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Of Cars, CCs and Fuel Consumption Per KM
Rank: Member Joined: 1/22/2009 Posts: 44 Location: Nairobi
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Just a matter of interest, is there any relationship between engine capacity CC and fuel consumption, all other things being constant?
I am interested for example in knowing the difference in the approximate fuel consumption per KM, for a carburetor car, EFI, VVTI etc (petrol only) for 1800 CC, 2000CC, 3000 CC. Assume ideal conditions, no jams. I also want to know if it depends on type of car, e.g. will a Merc 2400 consume more/less than say a Toyota 2400?
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Rank: Elder Joined: 11/13/2008 Posts: 1,565
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@popi, there are so many variables one needs to look at beyond engine capacity....you will find (as was illustrated on SK recently while the passat debate was t its peak) that even if you take two different 1800 cc cars, the results are different.
Some variables, IMHO:
1 - Vehicle weight - I find my 1796 cc rather sluggish because of its weight vs BHP ratio and sometimes it can be outrun by a 1500 cc g-touring (i.e. an overpowered beer can). If you took a Mercedes Actros (without a trailer) and a BMW 725 to Runway 1 at JKIA, the Actros will invariably outrun the BMW at some point...
2 - Body type and aerodynamics - I do not think an landrover with 3000cc can outrun a toyota mark II.
3 - Tyres - not just the tread (or lack thereof), but the width i.e. if a tyre is 14x80x185...its the 185 I mean - not the profile (80)... - I see may people rushing to upgrade the width from 175 to 195 (or 195 to 225) - this increases drag where the wheels meet the road (but the upside it offers greater stability on corners, defensive swerving, etc).
4. Driving habits - staying too long in a low gear - if you gave two people the exact same cars with only 10 litres of fuel and ask them to drive down Mombasa Road at midnight, when traffic conditions are the same for both, one will invariably get further than the other. Staying too long in a low gear, revving too hard on acceleration (like matatus), harsh "start stop" motoring. etc
5. Driving Speed (this may either be dictated by traffic conditions or driving habits) - there is an optimum speed (abt 80-90kph) when consumption is at its best....push it ober 100 and MPG starts to drop. Crawl along t 60kph and its still inefficient,
Sorry I cannot comment on EFI, WFI, etc...
My three optimistic 2010 naira....
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Rank: Elder Joined: 6/27/2008 Posts: 4,114
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...ever heard of the "Caltex Economy Run"? I think they will now have to call it Total Economy Run... Any way; it is organised by the Alfa Romeo Owners Club and they run from Westlands to Naivasha in their Alfas. The winner is the person who consumes the lowest fuel. Most winners clock about 25km/L in 2,000cc machines! No free-wheeling down Kinungi and you must finish within two hours. I talked to one winner and she (yes, a lady) told me the trick is to check your car's manual for the torque tables; then drive maintaining the RPM that yields the highest torque....2,000 - 2,500RPM for many cars. Now you know why they fix a rev counter in your car! Nothing is real unless it can be named; nothing has value unless it can be sold; money is worthless unless you spend it.
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Rank: Elder Joined: 3/2/2007 Posts: 8,776 Location: Cameroon
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How about diesel versions? Me thinks there is little difference among the various eng. capacities e.g. the vx-4200 cc and the noah-2200 cc dithoro wont give a very different milage (~12 kpl) kweli? TULIA.........UFUNZWE!
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Rank: Member Joined: 9/4/2008 Posts: 48
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If you have 2 corolla nze with different cc or as you say 'all things held constant' for sure higher cc equals more consumption. Even when idling, the bigger engine consumes more why? Engines are very inefficient energy convertors, so any slight increase in size goes with an increase in wasted energy Learn Something New Every Day!
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Rank: Member Joined: 5/2/2007 Posts: 536
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@Djinn has captured the key variables
... throwing in my thoughts:
Another variable might be the terrain - I've found that driving down to MSA from Nairobi is potentially cheaper per km than up towards Naivasha, Nakuru since the road is flatter.
Torque vs HP:
low rpm for a max torque from what i've read up (being doing a lot of that lately) generally translates to better consumption for that engine capacity. Typically diesels have max torque at < 2000 rpms. However, I've seen a good number of petrol engines that have max torque from like 1700 rpm - (was looking at the VW engines at this time). Many petrol engines typically have max torque at a pretty high RPM.
@ noinvestor If you have 2 corolla nze with different cc or as you say 'all things held constant' for sure higher cc equals more consumption
>>> generally true. though the way people drive is fascinating to watch.
Many people hardly service their vehicles as well.
@simonkabz
That VX is HEAVY!! - 2.5 tons should consume more than that i think. almost 1 ton heavier than the townace.
Incidentally I've done 14 km/l with a full compliment of passengers + a large sack in the boot on a 2L petrol. - for a VW TDi that would be nothing to write home about though...
