MPGs - Many People Griping - A Foundational Knowledge Primer To Assist in Better Efficiency

[Blue Sky]

I’m curious about altitude. I understand that turbos are better at higher elevation because they can manage the air to fuel ratio more effectively than an NA. But does it make them more efficient?

 

[GBee]

There is a lot of conversation around the small gas tank and bad gas mileage (and correspondingly low overall range) for the LC250 so I figured it might be useful to address some of the basics around how the forced induction impacts fuel consumption so people can adjust their expectations and behaviors.

"Well anybody who can afford this car, shouldn't care about gas mileage because they can afford the gas!" - Well I most definitely can afford the gas, and premium at that, but being very far off of advertised EPA estimates is worthy of being upsetting even if one can afford to pay for gas and expensive gas even.

"The hybrid system in the LC250 isn't designed for fuel efficiency, but for low end power, so get over it". - Well yes, it's not BIASED toward the explicit goal of extracting maximum fuel efficiency, but by definition, the electric boost results in recaptured energy otherwise wasted and dissipated as heat via the brakes, and instead adds torque and power to the wheels, which necessarily translates to forward motion that otherwise wouldn't exist in the absence of the hybrid system. So either way, it generates more power and forward motion vs a non-hybrid system, even if its BIAS is more for supplementing power or filling holes in the power band while the turbo spools, etc.

"Toyota is silly, their ECO mode isn't actually better for MPGs, put it in Normal or Sport mode". - I love how people extoll the virtues of Toyota engineering and how they are very intentional with design and then decide that they actually programmed ECO mode to be less economical than Normal or Sport because they don't like the slower responses and compensate by being heavy footed during ECO mode and end up keeping the motor in boost a lot and wonder why ECO isn't getting them better mileage. You can't counteract ECO by being lead footed to offset slightly slower responses and acceleration, it's self defeating.

Without splitting hairs too finely and getting down to stoichiometric specifics regarding rich vs lean air fuel ratios run on the T24A - FTS, one can use the engine displacement (2.4L), compression ratio (11.0:1) and various boost pressures of the turbo, to get some understanding of back of the envelope naturally aspirated equivalent for various boost pressures from the turbo. After all, engines and the way they generate power is all just a giant pump of air and fuel. Think of the turbo as displacement on demand. So here we go:

1) No boost - 2.4L engine
2) 10 PSI boost - 4.03L engine
3) 15 PSI boost - 4.85L engine
4) 20 PSI boost - 6.07L engine

So if you're easy on the pedal and more importantly in ECO mode and driving smoothly (vs abruptly accelerating and winding up the turbo boost pressures), it consumes the fuel equivalent of the above stated naturally aspirated engines at the various loads described. If you're constantly at 10 PSI of boost, you're roughly ingesting and burning up the air/fuel of a 4L engine for those moments. The car is too heavy and big to be operating as solely a 2.4L 4 cylinder, for lots of the time, but to be under low single digits of boost for periods vs 10+ lbs makes quite a difference for fuel economy. I never hesitate to call on its full power when I need to accelerate quickly, I am merely pointing this out to the countless people who are confused as to why their fuel economy is low when they wind up the motor quite often and spend a lot of time in boost. Separately, the hybrid electric assist can also be thought of as additional displacement equivalent roughly equating to ~0.8L across the entire range. so factor that in as well (but this doesn't cost us any additional fuel, so is really quite a neat perk). Now add that back in and suddenly being a 2.4L supplemented by a 0.8L of equivalent electric power sounds a lot more reasonable at 3.2L displacement equivalent.

Fuelly shows an average of ~19 MPGs mixed for the LC250 and I think between this forum and that site, there is selection bias for LC/car enthusiasts that have a penchant for modifying their cars and in the case of the LC, typically upsizing their wheels and tires and lifting them, adding armor etc, which reduces MPGs. With stock suspension and tires, the LC has no issues being able to reach its EPA ratings if driven reasonably, and without calling on its full power potential constantly.

Thanks for the info. Very informative.
I bought my LC, not because I expected to be efficient. But because is comfortable, big enough for long trips and the style is very impressive. And of course, is a Toyota.
If I wanted efficiency, I would buy a Hybrid RAV 4.
The bottom line. We cannot have it all. It is a truck and trucks are heavy and required more torque and power.

