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Lets talk cams

I've had my 930 for 3 years now. Done the exhaust, suspension, wheels, brakes, turbo, intercooler and clutch. This off season (northeast) I am contemplating changing the cams. Opinions? I use the car primarily for street use. I have done a couple of DE events but for the most part she is my get away. Nice evening blast around town does wonders for the mind.

Old 09-21-2010, 05:27 PM
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That's an easy one, SC cams set at 1.6 mm. Might consider a MSD 6530 programmable ignition to allow you to build your own timing & boost retard curve.
Will really wake that bad boy up for on the street.

Cole
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Mods: TurboKraft Custom IC, 934 Headers, GSX 61, Zork, Port Work, SC Cams, Air Mod Fuel Dist Relocated, Water Meth Injection, BL WUR, MSD 6530, Greddy EBC, Synapse Bov, Short 2nd & 3rd with 8:37 R&P, Wevo Shifter, Coupling, and Mounts, MTX-L SSI-4, Big Brakes, Rebel Coilovers, Bilstein Sports.

Last edited by cole930; 09-21-2010 at 09:17 PM..
Old 09-21-2010, 09:15 PM
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Question, I suspect you are staying with CIS correct? I am not sure of the specifics size of the turbocharger, etc.

For simplicity, Cole has a good point the SC camshafts are good choice. It's a all around good profile.

Most guys don't exceed the 964 profile, and those that need something a little more exotic
( run something in around duration profile wise that of the SC or GT2 ) and something around that of the ( SC and 964 lift profile. ) There are other variables not mentioned and a lot of truths with acceptions but I think it gives a bit of food for thought.

Nice looking car.
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Old 09-21-2010, 10:08 PM
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Looking at your car wicked car!

C2 cams with 8/1 compression pistons, .8 bar boost, and a little intake porting.

If you do not want to do the pistons or mild porting, SC cams are the standard go to.

Do note that you would be best served with SC or any cam upgrade going with resurfaced rockers and high performance valve springs to deal with the higher lift.

However, where do you want to make your power?

Stock cams will make more TQ than HP. SC cams will make about equal TQ and HP, C2 cams will make more HP than TQ. You can move this around depending how they are timed. For example SC's can make peak HP anywhere between 5500 and about 6300rpm.

Where you make your TQ determines your peak HP.

300# TQ at 5000, 5500, 6000 or 6500 rpm makes 287hp, 316hp, 344hp, and 373hp. All making the same power with each RPM.

I believe if stock cams are optimized they will work best in town with the stock gears. Compliment this with a quick spool small turbo (GT 30?), optimized ignition timing, about 13.5/1 AFR off idle, and it would be very quick off the line and might even make for a higher level of usable average HP in first and second gear than more aggressive cams.

However, I do think a little differently about these things than others.
Old 09-22-2010, 05:21 PM
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I do plan on staying with CIS (until I run out of modifications and find the need to step into that realm). I would down the line like to get into the piston/twin plug/ignition mods. I figure at some point the engine will be calling for a refresh and at that time I will cross that bridge.

As far as power wants/needs I have grown with the car and slowly/yearly tried to enhance performance. I have come along way from stock. I have gone primarily with the traditional upgrades. (k27, 1 bar spring, Kokeln IC, B&B exhaust, modified air box K&N cone filter, bumped cam timing for low end responce, lightweight clutch) At the beginning of each season after making whatever modification I did I was very happy and figured that would keep me satified. Well guess I'm not satisfied. I am in pretty good shape as far as lag (compared to where I was with stock). I feel I run short on power after 5000-5500 (k27?). I am not overly excited with the exhaust note.

Do I sit here and tell you I want to dump more money into my toy and am looking for some opinions. Maybe so. Can you blame me!!
Old 09-22-2010, 06:35 PM
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Which K27? Stock fuel head? Euro head? Fuel enrichment? You need everything to work together to get the most out of your mods. All I know is with my mods, my car pulls like a freight train from 3k to redline and then some.

If you wanted a bigger turbo, one of the guys is selling a K29. This is old technology compared to the hybrid K27s from UMW, but I am quite pleased with mine. Kevin did tell me when he rebuilt my turbo it was a K29 with the latest K27 turbine, but I'm not sure how much of a difference that makes.
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Old 09-22-2010, 06:51 PM
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Did my upgrades last winter, and added SC cams with 1,65mm overlap.

Car is much more responsive at lower RPM, a good thing for street.

Here is vid driving in 4'th gear in 60mph, then hit the trottle. As you can see boost come in quick compared to stock cams and turbo.

