EcoBoost boost at altitude, absolute vs. relative pressure?
01-09-2012, 01:51 PM
#22
Senior Member
Yes The boost pressure is messured with a map sensor which compares the pressure to a fixed spring pressure so the ambiant[outside] air pressure has no effect on boost level in the manifold so in affect elevation has no efect on boost as long as the turbos can gather enough air.in most non aircraft engines this is good to about14,000 ft before you will see a drop in manifold pressure if the turbos are sized right.bubbabud
01-09-2012, 02:29 PM
#23
Turbos in automotive applications generally provide a constant level of boost regardless of elevation, to a point. So the turbo is set to provide 10psi boost via the controller, it will maintain that 10psi. So at sea level, on a standard day, the absolute pressure would be 24.7 psi, at 10,000 feet it would be 20.06 psi. Of course as the air gets thinner, the turbo has to spin faster to move enough air to produce that much boost, so you may start seeing a drop in performance once the turbo starts reaching its operating limits.
Turbochargers in aviation applications are set up to maintain the set manifold pressure up to a certain altitude. They aren't there to increase the power output of the engine per se, but rather to maintain engine performance at higher altitudes.
Absolute and relative are just two ways of measuring the boost. Absolute is ambient pressure plus boost, relative pressure is what you would read off of a boost gauge.
Turbochargers in aviation applications are set up to maintain the set manifold pressure up to a certain altitude. They aren't there to increase the power output of the engine per se, but rather to maintain engine performance at higher altitudes.
Absolute and relative are just two ways of measuring the boost. Absolute is ambient pressure plus boost, relative pressure is what you would read off of a boost gauge.
01-09-2012, 05:02 PM
#24
locking out the top three gears made my drive much more enjoyable - and didn't suck much more fuel (these are 30-40mph roads, tops)
01-09-2012, 10:48 PM
#25
Senior Member
Thread Starter
I was the OP of this thread...
First off, just to get it out of the way, I LOVE my EcoBoost engine. IMHO, hands down the best engine Ford currently offers in the F150, especially at altitude!
With more miles under my belt (~9,000, almost all at high elevation), a mechanical boost gauge in the truck, and reading about the experience of others, I release my initial question was a bit simplistic.
Here's why: Ford continually "manages" boost pressure far more than any other turbo engine I've ever seen. The PCU is constantly tweaking boost pressure based on tons of input. How close to a shift point is it? Whats the ambient temperature? Intake air temperature? Barometric pressure? Throttle position? Current speed? Tow/haul mode set? And I speculate lots of additional data parameters floating around on the CAN bus. I would love to see Ford's algorithms for managing boost, but I'm sure Ford protects all the details as proprietary information
With a mechanical boost gauge, you can really see Ford's management in action, and I have no doubt that barometric pressure (which is lower at higher altitude) is factored in. I wouldn't be at all surprised if all this boost management is why Ford decided NOT to put a boost gauge in the truck! WAY too confusing for the average get in, turn the key, press the pedal kind of driver.
So is complex boost management bad? I don't think so... While I'd love to have the extra power, Ford's constant tweaking of boost likely provides a much smoother, less "turbo-like" driving experience. Better for the majority of drivers out there. And considering how many of even the "enthusiasts" on this forum gripe about MPG's instead of raving about power, Ford read their customer base correctly.
And for the true performance minded gearhead? Aftermarket tunes!
First off, just to get it out of the way, I LOVE my EcoBoost engine. IMHO, hands down the best engine Ford currently offers in the F150, especially at altitude!
With more miles under my belt (~9,000, almost all at high elevation), a mechanical boost gauge in the truck, and reading about the experience of others, I release my initial question was a bit simplistic.
Here's why: Ford continually "manages" boost pressure far more than any other turbo engine I've ever seen. The PCU is constantly tweaking boost pressure based on tons of input. How close to a shift point is it? Whats the ambient temperature? Intake air temperature? Barometric pressure? Throttle position? Current speed? Tow/haul mode set? And I speculate lots of additional data parameters floating around on the CAN bus. I would love to see Ford's algorithms for managing boost, but I'm sure Ford protects all the details as proprietary information
With a mechanical boost gauge, you can really see Ford's management in action, and I have no doubt that barometric pressure (which is lower at higher altitude) is factored in. I wouldn't be at all surprised if all this boost management is why Ford decided NOT to put a boost gauge in the truck! WAY too confusing for the average get in, turn the key, press the pedal kind of driver.
So is complex boost management bad? I don't think so... While I'd love to have the extra power, Ford's constant tweaking of boost likely provides a much smoother, less "turbo-like" driving experience. Better for the majority of drivers out there. And considering how many of even the "enthusiasts" on this forum gripe about MPG's instead of raving about power, Ford read their customer base correctly.
And for the true performance minded gearhead? Aftermarket tunes!
Last edited by pfbz; 01-09-2012 at 10:54 PM.
01-09-2012, 10:57 PM
#26
Senior Member
Thread Starter
i did the same thing running through the hills (just left 10,000' and the mountains two weeks ago) - the speed dictated that it was 3rd gear in order to not have the transmission hunting constantly. 4th is fine going down the hill, but 1100rpm doesn't work when its a 10-15% grade for a short distance so it would constantly shift.
locking out the top three gears made my drive much more enjoyable - and didn't suck much more fuel (these are 30-40mph roads, tops)
locking out the top three gears made my drive much more enjoyable - and didn't suck much more fuel (these are 30-40mph roads, tops)
04-30-2016, 11:45 PM
#27
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EcoBoost
I was searching for something else when I ran across this thread and thought I'd give my $0.02.
I have a 2015 Fusion with the 2.0L EcoBoost. I had connected an OBD-II monitor to figure out what the turbo was doing, and to read some other information after I had bought the car.