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Rank: Elder Joined: 6/27/2008 Posts: 4,114
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novestor wrote:If you have 2 corolla nze with different cc or as you say 'all things held constant' for sure higher cc equals more consumption. Even when idling, the bigger engine consumes more why? Engines are very inefficient energy convertors, so any slight increase in size goes with an increase in wasted energy A few years back, a friend brought my car from the port to Nairobi. When he got here, his first comment was that the car is a fuel guzzler - the "empty warning" lit up at Machakos. Four months later, I drove the same car down to Mombasa. The gauge touched half at Voi and by the time I reached Mombasa I still had about a quarter tank remaining. Same thing happened on the return journey - quarter tank remained by the time I reached Nairobi. I have absolutely no reason to suspect that he cheated...I blame it on his driving style. Another big factor is the road condition. Last Xmas (2009), I drove the same car down to Mombasa. This time I still had a half tank remaining by the time I got there. In fact, I never needed to add any petrol for my running around there. The difference? the road is now smooth all the way from Athi River to Mombasa - I did not see a single pot hole. Nothing is real unless it can be named; nothing has value unless it can be sold; money is worthless unless you spend it.
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Rank: Member Joined: 5/2/2007 Posts: 536
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@mukiha goes to show that we could save quite a bit in our economy if all roads were smooth
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Rank: Elder Joined: 11/7/2007 Posts: 2,182
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@ tuvok, true that. LOVE WHAT YOU DO, DO WHAT YOU LOVE.
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Rank: Veteran Joined: 6/8/2007 Posts: 675
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Very interesting discussion. Driving style therefore is a key factor. I find that in a manual car, I tend to go to gear 5 maybe twice or thrice as fast as many guys I've seen... and nowadays I try to keep to 80 - 90kph, maintaining RPMs of slightly under 2000. However, traffic jams just jumble up everything. I see the benefits on long trips, though. Form is temporary, class is permanent
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Rank: Member Joined: 5/2/2007 Posts: 536
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TDi guys - need some feedback - how good (or bad) is the diesel locally? A friend tells me that the Shell one should be fine but it's good to find out what wazua guys think...
From the stats online, I see that driving a diesel is quite the way to go to save on fuel costs.
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Rank: Elder Joined: 5/24/2007 Posts: 1,805
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@tuvok, I drive diesel vehicles and I can tell you there is nothing better in this town to drive. Interestingly, I find the diesel from National Oil not only cheaper but does more mileage. Maybe it is too heavy... I Think Therefore I Am
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Rank: Elder Joined: 2/16/2007 Posts: 2,114
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@bwenyenye,
Shed some light on servicing intervals and cost i.e oil ,filters etc....
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Rank: Member Joined: 5/2/2007 Posts: 536
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@bwenyenye - interesting stuff - I know some of these European diesels can be sensitive.
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Rank: Member Joined: 5/8/2007 Posts: 709
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Its just a myth that the engine capacity of a vehicle determines how much fuel it consumes.
for example, a car with a 4000 cc will consume less driving at 110km/h that a vehicle with 1800 cc .This is because the 1800 cc will be trying to maintain the speed constantly thus guzzling more while the 4000cc vehicle will not feel anything.
Driving style also determines alot
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Rank: Elder Joined: 5/24/2007 Posts: 1,805
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@Chaka, I service one after every 5000km and the mecha insists that I service the other after every 3000Km ( i think it can actually do 5000 km). It is actually cheaper to service diesel compared to a petrol engine as you do not buy spark plugs.The rest are basically comparable in price. Just make sure you get good oil. The other thing about diesel engines is that they require very good care. If you are not keen on service ( especially how you drive) it can be very deceitful. Guys let me sum it up this way, A diesel engine is a beatiful slave but an ugly master. Always take good care of her ( very cheap) but if you dont and she tipples over, then you will understand what an ugly maser she can be. I Think Therefore I Am
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Rank: Elder Joined: 6/27/2008 Posts: 4,114
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bwenyenye wrote:@Chaka,
Just make sure you get good oil. Now that used to be CALTEX DELO; but now that they've been bought by TOTAL, I don't know what they call it nowadays.... When you fill-up, make sure it is LOW SULPHUR DIESEL. Luckily, this is now readily available in Kenya. Problem with sulphur is that when heated to high temperatures and pressures, in an environment that has steam, it forms sulphuric acid! Then eats away the metallic cylinder of your engine. Nothing is real unless it can be named; nothing has value unless it can be sold; money is worthless unless you spend it.
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Rank: Member Joined: 5/2/2007 Posts: 536
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Thanks for the info @mukiha, @Bwenyenye, @chaka. Been looking at the VW group TDI engines and getting very tempted by their fuel consumption stats + power & torque (especially for the 2.0 TDI 167BHP) . Perhaps one after a couple of years.
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Rank: Veteran Joined: 9/11/2007 Posts: 816
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tuvok wrote:+ power & torque (especially for the 2.0 TDI 167BHP) . Perhaps one after a couple of years. @tuvok....TDi... 167bhp...Good taste! What's your choice...? -Audi A6 AVANT 2.0 TDi 16v Le Mans Estate -Audi A5 Sportback 2.0 TDI SE -VW Golf Mk5 2.0 GT TDI -VW Touran MPV 2.0 TDI 170 DPF Sport
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Rank: Member Joined: 5/2/2007 Posts: 536
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Tempted by Audi A6 AVANT 2.0 TDi 16v Le Mans Estate
But the price....
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