Performance at altitude?
06-14-2019, 07:50 PM
#1
Racer
Thread Starter
Performance at altitude?
I have a 2009 Turbo. I mostly live in Baltimore where I am very happy with its performance. I am in Denver this summer where I noticed, unsurprisingly, a drop off in performance given the mile-high altitude. I was talking to a mechanic I know, and he said there may be some software to improve altitude performance. Anyone heard of such a thing and where I might find it?
06-14-2019, 09:18 PM
#2
Rennlist Member
You think you had a drop off? Try a non turbo car once if you think you have a drop off in performance at altitude.
06-14-2019, 09:23 PM
#3
Racer
Thread Starter
06-15-2019, 04:12 AM
#5
Were you being aggressive enough with the throttle?
With a turbocharged engine you should develop the full power of the engine or very near there regardless of altitude (unless we're flying). Your turbochargers should be able to compensate for the altitude change but that only works when they're working which they won't be unless you're driving aggressively.
10PSI is 10PSI (or whatever the CTT turbo's boost to) at sea level or at 10,000ft above it.
With a turbocharged engine you should develop the full power of the engine or very near there regardless of altitude (unless we're flying). Your turbochargers should be able to compensate for the altitude change but that only works when they're working which they won't be unless you're driving aggressively.
10PSI is 10PSI (or whatever the CTT turbo's boost to) at sea level or at 10,000ft above it.
06-15-2019, 03:37 PM
#6
Burning Brakes
Were you being aggressive enough with the throttle?
With a turbocharged engine you should develop the full power of the engine or very near there regardless of altitude (unless we're flying). Your turbochargers should be able to compensate for the altitude change but that only works when they're working which they won't be unless you're driving aggressively.
10PSI is 10PSI (or whatever the CTT turbo's boost to) at sea level or at 10,000ft above it.
With a turbocharged engine you should develop the full power of the engine or very near there regardless of altitude (unless we're flying). Your turbochargers should be able to compensate for the altitude change but that only works when they're working which they won't be unless you're driving aggressively.
10PSI is 10PSI (or whatever the CTT turbo's boost to) at sea level or at 10,000ft above it.
Say altitude is 6000 feet, and atmospheric pressue there is 12 psi vs. 15 psi at sea level (14.7, I know, but to simplify ...).
So a normally aspirated engine at WOT would only be able to take in 80% of the air (12/15) that it normally does = a 20% drop in power + torque. No way around it.
With a turbo set to max at 10 psi gauge pressure (taking your number since it's easy to work with; no idea what the exact value is), at sea level, it would be sending 15+10=25 psi air into the engine. At altitude, if it still limits to +10 psi, it would be sending 12+10 = 22 psi air in. So that's a (25-22)/25 = 3/25 = 12% drop in power + torque. Surely enough to register on most butt dynos. And I think if it had a mechanical wastegate from back in the day, there would be no way around that.
But if the turbo could detect the reduced atmospheric pressure and increase the max boost to +13 psi, it would still have 12+13=25 psi, so no power loss.
Do these turbos do this? I have no idea.
06-15-2019, 03:56 PM
#7
Not the proper logic re. turbos and altitude. At 7000 feet, air density and exhaust density are 20% lower than sea level so there is a 20% power loss. A turbo at sea level that produces 20 psi would have to spin much faster at 7000 feet for the engine to receive 20 psi that it receives at sea level. Turbos dont typically push 20% more air at 7000 feet than at sea level so turbos do experience power loss at altitude, all things being equal. If you use a larger and/or faster spinning turbo at 7000 feet you can produce the same power produced at sea level. OR, if the vehicle has more turbo than it needs at sea level and there is a waste gate, it MAY be possible for THAT sort of turbo setup to produce the same power at sea level and 7000 feet. Superchargers have to work the same way. There is a drag strip near Denver... they run the superchargers faster to get the same internal pressures in the combustion chambers that they get at sea level.
Turbos in production cars typically wont prevent power loss at altitude. But they do have LESS power loss than NA engines at the same altitudes. Turbos for race vehicles can be configured with a waste gate that simply opens at the same pressure at any altitude COULD theoretically produce the same power at any altitude, though the turbo would have to be quite a bit larger than production car turbos... and have an adjustable waste gate.
Turbos in production cars typically wont prevent power loss at altitude. But they do have LESS power loss than NA engines at the same altitudes. Turbos for race vehicles can be configured with a waste gate that simply opens at the same pressure at any altitude COULD theoretically produce the same power at any altitude, though the turbo would have to be quite a bit larger than production car turbos... and have an adjustable waste gate.
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06-15-2019, 08:34 PM
#8
Burning Brakes
Lots of variables. Seems to me that the boost is likely relative; it will be 10 PSI (max) above absolute barometric pressure. But the delta P at lower atmospheric pressure should make the turbo more efficient in Denver than at sea level. Maybe the ECU adjusts fuel/air mix that affect power at altitude too. I know that.after living at higher elevation with a few turbo cars, I'll never have a naturally aspirated engine again.
Here's what Borg-Warner; a significant turbo mfr, says:
"The high-altitude performance of a turbocharged engine is significantly better. Because of the lower air pressure at high altitudes, the power loss of a naturally aspirated engine is considerable. In contrast, the performance of the turbine improves at altitude as a result of the greater pressure difference between the virtually constant pressure upstream of the turbine and the lower ambient pressure at outlet. The lower air density at the compressor inlet is largely equalized. Hence, the engine has barely any power loss."
