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Mike Fishwick
Forum Member Joined: 04 Aug 2006 Location: France Status: Offline Points: 2742 |
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Posted: 15 Oct 2018 at 10:18am |
Highly-rated diesels are very dependant upon the charge air temperature - that actually entering the engine. Our year 2000 VW Golf TDI is a good example. During a typical French winter the ambient temperature often falls to minus 10 C or lower at night, and the following cold morning a run to our closest large town (a return trip of about 25 miles) used to return 37 mpg from the Golf. I was not surprised, as diesels prefer a warmer charge air temperature to ensure accurate combustion timing, and complete conbustion before the exhaust valve opens. My first reaction was to cover the intercooler with bubble wrap, which improved matters to about 45 mpg. I then fitted my 'winter' air intake, which breathes from behind the engine, just above the turbocharger. This is made from 70 mm drain pipe, offering a far better flow rate than the original, and a quickly-increasing intake temperature reaching about 30 C - the intake pipe being just warm to the touch. The same run in sub-zero conditions now gives about 50 to 52 mpg, with a smoother and quieter engine. As the temperature rises to about 25 C I replace the 'Winter' intake by 'Summer' system, fed directly from the front of the car through a similar 70 mm flexible pipe. In an ambient temperature of about 30 C this system gives 70 - 72 mpg for the above journey. I do not uncover the intercooler until the ambient temperature rises above 30 C, or I am going to do a long motorway run with the trailer attached, as this generates a lot of aerodynamic drag, which can easily cost 10 mpg. Remember - a car engine - particularly a very high-geared diesel - spends most of its time running on light load, the effects of which can be offset to a great extent by keeping the charge air temperature at a reasonable level. High load conditions such as hard acceleration of steep hills are of an intermittent nature, and we seldom carry more than two people. These factors make the intercooler redundant for most of the time. If the charge air temperature rises too high, it is easily detected by a loss of bottom end pulling power. While many people will argue that 'The manufacturer knows best' it must be remembered that the original system has to cater for a wide range of driving styles, loads, and conditions, by a driver who has no idea about what is going on, and who has no mechanical sympathy. I keep the Exhaust Gas Recirculation system disabled to avoid having to remove the inlet manifold for cleaning every few years, and even in this condition the bi-annual French MoT records a zero level of particulate emissions. The exhaust system is the original, and oil (5/40 synthetic) is changed at about 5000 mile intervals. The engine does not have swirl flaps, and has not been touched in this mileage, apart from a preventative water pump replacement and a new turbocharger at about 100,000 miles, caused by a poorly-designed lube oil pipe - which was replaced by a modified version. The Golf has been remapped to 165 bhp/275 lb-ft, and seems quite happy with this arrangement, as it has now covered 235,000 miles, and looks set to outlast me!
Edited by Mike Fishwick - 15 Oct 2018 at 11:23am |
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issus
Region Chair Joined: 02 Jun 2010 Location: Northants Status: Offline Points: 1337 |
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Have an E46 320d Sport Saloon which has an oil change every 7 months. A year ago I had the Swirl Flaps removed at 124k - only bebause my Indy garage persuaded me to have them removed!
It is nothing unusual for me to obtain 50+ MPG on a reasonable trip - total of 80 miles. Urban driving its about 35/40mpg. Mike Fishwick is quite correct to to state the importance of the ambient temperature - it does make a difference on cold wet days. If you are going for the Touring Version best to stick to 330 ltr engine. Otherwise the 320 engine for the Saloon will give you economic returns. The real secret is frequent oil and filter changes with well maintained tyres.
Edited by issus - 14 Oct 2018 at 10:56pm |
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E46 320d Sport Myst Blue 054 reg - probably the best BMW ever
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Mike Fishwick
Forum Member Joined: 04 Aug 2006 Location: France Status: Offline Points: 2742 |
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The 'Combined' fuel consumption figure from most manufacturers is the very best you may get on that one day a year when everything is in your favour - from ambient temperature, fuel quality, driving style, and traffic/road conditions. It is similar to peak power figures - they are probably the best attained by one of several test engines, and is used by marketing men to make their product look good to a certain type of prospective customer. A couple of 320d-owning friends also found that they struggled to reach 50 mpg in normal gentle driving, and seemed to be somewhat under-powered in an E46 touring, another good reason for preferring the 330d. Again, this car's consumption figures seem to be also inflated a little, with a friend who is not a fast driver usually finding that consumption varied between 37 and 45 mpg
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m3kos
Club Member Joined: 30 Oct 2007 Location: United Kingdom Status: Offline Points: 567 |
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i run an F31 320d as a daily. Mostly 40mph A roads, town driving with a weekly long run. Mine has the N47TU engine i think the newer ones (post Feb2015) have the new engine which is much better i average 39mpg, i have a heavy right foot if you look at BMW car Magazine, the editor runs a 335d and he's getting 40+MPG personally, id go for the 330d, it will have a similar overall MPG at around 40 and have more useable power the technical info is utterly useless and inaccurate, its all done in a lab and never in the real world. Mine should be doing 50+ according to the From Pistonheads "both cars on my normal trip to work, which is a 40-mile mix of dual carriageway, B-roads & (at some points) heavy traffic. The trip usually takes about an hour (so 40mph average speed over the journey, but peaking at around 100 on the odd occasion)" The combined figure for the BMW is 62.8mpg. He got got 46.7mpg in a 320d |
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Norrie
Club Member Joined: 15 Jul 2012 Status: Offline Points: 4047 |
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You are best to look at the BMW technical information and compare the two especially in terms of MPG and the purchase price. There might be one or two people who have owned both, but I doubt it.
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Globus8484
Forum Member Joined: 07 Oct 2018 Location: Bradford Status: Offline Points: 2 |
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Hi I'm new to this club. I am thinking of buying a 330d xdrive touring or 320d xdrive touring. I can't decide which one to go for. But mpgis quite important. I do a mixture of town and motorway driving. Any info on which car is a better option.
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