44 mpg

Post by **chrisd87** » Sun Sep 20, 2009 4:20 pm

I tend to get in the region of 40mpg in my everyday driving with a standard 1098 engine (that's well serviced but beginning to get a little tired). The economy gets a bit better on a long run but nosedives if the car's driven hard.

I'd be interested to hear the results of modifying an engine for greater economy. Certainly I think replacing the standard exhaust with something a bit less restrictive might help. The Vizard book might be good place to start if you're thinking of making any changes.

Post by **ssnjimb** » Sun Sep 20, 2009 7:54 pm

so if i lean out my mixture just a little i can get more mpg's iam not worried about not being as fast.

Post by **bmcecosse** » Sun Sep 20, 2009 11:06 pm

Yes -to an extent - but TOO weak can lead to burned pistons if the engine is then hard pressed.

Post by **Stig** » Mon Sep 21, 2009 10:10 am

I noticed a significant improvement in performance and economy when I fitted a larger bore exhaust along with HIF38 carb on MG Metro manifold.
With everything else standard (apart from 1.5:1 rockers) I get a reasonably torquey engine and consistently 46mpg on my daily commute of 20 miles each way (50-60mph max).

I've wondered about replacing the engine-driven fan with an electric one - less wasted power at speed and a faster warm-up in winter. I'd rather fit a temperature gauge first though, just in case.

Does your K&N filter have a warm air intake option? I've read (Vizard?) that warm air gives better economy and my engine always runs better on warm days despite cold air being denser etc.

Post by **cormorant** » Mon Sep 21, 2009 4:45 pm

Hi Stig no the filter doesn't have a warm option though I thought cold dense air was better?
46mpg even better! And I have a large bore exhaust waiting.....you have high lift rockers on a standard head?

Post by **bmcecosse** » Mon Sep 21, 2009 5:26 pm

I would suggest you should NOT use high lift rockers- certainly not for economy reasons.

linearaudio · Post by **linearaudio** » Mon Sep 21, 2009 7:39 pm

Putting the large bore exhaust and HIF38 on MG Metro manifold onto 12g940 head has given me far more "go" with the same economy I previously had on the standard set-up, yet I am making more use of the right pedal

. If I could restrain myself, I am sure I would notice an improvement in economy in like for like conditions!
Cormorant, it wasn't all HIFs that had the part throttle leaning device, mine hasn't, though in your situation I would look for one that did have this feature. It is identifiable by a big black round plastic lump on the carb side, and an extra bit of pipe.[/i]

Post by **bmcecosse** » Mon Sep 21, 2009 8:12 pm

The black plastic lump is just a breather for the float chamber!
The large valve head etc will obviously give better economy - and because it has a higher compression ratio with that head - that will help overall efficiency and therefore economy - IF the car's use remains the same. The higher comp ratio if applied to the standard head will still give the economy but without the ability to go much faster, and so will restrain performance and give best economy. Don't get me wrong - I am a great 'fan' of the 940 head etc - and the available performance is then much much better - it's just not the very best way to get economy if that is the primary aim.

Post by **cormorant** » Mon Sep 21, 2009 9:38 pm

Well I might just fit my 940 head and then I will have the choice of economy or surprising modern cars a bit

But first....just filled up with super unleaded will see what happens with this next 25 litre run. Dropped a bit on the last one to 42.5mpg.

Post by **bmcecosse** » Mon Sep 21, 2009 10:48 pm

Interested to hear how the mpg works with that. BP are running an advertising campaign on the basis of 'up to' 28 miles extra. Of course - they mean per tankful, and don't say how big the tank is!

Post by **Stig** » Tue Sep 22, 2009 8:07 am

cormorant wrote:Hi Stig no the filter doesn't have a warm option though I thought cold dense air was better?
46mpg even better! And I have a large bore exhaust waiting.....you have high lift rockers on a standard head?

Cold dense air should be better for performance, but warm air for economy. My engine seems to ignore physics and has slightly more more go when the air's warmer, never figured out why.

