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Quote:
Originally Posted by 911st View Post
Might just be crazy thinking.
Not crazy at all!

I gave this some serious thought a couple of years ago, but didn't do anything with it. I thought I could drop the system pressure down to the NA levels, re-tune the WUR for the best off-boost performance, then have a boost referenced regulator to bump the system pressure up with boost. Hoping for better AFR control.

The downfalls I found, is the original designers of the CIS system went to a lot of trouble to get very consistant system pressure, with the damper in the fuel system, and balance chambers in the head. The reaction to the pressure change may be slow, and may upset the overall balance of the system.

I would love to see a direct bolt-in digital fuel head replacement, with full digital control of each cylinder injector, bypassing the WUR and other components completely.
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Old 01-21-2010, 11:28 AM
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Are you sure we are not both crazy?

How about just ditching the FD and put a magazine with a bank of EFI injectors there that are phased opposite each other.

Or, pull the metering pin assembly and replace it with a cartridge plumbed out the top of the FD center and hooked to a high capacity frequency valve or bank of injectors . No metering arm or pin needed.

It would take a pretty simple ECU to match the CIS's abilities. Could add temp compensation, TPS and other functions if one wanted.

-----

I very much like the idea of using system pressure to compensate for boost enrichment. That is what Protomotive & the Vortec dose with there kits with EFI and it seems to be able to compensate quite well. I think most EFI injection starts at around 30 to 45psi and by bumping pressure support twice the HP.

If we can operate at about 52psi ( 3.5 bar) N/A and up to 120psi (8 bar) on boost it might work well up to 1.3bar boost.

The challenge is we do not want the metering plate to stall before our peak on boost HP level is achieved so we need on our base (and only) control pressure to to keep the metering plate from stalling before say a peak of 600hp is reached. We might think of converting the WUR to a vaccum sensing for on cruse AFR and a little lower for N/A WOT AFR.

This will reduce the restriction at the metering plate to some degree over that of a 930 before 5 psi where enrichment is triggered for a little faster boost response.

Thus, 100hp at N/A WOT would be at about 13.2/1, at .7 bar, about 12.5/1. At one bar about 11.5. with a boost sensitive level of enrichment.

The more boost, the higher the AFR.

One a 930 it is only N/A AFR or after about 6 psi on boost AFR.

What is the control and system pressure levels an SC operates at?

Last edited by 911st; 01-21-2010 at 01:46 PM..
Old 01-21-2010, 01:43 PM
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Quote:
Originally Posted by 911st View Post
Are you sure we are not both crazy?
Anyone trying to get a fuel system that came out in the mid 70's, to feed a modern high HP engine has to be a little crazy!

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Originally Posted by 911st View Post
Or, pull the metering pin assembly and replace it with a cartridge plumbed out the top of the FD center and hooked to a high capacity frequency valve or bank of injectors . No metering arm or pin needed.

It would take a pretty simple ECU to match the CIS's abilities. Could add temp compensation, TPS and other functions if one wanted.
That's what's been in the back of my mind for awhile. Something like a MegaSquirt controlling a fast stepper motor, connected straight to the plunger. Pull the metering arm and pin, slap on the stepper motor, temp sensors, throttle pot, MAP, etc. Re-tune and go.

Quote:
Originally Posted by 911st View Post
What is the control and system pressure levels an SC operates at?
Need to look at my handy dandy spec manual when I get home.
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Old 01-21-2010, 02:11 PM
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Quote:
Originally Posted by WinRice;5139396 ... Something like a MegaSquirt controlling a fast stepper motor, connected straight to the plunger...[/QUOTE

I thought of the stepper motor thing to.

Controlling an injector or frequency valve is easier for most and most controller can do so.

Dose the MS control a stepper motor?
----

How about just bypassing the metering pin with injectors or frequency valve and use the injectors to pass fuel around the metering pin instead of moving it up and down.

