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Chris Bryant

4x4 system explained

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Chris Bryant

I just wondered if anyone could explain how the 4x4 system works in a 61 reg HiLux, Automatic.?

When I had a Freelander, I was able to know it inside out (which came in handy, often). With the IRD, how the viscous coupler worked etc.

 

With the HiLux, all I know is that 4H is just the same but 4wd. And 4L turns off the traction/ABS.

Would be great to understand the overall system. When I've used 4H, it feels like it has limited diff, as the turning circle is hugely increased.

 

 

As a sidenote, the Heater Booster switch. Is that just an idle increaser.? If so, I assume when driving (cold), it puts strain on the brakes/auto box, as it's trying to rev whilst stationary at a junction.??

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Shifty
31 minutes ago, Chris Bryant said:

I just wondered if anyone could explain how the 4x4 system works in a 61 reg HiLux, Automatic.?

When I had a Freelander, I was able to know it inside out (which came in handy, often). With the IRD, how the viscous coupler worked etc.

 

With the HiLux, all I know is that 4H is just the same but 4wd.

Correct!   4H simply engages the front diff leaving the gearbox ratios the same as 2H.

And 4L turns off the traction/ABS.

Correct!  4L turns off ABS and TC however it also engages the low range in the transfer box which effectively gives you a complete set of lower gears using the normal gearbox. On my truck it also allows me to "lock" the rear diff but only in 4L.

Would be great to understand the overall system. When I've used 4H, it feels like it has limited diff, as the turning circle is hugely increased.

The turning circle may appear increased because the Hilux does not have a centre diff so the front tyres will not cope easily with tight turns unless on slippy ground. I think Yota never used centre diffs as they are a known weak point - especially on Landrovers. My Defender needed a centre diff as it was permanent 4WD

As a sidenote, the Heater Booster switch. Is that just an idle increaser.? If so, I assume when driving (cold), it puts strain on the brakes/auto box, as it's trying to rev whilst stationary at a junction.??

As I understand it the heat booster increases the idle so the engine can warm up faster.

 

 

 

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JasXPear

Hi Chris

The Hilux has no centre diff so the transmission winds up a bit in 4wd, that’s why you feel the turning circle change.

The heater booster used to be called the Idle Up and yeah, I guess it would put more load on an auto. Rumour has it that there’s a supplementary electric heater that kicks in when the external temp is below a certain level but I don’t know that’s ever been verified.

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Chris Bryant

Thanks for the responses. Most helpful.

With regards to the 4x4 part. Is the grip literally just down to the ABS/Traction control sensors then.?

So unlike a viscous coupler, when it heats up when slipping etc. 

It's just 4 wheel drive.?

 

 

Didn't know that re the front diff (or lack of). Most things on my LR became weak points, so a front diff might as well join the gang. It's funny how much I loved that car, until I got the Hilux.

 

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JasXPear
31 minutes ago, Chris Bryant said:

Thanks for the responses. Most helpful.

With regards to the 4x4 part. Is the grip literally just down to the ABS/Traction control sensors then.?

So unlike a viscous coupler, when it heats up when slipping etc. 

It's just 4 wheel drive.?

 

 

Didn't know that re the front diff (or lack of). Most things on my LR became weak points, so a front diff might as well join the gang. It's funny how much I loved that car, until I got the Hilux.

 

Defenders have a front, rear and centre diff so you can drive them on tarmac in 4wd with no windup. The rouble is when any wheel loses grip all the drive gets sent to that wheel and all the others stop. Thats why they have a centre diff so at least 50% of the drive will go to the non-spinning axle.

The Hilux doesnt have a centre diff at all. It means you cant use it on anything with grip like tarmac but means you will always get power sent to the front/rear if one wheel at the other end is spinning. With an LSD/difflock on the rear too you're guaranteed power to 3 wheels in effect.

Only the newer Hilux (not certain what reg) have traction control. The mk4 Hilux and earlier 3.0 Mk6s  have a limited slip rear diff whereas the mk5 and 2.5 mk6s have a manual electronic locking rear diff.

