Pelican Parts
Parts Catalog Accessories Catalog How To Articles Tech Forums
Call Pelican Parts at 888-280-7799
Shopping Cart Cart | Project List | Order Status | Help



Go Back   Pelican Parts Forums > Porsche Forums > 911 / 930 Turbo & Super Charging Forum


Reply
 
LinkBack Thread Tools Rate Thread
Author
Thread Post New Thread    Reply
Registered User
 
Join Date: Jul 2006
Posts: 664
CIS Experts chime in. Strange AFR issue.

I'm trying to dial in a 76 turbo motor. Freshly built, mostly stock but has headers, k27 etc.

Car now runs great, rock solid idle, tractable, very civilized. When it comes on boost it's seems to be quite wicked. The problem is I can NOT get my AFRs below around 14 when in boost so I only stay there for a second. I have read most of the stuff on here and I have adjusted my WUR so the bottom slug is all the way out but it makes very little difference. The other odd thing is that my AFRs almost seem backwards. When cruising they are in the 13's but when I let off they go to 10, on boost they try to travel north towards 14-16.

I have had my WUR rebuilt and fuel head just rebuilt by fuel injection shop. New MSD, magnacore wires, etc, everything is up to spec.

I have over 100psi of pressure in the system. No leaks of any kind that I can find.

I've even borrowed a friends "working" (on a tired motor) WUR and it's better but not too much.

Any help is appreciated!
Old 01-18-2014, 08:22 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #1 (permalink)
Registered User
 
Join Date: Jul 2006
Location: S. Florida
Posts: 7,289
If you're '76 still has the black cast iron fuel head you're system pressure at 100psi or more is way too high and that makes control pressure also too high and that makes it run too lean.
Try removing a shim(s) or changing to a thiner shim in the system pressure regulator in the fuel head. System pressure should be around 85psi with the black cast iron fuel head.
Around 100psi system pressure is correct for the later cast aluminum lambda fuel heads.

If you go rich during closed throttle decel does the car have a recirculation type blow off valve or is it an aftermarket one venting to atmosphere?
The latter type will go rich at first when the throttle is closed and then gradually go lean as the turbo slows down during decel and pressure turns to vacuum inside the intercooler (before or above the closed throttle body butterfly) as the the blow off valve opens from high intake manifold vacuum (below or after the closed throttle body butterfly) and starts sucking in unmetered air leaning out the mixture.
Old 01-18-2014, 09:59 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #2 (permalink)
Registered User
 
Join Date: Jul 2006
Posts: 664
Thank you. I will have to see but I think I have the black fuel distributor. If I had to guess the fuel pressure coming out of the pump, directly into the gauge is like 140psi. I took the fuel distributor off but did not see any shims. Perhaps I should buy a regulator and try to regulate it down.

The BOV is a synapse Diverter valve. It was vented to atmosphere but I replumbed it to before the turbo in the intake stream.
Old 01-18-2014, 01:52 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #3 (permalink)
Registered User
 
Join Date: Jul 2006
Location: S. Florida
Posts: 7,289
All Bosch k-jetronic CIS fuel heads ever made have a small built in system fuel pressure regulator.
The 930 one is on the top right in the front and it takes a 15 or 16 mm wrench to unscrew it from the fuel head.
Be careful to not drop the plunger or any parts off of it.

Look for an exploded diagram of a 930 fuel head online that shows all the parts. Or maybe someone will post one.
Old 01-18-2014, 02:27 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #4 (permalink)
Registered User
 
Join Date: Jul 2006
Posts: 664
Thanks. Did that, took all the spacers out and it now seems to run pretty well in 1st and 2nd, getting into boost brings AFR down to about 11-11.5. But in third or higher it still goes lean up to 14 or 15. I tried putting another crush washer on the regulator to space it out further. That helped a bit but more of the same. I calculate I'm running around the 85 psi you specify for the black fuel distributor. Any other thoughts? Thanks!!
Old 01-18-2014, 05:42 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #5 (permalink)
Registered User
 
oilonly's Avatar
 
Join Date: May 2008
Posts: 1,148
Quote:
Any other thoughts?
Good thread here on cylinders 2 and 5.



