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I would rerun the test with a controlled 14 volts over a longer period of time. Pump volume varys considerably with voltage and the pump never runs at a falling 12 volts on a running car. MSD shows a 35% drop in FP delivery when the voltage drops from 13.5 to 10.
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Old 01-18-2010, 03:48 PM
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Originally Posted by WERK-I View Post
I was able to find a Bosch Fuel Pump Spec Sheet, if anyone is interested.

Thought I would add yet another chart for cross reference.

This chart shows the Bosch Part Numbers for Fuel Pumps.

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Old 01-19-2010, 07:33 AM
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Dave,

That info is to valuable to remain hidden in this post. I hope you do not mind but I reposted it in the 930 section.

CIS Fuel Pump Options for more fuel!
Old 01-19-2010, 08:24 AM
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Saw the new post. It is a good thread.

Paul, I upped the voltage as you suggested. It seemed that if flow was increased, that would tell me to source a new pump based on the data in Dave's post. I did not have 14V but did have 15.6V from a battery charger set on the jump start setting. You could here the pump vibrating at a higher frequency so it felt the juice. Here is what I got:

Volt 15.6, System pressure 5.4 bar (it increased from 5 bar), temperature 19C/67F

Result: same flow in all injectors about 160 ml/min

This must mean that most of the extra fuel was once again dumped into the fuel tank. Only thing left to do is play with the control pressures and see what happens.
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Old 01-19-2010, 02:38 PM
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Delivery to the injectors is also effected by the differential pressure valves and the lower chamber pressure. This is how CIS lambda effects injector delivery, maybe your test method is altering the lower chamber pressure. The chart suggests your fuel pump should support +450 hp, although some of the figures, especially the 944 turbo pump, look incorrect to me.
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Old 01-19-2010, 03:54 PM
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Good point. If it is a Lambda style FD you need the computer active and the O2 unplugged so the frequency valve sets to 50%.

If this is not done, it will under perform.
Old 01-19-2010, 05:42 PM
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It's a '79 so no Lambda. Any suggested changes to the test method? Which chart are you talking about?
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Old 01-19-2010, 05:48 PM
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Quote:
Originally Posted by psalt View Post
Delivery to the injectors is also effected by the differential pressure valves and the lower chamber pressure. This is how CIS lambda effects injector delivery, maybe your test method is altering the lower chamber pressure. The chart suggests your fuel pump should support +450 hp, although some of the figures, especially the 944 turbo pump, look incorrect to me.
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Originally Posted by 911st View Post
Good point. If it is a Lambda style FD you need the computer active and the O2 unplugged so the frequency valve sets to 50%.

If this is not done, it will under perform.

Could we stay on topic here? We're trying to wind-a-watch, not build one, metaphorically speaking.
DrJ has a '79 911 SC with no Lambda. He wishes to add a supercharger to the engine.

We are trying to figure out how to insure the existing fuel delivery system, fuel pump, fuel distributor, warm up regulator, lines and injectors can meet the task of delivering a targeted 300HP.
Problem: the injector sizing calculator doesn't seem to provide the proper answer. Which means either the calculator is wrong, the methodology of the test is at fault or something is amiss with the fuel delivery.

We now return to our regular scheduled programming.........
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Old 01-19-2010, 06:03 PM
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Quote:
Originally Posted by psalt View Post
Delivery to the injectors is also effected by the differential pressure valves and the lower chamber pressure. This is how CIS lambda effects injector delivery, maybe your test method is altering the lower chamber pressure. The chart suggests your fuel pump should support +450 hp, although some of the figures, especially the 944 turbo pump, look incorrect to me.
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Originally Posted by Dr J View Post
Saw the new post. It is a good thread.

Paul, I upped the voltage as you suggested. It seemed that if flow was increased, that would tell me to source a new pump based on the data in Dave's post. I did not have 14V but did have 15.6V from a battery charger set on the jump start setting. You could here the pump vibrating at a higher frequency so it felt the juice. Here is what I got:

Volt 15.6, System pressure 5.4 bar (it increased from 5 bar), temperature 19C/67F

Result: same flow in all injectors about 160 ml/min

This must mean that most of the extra fuel was once again dumped into the fuel tank. Only thing left to do is play with the control pressures and see what happens.
DrJ,
The source of power for your test could be a fully charged battery with a charger, capable of delivering 15-20Amps should suffice. I believe the voltage normally is around 13.8vDC. Its good all injectors are delivering the same 160ml/min volume. I suspect they would deliver that same amount at 13.8volts.

You are right about the remaining fuel being returned back to the tank. There is a pressure relief valve that controls this function in the fuel distributor. Shims are used to elevate the pressure, which will elevate the pressure at the injector. I'm a little nervous about raising the pressure on your application since the 911 SC injector lines are plastic. I'm sure they're over-engineered as most everything else is by Porsche, but just be aware.