YouTube - Impoved turbo lag 930

BTW your car looks awsome
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1979 930: Garret GT35r turbo, EFI, carerra intake, Link EMS, custom GT2 cams, 98mm JE P/C, 964 crank (stroker), custom valves & ported (XtremeCylinderHeads) etc..etc..
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Last edited by totle; 09-23-2010 at 06:53 AM..
Old 09-23-2010, 06:47 AM
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Can't you re-grind your stock 930 cams to the SC profile? I wouldn't think it would cost to much to do.
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Old 09-23-2010, 09:58 AM
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totle, What kind of numbers did you end up spending?(if you don't mind me asking) Did you do the work yourself? You may have me sold. I was out this evening for a blast and brought it up to 60 in forth put it down and went no where. I have the k27-7200 which made such a difference in a smoother more driveable ride. I would like to back that up without going too crazy. My modifications are modest but effective up to this point.
Old 09-23-2010, 05:27 PM
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BSKI,

Note that Totle did not just add cams. He also seems to have relived the ports.

Increasing ports from 32mm to 35mm increases cross section and potential by 20%.


I belive stock 930's seem to be very "port restricted."

I think I calculated once that before the intake valves are opened to 50% of stock lift, the area under the valve seats are equal to the area of the intake ports.

SC cams with increase intake duration from a stock 209 to 229 deg's. This keeps them open about 10% longer but the increase is more near TDC or TBC, not when the piston is moving at its peak speed during the intake stroke.

Being CIS complicates things as the small ports helps with air fuel mixing in aid of better low rpm pre boost ignition.

I suspect if one did two builds, one with SC cams and stock ports and one with larger ports and stock cams, the ported motor with stock cams will show a better improvement in TQ and boost response.

Never seen anyone do this. It is easer to just add cams.

Combine the longer duration cam with a less restrictive ports should maximize breathing potential as much at 30% or so for the best performance bang.

That dose not mean you can not make big power through the stock ports. I know one SC cam'd 930 motor that made 425 CIS whp with them.

SC cam, ports, a K27-7200, with optimized ignition and AFR's is a great combo for response and mid range HP.

I actually detuned my car back to this combination from C2 cams w a big K29 as I preferred the kick I got from it and it fit my driving style in town better.

Just what I belive so far.
Old 09-23-2010, 09:50 PM
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I really like totle's vid and it makes me wonder.

I think what we see in the vid is first boost at about 2k rpm and full boost by about 2500k with a 4th gear pull.

In most shorter gears I think we typically see first boost with a K27-7200 near the same 2k rpm on a 'tuned' 930 but full boost is more typically closer to 3k.

With this 4th gear pull the 7200 turbo has lots of time to spool.

Thus, I am thinking the difference between a 2500 and 3000rpm full boost is a 4th gear pull reduces the turbo's mass and friction's effect on spool time.

This makes me wonder, if we ran a BB turbo close in dimensions to a K27-7200 (and maybe with more modern wheels and less rotating mass) could we see full boost before 2500rpm in the earlier gears to.

If you read some of the adds for BB turbos, they quote around 300 to 600rpm faster boost.

I wonder.
Old 09-24-2010, 09:37 AM
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Quote:
Originally Posted by BSKI View Post
totle, What kind of numbers did you end up spending?(if you don't mind me asking) Did you do the work yourself? You may have me sold. I was out this evening for a blast and brought it up to 60 in forth put it down and went no where. I have the k27-7200 which made such a difference in a smoother more driveable ride. I would like to back that up without going too crazy. My modifications are modest but effective up to this point.
Hi, I bought the parts over the winter, have not figured out the numbers.
The cams I bought here on the board from a pelican. They are 930 cams regrinded to SC spec. Think they was around 300.
The rebuilding and porting was done by myself, so nothing else than labor time.
While engine was out I installed MSD ignition.
A free flo muffler will let your turbo spin sooner than the original muffler does.
Budget was almost gone, but wanted new headers as well, so went with OBX. I know that many here has problem with them. Welding was done good, but must admit there was a fitting issue.
Since living in Norway I needed heat, so had to weld heater boxes on.
Saving for Brians headers.


Also to have the the power down low rpm, timing is set on the higher values. SC cams can be times at 1.1-1,7. I timed mine to 1.65mm

Did a test drive together with my friends 89 930 that has 964 cams. We started in 4'th (his 5th) and my car had much quicker spoolup.
Maybe not a good comparison since he has G50-50 trans !!
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1979 930: Garret GT35r turbo, EFI, carerra intake, Link EMS, custom GT2 cams, 98mm JE P/C, 964 crank (stroker), custom valves & ported (XtremeCylinderHeads) etc..etc..
1972 914-6 GT replica project
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Old 09-24-2010, 10:50 AM
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VERY cool looking 930!

My car has SC cams, K27-7200 turbo, my intercooler, my headers and my muffler.
I see about the same boost response as Trond.
With headers your 7200 should hit boost in a similar fashion.
If you want to keep your threshold and also pull harder through redline I suggest the K27HFS.

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Old 09-24-2010, 11:01 AM
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