Juddian:
eddie snax:
Juddian:
..
the vehicle was supplied with an exhaust brake for a reason, it isn’t up to much they seldom are
Get a Volvo they allways are
Is the current Volvo an exhaust brake then?, i thought they were rather too good for a simple flap in the exahust pipe.
Haven’t driven a current one but the older ones had a VEB or Volvo Engine Brake, like a Merc KD.
Carryfast:
Saaamon:
Carryfast:
Saaamon:
Carryfast:
Saaamon:
To make good use of the engine brake you have to go down the gears earlier than say in a car so the only way you can match the road and engine speed is to rev in between gears which you don’t need to do nowadays (if you use the clutch)… But of course you shouldn’t be rough with it by dropping the clutch causing the revs to fly round suddenly, just slowly out with the clutch…You could consider just backing off the throttle earlier and just letting the speed drop off on its own, I personally wouldnt keep using high revs unless I was very heavy. The only time I tend to let the revs go into the blue is if im on a long downhill stretch.
So you’re saying that you let the engine idle during a downshift then in addition to the extra stress which you’re putting on the synchros by doing it you then also have to let the clutch in slowly to avoid overstressing the rest of the driveline as a whole.In which case you’re taking mileage off the clutch face because the only way that you can let it in slowly in that case is by using clutch slippage to avoid the transmission shock loading of using the clutch properly.Which as we all know means that it’s either in or it’s out or it’s slipping with slippage needing to be kept to an absolute minimum
All of which is why the correct way to drive is to match road and engine speeds during downshifts.
No he’s not letting the engine run at idle, its one smooth movement… Theres absolutely no way you can avoid clutch slip when changing gear (if you use the clutch) its what their designed to do, that’s why the pressure plate or now the flywheel has anti judder springs on them. In motorsport they don’t use anti judder springs and that’s why their either on or off but for full road use you need slip if you want a comfortable drive.
If you don’t avoid clutch slip during gearshifts you’ll simply just wear the thing out considering the amount of slip that every gearshift would add up to over the course of a year assuming that you’re not matching road and engine speeds in order to create that situation whereby,as I’ve said,it’s either in or it’s out with no slippage whatsoever.As I’ve said it’s that matching of engine and road speed which is supposed to not only provide the comfortable drive but it also prevents excessive stress on the synchros and through the driveline.Clutch slippage just creates heat and wears out the clutch and the flywheel face which effectively means throwing money away for nothing.
Can you explain the method you use to pull away then if you don’t slip the clutch?
There’s a big difference between the amount of clutch slip involved in starting from standstill using a low gear and as low engine speed as possible compared to how much mis matched engine and road speeds would cause over the course of every gear change if you’re using clutch slippage to compensate for the difference.
But were not mis matching engine speeds and the revs don’t drop down to idle when the clutch is depressed and as ive already stated, from my experience with a scania the fly by wire throttle doesn’t react quick enough… If you were ment to blip in between gear changes they wouldnt have made synchro box’s because for the blip to be worthwhile the gear will slot straight in without the clutch and even on a synchro box it will do that, the very fact your ment to use the clutch on these kind of box’s proves that you don’t need to match the engine speed by way of the throttle. Of course im not suggesting you go missing out loads of gears and let the revs fly round but smoothly working your way down missing out a couple along the way etc.
coiler:
Sidevalve:
Saaamon:
Carryfast:
Saaamon:
tootman318:
On any manual truck you should always match your engine revs to the gear selected, Basics really
Sorry what year is it again? Think you’ll find that you no longer need to do that on a modern synchromesh gearbox, reving in between gear changes is a waste of fuel… Do you even drive a manual lorry?
There’s nothing ‘modern’ about synchro boxes they’ve been available for years.The fact is the more of a mis match between road and engine speed the more stress the synchros are put under.That’s in addition to the extra stress that’s put through the drivetrain as a whole assuming you just force the downshift through with the engine at idle and then just let the clutch back in.
Im well aware that they’ve been around for a while now… So are you trying to say we should be reving in between downshifts then?
Well the Volvo i-shift does and that’s supposed to be a ■■■■ sight smarter than us drivers.
Go figure.
The Volvo I shift does not have synchro cones that why it has to rev between downshifts to match engine speed to gearbox speed otherwise the gears will crunch. That’s why it is lighter than a manual box.
Manual gearboxes are synchromesh so you don’t need to Match engine speed to gearbox.Another thing to think of when engine or exhaust braking is that your brake lights do not come on so there is no warning to drivers behind you that you are slowing.
I don’t think it will have, it’s a computer controlled normal malnual gear box, like you will find in a manual truck, the only reason why it revs between gears is because it doesn’t use the clutch, just like you can change gear in a manual gear box with out the clutch, it only uses the clutch when setting off and stopping.
Saaamon:
Carryfast:
Saaamon:
Carryfast:
Saaamon:
Carryfast:
Saaamon:
To make good use of the engine brake you have to go down the gears earlier than say in a car so the only way you can match the road and engine speed is to rev in between gears which you don’t need to do nowadays (if you use the clutch)… But of course you shouldn’t be rough with it by dropping the clutch causing the revs to fly round suddenly, just slowly out with the clutch…You could consider just backing off the throttle earlier and just letting the speed drop off on its own, I personally wouldnt keep using high revs unless I was very heavy. The only time I tend to let the revs go into the blue is if im on a long downhill stretch.
