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Old 6th October 2010, 07:44   #21
Roverron
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Originally Posted by COLVERT View Post
Thanks for your reply Ron. The first paragraph I find interesting. I guess the ECU must compensate for variable pressure up to around 3,000 rpm by holding the injectors open that fraction longer:
The injector opening time is just what it needs to be to either maintain a constant speed or provide whatever demand the driver is requesting via the accelerator. So the ecu doesn't compensate as such, its just programmed to proved a given quantity of fuel and as it knows the pressure, can work out the duration.

Hence tuning boxes work by increasing the pressure, though as the ecu isn't aware of this, it doesn't reduce the duration, so more fuel is injected and thus more torque produced.

The reason the fuel pressure is not constant is because the HP pump consumes a significant amount of power, so the pressure is only as high as it needs to be to provide the torque and meet emissions tests.

Returning to the subject of injector cleaning by means of an Italian Tune-up, there's many a car passed its MOT after being given a good blast up the road with some injector cleaner in the fuel. Thata's not an old wives' 'tale, its a fact.
I believe that diesels that are always driven gently will suffer from clogged injectors, cats, exhaust, even egr valve much more so than cars driven hard.
I recommend everyone give their diesel a good thrashing once a month to clear it out. You are not doing your engine any favours by being a gentle driver!

Ron
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Old 7th October 2010, 07:07   #22
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Hi Ron,

I read somewhere on the forum that you designed the Synergy2, so I reckon your are qualified in making a suggestion about how hard to drive a diesel engine. As one of the 'gentle drivers' I admit to feeling nervous about pushing the car hard. The car has been running smoothly now for the past 2 weeks. Given that there may well be drivers like myself out on the open road, could it be equally prudent to just floor the accelerator whilst the engine is on and stationary with injector cleaner in the tank, or not?

Are we looking at red-lining the tach and if so how often? or would 3K / 4K at least once a month be adequate?

What would you suggest? I am interested in your thoughts.

Thanks

Phil
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Old 7th October 2010, 08:58   #23
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Hi Ron,

I read somewhere on the forum that you designed the Synergy2, so I reckon your are qualified in making a suggestion about how hard to drive a diesel engine. As one of the 'gentle drivers' I admit to feeling nervous about pushing the car hard. The car has been running smoothly now for the past 2 weeks. Given that there may well be drivers like myself out on the open road, could it be equally prudent to just floor the accelerator whilst the engine is on and stationary with injector cleaner in the tank, or not?

Are we looking at red-lining the tach and if so how often? or would 3K / 4K at least once a month be adequate?

What would you suggest? I am interested in your thoughts.

Thanks

Phil
Its pointless revving it in neutral as the load and therefore fuel flow is little more than when idling.

Of all engines, the BMW one is very strong and reliable and as BMW produce performance cars, intended to be used to its full ability.
With decent performance and our crowded, speed trap infested roads, you cannot really thrash the engine very hard for long anyway.

Certainly take it 4000rpm, in 2nd and 3rd even on part throttle now and again and definitely use full throttle quite regularly even if only to 3000-3500rpm.

Ignore the red line - few diesels make significant power above 4K rpm, its a safe rpm limit and not as some owners think, where maximum power is!
Best performance is achieved by changing up so the revs drop to about 2000-2200rpm. This means changing at well below 4000rpm. If you change up later, you will miss peak torque which is at those sort of revs. Its hard to get some 'sporty' drivers to grasp this though not the more gentle ones like yourself.


Ron
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Old 7th October 2010, 21:30   #24
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Thanks Ron

All noted!

I drive an auto and the only way I can get the revs up quick is to do the 'kickdown' I have not yet tried it with auto off, but will do so and see what happens. Unless it is advisable not to.

I have had two MG tf's with the paddle gears 6 of them on the steering wheel and in those instances it was quite easy to redline and change down for acceleration in getting up the speed for overtaking. If I remember how I did that, then I could use the same technique with the diesel...I think. But I will not know until I try this out over the weekend. In those days I was not the gentle driver I am today and only had one HGF go. It was replaced in the days of the Rover no quibble warranty. Happy days.

Thanks

Phil
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Old 7th October 2010, 23:06   #25
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You can still use the gear lever even on an automatic. Use it the same way you do on a manual, but without moving yer left foot!