Mod the fuel pin so fuel can enter from the top of the FD and flow down into the upper chamber metering slits. Mill it on three sides to do this.

Put a spring above the metering pin to keep it at the bottom of its travel.

Remove the arm and mod it so the CO screw can still be used to set CO at idle.

Attach a fuel line to the top of the FD where the control pressure fitting was. Enlarge opening if needed.

Attach/Tee in a fuel line to the fuel supply line to the FD.

Put a bank of injectors in line between the fuel supply connection and the top of the fuel dist.

Use EFI system of your choice.

Idle fuel will be supplied as normally from fuel going around the fuel pin. Fuel above that comes down from the top of the metering pin as supplied by the injectors.

Cool???

Last edited by 911st; 01-21-2010 at 03:27 PM..
Old 01-21-2010, 03:25 PM
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Quote:
Originally Posted by 911st
Dose the MS control a stepper motor?
Since the circuit board and firmware are open source, with a little work, it could be adapted to run a stepper. The stepper could also be as simple as a high quality R/C plane servo, some of those can sweep 60 degrees in .09 sec.

Quote:
Originally Posted by 911st
Put a bank of injectors in line between the fuel supply connection and the top of the fuel dist.
Thought about that too, but to get the most fuel through the CIS injectors would need a fuel pressure in the 7 bar range, therefore, the 'injector bank' would have to operate at 7 bar, which most injectors can't handle.
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Old 01-21-2010, 07:03 PM
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Quote:
Originally Posted by 911st View Post
What is the control and system pressure levels an SC operates at?
1980 SC

Control Pressure Warm - 3.4 - 3.8 bar
System Adjust Pressure - 4.7 - 4.9 bar
Fuel Injector Open Pressure - 2.5 - 3.6 bar

1979 930

Control Pressure Warm - 3.45 - 3.85 bar
Full throttle Enrichment - 2.7 - 3.1 bar
System Adjust Pressure - 6.2 - 6.5 bar
Fuel Injector Open Pressure - 2.1 - 3.2 bar
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Old 01-21-2010, 07:13 PM
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Good brainstorming going on. Also good thoughts on the next issue (setting AFR's) after I get the flow issue resolved.

For 79 SC
Control Pressure Warm - 3.2-3.6 bar (vacuum line attached) and 2.7-3.1 bar (vacuum line removed).

Here is another thought. Without the injectors in place the FD can flow more than enough fuel; thus, the limit is caused by the injectors. Is there a different injector other than the SC injector that will flow more? In particular, the 930 CIS injectors at over $100 a pop (930-110-225-02-M14, 930-110-225-00-M14) vs the SC's (911-110-225-01-M14) at $35 each. Anyone tested different CIS injectors? What about Volvo/Audi/Mercedes/Saab/VW?

My injectors are Bosch 0 437 502 004

Another good calculator of HP for a given injector, calculating injection in lb/hr to cc/min, and determining flow rate when you increase the pressure:
http://www.witchhunter.com/injectorcalc1.php4

Here are links on flow rates for different injectors. Unfortunately for me, they are for EFI injectors only with no data for CIS.
http://www.witchhunter.com/injectordata1.php4
http://www.fuelinjector.citymaker.com/page/page/4782443.htm
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Last edited by Dr J; 01-22-2010 at 05:51 AM..
Old 01-21-2010, 07:58 PM
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Maybe you could find a used 930 (3.0-3.3) CIS? I've seen them on e Bay and on the Pelican Parts forum, maybe even a Mercedes or Volvo system may cut it. Search for one matching your HP requirements, not your engine displacement.

Your current system simply is not going to cut it without extensive modifications.

