High elevation gear change
Thread Starter
Burning Brakes
Joined: Sep 2008
Posts: 826
Likes: 12
From: Phoenix, AZ
High elevation gear change
Hey,
I did another post a while back asking about torque loss from going from a 3.42 to a 3.90 with a 6 speed. I realize that you lose torque and some of that seat of your pants acceleration because the car is moving along easier with the higher gear ratio. However, I am also at 6000' and I am wondering if the car is losing additional torque due to the loss of oxygen. meaning when approaching high RPM it is more effected by the loss of oxygen then the 3.42. It is a stock engine with an A&A kit. It just doesn't seem as fast as it used or should. It dynoed at 500RWHP at sea level. I estimate 425-450RPM at 6000'.
Any help is appreciated.
I did another post a while back asking about torque loss from going from a 3.42 to a 3.90 with a 6 speed. I realize that you lose torque and some of that seat of your pants acceleration because the car is moving along easier with the higher gear ratio. However, I am also at 6000' and I am wondering if the car is losing additional torque due to the loss of oxygen. meaning when approaching high RPM it is more effected by the loss of oxygen then the 3.42. It is a stock engine with an A&A kit. It just doesn't seem as fast as it used or should. It dynoed at 500RWHP at sea level. I estimate 425-450RPM at 6000'.
Any help is appreciated.
Racer
Joined: Jan 2010
Posts: 360
Likes: 0
That is a significant elevation difference
expect aprox .5psi drop for every 1000' of elevation
That is 3lbs - roughly 75whp - you most definately will notice that seat of the pants.
The solution = pully that bitch down some more to make the additional boost you want
As for gearing change - I personally would not consider going deeper than 3:42
expect aprox .5psi drop for every 1000' of elevation
That is 3lbs - roughly 75whp - you most definately will notice that seat of the pants.
The solution = pully that bitch down some more to make the additional boost you want
As for gearing change - I personally would not consider going deeper than 3:42
Last edited by 2bridges; Sep 26, 2012 at 08:18 PM.
Le Mans Master
Joined: Apr 2001
Posts: 5,479
Likes: 718
From: Black Forest CO
You lose a huge amount of power at altitude. The rule of thumb is 3% per 1000 feet. I live at 7350 feet and the power difference between here and sea level is amazing.
Part of the problem is that you make less boost at altitude. When I had a SC on my car it made 8psi in Tempe but only 6.5psi here.
Part of the problem is that you make less boost at altitude. When I had a SC on my car it made 8psi in Tempe but only 6.5psi here.
Last edited by 7LitreC5; Sep 26, 2012 at 08:58 PM.
