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Quote:
Originally Posted by Dr J View Post
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.
Not necessarily, you may be hitting the flow limits of your pump.

Look at the charts below, I couldn't find a chart for your 053, but the 979 is close:






Once you hit around 5.5 bar the flow rate drops drastically, and the current demand goes way up, indicating the pump is maxed out in efficiency.

Now lets look at the 044



You should be able to run that pump at 6 - 6.5 bar fine, giving a flow rate around 3.3 L/min (1650cc / 30 sec), which is close to the 1500cc / 30 sec given by the factory 930 system.

Also notice the big flow rate drop after 7.5 bar, if you need more than 7.5 bar with a good flow rate, a series pump system like the 930 is the way to go.

More pump info:

Bosch and Lucas Fuel pumps
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Old 01-24-2010, 08:54 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #61 (permalink)
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Dave,

I love trying to overlay math to bracket concepts. However I am limited to a degree. I can use compute the length around a circle and use it to figure out how much to change the angle of a rear arm but I can not use that co-sign stuff.

What I did was take the 200hp number you came up with, increased it 50% to aproxamate a 300hp N/A motor and then added 10% for the extra fuel I guessed we would need for a low pressure supper charger.

That is kind of like moving the BFSC from the .45 to .50. It sounds like .the .50 is at the lower end of the supper charger range.

Then in the PS I tryed to recognize that CIS dose not have any compensation built in to alow for the resistance that will be created trying to inject pressurised fuel into a pressureized intake that will thus reduce the flow rate. I did miss the extra 35hp that the supper charger will have to to see to net 300. Thus, we need another 10% for that. So about .45x1.1x1.1x1.1= might equal .60 which is closer to the number you picked .

In all a semi-educated guesstimation.

Per you numbers it looks like we need about 476cc/min to 682cc/ min to support 100hp.

Some one else I read noted a CIS rule of thumb that it took about 500cc /min to support about 100hp. So we seem to be in the ball park.
Old 01-24-2010, 09:21 AM
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Originally Posted by WinRice View Post

...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
Great info! Same for the fuel pump flow / amp.

So that would be

SC - ---2000 cc/min, and
Turbo -3000cc/min

In the real world we know the turbo suports up to about 400hp at one bar using only a reduced control pressure.

I have alwas believed that the metering plate stalls even with a control pressure of under 2 bar and that there is more fuel to be had. I learnd of this potental from a conversation with Lee Rice of the Rice Fueler. He said he had a 930 at full tilt on a dyno and was able to push the plate down even further and flood the motor even though the control pressure was already lowered to the max.

This seems to be supported even using Daves higher fuel rate of 642cc/100hp. That would indicate a 440hp potential.

Thus, the stock SC looks like it has enought fuel to support 312- 400hp (500cc to 642cc/ min per 100hp).

-----

So what would I do.

The cheapest way to get more fuel out of a CIS motor is to shim the fuel head. However, that can effect AFR's at points other than max HP.

The next and most taken rout is to lower Control Pressure. One can use a 930 WUR but it will probably still need to be adjusted to fit the air flow / metering of the SC system.

I would probably play with the SC WUR and mod it so with vac goes away, the CP is lower so it functions like a 75-77 3.0 Turbo WUR.

There is the option of using an Anidal fueler or a frequency valve to bled off control pressure or get a D-WUR for the ultimate in CIS AFR tuning.

If a combination of those two do not work I would then look at the head. One could try to source a good used 930 unit but I would probably just send it to Larry at CISFLOWTECH to have it rebuilt and calibrated for more fuel. He did the very first HF FD at my request about 7 years ago and later all the HF fuel heads for IA. He can also rebuild and reset you WUR to 3.0 Turbo or any other settings you might want.

This way one would have a known fresh FD and one that will do what it needs to.

Last edited by 911st; 01-25-2010 at 06:40 AM..
Old 01-24-2010, 09:55 AM
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Couple more clues else where on the Gold injectors. May just be a 930 injector in a Volvo body.

Bottom line is they were not getting any more HP per cylinder than some CIS 930 owners are.

Cis monster

With the Volvo race program they noted 600cc + flow from the Gold injectors. However, they ran them at 8 bar!

If we are getting 500cc at 6.2 to 6.5 bar, 600cc at 8 bar might be about right.

They note dual high pressure fuel pumps to get there.

If this is the case, we have a lot of fuel capacity left with pumps and more system pressure.


They also note different cones to tune the air sensor plate for ideal AFR's.

More clues.
Old 01-24-2010, 03:56 PM
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Based on a calculator in a link earlier in this post, with 6.2 bar at 500 cc, it predicts 568 cc at 8 bar.

My previous research shows that the 930s had the best HP/injector for the CIS system.

Now to find where to get one of these gold ones. There are some but I don't think they are the same. Searching bosch gold injector on ebay yields an injector for a Mercedes 300 SEL, 300 TE, 260 E with a Bosch part number of 0437502047. I doubt this is the same thing; although, many on the 928 side are happy with them. MB Injectors

The Bosch site has these injectors linked to Ferraris. But again, 930 has more hp/injector.
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Last edited by Dr J; 01-24-2010 at 07:29 PM..
Old 01-24-2010, 06:51 PM
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Dose an SC use a screw in like a 930 or a snap in like the MBZ...?

This might effect your choice.

The grand dad of CIS flow is the Bentley Rolls FD. It is at lease an equal per cylinder to the 930 but I do not know if it is more.

I suspect there are some trade offs with a larger injectors. They may support more flow but there may be some compromise as to atomization at lower speeds. This may or may not effect low end operation and emissions.
Old 01-25-2010, 06:46 AM
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An SC injector snaps in with the O-ring; it is not screw-in.

