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MG Midget and Sprite General - 60 mpg A Series Midget?

With the price of fuel rising faster than ever has anyone thought of making their Spridget more economic?

When I first got my Sprite I converted it to a single SU and was pleased to find it managed 44mpg on a long run at 60ish mph. That was just a standard car with a 4.22 diff. Eight years on the car has the same single SU and even a 5 speed box but I doubt it will do better than 30mpg!! Like most people I've spent all my time and money making it go faster with no regard for economy. Anyway, I've been wondering lately if it would be possible to build an engine with economy in mind and 60mpg as the target. Quite a few of the mods I've made should actually help economy, well two anyway! The 5 speed box and fact it is a lot lighter should help.

As my car is used for hillclimbs it would have to be just an experiment for maybe a long road trip. I was thinking of building up my spare engine to mostly standard spec but with a high compression, Hif44 carb and nice freeflowing exhaust. A diff change from my 4.5 to 3.9 and back to the standard tyre size should see the gearing nice and high. I reckon all that, the better aerodynamics of the hardtop and 10% less weight in the car should see it getting well over 50mpg.

Anyway, it's all just a pipedream at the moment, though every time I fill up I think more seriously of it. I realise the money I would need spend on the engine would take thousands of miles to get back but thats not really the point.

Anyone thought of doing something similar or am I just being tight??!!
John Payne

948 engines around here are mostly "free" for the taking. So I'd think that a mkI sprite with a 3.9 rear end and a stock engine would do pretty well (as long as you are not in a hurry). Change out the bonnet for a light weight/aerodynamic unit and find some lightweight alloys and some tall and thin tires.
Trevor Jessie

Also, remove the roof and 'screen.
Dave O'Neill 2

Yes, I reckon one of those more aerodynamic one piece front ends would make a difference. I'm not removing the screen or top though, way too draughty for my liking!

Maybe if fuel prices keep rising at this rate we'll be having 'economy challenges' instead of rolling road shoot outs!!
John Payne

talk to Pete Burgess, his Econotune heads (for Rover V8s) are/were legendary, I reckon he can apply the knowledge to the A series.
David Smith

Vizard gives a good run down in his first book "Modify Your Mini". 1275GT (with ugly square front)48MPG around town and up to 65MPG open road, and capable of 100mph. This appears to be the same car used on an around the US Run at 52.3MPG - presumably US gallons there. No slow driving and 2500 miles of city at about the mid point of about a 10,000 mile US circuit. Spridget w/ hardtop should be able to match that.

Been a guy on MGExperience Motorsports board who is building a somewhat bizarro super economidget trying for 100mpg US. Think he is using a Suzuki engine though.

FRM
FR Millmore

Irrc vizard correctley engine wise it looked like this
256 cam high cr (as posible) head with race ported exhaust ports and mild ported inlets.
Add an EFI system and i think you could improve that.

Though most gain is to be made with the driver...
Onno Könemann

A flat full front to back undertray works wonders. Not sure MR DV is correct about massive ex ports and valves. The small inlet valve head might work best on a 1275 (or 202 casting for small bore engine with slightly larger late 998 Cooper inlet valve), with probably a 'boggo' boring standard cam for greatest efficiency, remember bhp is not the aim but mpg is. The highest CR known to man( I thnik I read no detonation occurs after 17,000 rpm) Small bore ex manifold. Small 1 1/4" single su....etc etc. Throttle stop to prevent 'Big Yellow Boot' syndrome :)

Peter
P Burgess

In 'competition' with a friend and his Midget in the early 80s I can remember seeing 55 mpg driving along country lanes for a weekend break. His did around 50 mpg. We drove between 50 and 60 mph. Both cars were completely standard.

I think many with single large SU experience overall 35+ mpg. with a 5-spd box, mine was good for 45+ on a run if I stuck to 70. A BV/HC head and efficient inlet/exhaust systems benefit economy - mine was tuned for hill-climb.

