Forum Discussion
ShinerBock wrote:
4x4ord wrote:
If the GM had performed the way it should have people would have making excuses for why the Ford took so long getting to the top. Probably someone would have been blaming the turbo.
That is probably because the turbo and intake system plays a huge factor in how much power a diesel can make and sustain. If you put different turbos on the exact same engine/drivetrain and take it up the Ike, the results may be vastly different depending on how diverse the turbos and the intake systems are.
What I'm getting at is had the GM not had issues it would have run up the mountain in under 10 minutes. It really should have beaten the Ford. Had that happened fingers would have been pointing at why Ford's 475 HP engine couldn't keep up with a 445 hp Duramax.4x4ord wrote:
If the GM had performed the way it should have people would have making excuses for why the Ford took so long getting to the top. Probably someone would have been blaming the turbo.
That is probably because the turbo and intake system plays a huge factor in how much power a diesel can make and sustain. If you put different turbos on the exact same engine/drivetrain and take it up the Ike, the results may be vastly different depending on how diverse the turbos and the intake systems are.4x4ord wrote:
If the GM had performed the way it should have people would have making excuses for why the Ford took so long getting to the top. Probably someone would have been blaming the turbo.
Significant changes will have to happen to make up a 1:27 deficit.ShinerBock wrote:
FishOnOne wrote:
ShinerBock wrote:
^^^That is not how turbos work. Air density, blade profile, A/R ratio, flow, blade size and other things dictate how much power a turbocharged engine looses at altitude. Turbo shaft speed generally increases with altitude to compensate for the decrease in air density. Bigger turbo wheels that make a lot of power cannot spool as fast as a smaller turbo wheel. So generally a smaller turbo that is at its max potential at sea level will do better at altitude than a larger turbo.
Also, tuners do not often push turbos way past their efficiency zones, at least not a good one. If you go past the turbos efficiency zone then you start making less power and higher EGT's which is not what you want so to make the best gains you have to stay withing the turbo's efficiency. A tuner will generally keep adding fuel and timing until they start to see power numbers start to decrease with excessive EGT's. That is the point where they know the turbo is leaving it's efficiency zone and a bigger turbo is needed to make more power so they back the fuel and timing back down to where it made more power. Diesels are regulated by fuel and not air like gas engines.
The 11-14 power strokes had small dia turbo and was the reason for less performance at altitude. Then came 15 2nd gen engines with larger turbo to improve altitude performance
I guess physics are wrong then.....
The better performance from the 15 was likely due to the single VGT setup allowing the turbo adjust for altitude and having more space for a better blade profile allowing it to chop through the thinner air better. In 2015, they went with a single VGT and then to a sequential a in 2017-2019. Then went back to single VGT in 2020. The years they have a single VGT they do better on the ike than the years they have the sequential setup because of this. Another aspect of the 2011-2014 turbos is that they were waste-gated to keep the turbo from overspeeding while the 2015 was not.
Not challenging any physics but simply passing along what a recall reading about the change to improve altitude performance- If the GM had performed the way it should have people would have making excuses for why the Ford took so long getting to the top. Probably someone would have been blaming the turbo.
FishOnOne wrote:
ShinerBock wrote:
^^^That is not how turbos work. Air density, blade profile, A/R ratio, flow, blade size and other things dictate how much power a turbocharged engine looses at altitude. Turbo shaft speed generally increases with altitude to compensate for the decrease in air density. Bigger turbo wheels that make a lot of power cannot spool as fast as a smaller turbo wheel. So generally a smaller turbo that is at its max potential at sea level will do better at altitude than a larger turbo.
Also, tuners do not often push turbos way past their efficiency zones, at least not a good one. If you go past the turbos efficiency zone then you start making less power and higher EGT's which is not what you want so to make the best gains you have to stay withing the turbo's efficiency. A tuner will generally keep adding fuel and timing until they start to see power numbers start to decrease with excessive EGT's. That is the point where they know the turbo is leaving it's efficiency zone and a bigger turbo is needed to make more power so they back the fuel and timing back down to where it made more power. Diesels are regulated by fuel and not air like gas engines.
