Engine braking

[colfishnski]

I took the new ride to the summit of Pikes Peak today. Engine pulls great at high altitude, but coming down was a bit of a different story. Would love some advice and feedback on this.

I find the engine braking, gearing down to M2 and M1, lacking in the ability to effectively slow the truck on steep grades. Admittedly, it's a long steep decline there but I've done it many times and can usually baby brakes to keep them cool. Today the LC brakes got to 320 degrees at Glen Cove checkpoint. Could smell them slightly coming down, and knew I was on them more than I wanted even before getting a temp read. Never got fade, but concerning.

I find gearing down tends to get the motor quickly spinning at 4 or 5k rpms, but the speed is still picking up. There's just not a lot of engine braking to be had.

I experimented going into 4 low, and that was better, but the engine still wants to rev very high, and the speed still gets away from you, though more slowly, and on flatter sections you're stuck with being in low range.

Either gear range, the high RPMs are a bit disconcerting.

Am I missing something here? A setting, a mode selection, a technique, something..? I live in Colorado and have noticed a lack of slowing at highway speeds gearing down, but not to the point of brake temp concerns. I'm an experienced mountain driver and have not had a history of being hard on brakes. But I'm sure wide open to suggestions

I'm only 2k miles in and haven't done real trails yet, so a bit concerned on steep downhills. Maybe this is better at crawling speeds?

Of all the mods, I'm thinking beefed up slotted rotors and the best pads money can buy might be on the shortlist.

Any thoughts much appreciated.

 

[Area 51]

Did you try the tow haul mode?

 

[colfishnski]

Did you try the tow haul mode?

I did not. Tow haul is a mystery to me, but will experiment with it.

 

[b407driver]

The LC250's engine has little capacity for engine braking. Coming down off Santa Fe Peak I wondered what would happen (4 Low, 1st gear) if I just let it go and it hit redline; it surely would have if I hadn't hit the brakes. Not great for towing, either, and Tow/Haul mode doesn't do much.

 

[Altitude]

I live in Castle Rock and Avon and drive back and forth a few times a month. Honestly I’ve not noticed any issue with engine braking.

It’s an 8 speed transmission, so dropping one gear might not make as much difference as you expect based on a previous 5 speed unit. Try putting it in cruise control on long grades and see what it comes up with. Last weekend I managed to go from the Vail Pass summit down to the Vail Village exit without touching the brake.

 

[colfishnski]

I live in Castle Rock and Avon and drive back and forth a few times a month. Honestly I’ve not noticed any issue with engine braking.

It’s an 8 speed transmission, so dropping one gear might not make as much difference as you expect based on a previous 5 speed unit. Try putting it in cruise control on long grades and see what it comes up with. Last weekend I managed to go from the Vail Pass summit down to the Vail Village exit without touching the brake.

Thanks. I've just noted it at highway speeds in the mountains, not that it was particularly concerning, but certainly lacked engine braking compared to any car I've had.

The trip down Pikes Peak is 19 miles of pretty steep grade, so it's an extreme example, but honestly I'm pretty concerned about long downhill sections of trail. It's going to require attention to brake temps and perhaps pauses to let things cool. That's a bit of a surprise on an off-road designed vehicle. I also think we're going to find these trucks eat front brakes.

The cruise control uses the brakes to slow the vehicle when needed, so I'm thinking even if you didn't touch them the system is applying them anyway. That's a pretty steep grade coming off Vail Pass so it would be interesting to know just how hot the brakes get under full system control. The system will downshift on its own, but doesn't hit the rpms I hit today manually trying to maximize engine braking.

 

[Altitude]

Thanks. I've just noted it at highway speeds in the mountains, not that it was particularly concerning, but certainly lacked engine braking compared to any car I've had.

The trip down Pikes Peak is 19 miles of pretty steep grade, so it's an extreme example, but honestly I'm pretty concerned about long downhill sections of trail. It's going to require attention to brake temps and perhaps pauses to let things cool. That's a bit of a surprise on an off-road designed vehicle. I also think we're going to find these trucks eat front brakes.

The cruise control uses the brakes to slow the vehicle when needed, so I'm thinking even if you didn't touch them the system is applying them anyway. That's a pretty steep grade coming off Vail Pass so it would be interesting to know just how hot the brakes get under full system control. The system will downshift on its own, but doesn't hit the rpms I hit today manually trying to maximize engine braking.

