Recommended Posts

 

As far I remember while I was doing max speed which I assumed was 155mph speedometer was showing almost 160. 

There is also one more benefit of showing you that you are going faster - consumption. If car thinks it is going faster then it assume too that it travel further which then influence fuel consumption indications. It is always better to burn 10L of petrol and do 150km rather than 140km :)

  • Like 1

Share this post


Link to post
Share on other sites

Indeed - as I said I see the reason why manufacturers would like to overestimate the speed as much as possible - you going faster, car consumes less... perfect life.

Share this post


Link to post
Share on other sites

On 11/1/2017 at 10:01 PM, Glover said:

The EU and the majority of countries including the UK base their regulations on UN regulations https://www.unece.org/fileadmin/DAM/trans/main/wp29/wp29regs/r039r1e.pdf.  The UN legislation is where the variance comes from.  Isn't Google wonderful!

That is great, but where it says that speed indicated cannot exceed 10% or real speed? The only formula provided is:

0 ≤ (V1 - V2) ≤ 0.1 V2 + 4 km/h (or +6/+8), I believe +8 applies to our cars (cars over 200km/h maximum speed)

So if you are riding scooter, then it is ~ 0-21.2%

0 ≤ (30 - 23.64) ≤ 0.1 *23.64 + 4 or 0 ≤ (6.36) ≤ 6.364

The car below 200km/h top speed e.g. CT/Yaris ~ 0-27.25%

0 ≤ (30 - 21.825) ≤ 0.1 *20 + 8 or 0 ≤ (8.175) ≤ 8.1825

The car above 200km/h top speed e.g. IS250, GS450h (or Bugatti) ~ 0-33.33%

0 ≤ (30 - 20) ≤ 0.1 *20 + 8 or 0 ≤ (10) ≤ 10

In other words it would be within the law if car would indicate that you are doing 150MPH, when real speed is only 100MPH. In my personal experience in all car I had speedometers were never outside of 5-15% range, the most grossly overestimated speeds were on my Mazda Mx-3 ~ 18%, me running much larger rims took that down to like 10%, and most underestimated was on BMW525 with engine swap for M60B40, I don't know what would have been figure on standard rims as I have never had standard rims on it, but on 19 inch rims the speedo was close to perfect, still ~2% more than real. My father on another hand had Freelander with off road wheels. The standard wheels were something like R16/~215 and ~ 55/65 tires and the rims tires he had was something like ~ R17/255/85 and speedo was showing 5/8% less than real speed.

BTW, the law which applies in UK is based on EU directive which is based on above document from UN... 

Share this post


Link to post
Share on other sites

Surely it can't be right all the time unless using a gps based sysytem, as due to tyre inflatation and wear, which both impact the rolling circumference, either a wheel or gearbox or ecu pickup would only be counting revs, and extrapolating distance travelled, rather than measuring actual distance travelled. 

Share this post


Link to post
Share on other sites

Indeed, that is why by the law it must never be less and I guess just in case of effects you described can be more. However, in my personal experience it is always more - enough to be suspicious of foul play. Looking from manufacturers perspective - if you set every car to exaggerate by 10% you will get 10% more income from servicing, because people will have to service car more often, you will probably get more sales, because many owners looks at the total mileage as defining factor of value for both new and used cars, the car will indicate 10% better fuel consumtion, the overall driver perception will be that car is 10% faster. What are downsides? I don't see any. It is sometimes amazing to think about it... my IS250 has 172k miles, but really has "only" done ~ 154k.

Anyway... back to the topic - the GS450h in video most likely does 155MPH when it indicates 161MPH... I cannot claim whenever that is because of limiter in ECU or because it doesn't have power/gear ratios to go any faster.

Share this post


Link to post
Share on other sites

I am reasonably confidant the GS450H is capable of a higher top speed if the limiter were to be removed. This limiter does exist according to Lexus. The car does not struggle to the indicated 155 mph, and I would guestimate the actual top speed to be about 20 mph indicated over the 155 figure if the limiter could be removed.

John.  

Share this post


Link to post
Share on other sites

Is the limiter something to do with maximum permitted revs of the various motors? 10000rpm for one of the electric motors?

I have noticed that S Wales is nearer now I have new rear tyres.:smile:

John

Share this post


Link to post
Share on other sites

1 hour ago, OldTrout said:

Is the limiter something to do with maximum permitted revs of the various motors? 10000rpm for one of the electric motors?

That's my understanding. The RC300h is limited to 112mph simply because it doesn't have the additional power splitter device the GS/RX have to reduce the electric motor rpm

Share this post


Link to post
Share on other sites
1 hour ago, OldTrout said:

Is the limiter something to do with maximum permitted revs of the various motors? 10000rpm for one of the electric motors?

 

I expect is it to match the German brands with the 'gentleman' agreement VAG, BMW and Mercedes have to limit top speeds on the Autobahn.

Share this post


Link to post
Share on other sites

I have done some calculations for theoretical speed against engine revs. 

