B14 fuel consumption

[Joe Harding]

Originally Posted by macplaxton

My Spritmonitor.de records (incomplete):

1) 1978 Volvo 343DL B14.0E CVT

Best: 30.7 mpg / Worst: 20.0 mpg



2) 1982 Volvo 343DL B14.2E CVT

Best: 33.6 mpg / Worst: 24.0 mpg



Click on icons to see breakdown of figure or look up other cars. I'd expect it to be in the ballpark 25.7 - 35.3 mpg for general use, but short journeys I'd expect could pull it below 20. Do the 87- cars not have the idle solenoid cut-off relay to help out?

I understood this little relay was to stop dieseling run-on at switch off.

[classicswede]

On a run my cvt does just over 30mpg but never really checked what it does on short runs

[macplaxton]

Originally Posted by Joe Harding

I understood this little relay was to stop dieseling run-on at switch off.

Your thinking of the electro pilot jet on it's own. These go back to the early 1970s and the DAF days. Here's one on a 44:


pilotjetelectro by macplaxton, on Flickr

They're just a solenoid and work on the basis of ignition ON - jet open. Ignition OFF - jet closed.

The fuel shut-off relay, is a RPM controlled switch, which shuts the above solenoid under certain conditions to save fuel.

fuel_cut-off_relay by macplaxton, on Flickr

fuel_cut_off_wiring_01 by macplaxton, on Flickr

Now although the manual says MT only from 1987, the picture of the box above is from a 1989 CVT car...


V300_FCO by macplaxton, on Flickr

[Clan]

All interesting stuff , good response , keep it coming please ... Those figures are about what i remember when i was working with these cars from conception until the end ..
The tank is 10 gallons by the way , so anyone should get over 300 miles to a tank easily , there is still a lot of fuel left when the light comes on .. unless you run it dry you cannot base any fuel consumption measurement by "tankfulls" .. My 1980 343 was on LPG from 1979 to 1990 .

The CVT was horrendously thirsty when it wasn't working properly .
If you never went over 60 mph and it was working properly consumption could be good .

I have a lot to say later about how to improve the fuel consumption ..

[classicswede]

Originally Posted by Clan

The CVT was horrendously thirsty when it wasn't working properly .
If you never went over 60 mph and it was working properly consumption could be good.

My CVT is not working correctly at all. I have disconnected teh vac pipes as the diaphrams are leaking on the CVT, the clutch is need of changing and it does not like going slow. With keeping the speed between 70 and 90 it drives about the best and consumption was ok at those speeds. Swapping the CVT for a spare I have is on my to do list

[Clan]

Originally Posted by classicswede

My CVT is not working correctly at all. I have disconnected teh vac pipes as the diaphrams are leaking on the CVT, the clutch is need of changing and it does not like going slow. With keeping the speed between 70 and 90 it drives about the best and consumption was ok at those speeds. Swapping the CVT for a spare I have is on my to do list

well once you get over 60 the centrifugal weights change up the gears into overdrive so that would account for that , Can you still buy diaphragms , diaphragm springs ( which break) , seals for the vacuum input pipes to the pulleys , Vacuum control valves or repair kits for the small valves in there ? And the tachometric relay ? People weld the chassis and melt the vacuum pipes which run through the members too !

[classicswede]

You can still get the diaphragms and the springs should still be available. I stock repair kits for the vacuum valve and control relay.
As I have a complete working unit I will just swap it but will keep the old one for repair at a later date.

[Clan]

Well I'm now averaging 42 -45 mpg on a weekly basis , same journey every day sometimes slow moving traffic for about 20% of the journey . 2 long hills and a short steep hill to get up on the way .

How? i asked myself , I was expecting just over 30 mpg like the rest .
well:

The later 340 has a one piece rear wheel bearing , same as front wheel drive cars , lower friction than the older two ball bearing races each side .

The car has the idle valve fuel cut off as described above .

There are aerodynamic plastic pieces around the front panel and behind the bumper.
The car runs very freely and will coast for a long way , however this will not save fuel as the idle jet will not close off .


I fitted the 1.7 5 gear transaxle to replace the 4 speed M45R . the lower 4 gears are the same , 5th is higher , same rear axle ratio. I use it as often as possible .
( Perfect low mileage 4 speed M47R transaxle available )

Low friction Castrol Syntrax Synthetic Final drive oil

ATF in the gearbox not engine oil

5w/30 Synthetic engine oil .

new Vriedstein snowtrac 3 tyres @ 35 psi .

The instrument panel has the vacuum gauge .

have a 92 degree thermostat

I'm not particularly driving for economy but not exceeding 60 mph except down hill ,

Idle speed is 1000 rpm , haven’t had chance to turn it down yet .

fuel tank is filled to the brim each time ,


So there it is , still room for improvement , might fit an Oil to water heat exchanger under the oil filter to warm up the oil quicker . then drive for economy … stop/start anyone ? Fuel injection would help , must be a later Renault using this engine with injection ?

Nice to have modern car fuel economy from my 28 year old Volvo  And it goes better than any 340 1.4 i have driven before when you get the revs up .

Like the recent Driv e models there are about a dozen modifications they have done to help economy , each one on it’s own would make no noticeable difference , but the sum of them certainly does ….