Real world fuel consumption - Help please !!!

[wydsiwyrg]

I don't quite get as good fuel consumption from my 340 GL 1.7 as others.

In the last two weeks I've done 180 miles of all town driving (cost 35 quids worth of petrol!); so about 20 mpg.

Before that I did 250 miles of all motorway driving (cost 30 quids worth of petrol) so about 33 mpg.

Any tips to get better fuel consumption? (I use very little choke, and never drive above 70 mph).

[Clan]

The 1.7 is the one to get for economy , it is a much lighter power unit/transmission than the 2.0 litre , the early 1.7 with 3 nuts holding the cam cover on (1986) has a higher compression ratio and feels more lively too .
The ideal conversion would be the B18U or B18E from the 400 series . The body is just too heavy for the 1.4 for economy although there is nothing wrong with the 1.4 it is a willing unit , but has to work harder than the 1.7 accelerating the mass of the body hence usess more fuel . My brother did a trip to scotland up the motorway and got 48 mpg from his 1988 1.7 pulling a small trailer .

The 360 carb can be economical too but the gearing is incredibly high and it has such a heavy flywheel that it takes 5 seconds for the rpm to go from 1000 rpm to 5000+ rpm in neutral! all the 300's have a heavy flywheel to protect the long relativly weak transmission shaft from suddem torque surges . so it is best to drive them in as high a gear as you can and not to rev them to get moving ...

[foggyjames]

A B200K has the same weight flywheel as every other B200/230 of that vintage...but the tiny throttle opening stops it spinning up quickly....stops it making decent power....but also stops it drinking like a fish The prop shaft seems to be stronger than most people give it credit for. A number of tuned cars (a couple with 200+bhp) have been running reliably in hard use for years now.

1.4s are ok as long as you drive them sedately. They drink like a fish if you push them hard. I've no direct experience of 1.7s...but a lot of people seem to have trouble with ones that don't perform like they should...both in terms of fuel consumption and 'go'.

cheers

James

[Clan]

The B19E has a different flywheel to the bigger cars and has a heavy mass cast in around the outside much like the B14 flywheel . I would guess the B 200 is the same as the B19 and B200 in the 360 use the same clutch . The relativly small choke venturis in the B200K carb will infact improve low rpm torque and drivability up to 3500 rpm but limit ultimate bhp . It is quicker to get going by changing up to second gear as quickly as possible to minimise wasting time accelerating the flywheel mass too much !

The propshaft itself wasnt an issue on the 360 , neither was the alloy B14 one , my 210000 mile 1980 343 still has it's original propshaft. The problem with the alloy one was engine mountings sagging and misaligning and stressing the big bionded rubber bushes in each end of the propshaft , eventualy the bonding would fail if the mountings were neglected resulting in misalignment. Another problem was inexperienced mechnaics not knowing the correct way to fit the propshaft on it's splines it would often be not fully engaged on the output shaft or input shaft splines and these would strip due to this , luckily the propshaft splines were weaker so the clutch shaft or transaxle input shaft was not damaged . The CVT had a better idea a spring to press the propshaft all the way on to the splines and no clamps . There was never enough torque from the B14 to over stress the alloy propshaft as was later proved when the 300 was fitted with the 1700 engine in 1986 and this propshaft turned out to be just as reliable .

The 360 propshaft is completely different due to the much higher torque from this engine , the alloy propshaft wouldnt have coped, so a large very heavy over engineered Torque tube was developed with a 25mm shaft supported on 3 spaced out bearings through the centre to connect to the transaxle input shaft at the rear of the car so the engine and transmission was effectivly one unit literaly held to the car with two bolts at the front and two bolts at the rear .
The weak spot was the coupling used to join the shaft to the transaxle input shaft ,it was made of a piece of splined tube about 4 inches long slotted and clamped by the same clamps used for the alloy propshaft . the weakness was the slotting , cracks developed from these slots It looked a bit of a bodge and sometimes these failed resulting in loss of drive , again when this happened you could often get away with just fitting a new very expensive ( over £100 in the 1980's ) coupling sleeve as this rounded off before the transaxle shaft splines . My own 1983 GLT has fared ok with 200.000 miles and no problem in this area .

Neglected 300s these days are thirsty due to a number of reasons , the B 14 suffers from the accelerator pump jet and often the top of the carb itself coming loose and whenever you open the throttle a huge amount of fuel by-passes the jet and floods into the carb , the engine falters so you open the throttle further pumping in masses of extra fuel . It is just a matter of tightening the jet and re fitting the top and tightening the screws if the gasket hasnt worn completely away !

The 1700 suffers a bit more with it's carb , inexperienced mechanics overtighten the flange nuts causing the flange to warp and air gets drawn in ,so the co screw is richened up to compensate by those who don't understand , eventualy the flange has to be filed flat . Volvo brought out a repair kit which was a rubber spacer which would take up the gap of a mildly warped flange .
Another point which gets worse and is probably affecting all of the remaining 1700 300's is the float heigh , the float gradualy absorbs fuel over about 8 - 10 years and sinks , raising the fuel level in the carb a lot causing high fuel consumption , symptoms are lots of cranking and black smoke when re starting after about 20 minutes and high fuel consumption and cutting out when going around a roundabout with full throttle as the high float lever sloshes and overflows directly down the carb into the manifold .
Otherwise the 1700 engine is totaly reliable except for the distributor cap and rotor arm , change them for ORIGINAL parts every two years ...

