S-plus - Is it really 'fake'

[GoZoner6]

My contention is that S+ is about performance and, as Honda says, engagement but S+ is definitely not about 'fake' shifts. Every single YouTube personality (and I've seen them all in every language) claims 'shifts are fake'. Honda focuses on engagement and has not mentioned performance, that I've seen. This Honda position might suggest I'm wrong; but I'll explain.

The singular reason for a transmission in non-hybrid, IC engines is to keep the engine in its power band. To achieve that, manufacturers adjust gear ratios (and the spacing between gears) so that shifting, whether by a manual or automatic, keeps the engine revving in the desired RPM range. Sometimes to maximize torque; other times to maximize power (top speed). Doesn't the same apply to Honda's hybrid system?

The Honda e:HEV system connects the ICE output to a generator motor that produces electricity. That electricity is used to 1) charge the battery, 2) power the wheel drive motor, or 3) both. The faster the generator turns the more electricity that is generated (think windmills); if directed to the wheels, more electricity means more acceleration (or power overcoming aero-drag at higher speeds). We know this to be true because when 'brake torquing' Honda e:HEV cars, Honda sets the engine RPMs to the max, and keeps them there, in order to produce the fastest acceleration. So, what is S+ about?

S+ allows the driver to keep the engine rpms high, if desired, thereby generating more electricity which can be used for acceleration. (Or used for recharging the battery if the pedal is not demanding acceleration). Just like a traditional manual or automatic transmission, S+ allows the engine to spin at the optimal RPMs to generate electricity. As a side benefit, the higher reving engine generates sound and the action of shifting with the paddles increase engagement.

But, it is all about generating electricity at higher RPMs.

Makes sense?

 

[qlaval4]

Using the S+ Shift function doesn’t add real gears, as the Prelude electric motor only have a single direct-drive gear. No transmission in the Prelude, none. At highway speed, a clutch may engage the ICE to drive the wheels directly, because it more economical to do so and/or because it can act as power booster. For car enthusiasts, part of the joy of driving is choosing gears yourself. The act of shifting is an experience many aren’t ready to give up. So, to fulfill that wish with hybrid cars Honda invented the S+ shift function.

So yes, the feeling of sensing/hearing a gear shift is simulate, as there are no gears in the Prelude hybrid setup.

There are 2 electric motors, one to move the wheels and one to generate power to the battery.

The S+ function is able to make the sensation of shifting more "real", by making the generator motor (ICE) modulate its RPM to fit the one made by a regular motor who is shifting real gears. It's just modulating the RPM of the ICE to enhance the illusion of a real gear shifting. The ICE revs, blips for downshifts, “holds gears” on command, and more. Doing so hurt efficiency, that's why when using S+ you will burn more gas than if you don't use the S+. More using S+ mode will add to the 0-60mph time by about 1.5 sec, because instead of a seamless power delivery for maximum performance you will have a system that goes up and down. The only advantage of S+, at high RPM the ICE generates more electricity for the battery but at an added cost has this is not done at the economical sweet spot. More that surplus of electricity doesn't push the electric motor to give more torque, it just fills the battery faster...

 

[GoZoner6]

I think you've described the standard view of S+; I'm suggesting something different.

In a traditional transmission, gears exist for one-and-only-one reason - to keep the ICE in its optimal torque/power band. In addition to what you describe, the S+ button exists to keep the e:HEV ICE at its optimal electricity output band - which is high-rpms.

So, for spirited driving, where you want acceleration, use the S+ button to keep the revs elevated, thus providing more power to the front-wheel drive motors.

You said "It's just modulating the RPM of the ICE to enhance the illusion of a real gear shifting"; I'd say "It is allowing you to modulate the RPM of the ICE engine to enhance electricity generation and thus acceleration"

 

[qlaval4]

Where I differ a little bit, is where the enhance electricity generation from high RPM is only charging the battery faster, the acceleration is not impacted as it received the same amount of power from the battery. Changing the recharge rate of the battery doesn't change the output power of the battery, only the depression of the accelerator does, and it does that in the same manner for either a low or a full battery. A 1/4 full battery give the same output as a full battery, only the duration of the output is changed before the generator goes on again. If it was like you've said, the 0-60 would be faster with the S+ on, but in reality the 0-60 is faster by 1.5 sec when it is off.

 

[GoZoner6]

Like you said, the 0-60 time is not faster w/ S+ but that is because the engine RPMs can't be held a the maximum with S+. The fastest time is with 'brake torque' which holds the RPMs at the limit. But that brake torque just proves the point - Honda produces the best 0-60 at maximum RPMs; we get to use S+ to produce more power at higher RPMs - if is not 'fake' it is real power at higher RPMs.

Honda could replace S+ with a 'B' ('boost') button - hit the 'B' button and the engine stays at max rpms until the 'B' button is pressed again. That is, the 'B' button lets the driver enter a 'brake torque' like mode on demand. (The car would drone, and not be engaging, but it would produce maximum power.)