 

[TakaraLC]

I’m curious about altitude. I understand that turbos are better at higher elevation because they can manage the air to fuel ratio more effectively than an NA. But does it make them more efficient?

Yeah, engines are more efficient at higher compression, so a boosted engine will be more efficient.

But to see a noticeable difference, engine needs to be under load with turbo generating boost. So, for day to day driving, with turbo only intermittently engaging, the difference will be minimal. But if you tow, you may notice a difference.

 

[Bad1975]

I’m curious about altitude. I understand that turbos are better at higher elevation because they can manage the air to fuel ratio more effectively than an NA. But does it make them more efficient?

More efficient than NA but altitude robs the available boost pressure, 1 BAR = 14.7 PSI = 1 Atmosphere (the normal air pressure at sea level). As altitude increase air pressure decreases and thus 14.7 PSI boosted at sea level is Effectively ~30 PSI to the engine and is only ~27 PSI at 5000' and 25 PSI at 10000'. Typical turbo engines loose about half the available HP/TQ that the turbo generate at about 7 PSI of loss, still not as bad as what happens to NA engine at altitude, but an NA engine also won't lose almost half of its HP/TQ around 10,000' either. The big drawback of a turbo engine is they are quite major dogs when the turbo doesn't work (limp mode and other issues).

Turbo chargers were originally developed for aircraft to increase performance over their counterparts at altitude and increase the ceiling available they could cruise or climb to, it was a game changer in dog fighting in the rotary engine aircraft era..

Also, turbos don't manage A/F ratio any better or differently than a NA fuel injector motor, it's actually much harder to control A/F ratio on a turbo engine. That's a major factor of why manufacturers use recirculation valves vice blow off valves as the later causes' A/F ratio spikes when the air has already been measured by the MAF and then gets dumped to atmosphere vice getting dumped back into the intake stream after the MAF. The A/F ratio is checked on both via MAF and verified good and that full burn is happening via Wide band O2 sensors before and after the CAT/s.

 

[Justaron123]

Do you have charge/eco/power on your cluster?

In the center yes not on the sides like the larger cluster

 

[Justaron123]

Something i see over and over from the high MPG folks is the misplaced assumption that low MPG folks are simply doing it wrong and the only variable is "drive better, like me". The thing is that isn't so much about how you are driving, it's a lot more of what you are driving. We are all driving in so many different scenarios, lengths of drives, speeds, stops and starts, weather, elevation, load, etc etc etc. This is a pretty complex and nuanced topic that doesn't distill down to one or two things so easily.

Anyhoo, my MPG is low because of gremlins. I don't know how to get rid of them.

Extra boost always solves gremlin issue

 

[TakaraLC]

In the center yes not on the sides like the larger cluster

Can you share a picture?

 

[Sugarloafer80]

If I take it easy I do 30+MPG (or 7.8 L/km as shown in the picture I took this morning). My LC is stock. I have no doubt that the average of 25MPG is easily achievable if you drive like a normal person and stay close to the speed limits.

View attachment 43319

Tears for Fears... NICE!!!

Don't forget tire pressures. I wonder how many have underinflated tires............. No need to go over, manufacturers max those numbers in the name of mileage these days.

 

[Justaron123]

Can you share a picture?

This is the 1958 “Dollar General value screen” Impression of the same screen as show in the original photo. It shows the boost & EV gauge with the same style but uses bars to read charge/eco/normal/power. Little battery in the bottom right and “EV” max bar shows the charge/eco/normal/power.

 

[TakaraLC]

This is the 1958 “Dollar General value screen” Impression of the same screen as show in the original photo. It shows the boost & EV gauge with the same style but uses bars to read charge/eco/normal/power. Little battery in the bottom right and “EV” max bar shows the charge/eco/normal/power.

This is different than the picture I posted. Charge/eco/power shown in the picture replaces the tachometer and allows you to monitor regenerative breaking.

 

[Justaron123]

This is different than the picture I posted. Charge/eco/power shown in the picture replaces the tachometer and allows you to monitor regenerative breaking.

Yes that can also be seen using the screen with just the driveline. The 1958 has the small screen. All selections can be placed in the center. For the 1958 you can use the picture I posted or the one of just the driveline line.

