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Gatornapper · Joined: 23 Oct 2021 Posts: 294 Location: VA

Ok, just got an idea of what my gas mileage is - my odometer is still broken.

Using my phone to track my mileage, I did a short test of 115 miles intentionally trying to stay out of the turbo. A disappointing 17.5 mpg.

I noticed that when I was enjoying the turbo, my mileage had to be horrible. Thus my test.

So what is the norm here for the 931 crowd? ok, not a crowd. What is normal for trying to keep out of the turbo? And what is normal when using the turbo about half the time?

Last question: HOW do I keep from it going into turbo mode? I try to accelerate slowly and shift at 3,000rpm. Any tips?

On the other side, what is it that kicks in the turbo? It doesn't kick in to about 3,500 rpm, right?

TIA,

GN
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'87 944 S, looks & runs like new - sold my sweet 931; '76 914 2.0 mostly restored; 2011 Porsche Cayman S in Meteor Grey, 3.4L, Softronics ECU tune 355+hp , PDK w/Sport Chrono. Got this thing for Porsche's.......

chuck21401 · Joined: 20 Feb 2005 Posts: 526 Location: Annapolis, MD

Carrera RSR · Joined: 08 Jan 2010 Posts: 2309 Location: Somerset, UK

Wrong car for any thoughts on good gas mileage……if you’re considering this, buy a Prius

At best I get 20 UK mpg’s so that’s 250 miles at the very best out of a 50l tank. Usually far less on both counts. If it ain’t boosting, it ain’t worth driving.
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1980 931 - forged pistons, Piper cam, K27/26 3257 6.10 hybrid turbo, 951 FMIC, custom intake, Mittelmotor dizzy & cam pulley, H&S exhaust, GAZ Gold, Fuch'ed, Quaife
Now www.924board.org/viewtopic.php?t=34690
Then www.924board.org/viewtopic.php?t=31252

Gatornapper · Joined: 23 Oct 2021 Posts: 294 Location: VA

Gatornapper · Joined: 23 Oct 2021 Posts: 294 Location: VA

Not my goal - it's the right car for driving fun! Only new gas prices are going to make it a lot more expensive.

I was sensing that when I was enjoying the turbo, it was in the 10 mpg range - slurping gas fast.

Just wanted to know what a baseline was and if there was some adjustment I needed to make to something.

Thanks!

GN

Gatornapper · Joined: 23 Oct 2021 Posts: 294 Location: VA

You all use Regular gas or Premium?

I've been using Premium.

Can I use regular? I didn't know if the boost from the turbo required it - have seen nothing in manual or on car about needing premium........

GN
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'87 944 S, looks & runs like new - sold my sweet 931; '76 914 2.0 mostly restored; 2011 Porsche Cayman S in Meteor Grey, 3.4L, Softronics ECU tune 355+hp , PDK w/Sport Chrono. Got this thing for Porsche's.......

Carrera RSR · Joined: 08 Jan 2010 Posts: 2309 Location: Somerset, UK

Fasteddie313 · Joined: 29 Sep 2013 Posts: 2596 Location: MI

I felt I was getting excellent gas mileage highway flying but it was super thirsty being used as a DD for short errands..

Thing would just DRINK fuel boosting around town but high speed cruise all day long quite efficiently..
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80 Turbo - Slightly Modified

Cedric · Joined: 27 Aug 2004 Posts: 2608 Location: Sweden

IF your fuelling is of it doesnt matter how you drive, but yours should be lambda controlled on part load since its a us car, if it still works.

Normallt these cars (and many turbo cars, especially older ones) enrich the mixture quite alot at high load, hence its a good idea to noot boost it. They should be pretty good at just cruising, but i havent done that type of driving in any prolonged period of time in many years. But fast highway driving was around 25mpg if i remember correctly, though mine is euro s2 with 8,5CR, the compression ratio makes a significant different at part load fuel efficiency. According to the manual the euro s2 should do 27.4MPG at 74.5miles/hour, that would need the standard s2 turbo though, it definitely got a bit worse when i went up a size. I cant find any official numbers for the US version, it should be a bit worse though.

On track its about 3l/100km or 7.8MPG, will be nice now when fuel is at 2.2euro/litre

Do you have any vacuum leaks? clogged cat? Hows the status on the fuelling?
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1980 924 Turbo
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morghen · Joined: 21 Jan 2005 Posts: 8880 Location: Romania

Used to get around 29mpg on my 951 bumpered 924 turbo S2 cruising around 75mph. My S1 931 did similarly, a bit worse due to worse aero...maybe 26?

My supercharged 924 does around 23mpg but the driving conditions are different now, i mainly did 85 on highways and i did a lot of mountain climbs with it...also..shorter gears of the NA, not as good aero and obviously the supercharger make up the difference...and except maybe carbs, there is no worse setup for mileage than short gears and supercharged.
Your 17.5 mpg result is clearly pointing that there is something wrong with your car.

EDIT fuel price here is:
1.8 eur / liter
that is 2.7AUD / liter or 7.3 USD / US gallon
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peterld · Posted: Mon Mar 14, 2022 10:01 pm Post subject:

+1 to Morghen above.

ROW S2 with 6.10 turbo and 8.5 CR easily achieved 30+ mpg cruising at 110kph

Race car with hybrid turbo/7.5CR/enriched fuelling barely achieves 8mpg.

Fuel prices in Oz: 98 RON $2.89 litre/94 RON E10 $2.29 litre
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80/81 932/8 ROW

924RACR · Posted: Tue Mar 15, 2022 12:02 am Post subject:

Funny to see the Turbos getting such mileage on track; with our old NA 924 (relatively mild engine build) we only get about 7mpg on track!

OTOH, my prototype, which is unbelievably faster, gets around 11-12mpg on track with it's little 1.0L GSXR motor!

Of course, while the 924 NA runs on ordinary 93 octane pump gas (R+M/2 method for the rest of the world!), at approaching $5/gal here in MI I think, the Gixxer needs to be fed a diet of 100 octane race gas, which was $10 USD/gal last summer when gas was cheap!

It's all relative...

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Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

Cedric · Joined: 27 Aug 2004 Posts: 2608 Location: Sweden

Fifty50Plus · Posted: Tue Mar 15, 2022 3:05 am Post subject:

6-8 MPG has been the norm for all my race cars (at 12.8 CO), the difference probably being better aero on some body shapes (356, 911, 924, 2002, Benz, VW).
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1979 924 NA race car
1982 924 NA race car - Sold
1982 924 Turbo almost a PoS
1981 924 Turbo a real PoS, new engine
1982 924 Turbo nice body, blown engine
1972 911 E race car - going to Vintage
Various 944s to become IT-S race car

Gatornapper · Joined: 23 Oct 2021 Posts: 294 Location: VA

Thanks all......my local driving is 50/50 hwy/suburbs.

Gonna do a highway trip tomorrow and will check hwy mileage.

After that I'll do a boosty run in the twisties where I live and check that.

As far as I know no vacuum leaks, all Haynes tests of CIS were spot on, engine could not run better it seems to me. Injectors are new. Purrs at idle, starts instantly regardless of ambient temp, turbo kicks in nicely around 3k rpm. A hoot to drive tho it doesn't corner as flat as my '76 914 which has no sway bars. Gonna replace sway bar bushings soon with hi-perform ones.

GN
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'87 944 S, looks & runs like new - sold my sweet 931; '76 914 2.0 mostly restored; 2011 Porsche Cayman S in Meteor Grey, 3.4L, Softronics ECU tune 355+hp , PDK w/Sport Chrono. Got this thing for Porsche's.......