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Yet another WUR/CIS fuel thread

So I've installed my new UTCIS on the track car and am anxiously awaiting the arrival of my LM-2 to correctly tune it.. However on the 86 STOCK turbo theres a few issues to be resolved so I'm looking for some advice. Here's a summary of where I'm at..
It runs rich , when turbo kicks in it's black smoke, and sometimes some bucking..
If I lean it out I can't start it without pulling the air filter and pressing down the throttle plate to give it a bit of a "prime".. Also have a tough time adjusting the idle low enough
Just ran a pressure test on the "cold " WUR ( although it's 95 degrees in my garage here today).. system pressure is 6.7Bar and control pressure is 3.0 Bar..
Haven't run it "warm" yet..
So questions.. what other tests are relevant??
What would indicate a bad WUR ??
If it is a bad WuR do you think I could take the good one from my Euro 79 engine ( that was running great before I put the UTCIS on it)? Its a different P/N and obviously doesn't use the Lambda control on the engine it came from.
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98 Tahoe ,2007 Saturn Vue
86 930 black and stock, 80 930 blue tracdog
91 Spec Miata (yeah I race a chick car)
"life"ll kill ya" Warren Zevon
Old 07-07-2008, 06:27 PM
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How are you leaning it out? Is your '86 WUR adjustable?

Cold pressure settings have little to do with warm/threshold/boost settings. They all need to be set sepparately and then blended to the best compromise.

Your system pressure and cold pressure are both high.

If you have a known working WUR from the '79 then swap them out, check your pressures and be done with it. They all work the same basic way. I've had several WURs on my engine with 3 different part numbers.
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'78 911SC Widebody, 930 engine, 915 Tranny, K27, SC Cams, RL8 Headers & GT3 Muffler. 350whp @ 0.75bar
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Old 07-07-2008, 07:07 PM
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Bryan,
I was using the mixture control ( with allen wrench on the top of the fuel distributor)..
I'll swap it out and see how it runs,, will have to wait till Friday or Sat at this point.
T
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91 Spec Miata (yeah I race a chick car)
"life"ll kill ya" Warren Zevon
Old 07-07-2008, 08:29 PM
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Brian,
According to my notes his system pressure is in spec ( and the control pressure may only be slightly high - around 3 bar at 30 deg C - which must be close to 95 deg F. Depending which engine type, -eg 68, system pressure starts at 6.7 bar.
Cold start valve sticking - that would explain the pig lean start. But not warm idle problem.
Alan
Old 07-07-2008, 08:35 PM
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Alan,
Yes they are both in spec but on the high side. These pressures bleed over from one engine operating condition to the other. It is easier to tune the entire range if starting with the system pressure and warm pressure in the middle of spec. You can then wiggle those adjustments to accommodate your specific engine's needs. If there are other problems causing a rich condition they will only be made worse by a warm pressure that is on the high side.
Without an adjustable WUR this is a moot point though, so swapping out for the known-good '79 is a better option.
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'78 911SC Widebody, 930 engine, 915 Tranny, K27, SC Cams, RL8 Headers & GT3 Muffler. 350whp @ 0.75bar
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Old 07-08-2008, 04:16 AM
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Brian,
It may be worth finding what type of engine he has. A type 68 is US spec of around that era (I'm anexpert on this now - thanks to you guys - I have a 68 engine). If it is a 68, the bottom end of system pressure starts at 6.7 bar - in which case - should probably be left where it is. (6.7 -7.4 spec) The cold pressure for this spec at between 30-35 deg C (I'm guessing this is about 95 F) is 3.0 bar. In which case the pressures would be spot on - for a starting point.
If it is not a 68 - they do drop a bit - about 10 psi for both.
Alan
Old 07-08-2008, 12:14 PM
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Yes, the pressures should be set to the middle of spec for the engine type number if the engine is stock. My factory manuals don't go to '86 but I was not aware that any 930 had a stock control pressure greater than 95psi. What is different about the 930/86? Typically you need a higher system pressure for high performance. The '86 US has less HP than the Euro '79.
In this case though it doesn't matter. The WUR is not adjustable. If the warm pressure is off, the engine is stock and and you wish to keep it stock then you must purchase another WUR with the same part number.

The mixture screw only affects idle mixture/baseline. You need to check the warm pressure then the boost pressure to determine that the WUR is in fact faulty.
As for the cold start issue, a high cold pressure is lean and vice verca. How does your engine act when started cold? Does it put-put-put to life or fire and idle slightly high as normal, but taking longer to do so?
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'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 07-08-2008, 01:43 PM
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Brain,
Yes that is exactly what it does!! put-puts to life and eventually warms up to a higher than normal idle..
FYI, the 86 manual does list significantly higher pressures than the 79 so I knew that these were in spec albeit on the high side
No idea why the higher pressures other than the added air pump and other emissions stuff ??
The plan now is to switch the WUR and take some A/F readings and report back to you ..
T
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Old 07-08-2008, 01:50 PM
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Brian,
PM sent.
Alan
Old 07-08-2008, 02:00 PM
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I would not discount the cold start valve malfunction - until you can be sure it is working.
You may have simply adjusted the idle screw mix pig rich to compensate and run rich when warm as a result.
You could also check the WUR is working properly. Cold pressure about right - but is it rising when warm - to lean the engine out.
It should rise about about 15 psi - depends a bit on which model engine/WUR you have. But it should rise by this ball park number. If it does not, the WUR is malfunctioning.
The cold start valve will seize over time if not used. If you can acess it at all (hard to get at - below and behind fuel head), you should feel it click (solenoid activated injector) when cranked on start. Maybe it is not supposed to work at 95 deg - but I would still check it if possible.
Alan
Old 07-08-2008, 05:06 PM
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Alan, I would normally agree with you, but the going rich has been a gradual thing, not like I woke up one morning and it was pig rich... but I'll add the check the Cold Start Valve to the list for Sat morning.
Todd
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Old 07-08-2008, 06:07 PM
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Alan - thank you for the '86 WUR info. It turned out to be a missing piece to a WUR puzzle I had a couple of years ago.

