Had my Toyota auris t180 for 2 years now; finding 180bhp and 400nm quite fun and a very relaxing drive. It will do 43mpg daily or more on a longer run.
I like learning how things work so whist reading up and learning about common diesel problems like, EGR valves, DMF, turbo failure, soot built up, black smoking, limp mode, injector problems etc... i started to wonder.
I have adapted a specific driving style. I give it some beans, 70% throttle openings and usually try to keep the revs between 1.8k and 2.6k max torque. I also maintain steady speeds just under or on boost; 1.8k. So get up to speed quickly when the engine is running efficiently. I also accelerate through the rev range regulary and i occasionally put the car under full load for 10mins or so for a decent clear out. I always idle for 20seconds before turn off.
My reasoning is, the compression is maintained, the exhaust temps are kept nice and high, soot build up should be reduced, possibly less smoking and carbon build up, the revs just off boost mean that big power requests are answered with enough air to fuel mix from the turbo being ready so you dont get big clouds of black smoke / unburn't fuel. So at between 1.8k and 2.6k there is possibly less stress on the DMF and turbo. I also find that providing you maintain a steady speed there is little difference in fuel consumption between lower RPM's and say 2k. Infact 2.5k would also give similar consumption figures and fast acceleration means less time drinking fuel and more time sipping when at your required speeds; improving MPG for me.
Is my theory correct or are there any knock on effects of giving it the beans (50-70% throttle) for acceleration. I always wondered what the relationship is between people who pootle along or even try to request too much power off boost and who change at say 2k... what effect that has on soot, DMF, turbo etc.
Edited by OldSkoOL on 19/05/2009 at 00:10
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I would think the toughest thing for the DMF, other than overheating the clutch and shock loads, would be maximum torque (which you won't get unless you give it 100% beans, not 70%).
Broadly speaking (NC would refer to his engine map) maximising torque demand rather than revs will give best economy. That said 43mpg isn't very impressive is it? My CRV does that. A colleague bought one of these three months ago and got the same mpg - he didn't like the car though, and has now bought a 330D coupe which is returning 46mpg!
If you want to keep the injectors clean, and reduce the variability of fuel, you might consider using premium diesel if you don't already.
I believe the Auris has a dpf - so shouldn't be ejecting soot anyway.
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A modern car engine is controlled but its engine management programming, so 50% of throttle may mean 100% acceleration for a while before leaning back to match throttle position with desired speed. The turbo has the least amount of stress when it's not actually turning, and the most stress when it's spinning up to full revs.
You can't request too much boost, the amount and progression of boost is managed within pre-defined limits written into the engines software programmming. A remap or tuning box can/will alter these limits and as such their designers need to be aware of the cars mechanical limits otherwise component failure will occur.
As long as you haven't been driving the car fast or hard prior to shutdown there is no need to idle for 20 secs before turning off. Modern turbos use oil as lubricant so they don't need to be cooled down as much as with the pre-oil tyres. A good practice is to drive the last mile or so gently to help cool things prior to shutdown.
Keeping the revs around max torque provides the greatest engine efficiency but other factors come into play regarding fuel consumption, For example, running the engine at say 1500 rpm would produce less torque but the lesser speed means less wind resistance and friction to overcome which may equate to better fuel economy.
Pootling along is what diesel engines are good at, contrary to rumour, lots of low down torque and anti-stall engine management keeps things in order. Using various revs is fine, high revving any engine too often simply reduces its life expectancy.
DMFs are designed to provide isolation of the frequency below the engine?s operating RPM, usually between 200-400 RPM. The time that the DMF works hardest is during engine startup and shutdown.
Choosing the cleanest fuel to use for the engine is as important as how the car is driver. A cheap fuel or a mixture of fuels usually translates into more smoke and more internal gunk build-up.
Soot is produced as a result of an over rich mixture/air combination, mixture of different fuel brands or when an engine needs servicing. A quality fuel produces a lot less soot. Also the engine oil contains additives designed to suspend soot within the oil otherwise soot will wear the internals of an engine, hence why it so important to change oil and filter in due time.
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What an informative post. Thanks.
VBR......MD
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You don`t mention ever taking it above 2,600 revs. I would worry about it sooting up and regularly take my own diesel up to 4,000 revs on full throttle.
That`s momentarily though. Typically will hold 3rd up a motorway ramp until doing about 80mph. Hot engine of course.
Previously, when only using low revs - for the first time (in a year) going up to 3,000 revs put it straight into limp mode. No codes - but dealer said to use higher revs at times. Since then, 18 months ago, no problems and it`s running more freely.
Pre MOT I run both our diesels foot to the floor in second gear at maximum engine revolutions - repeatedly over the course of 30 minutes. The soot coming out of the tailpipe on the first runs at max revs is quite convincing ;-)
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"Soot is produced as a result of an over rich mixture/air combination"
Mike, It`s not like that. Diesels are running with maximum air at all speeds.
Regards
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Oil and filter change no less frequently than 10,000 miles using known brand oil of the appropriate grade/spec and an OEM filter, explore the rev range every so often, and don't be afraid to let the engine work for a living. Don't thrash it, but don't mollycoddle it either. Let it warm up before you boot it, and let it tick over for 30 seconds before switching off (probably unnecessary as mentioned above).
Run it on any UK forecourt diesel - it's all good enough.
Don't put petrol in it. ;-)
Had many hundreds of thousands of troublefree miles out of turbodiesels of various types - old Ford 1.8TD and Pug XUD to modern "antichrist" common rail Renaults - sticking to these rules.
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"Soot is produced as a result of an over rich mixture/air combination" Mike It`s not like that. Diesels are running with maximum air at all speeds.
OK then. Too much fuel injected for the available air, and/or poor combustion?
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Minor variations in driving style aren't going to make a lot of difference to MPG or engine life on a car that is already economical by nature.
One tip on a turbo engine is to run the engine at tickover for 30 seconds or so before turning off to minimise oil starvation to the turbo bearing.
And while you're driving along making sure you're giving it 70% welly instead of 75%, you might not notice that you've just passed a speed camera in a 30 mph limit at 42 mph!!!
Edited by Sofa Spud on 19/05/2009 at 22:38
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