It was mainly using the transmission - I was watching because I was also curious how it would vary the brakes and the transmission to moderate speed. Luckily we can see in the instrument cluster when the brakes are being applied.

 

[colfishnski]

It was mainly using the transmission - I was watching because I was also curious how it would vary the brakes and the transmission to moderate speed. Luckily we can see in the instrument cluster when the brakes are being applied.

Interesting. I've not noticed the braking indicated on the cluster in cruise. Assuming it's the two red bars at the bottom. I have some highway driving today, will take a look.

 

[Altitude]

Interesting. I've not noticed the braking indicated on the cluster in cruise. Assuming it's the two red bars at the bottom. I have some highway driving today, will take a look.

That’s it, if I understand correctly. I initially thought it was odd to have a brake indicator on the dash. But, as we’re discussing here, these vehicles apply the brakes on their own more than might be intuitive - so I guess it’s a good idea to have a readout.

 

[McCloud_Rainbow]

Don’t forget these are hybrids, so often when the brake indicators are on, it is regenerative braking and not the brakes themselves.

Obviously if your brakes are heating up, those pads are getting used, but in my experience, during normal driving conditions, I let the regen braking handle the load and slow the car down before pushing hard on the brakes to engage the pads. I am expecting longer pad life honestly, but only time will tell.

 

[colfishnski]

Interesting. I've not noticed the braking indicated on the cluster in cruise. Assuming it's the two red bars at the bottom. I have some highway driving today, will take a look.

Don’t forget these are hybrids, so often when the brake indicators are on, it is regenerative braking and not the brakes themselves.

Obviously if your brakes are heating up, those pads are getting used, but in my experience, during normal driving conditions, I let the regen braking handle the load and slow the car down before pushing hard on the brakes to engage the pads. I am expecting longer pad life honestly, but only time will tell.

It's my impression that regenerative braking is pretty mild in these trucks. In fact, I'm not noticing much slowing power at all from it. Perhaps my area is just an outlier, but I constantly drive mountain roads with steep inclines. It seems OK at highway speeds, though in slow go steep decent, Pikes Peak yesterday was full of freaked out toruists going 10 miles an hour, but when you're behind an 8000 lb Silverado that barely taps his brakes because his low gear grinds his truck to a halt, it was honestly pretty disturbing. Unless I'm missing something, the LC is not real comforting doing steep descents. I've never had a vehicle that would run away from you in 4lo even.

 

[grandsons]

Modern engines either petrol or diesel have less engine breaking power due to increased engine efficiency. This is due to better mechanical construction, better electronic gestion and variable turbo that regulate the airflow to maximize efficiency.

To counter act these benefits driver must increase engine lost by increasing rpm below red limit, this is unusual, noisy and not very much appreciated. This is solely valid for a well broken in engine. Do not use breaking power with a new engine. For this select gear manually and let the engine rev rise below red limit.

This phenomenon is even worst with diesel engines, because they are not equipped with throttle flap thus vacuum cannot be created during deceleration (vacuum at intake decrease engine efficiency). Some diesel car manufacturer implement engine brake mode, like a sport mode or other more commun engine modes. By playing with low gears, valve timing and/or turbo flow incidence, they try mimic good old smoky engine.

 

[colfishnski]

Modern engines either petrol or diesel have less engine breaking power due to increased engine efficiency. This is due to better mechanical construction, better electronic gestion and variable turbo that regulate the airflow to maximize efficiency.

To counter act these benefits driver must increase engine lost by increasing rpm below red limit, this is unusual, noisy and not very much appreciated. This is solely valid for a well broken in engine. Do not use breaking power with a new engine. For this select gear manually and let the engine rev rise below red limit.

This phenomenon is even worst with diesel engines, because they are not equipped with throttle flap thus vacuum cannot be created during deceleration (vacuum at intake decrease engine efficiency). Some diesel car manufacturer implement engine brake mode, like a sport mode or other more commun engine modes. By playing with low gears, valve timing and/or turbo flow incidence, they try mimic good old smoky engine.

Well, my engine is well broken in now, and my brakes are fully seated.. I don't think there's any sugar coating it, the US hybrid gas power train is a little scary on extended steep downhills. It will require more brake power in those conditions than a vehicle with average or better engine braking. It will require close attention to brake temps, and if this type of driving is frequent, it will require shorter brake service intervals. I don't see any way around that unless I'm missing some golden bullet setting.

