Low Rev Driving

[rjbetty]

Ok I'll try not to beat around the bush for once:

I've got a Silver Vauxhall Astra X Reg (2000). I wanna save fuel so I go round driving at low revs (like 1500-2000rpm). Trouble is, the car has been jolting at low revs recently, and now tonight on the way to Xscape at Milton Keynes the engine light has come on. It stayed on the whole way home too.

This looks like a problem with the ignition coil pack to me - I know that cos I've blown 2 before!

I'm just wondering does anyone know these things, cos I don't know very much... Do you think there is something about the way I'm driving that is causing my coil pack/spark plugs to overheat? Cos I read in the handbook years ago that 2000-2500rpm was recommended, but I do 1500-2000...

[Gregor-y]

I'd see what the code is and maybe get a compression test. A friend of mine that works for BMW claims some cars he deals with have trouble with water in the cylinders because the motors aren't revved enough to cook it off.

[Mark]

You might have also knackered the DMF (dual mass flywheel) too?

Simply keeping low revs isn't the full story. Especially if the engine is having to inject vast qualities of fuel to keep the engine turning under the load you are putting it.

I've been hypermiling for many months and the best way I've found by far to save fuel is to drive slower.

[driveace]

You can save on fuel by using the BUS,or by buying a car with a better MPG,and smaller engine.My Fiesta 1.8 diesel will do 60MPG even on driving tuition so consider a diesel car.

[rjbetty]

Thanks for the responses guys.

I actually save most of my fuel by using my bike for all short journeys - and even for journeys up to 20miles when I travel by myself. :)

But I do feel that the ignition coil pack has overheated again - the third time this has happened with me in a Vauxhall Astra. The symptoms are the jolting at low revs, especially in low gears, and that's exactly the symptoms I had before. But it always seems to be at high speed on the motorway/dual carriageway that the engine light has come on on the dash - and both times before it was on the M4 that the coil pack melted and broke down altogether...

[driveace]

|Get it plugged up to the computor,see what fault codes it comes up with ,other wise you are looking for a needle in a haystack !

[Mark]

You can save on fuel by using the BUS,or by buying a car with a better MPG,and smaller engine.My Fiesta 1.8 diesel will do 60MPG even on driving tuition so consider a diesel car.

Taking the bus will often cost more than the price of fuel. So would be pointless.

[rjbetty]

I think you guys are both right. Sadly I'm disappointed that with the Vauxhall Astra I can drive in 5th gear at 30mph as long as I have good momentum. The trouble is that is the highest gear, so it's the same one you use for 70mph!! Oh what a waste of fuel! Yeah I actually wanted an LPG car.

60mpg - Wow!
Yeah the bus is expensive! But the trains were a shock. Having not used one for years, I found out a single ticket from Reading to Port Talbot is £55, and £110 return. I actually thought it was a WEEKLY ticket! :eek:

[rjbetty]

|Get it plugged up to the computor,see what fault codes it comes up with ,other wise you are looking for a needle in a haystack !

Oh I think I saw someone do that once. How do you get one of those computers...?

[Mark]

I try to save as much fuel as possible on my 35 mile drive to work. I usually get low 70's MPG. But I've been known to get over 80MPG on a good run

1.6TDCi Fiesta.

[Mark]

Oh I think I saw someone do that once. How do you get one of those computers...?

The garage you take it too will have one. But often there is a car startup sequence which will display the current fault codes.

[rjbetty]

Thanks guys. Do any of you think that using low revs (not low enough to stall) can cause problems with the coil pack (making it overheat)?
I suspect it may be using too few revs that has done something to them, especially cos two blew in succession in my old Astra, and now this one's going in my recently acquired new Astra (same year X Reg).

Aw I think I might be what is known in F1 as a Car Breaker! What team would want me now...? :(

[D-Type]

i don't think driving at 1500 to 2000rpm is the most fuel efficient - I would have expeted 2500 to 3000 rpm. But more important is to be in the right gear. Sometimes an engine is more efficient revving freely than labouring in too high agear.

This doesn't cure your current engine woes, I suspect an obscure electrical fault possibly even that old perrenial - poor earthimg.

[rjbetty]

i don't think driving at 1500 to 2000rpm is the most fuel efficient - I would have expeted 2500 to 3000 rpm. But more important is to be in the right gear. Sometimes an engine is more efficient revving freely than labouring in too high agear.

This doesn't cure your current engine woes, I suspect an obscure electrical fault possibly even that old perrenial - poor earthimg.

