Is a remap possible?

[jumpingjehovahs]

Hi all,

 

I have a 2010 RX450H SE-L Premier that I’ve now had for a couple of months.

 

While completing and 800 mile round trip last week not once did I wish for any more power as the car is smooth and fast.

 

However, not speeding, a/c on low, tyre pressures checked etc etc I did wish for slightly better MPG, which was disappointing considering I was on a run.

 

I’m not expecting the world and was fully prepared for reasonable, not mind-blowing MPG. But I would expect more than 32 on a motorway run.

 

So I wondered if anyone had any experience of a remap on one of these and if it was even possible with the hybrid tech?

 

Finally, a picture of my car, just because I love it!

 

 

 

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[Herbie]

I seriously doubt that a remap would be possible and probably even less desirable, but someone with more knowledge than me will hopefully enlighten both of us.

Hybrids get their best economy in town driving, where the hybrid side can do its job. On a long motorway run it really just becomes a 'normal' petrol-engined car dragging around a big heavy Battery or at least that's been my experience up to now. Again, someone may come along and tell us otherwise and that's fair enough - I'm always willing to learn.

[rayaans]

I wouldn't expect more than 32mpg on a run

Bought the wrong car if that's what you were expecting.

[jumpingjehovahs]

Thanks both for your comments so far.

I do agree that the car performs best around town, and hadn’t really considered the whole “big car hauling around loads of batteries” scenario. So very fair point.


As stated, I wasn’t expecting the world and certainly not the 44 mpg that it’s rated at but would’ve expected to crack 35 or so and I don’t believe that to be unrealistic in the summer months.




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[rayaans]

29 minutes ago, jumpingjehovahs said:

Thanks both for your comments so far.

I do agree that the car performs best around town, and hadn’t really considered the whole “big car hauling around loads of batteries” scenario. So very fair point.


As stated, I wasn’t expecting the world and certainly not the 44 mpg that it’s rated at but would’ve expected to crack 35 or so and I don’t believe that to be unrealistic in the summer months.




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It seems to be extremely efficient at 65mph cruise control

I dont have that patience, so I regularly see 30-32 on the motorway. 

[Spacewagon52]

32 mpg on a run? That is interesting, I got around 28 mpg on a motorway run from my RX 300. Where it hits home is in normal driving conditions for me, town and mixed A Roads - 22 mpg.

 

In a normal week, what do you get? Personally I would be very happy with 30 mpg in such a lovely car.

[rayaans]

2 minutes ago, Spacewagon52 said:

32 mpg on a run? That is interesting, I got around 28 mpg on a motorway run from my RX 300. Where it hits home is in normal driving conditions for me, town and mixed A Roads - 22 mpg.

 

In a normal week, what do you get? Personally I would be very happy with 30 mpg in such a lovely car.

Get about 27-30mpg in town but I do quite a lot of short trips. MPG on the motorway in mine on average is about 33mpg but I dont hang around.

Worth remembering that these things weight nearly 300-400kg more than the RX300

[jumpingjehovahs]

32 mpg on a run? That is interesting, I got around 28 mpg on a motorway run from my RX 300. Where it hits home is in normal driving conditions for me, town and mixed A Roads - 22 mpg.
 
In a normal week, what do you get? Personally I would be very happy with 30 mpg in such a lovely car.

I’m pretty happy, but always looking to save a few quid, must be the Scotsman in me...

My commute to work is a pretty mixed 20 mile run, with 30mph, 60mph and motorway stretches. It probably gets around 36 which is wholly decent for a vehicle of its size on that run. My previous car, a VAG 1.6 TDI only got 5 MPG more on that journey.


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[jumpingjehovahs]

It seems to be extremely efficient at 65mph cruise control
I dont have that patience, so I regularly see 30-32 on the motorway. 

No, I’m not sure I’d have the patience for that either. May give that a go on my next short motorway run though and see how I get on, thanks!


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[mrfunex]

We have a 2009 RX450h and get about 31-32mpg average (over the last 25k miles) regardless of whether in stop/start traffic, or howling up the motorway. Given that it’s a petrol, 2+ ton vehicle with fat tyres, the aerodynamics of a small shed and 300bhp, I find that mildly astonishing. I don’t think a remap is possible.

What kind of fuel economy were you expecting? 

[Herbie]

I'm getting a bit more used to mine but believe me, having come from LPG-powered cars to a hybrid, the amount of fuel it uses did bring a tear to my eye in the early days.

The best I've managed is 41.3mpg if I remember correctly, certainly 41.something anyway, on a run, but my daily figure running around town is about 35.1mpg although that's gone down drastically recently with lots of short runs to the tip as we sort cupboards, the loft and the garage .

Around town I keep it in ECO mode, accelerate quickly to speed and then just back my foot off slightly to maintain momentum and it seems to work well.