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Chris Bryant
2 hours ago, JasXPear said:

Defenders have a front, rear and centre diff so you can drive them on tarmac in 4wd with no windup. The rouble is when any wheel loses grip all the drive gets sent to that wheel and all the others stop. Thats why they have a centre diff so at least 50% of the drive will go to the non-spinning axle.

The Hilux doesnt have a centre diff at all. It means you cant use it on anything with grip like tarmac but means you will always get power sent to the front/rear if one wheel at the other end is spinning. With an LSD/difflock on the rear too you're guaranteed power to 3 wheels in effect.

Only the newer Hilux (not certain what reg) have traction control. The mk4 Hilux and earlier 3.0 Mk6s  have a limited slip rear diff whereas the mk5 and 2.5 mk6s have a manual electronic locking rear diff.

Mine is a Mk6 3.0, so guessing it has the limited slip differential.

Thanks for your help. Got it now. 

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Wolfracer

The "idle up" function cuts out when you select a gear. Put it back in park and you will notice the revs have dropped. Ie no extra strain, its not running a fast idle  whilst in gear. 

 

 

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Daniel.
13 minutes ago, Wolfracer said:

The "idle up" function cuts out when you select a gear. Put it back in park and you will notice the revs have dropped. Ie no extra strain, its not running a fast idle  whilst in gear. 

 

 

Mine stayes on untill you move over about 3mph but its a manual

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Chris Bryant
1 hour ago, Wolfracer said:

The "idle up" function cuts out when you select a gear. Put it back in park and you will notice the revs have dropped. Ie no extra strain, its not running a fast idle  whilst in gear. 

 

 

Mine is auto and definitely does rev higher whilst in gear, until it reaches the desired temperature of course.

So at say a t-junction, you can feel it trying to creep forwards whilst you're foot is planted on the brake.

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Wolfracer

Them I stand corrected.

MINE cuts out when I select D.

 

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Mhan54
13 hours ago, Wolfracer said:

Them I stand corrected.

MINE cuts out when I select D.

 

Mine is the same, revs drop back to normal as soon as d or r selected :thumbsup:

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Wolfracer
6 hours ago, Mhan54 said:

Mine is the same, revs drop back to normal as soon as d or r selected :thumbsup:

Yep. Tested mine today. Released handbrake untill its was just creeping forward. Just. 

Hit the button and erm... nothing changed, no increase in forward motion, no increase in engine revs.  I knocked it into park and the revs slowly rose to the higher level.

 

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moggy1968
On 12/6/2017 at 12:53, Chris Bryant said:

Thanks for the responses. Most helpful.

With regards to the 4x4 part. Is the grip literally just down to the ABS/Traction control sensors then.?

So unlike a viscous coupler, when it heats up when slipping etc. 

It's just 4 wheel drive.?

 

 

Didn't know that re the front diff (or lack of). Most things on my LR became weak points, so a front diff might as well join the gang. It's funny how much I loved that car, until I got the Hilux.

 

In a word yes, but I think only below 30mph on 4H or in 4L. That will also contribute to the steering effect in 4L because it’s acting a bit (but not entirely) like a locker on the front axle.

as said above, the part time 4x4 set up means you cannot be in 4wd in a firm surface like tarmac, you’ll break something in the transmission or diff (I have heard of front diff failures, probably as a result of this) that’s one disadvantage over a Landy where you could use 4low on a grippy surface without the centre diff engaged, say when reversing a trailer, in a hilux you can’t.

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damian666
46 minutes ago, moggy1968 said:

In a word yes, but I think only below 30mph on 4H or in 4L. That will also contribute to the steering effect in 4L because it’s acting a bit (but not entirely) like a locker on the front axle.

as said above, the part time 4x4 set up means you cannot be in 4wd in a firm surface like tarmac, you’ll break something in the transmission or diff (I have heard of front diff failures, probably as a result of this) that’s one disadvantage over a Landy where you could use 4low on a grippy surface without the centre diff engaged, say when reversing a trailer, in a hilux you can’t.