Let's say you have a 200HP 3.0liter 911SC
Injector Flow Rate (cc/min) = Engine HP x BSFC x 10.5/Number of Injectors x Injector duty cycle

Injector Flow Rate (cc/min) = 200BHP x .45 x 10.5 / 6 x 1.0
Injector Flow Rate (cc/min) = 157.5 cc/min = 157.5ml/min

Look at the numbers for a Supercharged 300HP 3.0 liter engine. Keep in mind your BSFC will go up due to it being a supercharged engine.

Injector Flow Rate (cc/min) = 300BHP x .65 x 10.5 / 6 x 1.0
Injector Flow Rate (cc/min) = 341.25 cc/min = 341.25 ml/min

You have to more than double your injector output, at the same injector fuel pressure. Sure you could fiddle with your current system, but why? It will just cost you more in the long run, financially and psychologically.
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Last edited by WERK I; 01-22-2010 at 05:46 AM..
Old 01-22-2010, 05:44 AM
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Andial got 300 hp from a 3.7 with the same 79 CIS system, perhaps someone on the other list knows how this was done.
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Old 01-22-2010, 06:16 AM
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WinRice,

Thanks for the SC/Turbo numbers. Do you have the flow test quantity's?

Those number's seem to support our thoughts of setting the CP & SP at SC numbers and using a RR-FPR for boost enrichment. Might even be able to use the SC WUR.

Dave,

What happens when you run the 930's rate of 220ml? How much HP can it support?


-Are 930 and SC injectors the same size and interchangeable?


-If a stock SC puts out 200hp, Porsche would probably not put the fueling right on the edge. Many have bumped HP to 220-230 without issue.

For some reason using EFI calculations for a CIS dose not seem to add up. I am not a great at math but I could not get it to work using a 930's numbers.

-Sounds like the SC WUR has an acceleration fuel enrichment function if the CP goes down when vacuum goes away. That is great. This should let a stock SC run at near 14.7/1 on cruse and drop to about 13/1 with acceleration. We just need about 10% more fuel for an AFR that will support boost.

Not saying the total quantity will be there.

If one wanted to them might be able to mod it for a lower control pressure with acceleration. That was how the 3.0 turbo WUR used to work, on vac loss instead of with boost.

Still, I would get it togeather and test and then shim until it gets to good AFR numbers with acceleration.

Or shim the System Pressure about 10% now to about 5.5 bar in the hope for another 10% more fuel at all points and then when running fine tune it with further System Pressure adjustment and the CO adjustment screw.

JMO
Old 01-22-2010, 07:14 AM
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Keith,
The difficulty in comparing EFI injectors to mechanical injectors is in the very nature of their designs. Calculations for EFI injector output is based upon the duty cycle of the injector with the injector running at a specific fuel pressure. Mechanical injectors always run at 100% duty cycle but their volume is based upon a varying fuel pressure. Without specifications of the injector, it is impossible to determine if an injector (and the associated delivery system) is up to the task of providing the required amount of fuel.. I'm sure Bosch has injector curves based volume versus pressure, but it has been extremely difficult to find them anywhere.

There's no problem with the calculator in determining the fuel requirements. It's the problem of knowing whether the delivery system (in this case, CIS) can handle the increased demand, i.e. increased fuel pressure.
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Old 01-22-2010, 08:29 AM
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Quote:
Originally Posted by Dr J View Post
Here is another thought. Without the injectors in place the FD can flow more than enough fuel; thus, the limit is caused by the injectors. Is there a different injector other than the SC injector that will flow more? In particular, the 930 CIS injectors at over $100 a pop (930-110-225-02-M14, 930-110-225-00-M14) vs the SC's (911-110-225-01-M14) at $35 each. Anyone tested different CIS injectors? What about Volvo/Audi/Mercedes/Saab/VW?
Per the chart above, the CIS injectors need a certain pressure just to open, so they will always be a restriction. They really are nothing more than than a fancy check valve with a nice spray pattern.

