2014 PCX 150 - speed for best economy

[TheMaverick]

The built in gauge is fairly accurate except just after filling up from near empty when it takes a while to settle down - mine seems to be within a few mpg compared to real figures. Why not just use that and ride for the conditions or limits of the road and with a personal preference for speed within that.
Remaining fuel seems good - from near brim I can get about 135mpg and 230 miles trip soon as the bar starts flashing. I pushed it once and did just over 240 miles and still had duel left.

Mine's a 2014 model - so no trip computer - only the fuel gauge.

So is mine, '14 reg LED model. No trip computer but the meter has a trip miles function so I reset it each fill-up (it's one of the button presses - mpg, trip, total) but as for economy, the built-in mpg (or litre) gauge is very good so why bother with anything else.

Mine only has total distance and trip distance - no MPG.

I do reset the trip distance counter each time I refill, but it's only of limited use on long & hard runs as I can be down to flashing reserve in as little as 125km or 150km+ - unfortunately in this part of the country the gas stations are somewhere around this distance apart (give or take a little), which is what makes it "interesting" into a strong headwind. Case in point; refueled in Picton the other day - passed through Blenheim without refueling (29km away) on my way to Kaikoura - tail wind. Made it to first pumps with last segment flashing. Return journey had last segment flashing back at Blenheim (so 29km shorter) (and that was after throttling off a bit for the last 1/4 of the journey because I didn't like what the fuel gauge was doing).

[iceman]

I thought it gave mpg or km/l -switchable.

[gn2]

I thought it gave mpg or km/l -switchable.

New facelift version yes, original body versions don't have fuel computer.

[TheMaverick]

I thought it gave mpg or km/l -switchable.

I wish it did - would be great.

To make it even worse, even though I bought in 2015, they weren't selling the 2015 models in New Zealand until about ... now (something to do with getting rid of old stock) (at least they dropped the price). Knowing what I do now, I'd probably be better off with a Forza 300 for longer trips on open road ... but they don't sell them here new at all it seems

[ONTWOWHEELS]

Thanks. Mine is a 150, with 5.9l tank. At around 50 km/hr I get about 250km per tank, but wide open only 120 to 150km depending on wind (to start of last segment flashing).

Please forgive a little piece of advice.
Do not open full throttle to one cylinder engines for a long period of travelling.
They do not like this and they will brake down sooner thn using up to 3/4 of throttle and usually you gain little in higher speed and it takes much time to do so.

If you have a top speed of 115 kms/h for example with open throttle you must travell with a speed of 105 the most and 3/4 of throttle opened. In this way of use you will have zero problems but near the speed limiter all the time is bad for the engine.

If you want more travelling speed you should go to higher cc engine and a FORZA 300 or SH 300 but with them you will have to travell somewhere 10 kms below their top speed if you want to see 100.000 + kms to your counter without any engine problems.

But you will not have low consumption as with PCX.

The key words are <<keep the throttle somewhere between the 1/2 and 3/4>>.

Also mind about servicing.
A clean air filter and a proper valve adjustment are key factors to low consumption.
Hope i helped.

[TheMaverick]

Thanks. Mine is a 150, with 5.9l tank. At around 50 km/hr I get about 250km per tank, but wide open only 120 to 150km depending on wind (to start of last segment flashing).

Please forgive a little piece of advice.
Do not open full throttle to one cylinder engines for a long period of travelling.
They do not like this and they will brake down sooner thn using up to 3/4 of throttle and usually you gain little in higher speed and it takes much time to do so.

If you have a top speed of 115 kms/h for example with open throttle you must travell with a speed of 105 the most and 3/4 of throttle opened. In this way of use you will have zero problems but near the speed limiter all the time is bad for the engine.

If you want more travelling speed you should go to higher cc engine and a FORZA 300 or SH 300 but with them you will have to travell somewhere 10 kms below their top speed if you want to see 100.000 + kms to your counter without any engine problems.

But you will not have low consumption as with PCX.

The key words are <<keep the throttle somewhere between the 1/2 and 3/4>>.

Also mind about servicing.
A clean air filter and a proper valve adjustment are key factors to low consumption.
Hope i helped.

Thanks.

