Locking out gears

[dogboye]

Drive from Albuquerque to Durango.
Empty. No towing.
Set cruise control at whatever the speed limit is on HWY 550

Your Ecoboost (& Powerboost) 10r80 will definitely be in 10th at that speed.

Now watch your boost gauge at each incline. It will steadily climb to meet the torque request generated by cruise control expectations.

Now let's say it reaches ~7lbs
Manually downshift (lockout 10)
Immediately rpms increase, and boost decreases. Perhaps to 3lbs?

Drop to 8th. Rpms increase yet some more and boost might drop to 0lbs.

Remember, the Ecoboost is a torque management engine management system. It literally is interpreting the throttle position (or cruise control speed) into a mathematical torque request value. So when you downshifted, you increased the amount of torque that the engine was producing via rpms, so the pcm had no choice but to reduce the boost in use because it would otherwise be exceeding the torque request.

Torque management can take a bit to get your head around. It doesn't exactly reflect how we grew up thinking about the throttle being a command for more fuel.

But that's a digital command VS an analog/mechanical command.

All I can say is: <mind blown>
So it sounds like the turbos are always spinning, producing boost, even down low. At higher rpm, they're turning faster thus producing more boost. But it is being dumped by electronically controlled waste gates. Either that or there are valves that divert exhaust gas through or around the turbos, depending on torque needs.

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[HammaMan]

This entire discussion seems backward to me. And I see the numbers, so I believe it (well, I would believe it without seeing the numbers displayed). But I just don't understand how the Ecoboost (or Powerboost, for that matter) is getting/using turbos for torque if you keep the rpm low, but not if you use higher rpm by locking out gears. I always thought you needed high rpm to get usable boost from turbochargers.
But then you throw the Powerboost option with the ~100ft-lbs torque from the electric motor... and I don't know where it goes.
I think I need to read this entire thread a ... third... time.

The PB brings in the e-motor rather quickly in an attempt to stay out of boost to further its mileage. The issue comes from longer inclines where there just isn't enough juice in the batt to handle it (while it fills back up on the way down). Keep in mind there's torque multiplication through the gearbox, and the power to the ground is less in higher gears requiring more work of the motor. Downshifting not only requires less power from the engine to have the same effect at the ground, it also raises the RPMs higher into the powerband thus requiring less boost for the required power as the engine naturally produces more power at say 3k RPM than it does at 2.2k RPM. The goal is to avoid letting boost come in as fuel usage exponentially increases (vs power produced) as boost comes in. If you can make say 300hp at 3k RPM w/ no boost, or 300hp at 2.2k RPM w/ boost (just throwing out random numbers), the 3k RPM is going to use less fuel as it's made with a leaner burn.

The truck's programming is to be quiet (and not shift), not maximize efficiency. A true eco mode would hunt the appropriate gear vs allowing boost to come in. Just one illustration of how ford's so called eco mode, isn't. A true eco mode would avoid using boost where possible.

 

[HammaMan]

All I can say is: <mind blown>
So it sounds like the turbos are always spinning, producing boost, even down low. At higher rpm, they're turning faster thus producing more boost. But it is being dumped by electronically controlled waste gates. Either that or there are valves that divert exhaust gas through or around the turbos, depending on torque needs.

Don't confuse moving air for making boost. Boost occurs when the engine isn't able to eat all of the incoming air. When pressure increases, so too does the fuel needed to make the power, plus additional fuel that isn't fully burned in combustion and ends up getting consumed by the cats.

 

[dogboye]

Don't confuse moving air for making boost. Boost occurs when the engine isn't able to eat all of the incoming air. When pressure increases, so too does the fuel needed to make the power, plus additional fuel that isn't fully burned in combustion and ends up getting consumed by the cats.

No, I thought "boost" was the pressurized air on the compressor side of the spool, the engine intake side. Higher engine rpm produces more downstream mass flow, into the turbine side of the turbo, which spins the turbos faster, which produces more pressure on the compressor side, which then feeds into the engine, requiring more fuel because the intake air is denser. Which is where I though the intercoolers came in, to cool down the pressurized intake air that has a raised temperature due to the increased pressure.
So, not moving air. Pressurizing air. Which is why turbos are less affected by altitude than normally aspirated engines.