Thanks, that's helpful. :)

Ok I'm gonna try that kind of rev range on my next tank of fuel, especially cos I remember the manual years ago recommending 2500ish. I just assumed that low revs automatically means better fuel economy and engine life... I wanna drive with 2500 instead of 1500rpm and see how many miles I get till the low fuel light comes on. I'm getting about 400miles on a 50Litre full tank atm at 1500, I think that's 36mpg (uk gallons) - not happy with that...

Nice sig btw, I can think of a few people I know who could do with reading that. Come to think of it, I could do with it too.

[airshifter]

High revs and lower loads do produce reasonable strain on the ignition system, but not excessive. The lower revs will produce a situation that makes you notice any engine missing though, and that might be what is happening. As revs decrease engine misfires often seem more pronounced than if they happen at higher revs. Some cars will seem like they miss terribly at idle, but once driving you would hardly notice the problem exists.

If you have been burning up that many coil packs it seems to be a bigger issue. These days some of the coil packs even have cooling fins on them, so I'm assuming heat is an issue on many of them.

[donKey jote]

i don't think driving at 1500 to 2000rpm is the most fuel efficient - I would have expeted 2500 to 3000 rpm. But more important is to be in the right gear. Sometimes an engine is more efficient revving freely than labouring in too high agear.
I read somewhere that low steady revs on the motorway was not too good for the engine (something to do with lubrication) and I also know for a fact that long idle times can do your cat in, but until I can find a LPG system for my engine, I'll keep idling along (using ACC) at just under 2000rpm on my commute. This way I get ~33mpg on my Smax automatic 2liter "ECO"tec while the average user only gets ~23mpg, according to spritmonitor.de.
For city driving, just under 2000rpm means 58kmh and also gives me the best consumption. If I switch to manual mode 6th gear, the revs and the consumption go down further (to ~1500+ and by ~.5l/100km), but it does seem to struggle a bit :)

[rjbetty]

Thanks Donkey. Everyone's posts are helping me; this is an educational experience. :)

What did you mean you can get an LPG system for your engine? Can you do that, actually convert a car from petrol to LPG?!!

Wish I had a 6th gear...

[Mark]

Thanks Donkey. Everyone's posts are helping me; this is an educational experience. :)

What did you mean you can get an LPG system for your engine? Can you do that, actually convert a car from petrol to LPG?!!

Wish I had a 6th gear...

Erm, yeah. How else would you do it? You can't buy LPG cars new.

[donKey jote]

What did you mean you can get an LPG system for your engine? Can you do that, actually convert a car from petrol to LPG?!!

I used to drive a Scenic 2.0 16v, which I had converted to LPG for ~2500€. 50l gas tank instead of a spare wheel and 50% fuel costs. :D
After 10 years I got an Smax 2.0 EcoBoost (turbo direct injection), and hoped to do the same. Turns out Prins have a system for the 1.6 EcoBoost but not yet for the 2.0 :mad:

[schmenke]

Taking the bus will often cost more than the price of fuel. So would be pointless.

Yep.
A year ago I was working in the extreme south end of the city. I live in the extreme north end so I had a cross-city commute every day at just over 70kms round trip.
Taking the bus would take about 75 minutes to commute to work and cost $94.00 for a monthly pass.
Driving my Korean POS took under 30 minutes and averaged $80.00 a month on fuel :mark: .

[schmenke]

Oh I think I saw someone do that once. How do you get one of those computers...?

Around here you can purchase one at any automotive shop (and even some hardware stores) for about $40.00 :mark:
I'm not sure about European cars, but since 1996(?) all American and Japanese built vehicles have standardized codes and interface ports, so the readers are universal (can be used in any car).

[schmenke]

...This doesn't cure your current engine woes, I suspect an obscure electrical fault possibly even that old perrenial - poor earthimg.

I'm no mechanic, but this sounds likely. If your coils are overheating, assuming your voltage output is o.k., they are carrying excessive current. Proper grounding should alleviate this.

[Mark]

Around here you can purchase one at any automotive shop (and even some hardware stores) for about $40.00 :mark:
I'm not sure about European cars, but since 1996(?) all American and Japanese built vehicles have standardized codes and interface ports, so the readers are universal (can be used in any car).


AFAIK European cars use the same standard called ODB codes.

[Gregor-y]

In the US a lot of parts stores will offer a free ODBII scan. You may want to see if a local Halfords or some similar store does the same.