It’s easy to tell when your in regeneration and when your not. The lc250 does a way better job than the rubicon 4xe that I had. The biggest difference is the lc250 primarily starts regenerating when the drivers foot comes off the accelerator, engaging in engine braking, the motor-generator reverses its function. It acts as a generator, capturing the vehicle's kinetic energy (the energy of motion) that would otherwise be wasted as heat and converts it into electrical energy. So around town the rpm range you would want to be around 1200-1500 for fuel efficiency and recycling. 1700-2200 for moderate driving and 2200-3500 when towing. If you were to focus on the charging eco power those would be around the ranges to correlate with each.

 

[TakaraLC]

Yes that can also be seen using the screen with just the driveline. The 1958 has the small screen. All selections can be placed in the center. For the 1958 you can use the picture I posted or the one of just the driveline line.

It’s easy to tell when your in regeneration and when your not. The lc250 does a way better job than the rubicon 4xe that I had. The biggest difference is the lc250 primarily starts regenerating when the drivers foot comes off the accelerator, engaging in engine braking, the motor-generator reverses its function. It acts as a generator, capturing the vehicle's kinetic energy (the energy of motion) that would otherwise be wasted as heat and converts it into electrical energy. So around town the rpm range you would want to be around 1200-1500 for fuel efficiency and recycling. 1700-2200 for moderate driving and 2200-3500 when towing. If you were to focus on the charging eco power those would be around the ranges to correlate with each.

These gauges are also present on the larger screen, and no they are not showing when any info about regen breaking. One is showing power the electric motor is receiving and other is showing the boost turbo is producing.

The tachometer with charge section shows how much of the breaking power is from regen breaking. This is very helpful because the amount of regen breaking is dependent on the multiple factors, like battery charge state, battery temperature and electrical current. So one can not know how much of their breaking power is from regen vs friction breaks. On Hybrid Venza/Rav4 for example, if the battery charge is very high, it is very easy to see that the charge dial immediately maxes out even with a light touch to the break.

I don’t care about eco and power sections but I wish charge info was somehow integrated to the LC display, like by adding another quarter section to the hybrid max gauge where power the motor is generating is shown.

 

[Justaron123]

These gauges are also present on the larger screen, and no they are not showing when any info about regen breaking. One is showing power the electric motor is receiving and other is showing the boost turbo is producing.

The tachometer with charge section shows how much of the breaking power is from regen breaking. This is very helpful because the amount of regen breaking is dependent on the multiple factors, like battery charge state, battery temperature and electrical current. So one can not know how much of their breaking power is from regen vs friction breaks. On Hybrid Venza/Rav4 for example, if the battery charge is very high, it is very easy to see that the charge dial immediately maxes out even with a light touch to the break.

I don’t care about eco and power sections but I wish charge info was somehow integrated to the LC display, like by adding another quarter section to the hybrid max gauge where power the motor is generating is shown.

My apologies I misunderstood the original post. You are correct I was focusing on a different aspect. For the larger media screens. If you go to menu and then go to the car. Does it give you the option to see that there? The 1958 is limited to just three options. Hopefully the higher trim would allow you to see this as an active log while driving.

 

[COSmurf]

More efficient than NA but altitude robs the available boost pressure, 1 BAR = 14.7 PSI = 1 Atmosphere (the normal air pressure at sea level). As altitude increase air pressure decreases and thus 14.7 PSI boosted at sea level is Effectively ~30 PSI to the engine and is only ~27 PSI at 5000' and 25 PSI at 10000'. Typical turbo engines loose about half the available HP/TQ that the turbo generate at about 7 PSI of loss, still not as bad as what happens to NA engine at altitude, but an NA engine also won't lose almost half of its HP/TQ around 10,000' either. The big drawback of a turbo engine is they are quite major dogs when the turbo doesn't work (limp mode and other issues).

Turbo chargers were originally developed for aircraft to increase performance over their counterparts at altitude and increase the ceiling available they could cruise or climb to, it was a game changer in dog fighting in the rotary engine aircraft era..

Also, turbos don't manage A/F ratio any better or differently than a NA fuel injector motor, it's actually much harder to control A/F ratio on a turbo engine. That's a major factor of why manufacturers use recirculation valves vice blow off valves as the later causes' A/F ratio spikes when the air has already been measured by the MAF and then gets dumped to atmosphere vice getting dumped back into the intake stream after the MAF. The A/F ratio is checked on both via MAF and verified good and that full burn is happening via Wide band O2 sensors before and after the CAT/s.

