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Join Date: Feb 2005
Location: Portland
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Porsche Crest Help with CIS driveability problem....

I was taking my car to a show today and I experienced full time what was something that would happen only once in a while before and now has become a constant issue.

Vehicle 1977 930 3.0 Litre
Now 3.2 Litre , 8:1 CR, 964 cams, K27 - 7200 turbo, Full bay IC, GHL headers, and muffler, Stock euro fuel system with new fuel and air filter. I hope this info makes for an easier response.

On acceleration with little to no boost the car runs out great however with moderate throttle the car starts to quiver and bog and smoke black from the exhaust. When you give full throttle this gets much worse and seems like it wants to die then all of the sudden it will pull to red line in first gear. Once you shift into second gear or any gear after the symtoms are the same but the car will not get passed the bogging problem as easily if at all.

Cold and hot starts are never a problem although it does have an issue also with a wandering idle that is influenced heavily by ambient temperature. Idle is usually too high in cold weather and too low when warm outside.

This issue makes climbing hills a real downer. I miss the days of pulling like a freight train on hills and passing anything but a gas station.

Can anyone give me any pointers on how to get my baby back in good health?

Thanks in advance!
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77 930 "P Zilla" 3.2 Litre w / EFI conversion
Old 02-16-2007, 11:46 PM
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Possibly need to hook up some CIS pressure gauges ?
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1981 UK 930. G50/01 shortened, 964 3.8RS Fibreglass Body Kit, 18" Alloys 8.5" F & 10" R, 225's F & 285's R, Special Colour Metallic Blue Paint, FIA Sparco Evo's, A/C and Air Pump removed, Electronic Boost Controller, GHL Headers, Tial46 WG.
Fitting - New service kit.
Needs Fitting - Innovate XD-16 Kit, Kokeln IC. Stephen's K27 HFS, EVO Intake Assy & his Modded USA Fuel Head.

1983 UK 911 3.2 Carrera Sport Coupe. Black, Black Leather with Red Piping, Black Alloy Gear Knob, K&N Air Filter Element, Turbo Tie rods.
Needs Fitting - K&N CO Sensor, Round A/F Dial Gauge, Factory Short Shift Kit.

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Old 02-17-2007, 01:04 AM
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I'd hook up the gauges. Sounds like it's too rich (fuel pressure too low)
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Old 02-17-2007, 04:21 AM
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I have the same car only stock build. Go with the pressure checks first. Also, check fuel delivery. My experience has been if the pressure drops off under load, the mixture goes rich. I'm assuming the reduction in control pressure has a greater influence on the delivered results than the reduction of supply pressure. My car was rich @ idle, lean under acceleration, rich under initial boost then buck horribly when it ran out of fuel on the top end. My recommendation is to eliminate fuel delivery first before making any adjustments or repairs to any other component. I'm replacing the failed rear pump on my car now, which caused my lack of delivery volume. Once that's done, I'll be faced with undoing all the other adjustments made that have been a compromise for lack of fuel. Your car needs at least 1170 cm in 30 seconds with a stock build. Your build will probably require about 1500cm in 30 seconds. I can explain the test procedure if you are not familiar but I won't bore you with the details now in case you already know. My car was delivering 1000cm when my problem arose. That's enough fuel for about 260hp gross. Anything over that, you'll hit the limits.
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'77 930 turbo Garretson I/C 1 BAR spring, (2) '82 Triumph Bonneville Royal Wedding Edition
Past rides: '74 914 1.9 liter twin plugged track car, '83 928S, '87 924S, '75 911S w '78 ROW 3.0, '72 911T, '70 911T and various other insignificant domestic examples. Happiness is a grey tailpipe! Turbo lag......it's worth the wait!
Old 02-17-2007, 04:40 AM
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Quote:
Originally posted by 930turbo
I have the same car only stock build. Go with the pressure checks first. Also, check fuel delivery. My experience has been if the pressure drops off under load, the mixture goes rich. I'm assuming the reduction in control pressure has a greater influence on the delivered results than the reduction of supply pressure. My car was rich @ idle, lean under acceleration, rich under initial boost then buck horribly when it ran out of fuel on the top end. My recommendation is to eliminate fuel delivery first before making any adjustments or repairs to any other component. I'm replacing the failed rear pump on my car now, which caused my lack of delivery volume. Once that's done, I'll be faced with undoing all the other adjustments made that have been a compromise for lack of fuel. Your car needs at least 1170 cm in 30 seconds with a stock build. Your build will probably require about 1500cm in 30 seconds. I can explain the test procedure if you are not familiar but I won't bore you with the details now in case you already know. My car was delivering 1000cm when my problem arose. That's enough fuel for about 260hp gross. Anything over that, you'll hit the limits.
Please go further for me? You are not boring me, in fact you have my FULL attention now!