So you’re saying that you let the engine idle during a downshift then in addition to the extra stress which you’re putting on the synchros by doing it you then also have to let the clutch in slowly to avoid overstressing the rest of the driveline as a whole.In which case you’re taking mileage off the clutch face because the only way that you can let it in slowly in that case is by using clutch slippage to avoid the transmission shock loading of using the clutch properly.Which as we all know means that it’s either in or it’s out or it’s slipping with slippage needing to be kept to an absolute minimum
No he’s not letting the engine run at idle, its one smooth movement… Theres absolutely no way you can avoid clutch slip when changing gear (if you use the clutch) its what their designed to do, that’s why the pressure plate or now the flywheel has anti judder springs on them. In motorsport they don’t use anti judder springs and that’s why their either on or off but for full road use you need slip if you want a comfortable drive.
If you don’t avoid clutch slip during gearshifts you’ll simply just wear the thing out considering the amount of slip that every gearshift would add up to over the course of a year assuming that you’re not matching road and engine speeds in order to create that situation whereby,as I’ve said,it’s either in or it’s out with no slippage whatsoever.As I’ve said it’s that matching of engine and road speed which is supposed to not only provide the comfortable drive but it also prevents excessive stress on the synchros and through the driveline.Clutch slippage just creates heat and wears out the clutch and the flywheel face which effectively means throwing money away for nothing.
Can you explain the method you use to pull away then if you don’t slip the clutch?
There’s a big difference between the amount of clutch slip involved in starting from standstill using a low gear and as low engine speed as possible compared to how much mis matched engine and road speeds would cause over the course of every gear change if you’re using clutch slippage to compensate for the difference.
But were not mis matching engine speeds and the revs don’t drop down to idle when the clutch is depressed and as ive already stated, from my experience with a scania the fly by wire throttle doesn’t react quick enough… If you were ment to blip in between gear changes they wouldnt have made synchro box’s because for the blip to be worthwhile the gear will slot straight in without the clutch and even on a synchro box it will do that, the very fact your ment to use the clutch on these kind of box’s proves that you don’t need to match the engine speed by way of the throttle. Of course im not suggesting you go missing out loads of gears and let the revs fly round but smoothly working your way down missing out a couple along the way etc.
Getting boooooooooooring now FFS. Nite Nite
Scanner:
Juddian:
eddie snax:
Juddian:
..
the vehicle was supplied with an exhaust brake for a reason, it isn’t up to much they seldom are
Get a Volvo they allways are
Is the current Volvo an exhaust brake then?, i thought they were rather too good for a simple flap in the exahust pipe.
Haven’t driven a current one but the older ones had a VEB or Volvo Engine Brake, like a Merc KD.
Yeah i thought so, Eddie is comparing apples with oranges.
Bloody FM left by previous driver on full ■■■■■■ (unnoticed by me) nearly caught me out one morning, left the depot empty trailer first roundabout on the estate held black ice, sodding auto box drops about 3 gears just as i entered the roundabout and the engine brake cut in on full power locking the drive axle straight up…brown trouser moment… 
If you want to look after the clutch, blip the throttle on downchanges to try and match engagement speed, but if you don’t really give a ■■■■ then make it have it.
All auto box’s blip the throttle to save on clutch wear and in the right hands will easily exceed a million kms on the first clutch, unfortunately in the wrong hands and regularly held stationary on hills using the accelerator and no brakes their time is limited, but to some thats fair game it being deliberate abuse or just plain ignorance of the damage they’re causing that is equivalent to riding the clutch 
And on any decent truck the engine brake activates the stop lights with an inertia switch, and the exhaust/engine brake is over ridden by the ABS when it detects any wheels starting to turn slower than the average rotating speed of the rest. HTH.
coiler:
Another thing to think of when engine or exhaust braking is that your brake lights do not come on so there is no warning to drivers behind you that you are slowing.
Using the exhaust brake on a newer Scania brings the brake lights on.
Juddian:
Scanner:
Juddian:
eddie snax:
Juddian:
..
the vehicle was supplied with an exhaust brake for a reason, it isn’t up to much they seldom are
Get a Volvo they allways are
Is the current Volvo an exhaust brake then?, i thought they were rather too good for a simple flap in the exahust pipe.
Haven’t driven a current one but the older ones had a VEB or Volvo Engine Brake, like a Merc KD.
Yeah i thought so, Eddie is comparing apples with oranges.
:
I’ll give you that one. it is a 3 stage engine brake standard exhaust brakes are all noise and no action
The comfort shift manual box found in MANs speed matches
And I don’t see how saaamon can say he’s not mismatching speeds, a different ratio will give a different engine speed for a given road speed, if you don’t rev it on a downshift, then you’re mismatching.
Big Joe:
If you want to look after the clutch, blip the throttle on downchanges to try and match engagement speed, but if you don’t really give a [zb] then make it have it.