Unfortunately, Honda don't appear to sell the Forza 300 in New Zealand. I thought about getting a Fireblade, but suspect that keeping it's throttle at 3/4 would probably get me in trouble

I've made the conscious decision not to get the valve clearances checked as often as the book recommends; I'll be doing around 18,000km per year on the bike and over a 3 year period the servicing cost was going to be about 1/2 the cost of the bike - so I'm going to do most of the servicing myself and leave things like valve clearances for greater intervals. I discussed this with a dealer and they said "it's not a particularly high-revving engine" and "would be fine to leave". We kinda agreed that the Honda schedule was basically "just being kind to dealers".

[ONTWOWHEELS]

Thanks. Mine is a 150, with 5.9l tank. At around 50 km/hr I get about 250km per tank, but wide open only 120 to 150km depending on wind (to start of last segment flashing).

Please forgive a little piece of advice.
Do not open full throttle to one cylinder engines for a long period of travelling.
They do not like this and they will brake down sooner thn using up to 3/4 of throttle and usually you gain little in higher speed and it takes much time to do so.

If you have a top speed of 115 kms/h for example with open throttle you must travell with a speed of 105 the most and 3/4 of throttle opened. In this way of use you will have zero problems but near the speed limiter all the time is bad for the engine.

If you want more travelling speed you should go to higher cc engine and a FORZA 300 or SH 300 but with them you will have to travell somewhere 10 kms below their top speed if you want to see 100.000 + kms to your counter without any engine problems.

But you will not have low consumption as with PCX.

The key words are <<keep the throttle somewhere between the 1/2 and 3/4>>.

Also mind about servicing.
A clean air filter and a proper valve adjustment are key factors to low consumption.
Hope i helped.

Thanks.

Unfortunately, Honda don't appear to sell the Forza 300 in New Zealand. I thought about getting a Fireblade, but suspect that keeping it's throttle at 3/4 would probably get me in trouble

I've made the conscious decision not to get the valve clearances checked as often as the book recommends; I'll be doing around 18,000km per year on the bike and over a 3 year period the servicing cost was going to be about 1/2 the cost of the bike - so I'm going to do most of the servicing myself and leave things like valve clearances for greater intervals. I discussed this with a dealer and they said "it's not a particularly high-revving engine" and "would be fine to leave". We kinda agreed that the Honda schedule was basically "just being kind to dealers".

You are absolutelly right !
Sorry to hear about not selling FORZA and i assume SH 300 to New Zealand.

I also do servicing by my self but i have good tecknicians for something i do not want to deal with or to ask questions. They say that you must not bother about valves before 12.000 kms to check them for PCX. For SH it's another story because it has another system of valves and they must be checked by the book every 24.000 kms but usually we do so every 50.000 or some of us never...

PS Fireblade is a beautifull piece but it has not the consumption o a PCX.

[TheMaverick]

PS Fireblade is a beautifull piece but it has not the consumption o a PCX.

I have a theory about the Fireblade - I reckon it goes so fast there wouldn't be time for the fuel to run out!

[ONTWOWHEELS]

PS Fireblade is a beautifull piece but it has not the consumption o a PCX.

I have a theory about the Fireblade - I reckon it goes so fast there wouldn't be time for the fuel to run out!

LOL you are right !
It drinks like a sailor does like my previous FAZER without injection...

[DeaninMilwaukee]

I would expect like with most vehicles the pcx will get its best " real world " fuel economy at whatever minimum speed is required to have the variator in the " top " gear position.

I don't have a tach for my 2013 pcx, but I would expect it would probally be in the neighborhood of 40 mph.

[stryder123]

I had a PCX150 before I got my Forza. MPG was pretty much the same at any speed up to 50MPH. After that it dropped off about 25%.

[iceman]

In the winter my average mpg drops by about 10mpg due to colder temp and winter fuel mix - do they change the fuel mix in the US too?

[ONTWOWHEELS]

Always in winter the consumption rises up to every vehicle.

[Oyabun]

In the winter my average mpg drops by about 10mpg due to colder temp and winter fuel mix - do they change the fuel mix in the US too?

Actually extra consumption is due to longer warm up enrichment, and because of the lower air temps.

How it works. Lower temperature air is denser - it contains more oxigen. As the PCX is running closed loop (means the injected fuel is adjusted based on the feedback from the Lambda sensor in the exhaust) the O2 sensor feedback will signal the computer to add extra fuel in order to compensate for the more oxigen in the mix in order to reach the set 14,7:1 Air fuel ratio. So it is rather the engine's own mix than the change in the fuel itself.
Good news it that it generates a tad more power also (that's why all dyno measurements are normalized to a standard 20 degC environment), so enjoy the extra grunt got in exchange the slightly higher consumption.