With the engine off, the MAP recording would be about 12.3 psi, indicating absolute pressure for Colorado. With the engine warmed up and at night, the MAP would record about 32 psi total (the 2.0L EcoBoost is supposed to be an 18 psi turbo), indicating the computer is compensating for altitude.
In warmer air, the max boost was kept around 30 psi for the few times I looked at full throttle.
I have a 2015 Fusion with the 2.0L EcoBoost. I had connected an OBD-II monitor to figure out what the turbo was doing, and to read some other information after I had bought the car.
With the engine off, the MAP recording would be about 12.3 psi, indicating absolute pressure for Colorado. With the engine warmed up and at night, the MAP would record about 32 psi total (the 2.0L EcoBoost is supposed to be an 18 psi turbo), indicating the computer is compensating for altitude.
In warmer air, the max boost was kept around 30 psi for the few times I looked at full throttle.
05-01-2016, 12:59 AM
#28
Senior Member
The wiring diagram for the 2011 shows 2 IAT and one MAP sensor. One IAT is combined with the MAP. There is also a turbo boost pressure sensor.
Compensating for elevation is possible of the turbos are big enough. If they are limited to 15 psi at sea level, then they will have to produce 2.5 more psi at 5,000 ft. At some altitude, they will run out of capacity. That altitude depends on design. Keep in mind though that at higher altitudes there is LESS air for things like cooling your engine, transmission, axle and anything else that generates heat. So if it compensates for altitude, you run more risk of overheating. It also puts more stress on the ignition system as lower pressure requires less voltage to jump a spark. Turbocharged piston aircraft have pressurized magnetos for this reason. We do not have distributors but we do have an ignition system.
Compensating for elevation is possible of the turbos are big enough. If they are limited to 15 psi at sea level, then they will have to produce 2.5 more psi at 5,000 ft. At some altitude, they will run out of capacity. That altitude depends on design. Keep in mind though that at higher altitudes there is LESS air for things like cooling your engine, transmission, axle and anything else that generates heat. So if it compensates for altitude, you run more risk of overheating. It also puts more stress on the ignition system as lower pressure requires less voltage to jump a spark. Turbocharged piston aircraft have pressurized magnetos for this reason. We do not have distributors but we do have an ignition system.
05-09-2016, 08:29 PM
#29
I'd really like to know more about how Ford's electronic boost control handles altitude...
On a simple mechanical boost controller, usually the waste-gate is triggered by the rise in manifold pressure vs. ambient pressure. Which means you would get perhaps a 15 PSI boost over whatever the ambient pressure is, so ~30 psi at sea level, about ~27 psi at a mile-high.
Ford and most OEM turbos surely use more modern electronic boost control. I'm sure they are looking at the MAP (Manifold Absolute Pressure) sensor, temperatures, throttle position, knock sensors, and a bunch of other variables in determining the boost pressure, and from what I hear, they adjust boost quite a bit. Those who have added boost gauges see it going all over the place, dumping boost at shift points, etc. It's been reported that people see about 15 psi as maximum boost.
My curiosity is really about maximum boost at altitude... Does the EcoBoost add additional boost at altitude to achieve the same absolute manifold pressure as would be obtained at sea level?
A standard aftermarket boost gauge would measure relative boost, not absolute pressure, so if Ford was doing this, you would see MORE than 15 psi on a boost gauge at altitude.
Any thoughts?
On a simple mechanical boost controller, usually the waste-gate is triggered by the rise in manifold pressure vs. ambient pressure. Which means you would get perhaps a 15 PSI boost over whatever the ambient pressure is, so ~30 psi at sea level, about ~27 psi at a mile-high.
Ford and most OEM turbos surely use more modern electronic boost control. I'm sure they are looking at the MAP (Manifold Absolute Pressure) sensor, temperatures, throttle position, knock sensors, and a bunch of other variables in determining the boost pressure, and from what I hear, they adjust boost quite a bit. Those who have added boost gauges see it going all over the place, dumping boost at shift points, etc. It's been reported that people see about 15 psi as maximum boost.
My curiosity is really about maximum boost at altitude... Does the EcoBoost add additional boost at altitude to achieve the same absolute manifold pressure as would be obtained at sea level?
A standard aftermarket boost gauge would measure relative boost, not absolute pressure, so if Ford was doing this, you would see MORE than 15 psi on a boost gauge at altitude.
Any thoughts?
As you gain altitude, you use more and more of the turbo's capability until you reach the altitude at which the max capability of the turbo has to be used to make the 15psi difference. Above that altitude, the turbo will be working as hard as it can, but the psi differential will continue to decline as you climb.
You're unlikely to hit that altitude on roads in the US, with the possible exceptions of Pike's Peak or some other very high mountain passes. I don't know enough about the specifications to estimate what that altitude is, and haven't seen it noted in the owner's manual.
11-07-2022, 12:29 AM
#30
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K2 Rocky ridge f150 2021
Beautiful inside and out!!! So dreamy!! If I could go back to the day I purchased it knowing what I do now, would I? NO! I've received recall after recall. Parts are very limited and long waits. Don't ever hit a deer! You'll be without for a long time!! Randomly shuts off on me while I'm driving with my 2 children on windy backroads of upstate ny.....brakes lock up and your power steering is gone. Everything is so computer based nowadays. Where's the trust!? I'd rather use my rear view mirror/side mirrors than a backup camera anytime anywhere. Newer isn't always better. And no I don't need to get with the time. My dream truck would be f150 early 90s bench seat 5 speed. Obviously for my own pleasure. Can't put 2 carseats in there. Even though I'd trust it more than my rocky ridge. Damn truck won't even register my back rear passenger seatbelt!!!