 

On 06/12/2017 at 12:53, Chris Bryant said:

Thanks for the responses. Most helpful.

With regards to the 4x4 part. Is the grip literally just down to the ABS/Traction control sensors then.?

So unlike a viscous coupler, when it heats up when slipping etc. 

It's just 4 wheel drive.?

 

 

Didn't know that re the front diff (or lack of). Most things on my LR became weak points, so a front diff might as well join the gang. It's funny how much I loved that car, until I got the Hilux.

 

ABS/TC is always active on the mk6 (and Facelift and later etc) in 2wd H and L. The 4 wheel speed sensors feed back to the ECU and ABS module. If one wheel is sensed as going disproportionately quick as opposed to the others the brake is applied to slow it down. As the front and rear diffs are open (some have LSD at rear) this brake application prevents all the power to the particular axle going into the faster spinning wheel. The ABS/TC doesn't make the steering stiffer. The disparity between inside and outside wheel speeds when steering is not enough to trigger an intervention by the system. It is also worth remembering that the TC system needs a slip/spin to occur before it can see that issue and start to counter it. It is also not anything like active power distribution as fitted to race and performance vehicles. Although quick it is still relatively simple and has a reaction time more than a full-blown computer controlled set-up, and it doesn't do clever stuff like transfer power between wheels when cornering etc.

The Lux has no Centre diff. If you drive on grippy surfaces in 4wd, the turning left and right will create an imbalance between the front propshaft and the rear (the left/right on the front are fine as they are through a diff) and the difference between front and back usually manifests by a front half shaft or front diff failure, as they are the weakest points. 

Stiffening up when in 4wd when steering sharply is caused by the centre diff not wanting the front wheels to turn at a different speed to the rear. This is caused by the radius of the front wheels when turning being different between inside and out but not exactly opposed so that imbalance is fighting the centre diff. The fronts equalise between each other through the front diff but the equalled amount is still a bit different to the rear. If you remove the front propshaft and engage 4wd so the front diff connects then steering will feel the same as 2wd. The stiffening comes from the centre connection. Try a front locker! Then it's really stiff on tarmac!

Defender has a centre diff which can be locked by the driver if needed so can keep 4wd all the time.

As the Lux is intended as a different purpose to the defender, with only using 4wd when needed as opposed to all the time, there is no need for centre diff. No Centre diff and usually 2wd decreases wear on parts and improves fuel blah blah. Let's face it, you won't actually need 4wd very often. So if not using it why wear it out!

Engaging 4H does a few things, 1 is to connect front Prop shaft in the transfer box to drive the front diff, the other is slide a sleeve across to connect the offside halfshaft to the front diff. The centre diff connection is mechanical via the lever itself, the front diff connection is electrical signal from sensor on the transfer lever to an actuator on the front of the diff that pushes the slide across. Going from 4H to 4L is mechanical, and changes the range in the transfer from higher to lower.

If you want to be able to use low range on transfer box withou the front issues, there is a mod you can do to cut the power to the 4wd ECU. This means that shoving the transfer lever to to 4L will only alter the transfer box and will not engage the front diff offside connection, or switch off the TC etc (the signal to the TC is from the front actuator as part of a position feedback arrangement in the actuator). It is very handy when shunting trailers and stuff like that. 

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Wolfracer

Been tootlimg around the snowy roads in 4 low, with the front diff off. Flick of a switch and bingo. Just like the surfs were 20 years ago! 

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damian666
1 hour ago, Wolfracer said:

Been tootlimg around the snowy roads in 4 low, with the front diff off. Flick of a switch and bingo. Just like the surfs were 20 years ago! 

Handy isn't  it!

