F350 Super Duty vs 3500 Denali vs The Ike Pulling 30k lbs

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.