MG-Cars.info

Welcome to our Site for MG, Triumph and Austin-Healey Car Information.

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG Midget and Sprite Technical - Newly refurbished dizzy + improved fuel consumptio

Hi Folks
I have recently fitted a newly refurbished Lucas 25D4 Distributor, converting it to a powerspark electronic ignition unit with one of SimonBBC's little items.
Now I have got the timing set right, it is interesting (to me at least!) to see how the fuel consumption has significantly improved. There was an electronic unit already on when I bought the car, and at the best tuning I could manage, it returned 37-ish on a long fast run. The replacement has allowed a figure of 43mpg, on a 65 - 70mph run of 190 miles. That included sitting in a jam moving a few feet at a time for 30 mins or so. To say I am pleased is an understatement. (and no Nigel, I wasn't holding back on the accelerator either!)
Dominic Excell

Dom,
how many extra miles have you put on the car since the 37-ish, plus this time by actually pushing the accelerator the car's had a little bit of a blow out :)

difficult to compare figures accurately unless the runs were exactly the same in all respects but that seems a big enough improvement to bring a big smile

please note you got better mpg performance by going a bit harder :D

I tried doing a fairly strict mpg run check a few weeks back at a fairly steady 50mph (well 3,000 revs in 4th anyway) but I must have got my figures wrong as first check I had a disappointing 45mpg but on changing I then got a not credible 70mpg, I keep meaning to try again and write the petrol consumption down instead of just remembering it and seeing if I can borrow a SatNav but it's so boring to do

Dom try putting in a full tank of Tesco Momentum99 and see if the consumption improves further
Nigel Atkins

just put this on Gavin's thread but it could be for here too

after you've run the car a bit to know how well it goes try putting in some new NGK plugs (if required) and gap them wider (30 thou) and see if you get improved performance/mpg - course you might also need to check/adjust timing and mixture :)

if it doesn't work you can always go back to standard gap on the plugs
Nigel Atkins

Thats a 14% increase... was the old dissy in bad shape?

Any other mods...a change in fuel???

Id think there would be an increase, due to just new parts and tighter tolerances on the new dissy but a 6 mile increase of 37 to 43 is remarkable

Was the weather super nice... I know if the temp is just right, not harsh cold or melting hot I get good gas milage also

On my dodge with basic efi...when the temp is 65 to 75, it runs like crap and pings alot...below or above that and the truck runs great

Prop

Prop and the Blackhole Midget

depending on how worn the dissy was before there could have been a much bigger increase' plus how the car was previously set up and maintained

Dom has it maintained and set up well before so some or all of the increase could be from the new dissy

which also means Dom has more performance to exploit should he wish too, perhaps get down to the low thirties or even mid-twenties :D
Nigel Atkins

The only change since the previous long fast run was this proper Lucas dizzy, along with new (brass contacts) Cap and plug set from SimonBBC, and a change to the correct type of Lucas coil. The existing coil was a Nissan one which I noticed was running a lot hotter than this one. The previous dizzy wasn't knackered, just not well matched I guess. OK I accept it physically fitted in the engine, and sparked at approximately the right time, maybe just not the right "curve"? I know about as much about distributor curves as can be fitted on the back of a fag packet....
I might well try some higher octane fuel, I remember on my Morris it worked out a little cheaper overall, plus smoother and livelier performance.
Dominic Excell

my car's set up to run on 95 octane but I use Tesco 99 just about all of the time not for the difference in octane because that wouldn't matter but for the package of cleaning additives

I can't say if I get more mpg from using it over 95 octane as I've never checked but as I put in another post Tesco 99 'feels' right to me
Nigel Atkins

Plus you get points at Tesco. Every little helps. LOL.
Lawrence Slater

What worked for me in getting about 40 mpg and in order of preference

Fit HIF 44 with correct needle/jet - groans all round for sure, but immediate benefit in mpg, low down torque and smoothness through the range.

Adjust mix as per SU manual - I run ever so slightly rich

Adjust valves - taking my time

Adjust timing - mainly trial and error for me - Don't tend to use strobe.

Use Shell Optimax

New coil - about 20 quid from MGOC

New plugs and leads

Clean up dizzy internals and new rotor arm.

For sure the 5 speed box also fitted contributes.
Mark O

Shell Optimax, which decade are you living in ;)

what was it called before Optimax when Vauxhall(?), or was it Vauxhall owners, reckoned it ruined their engines?
Nigel Atkins

70's of course Nigel! Traslation - the high octane Shell stuff
Mark O

years ago we done a short holiday tour in Scotland in the BGT and I had a book from Shell showing all the stations in the UK selling their high octane petrol

much to my wife's annoyance I wouldn't stop to fill up at other petrol stations, once we drove a good few miles out of our way with a very low lying fuel gauge needle only to find the Shell station closed earlier in the evening

things got worse but that's another (longer) story

Nigel Atkins

This thread was discussed between 31/03/2014 and 03/04/2014

MG Midget and Sprite Technical index

This thread is from the archives. Join the live MG Midget and Sprite Technical BBS now