a lot to learn It's ok, when I was in high school I thought I knew everything too....

 

what you're saying doesn't follow logic though. 8 psi up here is not the same as 8 psi at sea level.

 

Oh my god. Just drop it already!!!

Rotary, your 16 years on this planet have not aged you enough to argue with MULTIPLE people proving you wrong REPEATEDLY. Please stop. You're wrong. Stop crying.

 

wait until he argues with his professor about being "logical" and fails his chem or physics class :p

 

I agree, no more arguing in this thread.
PM me and explain, in detail, why you're right. Please, if I'm wrong I would like to know why, but so far I'm not convinced.

To summarize:
You are telling me that if the mechanical VDO boost guage reads 8 psi at 1 mile high, and 8 psi at sea level (assuming all other things are the same, like temp, etc.), that the hp will be the exact same?

 

There is a difference between 'gauge' and 'absolute' pressure.

'Gauge' pressure is pressure relative to local conditions. I.E., X psig at sea level is of greater pressure than X psig in Denver.

'Absolute' pressure is referenced to sea level. X psia at sea level = X psia in Denver.