[Oyabun]

An engine running at 2000 RPMs, and doing 55mph in fifth gear is using as much fuel as the same engine running at 2000 RPMs in sixth at 70 mph.

Only if the fuel input remains constant at 2000rpm regardless of other factors.
But does it...?

I'm no rocket scientist, but I would have thought that if the RPM is constant then the amount of air moving through the engine must be constant - and the fuel/air mix would be most efficient at a give ratio (so no need to change it) - so therefore fuel consumption would be more or less constant.

But in practice I don't think that's the case - not sure why.

Engine RPM is only one factor in calculating fueling. There are a lot more factors, the two most significant are IAT (Intake Air Temperature) and load.
The explanation for IAT see above in my other post.
As for load, just think about the situation where you keep a steady 2000RPM on level ground, vs. on a steep uphill or ascending downhill. It will require completely different throttle and fueling therefore consumption will be significantly different.

External resistances on a moving vehicle are mainly calculated from rolling resistance (road surface; tire pressure and pattern; and bearings) and drag (mainly defined by frontal area, speed, density and shape). The earlier is linear, but the later is scaling exponentially with speed. That's why a tail or headwind can affect fuel economy significantly as drag is not calculated by road speed, but air speed. Other factors modifying engine load are inertia changes (acceleration or deceleration) and changing altitude.

Also internal combustion engines are the most effective at peak torque. That's why usually vehicles are engineered in a way to turn at their max torque RPMs at cruising speed.

So describing a moving vehicle with a mathematical algorithm is a fairly complex exercise, but one does not have to be a rocket scientist to understand the basics.

RPM<>LOAD therefore running at the same rpm in different scenarios does not result in the same fuel economy.

[Oyabun]

My 2015 seems to get the best fuel economy between 30-35 mph.

This---^
Generally speaking the best economy will be had at the fastest speed before invoking air resistance. On a calm day, on level ground, 30-35(mph) is about the best.

Actually depending on the rolling resistance and drag coefficient of the given vehicle the rolling resistance and drag equals around 100km/h or 60Mph. Below this speed rolling resistance is larger, but scaling linearly with speed. Above this speed drag is the higher force and actually scaling exponentially.
Go figure why the selected speed limit around the world for off highway traffic is below this speed, usually around 90 km/h or 45-50Mph.

For those who are more technically inclined and would like to have better explanation:

vehicle forces.jpg (18.47 KiB) Viewed 1330 times

X-axis velocity in meters per second and forces are in Newtons on the Y-axis.
The traction force (dark blue) is an arbitrary value, it does not depend on the vehicle velocity like an ideal CVT scooter transmission keeping RPM and power constant. The rolling resistance (purple line) is a linear function of velocity and the drag (yellow curve) is a quadratic function of velocity. At low speed the rolling resistance exceeds the drag. On this chart at 30 m/s (108km/h) these two functions cross. At higher speeds the drag is the larger resistance force. The sum of the two resistance forces is shown as a light blue curve. At 37 m/s this curve crosses the horizontal traction force line. This is the top speed for this particular value of the engine power (37 m/s = 133 km/h = 83 mph)

[TheMaverick]

As for load, just think about the situation where you keep a steady 2000RPM on level ground, vs. on a steep uphill or ascending downhill. It will require completely different throttle and fueling therefore consumption will be significantly different.

Thanks for all that. Coming from an aviation background most of it is "familiar territory" for me.

The bit I don't get though is ...

- if the ideal fuel/air mix is 14.7:1

and

- if the engine is doing, say, 2000 RPM

then

The air flowing through the engine must be constant regardless of the load because the RPM and displacement haven't changed.

Add to that the ideal fuel/air mix doesn't change depending on the load (or does it?)

So ...

If air through the engine isn't changing (constant RPM) and the fuel/air mix isn't changing - then why is the consumption changing?

[Oyabun]

As for load, just think about the situation where you keep a steady 2000RPM on level ground, vs. on a steep uphill or ascending downhill. It will require completely different throttle and fueling therefore consumption will be significantly different.

Thanks for all that. Coming from an aviation background most of it is "familiar territory" for me.

Welcome. I got my PPL flying a Yak52 and seen a few planes myself too.

The bit I don't get though is ...

