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931 S2 cuts off @ 5800 rpm
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Dutch924-racer  



Joined: 23 Jul 2007
Posts: 993
Location: The Netherlands

PostPosted: Mon Jul 03, 2017 2:16 am    Post subject: 931 S2 cuts off @ 5800 rpm Reply with quote

My 931 S2 cuts off @ 5800 rpm, at that moment the tacho goes to 0.

Strange thing is that I don't have a rev limiter
I also got a normal rotor
The pressure sensor is bypassed to earth
The fuel relay is a KAE one

The DITC is one of a 937 but I sure it has no rev limiter because I have driven it at highers revs with my previus engine.

The car runs and start great, only the idle is to high (see other topic)

What coul it be ?
_________________
937 trackday car
Series 2 engine
951S turbo and intercooler
937 DITC
Fast road camshaft
Forge recirculation valve + boost controller


Last edited by Dutch924-racer on Mon Jul 03, 2017 5:25 am; edited 1 time in total
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Paul  



Joined: 02 Nov 2002
Posts: 9296
Location: Southeast Wisconsin

PostPosted: Mon Jul 03, 2017 4:28 am    Post subject: Reply with quote

Are you sure your fuel pump relay doesn't have a built in limiter?
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White 87 924S "Ghost"
Silver 98 986 3.6l 320 HP "Frank N Stein"
White 01 986 "Christine"
Polar Silver 02 996TT. "Turbo"
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Dutch924-racer  



Joined: 23 Jul 2007
Posts: 993
Location: The Netherlands

PostPosted: Mon Jul 03, 2017 5:32 am    Post subject: Reply with quote

the KAE 3.300.300 doesn't have a rev limiter
_________________
937 trackday car
Series 2 engine
951S turbo and intercooler
937 DITC
Fast road camshaft
Forge recirculation valve + boost controller
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morghen  



Joined: 21 Jan 2005
Posts: 7764
Location: Romania

PostPosted: Mon Jul 03, 2017 5:31 pm    Post subject: Reply with quote

Crank sensor fault?
I drove mine at 6500 RPM
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Dutch924-racer  



Joined: 23 Jul 2007
Posts: 993
Location: The Netherlands

PostPosted: Wed Jul 05, 2017 7:28 am    Post subject: Reply with quote

just did some swapping with working parts:

- temperature sensor
- DITC
- timing control unit

I also
- tested the TPS
- bridged the fuel relay

all no effect

Anybody got a clue ?
_________________
937 trackday car
Series 2 engine
951S turbo and intercooler
937 DITC
Fast road camshaft
Forge recirculation valve + boost controller
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Dutch924-racer  



Joined: 23 Jul 2007
Posts: 993
Location: The Netherlands

PostPosted: Wed Jul 05, 2017 8:01 am    Post subject: Reply with quote

should the 'retard connector' on the right side above the headlight be connected on ROW cars ?

I am running octane 102 fuel
_________________
937 trackday car
Series 2 engine
951S turbo and intercooler
937 DITC
Fast road camshaft
Forge recirculation valve + boost controller
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Paul  



Joined: 02 Nov 2002
Posts: 9296
Location: Southeast Wisconsin

PostPosted: Wed Jul 05, 2017 8:23 am    Post subject: Reply with quote

Does your car have a knock sensor?
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White 87 924S "Ghost"
Silver 98 986 3.6l 320 HP "Frank N Stein"
White 01 986 "Christine"
Polar Silver 02 996TT. "Turbo"
Owned and repaired 924s since 1977
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Carrera RSR  



Joined: 08 Jan 2010
Posts: 1522
Location: Somerset, UK

PostPosted: Wed Jul 05, 2017 8:50 am    Post subject: Reply with quote

Dutch924-racer wrote:
should the 'retard connector' on the right side above the headlight be connected on ROW cars ?

I am running octane 102 fuel


Can’t remember which way round, but iirc you connect/disconnect it for a 7-8deg retard when using low octane fuel. Need to confirm in the FSM which way round it is.

Temp sensor also triggers a retard if intake air too warm/hot
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1980 931 - forged pistons, Piper cam, CGT turbo, 951 ducted FMIC, custom intake, Mittelmotor dizzy & cam pulley, H&S exhaust, GAZ Gold, Fuch'ed, Quaife LSD
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Dutch924-racer  



Joined: 23 Jul 2007
Posts: 993
Location: The Netherlands

PostPosted: Wed Jul 05, 2017 4:13 pm    Post subject: Reply with quote

• A wire plug connection can be seen in the engine compartment on the left wheel housing. If it is disconnected, the entire ignition timing will be retarded by about 7°.