It's important to make sure the mech and vac adv are working properly, and the mixture is slightly on the lean side for part throttle; make sure your brakes aren't binding; and you have 155/80 tyres at (say) 27f, 25r; if you're building an engine, go for 10:1 or slightly more compression.

With Kseries, I've bettered 50 mpg with restraint.

A
Anthony Cutler

My A series managed combined 45 mpg on a slightly ported head, twin 1 1/2s and LCB with RC40. And a heavy right foot.

When it was Icy-ish and the roads were greasy last month, I managed 71mpg in the K. Thought the fuel gauge had broken, but no, it just drove 71 miles on one gallon...
Rob Armstrong

My frogeye with 998cc , ported 12G295 head,10.5:1cr twin 11/4" Su's, piper fast road cam, LCB, RC40 etc, gave 48 hp at the wheels. would go to most Luffield events in the south, compete, and come home on one tank!. I wish I had done a proper consumption check, but I do remember coming back from Llys-y-fan hillclimb to Wiltshire in a monsoon, which limited all the M4 traffic to @60mph, and used under half a tank. 60+mpg. The car was standard all steel construction weighed 660kg, was running a 4.55 diff and 165/70 Uniroyals on Minilites.(Has anyone seen KFF528, oew red interior?, in a weak moment I swapped for Alan Haste's Sebring bodied Sprite -and I think he passed it on through Ivan Dutton? it might have gone to Japan?).
The Sebring bodied car , with 1380, 45DCOE, SCCR box, 3.9 LSD @98hp at the wheels on the other hand, did @8mpg during the Thoroughbred sportscar race at Silverstone!.
Kim Dear

On average 30 mpg (USG) is what we see with original 1275 MK-III, and standard gearbox. Given this is about the same as our B/GT with overdrive, I put this down to driving a bit more aggressively in the Midget;) Perhaps a Datsun 5-speed might improve this, but we don't drive enough (these days) to justify the cost.

Regards,

Larry C.
Larry C '69 Midget

Economy IMO depends upon efficiency of fuel usage and here there are 4 items that are extremely important.

The first being the cam design, the second being the engine RPM, thirdly the Compression ratio and finally the engine running temp.

Dealing with engine RPM first the slower the engine runs the less are the losses due to friction. However the engine needs to run fast enough to allow energy to be built up and thus run smooth. 2000 RPM always seems to me (jusyt my guess)to be an optimim figure.

Secondly the cam design. Most cams have overlaps that allow the engine to fill the cylinders with mixture at higher RPM. With total economy in mind this does not need to occur. So the cam could be made to simply ensure mixture enters the cylinder at optimum RPM (2000). (whether filling the cylinder is impotant or not I would not like to speculate?)

Thirdly the CR must be as high as practical. This ensures the fuel is made best use of. This of course is the same as tuning for power.

Finally The hotter the cylinder the better it is for efficiency. Simply stated the fuel burn does not need to waste energy warming up the combustion chamber. A few years ago engine designers (mercedes in particular) were doing lots of experiments with ceramic engines simply to allow much higher temperature to exist in the engine.

How this can work practically is I fear anyone's guess and as stated above a sticking brake or poorly inflated tyres would nullify all that hard work. :)
Bob Turbo Midget England

Some interesting ideas, I think I might have a go at it over next winter. Got most of the bits needed but I might go for a Hif38 instead of the 44. Thanks for the input Peter, we can discuss the ideal spec when I try my car out on your new road!

One thought though is that if I had a full tank of fuel, would I rather use it up getting 20mpg out of my 100bhp engine on some twisty back road or 60mpg sat at 56mph on a dual carriageway?!!

John Payne

I get 45+ with my Metro head and a 44HIF and a somewhat heavy right foot

I'm sure I COULD improve on it

And fairly certain I might soon have to
Bill 1

Way back, I seem to recall reading that optimum economy was achieved at the RPM where max torque occurs.