- if the ideal fuel/air mix is 14.7:1

Baseline. Lambda 1 (or A/F 14.7:1 weight proportion) is for petrol operated internal combustion engines. Lambda is different for diesel, e85, jetA or others. It is a selected AF mix, mainly to limit the exhaust gases emission. Depending on the design parameters running a mix between 12,4 (at WOT) to 15,2 (lean cruise) could be still ideal.

and

- if the engine is doing, say, 2000 RPM

then

The air flowing through the engine must be constant regardless of the load because the RPM and displacement haven't changed.

Add to that the ideal fuel/air mix doesn't change depending on the load (or does it?)

It does. See above. On the PCX load is calculated based on MAP sensor. In closed loop (outside of startup enrichment) it oscillates around AFR 14.7. Engine operates open loop above approx 75% load around AFR 13.2.

But once again. Fuel consumption is not only determined by it's RPM but real engine load. Power produced is proportional to fuel burned, not only by engine rotation.

[TheMaverick]

Welcome. I got my PPL flying a Yak52 and seen a few planes myself too.

Thanks. I mostly flew single-engine retractables and light twins, but have long since retired from that. I took up radio controlled helicopters, but not sure which was more expensive yet!

Baseline. Lambda 1 (or A/F 14.7:1 weight proportion) is for petrol operated internal combustion engines. Lambda is different for diesel, e85, jetA or others. It is a selected AF mix, mainly to limit the exhaust gases emission. Depending on the design parameters running a mix between 12,4 (at WOT) to 15,2 (lean cruise) could be still ideal.

Interesting, I'm finding my economy to be pretty much halved at WOT when compared to around 50km/hr. Assuming engine RPM is relatively constant then that must me one heck of a AFR variation.

[Oyabun]

Thanks. I mostly flew single-engine retractables and light twins, but have long since retired from that. I took up radio controlled helicopters, but not sure which was more expensive yet!

Great hobby. I kept myself away from gyro so far, still enjoying fixed wing flying. Compared to the upgraded Yak what is approved for unlimited acrobatic flying any of the Pipers and Cessnas I happen to fly nowdays are quite boring already. I'm already not piloting as much I'd prefer, traveling enough on big flying buses while on business anyway.
FPV remote flying has been around my interest for some time now. However having two young kids around keeps me away from my hobbies both financially and timely enough to try to limit myself to the current ones.

Interesting, I'm finding my economy to be pretty much halved at WOT when compared to around 50km/hr. Assuming engine RPM is relatively constant then that must me one heck of a AFR variation.

This is where real life and that "assuming RPM is relatively constant" is making a HUGE difference.
Peak power does not tell much about the operation of an engine, however a dyno chart speaks quite a bit more. Effectively it is a graph of engine efficiency. To explain better, I will use a dyno graph taken from an earlier topic where a stock and performance exhaust had been compared real life on a dyno.

pcx performance.jpg (64.62 KiB) Viewed 1325 times

It shows power curves (wheel Hp seemingly) for the stock and modified engine, but we will take a look only at the stock as for now.
As you can see peak power (and peak efficiency also, as power is not increasing further even by increasing engine RPM) happens at 7650 RPM peaking at roughly 10.5 whp. Anything beyond that point is downwards getting to 6whp @9500 this is down by 37% in efficiency at WOT. Giving the additional ~13% loss in fuel economy from A/F mixture change (the diffrence between 14.7 and 13.2 AFR) might explain why you see a significant drop in fuel economy.

There is however a great tool which is created to represent economy values. It is called a BSFC map. (Brake Specific Fuel Consumption) This supports the above statement, that top fuel efficiency happens near at top maximum torque as this is the point where the engine produces the most power compared to its internal losses.
The following graph is showing a typical street car engine specific fuel consumption at WOT (continuously accelerating at open throttle as an a dyno.

ctrp-1109-01+brake-specific-fuel-consumption.jpg (40.15 KiB) Viewed 1325 times

Plotting every operating point of an engine on a map can give us engine specific parameters, with engine RPM and load on the two axis and the "islands" representing fuel consumption. the map below shows a BSFC map for an another engine, including gearing.

BSFC.GIF (41.98 KiB) Viewed 1325 times

One can see that there is a "sweet spot" of RPM vs load on the engine where specific fuel consumption will be the smallest - in this case 275g/kWh. Moving the operation out of this area either by load (eg. a steep uphill) or RPM (gearing) will result in significantly lower economy.

As an engineer I'm happy to continue this discussion further - but I guess we have lost some of the readers already. :-)