I got the rockers for free, they certainly gave the engine more torque and were a simple bolt-on mod. Not the most cost effective if you're buying parts to uprate your engine though.

Have you read Vizard's book? There's a section on tuning for economy in it:

http://www.amazon.co.uk/Tuning-Engine-D ... gy_b_img_a
or
http://shop.ebay.co.uk/i.html?_nkw=viza ... rom=&_ipg=

Post by **eastona** » Tue Sep 22, 2009 7:01 pm

by leaning it out (carefully

), fitting a hot thermostat and driving very carefully I got around 48 - 50mpg last summer when I experimented for a few months.

Generally it was driving style that made the biggest difference. I could wipe out any engine tinkering by driving like a loon.

Anderw

Post by **bmcecosse** » Tue Sep 22, 2009 8:57 pm

Aaaah - perhaps that's where I'm going wrong then ?

Post by **MikeNash** » Sun Sep 27, 2009 9:42 pm

Cormorant,
Besides Visard, have you seen the article in MM of July/Aug 2001 "Fuel Economy" by Phil Catchesides? (Anyone know anything of him?) It covers most of the ground described above but done by him in trials over the previous 2-3 years. I'll send you a copy if you wish.
As a personal comment, the performance improvements above will make little difference to economy. At 50-55 mph you only need about 18-20 HP which is already fully available - what we need is greater efficiency or reduced internal friction. The former comes from increased compression (Catchesides took 75 thou off the head to get about 9.5:1.) and the latter from reduced viscosity of the oil. Catchesides says you can get 2 mpg from changing the backaxle oil to EP 80/90, but I expect you've already done that. Perhaps we should try thinner oil for both the engine and g'box too. I see my BMC Workshop Manual recommends for tropical and temperate climes only SAE 30 (and also 20W/30), much thinner than we use now. And hotter oil might help too; mine is usually only 75-80C max and only gets to the 100C Visard suggests on long fast runs at the height of summer when the oil's near the MIN mark.
Regards, MikeN.

Post by **cormorant** » Sun Sep 27, 2009 10:20 pm

Hello Mike I have Vizard but not seen the article you refer to, would be interested in reading it....yes axle oil is ep 80/90.
At the moment I am doing a couple of runs using super unleaded but the first run, though not complete only looks like heading for 42 mpg. This might be a false reading as the rad has been changed and the old one was blocked so car running cooler and on a 74 stat - will change back to the 82 soon.
Yes would be interested in reading that article!

Post by **bmcecosse** » Mon Sep 28, 2009 12:31 am

Thinner oil does help economy - modern cars use 0W30!! Don't try that in an A series. In winter you could take a chance on 10W40 - but don't go any thinner. Same in the gearbox - it churns the oil all the time - so 10W40 will be fine in there as long as the syncro is not on it's last legs. Axle oil is surely EP 75/80 anyway ?? And yes - best possible barometric compression ratio which can be partly achieved by raising the volumetric compression ratio - but is also best achieved by running with the throttle wide open at low revs in a very high gear, to ensure maximum possible cylinder filling! Otherwise - it's down to using higher pressure in the tyres, ensuring correct tracking, minimising weight, ensuring no dragging brakes/bearings etc - and eliminating any add-ons such as roof-rack/multiple mirrors, air deflectors on the windows/head light leg slashers - and worst of all - the external sun visor! An air-brake if ever I saw one!!

Post by **MikeNash** » Thu Oct 01, 2009 8:12 pm

Erm,
How do we send an attachment with a PM? I've scanned in the MM article for Cormorant and now want to send it. Can such attachments be done only with an ordinary e-mail? If so, would Cormorant pleae PM me his/her e-mail address?
(Small step for mankind, but a giant step for MikeN.)

Post by **cormorant** » Thu Oct 01, 2009 8:55 pm

pm sent Mike

Post by **bmcecosse** » Thu Oct 01, 2009 10:13 pm

At the moment - not possible to attach pictures etc to PMs. Why not just attach it here - so we can ALL read it!

Post by **MikeNash** » Thu Oct 01, 2009 10:21 pm

Cos if I do the writing will be very, very tiny! MikeN.