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Bad LT
 
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Go to guy for modified fuel head / CIS advice.

So I've maxed out the adjustable WUR and have cranked up the fuel pressure as far as I dare (10.2@1,000rpm) but still need more fuel at 5500+ rpm. AFR gauge is telling me 12.5 at 5,500 and 13+ to 6.500rpm.
The right balance for the CSV seems to be 4200rpm with full boost coming on at bang on 3000rpm.
Everything else is just fine but I just can't get enough fuel a higher RPM.

Am I missing something or is the answer a modded fuel head? I'm good with EFI but CIS is still new to me.


Specs are,
87 3.3ltr
K27.
Fabspeed headers with Zork tube.
B.L WUR.
Andial Cooler.
1 bar spring.
K&N Filter on the metering plate.
100RON fuel.


Last edited by Uncle; 11-17-2014 at 03:46 AM..
Old 11-17-2014, 03:41 AM
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Crotchety Old Bastard
 
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If you are running the -145 aluminum fuel head with Lambda the answer is yes you need to have the fuel head modified for more flow. The Lambda system will be eliminated. I try to keep these in stock if you want to swap out what you have.
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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 11-17-2014, 03:47 AM
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Bad LT
 
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Will check part number but it's an alloy job for sure.
Old 11-17-2014, 03:58 AM
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Bad LT
 
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So been racking my brain with this all day thinking I must of missed something.
I’ve lowered the full throttle enrichment pressure as low as I can get it (IE insert is all the way out) but am still too lean.
What I have not done, as I don’t have a CIS pressure gauge, is adjust the warm pressure 4mm Allen screw within the instert.
Am I correct in thinking if I decrease the warm pressure I should see an overall increase to a richer condition though out the rev range or have I got it backwards?

Warm Enrichment pressure is now set at 3.65 bar
Enrichment pressure was at 2.5 bar but would be less now.

Last edited by Uncle; 11-17-2014 at 05:43 PM..
Old 11-17-2014, 04:31 PM
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Quote:
Originally Posted by Uncle View Post
So I've maxed out the adjustable WUR and have cranked up the fuel pressure as far as I dare (10.2@1,000rpm) but still need more fuel at 5500+ rpm. AFR gauge is telling me 12.5 at 5,500 and 13+ to 6.500rpm.
The right balance for the CSV seems to be 4200rpm with full boost coming on at bang on 3000rpm.
Everything else is just fine but I just can't get enough fuel a higher RPM.

Am I missing something or is the answer a modded fuel head? I'm good with EFI but CIS is still new to me.


Specs are,
87 3.3ltr
K27.
Fabspeed headers with Zork tube.
B.L WUR.
Andial Cooler.
1 bar spring.
K&N Filter on the metering plate.
100RON fuel.
Are there other modifications? Is it the one bar spring that makes it lean?

I have a pretty similar set up...
88 3.3, k27, andial inter cooler, pretty open exhaust, and had a 1 bar spring but went back to stock...

Mine runs rich...

Hmmm. I am starting to wonder if the po modified the crap out of it... He had an adjustable boost valve on there and a bunch of other crap...

But in your set up, why wouldn't stock flow be adequate???

What afr are you shooting for at full boost? I see some folks shooting for 12.5 or so, yet when folks post videos I see the afr briefly dip below 10....

Bo
Old 11-17-2014, 05:15 PM
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Bad LT
 
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Yeah I thought the stock head would cope with it hance why I think I've missed something.

I'd like to shoot for an AFR of at least 11's

Last edited by Uncle; 11-17-2014 at 06:27 PM..
Old 11-17-2014, 05:48 PM
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Crotchety Old Bastard
 
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A little more detail is needed. The practical limit for the stock system is around 375whp at best.
Which K27 are you running?
Do you know the whp?
Any data on the AFR curve?
Is Lambda active or disabled?
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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 11-17-2014, 06:39 PM
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You can get more fuel by turning the little allen head diaphragm spring tension adjusters under the button head screws on the fuel head a little but if you havn't done that before and don't have a fuel head flow bench that's hit and miss and it's real easy to screw it up.