And that waste gates release pressure on the intake side when the compressor side pressurizes the air too much.

BUT... all my knowledge is old, outdated, and heavily influenced by turbine propulsion engineering.

[ETA: not trying to argue. Just trying to understand the scheme with the PB.]

 

[mxwrk]

Can someone just tell me if locking out 7-10 or 8-10 will get me better mileage driving from Orange County CA, to Santa Barbara CA? lolllll.

 

[Snakebitten]

Ahhhhh
Now I understand what is messing with your head.

Similar to yesterdecade engine management being analog, thus the throttle was a direct request for more fuel, the yesterdecade Turbo was being spooled up by exhaust and boost was determined by RPM increasing that velocity of exhaust.

The Turbos on the Ecoboost (and others very modern turbocharged engines) are managed very granularly by the pcm. And they are actually very small and can spool insanely quick with very little rpms needed to create the necessary exhaust.

Now return to the concept of torque management engine control. You push the accelerator with your foot.
There's nothing mechanically connected to the pedal. Literally fly by wire and mathematically converted into a request for a specific quantity of torque. (really cool when you think about it)

On the regular Ecoboost, the engine management has been "tuned" by Ford to produce that torque using the naturally aspirated (unboosted) capabilities of the 3.5 liters. Rpms and fuel.
But it also can tap the turbos for meeting the torque request if the request is beyond what the Normally Aspirated combustion can produce.

I know how obvious that might sound, but in the discussion regarding locking out gears, we are discussing the fact that the 3.5 Ecoboost can often meet the torque request without forced induction, as long as the transmission affords the necessary normally Aspirated rpms. If you lower those rpms with the gear ratio, then the Turbos are required to supplement the missing air necessary for the combustion chamber to meet the torque request.

Sorry if I'm going in circles. Lol

Those turbos aren't being spooled (relatively) unless the pcm calls on them to participate. If they aren't being called on, the exhaust isn't being used to compress/spool. And they are so small and efficient that if/when the pcm decides to include them in the torque request recipe, they spool QUICK!

 

[HammaMan]

No, I thought "boost" was the pressurized air on the compressor side of the spool, the engine intake side. Higher engine rpm produces more downstream mass flow, into the turbine side of the turbo, which spins the turbos faster, which produces more pressure on the compressor side, which then feeds into the engine, requiring more fuel because the intake air is denser. Which is where I though the intercoolers came in, to cool down the pressurized intake air that has a raised temperature due to the increased pressure.
So, not moving air. Pressurizing air. Which is why turbos are less affected by altitude than normally aspirated engines.

And that waste gates release pressure on the intake side when the compressor side pressurizes the air too much.

BUT... all my knowledge is old, outdated, and heavily influenced by turbine propulsion engineering.

[ETA: not trying to argue. Just trying to understand the scheme with the PB.]

Boost is really a function of 'struggle' as indicated by manifold pressure (or lackthereof). You can have an engine rev'n at 5k RPM still drawing vacuum. When this happens the exhaust is bypassing the turbo for the most part as the engine is not asking for it. If you're under load and the throttle is open and no vac. present in the manifold, the turbos know that power is being called for and thus generate boost. Today a lot of this is done by the computer as with electronic actuators it can build boost faster as well as ask for it sooner. It also allows for better control of how much boost is generated. The goal for good fuel economy on these engines is to stay out of boost as much as possible due to the rich conditions that occur when boost is built.

On the other hand if the engine is working hard and suddenly the throttle closes, the wastegates will open and the blow off will trigger to prevent a huge pressure spike that can break all sorts of things. Again electronically this can happen much faster than the traditional. The goal however is to stay out of boost, aka keep a healthy vacuum in the intake vs positive pressure where fuel mapping changes and richens up. Same concept for water hammer in pipes -- you want the excess pressure to be handled so the pressure spike doesn't go breaking things. As for altitude mitigation that's done with MAP sensors. Typical pressure gauges indicate the pressure delta between a contained substance and where the gauge itself is. A MAP sensor on the other hand looks at pressure vs a baseline. At sea level it'd be ~14.7 PSI, which is the pressure of the atmosphere. Thus to maintain engine performance at altitude, you're not concerned with pressure v. ambient, you want absolute pressure so the turbos can produce their typical pressure plus the additional pressure required to make up for the higher altitude has less total pressure.

