Driving for economy - which gears at what speeds

[CC2005]

Definitely a manual


Admittedly, I haven't cleaned the MAF, nor have I checked my intake manifold as I didn't have my EGR blocked until I'd done almost 30,000km.

EGR mod at 30,000km, I don't think you'll have anything to worry about at all . Mine at 25,XXXkm is basically clean as far as I can see. And the MAF is spotless. Being an auto it loves having a drink more than me on a Friday night.

Cheers

[Redtag]

EGR mod at 30,000km, I don't think you'll have anything to worry about at all . Mine at 25,XXXkm is basically clean as far as I can see. And the MAF is spotless. Being an auto it loves having a drink more than me on a Friday night.

Cheers

Hi there,
I did my EGR mod at 95,000km, so I'm not expecting my engine to be that clean! It is feasible (easy?) to clean the bits that normally coke-up?
redtag

[amec]

I've not done it by by what I've read it isn't hard.

Inlet manifold off and have it chemically cleaned.

[Redtag]

Hi folks
I took my Challenger (auto PB) to Lake Eucumbene from Adelaide for a few days fishing last week. Lightly loaded with just the wife and I and not much luggage (not camping!).
This was after a software update for the autotrans. It SEEMED like fuel consumption was slightly better around town after the software upgrade so I was interested to see what differences there might be on long flat roads at cruising speed and also getting up to Kiandra from Wagga.
The road around Hay-Balranald was perfect for a flat road test so I set the cruise control for 110kph (based on satnav, not the speedo, which showed about 118 at that speed). I chose top gear, re-set the fuel consumption gauge and recorded the l/100km reading after about 20km. I repeated that twice and then averaged the 3 readings. That returned an average of 10l/100km (in fact each of the 3 readings was 10l/100km). Then I tried using 4th gear at the same speed, average for 3 replicates was 10.4l/100km. Made sense, the engine speed is higher in 4th than 5th. Both gears remained locked up during the test.
Then I tried the experiment at 102kph, again using 4th and 5th gear and carried out 4 replicates in 5th and 6 replicates in 4th. Autotrans remained locked up in 4th and 5th. These results were more interesting - 9.8l/100km in 5th and 9.1l/100km in 4th. Although the engine was revving faster in 4th (2800rpm from memory, vs about 2000) it looks like I used less fuel. After an overnight in Balranald, the next day with a bit of a headwind the fuel consumption rose, quite a bit, but again the consumption was better in 4th gear at about 100km than 5th (10.6 vs 12.6).
I've seen lots of comments "not to trust the gauge" but I think re-setting it and travelling far enough for the gauge to give a settled reading should minimize inaccuracy, and the test was replicated a number of times to minimize error too.
Anyway, it LOOKS like it might be more fuel efficient to drive in 4th rather than 5th at about 100kph, but better to use 5th at 110. Why would that be? Is it something to do with the turbo boost characteristics or some weird quirk of an autotrans? What about engine wear rates at 2800rpm vs 2000 , is it a good long term practice?
For those interested, the fishing was challenging in thunderstorms, especially while waving a carbon fibre flyrod/lightening rod. But the 4w driving to fishing spots was fun and the Challenger performed faultlessly. All I had to do was top up the washer fluid and fill up with diesel!
regards
Redtag

[old Jack]

The Challeger auto at GPS 100kph does 2670rpm in locked 4th and 1959rpm in locked 5th, at 110kph GPS 2940rpm in 4th locked and 2150 in 5th locked. Even when the TC is locked often it is more economical to use a lower gear and have higher RPMs. On country trips I watch both the load percentage and the litres per hundred or the litres per hour display on my Scanguage II, the load percentage is the best and most reliable indicator, reduce the load and the fuel consumption will also reduce.

I too find the trip fuel consumption meter accurate within half a litre per hundred over long distances, around the city the trip meter is not that accurate.

OJ.

[Apollo]

Interesting, on a recent 4000km+ trip, I compared the average fuel usage from the trip meter v calculated fuel usage. Trip meter 12.4L/100km v calculated 12.5L/100km. Pretty happy with that!

[Redtag]

The Challeger auto at GPS 100kph does 2670rpm in locked 4th and 1959rpm in locked 5th, at 110kph GPS 2940rpm in 4th locked and 2150 in 5th locked. Even when the TC is locked often it is more economical to use a lower gear and have higher RPMs. On country trips I watch both the load percentage and the litres per hundred or the litres per hour display on my Scanguage II, the load percentage is the best and most reliable indicator, reduce the load and the fuel consumption will also reduce.

I too find the trip fuel consumption meter accurate within half a litre per hundred over long distances, around the city the trip meter is not that accurate.

OJ.

Hi OJ, thanks for the feedback!
I have one of the Bluetooth Ultragauges that I haven't fitted yet. I'll have a look at the gauge options and see if there is a facility for load display.
Around town I always run in 3rd so maybe in the country I'll use 4th unless the speed limit allows 110kph. Are there any negatives to cruising the engine routinely at 2670rpm, other than noise?
Redtag

[old Jack]

Hi OJ, thanks for the feedback!
I have one of the Bluetooth Ultragauges that I haven't fitted yet. I'll have a look at the gauge options and see if there is a facility for load display.
Around town I always run in 3rd so maybe in the country I'll use 4th unless the speed limit allows 110kph. Are there any negatives to cruising the engine routinely at 2670rpm, other than noise?
Redtag

3rd or 4th are my choice around the city.
I feel the engine is under less strain and much happier in a lower gear or two than the auto wants to select, I keep the trans in “D” and use the paddles for about 80% of the time. Yes, noise is increased a little but fuel economy and performance is better. I think 4 cyclinder CRD engine’s are in their sweet spot between 2000rpm and 3000rpm.

Ultragauge does have a load % readout from what I have read.

OJ.

[whitedg]

Ultragauge does have a load % readout from what I have read.

This is correct. I normally have % load, FR PSI, Intake temp, Boost PSI as my main selected gauges, and Voltage, Engine temp, KM since start and litres since start as my secondary gauges (this lot cycle around between pages).

Cheers
whitedg

[Redtag]

3rd or 4th are my choice around the city.
I feel the engine is under less strain and much happier in a lower gear or two than the auto wants to select, I keep the trans in “D” and use the paddles for about 80% of the time. Yes, noise is increased a little but fuel economy and performance is better. I think 4 cyclinder CRD engine’s are in their sweet spot between 2000rpm and 3000rpm.

Ultragauge does have a load % readout from what I have read.

OJ.

Yes, I use the paddles almost all the time on the road, I find them pretty convenient. The only drawback is rolling to almost a stop and then taking off again. The trans drops into back into first and sometimes catches me unawares.
Thanks for the guidance on the Ultragauge Whitedg, I've definitely got to fit it and get it going, I've had it for months, ever since the manufacturer had a special offer.
Redtag