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moggy1968

Damian- I was talking about tc on the front axle. As you say, the rear is always on. There is a way to switch it off but it’s complex and I can’t remeber how now. Regrettably memories of my hilux ownership are fading 😭. Even the dealer didn’t know and it can only be done below 30mph, which is a pain as in some circumstances you might want it off completely. You also can’t switch to off abs which is a pain in an off road vehicle in some circumstances 

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damian666
2 minutes ago, moggy1968 said:

Damian- I was talking about tc on the front axle. As you say, the rear is always on. There is a way to switch it off but it’s complex and I can’t remeber how now. Regrettably memories of my hilux ownership are fading 😭. Even the dealer didn’t know and it can only be done below 30mph, which is a pain as in some circumstances you might want it off completely. You also can’t switch to off abs which is a pain in an off road vehicle in some circumstances 

On the MK6 the traction control system is all four wheels or not at all. The TC monitors the speed of all four wheels at all times and compares those speeds continually.The TC has no controlling connection to the differentials in any way and solely acts by applying brakes to the wheels if it gauges if one is going too fast. Obviously if the truck is in 2wd then one of the front wheels cannot accelerate faster than it's chums but it still provides input to the TC system. If for example the truck is driving along and the driver wellies it or hits ice (for the sake of this example you keep going straight forward) and the rear wheels both accelerate by drive applied via the rear axle, then the TC system sees them both suddenly speeding up. It can't specifically do anything about it because it is based on a L-R disparity but if one of those spins even faster (ie truck starts to go sideways) than the other it will attempt to slow the faster one.

You can entirely disengage the TC and ABS at any speed if you really want to but the ECU is not set up to have that so gets upset.

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Chris Bryant
1 minute ago, damian666 said:

On the MK6 the traction control system is all four wheels or not at all. The TC monitors the speed of all four wheels at all times and compares those speeds continually.The TC has no controlling connection to the differentials in any way and solely acts by applying brakes to the wheels if it gauges if one is going too fast. Obviously if the truck is in 2wd then one of the front wheels cannot accelerate faster than it's chums but it still provides input to the TC system. If for example the truck is driving along and the driver wellies it or hits ice (for the sake of this example you keep going straight forward) and the rear wheels both accelerate by drive applied via the rear axle, then the TC system sees them both suddenly speeding up. It can't specifically do anything about it because it is based on a L-R disparity but if one of those spins even faster (ie truck starts to go sideways) than the other it will attempt to slow the faster one.

You can entirely disengage the TC and ABS at any speed if you really want to but the ECU is not set up to have that so gets upset.

Is it different then when you press and hold the VSC (hope I got that right) switch.? Doesn't that turn off both TC and ABS.?

3 hours ago, damian666 said:

 

ABS/TC is always active on the mk6 (and Facelift and later etc) in 2wd H and L. The 4 wheel speed sensors feed back to the ECU and ABS module. If one wheel is sensed as going disproportionately quick as opposed to the others the brake is applied to slow it down. As the front and rear diffs are open (some have LSD at rear) this brake application prevents all the power to the particular axle going into the faster spinning wheel. The ABS/TC doesn't make the steering stiffer. The disparity between inside and outside wheel speeds when steering is not enough to trigger an intervention by the system. It is also worth remembering that the TC system needs a slip/spin to occur before it can see that issue and start to counter it. It is also not anything like active power distribution as fitted to race and performance vehicles. Although quick it is still relatively simple and has a reaction time more than a full-blown computer controlled set-up, and it doesn't do clever stuff like transfer power between wheels when cornering etc.

The Lux has no Centre diff. If you drive on grippy surfaces in 4wd, the turning left and right will create an imbalance between the front propshaft and the rear (the left/right on the front are fine as they are through a diff) and the difference between front and back usually manifests by a front half shaft or front diff failure, as they are the weakest points. 

Stiffening up when in 4wd when steering sharply is caused by the centre diff not wanting the front wheels to turn at a different speed to the rear. This is caused by the radius of the front wheels when turning being different between inside and out but not exactly opposed so that imbalance is fighting the centre diff. The fronts equalise between each other through the front diff but the equalled amount is still a bit different to the rear. If you remove the front propshaft and engage 4wd so the front diff connects then steering will feel the same as 2wd. The stiffening comes from the centre connection. Try a front locker! Then it's really stiff on tarmac!