I'm willing to bet the SC and 930 injectors flow about the same, the big difference is system pressure. You need to get your system pressure up, and make sure you fuel pumps can support that system pressure. Per WERK's charts, the SC and 930 front pumps are the same. If your stock pump is in good shape, add the 930 rear pump and play with your system pressure. After each system pressure adjustment, you will have to go back and adjust you WUR control pressures to get your AFR in line. With low levels of boost, you could probably get by with the lower limit of 930 system pressure, about 6.2 bar.

I like Werk's idea of just getting a 930 fuel system, may be cheaper and easier in the long run.
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Last edited by WinRice; 01-22-2010 at 08:59 AM.. Reason: Added info
Old 01-22-2010, 08:54 AM
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Tried two different things unsuccessfully.

1. Added a 1 mm shim to increase FD pressure by 0.6 bar. That worked. Pressure was 5.6 bar but flow was about the same. According to the calculator from the link above, I should have expected about 9 ml more fuel per injector. I'm not measuring that accurately to detect 9 ml so this might have worked, but it seems I would need to increase to 160 psi (10.9 bar) to get 220 ml. Obviously need a new fuel distributor unless another injector may cause more flow (I think the injector issue is still open although narrowed down, as I explain at the bottom).

2. Had a spare FD that had been lying around for a while. It looks like an early '80s. Cleaned it up a bit and installed it. Now got around 200 ml/min/injector at 5 bar system pressure. Just by looking, I could tell it was flowing much more. However, this FD has a problem that it won't shut off. Cylinders 1, 2, 4, and 5 are always sending fuel even with the airflow plate is horizontal (even depressed it below level and it still kept sending fuel).

On the injector issue, here is what I found after spending some time searching on the net.

According to this site: Injector Opbrengst Bosch has the following injectors 0-437-502-xxx, where xxx is 003-007, 010, 012, 013, 015, 018, 022, 023, 043-047.

I looked at the 0-437-502-xxx series because the 004 is for the '79 SC's which could produce up to 209 HP.

According to saft7.com > Print > Daftar Lengkap: Flow-rate Fuel Injector, you can find out which other vehicles used these injectors. Everything from Peugeot, Volvo, BMW, Saab, Mercedes, Audi, Bentley and Ferrari. I looked for the highest HP/cylinder and found-- you guessed it-- the Porsche turbos 3.0/3.3/3.6 as the highest, so it's not worth looking at injectors from other vehicles in this series.

A final link: http://ecat-online.bosch.de/toc/
Select your language, then go right underneath WEB CATALOG, where it says Search Via, select Article Direct Search
This is a Bosch link where you can enter the injector number and you can find what vehicles used the injector.

Nowhere did I find any flow tests for the CIS injectors.
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Last edited by Dr J; 01-23-2010 at 02:51 PM..
Old 01-22-2010, 07:54 PM
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Quote:
Originally Posted by Dr J View Post
Tried two different things unsuccessfully.

1. Added a 1 mm shim to increase FD pressure by 0.6 bar. That worked. Pressure was 5.6 bar but flow was about the same. According to the calculator from the link above, I should have expected about 9 ml more fuel per injector. I'm not measuring that accurately to detect 9 ml so this might have worked, but it seems I would need to increase to 160 psi (10.9 bar) to get 220 ml. Obviously need a new fuel distributor unless another injector may cause more flow (I think the injector issue is still open although narrowed down, as I explain at the bottom).

Interesting thread :-)

I've got exactly the same behaviour on my 1991 C2T while I made my CIS tuning. Although I shimmed the head to increase the system fuel pressure ( from 6.8 to 7.8 bar ), I didn't get more fuel.

I kept the same fuel pressure adjustement and then I changed the front fuel pump ( I upgraded to bosch 044) ..... then I 've got more fuel !

If my understanding is correct, you have one single fuel pump right ? There is absolutely no doubt that the 930 and 964 C2T setup with dual fuel pumps is able to provide higher fuel low rate under exactly the same system fuel pressure...


