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931 S2 cuts off @ 5800 rpm
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Dutch924-racer  



Joined: 23 Jul 2007
Posts: 1001
Location: The Netherlands

PostPosted: Sun Jul 09, 2017 5:22 am    Post subject: Reply with quote

Carrera RSR wrote:
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?


by change I flipped the Forge recirculation valve today and put a heavier spring in it, the car now revs up to 6300/6400 rpm and doesn't cut abrubtly off like before and no bouncing tacho anymore (still don't understand that).

6300/6400 rpm is fine but I have a even more heavier spring (red/strongest available). Obviously the values for the springs on the Forge website are not suitable for a 931 setup

The picture in my older topic of the way the Forge was mounted, now the boost is on the other port, but don't know if that made a difference. http://www.924board.org/viewtopic.php?t=43093&highlight=

I did some other minor thing, like cleaning the contacts of the coil and tacho, but do'n't think that made the difference.

Hopefully the problem stay's away

The idle is still to high, will go further on that in te other topic : http://www.924board.org/viewtopic.php?t=43184
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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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Dutch924-racer  



Joined: 23 Jul 2007
Posts: 1001
Location: The Netherlands

PostPosted: Sat Jul 22, 2017 7:04 am    Post subject: Reply with quote

Update, the cut of problem seems to be in the rev counter.

I swapped back the rev counter of a early 1976 924 but the cut off came back.

How is the possible?

I wanted to use the early 924 rev counter because the red part is on top and better visible on track driving.


_________________
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 Sat Jul 22, 2017 4:31 pm; edited 1 time in total
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ideola  



Joined: 01 Oct 2004
Posts: 15489
Location: Woodstock IL

PostPosted: Sat Jul 22, 2017 7:40 am    Post subject: Reply with quote

Wow, baffled! In4TheUpdates!
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15 981 GTS | 88 924S SE | 82 931 Holbert | 82 931 Rallye | 81 937 | 81 Euro 931 | 81 Weissach | 80 US 928 | 80 US 931 '941' | 80 US 931 | 80 931 GTR | 79 Sebring | 78 D-Prod Replica | 78 w/D-Prod kit | 78 Poli-Form | 78 Limited Edition | 77 Martini
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