The 11-14 power strokes had small dia turbo and was the reason for less performance at altitude. Then came 15 2nd gen engines with larger turbo to improve altitude performance
I guess physics are wrong then.....
The better performance from the 15 was likely due to the single VGT setup allowing the turbo adjust for altitude and having more space for a better blade profile allowing it to chop through the thinner air better. In 2015, they went with a single VGT and then to a sequential a in 2017-2019. Then went back to single VGT in 2020. The years they have a single VGT they do better on the ike than the years they have the sequential setup because of this. Another aspect of the 2011-2014 turbos is that they were waste-gated to keep the turbo from overspeeding while the 2015 was not.ShinerBock wrote:
^^^That is not how turbos work. Air density, blade profile, A/R ratio, flow, blade size and other things dictate how much power a turbocharged engine looses at altitude. Turbo shaft speed generally increases with altitude to compensate for the decrease in air density. Bigger turbo wheels that make a lot of power cannot spool as fast as a smaller turbo wheel. So generally a smaller turbo that is at its max potential at sea level will do better at altitude than a larger turbo.
Also, tuners do not often push turbos way past their efficiency zones, at least not a good one. If you go past the turbos efficiency zone then you start making less power and higher EGT's which is not what you want so to make the best gains you have to stay withing the turbo's efficiency. A tuner will generally keep adding fuel and timing until they start to see power numbers start to decrease with excessive EGT's. That is the point where they know the turbo is leaving it's efficiency zone and a bigger turbo is needed to make more power so they back the fuel and timing back down to where it made more power. Diesels are regulated by fuel and not air like gas engines.
The 11-14 power strokes had small dia turbo and was the reason for less performance at altitude. Then came 15 2nd gen engines with larger turbo to improve altitude performance- Double Post
- ^^^That is not how turbos work. Air density, blade profile, A/R ratio, flow, blade size and other things dictate how much power a turbocharged engine looses at altitude. Turbo shaft speed generally increases with altitude to compensate for the decrease in air density. Bigger turbo wheels that make a lot of power cannot spool as fast as a smaller turbo wheel. So generally a smaller turbo that is at its max potential at sea level will do better at altitude than a larger turbo.
Also, tuners do not often push turbos way past their efficiency zones, at least not a good one. If you go past the turbos efficiency zone then you start making less power and higher EGT's which is not what you want so to make the best gains you have to stay withing the turbo's efficiency. A tuner will generally keep adding fuel and timing until they start to see power numbers start to decrease with excessive EGT's. That is the point where they know the turbo is leaving it's efficiency zone and a bigger turbo is needed to make more power so they back the fuel and timing back down to where it made more power. Diesels are regulated by fuel and not air like gas engines. 4x4ord wrote:
Is that dyno sheet from the actual truck that they used in the towing test? It seems as though it's not just an isolated truck. I thought the reason the Duramax they put up against the Ram failed to perform better might have been on account of the shift points programmed into the Alison transmission, but,after seeing the high rpms used in this run up the mountain I recognize that the Alison is tuned to aggressively use the high end of the power curve. It seems strange to tune the transmission to run high engine rpm if there is no additional power to be has there.
Not the actual truck for this test, but a previous one in 2017, where the 445hp Duramax failed to beat a 385hp rated Cummins.
The reason I feel this is elevation choked, is because Gale Banks has a nice series of video "killing a duramax", which he showed the turbo parameters being nearly maxed out to produce the rated 445 hp.
Therefore at elevation, the turbo has nothing left, and power output suffers starting at such an early RPM. Tuners often push the turbo way past its efficient zones on the compressor map, shortening the life.
I bet at sea level the engine hp will keep climbing after 2500 rpm.
