928 fuel economy

[ANF]

Not that I ever expect my 928 to be that fuel efficient. With all the modern push to autos as them now being the more economical way to go, with the belief that older autos use more fuel than their manual counterparts I was somewhat surprised upon reading the factory fuel consumption figures of my 83 928 in the owners manual....

All figures l/100km

at 90 km/h            9.7 (man)      10.0 (auto)

at 120 km/h        12.8 (man)     12.6 (auto)

city conditions     19.7 (man)     18.2 (auto)

For city driving there is a large advantage for the auto, not what I would have expected at all, and this is for the 3 speed auto! I know this is according to the tests of the day, but my past experience with German fuel figures found them to be accurate.

I wonder what other P cars and cars in general are stated at/ achieve of the same era......?

[KGB]

@ANF maybe you could share your real world (well Hobart anyway..) 'fuel economy'?

My 928 GTS 4spd Auto, city driving, 50% stop-start peak hour; 19.8lt/100km atm. 

[ANF]

Will do as soon as I fix the odometer..... should be over chrissie break.

Do you know what is in your owners manual for your GTS, and auto vs man? Carsales lists 9.8 extra urban and 18.8 urban. How "spirited" is your 50% non stop-start?

[tazzieman]

Then & now , I take "factory" economy figures with a large pinch of salt. That said , my auto 928 is surprisingly economical during regular driving. Perhaps because it is a relatively light car with heaps of torque? Or perhaps because I don't sit in city traffic.

[ANF]

Then & now , I take "factory" economy figures with a large pinch of salt. That said , my auto 928 is surprisingly economical during regular driving. Perhaps because it is a relatively light car with heaps of torque? Or perhaps because I don't sit in city traffic.

You have city traffic, just a very small bit of it

The inaccurate 928 speedo would throw things out too, in the wrong direction......

 

[Buchanan Automotive]

In regards to fuel economy figures with "NEW" cars( 1970's / 1980's) , they are testing with no hills to drive up & a very constant throttle ( very smooth driving ) , meaning getting up to the constant test speed quite slowly & repeating the testing until the best ( driving ) results are recorded

New cars have a massive advantage over the same car 33 years later , the new car has new tyres & wheel bearings , the new car has new injectors , new fuel dist head ( K-Jet) , new wiring , new everything , new tyres with MAX tyre pressures at test & no fuel economy done if the ambient temp range is excessive ( up or down ) , usually done at 20 deg cel on a road surface that is known to be helpful in rolling resistance

Even the wheel alignment is adjusted to give the most efficient (least) rolling resistance

Engine , when new the compressions are perfect , where as 33 years later they will not be as good

In the 1970's & into the early 1980's , if the passengers side mirror was an option , like on the 9112.7 & 3.0SC , 928( 4.5L ) , 924 NA , the fuel economy test was carried out without the "optional mirror " , this all helps that tiny amount ( less wind resistance )

That's why  ( in the real world ) it is not easy to replicate the fuel economy figures & made a whole lot harder 33 years later

 

[symsy]

I know nothing of 928's but aren't the numbers 928 and the letters used to spell economy ..kinda a numerical /alphabetical oxymoron 

[ANF]

In regards to fuel economy figures with "NEW" cars( 1970's / 1980's) , they are testing with no hills to drive up & a very constant throttle ( very smooth driving ) , meaning getting up to the constant test speed quite slowly & repeating the testing until the best ( driving ) results are recorded

New cars have a massive advantage over the same car 33 years later , the new car has new tyres & wheel bearings , the new car has new injectors , new fuel dist head ( K-Jet) , new wiring , new everything , new tyres with MAX tyre pressures at test & no fuel economy done if the ambient temp range is excessive ( up or down ) , usually done at 20 deg cel on a road surface that is known to be helpful in rolling resistance

Even the wheel alignment is adjusted to give the most efficient (least) rolling resistance

Engine , when new the compressions are perfect , where as 33 years later they will not be as good

In the 1970's & into the early 1980's , if the passengers side mirror was an option , like on the 9112.7 & 3.0SC , 928( 4.5L ) , 924 NA , the fuel economy test was carried out without the "optional mirror " , this all helps that tiny amount ( less wind resistance )

That's why  ( in the real world ) it is not easy to replicate the fuel economy figures & made a whole lot harder 33 years later

 

I do not think it has ever been easy to replicate the published fuel economy figures, but it does give an insight of one car versus another or an auto versus a manual car. This is what my post was referring to, the fact that the published figures show a better result (for my particular car) for an automatic car over a manual car. If I can ever get close to these figures in real life is yet to be seen......

We currently use the Europe ECE (83/ 101) system which is criticised as being not achievable in the real world, but then again would give an insight as all cars are scrutinised the same way.

By a comparison my last daily driver, 1997 Mercedes E320, was able to achieve the listed figures with "normal" driving.

 

I know nothing of 928's but aren't the numbers 928 and the letters used to spell economy ..kinda a numerical /alphabetical oxymoron 

It may be my fuzzy head, but WTF?

[HH1]

I know nothing of 928's but aren't the numbers 928 and the letters used to spell economy ..kinda a numerical /alphabetical oxymoron 

What are you doing on the front engined thread? 

