revtothelimit - motorbike forum

Dodgy knees wrote: Wed Jul 14, 2021 7:18 am In slippery, icy conditions, it's a more gradual and constant, less friction slowing to a stop. Engine braking can increase friction and cause momentary loss of control in these conditions.

If you have little or no friction, how will you stop?

'How' you slow (applying the brakes, or lifting your foot off the throttle) won't alter the friction available, it's either there or it isn't.

There is an argument that using the brakes is better than engine braking because it's more controlled- varying the pressure, etc.

Dodgy knees wrote: Wed Jul 14, 2021 7:18 am Also, how does engine keep running if fuel is cut completely

Because the wheels turn the engine when in gear and the clutch is engaged.

The FI switches off fuel, then back on again when revs fall to tickover - ie when the clutch is disengaged or gear in neutral, coasting or stopped.

Yeah that...the engine is 'forced' around by virtue of the fact its connected to the wheels.

Fuel cut is why most EFI vehciles don't snuffle and pop like carbed engines. Generally those overrun cracks on EFI vehicles are programmed in artificially.

As for coasting being better in ice....see alot ice on the roads at the moment?

It's true that the 'regen' effect of only charging the battery when you're slowing down doens't make much difference but it does make a difference. They wouldn't bother going to the effort of doing it if it didn't, would they? 1% here, 2% there, 0.5% over there etc. That's how you make a car 10% more efficient than your competitor's.

I only have a choice of four gears, on a bike with a 7,000 rpm red line that I seldom go near.

Trundling along in a 30 mph limit, I’ll be at 2,000-2,800 rpm in second or third, until I want to accelerate or climb a hill: then I’ll want at least 3,000 rpm.

On the open road, I’ll nearly always want to be above 3,000 rpm, which means I’ll not be in top at any speed under about 45 mph.

A hard burst of acceleration requires 4,500 rpm at least, so it’s not unusual to hold third gear up to 75 mph.

The main effect of having a four speed Triumph rather than the popular five speed T140 gear set, is you use more revs before changing up, to get to a speed suitable for the next higher gear.

I was gonna mention the auld Trumpet.

Supposedly my one has got a close ratio box - that's the family story at least - but things on this bike have changed so many times i'm really not sure. I do know it won't ride happily below ~20mph in 1st and the first time I rode it I actually struggled to tell if I was changing gear or just making clicking noises on the pedal

Not having believable gauges doesn't help!

Close ratios should be fun for pretending you’re racing, but it’s a bit like a five speed with no first gear.

Yeah.

At this point I'm basically resigned to the fact this bike is a twat and I'm just embracing it.

With a close ratio box, you now have no choice but to go fast.

Demannu wrote: Tue Jul 13, 2021 12:11 pm

Horse wrote: Mon Jul 12, 2021 6:02 pm

Demannu wrote: Mon Jul 12, 2021 4:09 pm
Well, the one observer tells me I need to hold the gear longer and not short shift it...........and the other one change up sooner and down later.
Confused.com

Like I say, ask how you should be able to tell. Are you being prepared for a formal test?

More an informal test, taken with all 3 observers, which makes it interesting as I am being told different things by 2 of the observers.
We're going out for a group ride this weekend, so I'll get no3 to have a watch and see what he thinks.
Bike never labours, it's got so much oomph I could leave it in 3rd all day apart from starts.
Imho, there's not much wrong with my riding skills, but I'm quite happy to have someone give constructive criticism if there is a real issue, however if it gets nit-picky ( which is what it appears to me) then they'll be a member short.
My initial assessment had nothing lower than 'good' and mainly 'excellent', so obviously no real issues.

This is IAM I assume? During my 7 or 8 observed rides I only remember one comment about gears, and that was when I screwed up and changed mid-bend. So here are some guesses:
- Your branch hasn't got a very consistent approach to observing, or
- you're not following IPSGA to the letter - gear after speed loss, not before or during - and one of the observers is fussy about that, or
- something else, as per previous comments.

I did say guesses

When I took my IAM test, gears was marked as 'thoughtful'. I have no idea what was meant by that!

Note of observation here. ☝

Since I've stopped using gear 6 in my car, 2.2 diesel my mpg has definitely got better. I'd always been led to believe that higher gears were best, low rpm, but no labouring. Maybe the manufacturers gear change points ain't right.

Could the engine be enjoying the higher rev and engine momentum rather than the lower less rev.

My lads Ford gets a little arrow to tell him to change up and does seem at very low rpm. Might ask him to experiment, but I doubt my request would be taken very seriously.

Too hot for biking.

Dodgy knees wrote: Sat Jul 17, 2021 2:01 pm
Too hot for biking.

Go early,it's the best of both worlds. Little traffic and much cooler temps.

There's a bit of subtlety as to why the manufacturer's gear change points are where they are. In the previous standardised drive cycle (i.e. the predefined journey you drive to get your 'official' mpg) the gears are specified. E.g. you had to accelerate to 20mph and then change into 2nd, then slow down and into 1st then up to 50mph in 4th etc - that's just example figures I'm making up BTW to demonstrate the idea.

