Dieselnick

I recently installed gauges in my 94 Ram and am only getting a max boost of 15 at WOT. I know that is low, but I live at 4400' elevation. Does elevation effect boost that much?

Thanks,
Nick

CamperAndy

Elevation does effect boost and can reduce performance by about 3-4% per 1000 foot. So 4400 feet is around 16% reduction so if you get 20 at sea level you would be down about 3 psi at your location.

carl48

the drop in air is 2.7% per 1000 ft elevation but no drop in wot pressure the turbo has to work a little harder and you will spool up slower is the only thing you will see. i am at 7,000 feet and the ski run is at 12,000 feet the 2.7% drop only affects naturally aspirated motors

Dieselnick

Do you have a boost gauge on your 06? If so, what kind of boost are you getting?

Thanks,
Nick

carl48

empty at 60 i see about 2 or3 lbs towing at 60 with 21,000gvw about 10lbs pulling 7% grade about 31lbs maxed out at 11,000 feet 34 lbs the altitude does not change the boost reading only the load does we are after mileage and the mods we make give us more power with lower egt's and lower boost readings for a given load than stock

Rare1

I see no difference in the reaction of my boost gauge, high elevation or sea level I get low boost with low power and 25+ psi under high load. However, there seems to be a reduction of power at high elevations.

I guess you could get your boost up to 20 (stock?) if you provided more fuel.

CamperAndy

Your performance loss number may be more correct (I was generalizing) but irrespective of it being naturally aspirated or turbo boosted there is a loss due to altitude. The turbo is fixed geometry and will move less air the higher you go for a given turbo speed. Less air in means less mass out for drive pressure. The only way to maintain drive pressure is more fuel but even that has limits. Turbos help maintain performance but they are not unlimited in what they can fix.

I can make 42 pounds at 2400 feet but when at 9800 feet I am down to 36. This is empirical data from my truck but if you want I can dig up the ISO curves for correcting engine performance to sea level.

CamperAndy

I decided to add the standard correction curve anyway. Why wait to be asked.

mopardamo

Hello,

Turbos make pressure. The waste gate helps regulate that pressure. Under heavy load conditions the elevation should not affect the waste gates performance. The computer may alter the pressure at which it opens but I do not think that is built into the programing. There should be no change in the boost provided that the turbo is correctly sized. The air has less oxygen and will not produce the same power though.

Damon

kevellis32

I can very easily push 33-35 under load at 6000'. Should affect your boost numbers at all, a significant loss of power due to the lack of oxygen, but no difference in PSI

CamperAndy

I like these threads.

The amount of O2 percent (20.9%) is the same no matter what the altitude is that you are driving in but what is different is the air is less dense so there are less O2 molecules in that 20.9% make up the higher you go.

This is where your handy turbo comes into play. Forty psig made at sea level has the same amount of O2 molecules as 40 psig made at 10,000 feet. The difference is that the turbo required about 35% more air volume to make that 40 psig.

The problem with the turbo is it would have to be over spun (out of its normal performance map) to flow that volume and would not be very good at compressing the air efficiently.

soulezoo

I have to side with CamperAndy on this one... we can talk all we want; the reality can not be denied. I commute each and every day from 4000' to sea level and back. In the same day, same conditions, same mods and tunes, I can hit 55-60psi at sea level and only 45-48 at elevation. That's a reality...

mopardamo

Hello,

I agree on the %o2 thing mostly. If you really want to know the air does change content as you go up but it is not worth going into. I just did not want to explain it out like you did. A turbo brings it's own air.

If the turbo is properly sized it will not experience a pressure drop. Like the stock trucks. Your trucks are heavily modded for a specific purpose and have a different reaction and that's fine. I believe that properly sized the turbo should be able to make the same pressure in the system at sea level and 9000ft..

Damon

plvaulter06

do you have fuel mods yet on your 94? you should be able to make way more than that. I'd block your wastegate. My 94 will make tons of boost i just have to keep out of the throttle in 4th and 5th otherwise it'll make way over 40lbs

CamperAndy

I really want to know so please post your references as it would be worth it to learn a new bit of physics. Before you say there is no O2 at 300,000 feet please remember we are talking about where we drive our trucks.