Achievement Ratio: How Well On-Paper Performance Translates into Actual Performance

ssun30

Expert
Messages
2,769
Reactions
6,389
A concept that is rarely talked about in western car media but is talked about increasingly frequently in Chinese car media is "achievement ratio". It measures how fast a car accelerates compared to its theoretical power-to-weight ratio.

The theory is very simple physics: F = ma, where F is force, m is mass and a is acceleration. Also P = Fv, where P is power, F is force and v is speed. Therefore, acceleration is a function of power-to-weight ratio (P/m) given the same speed. In reality, this "power" is not equal to the rated maximum power of the car, since there are mechanical frictions, traction limitations and powertrain calibration that all contribute to losses. But most importantly, ICEs don't make peak power at all rpms and there is no ideal CVT. The ratio of this 'real power used for acceleration' to maximum rated power is the achievement ratio.

In short, the higher the achievement ratio, the more power is used to accelerate the vehicle and not lost in the drivetrain and wheelspin, and the side benefit is better fuel economy. Example of high achievement ratio cars are BEVs, PHEVs and notably ICEVs made by BMW. Example of low achievement ratio cars are American muscle cars that usually rely on brute force.

There is no general consensus on how achievement ratio is defined since it's a very complicated measurement. The most basic form is just dyno-tested horsepower divided by maximum rated power. The value is 0.75-0.9 depending on the driveline (FWD/RWD/AWD) and dyno setup (axle vs. wheel). But this is still an overestimate since it is a static scenario while real world acceleration is a dynamic scenario with more sources for losses. For my calculations, I used a slightly more complicated formula using kinetic energy of the car travelling at 60mph/96kph as the basis to calculate 'average acceleration power'. Here is a table of achievement ratios of all new Lexus products with available data, compared to similar BMW vehicles which are known to have the best achievement ratios among ICEVs.
achievement ratio.png
Conclusions:
>> AWD cars generally have higher achievement ratios despite higher drivetrain losses. This is because they have less wheelspin, so less energy is wasted on creating molten rubber.
>> Lexus ICEVs usually underachieve compared to their power-to-weight ratio. This is a result of very conservative engine mapping, transmission shift strategies, traction control and just general lack of optimization. A negative consequence is Lexus ICEVs usually have worse fuel economy than competitors.
>> The LS 500 is a notable over-achiever. Despite often being called out for overestimated performance, the LS 500 is actually reasonably fast for how heavy it is. The poor real performance of this car is mostly due to the weight. If it could achieve the advertised 4.6s 0-96kph time, it would have higher achievement ratio than most BMWs but unfortunately Lexus is misleading its customers here.
>> The 10-speed also gives the LC 500 a better achievement ratio than the 8-speed RC-F and IS500 FSP. The RC-F could be faster if it had the 10-speed with a transmission cooler.
>> The old 6-speed used on the GX and IS300 is surprisingly good. I think we all remember how the 8-speed Gen.3 IS 350 was a downgrade compared to the original 6-speed Gen.2 IS 350.
>> As expected, most of their hybrids have very high achievement ratios thanks to the instant torque from electric motors and high efficiency. The multi-stage hybrid system is particularly quick considering how little power it has and how heavy GA-L products are.
>> I think it's pretty clear where Lexus put their emphasis on. They spend most of their effort on making their hybrids as efficient as possible, while ICEVs are mostly an after-thought and they are content with them being acceptable.
>> The highest achievement ratio I've ever seen in any car so far is the bZ4X AWD with 0.691. That's over 40% more efficient than most Lexus ICEVs. A hypothetical "IS EV AWD" at ~2100kg with ~300kW/400hp can do 0-60mph in 3.6s even if they make zero efficiency improvements by 2025. That's why I am quite excited about the real world performance of their future BEVs.
ref.png
 
Last edited:

NXracer

Admirer
Messages
939
Reactions
670
no RX?
Is the GX outachieveing the next gen LX? if so excited for the next gen GX.
 

ssun30

Expert
Messages
2,769
Reactions
6,389
no RX?
Is the GX outachieveing the next gen LX? if so excited for the next gen GX.
Well...we don't know the weight and real-world performance figures for the new RX.

Real world test results are highly variable. Two cars are considered to have similar achievement ratio if they are within +-0.01 to each other.
 
Last edited:

NXracer

Admirer
Messages
939
Reactions
670
Well...we don't know the weight and real-world performance figures for the new RX.

Real world test results are highly variable. Two cars are considered to have similar achievement ratio if they are within +-0.01 to each other.
I meant the 4th gen RX 16-22 MYs.

Haha the GX being tuned for a high achievement ratio reminds me of this
 

ssun30

Expert
Messages
2,769
Reactions
6,389
I'm in the process of making a comparison series of Lexus ICEVs across different generations. A trend I found is they have been improving their achievement ratios from 1990 to 2010, but from 2010-2020 they regressed so much that new products during this period are barely more efficient than late-90s/early-00s products. Meanwhile almost every car maker has been constantly improving. And we as Lexus loyalists know how underwhelming 2010s Lexus feel.

"Lexus customers don't care about performance" is a convenient excuse for their poor powertrain optimization during these 10 years. Achievement ratio matters. A low achievement ratio means Lexus is using unnecessarily large engines to achieve the same performance as competitors, and thus the products consume more fuel.

For reference, the average achievement ratio in 2022 is ~0.49. A good ratio is above 0.53. A bad ratio is below 0.45. From 2000 to 2020 BMW improved its average achievement ratio from ~0.47 to ~0.53.

