Tweaks For Better Economy?

[Laird Scooby]

Originally Posted by Exasperant

With luck I'm about to be the owner of a "why did it have to be silver, everything else about it is what I was looking for!" 940 2.0 LPT.

I'm wondering if there are any known tweaks to improve mpg. Not worried about outright performance, I already have a nippy throwable car for those moments.

I spotted some people selling chips claim their maps give "more economy", but I'm wondering how true that is? I'd have thought manufacturers would sacrifice performance for fuel efficiency...

Originally Posted by 360beast

2.0 LPT? do you mean 2.3? They didn't do a 2.0 LPT.

Manufacturers have to map cars for a best of both worlds and make them easy to drive so yes chips can increase performance and economy. They factor in longevity of the parts and not stressing the engines etc.

I and a couple of my mates all think silver is the best colour for the 940.

Edit: now I should actually answer your question, the best thing to do would be to give the car a stage zero. So new plugs gapped to 0.7mm (NGK BPR6ES), new oil and filter (genuine volvo oil filter only), air filter, distributor cap, rotor arm, HT leads (Bougicord only), PCV box cleaned out thoroughly with new O-ring, new belts and front oil seals and a new fuel filter.

There might be more things I've not listed but I can't think of them at the moment.

In addition to Lukes excellent advice, i would add only run it on 98 octane (95 is likely to cause detonation aka pinking which you won't hear, the knock sensor in the engine will though and retard the timing making it less efficient) which is likely to give you better performance as well.

Also some time before doing the oil/filter change, add 0.5L of Carlube ATF-U to the engine oil. When you do the oil change (leave it a minimum of a few days driving), after the old oil has drained and you've refitted the sump plug and new filter, add 0.5L of ATF-U to the engine then top up with your choice of 10W40 semi-synthetic oil to the right level.

I do this on both my beasts for many reasons, on the non-Volvo in addition to everything it does on my Volvo, it helps keep the hydraulic tappets working as they should. On all engines though it helps free sticky piston rings, valves, revives oil seals (won't cure major leaks but can remove minor ones) and generally cleans the engine gently. There are a couple more things it helps with (such as improving emissions) as well.

Also when you clean the PCV system out, make sure the inlet manifold stub is clean on the inside (carb cleaner) and clean the inside of the throttle body and AICV with carb cleaner too.

On no account EVER touch the throttle stop screw on the throttle butterfly. We've had a few on here lately that have decided to play with this to solve an idle problem and caused themselves even more headaches!

Remove fuse ~1 after doing the service for 30seconds and refit. Also, where does the temperature guage sit after about 5 minutes of normal driving from cold? If it's not halfway, invest in a new thermostat. Also if the mileage is 100k or more and there are no signs the Lambda sensor has ever been changed, consider changing it in the near future. They only have a service life of ~100k miles/10 years anyway and a weak/failing one can cost you precious mpg and maybe an MoT fail.

A dose of injector cleaner when you pick it up will help on the journey home (try and get a sustained high speed drive like a motorway to help get the cat hot and burn off excess carbon on the way) to clean the injectors :

https://www.halfords.com/motoring/en...te-247886.html

Other than that and all the usual stuff such as wheel alignment, tyre pressures, making sure brakes aren't binding etc and you should be fine - i can easily get 32mpg on a decent run out of mine and that's a 2.8 V6 auto!

[MiniNinjaRob]

I have a 940HPT.

Stage one to ensure the car is running right. Most engine mods, at least to start, concentrate on upping boost so won't improve economy.

My ranges between 40mpg on a long 60mph motorway run to 18mpg on short trips round my (hilly) town.

Decent super unleaded makes a difference. Not really done a lot of testing of that but I am sure it makes a few more mpg, more than 10% difference I reckon.

[volvo always]

Interesting to run a 940 on 98 unleaded. Always run my B230FK on 95.

Will have to try 98. My Lambda sensor is old. 5 years with me when bought car and swapped it out from old exhaust and refitted to new exhaust 5 years ago. What is a good genuine one?

James.

[Laird Scooby]

Originally Posted by volvo always

Interesting to run a 940 on 98 unleaded. Always run my B230FK on 95.

Will have to try 98. My Lambda sensor is old. 5 years with me when bought car and swapped it out from old exhaust and refitted to new exhaust 5 years ago. What is a good genuine one?

James.

You've been lucky!

Usually when they are removed, they let go with a bang and this makes a shockwave through them that damages the zirconium rendering it useless or at least causes premature failure!

Keep an eye on your economy, if it starts dipping, time to get the multimeter out and see what the Lambda output is doing!

[tofufi]

Originally Posted by Laird Scooby

You've been lucky!

