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931 Gas Mileage???
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Gatornapper  



Joined: 23 Oct 2021
Posts: 292
Location: VA

PostPosted: Tue Mar 15, 2022 11:40 am    Post subject: Reply with quote

Cedric wrote:
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 Think I'm getting about that when I am on turbo a lot......

Do you have any vacuum leaks? clogged cat? Hows the status on the fuelling?
Cat seems clear - great exhaust flow - and is not original - car has about 60k mis. on it so I'm guessing cat is low on mileage. It's coming out after I do a bunch of other stuff.
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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.......
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Gatornapper  



Joined: 23 Oct 2021
Posts: 292
Location: VA

PostPosted: Tue Mar 15, 2022 11:40 am    Post subject: Reply with quote

So how do I test the Lambda system and see if it is working?

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.......
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Gatornapper  



Joined: 23 Oct 2021
Posts: 292
Location: VA

PostPosted: Wed Mar 16, 2022 11:03 pm    Post subject: Reply with quote

Wooo Hooo!

26 mpg yesterday on the interstate!

And that includes about 20 miles of showing my NC friend how much fun the turbo is in full boost! "THAT'S ENOUGH!" he said - more than once.

Rest of trip was 70 - 74 mph according to GPS - my speedo reads 5 mph high with 195/65R15 tires. That will be replaced with 205/60R15's soon.

So would all agree my engine has to be tuned pretty well?

I do think the boost could be improved a bit - but won't know for sure until I get a gauge installed......

GN


[quote="Gatornapper"]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.......
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Mike9311  



Joined: 14 Dec 2004
Posts: 1390
Location: Chicago-ish

PostPosted: Sat Mar 26, 2022 3:39 am    Post subject: Reply with quote

Your last post here is more my experience. You should also notice an improvement in cornering when switching to the 205's
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1980 931 since 1989
1981 Ideola 931 Club Sport
1982 931 Entwicklungsfahrzeug
1979 924 NA ohne 650 mit 471
1982 931 Red Resurrection - 951 IC
1982 931 parts car / resurrection?
1980 924 NA (R&D lightweight)
1982 931 wana-be GTR race car
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Gatornapper  



Joined: 23 Oct 2021
Posts: 292
Location: VA

PostPosted: Mon Apr 18, 2022 10:34 pm    Post subject: Reply with quote

Got 26.3mpg again on a trip of 65+ mph on Sat. the 9th - very pleased.

Also seemed to have located and stopped most of the oil leaks - yay!

And yes, the new Riken Raptor 205's are just wonderful in the corners now. What also is a major difference is new front tie-rod ends and alignment.

Honestly, car rides and handles like both a new car and a modern car. Comfy, great ride, great handling, nice power - it's got it all. And nice looking too now with all the dents removed.

I'm amazed. Had no idea this 931 could be SO SWEET!

GN

Mike9311 wrote:
Your last post here is more my experience. You should also notice an improvement in cornering when switching to the 205's

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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.......
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peterld  



Joined: 10 Dec 2006
Posts: 922
Location: Noosa Heads QLD Australia

PostPosted: Tue Apr 19, 2022 12:37 am    Post subject: Reply with quote

Spread the love!!
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Fasteddie313  



Joined: 29 Sep 2013
Posts: 2596
Location: MI

PostPosted: Wed Apr 20, 2022 6:52 am    Post subject: Reply with quote

I love the 931 on the highway!
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Gatornapper  



Joined: 23 Oct 2021
Posts: 292
Location: VA

PostPosted: Wed Apr 20, 2022 10:28 pm    Post subject: Reply with quote

Eddie -

SO DO I!

Yesterday drove it almost 4 hours on interstate down to Newport News, VA and back, then 50/50 interstate & 2-lane Hwy 522 to Lake Anna and back another 2 1/2 hours in late afternoon.

Great highway car - just miss cruise control - and great car on 55mph country roads too.

Nary a problem and about 24 mpg.

Got my odometer repaired. Yay.

GN

Fasteddie313 wrote:
I love the 931 on the highway!

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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.......
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