A buddy of mine was having issues with his 930 so I lent him my adjustable WUR for a few days. I had a -153 WUR laying in a box so I tossed it on and took the pressure readings. They were is spec so I ran it for a few days with no issue. Turns out that the -153 is the '86 WUR we are speaking about now.
The reason I think it worked in my car was that my fuel head was set at 90psi. The system pressure will affect all others so it likely brought the -153 WUR into spec for use with my engine. Many other bench tests were done on that unit to figure out how it worked. The various year WURs have slightly different features but all work basically the same.
I do not know why the '86 has higher spec pressures. It could be that more cylinder cooling was added to the smog motor via more fuel - this is pure speculation.

As for your cold start issue, I cannot remember off the top of my head at what temperature the cold start valve is taken off-line. At any rate, on a hot (95F) day you should be able to start the engine without the valve, it just takes a few more revolutions of the starter to get things going. There is one fellow here on the board who has removed his CSV and does fine in a warm climate.
The put-put-put is very typical of a lean start caused by slightly high cold fuel pressure. By slightly high I mean in spec but on the high side. It can be that finnicky. If you can tap the plug just a smidge and get it to mid spec this problem should dissapear. If not you have hurt nothing and the cold pressure will be spot-on.
As for the rich warm condition it really does sound like your WUR is taking a dump. Try installing the '79 WUR and take pressure readings. If it is in spec hook up your A/F gage and drive it until warm to see how she acts. You will do no harm and there is nothing to lose by trying.
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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
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Old 07-08-2008, 06:37 PM
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Glad to help out Brian - you guys put so much good stuff across this forum.
If he has not fiddled with anything in between and it is slowly going rich, I can only suspect the WUR is not fully closing from cold. Stiff mechanism - or - a good possibility might be a piece of crap on the fuel diaphragm plate - stopping it shut as far as it needs.
Need the warm pressure numbers measured.
Regards
Alan
Old 07-08-2008, 07:42 PM
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CSV? Do you mean what I would call the Cold Start Injector?
If so, the thermoswitch that controls it in the left hand timing chain cover is disconnected on my 930 and it started just fine at approx 10 degrees centigrade.
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Old 07-09-2008, 11:22 AM
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Cold Start Valve , I would guess.
They do seize up tho - and note, he has been priming the engine via air plate before startup. The CSV would do this more effectively, presuming it is working - firing a spray of fuel in the manifold throat at crank over. Better than pushing the airplate down before crankover.
Still worth checking I think- given start up is a problem. It would be simple if not so hard to get at. At cold crankover could see if the thermo switch is sending any power, first. Might be easier. If it is not sending power, then need to see if timed out on temp, or faulty. If is sending power, then need to see if valve can actually respond. My was rusted stuck shut.
Alan
Old 07-09-2008, 12:22 PM
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Did you actually need the valve Alan? I find it hard to believe that you did unless you live in a very cold part of USA.
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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 07-10-2008, 08:46 AM
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Update,, put the known good WUR on and no change,, starts cold pretty well, but is pig rich ( maybe even worse), WON"T start when warm without the throttle plate prime method..
In fact when I hit the turbo I can see the black smoke billow out of the exhaust in my rear view mirror.. I"m off to my buddies to install my bung so I can put an LM-2 on it..
Oh and when it's running so poorly I can only get about 0.4 bar on the boost, just won't spool up cleanly ..
So what's the next thing to check ?
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Old 07-13-2008, 09:33 AM
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The WUR warm pressure is the next thing to check - that will indicate where the extra fuel is/is not getting the information from.
Nathan - mine has been hard to start from day one - probably because of this idle mix problem - only 4/6 tuned right. When I first got it the CSV was stuck shut. Freeing it helped the start up. Even in summer. When I get this problem sorted, things may change.
Alan
Old 07-13-2008, 03:07 PM
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You replaced your '86 WUR with a known good '79 and still get the same result. I'd put the '86 WUR back on and assume that isn't the problem.

You need warm fuel pressure data, boost fuel pressure data and AFRs.

If your fuel pressures are in spec you can assume you are getting the right amount of fuel. The other element of the ratio is air. Is your air filter clean? Do you have a catalytic converter? Is is free flowing? Is your ignition healthy? Good strong spark and clean plugs?
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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 07-13-2008, 05:39 PM
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Yes - he still needs warm WUR pressure - it is possible he simply is not getting 12 v to the WUR, in which case, none of them will work - no matter how many you swap.
If it comes up to warm pressure spec, then can eliminate WUR and start looking elsewhere.
Alan
Old 07-13-2008, 08:17 PM
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