As Ron sez, give the car some welly, and when the car stops pulling so well, move the gear lever up one = change up...

At 70 mph in 3rd gear my car does 4000 ish revs, so you don't have to break the speed limit if that's your worry ..

Problem with doing this is -- After a while you find yourself muttering "c'mon c'mon c'mon " under yer breath... heh heh..
...
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Old 8th October 2010, 23:29   #26
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Thanks James or should I say "The Stig" as you coach me thro the gears.

Tonight I ran into heavy traffic which ever way I went. After 1 hour of crawling at a snails pace, the engine overheated. I pulled off into a car park at Ally Pally, waited an hour - did a coolant top up and there were no more problems.

I have learned that this particular car does not like crawling along any longer than about 30 - 45 mins before the red light comes on.

I am still going to go for a burn over the w/e..one must push up the revs as I have now learned that it really is important to drive the car as James and Ron have talked about - ultimately to keep the M47 healthy.

Phil
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Old 10th October 2010, 18:06   #27
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Thanks James or should I say "The Stig" as you coach me thro the gears.

Tonight I ran into heavy traffic which ever way I went. After 1 hour of crawling at a snails pace, the engine overheated. I pulled off into a car park at Ally Pally, waited an hour - did a coolant top up and there were no more problems.

I have learned that this particular car does not like crawling along any longer than about 30 - 45 mins before the red light comes on.

I am still going to go for a burn over the w/e..one must push up the revs as I have now learned that it really is important to drive the car as James and Ron have talked about - ultimately to keep the M47 healthy.

Phil
As it is extremely rare for a Diesel R75 to overheat it sounds as though you have a problem with your cooling fan. A regular problem with the R75 and well documented on the forum.



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Old 10th October 2010, 18:19   #28
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RoverRon. Sorry to be a pest but my enquiring mind keeps driving me on .Lol.
If I drive my car hard I get around 40mpg. If I drive it gently I get around 50 mpg.
I can use a tankful of fuel, with injector cleaner in it, in either 4 days or 5 days depending on how hard I drive it.
Now does this mean that, at the end of a week, my injectors will be cleaner after driving it hard than they would be if I drive it gently ????
( Having had the same amount of fuel and cleaner in both cases pass through the injectors. )


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Old 10th October 2010, 18:52   #29
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Me again Ron. ( The pest !! )
If you check the emissions and soot particles ejected from a vehicle running efficiently at 60 mph on the flat versus another identical vehicle maintaining 60 mph up a 1 in 10 slope does not the vehicle on the slope pass much more soot through EGR valve back into the engine ??? Put a greater coating of black inside the exhaust pipe and soot particles into the engine oil ??? It's this muck plus unburnt fuel that clogs the EGR valve and blocks the cat and reduces its efficiency is it not ???
Don't think it does your lungs much good either when the person in front of you gives his car the boot and you disappear in a giant black cloud of whatever is not being burnt. Lol.
Told you I was "a pest", didn't I ???
It's just that I can't see at what point of booting or thrashing your car everything becomes cleaner !!!!! Especially the poor bloke behind you who now looks like a Panda.


PMSL. Sorry Ron, I really am.



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Last edited by COLVERT; 10th October 2010 at 18:53.. Reason: Spelling
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Old 30th July 2013, 16:22   #30
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Hi,
I have a well similar problem as mick1960.
Rover 75 cdti, saloon, automatic, 2004, 80.000 mls.
The engine is knocking, the idle is rough. The rev is bouncing up and down between 600-750.
When I put the car in D or R the whole car is shaking for a second or two and the knocking noise comes. If I put the it back to P or N the knocking disappears, but the rough idle is still there.
When I`m driving the knocking disappears above 1800-2000 rev in 1st and 2nd gear and it disappears in 3 4 5 because the speed is a bit higher even the rev is low.
When I have to brake, just before I stop -the car goes very slowly- the rev drops down to 400-500 for a second and the car is shaking but the rev goes back straight to the 600-750 rough idle.
This is always happening when the engine is hot. It is not happening with cold engine.
The performance of the car is good. No smoke, no power loss, kickdown is good.
I think Ron is right but I would located the problem first rather than start to spending my fortune on the car.
Any help appreciated.
Thank you
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