I agree with your statement on the atomization, but if they open at something like 3 bar, then that should be good enough.
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Old 01-25-2010, 02:21 PM
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So do the gold's it seems. If they can be had they might fit on an SC.

I bet you could get a turbo injector from someone here and test it against your SC injector on your system doing the flow test to see if a larger injector is going to be of any benefit (or if the 930 is larger). That would be a very good data point!

Still, almost no one has used injectors as a path to more fuel from anything I have seen in the last 10-12 years on turbo boards. That dose not mean it will not work.

Most get more fuel from lower control pressure first (Rice Fueler, Andial Fueler, BL w RPM delay, D-WUR...), higher system pressure second (Chris Fisher, SW...), and probably then readjusted HF head (my invention). One advantage to a HF head is it is then known to be in great shape and balanced.

Fuel pumps are a different issue.

It seems there should be plenty of fuel with the SC head /injectors by lowering control pressure with acceleration. A DIY'r can do this by playing with the WUR and or doing some research and tinkering with the WUR or looking at the Audi, Volvo turbos, 930 or other WUR's.
Old 01-25-2010, 03:01 PM
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Dr.J,

Did you check if your metering pin is seeing full engagement when the plate is pushed down all the way?


Also, under the screws on the FD next to each exit there is previsions for flow adjustment.

You may be able to get more fuel by changing the adjustments. This changes the spring pressure around the internal orifices. Increased spring tension increases differential pressure between the upper and lower chambers and more fuel flows past the diaphragm.

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Old 01-25-2010, 05:01 PM
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For what it is worth Bruce Anderson's book on modifying Porsches has some info on supper charging the SC. It dose not say anything about fueling but they did say Supper Chargers of Knoxville used MSD with boost retard on the ignition side.

They also used a strategy of using a pulley for a little higher boost and using a blow off valve to set boost lower. For example they would set the pulley for 10 lbs and set the blow off valve for 8 lbs.

This make sense as a SC makes boost as a function of rpm with low boost at idle increasing in a mostly straight line. This might help mid range some I guess.
Old 01-25-2010, 08:28 PM
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For what it is worth Bruce Anderson's book on modifying Porsches has some info on supper charging the SC. It dose not say anything about fueling but they did say Supper Chargers of Knoxville used MSD with boost retard on the ignition side.

...................................edit to save space...................
Really? All I saw were the examples for Carrera 3.2's. Was this the old Anderson book or the new one?
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Old 01-26-2010, 03:30 AM
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Second Ed.
Old 01-26-2010, 06:26 AM
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Based on Stu's post for adjusting flow, (Meter head flow adjustment question??) I believe I should be able to adjust the flow on my injectors through the screws (marked with the yellow lines) next to where the banjo bolts from the fuel lines connect to the fuel distributer. Any comments or suggestions before I take a screwdriver to it?

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Old 02-08-2010, 10:45 AM
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Originally Posted by 911st View Post
Dr.J,

...Also, under the screws on the FD next to each exit there is previsions for flow adjustment.

You may be able to get more fuel by changing the adjustments. This changes the spring pressure around the internal orifices. Increased spring tension increases differential pressure between the upper and lower chambers and more fuel flows past the diaphragm.
Old 02-08-2010, 11:04 AM
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..........................edited for space..............
Any comments or suggestions before I take a screwdriver to it?

Don't do it?
Unless you're certain the FD is 100% healthy and in spec., I wouldn't recommend it. You may be be masking over a problem that's there, like fuel debris, corrosion, wear, etc. My $0.02, get it rebuilt or exchange for rebuilt from reputable shop, then tinker with fuel flow.
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Old 02-08-2010, 11:23 AM
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Excellent, thanks. The FD is in great shape. It is a rebuilt unit that is working fine. The reason for the adjustment is because I am supercharging and need more fuel.
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Old 02-09-2010, 08:20 AM
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If the screws are real tight and it seems like the screwdriver slots are going to distort and slip than try PB blaster and gentle use of an impact wrench with flatblade screw bit installed and light taps with a hammer to get them loose.

The 930 fuel heads have 4mm round head allen head bolts there instead of flat blade screw slots.

With them out you'll see 3mm allen head adjustments underneath. They are the spring tension adjustments.
Turn them clockwise a little bit at a time to put more pressure on the diaphram to push it down and let more fuel pass by the small clearance between the top side of the diaphram and the bottom of the orifice thats below the fuel injector line banjo bolt.

Your fuel head looks like an older cast iron one with a stainless steel diaphram in between the top half and lower half of the fuel head so if you go too far with those spring tension adjustments you may dent the diaphram and then it will need to be replaced to meter fuel correctly.

The aluminum USA fuel heads use a white colored synthetic diaphram material that is more flexible than the older stainless steel diaphrams used in the cast iron fuel heads.
From what I've heard... this more flexible diaphram is why the lighter cast aluminum lambda fuel heads can be modified to flow more fuel than the older cast iron fuel heads with their stiffer stainless steel diaphram.
Old 02-09-2010, 08:50 AM
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I would personally adjust to calibrate even flow to each cylinder but NOT to try and gain more fuel as a whole!

I would go down a different route to try and acheive more fuel to your cylinders then slightly adjust via head only if fuel flow is uneven to each cylinder.
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Old 02-09-2010, 11:07 AM
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The nice thing about it is if he doesn't like it he can turn the adjustment screws back to where they were.

This and raising system pressure is part of modifying a fuel head to deliver more fuel to the injectors, and this doesn't return fuel to the tank to do that.
Old 02-09-2010, 01:55 PM
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JFairman, what do you think would be a max turn? 1/4 turn? 1/2 turn?
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Old 02-09-2010, 06:40 PM
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