Defender has a centre diff which can be locked by the driver if needed so can keep 4wd all the time.

As the Lux is intended as a different purpose to the defender, with only using 4wd when needed as opposed to all the time, there is no need for centre diff. No Centre diff and usually 2wd decreases wear on parts and improves fuel blah blah. Let's face it, you won't actually need 4wd very often. So if not using it why wear it out!

Engaging 4H does a few things, 1 is to connect front Prop shaft in the transfer box to drive the front diff, the other is slide a sleeve across to connect the offside halfshaft to the front diff. The centre diff connection is mechanical via the lever itself, the front diff connection is electrical signal from sensor on the transfer lever to an actuator on the front of the diff that pushes the slide across. Going from 4H to 4L is mechanical, and changes the range in the transfer from higher to lower.

If you want to be able to use low range on transfer box withou the front issues, there is a mod you can do to cut the power to the 4wd ECU. This means that shoving the transfer lever to to 4L will only alter the transfer box and will not engage the front diff offside connection, or switch off the TC etc (the signal to the TC is from the front actuator as part of a position feedback arrangement in the actuator). It is very handy when shunting trailers and stuff like that. 

Thank you. Can't get any more comprehensive than that.

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damian666
52 minutes ago, Chris Bryant said:

Is it different then when you press and hold the VSC (hope I got that right) switch.? Doesn't that turn off both TC and ABS.?

VSC is Vehicle Stability Control and again, uses the four wheel speed sensors as inputs but also the steering wheel position sensor and an accelerometer in the truck. The idea of the VSC is to keep you going in a straight line. If for example you are going along the motorway and hit an unseen pothole or big gust of wind then the truck will swerve. The idea is that the VSC system senses this and attempts to correct the swerve (and thus the roll and likelihood of the truck rolling over) by braking the wheels in the appropriate way to get the control.

An added feature/bonus is the Towing Stability or whatever they call it. If you get a trailer slewing around and trying to push the arse of the truck sideways the VSC system pulses the brakes on the rear corner to the direction of the shove to slow it, so the rest of the truck effectively pivots slightly round that wheel. So if the arse is going to the right it brakes the right rear wheel so the momentum of the truck pushes the nose to the right rather than being pushed left by the tail swing. It's kinda like skiing and cutting in to zigzag down a slope. I know it works, I have had it go on a badly loaded trailer that went a rogue and tried to flip me off the motorway. Feeling and hearing the rear wheels lock up alternately as the truck swerves is kinda cool! That coupled with me accelerating rather than braking brought it back under control.

VSC switch pressed will turn off the VSC. Press and hold eventually turns off the TC too. They will both re-engage normally at about 30mph. ABS is always on.

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Chris Bryant
10 minutes ago, damian666 said:

VSC is Vehicle Stability Control and again, uses the four wheel speed sensors as inputs but also the steering wheel position sensor and an accelerometer in the truck. The idea of the VSC is to keep you going in a straight line. If for example you are going along the motorway and hit an unseen pothole or big gust of wind then the truck will swerve. The idea is that the VSC system senses this and attempts to correct the swerve (and thus the roll and likelihood of the truck rolling over) by braking the wheels in the appropriate way to get the control.

An added feature/bonus is the Towing Stability or whatever they call it. If you get a trailer slewing around and trying to push the arse of the truck sideways the VSC system pulses the brakes on the rear corner to the direction of the shove to slow it, so the rest of the truck effectively pivots slightly round that wheel. So if the arse is going to the right it brakes the right rear wheel so the momentum of the truck pushes the nose to the right rather than being pushed left by the tail swing. It's kinda like skiing and cutting in to zigzag down a slope. I know it works, I have had it go on a badly loaded trailer that went a rogue and tried to flip me off the motorway. Feeling and hearing the rear wheels lock up alternately as the truck swerves is kinda cool! That coupled with me accelerating rather than braking brought it back under control.