The 300 is still a great car with more room in the back than todays "big" volvos ......

[foggyjames]

I don't know about the early cars, but if it's a B200 with a Renix unit, it'll have exactly the same 'dished' flywheel as a B200/B230 in any of the larger cars. B230 Turbo cars spin up much faster than a carbed 360 (I agree it's slow!), as does my 360 now it has the big carbs on it. Even a late model B230FK/FT with the uber-heavy 'dual mass' flywheel spins up a lot faster than a 360's B200K.

A lighter flywheel would probably help, but it's not the primary cause, in my eyes. When I put the big carbs on my 360, I gained a huge amount of low-end torque (and even more at the top end!). As I see it, that undersized carb was purely an emissions and economy measure.

The torque tube is an interesting piece of design. As well as solving an engine mounting headache, I suspect they were also struggling to stop the box from tipping over when using the standard 340 'bushed' mounts.

cheers

James

[Clan]

The 360 flywheel is a different part number to any of the other cars with the similar engine . As the engine also takes a long time to slow down from 5000 rpm to idle it can be nothing else but the mass of the flywheel can it ... .
That seems a good modification to fit the larger carb , there was a B200K engine in the 1984 240 with this Pierburg carb it was very flat caused mainly by the intake pipe on top of the carb being too small , volvo's mod when they got a complaint was to fit the 360 carb complete with its larger intake pipe housing on top .
I think the reason for the restricted carb on the 360 was that if it had the standard 740 arrangment it would be just as fast as the more up market 360 GLT ! It was also restricted by the very high final drive ratio ! It was satisfying changing into 5th at 110 mph though :-) whilst the GLT was doing over 5000 rpm in 5th at this speed
It is all about marketing just like the restricted B234F on the 740 GLT It has a very small inlet manifold to restrict it to the same power as the B200FT so as not to outshine it . All that extra complication and mechanical balance shafts etc and only 20 more bhp is a waste that engine should have been putting out about 170 bhp as standard.

The torque tube idea wasnt new porsche use it and some very older makes , but as you say it takes any twisting force out of the transmission unit mounts so they only have to take up/down stress .

[Chris_C]

Clans got the main points for economy... I only get that economy with a clean airfilter (12months or just under however many miles the book says, an ecnono halfords own one is £6.09, and makes the biggest difference if it hasn't been done). Rotor cap and arm really really should be dealer parts, others are shocking.

Oh, and I rebuilt my carb 18months ago, new floats, gaskets, needle valve, and whatever else I found in the rebuild kit

Bl**dy thing just went and blew a hole in another Bosal exhaust though, I swear Bosal make them out of kit kat wrappers... I've seen more solid AX's . However, new air filter only this weekend, as it had got a bit thirsty (down to 35ishMPG) and she's just done 215 miles to £21 brim to brim of tank, at the 102.9. I make that 48mpg, not bad for a seirra sized 19 yr old motor thats done 195,000miles! That was doing GPS 70, motorway only.

[Clan]

Originally Posted by Chris_C

Clans got the main points for economy... I only get that economy with a clean airfilter (12months or just under however many miles the book says, an ecnono halfords own one is £6.09, and makes the biggest difference if it hasn't been done). Rotor cap and arm really really should be dealer parts, others are shocking.

Oh, and I rebuilt my carb 18months ago, new floats, gaskets, needle valve, and whatever else I found in the rebuild kit

Bl**dy thing just went and blew a hole in another Bosal exhaust though, I swear Bosal make them out of kit kat wrappers... I've seen more solid AX's . However, new air filter only this weekend, as it had got a bit thirsty (down to 35ishMPG) and she's just done 215 miles to £21 brim to brim of tank, at the 102.9. I make that 48mpg, not bad for a seirra sized 19 yr old motor thats done 195,000miles! That was doing GPS 70, motorway only.

Yep thats not unusual fuel consumption for a 1.7 in good condition . Why dont you try a genuine Volvo exhaust kit with a 3 year guarantee ? Prices are very close to cheap makes which only last a year or so ...

[Chris_C]

I'm not sure you can still get them, but got to be worth a go with a 3 year guarentee! Cheers, I'll look into it!

[foggyjames]

There's no doubt that the flywheel is heavy, and absolutely doesn't help, but I promise you that it is identical to the ones used in all other B200/B230, including versions which spin up far, far faster than a B200K. The difference in part numbers is due to the timing pattern around the outside - 300s have a 44-4 (or similar) pattern for Renix, 740/760 turbos have a single peg to indicate 90 degrees past TDC, 240s and 740s with the timing pickup in the dizzy have blank flywheel, while LH2.4 equipped cars (late 240s and 740s, plus all petrol 940s) have a 60-2 pattern...similar to the Renix pattern, but with more holes! Actually, Chris has pictures of this, I believe

All I'm getting at is that lightening the flywheel alone won't do the job. Of course it's one the main things which will help, but there are other things to consider.

cheers

James