With the exception of the IS300 AWD, which probably has a heavily underrated engine, the 3IS is the worst optimized of all generations. The IS500 wastes 60-70hp and performs like a 400hp modern car.
IS.png

The ES has been improving since 1990. Gen.6 is notably worse than gen.5, but I suspect it's because they hit the traction limit of FWD. The true achievement ratio should be similar to the non-traction limited ES250 at ~0.49 if they bothered giving the ES350 an AWD system.
ES.png
 

NXracer

Admirer
Messages
939
Reactions
670
"Lexus customers don't care about performance" is one way of thinking of it. How about the more common "Lexus prides its reliability over performance so everything is oversized yet performance is way worse"?
 

ssun30

Expert
Messages
2,769
Reactions
6,389
Despite our memory of GS as a fast sports sedan. Its achievement ratio was never that high. It has been underperforming for how much power it has, especially the V8 model.
GS.png

The 5LS is actually the best performing of all generations especially considering it's over half a ton heavier than the original LS400.
LS.png
 
Last edited:

ssun30

Expert
Messages
2,769
Reactions
6,389
RX always had high achievement ratio from gen 1 to gen 3. Gen 4 was a big step backwards.
RX.png
"Lexus customers don't care about performance" is one way of thinking of it. How about the more common "Lexus prides its reliability over performance so everything is oversized yet performance is way worse"?
The LX remained good across all generations. J100 was particularly good. The LX is an example of how high achievement ratio helps reliability. It means the engine can be detuned (especially in the case of 2UZ) for extra reliability. Do you think the IS500 would be more reliable if the engine is detuned to ~420hp because the 50hp extra is wasted anyway?
LX.png
 

ssun30

Expert
Messages
2,769
Reactions
6,389
We also see the LS has by far the worst weight growth. The IS and ES grew by 20%, GS by only 2%, RX by 10%, LX by 14%. But the LS500 is 33% heavier than the LS400.
 

JustADude

Follower
Messages
226
Reactions
149
I'm in the process of making a comparison series of Lexus ICEVs across different generations. A trend I found is they have been improving their achievement ratios from 1990 to 2010, but from 2010-2020 they regressed so much that new products during this period are barely more efficient than late-90s/early-00s products. Meanwhile almost every car maker has been constantly improving. And we as Lexus loyalists know how underwhelming 2010s Lexus feel.

"Lexus customers don't care about performance" is a convenient excuse for their poor powertrain optimization during these 10 years. Achievement ratio matters. A low achievement ratio means Lexus is using unnecessarily large engines to achieve the same performance as competitors, and thus the products consume more fuel.

For reference, the average achievement ratio in 2022 is ~0.49. A good ratio is above 0.53. A bad ratio is below 0.45. From 2000 to 2020 BMW improved its average achievement ratio from ~0.47 to ~0.53.

With the exception of the IS300 AWD, which probably has a heavily underrated engine, the 3IS is the worst optimized of all generations. The IS500 wastes 60-70hp and performs like a 400hp modern car.
View attachment 6148
The pre refreshed 3IS350 probably has a better ratio since it's lighter by 100-150lbs vs the 2021+ models
 

carguy420

Follower
Messages
474
Reactions
590
So at this point, if we want a new fast Lexus that doesn't throw away all its power we basically have to wait for their upcoming BEVs. It's such a stupid excuse that a fast and efficient vehicle can't be reliable.
 

Gecko

Administrator
Messages
4,119
Reactions
9,560
The pre refreshed 3IS350 probably has a better ratio since it's lighter by 100-150lbs vs the 2021+ models

Biggest problem with the 3IS is the super soft transmission tuning of the 8AT over the 2IS's 6AT.

Many of us remember when the 2006 IS 350 first debuted and it was neck and neck with the 335i, sometimes cracking off 0-60 in less than 5 seconds. I think C&D might have even gotten 4.8 at one point? That 6AT and 2GR-FSE combo is some of Lexus' most legendary work... 2GR-FKS was paired to a much softer/less aggressive transmission that neutered power delivery on every model that used it. A real shame...
 

JustADude

Follower
Messages
226
Reactions
149
Biggest problem with the 3IS is the super soft transmission tuning of the 8AT over the 2IS's 6AT.

Many of us remember when the 2006 IS 350 first debuted and it was neck and neck with the 335i, sometimes cracking off 0-60 in less than 5 seconds. I think C&D might have even gotten 4.8 at one point? That 6AT and 2GR-FSE combo is some of Lexus' most legendary work... 2GR-FKS was paired to a much softer/less aggressive transmission that neutered power delivery on every model that used it. A real shame...
2IS is by far the best generation. We need a new boosted 300hp t24 + 10 speed combo to be faster vs 2IS 350. And a detuned v35 if it really wants to compete with an M340
 
Messages
1,509
Reactions
2,433
Biggest problem with the 3IS is the super soft transmission tuning of the 8AT over the 2IS's 6AT.

Many of us remember when the 2006 IS 350 first debuted and it was neck and neck with the 335i, sometimes cracking off 0-60 in less than 5 seconds. I think C&D might have even gotten 4.8 at one point? That 6AT and 2GR-FSE combo is some of Lexus' most legendary work... 2GR-FKS was paired to a much softer/less aggressive transmission that neutered power delivery on every model that used it. A real shame...

Lowest was 4.6. Same time as the IS F if the latter launched poorly.
 

NXracer

Admirer
Messages
939
Reactions
670
Tire and traction control technology back then was pretty poor, much less grip than today. IS-F was overpowered for its day. Still has better achievement ratio than later IS500...
Sidenote. I do see some IS-Fs trying to do street takeovers currently but them b58 boys are ruling with an iron fist.