I think this is a great explanation of how it conceptually works, with the only thing I’d add being that modern turbo engines and the ECUs managing them, tend to do a really good job of fully overcoming elevation related losses until you climb pretty high. What I mean is that the variation between atmospheric pressure at sea level and say 5000 ft can easily be overcome by the turbos spinning up and cramming in more thin air until air volume and pressure reach the desired thresholds up to the point where the system limits (primarily turbine size, turbo RPMs and heat management) mandate it to back off and stop compensating.

What weighs more: a pound of sea level dense air or a pound of thin air at 5k ft? SAME, just requires a bit more of the latter to achieve a pound. At some level of elevation, the thin-ness of the air just becomes such that the turbo can no longer spin fast enough to fully provide the compensating compression and volume due to heat and friction so you experience power loss but I certainly think at elevations up to at least 5000-7500 ft, there probably isn’t any loss at all for newer forced induction motors which cannot be said of naturally aspirated counterparts.

 

[TakaraLC]

I think this is a great explanation of how it conceptually works, with the only thing I’d add being that modern turbo engines and the ECUs managing them, tend to do a really good job of fully overcoming elevation related losses until you climb pretty high. What I mean is that the variation between atmospheric pressure at sea level and say 5000 ft can easily be overcome by the turbos spinning up and cramming in more thin air until air volume and pressure reach the desired thresholds up to the point where the system limits (primarily turbine size, turbo RPMs and heat management) mandate it to back off and stop compensating.

What weighs more: a pound of sea level dense air or a pound of thin air at 5k ft? SAME, just requires a bit more of the latter to achieve a pound. At some level of elevation, the thin-ness of the air just becomes such that the turbo can no longer spin fast enough to fully provide the compensating compression and volume due to heat and friction so you experience power loss but I certainly think at elevations up to at least 5000-7500 ft, there probably isn’t any loss at all for newer forced induction motors which cannot be said of naturally aspirated counterparts.

Yeah most modern turbos are (designed to be) limited by output pressure, meaning the how fast the turbo spins is restricted by the internal air resistance on the turbine. At altitude, the turbo will be still reach to the same output pressure (boost), but the turbine will spin to a faster RPM to do it since input air density is lower and therefore generates less internal resistance.

I am sure after a certain altitude, mechanical resistance inside the turbo becomes limiting so the turbine cannot spin any faster even if input pressure decreases, but that is probably above 15k feet range.

 

[TakaraLC]

My apologies I misunderstood the original post. You are correct I was focusing on a different aspect. For the larger media screens. If you go to menu and then go to the car. Does it give you the option to see that there? The 1958 is limited to just three options. Hopefully the higher trim would allow you to see this as an active log while driving.

No unfortunately there isn’t. I think we the option to display more at the same time on larger instrument cluster, but the available gauges are the same. On media screen, there is the option to plot gas mileage, but nothing about regen or hybrid system.

 

[New York Ralph]

There is a lot of conversation around the small gas tank and bad gas mileage (and correspondingly low overall range) for the LC250 so I figured it might be useful to address some of the basics around how the forced induction impacts fuel consumption so people can adjust their expectations and behaviors.

"Well anybody who can afford this car, shouldn't care about gas mileage because they can afford the gas!" - Well I most definitely can afford the gas, and premium at that, but being very far off of advertised EPA estimates is worthy of being upsetting even if one can afford to pay for gas and expensive gas even.

"The hybrid system in the LC250 isn't designed for fuel efficiency, but for low end power, so get over it". - Well yes, it's not BIASED toward the explicit goal of extracting maximum fuel efficiency, but by definition, the electric boost results in recaptured energy otherwise wasted and dissipated as heat via the brakes, and instead adds torque and power to the wheels, which necessarily translates to forward motion that otherwise wouldn't exist in the absence of the hybrid system. So either way, it generates more power and forward motion vs a non-hybrid system, even if its BIAS is more for supplementing power or filling holes in the power band while the turbo spools, etc.

"Toyota is silly, their ECO mode isn't actually better for MPGs, put it in Normal or Sport mode". - I love how people extoll the virtues of Toyota engineering and how they are very intentional with design and then decide that they actually programmed ECO mode to be less economical than Normal or Sport because they don't like the slower responses and compensate by being heavy footed during ECO mode and end up keeping the motor in boost a lot and wonder why ECO isn't getting them better mileage. You can't counteract ECO by being lead footed to offset slightly slower responses and acceleration, it's self defeating.

