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MG MGA - What's Your Fuel Consumption?

What does your MGA do to the gallon? I,ve been keeping tabs on my 1500 A's fuel consumption just lately and don't seem to get any better than 22.5 miles per gallon. I haven't got dragging brakes, all wheels spin freely, I,ve overhauled the engine; not a rebore or crank grind, but new camshaft, valves, springs etc. I've overhauled the carbs, balanced and adjusted them to the book. Ignition timing is set to 7 degrees static; i've tried advancing up to 30 degrees at 3000rpm but I didn't like the way it ran at all at that setting or anything approaching it so I set it back to the book setting and it seems much sweeter. The distributor is a brand new one from Moss Europe. The car seems to run nicely and is fast when it gets there although the acceleration is not exactly blistering, but maybe modern cars have spoiled me! I am sure I got into the thirties fuel consumption wise with my '55 Magnette, a much heavier car. So is this normal, have I got a fault somewhere or just too heavy a right foot!
Lindsay Sampford

Lindsay,
With my 1500 I get around 25-26 mpg in town and 30-32 on the highway. This engine has 8.5 to 1 compression, standard ignition specs, stock distributor and intake/exhaust port matching/polishing. I normally don't go above 4000 rpm when shifting. This mileage is pretty much what I've come to expect after 40 years of MGAing. As is often stated "your results might vary".
Cheers,
Gerry
G T Foster

Sounds a bit low Lindsay, there's loads of stuff on this in the archives.

Obviously MPG depends on driving style and traffic conditions. On a steady run country roads little traffic, around 40-60+mph one should be getting mid to high thirties. 70+mph motorway (1500-hope not) or stop start town driving might bring the figures back down to where you are now.
Neil McGurk

I agree with Neil - mine never goes below 30 mpg (1600 standard) and usually around 35. cheers Cam
Cam Cunningham

Lindsay

That's less than what I get with a Supercharger and a lead foot. The carb on the Judson is best described as agricultural (it was also used on some International Harvester trucks and Mustangs, 'nuff said...)

Unless you drive like a maniac, you should get much better than that.

It's probably running too rich, which may explain the poor acceleration too.
dominic clancy

Thanks for that folks, at least I now know I am looking for a fault. Just been out to check the mixtures (with the lifting pins). Back carb was too rich by one flat; was spot on last time I checked it. Would that make much difference to mpg?
Lindsay Sampford

Gerry, I assume you are referring to US gallons. That would translate to 30-31 in town and 36-38 on the highway over here!

Lindsay, one flat on one carb should not make much difference. Did you check the plugs? How about the colour of the tailpipe? Is there much of a petrol smell?

Neil McGurk

I get 35MPG out of my 1600 fuelled by a dcoe. :-))

Well when touring anyway, that is 75MPH on the main roads and 30 to 50 on touring routes.

I think your problem Lindsey relates to why you can not set the timing correctly I need mine set at 32 degrees max mech advance with correct operation of the vac advance which helps enormously with MPG.
Robert (Bob) Midget Turbo

Robert, I tried setting the ignition dynamically at 32 degrees full advance with the engine running 3000rpm using a Snap On computerised timing light (frightened the life out of the wife with her foot on the throttle.....go on, give it some more, it's not going to blow up!). I had to turn the tickover screws right down to get a reasonable idle, and once it got really warmed up, the tickover became erratic. In the end I got fed up with it and went back to the book setting, whereupon it seemed to run much nicer all round.

Neil, after a normal run ending in a few seconds tickover the outside edge of the plug is dark grey, the insulator is clean and white and the electrodes are a lighter grey. Inside the tailpipe is black, which I thought was normal for unleaded, I haven't seen that nice grey colour in a tailpipe since they took the lead out of the petrol. At tickover the exhaust note is light and even with no misses.

Having had the engine right apart, it seemed to me that it probably hadn't done many miles since a re-bore and new pistons as the pistons looked brand new with no staining. The cylinders, however, had what looked like rust staining on them. I wonder if a previous owner had it re-bored, did about 100 miles in it then it stood for ten years or more. When I got the car from the PO it had only got 300 miles on the odometer, and as the car drove like a pig, he had not done many miles in it. It is now just coming up on 4000 miles, so it may be that it is still a bit tight. It just doesn't seem in a hurry to go faster but gets there in its own time. At 70+ it is as sweet as a nut and has got plenty more in reserve, but if you try to gun it through the gears to get there, it doesn't want to play, it is happier if you just put your foot down in top gear and wait! So maybe this is connected with the poor fuel consumption. I have looked back through the archives, and as Neil says, there is loads of stuff on this subject, but I did notice that a lot of other people were only getting 20-22 mpg so I am wondering now!
Lindsay Sampford

