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ideola
Joined: 01 Oct 2004 Posts: 15548 Location: Spring Lake MI
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Posted: Thu Jul 06, 2017 12:31 am Post subject: |
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There is no information at all that I can find on what the DITC does with rev limiting. However, it is conceivable that if the different pre-programmed maps can do things like timing retard, they may also have different rev limits that kick in when different conditions exist. If your engine is running hot, maybe it's causing a different map with a different rev limit to be selected.
I would want to figure out why the engine is running too hot first. Maybe if you get that sorted, the rev limit problem goes away. First thing I would do is double check coolant bleeding, ensure there are no air pockets in the system. Make sure to bleed system with heater controls set to full heat. Make sure the vent line isn't plugged, and make sure you have a fresh cap on the expansion tank.
Have you swapped in the colder-range thermostat and fan temperature switch? If not, you should definitely do that. I also like running a bottle of water wetter.
Try running colder plugs.
You still haven't indicated what boost pressure you're running. I would set that back stock level, and possibly consider eliminating the boost controller (are you sure it's installed the correct way? maybe you're overboosting and don't know it???). The best way to plumb the boost gauge is to tee into the line that is also feeding the DITC, this way your gauge is showing you exactly the same signal as the DITC is seeing. _________________ 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: Thu Jul 06, 2017 1:10 am Post subject: |
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I got a 80c celcius themostat and low temp sender
Boost was already turned back to +/- 0,65 bar
I will T it in the DITC line (now it is just before the intercooler)
AFR is set to 14.7/15 @ idle, under boost is is around 11
Spark plugs I did change, previous engine it was NGK racing, now Bosch, I will search for the numbers _________________ 937 trackday car
Series 2 engine
951S turbo and intercooler
Fast road camshaft
Forge recirculation valve + boost controller |
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ideola
Joined: 01 Oct 2004 Posts: 15548 Location: Spring Lake MI
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Posted: Thu Jul 06, 2017 2:59 am Post subject: |
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Dutch924-racer wrote: | Boost was already turned back to +/- 0,65 bar
I will T it in the DITC line (now it is just before the intercooler) |
So, just before intercooler, you mean pre-throttle body but post turbo charger...yeah, that's an issue. You need to read boost from the inlet manifold.
But I would still be very concerned about the running hot issue. I think that is a bigger concern right now...fix that and then let's see what's going on with the RPM cut out. _________________ 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: Thu Jul 06, 2017 5:21 am Post subject: |
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the running hot and ignition problem could be related.
The cooling system hasn't changed I only changed the coolant cap of the reservoir. It was 150kpa and changed it for a 100kpa. I will swap it back to rull it out.
So far thanks for all the advice, got enough to do now
14 juli is a trackday, hopefully I get it fixed before that date.
_________________ 937 trackday car
Series 2 engine
951S turbo and intercooler
Fast road camshaft
Forge recirculation valve + boost controller |
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Dutch924-racer
Joined: 23 Jul 2007 Posts: 1077 Location: The Netherlands
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Posted: Fri Jul 07, 2017 1:45 am Post subject: |
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Just another test day, replaced the DITC sensor, still the same problem, cuts of @ 5800 and the tacho bounces down and then up again at that moment.
The cut off is not temperature related, the coolant gauge was just in the middle at that moment.
I haven't changed the spark plugs yet but they can't be the problem of this cut off.
I don't have a spare coil, so have to buy a new one. _________________ 937 trackday car
Series 2 engine
951S turbo and intercooler
Fast road camshaft
Forge recirculation valve + boost controller
Last edited by Dutch924-racer on Fri Jul 07, 2017 4:22 am; edited 1 time in total |
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Cedric
Joined: 27 Aug 2004 Posts: 2614 Location: Sweden
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Posted: Fri Jul 07, 2017 2:24 am Post subject: |
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When i had ignition module problems the tach bounced alot and i got ignition issues, but it was much more random, its super cheap to replace. Do you have a spare ditc box? _________________ 1980 924 Turbo
www.instagram.com/garagecedric/ |
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Dutch924-racer
Joined: 23 Jul 2007 Posts: 1077 Location: The Netherlands
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Posted: Fri Jul 07, 2017 4:05 am Post subject: |
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All the ignition parts have now been swapped for good working components, except from the coil en ignition leads. Makes no difference.
1 — Timing control unit
4 — Temperature sensor
5 — Throttle switch (tested not swapped)
6 — Flywheel sensor
9 — Ignition control unit _________________ 937 trackday car
Series 2 engine
951S turbo and intercooler
Fast road camshaft
Forge recirculation valve + boost controller |
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morghen
Joined: 21 Jan 2005 Posts: 8884 Location: Romania
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Posted: Fri Jul 07, 2017 10:14 pm Post subject: |
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How does the limiting sound? do you have a video?