Now, if you need much more fuel , new injectors with higher flow rate is "the" solution !
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Old 01-23-2010, 04:42 AM
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Seeing some evidence of some special CIS Bosch R-Sport injectors when looking around.

We should not be afraid of fuel pressure. There are Bosch fuel pressure regs to 8 bar and fuel pumps that support up to 8 bar. MFI runs in the 230 PSI range. We just need the the pumps to keep up.


I suspect there is some weaknesses to the math formulas that predict how much HP can be supported by a give quantity.

First, we run turbo 10% or more richer than a N/A motor for cooling.

Secondly, we are usally injecting fuel under boost into a higher pressure environment which will reduce flow.

Thus, we might need to reduce the HP level potential by as much as 20% I would guess.


Some more goodies:

Quote:
Conversions

* 500cc per minute is approximately equal to 49lbs per hour which is equal to approximately 100hp.

* lbs/hour = cc per minute / 10.2

* lbs per hour = HP / 2.04

* cc per minute = lbs per hour x 10.2

* cc per minute = HP x 5

* HP = cc per minute / 5

* HP = lbs per hour x 2.04
Old 01-23-2010, 01:27 PM
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OK. Think I've spent enough time testing and have decided to do the following:

Continue assembling the engine.
Leave the higher pressure in the FD
Install the supercharger, to make sure everything fits and is in place.
Will not connect the supercharger to the intake. (grrrr)
Start the car and break it in as NA- I need the transportation!
Purchase a newer fuel pump like the 044 and install.
Check AFRs to see if it can support boost.
If so, connect the intake tubes from the supercharger (weeeee)
If not, look for a 930 CIS.

Any suggestions on which year or type of 930 CIS I should get? I'm thinking I would need the FD, the WUR, the steel lines, and the injectors.

Thanks
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Old 01-23-2010, 07:56 PM
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Originally Posted by WERK-I View Post
Maybe you could find a used 930 (3.0-3.3) CIS? I've seen them on e Bay and on the Pelican Parts forum, maybe even a Mercedes or Volvo system may cut it. Search for one matching your HP requirements, not your engine displacement.

Your current system simply is not going to cut it without extensive modifications.

Let's say you have a 200HP 3.0liter 911SC
Injector Flow Rate (cc/min) = Engine HP x BSFC x 10.5/Number of Injectors x Injector duty cycle

Injector Flow Rate (cc/min) = 200BHP x .45 x 10.5 / 6 x 1.0
Injector Flow Rate (cc/min) = 157.5 cc/min = 157.5ml/min

Look at the numbers for a Supercharged 300HP 3.0 liter engine. Keep in mind your BSFC will go up due to it being a supercharged engine.

Injector Flow Rate (cc/min) = 300BHP x .65 x 10.5 / 6 x 1.0
Injector Flow Rate (cc/min) = 341.25 cc/min = 341.25 ml/min
...

I might be able to start to understand the above as math is not my strong suit.

The BSFC has to do with the design and efficency of the motor and we have to adjust it for a forced induction motor. A low pressure motor probably uses about 10% more fuel than a N/A motor. Thus, a jump from .45 to .65 seems a lot more than I would guess and suggests such a motor needs 50% more fuel per every HP made.

Again, I am not a math wiz and I could be off on this.

So if a NA 200hp motor 'might' need 157cc/min (depending on how efficiently is operates or its BSFC),

a NA 300hp motor might then need 'about' 225cc /min if it operates at the same BSFC.

If a low pressure supper charged motor needs 10% more fuel than the N/A motor it seems it might need about 250cc/min.

Again, it depends on how much fuel the motor needs per HP and that varies.

How one get's there is the question. Changing an SC to Turbo specs it probably not going to be that simple and may be more than is needed as a 930 can supply enough fuel for about 400hp.

AFRs are a function of the injectors, system pressure, control pressure, spring tension around the internal orifices & there height, and the profile/programing of the metering cone and assembly. An SC metering plate is probably going to advance at a different rate on an SC than a turbo even with the same WUR specs.

