Going to look at a fantastic 1973 911S tomorrow. Need a bit of advice.

[sithot]

?55MPH?

MFI was NEVER known for fuel economy.

Road tests from C&D 1972 verify this fact.
16-20mpg on a T, 15-18mpg on an E and 14-17mpg on an S.

[911MRP]

...To complete the when new MFI input 73 Carrera RS M472 vs some top end of market sporting comparators with larger ( some 2x) engine marques was the least thirsty over a test distance and required only two star Petrol. Daytona (which cost roughly price of a new etype jag on top of RS tourings retail price ) only beat it when above “real world” Road performance bracket. All are from same weekly magazine testing protocols using measurements and calibrated equipment for speed. Note: being British article I assume Imperial gallons. One imperial gallon is equivalent to approximately 1.2 U.S. liquid gallons.

By way of comparison to prior year 2.4S 1972 the smaller capacity car was comparatively thirsty (vs 2.7) with overall 13.3 imperial mpg over roughly 2000 mile test distance With 2.4 being slower eg acceleration 0-60mph 6.2 sec (vs 5.5 sec); 0-100mph 17. 1sec (vs 15 sec) acceleration benchmarks along with the worse average mpg also on two star.

The 2.4 litre compares pretty favourably to several of these bigger engine cars in terms of the often quoted to 60 mph acceleration benchmark and average mpg

Steve

*The Lamborghini Although no longer on sale by 1973 it had retailed around £9600 in 1971 before any options etc

[LongRanger]

. . . some other threades . . .

https://www.early911sregistry.org/fo...umption-on-MFI

https://www.early911sregistry.org/fo...ur-gas-mileage



.......................

[911MRP]

Buried in the narrative they say this about consumption over a total of 2600 miles when they had nearly new press demonstrator at their disposal..including a brief comparison to similar consumption from a 2.4E they’d previously tested with 0-60 benchmark of one seconds slower and 11 mph lower top speed.



Many things have changed since 73 but this report gives a perspective on what was considered moderate consumption for a MFI car with a high level of performance from a mere 2.7 back in those carefree days Just before looming oil crisis.

Incidentally my car history papers has some unused old UK fuel rationing books tucked away which I assume must be left overs from the oil crisis of 73 that kicked off when car was just a few months old.

Steve

PS Totally by coincidence I came across this little table tonight whilst clearing my desk so posting it for information to put the 72/3 911 and the other top end sports car mpg figures in context of a mixed bag of cars the editor of a magazine tested in 1972. No big point in doing so other than the obvious point it illustrates the 911 wasn’t for people worried about fuel economy probably many company owners, professionals or of independent means — although interestingly a ford for upper middle management had similar mpg (17) although that Granada would’ve been a company car employment perk typical 3 year lease with fuel account in those days here in UK Probably little regard for economy either. Some cars however were quite frugal even before oil crisis and early environmental considerations in some regions forced car makers to look at more closely mid 70s. I suspect the ford cortina was among if not the actual best selling car here at that time.

[NorthernThrux]

Not complaining about mpg. For the amount I drive, it's just about the cheapest thing about owning this car

Remember, while I may have a 2.4S, it is producing 212 hp and the lean mid-rpm mid-throttle part of the space cam has been plumped up so it isn't running the stock 16:1 AFR there, which we think Porsche did for emissions purposes to get the S certified in the US. So anything above 13 mpg is a gift on Sunday drives. Especially since I run 87 octane regular, which around here is 10% ethanol typically and reduces the specific energy content of the gas. That's what the car was setup for and tested on the dyno with.

The irony is that my 3 litre V-6 twin turbo 4300 lb Porsche Macan S with a 400 hp Cobb tune gets 20 mpg in mixed driving, albeit on 91 octane. EFI has come a long way from MFI. I see about 24-25 mpg on the highway at legal(ish) speeds. It is a bit surprising, because MFI was very much the most excellent way to atomize fuel and should have allowed some degree of lean burn, but I guess things were just too crude. My 2 litre 1980 Saab 900 turbo, which had Bosch CIS with an O2 sensor was around 24 mpg in mixed driving, so you can see the progress through the ages.

The extended idling wasn't intentional. It just happened to take me a long time to get the Macan onto the lift and up in the air. Really wish I had built a 3 bay garage. Usually, with any EFI car, I start, wait 30 s for the high idle to drop and pull away. 30 s with the MFI car as well.

Ravi

[terry911t]

Ravi,
Find a non ethanol fuel for your car. I use the REALGAS app on my phone when driving outside my home base. Depending on the octane of the non ethanol, I may add some race fuel(110 octane) to the non ethanol. I have a local spot that has 90 octane non ethanol. I have cleaned my last carb on my mowers, trimmers and old cars. Hate ethanol. Avoid at all costs.
Enjoyed your thread over the years. Nice to see you getting seat time. Drive it like you stole it!

[NorthernThrux]

I also use nonethanol in my snow blower and pressure washer. Switched to electric everything else years ago. However, Robert and others told me that starting can be an issue with higher octane gas, almost by definition. 91 octane here is ethanol free at any of the brand stations, so that’s not hard to find. Of course premium does come a a significant price bump here too. I may try mixing in premium each time I get down to a half tank and see if the gradual increase in octane makes a difference. So far, warm and cold starts are a breeze.

Robert was not concerned about ethanol, and given his 35 years of experience with 356s and 911s, I wasn’t going to question him despite my own bias against ethanol. His philosophy was always to tune for the worst possible gasoline, because you never know what is available in the sticks. Worth playing around with like you say once I have established all the normal operating parameters. I noticed on my first fillup that the odometer doesn’t reset, so that’s a winter project to put on the list. That makes carrying a notebook to keep mpg notes more important.

[Arne]

Ravi, I'm in pretty much the same fuel boat as you are. Non-ethanol regular fuel is almost impossible to find around here. There is something like 3-4 stations in the entire state of Oregon that sell non-ethanol regular. And my '72T with even lower compression than your S (7.5:1) doesn't run particularly well on high octane. It's hard to start (especially cold) and doesn't seem to run well in general. The exhaust is rather smelly with premium, which makes me suspect poor combustion.

Remember that even the "Check, Measure, Adjust" document warns against poor combustion in the 2.4s with high octane fuel. So I use regular with ethanol. In my car's case (like yours also, I suspect), everything is pretty much new, so there isn't much there that ethanol can degrade now. I do use fuel stabilizer if the car is going to sit unused for any period of time.

[frederik]

This is interesting, I run 98 octane fuel from BP or Shell here since it's the only stuff guaranteed to be ethanol-free. No issues running or starting. But it's very likely we tuned it for this fuel type (which is easily available in Europe). EU fuel ratings are not the same as in the US though, 98 EU apparently means 93 in the US (https://www.etuners.gr/fuel/).

The lowest fuel type here is 95 RON or E10, which is 91 MON (US). But that nowadays contains 10% ethanol.

[HughH]

I also run 98 (RON) octane from BP here in Australia in my "2.4" E although it has a 2.7 RS spec engine, (never SHELL as their fuel is supposed to have too much "clay" in it here in Australia which is not good for MFI). Again 95 and 98 here are guaranteed to not contain ethanol which I understand is a risk factor for fuel lines and some other parts of the fuel system that the ethanol can react with on old cars built well before its use was contemplated.
I don't have any running or starting issues with it and have been advised (because I have a big 85L tank and don't therefore fill up often) that the higher octane is actually better as the octane rating deteriorates over time - certainly over a period greater than a couple of months which is a normal minimum period for my refills most of the time.