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Join Date: Jun 2001
Location: Sweden
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Quote:
Originally Posted by rsrmike View Post
I'm working on a RUF RCT that has an 8.5/1 3.6 w/twinplug and 964 cams. As well as a 3.6 NA intake manifold and C2 intercooler. It makes 360 whp at .77 bar/11psi. I think this equals about 415 FWHP? It's rated by RUF @ 385 FWHP... Just got the heads back from Ollies's, I'll go back to the dyno w/fresh top end and compare...

Someone told me this costs about $88,000 now for the EVO version w/a few more ponies, I'm guessing you spent around 35% of this? Sounds like your doing fine to me once you dial in the fueling issues. Good luck

Here's a link to a story about the car in question if anyone cares, although it has a new owner

http://www.rsamerica.net/articles/member/index.htm#RUF-RCT
(i hope it's okay to post this link here, please advise if it's not, thanks)
Well this just makes me more confident that 360FWHP from CIS 3.4 is not "dissapointing" in any sense. RUF dynoed their turbocharged 3.6 engine, equipped with Motronic (=hotwire EFI, no barn door) and boosting 0.77 bar at 385 FWHP. I see no reason to doubt that 0.2L smaller engine strangled with CIS and boosting .07 bar less would produce 360 FWHP while going slightly lean on the top.

Dyno shops love to goose customers by measuring power at wheels and then fudging the numbers by adding fantasy drivetrain losses, correcting for temperature and whatnot. Engine dyno is the real thing. You have torque brake, measure torque and multiply it with revs. That's it...there is no lie.

CIS is still there and it's strangling the flow, and it's influence is felt more as you keep extracting more power. You could pour more on the top and then tweak the ignition and boost for little more power. It would be good to see torque/AFR graphs first.
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Old 03-27-2008, 03:01 PM
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UPDATE

looks like the culprit to running out of fuel at 5k rpms is mostly due to a lack of system pressure. It was recoomended to be at a minimum of 95lbs. currently my pressure was running at 80lbs. So it looks like raising the pressure should get the xtra fule it needs then onto the adjusting so as not to foul 12 sparkplugs. I guess the good thing is if plugs foul now on the low end, it is easy to change. However, once the engine is back in the car, i can see where changing 12 plugs might just take me longer than a 6 pack of cold ones.

thanks to everyone that offered commnets 7 suggestions, i used them all as a checklist this morning with the mechanic and the only item on the list that stood out was the system pressure or should i say a lack of pressure.

well a few fixes and back to the engine dyno, hopefully we can get it in next week. Will update after next dyno run.
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88 930 cab w/36k miles(ok its the wife's 40th b-day present) She knows the clutch needs replaced. She doesn't know about-3.4L: LN engineering-Nikkies cylinders: 8:1 JE pistons: IA-(fuel head, XDI twin plug ignition, revalved, respringed, reguided & ported n polished heads, matched cam grind): K27HFs: Kokeln IC: Braink Leask-(WUR & RPM switch): H&K-(SSI & dual exhaust): Tial 46mm wg: and lots of parts coated by Calico Coatings.
Old 03-27-2008, 03:02 PM
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95 lbs of fuel pressure is not right for a stock CIS fuel system. To be sure, have someone look up the fuel test pressure in the Porsche shop manual. I think its closer to 55 or 60 lbs (4 or 4.5 bar).

Although I agree with Goran about dynos being suspect, I think your numbers are low for what you have. When I had my CIS car, with similar mods, I used an extrude honed stock intake with good results - 410 RWHP (on two different dynos). I am still using the stock 930 heads with EFI at over 500 rwhp now. It would be interesting to hear what IA told you what you should see since there are a lot of their parts here. They should be guiding you on the tuning process too. You have a lot of stuff changed on your motor (fuel head, spark, WUR, etc), so I am not surprised its not running up to par the first day.
Old 03-27-2008, 04:46 PM
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That sucks. You gotta have something badly out of whack. Did they check that the RPM solenoid was triggering and enabling the boost enrichment? CIS gauge would show that immediately, I would think.

Some of these figures for CIS motors sound a tad low.

