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Cam timing for X33 option / ( SC cam)

Hello everyone

This is my first thread in this amazing porsche lover forum.

I own a 965 C2T 3.3L and I just bought a pair of original "X33" camshaft. These cams has been removed from an original 965 3.3L turbo "S" (355 HP). As many know, the reference of these cams which are listed into the "X33" option, are 930 105 147 50 and 930 105 148 50. However, from the reference which are engraved at the extremity of each cam ( 930-147-10 and 930-148-10 ) it seems they are simple "SC" cams ( They simply add a piece of metal for the scavange pump on one of them)

My engine will be completely repare soon and of course my shop will install these cam inside my engine. However, it is not possible to get the orginal cams timing from PORSCHE. ( They are not able to provide this information ? !!). Some people ( in france) said it must but timed at 1 to 1.2mm. Some others said it must be timed to 1.6 to 1.7mm.

If some people here want to share their expérience. It would be really appreciated !

By the way, my car is almsot full stock at present time. I just removed the cat and increase the boost pressure to 0.95 ( instead of 0.7). As my engine will be repare, I also plan to remove the air pump and all involved accessoiries.
I am also potentially interested to replace the original WUR by a Digital WUR. However, it seems this company has some trouble to deliver their product.

Thanks and regards

Thierry

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Old 02-07-2009, 05:12 AM
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Thierry, welcome. Interesting find. Those are the same cams that I found in my '85 930 Special Wishes Slant with the enhanced output engine. This was a 330BHP option back then. I see they put a more accurate rating of 355BHP for the X33 engines.
Your friends in France are right. The spec should be in the 1-1.7 mm range. If you can get it to 1.7 mm, all the better. Unless you are tracking your car, spending most of your time in the upper RPM range, time your engine cams at 1.7mm. This will provide a little bit more torque in the lower to mid RPM ranges. These engines need all they can get!

Regarding your observations about Unwired Tools' Digi-Warmup Regulator, I think they have a very good product thus far. Stuart, "stup", in Great Britain has achieved some very promising results in his install on a C2 Turbo. Everyone has been clamoring for more features, namely O2 sensor input, from them and it has been somewhat unfair to Unwired to take the rap for that. Their product already exceeds what is currently in your car. The D-WUR or Brian Leaske WUR regulators are very good additions for our cars.
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'85 930 Factory Special Wishes Flachbau
Werk I Zuffenhausen 3.3l/330BHP Engine with Sonderwunsch Cams, FabSpeed Headers, Kokeln IC, Twin Plugged Electromotive Crankfire, Tial Wastegate(0.8 Bar), K27 Hybrid Turbo, Ruf Twin-tip Muffler, Fikse FM-5's 8&10x17, 8:41 R&P

Last edited by WERK I; 02-15-2009 at 05:49 AM.. Reason: typo
Old 02-07-2009, 05:38 AM
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I pulled this off a GB club page a while back...might be of help;

Engine type: M 30 / 69 S
Exclusive Special Option No X33
Output 355 HP @ 5750 rpm
Torque 471 Nm @5000 rpm

Scope of modifications:
- cylinder head, inlet and exhaust ports modified
- inlet manifold modified
- modified camshafts
- valve timing (setting) 0.9 - 1.1.

Modified parts:
930.105.147.50 camshaft left hand
930.105.148.50 camshaft right hand
911.105.171.02 Spacer flange, left hand
911.105.172.02 spacer flange, right hand
900.105.172.02 Bolt, 4
N 010.183.1 Bolt, 1
930.113.025.03 gearwheels
N 013.349.1 roll pin
930.100.908.03 gasket set
930.104.043.14 cylinder head, 6
Old 02-07-2009, 06:40 AM
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"Some people ( in france) said it must but timed at 1 to 1.2mm. Some others said it must be timed to 1.6 to 1.7mm"

The lower the number here the more you are retarding the cam timing, and the higher number is advancing cam timing.

Advancing the cam timing gives a little more lower to midrange power which comes on smoother which is better for city driving and retarding cam timing can move the power band as much as 5-700 rpms higher and make it come on with more punch... better on the open highway and track.

If you want to move the power band still higher than SC cams can do, sell the SC cams and install 964 cams. You could also have the SC cams welded up and reground to 964 profile but thats seems a waste if they are in great shape.