I love the truck, and will learn to live with it because it's just so good in so many ways, but that's a rather disheartening performance limitation on a true 4 wheeler in my view.

 

[Altitude]

Modern engines either petrol or diesel have less engine breaking power due to increased engine efficiency. This is due to better mechanical construction, better electronic gestion and variable turbo that regulate the airflow to maximize efficiency.

To counter act these benefits driver must increase engine lost by increasing rpm below red limit, this is unusual, noisy and not very much appreciated. This is solely valid for a well broken in engine. Do not use breaking power with a new engine. For this select gear manually and let the engine rev rise below red limit.

This phenomenon is even worst with diesel engines, because they are not equipped with throttle flap thus vacuum cannot be created during deceleration (vacuum at intake decrease engine efficiency). Some diesel car manufacturer implement engine brake mode, like a sport mode or other more commun engine modes. By playing with low gears, valve timing and/or turbo flow incidence, they try mimic good old smoky engine.

Decent argument, but would be better if you spelled “braking” right. Given that, as a concept, it’s central to the point you’re arguing.

Not lost on me your profile says you’re in Switzerland and I will concede right now your English is better than my German or French.

 

[grandsons]

Decent argument, but would be better if you spelled “braking” right

I'm sorry for the typo, both brake and break sound close.

Curious Swiss people live in a multicultural world. If I travel 50 km, it's a different language. I think it's completely different from the US, except for the drug-ridden neighborhoods (neighbourhood?). Last century, I worked for a company in Haverhill, Massachusetts. And I have a cousin who is a university professor in your country, a specialist in number theory. I don't think his budget will be cut, so he will not be deported.

 

[Ed1]

The fact that it’s a four cylinder engine might have something to do with milder engine braking. Fewer cylinders to create negative pressure and hold back the vehicle. Heavy vehicle, small total cylinder displacement.

 

[Altitude]

I'm sorry for the typo, both brake and break sound close.

Curious Swiss people live in a multicultural world. If I travel 50 km, it's a different language. I think it's completely different from the US, except for the drug-ridden neighborhoods (neighbourhood?). Last century, I worked for a company in Haverhill, Massachusetts. And I have a cousin who is a university professor in your country, a specialist in number theory. I don't think his budget will be cut, so he will not be deported.

It’s a mysteriously common misspelling over here these days, tied with spelling the word that means the opposite of gain as “loose.” Mostly people who do it either aren’t paying attention or think that being wrong and being right are the same thing. Your situation is clearly different.

 

[colfishnski]

Modern engines either petrol or diesel have less engine breaking power due to increased engine efficiency. This is due to better mechanical construction, better electronic gestion and variable turbo that regulate the airflow to maximize efficiency.

To counter act these benefits driver must increase engine lost by increasing rpm below red limit, this is unusual, noisy and not very much appreciated. This is solely valid for a well broken in engine. Do not use breaking power with a new engine. For this select gear manually and let the engine rev rise below red limit.

This phenomenon is even worst with diesel engines, because they are not equipped with throttle flap thus vacuum cannot be created during deceleration (vacuum at intake decrease engine efficiency). Some diesel car manufacturer implement engine brake mode, like a sport mode or other more commun engine modes. By playing with low gears, valve timing and/or turbo flow incidence, they try mimic good old smoky engine.

The fact that it’s a four cylinder engine might have something to do with milder engine braking. Fewer cylinders to create negative pressure and hold back the vehicle. Heavy vehicle, small total cylinder displacement.

I think you both are correct here. I'm no expert but reading a lot about this in the last couple of days I think it's a combination of small displacement, high effeciency and high air flow, it's just simply not the available mass of compression in a larger motor, plus it seems with the hybrid transmission setup, perhaps the electric motor acting as a torque converter between the engine and transmission isn't conducive to maximal engine braking. Don't think regen braking really helps slowing much.

I think it's about driving strategy in these situations. Anticipate, slow in advance, understand the limitation, and keep a eye on temps. I tried tow/haul and it changes the shift pattern some and it helps a little, but isn't magic. I drove two highway passes yesterday and this really isn't much of an issue at highway speeds, say 35mph and above. Slower, extended downhill is the concern.