So it should be connected
_________________
937 trackday car
Series 2 engine
951S turbo and intercooler
937 DITC
Fast road camshaft
Forge recirculation valve + boost controller
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morghen  



Joined: 21 Jan 2005
Posts: 7764
Location: Romania

PostPosted: Wed Jul 05, 2017 6:17 pm    Post subject: Reply with quote

That's right, wire needs to be connected so you don't get 7deg retard but I don't think that also lowers the RPM limiter.
You haven't replaced the crank sensor...and please post a picture of the rotor inside the spark distributor...

This is a non limiting rotor:



This is an RPM limiting rotor:

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Dutch924-racer  



Joined: 23 Jul 2007
Posts: 993
Location: The Netherlands

PostPosted: Wed Jul 05, 2017 7:06 pm    Post subject: Reply with quote

I have the non limiter for sure

The cranksensor I didn't check yet, will swap it for another one and let you know. That is the last component of the ignition system except form the coil/ leads and wiring.

Other thing I going to check:

Forge boost controller
Forge Dumpvalve
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937 trackday car
Series 2 engine
951S turbo and intercooler
937 DITC
Fast road camshaft
Forge recirculation valve + boost controller
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morghen  



Joined: 21 Jan 2005
Posts: 7764
Location: Romania

PostPosted: Thu Jul 06, 2017 12:09 am    Post subject: Reply with quote

wait, you haven't replaced the coil yet? do that before the sensor...much easier and faster.
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ideola  



Joined: 01 Oct 2004
Posts: 15486
Location: Woodstock IL

PostPosted: Thu Jul 06, 2017 12:22 am    Post subject: Reply with quote

I think you guys are chasing down the wrong things. I don't see how coil, crank sensor, temp sensor, or retard connection would have anything to do with rev limiting. The air temp sensor retards timing, it does nothing to revs. I would also be very hesitant to tamper with a known good working crank sensor. They are really easy to damage taking in and out. In every case I am aware of, the crank sensor either works or it doesn't. If the car starts, the crank sensor is probably just fine.

After thinking about this, I did some digging through some older posts, and I've read several threads that indicate the rev limiting is in the DITC, although I have yet to see definitive proof documented in the FSM or otherwise. I would focus on the fuel pump relay, the rotor, and the DITC. Which DITC units do you have? (Post numbers). There is a difference between Euro spec, US spec, and GT spec. Maybe the US spec has a rev limiter in it and that's what you're using? I don't have a running US-spec S2, only my Club Sport (Euro spec S2) and GT. Both of these will pull past 6000 RPM with no problem.
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Dutch924-racer  



Joined: 23 Jul 2007
Posts: 993
Location: The Netherlands

PostPosted: Thu Jul 06, 2017 12:57 am    Post subject: Reply with quote

the strange thing is that as soon as the tacho hits 5800 it bounces back a lot, feels like a cut off.

I tested two DITC, both good working:

5 WK 1664 (standard one) and the 5 WK 1666 (Carrera GT). Both used to rev 6500 easy.

I hope to swap the flywheel sensor tonight.

My previous engine was running fine, I rebuild it because of oil use.

Modifications made:
- stage 1 cam
- Forge recirculation valve
- Forge manual boost controller
- 951 k26/8 turbo
- other flywheel form a S2/GT(i used to have one with the rubber clutch type)
- fuel distirbutor S2 (had one form a S1 before)

The rest of the components are form the 'old' engine.

The engine also gets a bit hot, strange because I use a 944 turbo radiator with twin fans.
May be the ignition timing is incorrect. I noticed it before when I tried to adjust idle, I can't see the dot on the flywheel.

I checked the tdc, Z1 on the flywheel is correct with the markings on the camshaft and crankshaft pulley
_________________
937 trackday car
Series 2 engine
951S turbo and intercooler
937 DITC
Fast road camshaft
Forge recirculation valve + boost controller
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Carrera RSR  



Joined: 08 Jan 2010
Posts: 1522
Location: Somerset, UK

PostPosted: Thu Jul 06, 2017 1:25 am    Post subject: Reply with quote

Cam timing too retarded?
Fuel leaning out at top end? Do you have AFR?
Boost ok at the top end? Not leaking due to Forge?
_________________
1980 931 - forged pistons, Piper cam, CGT turbo, 951 ducted FMIC, custom intake, Mittelmotor dizzy & cam pulley, H&S exhaust, GAZ Gold, Fuch'ed, Quaife LSD
Now www.924board.org/viewtopic.php?t=34690
Then www.924board.org/viewtopic.php?t=31252
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