The place to go is:
CIS Flowtech - Rebuilding Bosch Fuel Distributors & Warm-Up Regulators
Or get in touch with Brian. He gives good service and he's here to help every day.
Maybe he has a CIS Flowtech 007 modified aluminum fuel head in stock.

Larry Fletcher at CIS Flowtech does more than just adjust the 3mm allen head screws he also replaces all the old orings with new ones that can handle ethanol in the gasoline and does some orifice machine work inside the fuel head if you want 20% or more fuel up top. He may remachine the metering slits in the control plunger cylinder wall too.

Won't be cheap but he does good work with a warranty and if your fuel head has never been rebuilt and has been run with E10 gasoline for a while the original orings may be swollen or rotting and the thing will need to be cleaned out and flowbench adjusted anyway.

You already have the BL adjustable control pressure regulator so you can lower boost control pressure more than stock for more fuel and fine tune steady cruise control pressure and that's a good thing.

You need a 100psi CIS fuel pressure test gauge with ball valve like this one if you want to get into tuning it.
Star Products TU-14PB Fuel Injection Tester - Bosch C.I.S. STATU-14PB
Old 11-17-2014, 07:10 PM
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Bad LT
 
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Can't give you exact spec's on the K27 as the tag is missing. P.O fitted it.
RWHP before B.L WUR,Fabspeed headers and Zork was 287RWHP. We only did one pull as we could see that the AFR’s going way too lean for comfort.



Post B.L WUR and headers the car is puling like a champ. I’ve got the RPM CSV set at 4,200RPM so it’s sitting on ~mid 12 AFR then leans off again once past 5,500. Once we saw it hit 14.2@6000rpm we called it a day.

There was no 02 sensors in the stock headers when I got the car so I’m going to say no lambda.
Old 11-17-2014, 07:14 PM
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In such a scenario, can the lambda frequency valve be broken? Plugged in or not, this think is buzzing. It seem slike this regulates back pressure on the same circuit as the WUR???

Does removing the valve make a difference? Replacing it? This may help you.

I almost never see any posts on here about this frequency valve, but it must have some kind oif failure mode.

Bo
Old 11-18-2014, 04:20 AM
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Crotchety Old Bastard
 
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Lambda failure mode is rich.
Measure the fuel pressure with boost applied to the WUR and correlate with AFR. Could be your threshold setting is off or you are simply running out of fuel.
Old 11-18-2014, 06:56 AM
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The lambda valve is an inline fuel injector that is opening and closing in pulses. Thats the buzzing sound and it's returning fuel from the lower differential chamber or bottom half of the fuel head to the gas tank.
System pressure fuel feeding the lower chambers has to go through an orifice so returning some of it faster than it can be replenished will lower the pressure.

Removing the lambda valve and plugging the inlet line to it line on one end and installing a shorter banjo bolt on the return line side of it will stop the return of fuel and increase lower chamber fuel pressure little and that will push the diaphragm that seperates the upper and lower chambers upward.

[The control pressure regulator is a seperate circuit that shares the same small 10x1mm thread return line banjo bolt.
The fuel is returned there so it goes through a small fuel pressure valve in the middle of the system fuel pressure regulator valve so it holds system fuel pressure after the fuel pumps are shut off.]

As the diaphragm flexes up a little it closes off or restricts the opening of the bottom side of the 6 final fuel metering orifices that lead up to the injector line fittings.
That will lower fuel flow and fuel pressure to the fuel injectors.
There are also 6 little springs - one around each final metering orifice pushing down on the top of the diaphrahm with 3mm allen head adjustment screws that adjust the spring pressure.

Failure mode of the lambda valve inline injector could be stuck open letting too much fuel return to the tank instead of the pulsing open and closed action it usually does (the buzzing sound) or stuck closed and then it would not be returning any fuel to the gas tank.

