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Dutch924-racer
Joined: 23 Jul 2007 Posts: 1077 Location: The Netherlands
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Posted: Sat Apr 22, 2017 4:10 pm Post subject: What are the AFR ratio's you want for a 931 ? |
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My 931 (series 2) engine rebuild is finished I am now adjusting the mixture.
I have a Innovate wideband sensor/ gauge.
What are the AFR ratio's I want to aim for at:
idle
cruise
full throttle/boost _________________ 937 trackday car
Series 2 engine
951S turbo and intercooler
Fast road camshaft
Forge recirculation valve + boost controller |
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Cedric
Joined: 27 Aug 2004 Posts: 2614 Location: Sweden
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Posted: Sat Apr 22, 2017 5:25 pm Post subject: |
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I would start out with 14.7 at cruise and 11 at wot, should be a good start, thats how my cis is setup. _________________ 1980 924 Turbo
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ideola
Joined: 01 Oct 2004 Posts: 15548 Location: Spring Lake MI
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Posted: Sat Apr 22, 2017 10:34 pm Post subject: |
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I have two 931s with wideband AFR. One is with S1 CIS/ignition, and one is with Euro S2 CIS/ignition.
Get the car fully warmed up, to the point that your OIL TEMP is at operating range. Then go through the full regimen to set mixture and idle speed. Use the wideband gauge to get the mixture at 14.7:1 at proper idle speed on a fully warmed up engine.
On both of my cars, I get very steady idle + 14.7:1 AFR, and this results in proper cruise AFR, somewhere between 14:1 - 15:1, with WOT / full boost AFR in the 10:1 range. In my case, the WOT AFR may end up being richer than Cedric's because both cars are running higher-than-stock boost levels. _________________ erstwhile owner of just about every 924 variant ever made |
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morghen
Joined: 21 Jan 2005 Posts: 8884 Location: Romania
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Posted: Sun Apr 23, 2017 7:34 am Post subject: |
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I keep mine at 13.5 AFR at idle, 11AFR at full pedal and boost. _________________ https://www.the924.com |
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Carrera RSR
Joined: 08 Jan 2010 Posts: 2309 Location: Somerset, UK
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Posted: Sun Apr 23, 2017 7:33 pm Post subject: |
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A stock WUR is extremely difficult to tune to ensure the best AFR's across the throttle and rev range. Many owners will report differing results. 14.7 is your target for idle and cruise. At wot, 10's is safest for non IC'd turbos. 11's is safe for intercooled turbos. Low 12's if you feel brave.
The one to watch with our cars is the mid range boost enrichment. Our wurs are set up for non IC. Therefore over enrichening the mixture as soon as boost kicks in regardless of throttle position. So sapping power and wasting fuel as you accelerate at semi or full wot and full boost. Hence the 'Brian Leask' type solution which many 930 guys on their modified cars. _________________ 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
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ideola
Joined: 01 Oct 2004 Posts: 15548 Location: Spring Lake MI
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Posted: Sun Apr 23, 2017 10:27 pm Post subject: |
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Carrera RSR wrote: | At wot, 10's is safest for non IC'd turbos. 11's is safe for intercooled turbos. |
Good point...
Worth mentioning that the two cars I cited are both intercooled: the 80 S1 (941) has progressive water-meth injection that starts sparying at 5PSI with progressive (linear) increase up to full boost (@ 12PSI). The 81 Euro S2 (Club Sport), of course, has many modifications, and is also running my TMCC (liquid to air intercooler). _________________ erstwhile owner of just about every 924 variant ever made |
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Dutch924-racer
Joined: 23 Jul 2007 Posts: 1077 Location: The Netherlands
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Posted: Mon Apr 24, 2017 3:50 am Post subject: |
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My gauge at cruise before adjustment reads about 18-22.
I turned it richer but the car began to smoke, so turned it leaner again. After a test drive the spark plug looks very black and a bit wet. So still to rich.
I turned it leaner agian and now it reads about 13.5/14 at idle but the strang thing at cruise still around 16/17. On boost it drops to 12-14.
I don't understand it now anymore. The Innovate kit is just about 200 miles old and was recenlty calibrated.
If I go of the gass, the exhaust makes a popping noise.The exhaust is straight through sport system, so maybe it is normal.