Is your tacho working right...? _________________ https://www.the924.com |
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Carrera RSR
Joined: 08 Jan 2010 Posts: 2309 Location: Somerset, UK
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Posted: Sat Jul 08, 2017 1:23 am Post subject: |
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When the FPR cuts fuel its quite a violent end to the revs. Almost a large backfire and complete engine shut down. I've experienced this with the overboost switch before earthing it out/disconnecting the switch
Never hit an electronic rev limit/fault to know what this is like whether its softer or not to the FPR cut out
If the tacho fails, its usually a connection from coil to FPR. They share the feed to tacho with a green(?) wire _________________ 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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Dutch924-racer
Joined: 23 Jul 2007 Posts: 1077 Location: The Netherlands
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Posted: Sat Jul 08, 2017 6:02 am Post subject: |
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morghen wrote: | How does the limiting sound? do you have a video?
Is your tacho working right...? |
Tacho works right I already swapt it with another one.
It feels/sounds like a rev limiter.
Tomorrow I am going to look in the wiring of the DICT/ fuel system.
Does the DITC box itself needs to be grounded ?
Spark plugs in the old engine where NGK B8EGV Gold Palladium. Now I run Bosch 0 241 256 517 double platina _________________ 937 trackday car
Series 2 engine
951S turbo and intercooler
Fast road camshaft
Forge recirculation valve + boost controller |
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ideola
Joined: 01 Oct 2004 Posts: 15548 Location: Spring Lake MI
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Posted: Sat Jul 08, 2017 6:37 am Post subject: |
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Plugs should have nothing to do with it. I think there is a rev limiter in the DITC, and you have somehow gotten stuck on a rev-limited map. Maybe it's in some default / limp mode, or one of your sensors is telling it something that makes it revert to a rev-limited map. If it were an intermittent wiring fault within the FPR circuit, it would be highly unlikely for it to consistently cut out right at 5800 RPM. _________________ erstwhile owner of just about every 924 variant ever made |
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Carrera RSR
Joined: 08 Jan 2010 Posts: 2309 Location: Somerset, UK
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Posted: Sat Jul 08, 2017 9:32 am Post subject: |
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Just a note, I've been running NGK iridium BR10EIX plugs for the last year after ditching the the 8's. colder plugs have been running fine on higher boost for me. But as Dan mentioned, don't believe your problem here is plug related. But colder plugs wil help cool the combustion a touch. _________________ 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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Dutch924-racer
Joined: 23 Jul 2007 Posts: 1077 Location: The Netherlands
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Posted: Sat Jul 08, 2017 3:50 pm Post subject: |
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ideola wrote: | Plugs should have nothing to do with it. I think there is a rev limiter in the DITC, and you have somehow gotten stuck on a rev-limited map. Maybe it's in some default / limp mode, or one of your sensors is telling it something that makes it revert to a rev-limited map. If it were an intermittent wiring fault within the FPR circuit, it would be highly unlikely for it to consistently cut out right at 5800 RPM. |
I also swapped the the DITC so the problem is not in the DITC. Could be the wiring or the cut off sensor or the temperature sensor. _________________ 937 trackday car
Series 2 engine
951S turbo and intercooler
Fast road camshaft
Forge recirculation valve + boost controller |
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ideola
Joined: 01 Oct 2004 Posts: 15548 Location: Spring Lake MI
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Posted: Sat Jul 08, 2017 5:12 pm Post subject: |
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I think maybe you're missing my point.
What if the DITC has a map specifically for limp home condition; and what if there is something about your configuration that is triggering that map?
This assumes, of course, that there is a rev limit in the DITC, which as discussed earlier has been hypothesized in several of the historic threads I've perused, but not conclusively confirmed. The FSM and all of the supplements I have say nothing about rev limiting in the DITC or elsewhere. _________________ erstwhile owner of just about every 924 variant ever made |
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Carrera RSR
Joined: 08 Jan 2010 Posts: 2309 Location: Somerset, UK
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Posted: Sat Jul 08, 2017 6:26 pm Post subject: |
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Is the rev limit a hard cut off or just that the motor feels strangled at the top end? I hardly ever get to 5800 as my motor starts to feel less effective. All the boost/torque is at 3000-5000 rpm. All starts to tail off over 5000.
You havent mentioned what boost you are running?
Forge bov are known to leak boost if the spring is too soft
Is the rev limit electrical or fuel related?
I had a bad fuel filter once which wouldn't allow my motor to rev over 5000rpm. Flow was too restrictive
An advanced cam has great low end pick up but the motor struggles at the top end. A retarded cam has slow pick up but great top end ability. One tooth out does make a difference
Is your fast idle and rev limitation connected? _________________ 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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