Here's what Borg-Warner; a significant turbo mfr, says:
"The high-altitude performance of a turbocharged engine is significantly better. Because of the lower air pressure at high altitudes, the power loss of a naturally aspirated engine is considerable. In contrast, the performance of the turbine improves at altitude as a result of the greater pressure difference between the virtually constant pressure upstream of the turbine and the lower ambient pressure at outlet. The lower air density at the compressor inlet is largely equalized. Hence, the engine has barely any power loss."
06-15-2019, 10:03 PM
#9
Consider the source, they have a spin that always favors their position. The fact remains that if a turbo is spinning 100,000 RPM at sea level at peak boost, at 7000 feet the turbo has to spin at 120,000 rpm to produce the same combustion chamber pressure that is produced at sea level---thats the only way a turbo at altitude can produce the same power as a turbo at sea level. It also means that if the turbo cannot spin faster than 100,000 rpm at 7000 feet, you are GOING to lose power in spite of a turbo being present. Atmospheric pressure is about 20% less at 7000 feet... to make the same horsepower at 7000 feet and sea level, the turbo has to feed 20% more air at 7000 feet. To do that, the turbo has to spin faster than it spins at sea level... not something that is common or easy. Otherwise the turbo has to be at least 20% too big for the job at sea level with a waste gate to prevent overboost. At 7000 feet, the waste gate might never open. Superchargers have the same issue... if they dont run 20% faster to flow 20% more air, there will be a power loss. How much power loss is the question... most turbo engines do have somewhat more boost capability than they need or use at sea level. So a turbo vehicle at higher altitude might lose 5% to 10% compared to normally aspirated engines that will lose 20% of their power at 7000 feet.
Atmosphere at 7000 feet is about 20% less dense than at sea level... so turbos or superchargers have to spin 20% faster (or whatever the final calculation is, it might be 21% or 22% more to cover losses) to push 20% more air into the engine to keep the same performance as sea level. Most (all?) production turbo/super charged cars wont do that. Every race vehicle with turbo or super charging WILL produce sea level pressure at essentially any altitude up to 14,100 feet (Pikes Peak summit).
There is a hidden problem for engines that CAN produce 20% more boost at 7000 feet... at those altitudes, fuel is reformulated to provide proper flame front propagation at higher altitudes---in normally aspirated engines. When you fuel up at 7000 feet, the octane options will be 85, 87, and 89. If your engine requires 91 octane or higher (Euro octane numbers are higher than US octane numbers) AND it produces as much boost at altitude as it does at sea level, the engine computer MUST retard ignition timing significantly if you are forced to run 89 octane fuel at high altitude. That retarded timing will cause a power loss also. You'd need to find racing fuel to get full power at 7000 feet from a vehicle with full boost available at 7000 feet.
Atmosphere at 7000 feet is about 20% less dense than at sea level... so turbos or superchargers have to spin 20% faster (or whatever the final calculation is, it might be 21% or 22% more to cover losses) to push 20% more air into the engine to keep the same performance as sea level. Most (all?) production turbo/super charged cars wont do that. Every race vehicle with turbo or super charging WILL produce sea level pressure at essentially any altitude up to 14,100 feet (Pikes Peak summit).
There is a hidden problem for engines that CAN produce 20% more boost at 7000 feet... at those altitudes, fuel is reformulated to provide proper flame front propagation at higher altitudes---in normally aspirated engines. When you fuel up at 7000 feet, the octane options will be 85, 87, and 89. If your engine requires 91 octane or higher (Euro octane numbers are higher than US octane numbers) AND it produces as much boost at altitude as it does at sea level, the engine computer MUST retard ignition timing significantly if you are forced to run 89 octane fuel at high altitude. That retarded timing will cause a power loss also. You'd need to find racing fuel to get full power at 7000 feet from a vehicle with full boost available at 7000 feet.
06-16-2019, 11:11 AM
#10
Burning Brakes
Maybe the ECU adjusts fuel/air mix that affect power at altitude too.
The wastegates open at the preset psi no matter what elevation you're at, and the turbos have more than enough capacity to reach that pressure. I guess the tiny turbos being used on cars these days (that only give a ~20% increase in hp) may be maxed out at a normal elevation.
06-16-2019, 03:37 PM
#11
I've driven my 2004 Turbo to the top of Pikes Peak at over 14,000 ft.
A turbo will compensate and lose much less power than a Normally Aspirated car or a supercharged car (fixed rpm, can't spin faster like a turbo).
You might feel some power loss, but it'll still be doing much better than the other cars!
A turbo will compensate and lose much less power than a Normally Aspirated car or a supercharged car (fixed rpm, can't spin faster like a turbo).
You might feel some power loss, but it'll still be doing much better than the other cars!
06-20-2019, 06:27 PM
#14
having driven an NA explorer and a ecoboost explorer up pikes with 5 adults... the turbocharged ecoboost certainly has far less struggle bus tendency.
the N/A was gasping for air at about the tree line with 5 adults.
the N/A was gasping for air at about the tree line with 5 adults.
06-21-2019, 12:53 PM
#15
You can chip the car, would give more power. There look to be several options
https://flat6motorsports.com/product...enne-turbo-957
https://www.vividracing.com/tuned-ec...150773655.html
https://www.sharkwerks.com/software-...-turbo-EVOF188
https://www.fabspeed.com/porsche-957...peed-ecu-tune/
All look to boost HP and TQ from stock to about 570ish hp and 600 TQ
https://flat6motorsports.com/product...enne-turbo-957
https://www.vividracing.com/tuned-ec...150773655.html
https://www.sharkwerks.com/software-...-turbo-EVOF188
https://www.fabspeed.com/porsche-957...peed-ecu-tune/
All look to boost HP and TQ from stock to about 570ish hp and 600 TQ