How much Altitude change allowed before retune?
03-07-2010, 08:12 PM
#1
TECH Veteran
Thread Starter
iTrader: (14)
Join Date: Apr 2005
Location: N. Falmouth MA
Posts: 4,085
Likes: 0
Received 0 Likes
on
0 Posts
How much Altitude change allowed before retune? I got my car dyno'd @ TSP 31 Oct 2008. That was at about 3800ft elevation, now I moved back to CT at around sea level to about 500ft. How much altitude change is allowed or tolerated before a re-tune is needed?
Was wondering if I picked up any HP from the drop in altitude.
Was wondering if I picked up any HP from the drop in altitude.
03-08-2010, 07:22 AM
#4
TECH Veteran
Thread Starter
iTrader: (14)
Join Date: Apr 2005
Location: N. Falmouth MA
Posts: 4,085
Likes: 0
Received 0 Likes
on
0 Posts
^ Sweet. I think I'll have it dyno'd and have him run a data log on it to see if there could be some room for improvement. Gonna go to ESP maybe next week.
03-09-2010, 01:09 AM
#5
TECH Enthusiast
iTrader: (1)
Join Date: Dec 2005
Location: Denver International Airport, Colorado USA
Posts: 549
Likes: 0
Received 0 Likes
on
0 Posts
About a 3% gain/loss in 'real' HP for very 1000' feet (up or down) in elevation you go.
Now if your dyno was SAE, it should read the same (they adjust for pressure). But your car will be stronger by at least ~10% in uncorrected HP..I.E. faster.
Re-tune..Your MAP sensor is essentially a barometer, and MAF is good at picking up density changes. Sometimes though your Trims can alter. Whether you actually see that persist is debatable. If you can 'cheaply' dyno-tune it again, it never hurts. Sometimes your WOT and AFR requirements can change.
For me, I have had the opposite problem (going up in elevation). So even though all your sensors do handle the change, you do have differing cylinder pressures with altitude change..I might not spend $500-$600 buck for a re-tune, but take a moderate approach just to check.
Good luck.
Now if your dyno was SAE, it should read the same (they adjust for pressure). But your car will be stronger by at least ~10% in uncorrected HP..I.E. faster.
Re-tune..Your MAP sensor is essentially a barometer, and MAF is good at picking up density changes. Sometimes though your Trims can alter. Whether you actually see that persist is debatable. If you can 'cheaply' dyno-tune it again, it never hurts. Sometimes your WOT and AFR requirements can change.
For me, I have had the opposite problem (going up in elevation). So even though all your sensors do handle the change, you do have differing cylinder pressures with altitude change..I might not spend $500-$600 buck for a re-tune, but take a moderate approach just to check.
Good luck.