VSC switch pressed will turn off the VSC. Press and hold eventually turns off the TC too. They will both re-engage normally at about 30mph. ABS is always on.

I am glad I asked now. :)  It sounds like the VSC would be dangerous when you say it out loud - but I totally get how it helps... very clever.

Gotta love a forum for finding out things like this.

 

Thanks all.

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Wolfracer
4 hours ago, damian666 said:

Handy isn't  it!

More than one would think. Especially the reverse up a slope around a corner with maxed out trailer weight. :thumbsup:

 

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damian666
24 minutes ago, Wolfracer said:

More than one would think. Especially the reverse up a slope around a corner with maxed out trailer weight. :thumbsup:

 

Agreed. Big road tow generators are a regular for me.

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moggy1968
4 hours ago, damian666 said:

On the MK6 the traction control system is all four wheels or not at all. The TC monitors the speed of all four wheels at all times and compares those speeds continually.The TC has no controlling connection to the differentials in any way and solely acts by applying brakes to the wheels if it gauges if one is going too fast. Obviously if the truck is in 2wd then one of the front wheels cannot accelerate faster than it's chums but it still provides input to the TC system. If for example the truck is driving along and the driver wellies it or hits ice (for the sake of this example you keep going straight forward) and the rear wheels both accelerate by drive applied via the rear axle, then the TC system sees them both suddenly speeding up. It can't specifically do anything about it because it is based on a L-R disparity but if one of those spins even faster (ie truck starts to go sideways) than the other it will attempt to slow the faster one.

You can entirely disengage the TC and ABS at any speed if you really want to but the ECU is not set up to have that so gets upset.

I know it doesn't have anything to do with the diff, I said it's a bit like a locking diff because I was trying to describe the effect it has on traction from the driving seat. I know it works by utilising the ABS system.

In 2wd there is no drive to the front axle, so there will be no traction control. You can't have traction control when there's no traction! If that were the case, there would be no need for 4H,  but there will be ABS as you say on all wheels at all times and braking to the wheels, helping to control slip, slide and yaw front and rear. It appears thats exactly what your describing with your description of rear wheels spinning later in your post (where the matter of the front wheels appears to have mysteriously vanished!). I think your confusing VSC with TRC. As I understand it VSC works on both axles in both 2WD and 4wd as I think you were describing, TRC, or traction control only works on the driven axle. It detects when a wheel is slipping (under load) and lightly applies the brake, through the abs system, causing power to be transferred to the non slipping wheel, a bit like the old trick of lightly applying the handbrake (and no I don't mean it works by working on the handbrake :)  It's an analogy, like the diff thing ;) ). Clearly that can't happen if the axle isn't driven. 

The ability to disconnect them is limited in standard trim, but clearly, as it is computer driven there are ways around that should you wish to and you have the technical know how, but thats different to what was being discussed.

 

I managed to find a similar thread from a while back that explains how to manually disconnect VSC and stop the engine cutting back using the dash mounted button. It does reactivate though I think at 30mph

Anyways I think we're going round in circles here (so to speak) so I'll leave it there

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moggy1968
On 06/12/2017 at 12:13, Chris Bryant said:

As a sidenote, the Heater Booster switch. Is that just an idle increaser.? If so, I assume when driving (cold), it puts strain on the brakes/auto box, as it's trying to rev whilst stationary at a junction.??

This from a road test by car products tested

'Further to that, to get you toasty warm quicker in winter time, the Hilux features a Power Heat system. Push the button, and the Toyota’s revs rise to around 1,200 rpm, and warm air comes out the vents almost immediately. Apparently heater elements within the system provide warm air quicker than the car, and the higher revs also help heat the engine up quicker too. Brilliant bit of kit, and those of you working outside all day will appreciate this bit of tech. For summer, there’s air conditioning and all-electric windows.'

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