Because the SC is normally aspirated, the Warm up Regulator does have its limitations. It has no ability to adjust for boost as the 930 WUR does. The 930 WUR lowers the control pressure in the head when it begins to sense boost. Maybe a different approach will be necessary when it comes to a self-adjusting control pressure regulator(WUR)?
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Old 01-19-2010, 06:42 PM
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It's a '79 so no Lambda. Any suggested changes to the test method? Which chart are you talking about?

Dr J,

There is more to fuel delivery at the injectors than height of the plunger. There is a differential pressure valve after the plunger slit and before the injector line. If your test method plumbing effects the pressure in the lower chamber, the amount of fuel at the injector will be different. My point about CIS lambda is that it controls the amount of fuel at the injector by varying this pressure with the FV pulses. The range of the delivery amount is quite large. If the lower chamber pressure is higher in your test than under running conditions, delivery at the injector will be lower. Have you tried the test with all the fuel lines hooked up normally and no test valve ?
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Old 01-20-2010, 03:31 AM
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Quote:
Originally Posted by psalt View Post
It's a '79 so no Lambda. Any suggested changes to the test method? Which chart are you talking about?

Dr J,

There is more to fuel delivery at the injectors than height of the plunger. There is a differential pressure valve after the plunger slit and before the injector line. If your test method plumbing effects the pressure in the lower chamber, the amount of fuel at the injector will be different. My point about CIS lambda is that it controls the amount of fuel at the injector by varying this pressure with the FV pulses. The range of the delivery amount is quite large. If the lower chamber pressure is higher in your test than under running conditions, delivery at the injector will be lower. Have you tried the test with all the fuel lines hooked up normally and no test valve ?
Just my simple opinion

Actually, when the FV valve is triggered (50 to 75%) , it takes about 150 to 250 ml of fuel flow back to the tank ... this flowed fuel volume is no more availabe for the injectors !!!

So you reduce the upper valve restriction (différential pressure) .... but finally you draw more fuel back to the tank.

If the max injectors fuel flow is limited by the fuel pump flow rate capability.....

- you gain nothing by acting the FV on the max injector flows ( at fully metering plate deviation) .

- you gain nothing by increasing the system pressure.
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Old 01-20-2010, 12:02 PM
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If the max injectors fuel flow is limited by the fuel pump flow rate capability.....


In this case, the fuel pump should be good for +400 hp, but the measured ouput of the injectors is only good for 160 hp.

If the airflow sensor is held to it's limit, control presssure should be out of the picture. Lower chamber pressure is one variable that could reduce delivery to the injectors.
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Old 01-20-2010, 01:45 PM
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Ok, what I am getting from the posts is to disconnect the CIS gage and its valve, then put the original line to the WUR and repeat the test. Easy enough to try.
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Old 01-20-2010, 02:18 PM
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I must have missed it. What is an SC supposed to test at?

Per the following a 930 is in the 240ml range.

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Originally Posted by stup View Post
....
At wide open meter plate with injectors FITTED my car flowed between 120ml-124ml per 30 seconds(tested twice and results the same both times)..approx all within 3% at WOT...Copied that from earlier,,hope that helps...tested control pressure flow rate also and it was towards upper limit of specs 160-240ml per minute...i was at 220ml..that was the fuel line into the wur...
Ok, you are getting 150ml.

Upper end of the spec for a 930 seems to be 240ml.

If 240ml supports up to 400hp, then 150ml would support up to about 250hp on boost.

On top of that a 930 runs at about 11/1 AFR and an SC at about 13/1 AFR so this might be enough fuel for up to almost 300 N/A HP.

That would be about a 50% margin so it seems like the FD is functioning correctly considering is was fitted to a car that was to make about 200hp.

If the boost level is kept to 6 psi and 300hp is expected at an AFR of 12/1 it will probably be close.

If so, you might then be able to shim the system pressure to get to where you need to be.

Shimming to increase system pressure dose increase fuel delivery as long as the fuel pump is not over worked. If there is still fuel returning to the tank, the pump is fine.

System Pressure can be tested as the same time the test is made without any issue during the flow test and is a good idea.

This is not a Lambda head so this dose not complicate things.

Have not been following closely so if I am off base, sorry about that.