Usually when they are removed, they let go with a bang and this makes a shockwave through them that damages the zirconium rendering it useless or at least causes premature failure!

Keep an eye on your economy, if it starts dipping, time to get the multimeter out and see what the Lambda output is doing!

Interesting you say that Dave. My 340 turbo has a 'used' lambda and returns mediocre fuel economy... could also be due to gearing and being fun to make progress

What readings would you expect from the Lambda/how to test?

[tofufi]

Originally Posted by john.wigley

If you are looking for economy, your own input can have a significant effect. Long runs with few cold starts help tremendously. My 944 returned well over 30 MPG on a 75 mile commute with just the two cold starts daily. Avoiding harsh braking and using gentle acceleration wherever possible, removing roof racks when not required and not carrying excess weight around (the 945 makes this very easy(!)) will all help.

I'd definitely agree with this ^^ combined with a stage 0 tune up to make sure everything is doing the absolute best it can.

I'd also recommend playing around with the tyre pressures. I've found increasing mine by about 3PSI all round has given me another MPG.

I do mostly long runs in mine, rarely exceed 70 (but sitting at 70 where possible) and mine has averaged just over 45MPG for the last 30k+ miles. It is the 6 cylinder diesel though, but most people struggle to top 40mpg with the diesels

I also found retrofitting cruise control gave me at least 1MPG

[Laird Scooby]

Originally Posted by tofufi

Interesting you say that Dave. My 340 turbo has a 'used' lambda and returns mediocre fuel economy... could also be due to gearing and being fun to make progress

What readings would you expect from the Lambda/how to test?

Multimeter on 0-2V range, engine hot and idling Jim. Put the +ve probe of the meter on the Lambda output wire, -ve probe to a good known earth and it should cycle between 0-0.9V centreing around 0.45V and be rhythmical. In practice it may be between 0.3V and 0.6V but if the voltage is struggling to get above 0.5V on the rich part of the cycle then chances are the Lambda has died.

It's easier to see with an oscilloscope but any reduced output voltage puts the Lambda in question.

[Exasperant]

Originally Posted by Laird Scooby

In addition to Lukes excellent advice, i would add only run it on 98 octane (95 is likely to cause detonation aka pinking which you won't hear, the knock sensor in the engine will though and retard the timing making it less efficient) which is likely to give you better performance as well.

On no account EVER touch the throttle stop screw on the throttle butterfly. We've had a few on here lately that have decided to play with this to solve an idle problem and caused themselves even more headaches!

I'd wondered about the octane thing - I've never had a car with a knock sensor, so have no experience of how much difference it makes to economy or performance. Definitely worth a try.

And... Definitely not going to try touching the throttle stop screw then!

[Laird Scooby]

Originally Posted by Exasperant

I'd wondered about the octane thing - I've never had a car with a knock sensor, so have no experience of how much difference it makes to economy or performance. Definitely worth a try.

And... Definitely not going to try touching the throttle stop screw then!

I'm surprised you've not had a car with a knock sensor before, almost all cars from the mid-late 80s had them.

With my 760, the only fuel it runs right on is BP Ultimate, all supermarket brands are now "emergency use only" after Sainsburys changed from having BP as their sole supplier and my economy dropped through the floor. Normally all my running is short runs so i generally get 25-26mpg although that was compromised by a handbrake fault following an MoT - long story!

Using Sainsburys (while i hadn't realied they were no longer supplied by BP) super unleaded i was down to 14mpg. Changed to BP Ultimate and immediately went back up to ~22mpg (this was with the handbrake fault) and now the fault has errrrrrr.......... "cleared itself" it's back up to where it should be.
Coincidence? No. My other beast was down to 18-20mpg on Sainsburys fuel as well, switched that to BP Ultimate and back up to 28-30mpg for normal runs, haven't had the chance to do a long run as yet for various reasons.

Yes, BP Ultimate is ~10% dearer than the supermarket equivalent but it returns 50% better economy - no brainer in my book!

For the record, i know the problem with the handbrake and have new disc/drums, shoes, pads, flexi hoses etc to fit. I can finally get onto that sometime soon, now i have my other beast back!

[baggy798]

Remove nearside wing mirror.
Tape up gaps around headlights, cover half the grille.
Run 4 space saver tyres.
Lightweight battery.
Put panels underneath chassis so it's flat.
Remove the seats, radio, heating system, sunroof, glass, carpets, trim.
Drink some Carlube ATF-U.
Splash some meths behind your ears.
Carry nothing in the car, not even yourself. Convert it to remote control and drive it by following it in a diesel.

Should get over 30mpg.