Open to correction of course.
Doug Plumb

As said above it can be done but why?!
I'd rather drive 20 mile like i want to than 200 like a granny.
And as we all know most of it is up to the human component.
Onno Könemann

The BEST way to get high MPG fuel economy is a ... ""5-speed trans,""

Theres just no esiaer way outside the basics... any time you can save 800 rpm for 2 hours at a time on the interstate, its going to save you some serious cash
Prop

Onno....did you see this Granny flying her Spitfire? She is Carolyn Grace....I think I read she is 58....my wife Sandra is 59 and a great granny so maybe Carolyn is a granny :)


http://www.bbc.co.uk/news/uk-england-hampshire-12656520

http://www.uk-warbirds.net/operators_grace.html


Peter
P Burgess

one idea that ive have kicked around for several years is a hybrid (Gasoline / compressed natrual gas) set up on the midget.

The more I look into CNG, the more Im a fan.

600 year supply right here in the usa to supply to power to ever current car and truck in the usa.

60 cents to $1 dollar a gallon

Its here on our soil... so we can tell the middle east to go jerk themselfs off, cause we dont need your oil.. infact if that day comes, trust me! Im a huge freaken supporter of $5000 per bussel of grain and wheat prices for our so called "Friends" in the entire middle east and the continate of africa... cause Payback is a real b*tch... you dont like it !!! grow your own or starve... I dont care!

its an easy conversion... and dosnt reqiure alot of emissions crap and much fewer parts on new cars..aka cheaper car prices

the internal combustion last much longer, due to the reduction of burning then clogging up with all that carbon... fewer repairs, you dont have to do as many engine rebuilds

the tech aready exist so no reinventing the wheel

in missour its 50 feet under ground. you can drill on monday at 8am and have a natrual gas well dug by lunch time the same day, and sell the 1st gallon the next morning.

Its clean burning

you dont have to wait 8 hours for a battry charge to drive another 60 miles so you can wait another 8 hours for an electrical charge... how insanely stupid is that concept

and yes CNG its not effiacinat as carbon based gasoline, but with gas at $4 to $6 bucks a gallon here in the usa, and CNG is 60 cents to 1 dollar a gallon... who the heck cares if you get 16 miles to the gallon with CNG compared to 20 mpg with gasoline


Im not saying everything needs to go to CNG just cars and light trucks, for 18 wheeler lorreys, heavey equippment and aircraft ect ect. , there is more then enough state side oil to power those transport vehicals

Oh thats right!!!... one last piss in the face fact for the need for CNG...

we can hold mass lynching execusions of republican leadership that want to give -- GIVE ""( GIVE "") 61 BILLION dollars to the worlds top 5 biggiest oil companys...($2030 for every man woman and child in the usa) as fun money, genorosity cash, chartiy finance, For NOTHing in return...Solely based on I like the color of your tie I want to give you $2030 dollars of my money, via the republican party... Yepp thats exactly what the republicans did just 3 weeks ago in there last budget proposal... let me say that agian... 61 BILLION dollars, With a "B"... Thank you so much MR speaker of the house John "The Thief" Bohiner...For looking out for my best interest... thats working out really well at the gas pump for me. Im so glad I supported the republicans party last fall, You thought I would have learned after 8 years of watching our "national embarresment living in the white hose" that lead our nation along with the planet to the disastor that we are suffering in today... nope not me... Im clearly the idiot in the room.

Sorry for the rant, can you tell im working on my taxes at the moment... I dont know which is worse, seeing my business cut by 70% from just 3 years ago or seeing news stories of idiots that said they wanted to make a differance at the top of governent, then realising .. yepp they sure are... now when screwing me over they use a big ol electric power driver, instead of by hand like back in the old days.

Prop
Prop

This thread was discussed between 06/03/2011 and 07/03/2011

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