Without splitting hairs too finely and getting down to stoichiometric specifics regarding rich vs lean air fuel ratios run on the T24A - FTS, one can use the engine displacement (2.4L), compression ratio (11.0:1) and various boost pressures of the turbo, to get some understanding of back of the envelope naturally aspirated equivalent for various boost pressures from the turbo. After all, engines and the way they generate power is all just a giant pump of air and fuel. Think of the turbo as displacement on demand. So here we go:

1) No boost - 2.4L engine
2) 10 PSI boost - 4.03L engine
3) 15 PSI boost - 4.85L engine
4) 20 PSI boost - 6.07L engine

So if you're easy on the pedal and more importantly in ECO mode and driving smoothly (vs abruptly accelerating and winding up the turbo boost pressures), it consumes the fuel equivalent of the above stated naturally aspirated engines at the various loads described. If you're constantly at 10 PSI of boost, you're roughly ingesting and burning up the air/fuel of a 4L engine for those moments. The car is too heavy and big to be operating as solely a 2.4L 4 cylinder, for lots of the time, but to be under low single digits of boost for periods vs 10+ lbs makes quite a difference for fuel economy. I never hesitate to call on its full power when I need to accelerate quickly, I am merely pointing this out to the countless people who are confused as to why their fuel economy is low when they wind up the motor quite often and spend a lot of time in boost. Separately, the hybrid electric assist can also be thought of as additional displacement equivalent roughly equating to ~0.8L across the entire range. so factor that in as well (but this doesn't cost us any additional fuel, so is really quite a neat perk). Now add that back in and suddenly being a 2.4L supplemented by a 0.8L of equivalent electric power sounds a lot more reasonable at 3.2L displacement equivalent.

Fuelly shows an average of ~19 MPGs mixed for the LC250 and I think between this forum and that site, there is selection bias for LC/car enthusiasts that have a penchant for modifying their cars and in the case of the LC, typically upsizing their wheels and tires and lifting them, adding armor etc, which reduces MPGs. With stock suspension and tires, the LC has no issues being able to reach its EPA ratings if driven reasonably, and without calling on its full power potential constantly.

Good information. I have been getting 22.8 overall since last year with stock 20" rims and tires.

 

[ultane]

After a while when you own a vehicle, you get to know pretty closely how much additional fuel you can add after the initial pump shutdown to within a few tenths. That will get you within a few tenths in your calculations....consistently. It seems the fuel tank is on the left of LC. That would also suggest you would get slightly more in the tank if right side is higher. Would be pretty interesting if anyone has run the tank dry and done a complete fillup.

The Car Care Nut (YouTube) recommends to NOT add additional fuel after the pump shuts off, as it will eventually fill the charcoal canister. They are not cheap, and likewise not easy to replace. DAMHIKT….

I have run for ~30 miles after the DTE showed 0. I put 16.5 gallons of fuel back in the tank.


Edited: To state proper amount of fuel on FIRST fill up on day one of ownership (I keep receipts).

 

[Sugarloafer80]

Stellantis is still playing catchup in hybrid world. I had a Tonale loaner for a week a year ago. I believe same fundamental type of system. Loved it. Loved how you could do 75mph pure EV mode. Only had ~32? miles of range but....but I did notice even coasting down my long hills etc did little to move the bar on that EV range. Fiat is totaly different..pure EV

The Car Care Nut (YouTube) recommends to NOT add additional fuel after the pump shuts off, as it will eventually fill the charcoal canister. They are not cheap, and likewise not easy to replace. DAMHIKT….

I have run for 40 miles after the DTE showed 0. I put 17.1 gallons (IIRC) of fuel back in the tank.

Yup, 2+ gallon reserve or 10 liters. I hadn't heard that one in years. Low placement of the charcoal canister was usually the culprit. I have cars that shutoff as much as 1.5 gal before I reduce flow and let it fill till it shuts off again. This is not even a full to the brim scenario. RR would only take .1-.2 after shutoff Stelvio is opposite and esp my baffled tank Evora takes forever to top up and even that is never a full to brim scenario because the tanks are vertical.

 

[TakaraLC]

Took the stock gx OT on the freeway for a 40 mile loop. Going 65mph , 29.7 on the way there and 22 coming back . That’s 26mpg combined. As for city driving on I’m getting 2 mpg less compared to stock lc

That is not combined 26 by the way.