Nitrous and altitude

**Mr. Luos** · 06-17-2006, 07:02 PM

Originally Posted by Bob'sWS6

As I recall irregardless of altitude a nitrous car will run the same at 3000 ft. as it will at sea level.

I don't believe that is correct.

What it will do is recover the power that is 'lost' at altitude. Basicly a 75 shot would give me my power back that I lose.
But...when at sea level, I would gain that 75 shot as well.

Am I right here????

**mrr23** · 06-17-2006, 07:41 PM

what he is getting at is the nitrous effects are not influenced by altitude because it provides it's own oxygen. you are correct in thinking that if you are losing 75 hp NA due to the altitude, you will 'get it back'. what he's getting at is altitude doesn't affect nitrous.you are mixing up the NA results of a car when racing at sea level vs say 3000 ft above sea level. even blower (FI) cars are susceptible to altitude because they can only push in whatever air is around them.

now you know why nitrous cars get a weight penalty in racing. nitrous cars usually have to add 200 lbs to compete in the same class.

**Mr. Luos** · 06-17-2006, 07:52 PM

So I would gain 75 horse from said 75 shot regardless of where I am??
This makes sense to me.

I thought he made it sound like it completely got rid of the affects of altitude.

So.
I made 527 RWHP corrected. Add 75 shot and I am looking at 602 RWHP corrected.
I made 440 (give or take) uncorrected. Add a 75 shot and I am looking at 515 uncorrected.
The shot just doesn't lose the percentage of power right??

Sorry if I am making this more difficult than it needs to be.

**LS1Power06** · 06-17-2006, 10:40 PM

Originally Posted by Mr. Luos

I made 527 RWHP corrected. Add 75 shot and I am looking at 602 RWHP corrected.
I made 440 (give or take) uncorrected. Add a 75 shot and I am looking at 515 uncorrected.
The shot just doesn't lose the percentage of power right??

Sorry if I am making this more difficult than it needs to be.

not to hijack this thread but theres a difference between corrected and uncorrected HPs, obviously, but why are they different and what makes them different?

**mrr23** · 06-18-2006, 08:03 PM

uncorrected is what the car made at that exact moment with those exact conditions. what 'correcting' does is try to make similiar comparisons in all areas of the world.

http://dynojet.com/gmhtpmag3.shtml
direct from dynojet:

Originally Posted by dynojet

In the United States this is usually Society of Automotive Engineers (SAE) standard J1349 Rev JUN90. Correcting to SAE J1349 alters the data to make it seem as if it was taken when the atmospheric pressure was 29.23 in/hg., the temperature 77°F and the humidity zero.

The degree to which temperature, pressure and humidity affect power output is constant. If we accurately measure those parameters at the dyno location, we'll know the difference between the atmospheric conditions at the time and location of our test and those of SAE J1349. That difference is applied to the raw data and the result is corrected power and torque which we can compare to other data taken anywhere in the world that is also corrected to J1349.

**mrr23** · 06-18-2006, 08:05 PM

Originally Posted by Mr. Luos

So I would gain 75 horse from said 75 shot regardless of where I am??
This makes sense to me.

I thought he made it sound like it completely got rid of the affects of altitude.

So.
I made 527 RWHP corrected. Add 75 shot and I am looking at 602 RWHP corrected.
I made 440 (give or take) uncorrected. Add a 75 shot and I am looking at 515 uncorrected.
The shot just doesn't lose the percentage of power right??

Sorry if I am making this more difficult than it needs to be.

the thing with nitrous is if you want 75 RWHP, then you jet accordingly until you achieve 75 rwhp. the inital jet chart you get is a close approximation.

**Mr. Luos** · 06-18-2006, 08:13 PM

Right. I know that part.

So if I am spraying 100 shot and run a 11.0 at sea level.
Will I spray the same shot and run the same time at 5800 feet??

LS1Power06, I live 5400 feet above sea level. The air is much thinner here. The car suffers with the lack of air.

**mrr23** · 06-18-2006, 08:29 PM

no. still rely on atmosperic pressure for the NA part of equation. you may see quicker times using the n2o given addition of oxygen.

examples:
100 rwhp = 1 second quicker
sea level you run 12.0 NA
5800 you run 13.0 NA
in both cases, you will run at least 1 second quicker on the bottle. this, given all other things taken into account. traction, activation time of n2o, etc...

you might run a little quicker on the bottle in higher altitiude vs seal level. this is a guess though.