Stuck open would drop the lower chamber fuel pressure lowering the diaphragm a little which would let more fuel by the clearance between the top of the the diaphragm and the bottom of the 6 final metering orifices and stuck closed or unplugged so it isn't buzzing or pulsing and returning fuel to the tank from the lower chambers will raise lower chamber pressure pushing the diaphragm upward a little closing off the clearance between the top of the diaphragm and the bottom of the 6 orifices and that will reduce the amount of fuel going to the injectors a little leaning out the AFR a little.

This is all happening after the airflow meter has moved the control plunger up or down in it's cylinder exposing more or less of the 6 vertical fuel metering slits in the control plunger cylinder wall leading to the upper differential chambers in the top half of the fuel head.

If you could see a cross section diagram of the inside of the fuel head with arrows showing the orifices and fuel flow through the inside of it, it would be easier to understand whats going on.
Old 11-18-2014, 07:42 AM
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Really nice description . Thanks for the detailed response.


So falure of the frequency valve CAN cause a lean or rich condition based on what you just posted. That would make sense, as it can effect control pressures.

So how does he check the frequency valve for function? Is the fact that its buzzing mean that its working?

Sounds like removing it would lower control pressures, lower the amount of fuel being returned to the tank, and increase fuel flow to the injectors.

This begs the question, if all of the above is true, why haven't people gotten rid of the valve in their search for more fuel flow?

Seems way easier that modifying the fuel head...

Bo
Old 11-18-2014, 08:16 AM
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Trying to get this to post...
I've forgotten the best format to do multiple replies in one post so...

Quote:
Originally Posted by bpu699 View Post
Really nice description . Thanks for the detailed response.


"So falure of the frequency valve CAN cause a lean or rich condition based on what you just posted. That would make sense, as it can effect control pressures."

>The lambda frequency valve is in a completely seperate fuel flow circuit frm the CPR and has nothing to do with it.

"So how does he check the frequency valve for function? Is the fact that its buzzing mean that its working?"

>It's an inline fuel injector returning fuel from the lower chamber or lower half og the fuel head to the gas tank.

"Sounds like removing it would lower control pressures, lower the amount of fuel being returned to the tank, and increase fuel flow to the injectors."

>The lambda valve has nothing to do with the hydraulic control pressure level on the top side of the control plunger. Hydraulic control pressure is being regulated up or down by the CPR/WUR returning some of that fuel to the tank.
Fuel flow to the different parts of the bosch k jetronic system is seperated by fuel flow orifices leading to these seperate systems.
fuel pressure in these seperate systems is regulated by returning some of it to the gas tank.

"This begs the question, if all of the above is true, why haven't people gotten rid of the valve in their search for more fuel flow?"

Lots of people have including me. I paid CIS flowtech to do it 7 or 8 years ago. not everyone want to do this and if your car has to pass emission testing then you probably have to leave the functioning lambda system, catalytic converter, and air pump systems on there so it passes the emissions test

"Seems way easier that modifying the fuel head..."

>If you only remove the lambda valve you have to adjust (turning clockwise a little) the the six individual 3mm allen head spring tension adjustments (raising spring tension pushing down on the diaphrgm a little) under the 4mm button head screws next to the injector line banjo fittings to compensate.. If that is not done it will run too lean. It has to be done accurately for each injector on a flow bench to be done right. you can try doing it yourself woth the injectors in plastic water bottles and do it over and over until each injector fills the bottle equally but thats a risck if you don't know what you're doing.

That's just part of what CIS Flowtech does an excellent job of on a fuel head flow bench when modifying the lambda fuel head for more fuel flow across the range to get more fuel at higher rpms with higher than stock boost.

You can use an rpm switch controlling a vacuum solenoid in the boost pressure line going to the bottom of the CPR to keep the AFR's from being too rich during the initial onset of turbo boost in the midrange rpms with a CIS fuel head that has been modified to inject a lot more fuel than stock.
That will greatly improve drivability and fuel mileage with a 20%-30% higher flowing modified CIS fuel system..