The 964 cams will loose some midrange power while making more on top from around 4300 to 7000rpm timed at 1.25mm, but you can't have it all without current day variable cam timing.
Old 02-07-2009, 10:55 AM
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Dear Dave, Dear Jeff , Dear JF

Thank you very much for your kind and valuable reply . ( and sorry my tardy one ! )

Dave and JF, if my understanding is correct , the higher the value (in mm) will be , in lower in RPM the torque will occur ? (1.7mm is for street driving with torque in low and midrange RPM ) And the lower the value (in mm) will be, the higher in RPM the torque will occur ( 1.25mm or 1mm as stated in the Jeff finding, is for track & higway driving ) .

If so, I am a bit surprised because I was pretty sure it was the opposite. I am not an expert and I was certainly wrong about it. Maybe someone here has made a dyno with the different adjustement ? It could help me to see what's happen exactly.

Jeff, do you know if an original document ( I mean a scan) of what you found is available somewhere? In fact I also see the same details on the french forum. However, it is not the excat copy or the scan of the original Porsche technical bulletin. Maybe someone , somewhere has the orginal scan ?

JF, I won't destroy my cams which are something like valuable for collection ! And so far I think it is much better to buy a new pair of 964 cams if I wish to go in that way.

Dave, I am sorry, although I know you are completely right about the low and midrange behavior , I still want to get more punch and HP in the higher RPM. As to the digital WUR , I believe in this device and I perfectly understand what kind of advantages it can bring to my car. I just bought a permanent INNOVATE System to make full datalogging ( AFR, EGT, MAP ) and to display the AFR on my dash. I am not clamoring any extra features of such kind for the DIGITAL WUR ! I am just clamoring the product itself !!!!!! Until now ( there is about 2 weeks I spoke with them) they are not able to provide any answer regarding when they will be ready to deliver the product !

Regards

Thierry
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Old 02-13-2009, 12:44 AM
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Hi Thierry,
Right, the higher the value of the cam timing, the sooner the valve opens. This gives the engine the opportunity to start filling the cylinders a little sooner, thus improving the low to mid torque range. This merely shifts the torque curve a little (albeit a little) to the left. You will lose a little torque on the top end.
If you are looking for more top end, I would suggest a little wilder cam, i.e. 964 grind, to suit your needs. The duration is a little longer, giving you more fill time.
If you wish to stay with the SC cams, set your timing somewhere between the low value to mid-point.
Good luck with the dwur, it sounds like a promising product! Keep us posted with your opinions/issues. I'm very much on the fence, but starting to lean towards the darkside.
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'85 930 Factory Special Wishes Flachbau
Werk I Zuffenhausen 3.3l/330BHP Engine with Sonderwunsch Cams, FabSpeed Headers, Kokeln IC, Twin Plugged Electromotive Crankfire, Tial Wastegate(0.8 Bar), K27 Hybrid Turbo, Ruf Twin-tip Muffler, Fikse FM-5's 8&10x17, 8:41 R&P
Old 02-13-2009, 01:19 PM
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Thierry,
You have the National School for Mechanics there in your city, no? Do they have a garage where you can test the cams?

Mark
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Old 02-13-2009, 08:19 PM
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Hi Dave

Thank you very much for your confirmation and your valuable advice. At present time I will apply between 1.0 and 1.25 mm for the setting. ( It seems it is always a compromise .....and compromise always need a choice).

As to the Digital WUR, I still have no news from this company.....it is a a pîty because my car is at the workshop now and it woud be the right time to install this device while the engine will be out of the car very soon. At least they could tell me how long I am supposed to wait ... Of course I will keep you and the community informed of the result/ opinion if I install this device. In order to make the right tuning, I just ordered a complete innovate system and I will be able to record the AFR, EGT , MAP, RPM ....

By the way, I just get one idea of improvment which I would like to submit to you and to the community here. In fact this idea ( probably not new) would concern a "variable" boost pressure control and come from simple observation. The torque and power is always very high in the 4000 to 5500 range. Then after 5500 rpm the torque and the power drop. This is certainly due to the cam setting, lower air and fuel filling (maybe ignition timing either). However, I am wondering what would occur if I could increase the boost pressure between 5500 and 7000 rpm. ( of course the AFR would be adjusted accordingly by digigital wur). The wastegate keep the pressure at 0.95 bar ( at least it is supposed to do it) from 4000 to high RPM. However there is some extra potential energy here since the wastegate limit the MAP pressure and lead the extra air from the turbo directly to the atmosphere. As you know the boost pressure can be increased if the wastegate upper vent ( on the top cover ) is closed or restricted. So it is possible to control the wastegate behavior by acting to this vent. My idea would be to install an elctrical valve ( driven by an RMP switch) which could link (simple hose) the intercooler pressure to the vent of the wastegate. From idle to 5500 the valve would simply lead the wastegate vent to the atmosphere ( so there is no addition boost pressure and the wastegate have a standard behavior). Beyound 5500 rpm the switch would acting the valve which would link the (roughly equal to MAP) pressure (which can be adjusted through a knobs) from the intercooler to the vent of wastegate. Thus the boost pressure would be increased accordingly. RPM switch would be very easy to do for me since I can program an alarm with the MAP and RPM sensor that I will install on my car and use this "alarm" to drive the electrical valve.