The only way you could choose for yourself which gear to be in was to either have an autobox or a system which displays to the driver when to shift in a manual. That's why so many cars have the little arrow display. Naturally they set the arrow system to give the best possible results on the standard drive cycle.

They've changed the test now though (couple of years ago) so that ^^^ doesn't apply as much.

In general though, changing up earlier is more fuel efficient but as with all things exceptions will apply. That's why autos now tend to be more efficient than manuals, 'cause they've got more gears whereas previously manuals used to have more than autos.

Dodgy knees wrote: Sat Jul 17, 2021 2:01 pm Note of observation here. ☝

Since I've stopped using gear 6 in my car, 2.2 diesel my mpg has definitely got better. I'd always been led to believe that higher gears were best, low rpm, but no labouring. Maybe the manufacturers gear change points ain't right.

Could the engine be enjoying the higher rev and engine momentum rather than the lower less rev.

My lads Ford gets a little arrow to tell him to change up and does seem at very low rpm. Might ask him to experiment, but I doubt my request would be taken very seriously.

Too hot for biking.

The little roller skate, I mean car, that I'm using at the moment is a 900cc Fiat 500. Bloody lovely down in the valley. And very economic, too (it says it's a hybrid but I've never noticed the engine not making engine noises!!).

But - going up the mountain is a serious challenge. If I followed the arrow instructions I'd probably end up stationary or going backwards!!! LOL To get it up without it feeling as if it's labouring in any gear you have to hit about 4500rpm before changing up a gear - which sounds horrible but if you believe the 'how economically am I driving' thingy, it seem to be ok.

Absolutely no chance of a short quick overtake between hairpins though There's only a couple that allow it in the roller skate - in a 'normal' vehicle there are plenty of places!! Even when I've tried to rant it through the gears, it won't do a decent overtake

As we have moved onto cars, our little petrol fiesta averages 54.3 mpg.
We don't live on the vast plains so we get a fair.bit of up and down. The readout is on ATM fuel consumption, so I can see if I'm in the right gear.
As for the bike, we've got a 100 mile run to the coast, so hopefully get some clarity as to what I'm doing.

The Octavia keeps telling me to change up earlier than I want to. The Tracer has an 'Eco' message that seems to come on more or less whatever I'm doing. I prefer that!

Mr. Dazzle wrote: Wed Jul 14, 2021 6:53 pm It's true that the 'regen' effect of only charging the battery when you're slowing down doens't make much difference but it does make a difference. They wouldn't bother going to the effort of doing it if it didn't, would they? 1% here, 2% there, 0.5% over there etc. That's how you make a car 10% more efficient than your competitor's.

Charged the battery from flat to full on an Audi hybrid, descending from high up in the Sierra Nevada last year. The battery got us maybe a third of the way up. So that's a pretty effective rate of recovery.

The Spin Doctor wrote: Sat Jul 17, 2021 11:45 pm

Mr. Dazzle wrote: Wed Jul 14, 2021 6:53 pm It's true that the 'regen' effect of only charging the battery when you're slowing down doens't make much difference but it does make a difference. They wouldn't bother going to the effort of doing it if it didn't, would they? 1% here, 2% there, 0.5% over there etc. That's how you make a car 10% more efficient than your competitor's.

Charged the battery from flat to full on an Audi hybrid, descending from high up in the Sierra Nevada last year. The battery got us maybe a third of the way up. So that's a pretty effective rate of recovery.

Can't remember whether I read it on here, or elsewhere, there's a quarry somewhere that has electric trucks hauling rock down off a mountain. They regen more power going down than is used going up.

The Spin Doctor wrote: Sat Jul 17, 2021 11:45 pm

Mr. Dazzle wrote: Wed Jul 14, 2021 6:53 pm It's true that the 'regen' effect of only charging the battery when you're slowing down doens't make much difference but it does make a difference. They wouldn't bother going to the effort of doing it if it didn't, would they? 1% here, 2% there, 0.5% over there etc. That's how you make a car 10% more efficient than your competitor's.

Charged the battery from flat to full on an Audi hybrid, descending from high up in the Sierra Nevada last year. The battery got us maybe a third of the way up. So that's a pretty effective rate of recovery.

As a hybrid it will also have a much beefier regen system. The electric motor is able to sink much more power out fo the car and put it into the batteries.

In my car the only regen aspect is the regular alternator. The reg/rec is smart, so it only excites the alternator coils to charge the battery when you're slowing down or if the battery is below a certain charge. The rest of the time it just produces enough juice to keep the electricity balance at zero - I.e. neither charging nor discharging the battery.

I can't imagine it provides very much braking power at all, but as I said BMW have obviously done the maths and deemed it worthwhile.

Atm, I guess you can only 'force feed' a battery with charge so much before things go very wrong. It's always gonna take longer than a petrol stop. That's why I reckon the home charge for commuting vehicles should be first agenda.

I could be wrong.

Yeah that's right, the maximum charge/discharge power is limited. Bigger batteries can cope with more, which is why the longer range vehicles are also faster.