 

[Mr Vlad]

Worst mpg I've had in mine is 22 when speeding down the M62 home from Leeds. Best I've had is 38.5 going to leeds but keeping to the speed limits. Fully laden my car got just over 30mpg to Skegness and back to leeds. That was damn excellent considering the car was Fully laden. 

I don't know where honest John real mpg for the 450h figure come from. I suppose it is possible to average mid to high 40's but that would need hybrid trained driving. 

The 450h is Not the wrong car for economy runs. Imagine the car without its hybrid. Mpg would be constantly low 20's. 

Don't worry about your mpg. Just enjoy your fabulous car.

[Delphius1]

As has already been mentioned hybrids are more efficient in mixed driving where the car is accelerating and decelerating often. During deceleration the regenerative braking stores the kinetic energy in the Battery and then that energy gets recycled to give a boost under acceleration.

On a steady cruise the electrickery doesn't really get involved, so you're using the internal combustion engine all the time and mpg falls to the same as a non-hybrid.

32 mpg is the same as my '04 RX (actually I can eke out a bit more), I did think the later engines were a bit more efficient. Maybe check tyre pressures as that has a significant effect on mpg with the RXs.

[Jaystar77]

Just on the topic, I've been looking at a remap for my 06 RX350 (more for power than mpg) and there seems to be a few options available.  For reference I'm getting around 28mpg on the daily commute which is spot on for the size of it.

 

http://www.quantumtuning.co.uk/car-remap-tuning-remapping.aspx?Make=Lexus&Range=RX350

https://www.racechip.com/chip-tuning/lexus.html

http://www.dcptuning.com/car-ecu-remap-engine-mapping-chip-tuning-lexus.html

 

They all seem to be mainland UK so a few emails might net you some answers.  After a few 'brown' moments I've decided that the chassis needs some work before I go adding any more horses!

[olliesgrandad]

Just achieved over 33mpg tankful to tankful driving from Gloucester to Fountains Abbey via minor roads across the Peak District (including a trip to flash the highest village in England) with 2 adults 1 small boy and the car stacked up to the roof with clothing and food for a week away. Very pleased. 

[chris_fletcher]

Last tank on my gen 4 RX was 36.6mpg calculated brim to brim, mostly eco as it lets go of the engine quicker and I am tight b*st*rd. if you can live eco and with less than 60mph on the motorway I suspect you would do better than 32mpg. I sometimes do that just to see what I can achieve, usually ~38-40 mpg, it soon drops back at 70mph and over though.Other times I am forced to crawl along through stop start traffic on the M62 which very quickly depletes the Battery and kills the figure but I am still managing average of 35.5mpg over 13 months. The car computer is strangely accurate and it also indicated 36.6mpg for the same tank. I have never had that before, usually car is plus ~10%

[Clive-D]

Thanks both for your comments so far.

I do agree that the car performs best around town, and hadn’t really considered the whole “big car hauling around loads of batteries” scenario. So very fair point.


As stated, I wasn’t expecting the world and certainly not the 44 mpg that it’s rated at but would’ve expected to crack 35 or so and I don’t believe that to be unrealistic in the summer months.




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How is you driving style and what speed do you cruise at - both have huge impact on mpg.

I get on average 33-34mpg from my 2008 400h. I have one of the lightest right feet in the uk!! I do a mix of town, country roads and dual carriageway. I cruise between 65 and 70. On one country road I use every week with 40 and 50 speed limits I get over 50mpg but it is flat and slopes in my favour! Agree fast cruising doesn’t get the best from the hybrid system but the batteries boost performance all the time - if not you’d be getting low 20s mpg. I’ve been running on Battery at 65mpg - it’s great!

Learning to use the car’s weight is a must. I take my foot off as often as I can. Avoid floating the throttle as this keeps the engine running. If you see a corner or a junction coming up, foot off and let the car coast along, you’ll be amazed how long it goes without much slowing down- the car is designed for this and you charge the Battery. Same with gradients, coast onto it and let the gradient build up speed. It’s fun learning little tricks. Even Hamilton backs off early to get the most from his F1 hybrid system - ok, a millisecond, but look how quick he is!

You can’t complain at your 3.5lr V6 petrol giving you 32, ask the Range Rover owners!!

Nice pic too - I like that model, think the new ones are just too big.


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[rayaans]

3 hours ago, Clive-D said:

How is you driving style and what speed do you cruise at - both have huge impact on mpg.

I get on average 33-34mpg from my 2008 400h. I have one of the lightest right feet in the uk!! I do a mix of town, country roads and dual carriageway. I cruise between 65 and 70. On one country road I use every week with 40 and 50 speed limits I get over 50mpg but it is flat and slopes in my favour! Agree fast cruising doesn’t get the best from the hybrid system but the batteries boost performance all the time - if not you’d be getting low 20s mpg. I’ve been running on battery at 65mpg - it’s great!