Ok maybe this a stupid idea but if you or someone here has some comment and experience about something equal or similar ?

Dear Mark, I don't have any possibilty of such kind near my city . If so I would have contact them already .
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Last edited by Thierry25; 02-15-2009 at 02:11 AM..
Old 02-15-2009, 02:08 AM
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Thierry, the idea has been discussed. Great minds think alike!

Shop around and read up on electronic boost controllers (EBC's). Some of these devices actually have fuzzy logic built in that will help the wastegate perform much like you describe. Apexi comes to mind. Others are just controllers that override the wastegate boost spring pressure to a predetermined value.
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'85 930 Factory Special Wishes Flachbau
Werk I Zuffenhausen 3.3l/330BHP Engine with Sonderwunsch Cams, FabSpeed Headers, Kokeln IC, Twin Plugged Electromotive Crankfire, Tial Wastegate(0.8 Bar), K27 Hybrid Turbo, Ruf Twin-tip Muffler, Fikse FM-5's 8&10x17, 8:41 R&P
Old 02-15-2009, 05:25 AM
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Welcome!
I have a similar setup on my engine, SC cams and the K27-7200 turbo. Timing is set at 1.6 with good driveability. I really like the characteristics of these cams as compared to the other choices.
The power drop off in the upper range is more a function of the turbo than it is tuning. You can tune out performance but you cannot tune in more than the turbo was designed to handle.
Adding boost at the top end is a dangerous bandaid. I assume you have the stock K27-7200 turbo which is not designed to carry boost to redline. The replacement turbo for 965 top end performance application is the K27HFS. It is capable of carrying 1.0bar past redline while having a slightly lower threshold than the stock 7200.
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Old 02-15-2009, 05:36 AM
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Dear Dave
Thank you very much for your answer and for your suggestion. Finally after some google investigation I found some interesting things.

Brian, Thank you very much for your comments. It seems you are happy with 1.6mm timing too. As to the boost pressure, don't you think there is no little room to play with it ? My idea is to increase the boost level to something like 1.05 or 1.1 beyound 5700 RPM . ( with correct AFR of course). I do understand that the K27HFS is able to provide more air volume at high RPM. However it seems the standard K27-7200 still push some air in wastegate at high RPM. ( maybe it's a way to keep turbo's effeciency I don't know) So I am just wondering if there is no little improvment to make.

Thierry
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Old 02-16-2009, 09:28 AM
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Yes, the efficiency of the 7200 decreases after 5500rpm. It cannot push enough air at 1.0bar so is not capable of even more.
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Old 02-16-2009, 02:24 PM
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Dear Brian, I understand this point . It can not push enough air at high rpm while keeping 1.0 bar pressure . Just a small idea that came to me. If the standard Turbo can not provide énough air volume ( at 1.1 bar ) on high RPM, maybe it would be better to use a very low cam setting ( 0.9mm with SC cam) and to add little more boost pressure ( via electronique boost controller) in the mid RPM ( maybe between 3800 to 4500) then to maintain the 0.95 bar beyound). Thus the cam setting would provide a more torque at high RPM while the extra boost would compensate this " 0.9mm" cam setting. How do you think about this idea ?
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Old 02-17-2009, 01:12 AM
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I am pretty sure the X33 option on the 91/2 C2 Turbos used C2 normal cams, not SC cams.

Before you time them as SC cams might want to triple check this. Also important to run sport valve springs with them or I think you can shim the stock ones but do not know the spec.

Per Bruce Anderson's book, C2 cams time at 1.4 - 1.7mm. Also, says to reset springs to 34.5mm for intake and 33.5 mm for exhaust. I ran Andial Sport springs matched to them. Also should have rockers refreshed at same time.

Sorry if this missed the topic as I did not read through all above.

Best of luck.
Old 02-18-2009, 02:27 PM
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I don't know if the "X33" option is an SC or C2 cam profile, but I do know C2 or C4 is a 964.
Cam timing for 964 cams is 1.25mm

If you are tracking the car and want to move the powerband higher than time them later like around 1mm, and timing them earlier like 1.3 may or may not give a little more power at lower rpms.