Last edited by 911st; 01-20-2010 at 04:07 PM..
Old 01-20-2010, 03:53 PM
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You're not off-base at all. Actually, it is an excellent answer. May just need to up the pressure a bit and I'm good to go. This delay has been placing my supercharger project on hold for about two weeks. Thanks.
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Old 01-20-2010, 05:56 PM
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Per the Porsche Technical Spec Manual

The US SC head has a system adjust pressure of 4.7 - 4.9 bar
The 930 head has a system adjust pressure of 6.2 - 6.5 bar early turbos, 6.9 - 7.1 bar late turbos

The first thing you need to do is get the fuel system up to the task with a larger single pump, or a dual 930 pump system. Then you need to shim up the fuel head to get a system pressure of 6.2 - 7.1 bar minimum.

One of the reasons the 930 uses a two pump system is the pressure boost you get from series pumps to get the high pressure (7.1 bar = 103 psi) needed by the CIS under boost. Most single pumps have a big drop in flow rate at those pressures.
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Old 01-20-2010, 07:21 PM
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You can try to copy a 930 by going for the same system pressures and use a 930 WUR to control it. This will probably require you to copy the 930 fuel pump set up as noted.

I hope you will have a wide band O2 so you can monitor in real time.

If so, what I would do is set it up and get it running and see what you have.

You might just be able to set the CO adjustment fat and get close.

If that dose not do it, then start shimming for more fuel.

Shimming will change the slope of your AFR curve if you leave your WUR stock. That is if you shim it for 10% more fuel, it will give you 10% more every where. You can pull the AFR back at idle but then all points past that will start to get rich.

If you get lucky the shimming will change the slope of the AFR curve enough that you do not need to change to a WUR that has enrichment.

Supper chargers are more liner than a Turbo so you might bet lucky and be able to tune your motor by only playing with system pressure.

Here is my thinking.

If you shim it about 10 to 15% more fuel you will get that much more fuel at all points.

Thus, you can set your AFR at 14.5/1. At curse (say apx 50hp) it might then be at something like 14/1. Then at 200hp WOT be in the 12's.

Your goal being to be at about 11.5/1 at TQ peak.

The AFR curve is just that, a curve. The metering plate moves quite a bit at first with changes in air flow. Latter in the cycle because of the design of the metering area and the angle of the metering arm to the metering pin, it starts to move slower the the AFR curve starts to turn. If you are lucky you will get the richest AFR at TQ peak as that is where you are most at risk.

Timing is the other thing. At full power you might want to start at about 16 to 18 deg advance and add more in a bit at a time. Your goal is about -10 at idle, -18 on boost above 3500rpm, and -30 or so at curse.

I am not a real expert so do this at your own risk but this is what I would do.

Good luck. This is an interesting project.

Last edited by 911st; 01-20-2010 at 08:22 PM..
Old 01-20-2010, 08:19 PM
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Isn't 160-240 the control pressure delivery rate, not the injector delivery spec ?
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Old 01-21-2010, 02:55 AM
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Paul,

Good question. I read through stup's thread as well as I could and did not see where he stated the factory spec for the injectors.

Thus, it would be good to verify both the SC and 930 spec's.

However, he said his injectors flowed 120-124 per 30 sec which is 240-250. He also clearly states his control pressure flow rate was 220/min.

Again, it would be worth checking. However, I would still probably try to just get this thing back together and see what there is to work with. CIS fuel distributor's do not like to be stored wet and that can create issues. However, he seems to have effectively flushed it and is flowing equally so it is probably flowing as well as an SC head can.

I do not know what boost Dr. J is going to get with his supercharger. However, if he dose run 6 psi it will start out with boost at idle and build with RPMS. That is a bit different than how a turbo build boost.

If the motor is a 8.5/1 CR and runs 6 lbs, it will be an effective CR of about 10.1/1. A stock 930 is about 10.2 so the AFR's need to build progressively with boost.

The cheapest way would probably be to keep the stock WUR and try to adjust around it and or bump the system pressure.

Getting a D-WUR or a controller and a frequency valve to manipulate control pressure would be more accurate but more expensive.

I would not expect perfect AFR's but CIS dose not deliver them even on a stock car. It just might run a little fat on cruse.

At least that is my guess.

Last edited by 911st; 01-21-2010 at 07:27 AM..
Old 01-21-2010, 07:24 AM
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Another approach to try might be to plumb a Rasing Rate Fuel Pressure after the return line and the WUR return after that. I think Vortec and Bell both have them. The simple Vortec would probably be the best as it dose not set a floor pressure I believe as that would be kept by the FD.

This would keep the cruse AFR stock SC and with boost increases the System Pressure would increase as the boost increases.

50hp at curse at 8.5/1 CR or 50hp at WOT and 10.1 CR would then get different AFR's.

The other way to go is a 930, Volvo Turbo, or Audi turbo WUR that has enrichment. But these do not trigger until about 5psi I think.

Might just be crazy thinking.
Old 01-21-2010, 07:34 AM
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