So for anyone that has a boost gauge I was driving down the highway the other day and I got thinking.....does boost indicate how much HP is being created?

I noticed that as I started up a hill at a constant speed (cruise on) the boost would go from 7-8 pounds to 11 or 12.....start to whistle more etc......I know this is normal, and that more power is needed to climb hills......so can you figure out how much power the engine is making based on the boost gauge?

Truck supposedly makes 425 horse @ the flywheel....it tops out at 26 lbs of boost....at least that is what the gauge can read.....so do the math and each lbs of boost equals 16.34 horsepower.

So if I see 10lbs of boost is the motor making 163 hp? Just wondered if we have a "ball park" dyno on the dash as we drive around?

I know this isn't very precises but does the theory hold water?

Short answer = Yes, with lots of conditions.

Longer answer:
There is a correlation between intake boost & power produced. I don’t think there is a hard & fast correlation because there are many other factors involved.

It is my understanding that under most conditions the two factors do have a direct relationship and the correlation does hold fairly well. Plotting the two on a graph would show this, but exactly how much power is being produced will vary with other factors.

Fuel = HP, you just need to make sure you have enough oxygen to burn it. Since you are wastegated, you cannot use the boost gauge to indicate power, and even if you weren't RPM comes into play. 10PSI at 1500rpm<> 10PSI at 3000rpm.

On a gas engine where air/fuel ratios cannot vary widely....YES, Boost=HP.

On a diesel, the short answer is not necessarily. Boost can equal more HP, but it's more of a byproduct of the additional fuel which is needed to make HP (especially in a diesel)

you have so much horse power then when the boost kicks in it adds. its all on fuel, air, and resistance. the more fuel added the more hp... the better air flow the more hp... the less resistance you have the less hp needed...

I liked the first answer better....):h

I knew that it was a lot more complicated but I just wanted to see if the theory was correct.

I would think that given enough O2 to burn it clean ....boost does roughly equal power......yes power = fuel but boost is a result of fuel.....so boost = fuel = power......so basically boost = power. I LOVED logic in school.....:ro)

sorry...:rolleyes: I hang out with other engineers all day....so the smell of geek gets lost.......

didn't they measure the output of fighter plane engines in WWII by boost pressure? I mean the pilots would adjust the throttle to achieve a specific boost for a certian condition. Those were supercharged but boost is boost.

I know....way too much spare time. :D

I liked the first answer better....):h

didn't they measure the output of fighter plane engines in WWII by boost pressure? I mean the pilots would adjust the throttle to achieve a specific boost for a certian condition. Those were supercharged but boost is boost.

I know....way too much spare time. :D

back in the old days of the aforementioned airplanes, they had compound "boosting" turbosuperchergers and superchargers, and some even had PRT's also ( power recovery turbines) the supercharger was for "over-boosting" for more power, and the turbosupercharger was for "turbo-normalizing" or to make up for the loss of air density from the higher altitude....

on a side note, the germans where realy the first ones to use nitrous oxide on thier war birds to make up for the thin air at high altitude (guess they didn't have boost)

They also used water-meth injection.

Nitrous and water-meth were used to climb rapidly to altitude to intercept Allied bombers which flew very high.

Nitrous can equal boost, it comes down to just how much oxygen is going in the engine whether it be in a mechanical form or chemical form (given the same amount of fuel to be burned).

Boost = pressure which equals more oxygen in the same given space. Normal atmospheric conditions carry about 19 to 21 percent usable oxygen; double the pressure, double the oxygen content in the same given space. Nitrous carries approximately 33 percent more oxygen, the more nitrous by volume induced, the more oxygen in the same given space.

Can’t remember exactly off the top of my head so don’t quote me on it, IIRC, my rough calculations a while back indicated that it would take approximately .95 lbs/min of oxide to make the same horsepower power as 1 pound of boost, given everything else being equal (i.e. same rpm, same amount of fuel, etc.)

Interesting reading for you all;
http://www.beyond-designs.com/download/Naca_E5F26.pdf

http://www.beyond-designs.com/download/Naca_3624.pdf

http://www.beyond-designs.com/download/Nasa_104330.pdf

http://www.beyond-designs.com/nitrous.htm

If this were the case, either my gage is wrong, or I could pull my truck by hand. Because I see 0 boost a lot, and very seldom more then 3-5 lb :eek:

I'm with Thomas. Boost can be used as an indicator, but horsepower comes from fuel, not air. A diesel is not air-throttled; rather it is fuel throttled. Of course the (stock)computer will make sure it never dumps in more fuel than it has air available to react with, so you could argue the more air available the more fuel can be dumped in. But, at the end of the day, the fuel is what makes the power.

yeah, I agree fuel = power.....but given clean burning....meaning that there is enough air to burn it clean.....and the computer makes sure there is......air is in at least a minimum ratio with fuel so while it's not set in stone.....in a clean burning engine... air roughly = fuel, cause the computer won't dump in more than it can burn (normally)....in a ratio......so in a computer controlled engine air is in ratio to fuel and fuel is in a ratio to power.

I beating a dead horse I know.......

thanks guys......

I think it's safe to say that it is a very rough estimate........