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A fellow Pelacanite
 
NathanUK's Avatar
 
Join Date: Nov 2006
Location: UK
Posts: 2,002
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I have a chart for the '91 3.3t

It states at 20 degrees C (room temp) the cold pressure is 3bar which is approx 45PSI.
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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.

http://www.danasoft.com/sig/Iamnotanumber.jpg
Old 12-04-2007, 01:17 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #41 (permalink)
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Alan L's Avatar
 
Join Date: Apr 2006
Location: New Zealand
Posts: 3,185
progress report

Thanks Nathan. I tried some lower pressures - dropping one spring out, winding the adjuster back. But it seems it wants to run at 50 psi. I had it running at 40 psi, but it is loading up with too much fuel at the moment. Too rich. Not sure what is causing this. Seems to be on the factory setting then - for a 3.6 T.
BUT, good news. No Fuel head leaks and NO PLATE FLUTTER.
I am very happy about that. It seems the scored piston was at fault. You have no idea how good a rock steady air plate looks to me right now. Having been thru all that, I have concluded in hindsight that I could have replaced the piston without splitting the fuel head. It pings out the bottom once you let the lock tab go. But I had no idea what I was looking for, and it could have been a damaged diaphragm or whatever.
I just have to get this mixture leaner now. Not sure how many turns I have on the adjuster screw before it falls out into the airbox. Scares me.
My piston is about 0.5 thou smaller in diameter than the original - but minus the scoring. Not sure if this difference is letting more fuel thru or not. Seems worse at idle, with a few revs seems happier.
Will have to investigate further. Spent ages synchronising the injectors. Very tedious.
Thanks for the help guys, and Goran, you can relax now.
Seems Bosch and I came to the same source of steel for the pistons - the coeff of expansion was the same, and mine came out 0.7 gm heavier by the time I finished it in the original shape. I intentionally left extra on originally - better too heavy than light - can always take some off.
Regards
Alan
Old 12-04-2007, 07:53 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #42 (permalink)
Crotchety Old Bastard
 
RarlyL8's Avatar
 
Join Date: Jan 2000
Location: Huntsville, AL
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You machined a new metering piston? Damn you are hard core! Ha!
I hope all those who are hisitant to work on the fuel head are reading this thread and getting the great insight you have shown us.
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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 12-04-2007, 08:02 PM
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Alan L's Avatar
 
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Location: New Zealand
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I have pretty well solved the tuning problem - I have one of those spring loaded mixture adjusters - but the knob was just turning on itself - the actual adjusting screw was not moving. Once I took it off and stuck my allen key down the hole I could feel it move. It was about 1 turn too rich - it suddenly hit a sweet spot , and whang!. Slight tuning issue to sort - hesitant coming on to throttle - feels like a lean spot. Will have to look further.
My AFR system arrived today (about 3-4 weeks). Am trying to get some work done tomorrow, having killed all today.
Brian, I think I posted pics of my piston in progress - compared to the damaged one. Fat chance of buying one here - and I really just wanted to know if it was the problem, before scouring the world and spending mega$'s. This one cost me about half a day and $2. And seems to work. I'd still be waiting after Xmas for the answer. A small workshop lathe is the best tool you can buy.
Alan
Old 12-04-2007, 09:44 PM
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Quote:
Originally Posted by Alan L View Post
Thanks for the help guys, and Goran, you can relax now.
Seems Bosch and I came to the same source of steel for the pistons - the coeff of expansion was the same, and mine came out 0.7 gm heavier by the time I finished it in the original shape. I intentionally left extra on originally - better too heavy than light - can always take some off.
Regards
Alan
Jeez. First you split the fuel head, then you made your own plunger piston. That's seriously hard-core! I dissasembled many things but wouldn't touch CIS with a 10-foot pole (except throwing it out and replacing it with EFI)

So you recieved your WBO2? That's excellent! I hope it has functionality to log AFR vs. RPM, it's quite hard just to look at the indicator.