With MG1 being held stationary and the engine doing 6500 rpm the top speed would be 152 mph. If MG1 is driven in reverse the theoretical top speed for 6500 rpm is well in excess of 200 mph without over revving of any component. This of course makes the assumption that the engine has sufficient power which it does not.

John.

  • Like 3

Share this post


Link to post
Share on other sites

MG1? Motor/Generator? 

I have a lot to learn :~)

 

Share this post


Link to post
Share on other sites

On 11/5/2017 at 8:05 PM, Britprius said:

I have done some calculations for theoretical speed against engine revs. 

With MG1 being held stationary and the engine doing 6500 rpm the top speed would be 152 mph. If MG1 is driven in reverse the theoretical top speed for 6500 rpm is well in excess of 200 mph without over revving of any component. This of course makes the assumption that the engine has sufficient power which it does not.

John.

Would you shed any light how you came to these numbers?

I am not challenging your calculations, just wanted to point out that MG1 and 2 only matters if there are battery power to power them, which in case of sustained performance would last less than a minute. Basically, in practice that means you might get higher top speed for few seconds and then cruise at lower speed. Again I would draw comparison with GS350 (same engine) which has higher gear ratio and it is known to reach just about 160MPH, somehow I cannot imagine GS450h making much more than that and if it does it would be for very short time.

Share this post


Link to post
Share on other sites

You missed the main point: This of course makes the assumption that the engine has sufficient power which it does not. 

Britprius is not saying it will do 200mph but if you will put 5L engine with 500bhp and leave the gearbox it should go up to 200mph without reaching crazy rev like 15k rpm. Of course don't try to do that as gearbox also got limits on the max torque not just rpm :)

As for sustained max speed it just mean limit is not on the gearbox side but on the engine and battery.

  • Like 1

Share this post


Link to post
Share on other sites

I've found very good video: 

 

It got battery meter and power displayed so we know what is happening. 

We can see car is accelerate with the battery assistance at 250KW. Then he brakes and accelerate again with battery deplated at 220KW - you can compare the difference if you want.

Then at 155mph it hit the limiter - observer that speedo is showing 260kmh which is 161mph. So limiter is set to the real 155mph. At that time power output is dropping to 190KW (255bhp) and is stable engine only output.

That means if limiter weren't there engine still got like 40bhp to get extra 10-20kmh.

 

 

  • Like 2

Share this post


Link to post
Share on other sites

That video has answered my initial question. It very much looks like the V6 is quite capable of achieving the advertised potential unaided, and continuously (fuel tank  allowing!).

I'm seriously impressed with the performance from what's been described as a "Pensioner's Car", but travelling at ~260kmph at night with traffic? I've seen too many Russian dashcam videos :~)

Interesting responses, guys, Thanks all.

Share this post


Link to post
Share on other sites

What rev needle? :wink3:

It's well beyond when the clutch engages to go into 'overdrive', circa 65mph/104kph.

Maybe the driver lifted off? - although I don't see him closing on any vehicles to cause him to lift.

Share this post


Link to post
Share on other sites
19 hours ago, Linas.P said:

Would you shed any light how you came to these numbers?

I am not challenging your calculations, just wanted to point out that MG1 and 2 only matters if there are battery power to power them, which in case of sustained performance would last less than a minute. Basically, in practice that means you might get higher top speed for few seconds and then cruise at lower speed. Again I would draw comparison with GS350 (same engine) which has higher gear ratio and it is known to reach just about 160MPH, somehow I cannot imagine GS450h making much more than that and if it does it would be for very short time.

Calculations as folows:-

Engine revs 6500 divided by gear ratio with mg1 stationary 3.266 to give wheel rev per minute = 1990 rpm x tyre rolling circumference (81.7/36 = 2.27 yds) = 4517.3 yds per min

4517.3/ 1760 yds per mile = 2.567 miles per minute x 60 for mph = 154 mph some of the figures are rounded for calculation. It should be noted that 6500 rpm is not the maximum engine speed of the GS450H

John.

  • Like 1

Share this post


Link to post
Share on other sites
15 hours ago, Farqui said:

What rev needle? :wink3:

It's well beyond when the clutch engages to go into 'overdrive', circa 65mph/104kph.

Maybe the driver lifted off? - although I don't see him closing on any vehicles to cause him to lift.

For me he just hit the limiter and ignition cut off cause it.

Share this post


Link to post
Share on other sites
On 11/7/2017 at 11:45 AM, WSandME said:

but travelling at ~260kmph at night with traffic? I've seen too many Russian dashcam videos :~)

To be honest at night it is almost safer... less cars and in Germany that is quite normal, simply they have strong lane discipline and they do anticipate car to fly past in unrestricted areas, therefore they won't cut you off and they would not just sit and hog middle or outside lane doing 60MPH like in UK. 

GS450h is really great car for it's performance and economy.... I wish they make 2 doors version of it (RC perhaps...:whistling: ).

Share this post


Link to post
Share on other sites

I like the dash displays, the wheels into battery bit doesn't show on mine, it's a different display.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now