Learning to use the car’s weight is a must. I take my foot off as often as I can. Avoid floating the throttle as this keeps the engine running. If you see a corner or a junction coming up, foot off and let the car coast along, you’ll be amazed how long it goes without much slowing down- the car is designed for this and you charge the battery. Same with gradients, coast onto it and let the gradient build up speed. It’s fun learning little tricks. Even Hamilton backs off early to get the most from his F1 hybrid system - ok, a millisecond, but look how quick he is!

You can’t complain at your 3.5lr V6 petrol giving you 32, ask the Range Rover owners!!

Nice pic too - I like that model, think the new ones are just too big.


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They've made them bigger to make way for the NX, which is the same size as the RX400h.

[cachaciero]

Bit late to this topic and what I will have to say is based upon my experience with an RX400H.

IMHO the bit that needs re-mapping is the gearbox / electric motor controller. The 450 motor is unlike the 400 already tuned for economy, now given that on a reasonably cross country run mixed motorway / A roads I can see 32- 34 I would have thought that the 450 would be able to get 35-38 on the same journey and maybe better driven to the cars strengths.

However the bit that will kill the mpg figures on the 400 is Mway driving, the fuel consumption drops of a cliff at about 65 and driven hard will soon dip to sub 30mpg, I don't understand why the cut off point is as marked as it is, drag force will increase in proportion to the square of the speed so I have to assume that being a draggy square box the extra 5mph between 65 and 70mph is enough to significantly increase the aerodynamic load at that point.

However there is one other issue that takes its toll on motorway driving. Imagine driving in a file of cars all doing nominally 70 but slowing up to say 60  and then accelerating back to 70 and then decelerating again (M25 scenario )-

Now my 400 decelerating from 70 will often require a touch of brake to get the speed down to an acceptable level in the distance available under these circumstances I will often put it into B mode thus increasing  the deceleration and getting a little extra into the Battery, as the stream speeds up back into D and touch the throttle, now I don't require much energy to get back to 70, the Battery is well up and there is more than adequate electrical energy available to restore speed but the moment you touch the pedal the IC engine springs into life, burning petrol which does not need to be burnt, because a minute or two later you are having to slow again and this really pi???? me off.   That is the one area where my gut feel is that the software really needs a bit of re-working. There appears to be little sensible relation between speed, torque demand (pedal position) and Battery power'

Unfortunately with no access to logic flow diagrams let alone source code it is near impossible to do anything. Someone with the requisite tools and knowledge could probably re-constitute the code but that would require a lot of enthusiasm or money and as we are not talking about races to win on a low volume production vehicle there is little chance of either happening as far as I can see.

 

 

[m4rkw]

If you want better economy the best way to achieve this is to alter your driving style. Brake less, accelerate gently, maintain a constant speed.

Really though, imho, life is short, you've got a great car, just enjoy it and don't worry about the mileage.

[Herbie]

There's a knack to driving a hybrid.

Accelerate briskly to the desired speed and then very slightly back off. You should be able to run on Battery for a while but remember, these are not electric cars and you'll only get a couple of miles by relying on the traction Battery alone.

All the 'B' mode does is to increase engine braking and it's not a very efficient use of the system, which really relies on the use of regenerative braking for maximum efficiency. You get much more charge by braking and it's easy to prove. Next time you're on a long descent put the selector in B and watch the power meter, then put it in D and use the brakes - the power meter will move a lot further down the scale (indicating more charge going into the traction battery) when in D and braking, than in B.

The vast majority of braking is, or should, be done regeneratively by the hybrid system. The idea is to read the road ahead and brake gently. The regen brakes operate until the car is almost stopped (3mph if I remember correctly) and then the traditional hydraulic brakes take over. The only exceptions to this as far as I'm aware is when you have to anchor on in an emergency and the hydraulic brakes come on immediately, or when the traction Battery is fully charged and can accept no more, then again, the hydraulic system takes over.

This is the reason why brake pads and discs last thousands of miles longer on a hybrid.

[m4rkw]

Turns out I know nothing about hybrids and should shut up 😄

[Bluesman]

1 hour ago, m4rkw said:

Turns out I know nothing about hybrids and should shut up 😄

Not at all, if you don't ask you will never know.

[cachaciero]

5 hours ago, m4rkw said:

If you want better economy the best way to achieve this is to alter your driving style. Brake less, accelerate gently, maintain a constant speed.

Really though, imho, life is short, you've got a great car, just enjoy it and don't worry about the mileage.

The theory is fine however try to apply it consistently on the M25 / M4 🙂

[Brian26]

I would just like to get out for a decent run sod the MPG!

Bri