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morghen
Joined: 21 Jan 2005
Posts: 9105
Location: Romania
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 Posted: Mon May 04, 2015 10:35 pm Post subject: S2 ignition retard, how evident is it? |
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Yesterday i took the red GTS wannabe on a joy ride for about 50km.
Engine was fully warmed up...every dial showing what it should.
I didnt drive agressively but i did get into 4th and 5th to 5000 RPM.
It was a warm day but not that warm...and like no other time there was an evident power decrease/modulation during reving up.
So i was doing 4000-RPM to 5500RPM and my butt dyno felt like there was something drawing it back from all the glorious go.
Since it wasnt very hot i'm wondering if there is something wrong with my intake temp sensor as it seems the DITC retarded the timing quite noticeably. I didnt monitor the AFR values but there is plenty of fuel...so i'm thinking its either timing retard or missfire.
Any 931 S2 drivers that can comment ?
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Cedric
Joined: 27 Aug 2004
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Location: Sweden
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| Posted: Tue May 05, 2015 12:04 am Post subject: |
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You could take the sensor out and test it.
On track i can feel that the car is a tad softer in acceleration in the end of a session. But it never feels abrupt. Could not see any drop-off after several runs im the dyno. Sounds like something is wrong..
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morghen
Joined: 21 Jan 2005
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Location: Romania
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| Posted: Tue May 05, 2015 2:46 am Post subject: |
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The difference is not huge, but its quite noticeable and i too think that there is something wrong.
I tried to get the sensor out but i dont have a key that will work there...is there a special tool or a technique to get that thing out?
So until now:
-maybe the sensor is not in specs
-partial contact at sensor (need to clean the contacts and tighten them)
-i'm also considering the transistorial amplifier unit..this might be on its way out and acting up.
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ideola
Joined: 01 Oct 2004
Posts: 15550
Location: Spring Lake MI
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| Posted: Tue May 05, 2015 6:21 am Post subject: |
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What does DITC do when IAT is unplugged????
Make sure you're not doing a false test, as I would be concerned DITC defaults to some failsafe mode if any of the sensors aren't plugged in. It might not be that smart, but I don't know off the top of my head. That's what the Lambda / O2 setup does on US cars, so it wouldn't surprise me if something similar were programmed into the DITC.
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Cedric
Joined: 27 Aug 2004
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morghen
Joined: 21 Jan 2005
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| Posted: Tue May 05, 2015 4:18 pm Post subject: |
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Idling at 1100RPM as i set it, if i dissconect the IAT the revs drop...but i'll do another test today and i'll measure the impedance of the sensor cold, during and after full warm up.
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morghen
Joined: 21 Jan 2005
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Location: Romania
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| Posted: Wed May 06, 2015 1:50 am Post subject: |
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7.5kilo cold, ~20 celsius
2.5kilo warm, ~40 celsius (normal warm engine)
Drove thd car for 15 min in city trafic and could not warm it up further.
Confirmed that cold or warm if i dissconect the IAT revs drop about 300rpm.
What does yours measure at those temps? Lol that sounds weird!
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Cedric
Joined: 27 Aug 2004
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Location: Sweden
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| Posted: Wed May 06, 2015 2:52 am Post subject: |
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Engine heat doesn't matter since it's boost temp. I think i boiled mine together with a kitchen thermometer 
Ill look it up, i went through the system when i had problems when I started running the s2 engine. Back then it was the ignition amplifier, cheap as chips to replace and solved everything has been running fine since.
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Cedric
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Carrera RSR
Joined: 08 Jan 2010
Posts: 2312
Location: Somerset, UK
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| Posted: Wed May 06, 2015 4:27 am Post subject: |
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So is the stock IAT sensor just a temp switch which is activated at a given temperature or gives a variable temperature result? I ditched the one in my S2 intake manifold for a new Zeitronix version to go with the data logger, assuming that the former would be no use versus the later. But reading this leads me to think the DITC is looking for a variable temp input.
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morghen
Joined: 21 Jan 2005
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Location: Romania
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| Posted: Wed May 06, 2015 4:53 am Post subject: |
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Yes, it has a function that reads impedance off the sensor and adjusts timing accordingly.
Is the ignition amplifier available from Porsche?
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Cedric
Joined: 27 Aug 2004
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Location: Sweden
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| Posted: Wed May 06, 2015 5:03 am Post subject: |
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I just took it from an old volvo 740 that my dad was about to scrap. So a fairly standard unit obviously. I had to redo the cooling flange though.
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