Premium vs Regular gas?

[timfromma]

I can say with 100% honesty that I've done over 10,000 miles of towing this year and have not used a single drop of gasoline except in my generator.

[mopwr4me2003]

Diesel guy lol ☝️[emoji16]

[Arctic Wolf]

Originally Posted by Hersbird

Ok, I got you. I thought you were disputing the fact turbos handle altitude better than natural aspiration.

That's what I thought too.
The whole reason turbos were invented was to compensate for altitude on aircraft engines.

The air, pressurized to whatever PSI the computer allows is just as dense at sea level as it is at 20,000 feet... in absolute pressure, not gauge pressure. The engine doesn't know how high it is because the turbo is pushing the air in, rather than just allowing atmospheric pressure to push it in.
In theory the charge air cooler should keep a consistent air temperature, not sure how well it works in reality though.
Just my $.02

[babock]

Originally Posted by Arctic Wolf

That's what I thought too.
The whole reason turbos were invented was to compensate for altitude on aircraft engines.

The air, pressurized to whatever PSI the computer allows is just as dense at sea level as it is at 20,000 feet... in absolute pressure, not gauge pressure. The engine doesn't know how high it is because the turbo is pushing the air in, rather than just allowing atmospheric pressure to push it in.
In theory the charge air cooler should keep a consistent air temperature, not sure how well it works in reality though.
Just my $.02

The reality is that the ECU never allows the turbo to provide enough boost to full compensate.

[Arctic Wolf]

Originally Posted by babock

The reality is that the ECU never allows the turbo to provide enough boost to full compensate.

The ECU allows whatever manifold pressure it's programmed to, regardless of atmospheric pressure.
As I understand it.

[babock]

Originally Posted by Arctic Wolf

The ECU allows whatever manifold pressure it's programmed to, regardless of atmospheric pressure.
As I understand it.

It is until the heat generated causes the ECU to pull it back which is what happens at high altitude conditions.

[Arctic Wolf]

Ok, that makes sense. So the increased adiabatic heating from compressing less air at high altitude overloads the CAC and causes the ECU to derate the engine? Interesting. Just when you need it most the computer takes away power.

[Hersbird]

Now I sort of have to disagree on the turbo boost, elevation and what the ECU allows, at least on my turbo a 2004.5 Cummins. On my motor boost is mechanically limited at about 30psi at the wastegate. There is no connection to the ECU at all. The ECU knows the boost via only the MAP sensor. So it will see 14.7 Absolute pressue at sea level or zero boost. At elevation it sees say 14 Absolute or -.5 boost but when spun up at either sea level or altitude it sees 47.7 psi absolute at the MAP sensor basically it has no idea what elevation it is at. Now it may after time start to see a rise in the IAT and start to lower power but at least on the Cummins the intercooler is sized to handle it. I can monitor my IAT so maybe next time I will watch it and see if it is greatly different at altitude compared with home. I have a feeling because it is inherently cooler outside at higher elevations if anything it will be cooler even though the turbo is working a little more.

[Arctic Wolf]

Originally Posted by Hersbird

Now I sort of have to disagree on the turbo boost, elevation and what the ECU allows, at least on my turbo a 2004.5 Cummins. On my motor boost is mechanically limited at about 30psi at the wastegate. There is no connection to the ECU at all. The ECU knows the boost via only the MAP sensor. So it will see 14.7 Absolute pressue at sea level or zero boost. At elevation it sees say 14 Absolute or -.5 boost but when spun up at either sea level or altitude it sees 47.7 psi absolute at the MAP sensor basically it has no idea what elevation it is at. Now it may after time start to see a rise in the IAT and start to lower power but at least on the Cummins the intercooler is sized to handle it. I can monitor my IAT so maybe next time I will watch it and see if it is greatly different at altitude compared with home. I have a feeling because it is inherently cooler outside at higher elevations if anything it will be cooler even though the turbo is working a little more.

Yup.
And in computer controller engines like the 6.7 Cummins the computer sets manifold pressure, not boost. So 45 psi is 45 psi, the engine doesn't know what it's altitude is.
Some say "there is less oxygen at higher altitude" this isn't true. Air is roughly 21% oxygen, at Sea level or at altitude. What changes is atmospheric pressure, there is less air above you at altitude, sort of like when you dive down under the water, the pressure increases as you go deeper.
Normally aspirated engines do not "suck" air in... It is pushed by atmospheric pressure (the weight of the air above us).
With forced induction, we use a machine to create that pressure, and with computer controls we can maintain manifold pressure at a constant level.
At higher altitude, the turbo actually spins faster (to create the same pressure) due to it doing less work, similar to how a vacuum cleaner speeds up when you block the inlet hose.

[Hersbird]

I also apologize in advance to babock as he isn't making an argument against boost and only talking about octain rating. I admit I know little compared to him as to when a motor starts detonation and needs computer changes based on all the parameters. Heck diesel only has an octain of like 15 LOL! You want it to detonate. It does bring up another thought on the use of E85 with an octain rating of 115. The Michigan State Police vehicle testing sure shows those cars are quicker and have a higher top speed running E85 if designed to allow it. They may use more of it per mile but they make a bunch more power with that moonshine.

[Arctic Wolf]

Diesel doesn't have "octane" it had a cetane rating, completely different stuff.
The higher the octane rating the slower the gas burns, and the more resistant to detonation it is, allowing more boost, or higher compression ratio, or more spark advance.

[Hersbird]

Originally Posted by Arctic Wolf

Diesel doesn't have "octane" it had a cetane rating, completely different stuff.
The higher the octane rating the slower the gas burns, and the more resistant to detonation it is, allowing more boost, or higher compression ratio, or more spark advance.

Every fuel can be rated in octane and if you rate diesel it is about 15. You can also rate the cetane of gasoline but I admit octane in diesel and cetane in gasoline are kind of meaningless numbers. It does show you the difference how a diesel works, you want it to self ignite where in a gas motor you want the spark to control when ignition happens.

[Arctic Wolf]

Originally Posted by Hersbird

Every fuel can be rated in octane and if you rate diesel it is about 15. You can also rate the cetane of gasoline but I admit octane in diesel and cetane in gasoline are kind of meaningless numbers. It does show you the difference how a diesel works, you want it to self ignite where in a gas motor you want the spark to control when ignition happens.

Point taken.