It is going to probably be a trial and error exercise unless a used 930 intake system is purchased and it to will still need tweeking.

---

PS: Injecting fuel into a supper charged motor running about 70psi in to an pressurized manifold running at about 7 lbs boost will require a higher fuel delivery rating of about another 10% I suspect. Thus, the est of 225 goes to about 250cc/min.

This could be off if the est of BFSC is off.

Again, I could be off on some of this stuff.

Last edited by 911st; 01-23-2010 at 09:33 PM..
Old 01-23-2010, 08:47 PM
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Dr J.

Good general plan. If you do need more fuel, try lower control pressure and higher system pressure first. Then the fuel pump. Injectors & head next.

I would not think you would need the WUR. You will need custom control pressure settings and your pressure sensing WUR is probably a better fit with low boost suppercharger.

---

As you your variations with the second FD. Is the metering pin stuck?


Next, on the first FD the metering pin might not be traveling to its full potental. Check if when the metering plate is at full travel if the pin can move further.

Any easier way to check this might be to adjust the CO screw to an extreme rich setting and re run you quantity test. If you get more fuel, the pin is not going all the way.

On one of my turbos I had to detail the metering assembly to get full pin travel at some points of CO adjustment. At many points it did not mater, but at very lean CO settings I was not getting all the fuel I had available to me.

I guess what I am wondering is if the second FD was stored upside down and the pin froze at its max point and or if the first FD is not reaching its full delivery point.

Last edited by 911st; 01-23-2010 at 09:35 PM..
Old 01-23-2010, 09:31 PM
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Keith,
The formulas for calculating the flow injector requirements have been based on a generality, specifically BSFC. The .65 BSFC used in the forced induction example would be a worst case example. Turbocharged engines generally fall in the range of .55-.65 and supercharged engines fall in the range of .50-.60 for their BSFC's. Without the engine on a dyno, that number can't be more accurate. I'm afraid the 10% figure you suggest in increasing the fuel flow is a tad off. Increasing horsepower from 180-200 (depending which engine) to 300 is a 50% jump in power, just how are you going to generate that much of a jump with a meager 10% increase in fuel? Also, don't forget superchargers and turbochargers are parasitic.....to make power it takes power.

Without an engine dyno, this is all conjecture at this point. It can provide the BSFC for that engine being tested and modified. I would rather side on the margin of safety in using an induction system that was designed for forced induction than one that was not. We haven't even gotten into the weaknesses of the 911 SC CIS, such as the air box, warmup regulator and injector lines. None of which were ever designed for positive atmospheric pressures and fuel pressures that high. Does the owner have a "blow-off valve" in the air box? You know that has to go. 230PSI on those plastic injector lines? Good luck with that.
How does the fuel distributor behave with pressures that high? I don't want to hear, "it should be fine". There's nothing worse than seeing an engine running, suddenly being doused with fuel and catching fire.

Don't be afraid of the math.....it is your friend, some say it is god.
You have to use it to get in the ballpark in building an engine meeting your target goal. If all you use is conjecture, it will wind up being very costly in time and money and customers. Turbo maps, injector flow rates/characteristic, fuel pump curves are put there for a reason. Use the math. It is your friend.
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Dave
'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 01-24-2010, 05:09 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #59 (permalink)
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Quote:
Originally Posted by 911st View Post
WinRice,

Thanks for the SC/Turbo numbers. Do you have the flow test quantity's?
Sorry Keith, no injector flow rates, which is a little surprising.

I have the small white Porsche spec book for 78-81 SC and Turbo and it has every spec you could think of, except that.

It does show the minimum fuel system flow rates:

SC - 1000cc / 30 sec
Turbo - 1500cc / 30 sec
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Old 01-24-2010, 08:19 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #60 (permalink)
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