[Buchanan Automotive]

The three numbers 928 were simply the following }

The original 911 was the 901 ( Porsche had decided to use the number 9 as the first number to all future models ) , the 901 became the 911

Then like other Euro car makers in the early/mid 1970's the use of car model numbers will identify engine size& or number of cylinders or engine

When the Porsche 924 turned up ( mid 1970's )  the 9 = Porsche prefix , the 2 = next generation ( generation 2 ) , the 4 = (4 cylinder engine)

The same logic went into the naming the 928 , 9 = Porsche prefix , the 2 ( generation 2 ) , the 8 = ( 8 cylinder )

Volvo did the same but with more info  ,  with the 244 series in the same decade
244  = series 2 , the middle 4 = 4 cylinder , the last 4 = 4 door
264   = 2 series , middle number = 6 cylinder , the last = 4 door
242  = 2 series , middle number = 4 cylinder , last number = 2 door
245 = 2 series . middle number = 4 cylinder , last number = 5 doors ( station wagon )

Ferrari did similar to Porsche in the 1970's
308  = 3 = litre engine  & the 8 = 8 cylinders
512   = 5 litre engine  & the 12 = 12 cylinders

 

[symsy]

What are you doing on the front engined thread? 

928's the chairmans car of choice in the 80's and 90's yes.. just like Aston

Do 928 owners really worry about fuel economy ..

[GUT]

Mine uses a lot and uses it well

If you must know numbers, it's around the 19 and a bit normal driving and long trips somewhere around 12. Manual GTS.

 

[HH1]

928's the chairmans car of choice in the 80's and 90's yes.. just like Aston

Do 928 owners really worry about fuel economy ..

Fuel costs pale in comparison to smiles per mile. 928 a real man's porsche. ?

[ANF]

Yes the 928 certainly does provide a lot of smiles per $. Loving mine as a daily right now, probably uses more than my ML but don't care

[tazzieman]

Classic car /exotic drivers generally drive for the joy of driving..not just commuting. Thus economy is a secondary consideration. 

I can't claim any fuel on tax/business ; "just doing my bit for the economy"

 

[DJM]

Mine uses a lot and uses it well

If you must know numbers, it's around the 19 and a bit normal driving and long trips somewhere around 12. Manual GTS.

 

and on SMT......25+?  My oh my how will that supercharged 5.4 for sale in NZ would suck the juice.

still, got nothing on a rotary in the guzzling stakes.  Mine uses 20L - 25L per 15 minute track session.  Let's say 10 laps of 4km that's 25L per 40km or 62.5L/100km ?

Greenies look away!

[KGB]

Do 928 owners really worry about fuel economy ..

No.

Will do as soon as I fix the odometer..... should be over chrissie break.

Do you know what is in your owners manual for your GTS, and auto vs man? Carsales lists 9.8 extra urban and 18.8 urban. How "spirited" is your 50% non stop-start?

City Cycle Man 20.7. Auto 18.8

Mildly spirited stop-start. So I guess the owners manual is accurate in my case.  My commute involves 3km at 70, then the balance at 40-50-60km/h. I'd call it reasonably fuel intensive,  Perfect car for it .

[tazzieman]

 My commute involves 3km at 70, then the balance at 40-50-60km/h. 

You should try shifting into 2nd , might get some better figures 

[ANF]

No.

City Cycle Man 20.7. Auto 18.8

Mildly spirited stop-start. So I guess the owners manual is accurate in my case.  My commute involves 3km at 70, then the balance at 40-50-60km/h. I'd call it reasonably fuel intensive,  Perfect car for it .

That's not too bad

My "daily" "commute" just completed, school run, is a couple of km of twisty 60 km/h then a couple of km of suburban 40/ 50. On the way back I go the long way 90 km/h for 5 odd km then twisty 60 km/h for a few more km. Quite a fun little drive with smiles! 90km/h up a steep hill from standstill is fun and the roar....  The ML gets the short version of the trip! I would be amazed if it got less than 20l/ 100km.....

Again the auto is more economical than the manual!! Porsche ahead of the times...

[KGB]

and on SMT......25+?  My oh my how will that supercharged 5.4 for sale in NZ would suck the juice.

still, got nothing on a rotary in the guzzling stakes.  Mine uses 20L - 25L per 15 minute track session.  Let's say 10 laps of 4km that's 25L per 40km or 62.5L/100km ?

Greenies look away!

You should repair that hole in the tank.

[symsy]

Well just for comparison TT .. airport run 8.8l / 100kmh  highway max 125km.. using 6th 35 mins , fast run 26 mins probably max 185 kmh 14l/100,  latte run  21l/100km  short way .. long way by road , fast way by smile/time 28.8l/100km  oh and some tyres and brakes

We have no traffic lights.. the nearest 40 kms away

You guys got nothing to worry about!.. 

Fossil fuels ..used in style are never a waste. 

[KGB]

Well just for comparison TT ..

[stuartbrs]

I dont have any figures to back this up, but when I swapped from Tazziemans 81S to my current 928 S4 manual, the later manual car was a LOT better on fuel. 

Now that I work just up the road, its even better still  

[tazzieman]

I dont have any figures to back this up, but when I swapped from Tazziemans 81S to my current 928 S4 manual, the later manual car was a LOT better on fuel. 

You've just matured a bit  OTOH I am regressing

[KGB]

I dont have any figures to back this up  

It's a feeling?