data on which cylinders run leaner than others on 930 engine
__________________
'87, Modified WUR, Billet valve, 965 downpipe, Kokeln intercooler, GHL headers, Garrett T04B K27 hybrid, Tial w/.8 bar, WEGO IV, RarlyL8 dual out, LSD
Old 01-18-2014, 06:04 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #6 (permalink)
 
Crotchety Old Bastard
 
RarlyL8's Avatar
 
Join Date: Jan 2000
Location: Huntsville, AL
Posts: 13,622
Garage
Do you have fuel pressure data at these points:
> system pressure
> warm control pressure
> full boost control pressure
You say the engine is a '76, is the WUR Bosch number 0 438 140 022?
Is the fuel head # 0 438 100 037?
What is the full list of your mods?
__________________
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 01-18-2014, 06:21 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #7 (permalink)
Registered User
 
Join Date: Jul 2006
Posts: 664
Quote:
Originally Posted by RarlyL8 View Post
Do you have fuel pressure data at these points:
> system pressure
> warm control pressure
> full boost control pressure
You say the engine is a '76, is the WUR Bosch number 0 438 140 022?
Is the fuel head # 0 438 100 037?
What is the full list of your mods?
Hi thanks for the help. Keep in mind I'm new with Turbo cars and not super with CIS in general so I'll give the info I can, I am happy to try to get more.

System pressure is 6.3 bar as tested by closing T fitting with CIS gauges hooked up to WUR
Warm pressure is 3.6 bar
Not sure how to get boost control pressure but can try tomorrow
I believe the WUR is the 022, I have to double check that and the fuel head tomorrow morning.

Car is new to me. Previous owner has not given me any documentation yet, probably never will. The engine was supposedly rebuilt 300 miles ago with ported and polished heads and stock intake. He adapted a 3.3 intercooler, the turbo is a fresh K27, stainless headers, Synapse wastegate and diverter valve. Second fuel pump is Bosch 044 in 034 Motorsports scavenge tank. Car/engine does not have things like SMOG equip, AAR, A/C, etc

I just took the car out again earlier and as I mentioned, its strange to me that I can get into boost when it's cold and the AFRs go down to 10-11 but as it warms up it gets more and more lean to the point I can't get on boost at all.

Also did a CO test and it's running a 9.99% plus at idle
Old 01-18-2014, 07:15 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #8 (permalink)
Crotchety Old Bastard
 
RarlyL8's Avatar
 
Join Date: Jan 2000
Location: Huntsville, AL
Posts: 13,622
Garage
A cold engine should not be boosted. The warm control pressure will be low during this event which will enrich the mixture. Once the engine is warm the mixture will lean, which is what you are seeing.
If you have the -022 (and I suspect by your symptoms that you do) the WUR is not capable of supporting your mods. The -022 is primitive and works the same way that the early 911SC WUR did. They enrich using of the lack of vacuum instead of the presence of boost. That enrichment is calibrated for low output and cannot easily be improved upon.
With your modifications I would use a -054 or -112 WUR.
__________________
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 01-18-2014, 10:29 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #9 (permalink)
Registered User
 
Join Date: Jul 2006
Posts: 664
Thanks. I dont get into it when its stone cold, but I will get the boost up to 5psi or so to test it when the engine has run for several minutes and it's 70 degrees out.

Anyway, I might try a -153 WUR that I have laying around that's supposed to be from a 3.3 turbo. The lower diaphragm looks completely different that the 022.
Old 01-19-2014, 01:40 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #10 (permalink)
Crotchety Old Bastard
 
RarlyL8's Avatar
 
Join Date: Jan 2000
Location: Huntsville, AL
Posts: 13,622
Garage
That should do it. Won't be perfect but will be safer.
__________________
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 01-19-2014, 03:40 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #11 (permalink)
Registered User
 
Join Date: Jul 2006
Posts: 664
Update, maybe have a new problem. I now have 0 (zero) system pressure.

I tested system pressure yesterday and it was right above 6 bar.

Let the car sit over night, I bolted on the -153 WUR and tested it, the WUR showed a cold pressure of over 5 bar but when I close the T on the CIS gauges it is 0 bar. Borrowed a friends -054 WUR and tried the same thing and got 1.5bar for cold pressure but still 0 bar for system pressure.