My sparkplug (W-3-DPO Bosch platinum) looks now like this now:
_________________ 937 trackday car
Series 2 engine
951S turbo and intercooler
Fast road camshaft
Forge recirculation valve + boost controller |
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Carrera RSR
Joined: 08 Jan 2010 Posts: 2309 Location: Somerset, UK
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Posted: Mon Apr 24, 2017 7:04 am Post subject: |
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What are you turning ? _________________ 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
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Dutch924-racer
Joined: 23 Jul 2007 Posts: 1077 Location: The Netherlands
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Posted: Mon Apr 24, 2017 3:55 pm Post subject: |
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the mixture screw on the mass air flow meter (3mm allen key) _________________ 937 trackday car
Series 2 engine
951S turbo and intercooler
Fast road camshaft
Forge recirculation valve + boost controller |
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Carrera RSR
Joined: 08 Jan 2010 Posts: 2309 Location: Somerset, UK
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Posted: Mon Apr 24, 2017 5:46 pm Post subject: |
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Dutch924-racer wrote: | the mixture screw on the mass air flow meter (3mm allen key) |
That only effects the idle mixture not the AFR through the rev range. if you want to specifically adjust other areas then it's the WUR _________________ 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 |
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morghen
Joined: 21 Jan 2005 Posts: 8884 Location: Romania
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Posted: Mon Apr 24, 2017 8:32 pm Post subject: |
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Carrera RSR wrote: | Dutch924-racer wrote: | the mixture screw on the mass air flow meter (3mm allen key) |
That only effects the idle mixture not the AFR through the rev range. if you want to specifically adjust other areas then it's the WUR |
I respectfully disagree. If you adjust for a richer mixture the CIS head/plunger will open more for the same amount of air drawn trough the plate.
WUR will increase the pressure when on boost so more fuel will flow trough the system.
_________________ https://www.the924.com |
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Carrera RSR
Joined: 08 Jan 2010 Posts: 2309 Location: Somerset, UK
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Posted: Mon Apr 24, 2017 9:06 pm Post subject: |
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I thought the same Ciprian. If you enrichen the idle mixture then this would enrichen the whole sytem in a linear way, therefore enrichen cruise and WOT as the same time. On my car it did nothing for the cruise or WOT AFR's, only the idle. But I did not over adjust to prove the theory.
I have read that there are two seperate adjustments on the WUR to change the AFR elsewhere in the rev range/WOT. I think I linked a Rennlist page in the thread I did when messing around with the boost enrichment/delay.
But I may be completely wrong _________________ 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
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Then www.924board.org/viewtopic.php?t=31252 |
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Dutch924-racer
Joined: 23 Jul 2007 Posts: 1077 Location: The Netherlands
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Posted: Wed Apr 26, 2017 2:26 am Post subject: |
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I forgot to tell, I run 98 ocatane fuel and car is now still on stock boost level. _________________ 937 trackday car
Series 2 engine
951S turbo and intercooler
Fast road camshaft
Forge recirculation valve + boost controller |
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canyonblaster
Joined: 20 Aug 2012 Posts: 391 Location: Denver, CO, USA
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Posted: Fri May 05, 2017 8:43 am Post subject: |
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Carrera (& others!),
Would my IC car benefit form this mod?
Hence the 'Brian Leask' type solution which many 930 guys on their modified cars.
(EDIT: I just sent an email to Brian Leask)
Thx
Carrera RSR wrote: | A stock WUR is extremely difficult to tune to ensure the
best AFR's across the throttle and rev range. Many owners will report differing results. 14.7 is your target for idle and cruise. At wot, 10's is safest for non IC'd turbos. 11's is safe for intercooled turbos. Low 12's if you feel brave.
The one to watch with our cars is the mid range boost enrichment. Our wurs are set up for non IC. Therefore over enrichening the mixture as soon as boost kicks in regardless of throttle position. So sapping power and wasting fuel as you accelerate at semi or full wot and full boost. Hence the 'Brian Leask' type solution which many 930 guys on their modified cars. |
_________________ PCA Licensed Club Racer & Driving Instructor Current P cars: 1981 931
Past P cars, 1985 944, 1987 951, 1990 911 C4, 2002 Boxster S, 2005 996 GT3, 2013 911 C2S
Daily Driver P cars: 2008 Cayenne GTS, 2013 Cayenne GTS |
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Carrera RSR
Joined: 08 Jan 2010 Posts: 2309 Location: Somerset, UK
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Posted: Sat May 06, 2017 3:33 am Post subject: |
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if boost is significantly increased and the dizzy advance and retard has been recurved and the timing advanced. _________________ 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 |
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