Out of interest, how does blipping the throttle “look after” the clutch?
Big Joe:
All auto box’s blip the throttle to save on clutch wear and in the right hands will easily exceed a million kms on the first clutch,
As has been said already, auto boxes blip the throttle because they are automated “crash” boxes…there is no synchromesh to match the gear speeds so the ecu has to do it in the same way the driver had to when crash boxes were the norm.
It’s nothing to do with the clutch.
@javiatrix If it is a brand new truck it should have been supplied with an operators manual 
You would be well advised to read that because the maker of the truck is probably the only one who will be able to explain ‘clearly’ what you want to know 
Regards
Dave Penn;
The blue band on the rev counter is there to indicate the optimum RPM for engine braking!
Blipping the throttle on a synchromesh gearbox will wear out the synchro rings faster than not blipping the throttle. If it’s synchromesh DO NOT BLIP!
Automated Manual Transmissions, such as i-shift are constant mesh, this is why the computer blips the throttle on downshifts, or even applies the engine brake to get a fast upshift, it has to match engine and transmission speeds as there are no synchro rings.
Nothing wrong with what the OP is doing, just make sure it’s done smoothly (by being gentle with clutch engagement) and it will be fine.
Javiatrix:
‘… it’s a 6 speed … drop to 5th gear … drop it to 4th…’
I’d advocate to get ‘block changing’, ie, without the sequencial down-shifts by allowing greater decelleration on the retarder/engine brake from the original higher gear 
That all depends on the gear spacing, the jump from 6th to 4th could be 1000rpm and that will not be very mechanically sympathetic…
I drive an Actros. Mercedes say you can replace 85% of the foot brake use with the engine brake. Optimum braking power is between 1500 and 2300rpm. Each gear drop increases the revs by 400rpm so they advise getting the revs to 2300rpm for maximum effect then waiting till it drops to 1500 before doing a double downshift to get it back to 2300 and maximum effect again.
Apparently the engine is designed for this and causes it no harm. It does make a hell of a lot of noise and gets you thinking, would I want my car to sound like this, the answer being no obviously. But, Mercedes say it’s OK and some of our units have 2 millions kms on the clock so it can’t be that bad.
newmercman:
The blue band on the rev counter is there to indicate the optimum RPM for engine braking!Blipping the throttle on a synchromesh gearbox will wear out the synchro rings faster than not blipping the throttle. If it’s synchromesh DO NOT BLIP!
Automated Manual Transmissions, such as i-shift are constant mesh, this is why the computer blips the throttle on downshifts, or even applies the engine brake to get a fast upshift, it has to match engine and transmission speeds as there are no synchro rings.
Nothing wrong with what the OP is doing, just make sure it’s done smoothly (by being gentle with clutch engagement) and it will be fine.
Thank god someone’s posted some sense it was getting painful. 
I think people are misunderstanding when manufacturers say their lorries have automated manual transmissions what they’re really saying is it’s not a torque converter type automatic like cars.
I would just add
Blipping the throttle may be beneficial sometimes if you’re given an old shed.
The brake light situation on exhaust/engine brake depends on the make and someone mentioned the risk of locking up with them with a rigid there is exceptionally low odds of coming unstuck like this and I think the risk is often greatly overstated in an artic.
As far as the OP’s concerned, I agree, leave the exhaust brake switched on so it activates when you brake normally. If the changes feel smooth and nothing’s screaming you’re probably doing fine. Consider using the exhaust brake on its own just to start taking speed off before applying the service brakes.
newmercman:
The blue band on the rev counter is there to indicate the optimum RPM for engine braking!Blipping the throttle on a synchromesh gearbox will wear out the synchro rings faster than not blipping the throttle. If it’s synchromesh DO NOT BLIP!
It’s simple mechanical physics that the larger the mismatch between engine speed and road speed the harder the synchros will need to work especially in the case of drivers following the idea of block changes. In addition to which the only way that you’ll be able to let the clutch back in,if you’ve got an engine that’s turning over slower than the engine speed required for the lower gear,is by slipping the clutch unless you want to apply a massive shock loading through the driveline.
Terry T:
I drive an Actros. Mercedes say you can replace 85% of the foot brake use with the engine brake. Optimum braking power is between 1500 and 2300rpm. Each gear drop increases the revs by 400rpm so they advise getting the revs to 2300rpm for maximum effect then waiting till it drops to 1500 before doing a double downshift to get it back to 2300 and maximum effect again.Apparently the engine is designed for this and causes it no harm. It does make a hell of a lot of noise and gets you thinking, would I want my car to sound like this, the answer being no obviously. But, Mercedes say it’s OK and some of our units have 2 millions kms on the clock so it can’t be that bad.
^ This.
Sequential downshifts keeping the engine speed as high as possible is the correct way to make an exhaust brake work properly.
How is dropping two gears sequential ffs
I know what carryfast is saying. Obviously with a crash box you cant make a change if the road speed and engine speed dont match and with the i shift type boxes the electronics wont let it or the driver if in manual select a gear that it cant match the speeds too.
How ever you can force a sychro box to do it but the clutch will take a hammering but anyone with half a brain should realise the have dropped a clanger.