 

[Snakebitten]

I'm a horrible teacher because I'm barely a student.

But this is a fascinating and comprehensible overview that is worth the dig

https://www.motorsport-developments.co.uk/Understanding_Ford_Ecoboost_Torque_Control.html

 

[wrgrimes]

Just to muddy the waters-
I drove to Ruston, LA today, 71mi each way on I-20.
Going, locked out 9&10; never saw the turbos spin up- 23.2mpg
Return, Normal 10 speed; turbos spun up some frequently near the peak of inclines- 25.2mpg
Cruise Control speed limit (70) plus 2
Traffic was light.

I will try some more, but so far I have not been able to beat the baseline Normal node

 

[Snakebitten]

Not really muddying the waters, unless someone needs absolutes/black&white.

It's fluid. Lots of moving pieces and parameters playing the torque ensemble.

Regardless of your strategy, you are getting insane efficiency when you consider the big heavy brick you are driving with ~600ftlbs burning gasoline.

 

[wrgrimes]

Not really muddying the waters, unless someone needs absolutes/black&white.

It's fluid. Lots of moving pieces and parameters playing the torque ensemble.

Regardless of your strategy, you are getting insane efficiency when you consider the big heavy brick you are driving with ~600ftlbs burning gasoline.

Yes, my 22+mpg overall is better than my previous Audi Q7 (4 cylinder) and my BMW X5!?

 

[powerboatr]

Not really muddying the waters, unless someone needs absolutes/black&white.

It's fluid. Lots of moving pieces and parameters playing the torque ensemble.

Regardless of your strategy, you are getting insane efficiency when you consider the big heavy brick you are driving with ~600ftlbs burning gasoline.

toss in
i got 23 in my 2021 f250 4x4 at hmmm 77 with the oil burner diesel
efficiency is the name of the new game with ability to dial in tq or not at a split second
my 22 has to work to get close to 22 for same speed, but i still like her more

 

[HammaMan]

toss in
i got 23 in my 2021 f250 4x4 at hmmm 77 with the oil burner diesel
efficiency is the name of the new game with ability to dial in tq or not at a split second
my 22 has to work to get close to 22 for same speed, but i still like her more

Diesel has more energy content per gallon than gasoline and the engines have higher compression ratios and better combustion efficiency. Unfortunately there's no free lunch though, the engines are built stronger with a higher price tag and the fuel is more $. Ethanol on the other hand contains less energy than gasoline.

Ethanol was sold as making gasoline 'greener' but the entire production cycle increased its CO2 footprint by 25% while robbing gasoline of of its energy content. It's been kept as an additive to gasoline to subsidize farming despite all of the drawbacks it has.

 

[powerboatr]

Diesel has more energy content per gallon than gasoline and the engines have higher compression ratios and better combustion efficiency. Unfortunately there's no free lunch though, the engines are built stronger with a higher price tag and the fuel is more $. Ethanol on the other hand contains less energy than gasoline.

Ethanol was sold as making gasoline 'greener' but the entire production cycle increased its CO2 footprint by 25% while robbing gasoline of of its energy content. It's been kept as an additive to gasoline to subsidize farming despite all of the drawbacks it has.

yes i know
i was trying to be a smart assss as the 250 weighed over 8600lbs and was areo like a tree stump
compared to the little 150
i will say the 250 did have lots of areo management stuff on front end.

agree a million about ethanol

 

[nomarhits400]

Yes, my 22+mpg overall is better than my previous Audi Q7 (4 cylinder) and my BMW X5!?

Audi Q7 4 cylinder? We’ve had 3 Q7’s- didn’t know they made a 4 cylinder.

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