As far as I understand, you first synchronized the individual injector flows by measuring the fuel flow vs. time and adjusting their spring tensions and then fiddled with "collective" CO adjuster screw by turning it 1 turn until you got your idle right?

I suggest doing a WBO2 pull now and checking AFR's during the load. Usual CIS behaviour is fairly rich AFR's (around 12 or so) during the boost, then leaning out above 5500 RPM towards 13's.
CO screw mostly influences AFR's at idle and low loads, it's the shape of CIS flapper-cone that is doing the air-fuel "mapping" after that. About on-throttle hesitation: as far as I know, CIS doesn't have any accelleration-enrichment device except the inertia of plunger itself. When you boot it, plunger is supposed to overswing briefly and squirt extra fuel. You new DIY-plunger maybe isn't "run in" yet so it doesn't move as freely as old one.

If I understood everything correctly, you bought Japanese car with later US-spec engine that has been rebuilt recently, ROW dizzy and fuel head, 964 WUR and Mercedes fuel regulator? Challenging to say the least!
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Thank you for your time,
Old 12-05-2007, 02:05 AM
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Me like track days
 
Craig 930 RS's Avatar
 
Join Date: Sep 2003
Location: Kirkland, WA
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You deserve some sort of CIS Medal of Honor. Hard core! Way to go.
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- Craig 3.4L, SC heads, 964 cams, B&B headers, K27 HF ZC turbo, Ruf IC. WUR & RPM switch, IA fuel head, Zork, G50/50 5 speed. 438 RWHP / 413 RWTQ -
"930 is the wild slut you sleep with who tries to kill you every time you "get it on" - Quote by Gabe
Movie: 930 on the dyno
Old 12-05-2007, 07:09 AM
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Join Date: Apr 2006
Location: New Zealand
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Guys, I would never have attempted this whole 930 project without the Pelican forum. Just getting quick reliable information , experience and being able to bounce ideas is invaluable - when you are stuck at one end of the world with limited access to things. I suspect my tuning hesitation is more like a small air leak - this is typical symptom. I have had the plenum and intercooler (they do make good work trays) off 5-10 times in last few weeks, plus replumbed lots of vacuum fittings. I'm hopeful I will find either a faulty hose, or seal. As I said earlier - the fuel head O ring is suspect. Every time I have pulled it out it had a sliced O ring. The last one I sized 2 mm less hoping it would squeeze in. The hole needs re chamfering. But not today. Will take a day or two to get WBO2 in.
This thread started with a 'where to now ? on a 930. Wandered off to fuel pump relays and CIS head. I will try and link them up to tidy it up for anyone else stuck with the same issue.
Goran, I don't mind CIS - I am not at the point of performance limitation, and it is about as simple injection system as you can get - I like simple, and don't like computer stuff. I can tell you a recent story about cars/computers/$'s sometime.
Brian - if you are there - your PM box is full.
Best regards to 930 Pelicans - we are almost ready for takeoff.
Alan
Old 12-05-2007, 09:10 AM
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A fellow Pelacanite
 
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Location: UK
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Alan, I think the lower the control pressure the richer it will run. The higher the control pressure the leaner the engine will run.
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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.

http://www.danasoft.com/sig/Iamnotanumber.jpg
Old 12-05-2007, 02:30 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #48 (permalink)
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Alan L's Avatar
 
Join Date: Apr 2006
Location: New Zealand
Posts: 3,185
Yes Nathan, that is correct. The system pressure works against the WUR pressure - which sits on top of the piston. When the air plate drops, it pushes the piston up - because the pin of the piston rests on the other end of the air plate arm. To lift the piston, the arm has to work against the WUR pressure. The lower the WUR pressure - the easier to lift the piston, which opens the metering slots = more fuel for a given amount of air. When you tune your idle CO you are just adjusting the height the pin sits at in the metering slots for a given opening of the air plate.
Now that I have it tuned approximately right, I can fiddle with the WUR. But from memory , in my 3 km run previously a month or so ago, I dont recall a hesitation.
Regards
Alan
Old 12-05-2007, 03:26 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #49 (permalink)
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