 

[qlaval4]

 

[Alfettaman47]

In the lower 'gears' the system also uses more regenerative braking as you ease off the throttle. Driving the car in a spirited way, you can drop down a 'gear' as you start to turn in, and actually feel the front end of the car tuck into the corner a bit more tightly.

Similarly, as you exit the corner and start to open the throttle more, changing up a 'gear' helps to straighten the car's attitude. In this way, the S+ system can create a genuine effect when the car is driven swiftly through a series of bends, by directly influencing the vehicle's rotation/turn-in.

That said, I guess a lot of Preludes will never get driven like this...!

 

[BlueTiger]

Let me add two more things:
1. in NO S+ mode, if you ask for something less than 100% of power, the system simulates the gear change by himself, frankly speaking I do not why... more fuel for nothing...
2. More eletric output from the motor can not be used because for warranty reasons the power output is limited to 184HP. In other countries the power is 16HP more... But in Italy they have to give 8Y warranty...

 

[qlaval4]

...
2. More eletric output from the motor can not be used because for warranty reasons the power output is limited to 184HP. In other countries the power is 16HP more... But in Italy they have to give 8Y warranty...

In Canada it's 200HP and we also have an 8 years/160,000km warranty on the hybrid system.

 

[BlueTiger]

wow... I am so gelous... anyway the power reduction is for silence and pollution too... very restictrive law here... mrs fondercazzen in germany is really crazy... and I am avoiding the right bad words....

anyway, if you can ask for the canadian map file to your dealer I can give you 100 euro by paypal to you and 100 to your service responsible... just in case let me know in pm...

 

[PR76UDE43]

wow... I am so gelous... anyway the power reduction is for silence and pollution too... very restictrive law here... mrs fondercazzen in germany is really crazy... and I am avoiding the right bad words....

anyway, if you can ask for the canadian map file to your dealer I can give you 100 euro by paypal to you and 100 to your service responsible... just in case let me know in pm...

The power in Europe is not reduced. It's just a quirk of how they report power figures. The reduced figure is the peak output of the main electric motor, whereas in North America they use a 'combined' figure.

 

[BlueTiger]

wow... that's so impressive... do you have more details mate?

 

[PR76UDE43]

wow... that's so impressive... do you have more details mate?

European regulations are that the power presented must be that of the primary propulsion source. In the e:HEV system thats the electric motor, which is exactly 184PS. The US regulations are that they can use peak combined output, which is higher as at higher speeds the engine also clutches up and provides additional power directly and not just from the electric motors, resulting in a total of 200hp.

Regulation No 85 of the Economic Commission for Europe of the United Nations (UN/ECE) — Uniform provisions concerning the approval of internal combustion engines or electric drive trains intended for the propulsion of motor vehicles of categories M and N with regard to the measurement of net power and the maximum 30 minutes power of electric drive trains

3.3. For hybrid electric vehicles (HEV), the tests shall be carried out separately on the internal combustion engine(according to Annex 5) and on the electric drive train(s) (according to Annex 6).

Whereas in the US...

SAE J2908 Vehicle System Power RatingSAE J2908-2023

I'm not sure where the rumour that it was detuned due to emissions or anything started but I've seen it mentioned around in a few places. If you think about it though it's clearly nonsense. The stats report identical peak torque figures for both markets, and it's already an incredibly efficient and low emissions vehicle. The simple fact that you can still buy a 4L twin-turbo V8 new in Europe makes the theory illogical. The final nail in the coffin being that when you pull up the US spec sheet and Europe spec sheet for the Prelude everything is identical across both. See here and you'll see that 184 figure, as [Electric motor power 184 Hp @ 5000-6000 rpm.].
Not to mention the Prelude is rated to LEV IV SULEV30 in the US, and Euro 6e-bis in the EU, of which I'll let the stats speak for themselves:

Pollutant Limit	LEV IV SULEV30 (US)	Euro 6e-bis (EU)
NOx + NMHC (Gasoline)	~18.6 mg/km	128 mg/km (Combined)
NOx (Diesel)	~18.6 mg/km (Combined)	80 mg/km (NOx alone)
Particulate Matter (PM)	~0.62 mg/km	4.5 mg/km

TLDR: in the US they measure peak mechanical output power of the entire system. Europe measures the peak output of the power source itself.

and don't get me started on Honda's braindead decision to call this drivetrain a CVT...

 

[PR76UDE43]

Where I differ a little bit, is where the enhance electricity generation from high RPM is only charging the battery faster, the acceleration is not impacted as it received the same amount of power from the battery. Changing the recharge rate of the battery doesn't change the output power of the battery, only the depression of the accelerator does, and it does that in the same manner for either a low or a full battery. A 1/4 full battery give the same output as a full battery, only the duration of the output is changed before the generator goes on again. If it was like you've said, the 0-60 would be faster with the S+ on, but in reality the 0-60 is faster by 1.5 sec when it is off.