Everything is hooked up correctly, only thing I did between yesterday and today was swtich WUR's and I removed the shims from the fuel distributor. I have put those back in for the purposes of this test but that did not change my 0 system pressure issue.

Will keep working on it. Thanks for any comments
Old 01-19-2014, 03:45 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #12 (permalink)
Registered User
 
Join Date: Jul 2006
Posts: 664
Scratch that. Sometimes people are stupid, usually those people are me. I had the T fitting mounted the wrong way on the CIS gauges! Back to 6.3 bar of system pressure. Will go back and try WUR's again now.
Old 01-19-2014, 03:55 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #13 (permalink)
Registered User
 
Join Date: Jul 2006
Posts: 664
Also, FYI I just checked the fuel head is -016
Old 01-19-2014, 04:26 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #14 (permalink)
Crotchety Old Bastard
 
RarlyL8's Avatar
 
Join Date: Jan 2000
Location: Huntsville, AL
Posts: 13,622
Garage
-016 is correct for your engine. I was hoping it had been changed out to a -037 which is a better match for a -054 or -112 WUR. The -153 WUR with the -016 FD is not optimal but should lower your AFRs on boost.
Old 01-19-2014, 09:35 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #15 (permalink)
Registered User
 
Join Date: Jul 2006
Posts: 664
So I've gotten it all swapped out. Still messing with the WUR pressures but the car does run a lot better. Although, it goes lean at tip-in, when boost comes on it AFRs go down to 11.2-12.2. Not sure what the going lean under light throttle is.

I have a fuel head off a 87 turbo somewhere. Should I try running that?
Old 01-19-2014, 09:51 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #16 (permalink)
Crotchety Old Bastard
 
RarlyL8's Avatar
 
Join Date: Jan 2000
Location: Huntsville, AL
Posts: 13,622
Garage
You might be OK now. The -153 should be set ~13.0-13.5 AFR at idle as a starting point. Cruise should be ~14.0-14.5 AFR. Light throttle will knock it down to idle readings. Boost enrichment begins at ~0.3bar with a steep pressure drop. AFR will climb out steadily to redline. Every engine runs a bit different and there is a sweet spot idle AFR. You'll have to find that with your new combo. If you decide to try the aluminum -145 Fuel Head the Lambda system must be removed.
__________________
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 01-20-2014, 05:03 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #17 (permalink)
Registered User
 
Join Date: Jul 2006
Posts: 664
Gotcha, looks like I wont do the lambda fuel head for now.

So now, with the -153 the car goes really lean, 15,16, 17 under light throttle and tip-in. I can drive through it to get on a little bit of boost and then AFR's will go down but its not usable as-is.

System pressure this morning was 6.2. Warm pressure is 3.6. Cold is around 1.9. Shows 3.5-3.6% CO on SMOG machine. I pushed the brass plug out (towards outside of WUR) to try and get lowest AFR's possible on boost and to see if that helped light throttle but it hasn't.

No intake leaks that I can find, spent at least 20-30 min shooting around with starter fluid. Timing is with-in spec. All testing and driving done when oil temp is roughly 180*.

Any other observations? I'm about ready to end my relationship with this car...
Old 01-20-2014, 04:50 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #18 (permalink)
Crotchety Old Bastard
 
RarlyL8's Avatar
 
Join Date: Jan 2000
Location: Huntsville, AL
Posts: 13,622
Garage
Where is your O2 sensor located?
Sounds like all is better. I wouldn't mess with the brass plug until you get AFR readings on boost. Don't want to have to see-saw if it can be avoided.
__________________
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 01-20-2014, 07:06 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #19 (permalink)
Registered User
 
Join Date: Jul 2006
Posts: 664
O2 sensor is mounted right before the turbo. Things are mostly better except for the stumble at light throttle. Given that, you have to be extremely gentle on the throttle which makes the car essentially undrivable
Old 01-20-2014, 07:11 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #20 (permalink)
Reply

Thread Tools
Rate This Thread
Rate This Thread:

 


All times are GMT -8. The time now is 10:27 PM.


 
Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2019, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2018 Pelican Parts, LLC - Posts may be archived for display on the Pelican Parts Website -    DMCA Registered Agent Contact Page
 

DTO Garage Plus vBulletin Plugins by Drive Thru Online, Inc.