My CIS motor made 395 FWHP @ 6100, 350 ft/lbs @ 5700 RPM on Bob Watson's dyno. That's 330 RWHP with RoW 3.3, 8:1 C/R, Camgrinder SC cams, factory wastegate with stock spring reads @ 12.5 PSI on the mech gauge. GHL's. Kokeln, K27/HF, dump pipe, factory RoW muffler. Stock ignition, CIS & fuel head, adjustable WUR.

Yours should make more than that. Very comfortably.

Why do I think the dyno was accurate? Same motor, before it spun a bearing, made 310 FWHP (@ 5700 RPM) with the same P&C's, heads/valves - 8:1, SC cams, stock turbo, intercooler, yada yada - oh, and a 3" open pipe for an exhaust. Pretty much right around where it should be.

My spec book gives 930 system pressure as 6.0 to 6.7 bar (88-98 PSI). I think you look to be in spec for that.
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Old 03-27-2008, 10:05 PM
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Throw the spec book out - this ain't stock.
You need ~95# system pressure to push the power. You spent a LOT of money with iA, they need to be on top of this.
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RarlyL8 Motorsports / M&K Exhaust - 911/930 Exhaust Systems, Turbos, TiAL, CIS Mods/Rebuilds
'78 911SC Widebody, 930 engine, 915 Tranny, K27, SC Cams, RL8 Headers & GT3 Muffler. 350whp @ 0.75bar
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Old 03-28-2008, 04:50 AM
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Is IA helping you with this tuning or not?
Did they say they would help with the tuning or just send youl ots of expensive parts?
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Old 03-28-2008, 07:56 AM
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Sounds like too little power to me.

Fuel pressure should be at least 6 bar or 87 psi, so it's a bit low. I'd check fuel flow too, which should be 1.5 liters in 30 seconds.

CIS is opposite to EFI when it comes to the control pressure and fuel delivery since the higher the control pressure, the less the fuel head piston can move so it flows less fuel. Where a higher pressure with EFI gives more fuel flow. What's your hot control pressure?

Have you double checked your cam and ignition timing? Of course the ignition timing should be set on the dyno so it should be right.

Was anything changed on the intake or exhaust that could be limiting flow?

I have the 100mm JE pistons and I measured a compression ratio of 7.7:1 so your compression may be a little less. I wouldn't crank up the boost until you sort out the problem, but I think 1 bar for the street and .8 or .9 for the track should be safe with enough fuel.
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Old 03-28-2008, 09:03 AM
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Quote:
Originally Posted by RarlyL8 View Post
Throw the spec book out - this ain't stock.
You need ~95# system pressure to push the power. You spent a LOT of money with iA, they need to be on top of this.
I ran stock fuel pressure at +400rwhp CIS. Are you saying you need bigger after-market pumps?

In any event, it was all probably sold as "bolt-on" . I hope it works out.
Old 03-28-2008, 06:14 PM
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No, you don't need bigger pumps, just a healthy system that puts out pressure at the top of the spec range. If the pressure is low it needs to be adjusted at the head.

It'll work out. You cannot expect to do such extensive changes and have it run perfectly with the same fuel settings adjusted at 1/3 less power. You're well aware of that, Don! Ha!
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RarlyL8 Motorsports / M&K Exhaust - 911/930 Exhaust Systems, Turbos, TiAL, CIS Mods/Rebuilds
'78 911SC Widebody, 930 engine, 915 Tranny, K27, SC Cams, RL8 Headers & GT3 Muffler. 350whp @ 0.75bar
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Old 03-28-2008, 06:37 PM
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K-Jet works on basis of differential pressure so high system pressure is by no means a guarantee that rest works correctly. It the difference between control pressure and system pressure that matters.

K-Jet is designed that way to get rid of influence of fluctuating system pressure. With other words, it will work roughly the same within certain system pressure margins. It's the differential inbetween that influences AFR's.
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Old 03-29-2008, 09:13 AM
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Yes, that is true, but starting at the higher end gives you more volume to work with.
Any way you look at it 80# is too low.
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RarlyL8 Motorsports / M&K Exhaust - 911/930 Exhaust Systems, Turbos, TiAL, CIS Mods/Rebuilds
'78 911SC Widebody, 930 engine, 915 Tranny, K27, SC Cams, RL8 Headers & GT3 Muffler. 350whp @ 0.75bar
Brian B. (256)536-9977 Service@MKExhaust Brian@RarlyL8
Old 03-29-2008, 09:50 AM
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