More directly back on topic it isn't actually quite that simple. There's a real mechanical physics reason the car is slower to 60 when rowing through the 'fake' gears in S+ and it's not just because of the brief deliberate delays they put in to simulate the momentary torque drop of a clutch.

To simplify the concept, just forget there's actually two electric motors in the system. Imagine we simply have one, the battery, and the engine.

So now to the power numbers.
The engine alone can output ~101kw(141hp) at its peak.
The electric motor can output ~137kw(184hp) at its peak.
The peak system output is ~149kw(200hp). How do we get to that 200hp figure and why does that matter?

Well, the Prelude has a 1.06 kWh battery on board to power the electric motor. This is important to note as batteries have their own peak power output, and it typically scales with their capacity somewhat. This is why a electric city car with a 30kWh typically doesn't have much more than 100-200hp, and the 1000hp super electric saloon cars often have batteries around the 100kWh mark. In comparison, a 1kWh battery is absolutely tiny, and your typical 1kWh battery can output perhaps 35-45hp at most.

So if the battery is only capable of ~40hp, how is the electric motor capable of 184hp? Simple. The engine. This is where that second electric motor we decide to ignore earlier comes back. Let's instead just call it a generator, again for simplicity. So what's happening at full throttle where we're putting 184hp to the wheels is a simple bit of additive math. The electric motor is sucking down ~40hp from the battery, and then the missing 144hp from the generator attached to the engine. What helps even reinforce this argument is the math on the figures itself. Electric motor can output 184hp. 184 minus a maximum 141 from the engine is 43hp. Almost exactly the amount the typical battery of the size in the Prelude can output. (P.S. it's obviously not quite this simple and there's a lot of blending and overlap going on, but this is the rough principle of how it works)

So why does that matter to the original point of the thread? Well it means that when you 'upshift' into a higher 'gear' the actual real RPMs of the engine drop, and therefore the current power output of the engine drops, and therefore the power output of the entire system drops. Meaning the growing surge in power you feel as you then climb back through the revs is real and not simulated. The gears are not, but the effect of the revs are real just like they would be in a real gearbox. THAT is why it is slower to 60 in S+, your actual peak power output IS lower during those lower RPM moments due to 'upshifts'. It's also why when you floor it not in S+ the car will sit at max RPM and scream their the entire way, because it has to in order to be able to put the power to the wheels, not to keep the battery topped up. It's also why you can't go more than ~20mph without the engine kicking on even if the battery is full, because the battery physically can't push out enough juice to turn the motor hard enough to get you going any faster.

So yeah @GoZoner's claim of using S+ in order to keep the revs higher to have more power ("It is allowing you to modulate the RPM of the ICE engine to enhance electricity generation and thus acceleration") is correct. I imagine you'll find around a track you will get better performance using S+ than you would without it as you won't be waiting for the engine to be rev'd back up to full power as long as you would without S+. It just doesn't apply in a straight line 0-60 test as at no point are you lifting the throttle which would have allowed the system to severely drop revs in the default mode, whereas around a track you will be letting off the throttle for corners and so want the power ready and waiting for you to mash it out the bend. And yeah a 'boost' button that just held the engine the entire time at peak power RPM would be the fastest option, but damn would it be annoying to listen to.

EDIT: Edited to remove mention of planetary gearset, Honda does not use one and instead has a direct drive clutch only used for cruising. The reality is the Prelude actually cannot ever put 200hp 'to the wheels'. So the opposite is actually true for the whole Europe vs North America power figures, the real true power of the car is 184hp, not 200hp. The 200hp figure is just the mathmatical peak of the engine's output plus the batteries output, not the peak amount of power possible to output to the wheels.

 

[qlaval4]

Thank you for taking the time to write it all.
Very instructive.

 

[PR76UDE43]

Here's a little chart helping to visualise what's going on during a straight line full throttle pull:

I also charted a little simulation help. Ignore the exact numbers and just look at the shape of the graphs. This simulates approaching a corner at speed, lifting off the throttle, then accelerating back out of the corner.

Here in non-S+ you can see the revs drop dramatically, then climb back up as you accelerate. Dropping total power to almost 0hp right as we hit the throttle to accelerate back out of the corner.

In contrast, in S+ mode you can see the backing off of the throttle, but then downshifting to keep RPM high, so the total power available is notably higher at the moment we get back on the gas to power out of the corner letting you command almost all of the total power of the car instantaneously. In the real world this results in exactly what Honda promised, a more responsive and enjoyable drive.

 

[GoZoner6]

An annoying drone or not, a boost button that kept the engine at maximum revs located on the steering wheel (where the later CR-Z models had for battery output) would be great fun.

 

[PR76UDE43]

An annoying drone or not, a boost button that kept the engine at maximum revs located on the steering wheel (where the later CR-Z models had for battery output) would be great fun.

Well I guess constantly tapping the downshift paddle in S+ is about as close as we can get, probably feels rather weird though. Out of curiosity, what happens if you just hold the paddle?