I have kept a regular spreadsheet on fuel consumption and over the last 5000 miles my Mk 2 Coupe has averaged 25.61 mpg (UK gallons) however on long runs I get between30-35 mpg and around town and "testing" as low as 22-25mpg
my two pennorth
Paul
P D Camp

Good morning Paul, I'm fast coming to the conclusion that it's not how many miles you do but the way you do them! There seems to be a big difference between town driving and long runs. I have monitored the last three tank fills; about 400 miles, and probably half of that has involved round trips of not more than 10-15 miles but no slow moving traffic and 50-60 mph on the open road. As far as I can tell, everything is set the way it should be and there are no leaks or flooding. Aside from the slightly dissapointing acceleration, the car runs very sweetly. The only thing I can't be 100% certain of are the characteristics of the distributor advance mechanism (new Moss EU unit).
Lindsay Sampford

Lindsay

Mine (1800 engine) will do over 30 on long runs. However, on my every day short commutes of 4 miles each way I was getting 22.5 ish like you. I now commute 8.5 miles each way and my consumption first went up to 25.5. I then changed to a chinese dizzy and it is now 28.5. I expect mid thirties on a long run.

Just to be contoversial, I believe a lot of people exaggerate their mpg. It is only when you keep a spreadsheet over a year or 2 that I think you can be qualified to quote average mpgs. We can all do the occasional long journey and make all sorts of claims, but it is the average of all the short (less than about 5 miles) journies also that go to make up the true figure. I have had my spreadsheet going for about 2.5 years now and can quote you to 2 decimal places on average and individual tankloads. Believe me, the difference can be astronomic.

Steve

Steve
Steve Gyles

Just in case anyone on this side of the pond is wondering how those Limeys get such great mileage...
1 gallon (UK) = 1.200949926 gallon (US)
Cheers. Safety fast.
J Rogers

I can't believe there are so many odometers still working!!!!
SAC Scott Curtis

Good Morning Lindsay
I think there is a clue in your relative poor acceleration -timing or carbs not quite right.I spent quite some time getting my timing correct and making sure the S Us were correctly tuned.I have a 25d Dizzy which I am contemplating changing to the 123 electronic system ( I had one o my B which was excellent)
My 1622 engine was rebuilt some 10000 miles ago with a slightly skimmed head giving 9.5 cr and a mildly tuned cam( at least according to the spec sheet from the pevious owner) and now runs very sweetly.I also have fitted the Hi Gear 5 speed conversion.The acceleration is good and will cruise easily at 70/80 @ 3000-4000rpm.Sluggish accelaration will I suspect drink petrol as you have the throttles wide open
Paul


P D Camp

Lindsay-
The combination of apparent good running, poor acel, and low gas mileage is characteristic of late cam timing.
Following is from earlier post I made on another board.
Do the quick timing check described in a nearby thread.

On a Spitfire 1500 that had never been apart, I found that the cam was timed about 9deg late, from the factory, plus about 5deg for chain wear - total 14deg late. The Triumph design lets you set cam timing wherever you want by switching the cam gear position around - no new parts needed. This engine was removed due to a strange problem at about 60,000 miles, not for wear or any apparent deficiencies - it had a loose bolt (not) securing the rear engine plate that backed out and locked against the flywheel, due to the factory having left off the lockwashers that are supposed to be fitted to those bolts. The engine had obviously been very well maintained. Mains and rods were clearly due but OK, TW were worn but not about to fallout. Crank was polished and was in spec for new, refitted with new bearings and TW clearance set at minimum. The cam was bad (just, as opposed to scrap), reground to stock and refitted with new lifters. Rings and bores were as new, and were refitted. Valves & seats took the slightest cleanup cuts, more miles and it would have needed new valves and possibly seats. The cam was timed in exactly, to 2 deg advanced as I always set them with a new chain. No changes whatsoever were made to spark timing (set to where it was on disassembly), carb adjustments, etc. Fuel mileage jumped from about 28 to 32, and I estimate about 10hp increase, based on notably better performance. On a stock 1500, you have about 10hp available for acceleration, hill climbing, etc., so a 10hp increase is a doubling of "free and usable" power, and it would cost several hundred dollars to achieve this via mods. The customer was frightened by the change and demanded to know what "hot-rod" tricks I had employed.