Call Larry at CIS Flowtech when he's not too busy to talk to you. He likes to talk about fishing too...
Bo

Last edited by JFairman; 11-18-2014 at 08:58 AM..
Old 11-18-2014, 08:56 AM
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i dont think it will change the control pressure as in at the WUR. it really lowers the system pressure that is at the bottom or lower chambers. this lets the spring on top push down more on the diaphragm letting more fuel in. this leads me into what i wanted to say from the begining.
raising the system pressure would lean it out reducing the fuel at hi RPM,, and across the band.

is there really an issue with 100ron fuel and the amount of time at 6500?
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Old 11-18-2014, 09:03 AM
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Quote:
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raising the system pressure would lean it out reducing the fuel at hi RPM,, and across the band.
That's correct because hydraulic control pressure pushing down on the top of control plunger against the mechanical force of the air flow meter pushing up on it from the bottom will also increase as system pressure is increased.

Unless you make adjustments to compensate...

That's why you need an adjustable control pressure regulator when raising system pressure.
Then you can adjust and lower boost control pressure in order to keep the AFR from leaning out as system pressure is raised.

Overall CIS is complicated but all the sub assemblies that are working together are relatively simple.
A bunch of mechanical fuel pressure regulators all working with and against each other...
Old 11-18-2014, 09:28 AM
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You mention that the FV and WUR are independent... makes sense.
As a newbie, just learining this CIS stuff out of necessity, I noticed that the outlet flow from the WUR and the outlet flow from the FV go to the same banjo bolt on the fuel distributor.

I assume that this is the bolt that runs the fuel through the fuel head and back to the tank.

If they both drain to the same bolt, wouldn't a mulfunction in one effect the other as it raises resistance down stream?

Bo
Old 11-18-2014, 09:53 AM
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"I assume that this is the bolt that runs the fuel through the fuel head and back to the tank."

That banjo bolt is running the fuel from the CPR and the lambda valve through the middle part of the system fuel pressure regulator only. It's not going through any other part of the fuel head. The fuel pressure regulator is actually two seperate fuel presure regulators. The little skinny one in the middle is the one we're talking about here and it holds some fuel pressure in the CPR return line and lambda valve line leading up to it so the fuel system will hold 35 psi which is the fuel injector crack open pressure after shutting off the engine and fuel pumps over night or a little longer so the car will start faster next time you want to drive it.

If that little pressure regulator wasn't there then fuel pressure from the fuel pump check valve to the fuel injector pintle would drop to zero the moment the fuel pumps shut off.

The larger outer part of the fuel pressure regulator in the fuel head is what maintains system fuel pressure around 85psi in the early cast iron fuel heads and around 98 psi in the aluminum lambda fuel heads while the fuel pumps are running.

When removing the lambda valve you screw a 10x1mm plug into the fuel head where the lambda valve connected to the lower chambers and you take the short 10x1mm banjo bolt that was there and switch it with the longer 10x1mm return line banjo bolt the CPR and lambda valve return line banjo fittings were piggy backed on.

"If they both drain to the same bolt, wouldn't a mulfunction in one effect the other as it raises resistance down stream?"
Maybe.. I don't know.
Old 11-18-2014, 10:19 AM
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Bad LT
 
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Quote:
Originally Posted by JFairman View Post
That's correct because hydraulic control pressure pushing down on the top of control plunger against the mechanical force of the air flow meter pushing up on it from the bottom will also increase as system pressure is increased.
.
Very good info either side of this and thanks for the help so far.
In relation to this bit of the quote I've left in. Going back to my first thought of lowering my warm fuel pressure slightly should see a slight rise in an overall rich condition should it not. If that's the case I could do that then raise the CSV to kick in at a later RPM. Thus helping with a better AFR post 5,500RPM.

Now I typed that I should have a morning Coffee. 0800 here and no Coffee yet is a bad thing.
Old 11-18-2014, 12:35 PM
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Sorry, I don't know what you mean by CSV?
I'm guessing it stands for cold start valve but that doesn't make sense to me unless you have it wired to an RPM switch to open and spray fuel at a programed rpm.

Old 11-18-2014, 12:54 PM
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