[shushikiary]

I just installed the VTT hot side charge pipe, I've found doing everything possible to help the turbo's move air is a BIG deal at altitude. Inlets, a good cold side charge pipe, and a good hot side charge pipe I've found make a very decent difference.

[GODDSPD]

Originally Posted by shushikiary

I just installed the VTT hot side charge pipe, I've found doing everything possible to help the turbo's move air is a BIG deal at altitude. Inlets, a good cold side charge pipe, and a good hot side charge pipe I've found make a very decent difference.

I have to disagree. According to my logs, inlets and outlets did not make a significant improvement at my altitude. My theory as to why is basically the same reason you won't see much improvement with inlets if you are running a mild pump gas tune.

Essentially at higher altitude the turbos are not moving as much air and therefore the stock inlets are not as much of a restriction.

If you have before and after logs showing the improvement please share.

[shushikiary]

I actually do happen to have those logs.

Lowered WGDC by about 5% with about 0.3 increased PSI around 6200 rpm.

Of course, since they were taken at different days its not a perfect example due to DA changes and other possible factors, but you can draw your own conclusitons.

before:
http://datazap.me/u/shushikiary/mhd-...5-30&solo=2-30

after (also in the name of the log):
http://datazap.me/u/shushikiary/de74...5-30&solo=2-30

I suspect that due to the higher boost setpoint factor, that its not just about total volume flow, but more about reducing restrictions so it effectively reduces your setpoint factor from the compressors perspective, thus pushing the operating point into the more efficient part of the compressors map as much as you can, so every little bit helps.

[adidoman]

Originally Posted by GODDSPD

Essentially at higher altitude the turbos are not moving as much air and therefore the stock inlets are not as much of a restriction.

I would completely disagree with this statement. At high altitude the turbos have to move more air since there is less oxygen, and the turbos have to work harder to get to the same PSI that you would have at sea level. Therefore, having inlets would reduce the stress on the turbos and be more important to have since the turbos have to work harder up at altitude

[Milan]

Originally Posted by adidoman

I would completely disagree with this statement. At high altitude the turbos have to move more air since there is less oxygen, and the turbos have to work harder to get to the same PSI that you would have at sea level. Therefore, having inlets would reduce the stress on the turbos and be more important to have since the turbos have to work harder up at altitude

Right.

At elevation the turbo has to spin faster in order to create the same amount of boost that it would be making at sea level.

Honestly I don't think it will matter much and people in this thread are blowing things way out of proportion. The only thing you will notice is that the car will be slow as balls at that elevation.

[GODDSPD]

Originally Posted by shushikiary

I actually do happen to have those logs.

Lowered WGDC by about 5% with about 0.3 increased PSI around 6200 rpm.

Of course, since they were taken at different days its not a perfect example due to DA changes and other possible factors, but you can draw your own conclusitons.

before:
http://datazap.me/u/shushikiary/mhd-...5-30&solo=2-30

after (also in the name of the log):
http://datazap.me/u/shushikiary/de74...5-30&solo=2-30

I suspect that due to the higher boost setpoint factor, that its not just about total volume flow, but more about reducing restrictions so it effectively reduces your setpoint factor from the compressors perspective, thus pushing the operating point into the more efficient part of the compressors map as much as you can, so every little bit helps.

That's about the same improvement I saw; nowhere near the 5+psi at redline guys at sea level are seeing...

[GODDSPD]

Originally Posted by adidoman

I would completely disagree with this statement. At high altitude the turbos have to move more air since there is less oxygen, and the turbos have to work harder to get to the same PSI that you would have at sea level. Therefore, having inlets would reduce the stress on the turbos and be more important to have since the turbos have to work harder up at altitude

I should have specified in that sentence, but I was referring to max WGDC. Sure, 10psi at 5000 ft requires the turbos to move more air than 10psi at sea level, but the difference between max boost at max WGDC at sea level vs altitude can be more than 5psi.

So, which scenario is moving more air- Stock turbos maxed out at sea level, or stock turbo's maxed out at altitude?

[V8bait]

Originally Posted by GODDSPD

I should have specified in that sentence, but I was referring to max WGDC. Sure, 10psi at 5000 ft requires the turbos to move more air than 10psi at sea level, but the difference between max boost at max WGDC at sea level vs altitude can be more than 5psi.

So, which scenario is moving more air- Stock turbos maxed out at sea level, or stock turbo's maxed out at altitude?

10psi at sea level vs 10psi at altitude are completely different airflow. At altitude you'd need like 14psi to hit the same airflow as 10psi at sea level or so, and the restrictiveness of the stock induction system would be comparable at that level. At 10psi vs 10psi altitude is less restrictive but less power due to less airmass.

The turbos move air based on pressure ratio and shaft speed. They have a maximum flow rating for specific pressure ratios. At sea level they can hit that airflow with a lower pressure ratio, thus lower shaft speed and better efficiency (less heat). If you max the shaft speed at see level you're likely just making heat, not more airflow.

At high altitudes you need to run higher shaft speed and less efficient to move the same airflow. You may run out of shaft speed before you hit the same airflow. Cars at altitude won't move 500whp of air with stock turbos for example, it's outside of the turbos abilities.

Tl;dr- At altitude stock inlets are less restrictive since you're generally moving less air, but more important if you're trying to really maximize your setup since any restriction is worse at altitude where you're already running inefficiently.

[GODDSPD]

Originally Posted by V8bait

10psi at sea level vs 10psi at altitude are completely different airflow. At altitude you'd need like 14psi to hit the same airflow as 10psi at sea level or so, and the restrictiveness of the stock induction system would be comparable at that level. At 10psi vs 10psi altitude is less restrictive but less power due to less airmass.

The turbos move air based on pressure ratio and shaft speed. They have a maximum flow rating for specific pressure ratios. At sea level they can hit that airflow with a lower pressure ratio, thus lower shaft speed and better efficiency (less heat). If you max the shaft speed at see level you're likely just making heat, not more airflow.

At high altitudes you need to run higher shaft speed and less efficient to move the same airflow. You may run out of shaft speed before you hit the same airflow. Cars at altitude won't move 500whp of air with stock turbos for example, it's outside of the turbos abilities.

Tl;dr- At altitude stock inlets are less restrictive since you're generally moving less air, but more important if you're trying to really maximize your setup since any restriction is worse at altitude where you're already running inefficiently.

Agreed. That is what I was getting at.