FRM
FR Millmore

Steve,
What carbs do you run on your 1800 cc? Just about to drop one in my A and what to fuel it properly.
Chris Velardi

Chris,

I get 31mpg Hwy, 26mpg City (USGal) with MGA H4 carbs on my 1800. #5 needles.
Jim Ferguson

Chris

Like Jim, I run the MGA carbs. I also have the original needles (GS?). Seemed to tune up okay. However, I have never had what I would call a brilliant MPG so I have often wondered if fitting different needles like Jim would make a difference. Once I have done a few more tankfuls with my new dizzy, I may swap over and do a comparison.

Steve
Steve Gyles

To be honest , I'm not as concerned about economy as performance. I just had Fab Tec
http://www.fast-mg.com/
build up a new 1800 engine for my A with performance upgrades and I want to make sure I feed it properly.
Chris Velardi

FRM, thank you for your post on valve timing and its association with performance and fuel consumption. I checked it as per the book, i.e. 60 thou on number one inlet and rotate the engine til all the clearance gone. I really thought I was on to something as I have just replaced the camshaft with a new one and it could have been possible that the keyway had been ground in the wrong place. Sadly though, I only found the valve timing about 2 degrees late (with a used chain), which would appear from the thread on valve timing, to be "within limits". Am I right in this assumption or would that 2 degrees make a difference worth correcting?
Lindsay.
Lindsay Sampford



83.99 MPG in my MGB GT. I think I could manage similar in an MGA as it has 15" wheels.

However I did build a 3 cylinder MGB engine with MGA head with single valve springs and single 1 1/4 carb.

I tried a 2 cylinder the next year, but did not manage to better my results, due to SU needle and seat failure... Too much engine vibration.

After the MGCC event the race engine went back in and MPG went south once more.

Cheers
Mark.
Mark Hester

Well I guess you'd be an expert on "going south" Mark!
Lindsay Sampford

Just to combat the assertion that my MPG claim is seen thro' rose coloured specs. I have been using Steve G's excellent spread sheet for just about 12 months now ( thanks Steve!) - my petrol overall has been hovering around 50Km per gallon (which is around 32MPG I think, assuming my odometer is correct ) - although it has dropped to 46KPG recently as the front carb is weeping a bit - must get round to looking at it before it bursts into flames!! cheers Cam
Cam Cunningham

Is the UK still selling 100% gasoline? Most all the fuel around the Chicago area is 10% ethanol and has been for years.

My car is a std 1500 with nothing special done to it. it was rebuilt about 11,000 miles ago to basically std specs. I think .020 over bore and a std cam grind. I generally get around 26-27 MPG (USA) with casual rural driving and a passenger. Not highway, but also not stop and go commuter driving. This is not a scientific or long term study. I have gotten as high as 28 MPG on cross country highway driving 2 people doing 70 MPH, top down, with a large storage bag strapped to the luggage rack and a boot full of spares and tools. This is not very aerodynamic nor is it an ideal speed for good mileage. I know I can do better, I just never tried.

Using the 26 mpg as a base and making a few adjustments to my mileage as follows:

USA vs UK gallons: +20% = 31.2 mpg
Gasahol vs 100% gas: +3.5% = 32.3 mpg
Miles vs Kilometers: +61% = 52 kpg

This seems to be in line with most, and not as good as some.

Chuck
Chuck Schaefer

My stock MK11 is getting an average of 28 MPG, varies + - depending on how driven:) the 58 with the Mazda rotary gets about 10 :( ,but it is a wee bit faster.
R J Brown

Lindsay-
2deg should not make as notable a drop off as you seem to have, though it might help to advance the cam by another two - ie 4 advanced from where it is. Enough to notice in driving.
However, note that if the new cam is not "exactly" as the OE spec, then all bets are off. You should have a timing card with the new cam, which will enable you to do a full timing check to sort it. If you do not have the card, then you get to do a full cam event measurement and calculate the appropriate timing.
If the new cam has a little more duration and/or a little more lift than OE spec, it would pass the simple check whilst still being substantially retarded. I always check at least one inlet and one exhaust for overall timing, even when a new/RG cam is said to be "stock". And, I then at least check that #4 is timed the same as #1, since it only takes another revolution of the crank to do it. Cam grinders are known to be unreliable on indexing! Vizard cites some rather amazing cases he has encountered.
As you can see, the Spitfire was 14+2 degrees advanced from earlier when I reassembled it, netting around 15% in fuel consumption and power. The big killer seems to be late closing of both inlet and exhaust, which would be even worse if your new cam has more duration and/or lift. Closing would be delayed due to the later opening and doubled by the cam event difference.

FRM
FR Millmore

This thread was discussed between 22/06/2009 and 02/07/2009

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