Thank you so much for the help!
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77 930 "P Zilla" 3.2 Litre w / EFI conversion
Old 02-17-2007, 09:02 PM
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The first test to conduct is the fuel delivery rate. The CIS system finesses the mixture via pressure and opposing pressures. If the deliver is anything less than adequate, every other aspect is potentially influenced. The test is relatively easy if your stock air box is removed because you need to access the plug attached at the front side of the airflow metering device between the fuel distributor and metering plate. Once you have access to this, locate the fuel return line on the left side of the engine bay. It exits the fuel distributor from a hard line visible from the rear and heads to the left. There is a "T" in the line that attaches to the base of the accumulator. While I'm thinking about it, a leaky accumulator will allow supply fuel to bypass your CIS which can also cause undesirable results. The line on the bottom of the accumulator provide somewhere for the fuel to go when it fails, that's it only purpose. I disconnected the line from the bottom of the accumulator and plugged the line itself during the test. The idea is to measure to volume of fuel flowing through the return line to the tank. Once the accumulator has been isolated, locate the connection between the hard line and rubber line and disconnect. I attached a short piece of line here (hard line side) so I could place it in my collection container. I used a .5 liter water bottle for the test. Turn the key on, the pumps should NOT run. Pull the plug previously mentioned loose from the meter box and time how long it takes to fill the .5 liter bottle. You can stop the flow by reconnecting the plug at the appropriate time. A little simple math will determine your delivery rate. Basically, your looking to fill a .5 liter bottle in 10 seconds. I hope this makes sense. Good luck with the test, let me know the results. Once you've eliminated this, we can move on the WUR control pressures.
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'77 930 turbo Garretson I/C 1 BAR spring, (2) '82 Triumph Bonneville Royal Wedding Edition
Past rides: '74 914 1.9 liter twin plugged track car, '83 928S, '87 924S, '75 911S w '78 ROW 3.0, '72 911T, '70 911T and various other insignificant domestic examples. Happiness is a grey tailpipe! Turbo lag......it's worth the wait!
Old 02-18-2007, 05:16 AM
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My car has similar problem finaly front pump died so fuel deliver was the problem. I just put in a sx race pump good for 1000 h.p. motor and you only need one pump ( $ 321.00 ) .
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Old 02-18-2007, 05:58 AM
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Quote:
Originally posted by 930turbo
The first test to conduct is the fuel delivery rate. The CIS system finesses the mixture via pressure and opposing pressures. If the deliver is anything less than adequate, every other aspect is potentially influenced. The test is relatively easy if your stock air box is removed because you need to access the plug attached at the front side of the airflow metering device between the fuel distributor and metering plate. Once you have access to this, locate the fuel return line on the left side of the engine bay. It exits the fuel distributor from a hard line visible from the rear and heads to the left. There is a "T" in the line that attaches to the base of the accumulator. While I'm thinking about it, a leaky accumulator will allow supply fuel to bypass your CIS which can also cause undesirable results. The line on the bottom of the accumulator provide somewhere for the fuel to go when it fails, that's it only purpose. I disconnected the line from the bottom of the accumulator and plugged the line itself during the test. The idea is to measure to volume of fuel flowing through the return line to the tank. Once the accumulator has been isolated, locate the connection between the hard line and rubber line and disconnect. I attached a short piece of line here (hard line side) so I could place it in my collection container. I used a .5 liter water bottle for the test. Turn the key on, the pumps should NOT run. Pull the plug previously mentioned loose from the meter box and time how long it takes to fill the .5 liter bottle. You can stop the flow by reconnecting the plug at the appropriate time. A little simple math will determine your delivery rate. Basically, your looking to fill a .5 liter bottle in 10 seconds. I hope this makes sense. Good luck with the test, let me know the results. Once you've eliminated this, we can move on the WUR control pressures.
I will do that soon! Thanks for the help!
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77 930 "P Zilla" 3.2 Litre w / EFI conversion
Old 02-18-2007, 09:08 AM
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