I have Webcam cams in grind #40 which is a 964 or C2/C4 profile in my 930 and here is a scan of the timing specs that came with them.

I've heard the 930s or the '94 965 may have used these cams.
Old 02-18-2009, 02:49 PM
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Dear 911ST , no sorry but I am 100% sure. These cams come from X33 option ( which is called 965 3.3 turbo "s" here and is stated at 355HP ). Not kidding you. I can provide picture to you as well as engine serial number (M30/69S). The owner of the workshop I bring my car now, also own an original 965 turbo 3.3 S (355HP) . He is also 100% sure since he made the engine (M30/69S) rebuild by himself. Actually these cams seems to be referenced as 930.105.147.50 &930.105.148.50 but the real reference which is engraved on their each extremities are : 930-147-10 et 930-148-10 ....this is the same reference as SC cam. They just added the 2 flangers in order to drive additionnal devices(oil & steering pump I think).
As to the spring I bought a complete set of new one (stock) for my engine rebuild. It seems there is no special reason to change it if we don't "play"with high power over 7000 RPM . According to your estimated suggestion, I will check the question of the spring reset.

By the way, I saw through several thread that you did something like an "andial " system on your car. May I know more about this ? Actually I was quite enthousiast by the digital wur. However this device is not available and not completely ready at present time. If you want to share your idea and valuable experience in fuelling improvment, I would be very glad. :-)

Dear JF, yes you are right, the 964 cam timing is 1.25mm. It is possible that Porsche installed the 964 cams on the very rare 964 3.3 turbo S "leichbau" which is stated about 388 HP ( motor is M30/69SL / They produced only very few of this model )

Thierry
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Old 02-19-2009, 04:36 AM
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I am still suspect on the cams being SC. That goes against my recollection. When Porsche was building SC's and Carrera's they used those in there special Turbo cars. When they started building the C2/4, the used those in there special Turbo Cars. I know the S2 used C2 normal cams, replaced the stock IC core with a thicker one, and used the 7006 Turbo. For power the C2's will flow more air.

With the steeper ramps and higher lift on SC or C2 cams there has to be some accommodation at the spring or spring tension. See Bruce Anderson's book on modifying turbos.

As to the fueler. I used the Andial plumbing but not there on/off controller. For the controller I had Split Second Timing modify one of there Additional Injector Controller's to add a clock to the board. This allowed is to set frequency at a fixed rate 50 times a second instead of being a function of RPM. Then it was just a mater of programing the controller to add fuel anywhere needed along the rpm range. I went one step further and disabled the boost line to the stock WUR so I could tune the fuel curve better and not have the to rich on first boost issue. The AIC uses an rpm signal, manifold signal, and voltage. I mounted it right on the right side of the intake manifold as there is a lot of air flow in there. Did not seem to be an issue. I think the Purple wire in the motor compartment was the RPM signal. If you actually do this let me know and I will give you some programing hints that increases pre boost throttle response by getting the CIS metering plate moving faster upon acceleration.

Best of luck.

Hope this helps.
Old 02-19-2009, 08:39 AM
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Dear 911ST

As to the cams, I got your mean, however I am 100% sure. Once again I am not kidding you. In fact, the M30/69 3.3 engine is very close to the previous 930 3.3 engine. I think Porsche applied a known and reliable solution ( it was was very easy and costless for them) for the X33 version.
I have order one week ago the book that you suggested to me. :-) Dave said "great minds think alike !!! I am glad to be confirmed that I bought a good book. Not yet delivery but hurry to see it !

As to the fuelling, if you don't mind, I will send a PM to you.

Thanks
Thierry
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Old 02-19-2009, 11:47 PM
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I am thinking there might be an error as to the books specs as to setting the cam timing on a C2 cam so double check it with a real turbo builder if you were considering using it.

The C2 Turbo motor is a bit better in that the oil cooler was removed from the motor so more air goes over the cylinders. It also finally got rid of the smog cylinders and went to proper cylinders with full fins. This give is a little better thermal reserve than the earlier base motors.

I would be very surprised if Porsche used the SC grind on any of the special C2 Turbo motors. On the Turbo S and S2 they used the C2 normal cam. The S2 was a special build to qualify the Turbo for IMSA so it could be run and used a 7006 turbo. The Turbo S had a special turbo built with a larger compressor wheel like a K29.

All these cams had to be a special build to get both a drive for the turbo pump and the power steering pump. Again, I just do not see Porsche using the old SC technology on some an not others when they had a more modern cam developed from 1989 that they knew worked well with the turbo.

However, I have been wrong before.

Old 02-20-2009, 08:41 AM
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