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Alan L's Avatar
 
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turbo seal question

Keep trying to find a possible air leak to resolve a tuning issue.
Tried most things, sealed everything I can lay my hands on.
But I wonder about the turbo. I have a standard turbo. There is no spindle play and it makes full boost. I assume it is in reasonable condition. I know very little about turbos and have never had one apart. But it strikes me there must be a shaft seal between the inlet and exhaust side of the shaft, and if this was leaking you could expect some issues - like sucking exhaust gas into the intake at idle-low revs?
Am I correct, and what would the symptoms be and how would you check.
Also, I have sealed the BOV ends on plenum with silicone - but if there was an issue with the BOV, what would the sypmtoms be, and how would I check it. I'm running out of options to fix this tuning issue - sluggish pre - boost power - hesitation and leaness unless I run it so rich it is too rich on boost.
Alan
Old 07-27-2008, 02:17 PM
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Negative on turbo. If turbo is so worn that there is "gas going from hot to cold side" you would notice it in much more spectacular fashion. There is a bearing in-between lubricated with hi-pressure oil film. Once that lubrication is gone, turbo is trash within seconds.

Remember, as long as you aren't leaking something out of the system, all air sucked into engine is going trough CIS first. So even if BOV piston is stuck or leaking, everything is going trough CIS, is metered and fuel is dispatched accordingly.

Thus: you still have good-old CIS fueling problems. WUR, control pressure, cone steepness...the usual.

Do you have wide-band lambda? If nothing else helps, you might try to strangle the cone on low-load part. Thus manually "map" the leanness from the low-load region.

Remember, CIS doesn't know about turbo...it just feels the air sucked trough it. It delivers same amount of fuel regardless if you boost or not, as long as it's feeling the same flow trough it. Only way to "map" it is to to modify cone or to use digital WUR or such.

Frankly, you could use Megasquirt connected to one injector, in order to "bleed" fuel from control-pressure and voilá, you can map it any way you like. MS costs 200 bucks and you are a handy man
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Last edited by beepbeep; 07-27-2008 at 02:53 PM..
Old 07-27-2008, 02:46 PM
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Thanks Goran. I am running out of possibilities for this metering problem.
The wide band AFR shows leaness everytime I apply throttle - if I am at idle of say 11, it will go to 13-14 with slight throttle, and bog down until reaches boost range. Then AFR will drop to say 11-11.5, and power comes on. These numbers alter with control pressure. I currently have it set about 10 psi below proper value. If I use proper value CP, the leaness goes out to 15-16 and it misfires/backfires badly. But it idles erratically too - the AFR changes after each boost run.
I had it tuned ONCE where I had reasonably smooth power from 2000 rpm (bogging below this) by dropping the CP 10 psi. The AFR hit 11.5 on boost and crept up to 12.2. I was pretty happy with this, but cannot get it to do it again. I have since installed new injectors too, to help the low end power. But it still runs like crap below boost.
One side of the dual exhaust outlet is always cold, while the other is hot - which is weird, but I supect connected.
I am seriously considering digi WUR (same price as new injectors). But am very worried it is not the WUR that is at fault, and same problem will persist.
Just did compression test (all between 125-130) - which is consistent with my earlier leakdown test - 2-3%. Just thought I may have burnt a valve, or cracked a piston ring etc. The problem is sooo persistent.
Would electrical -ignition problems cause this. Have put new plugs in. About all left is new leads. They look fairly new - but hard to check - they have air gap units in them.
Regards
Alan
Old 07-27-2008, 03:13 PM
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I don't believe your problem is mechanical or caused by ignition.

What do you mean when you say "One side of the dual exhaust outlet"? Just a outlet after the turbo or before the turbo? Exhaust gases are siamesed prior entering the turbo so what happens after they leave the turbo is not important. It's just matter of exhaust flow trough muffler. It would be better to measure temp on your heat exchangers. If both are hot, everything is OK.

If your AFR's are not consistent after each boost run, I suspect your hand-made CIS plunger is sticking. If it's sticking, it will be stuck until large onset of boost air "unsticks it". This kind of behaviour is very hard to mend, even with digi WUR.

I would log RPM, boost, AFR in a full-boost run (WOT from 1500 RPM to 5500 RPM) and compare the results. If AFR is changing in-between, CIS in behaving inconsistently and CIS fuel plunger is probably sticking.

It might be time to remove the CIS and polish the plunger and it's bore little more?
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Old 07-27-2008, 03:33 PM
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Thanks for reply Goran. The plunger is very smooth in the bore. I have polished it to a better finish than the original - according to the people who heat- treated it. It is 0.5 thou smaller diameter than the original - ie 0.25 thou more clearance. The same symptoms occur with the original piston - low rev poor power. (The original is made of tool steel apparently). With the original piston I was getting very inconsistent fuel flow readings at each injector at low throttle opening - 100% variance between outlets, while tuned to within 1-2% at WOT. This led to erratic idle - and the headers were operating at very different temperatures after a minute or two of idle - one or two dead cold, others warm, others very hot.
Currently (new piston/injectors) they all feel about the same. At the moment it starts on 6, instead of 4. Last measure, the idle fuel flow rate was very close for all outlets. I have also gently pushed the airplate down with no fuel load, it is smooth - no resistance.
The exhaust has dual outlets - one each end. The turbo flows into the top of muffler, two outlets at lower ends. The LHS gas is always hot, the RHS gas is always cold. Work that out. Where is the cold gas coming from via an exhaust system? If I tune the idle to very rich to try and fix low range missing, the LHS emits black smoke, the RHS does not. And yet they siamese into the turbo, and get all mixed up before flowing to muffler. Work that out. And the RHS of the engine seems to have been more erratic than the LHS - in terms of header temps. I have scratched my head until nothing left to scratch.
I have checked for spark at each ignition lead, and swapped leads over. An ignition misfire would look like lean mixture - as the sensor measures O2, not fuel. So, stuffed for other options, I was considering that track. But can't imagine why the ignition would behave badly at low revs and work fine at boost. There is no misfire at 5-6000 rpm.
I just can't work this out.
Regards
Alan
Old 07-27-2008, 04:48 PM
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I have wondered about the cone setting. As far as I can see, the plate is set at right height - in line with top of parallel edge. However, it is fully extended upwards. If I try, I cannot lift it any higher. Should there be any remaining vertical movement beyond the rest position - is it set too high? This would seem to cause a rich response rather than lean tho - slow to allow air to follow fuel. My problem is the opposite - the fuel seems slow to follow the air.
Alan
Old 07-27-2008, 04:55 PM
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Allan, where are you ? I have an extra WUR I could loan you if that would help..
Todd,,, I highly recommend the digital WUR however..
T
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Old 07-27-2008, 05:55 PM
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Todd - thanks for the offer. I am at the bottom of the world. Next stop Antarctica. And at the moment, it feels fairly close.
But I do not think the WUR is the problem - at the moment. If I get to the point of suspecting it, I may take you up.
I really suspect the fuel head or an air leak I have yet to find, in some exotic location (which is why I have not splurged on a digi WUR yet). Intend to shortly pressurise the intake system as in pic, to see if I can find any more. But with your situation in mind - this is how I found my injector blocks to be seriously faulty. It takes about 1/2 hr to strip it down this far and then you can easily test all this end of the system. It takes about another 1/2 hr to remove CIS gear and manifold if you need to replace injector blocks.
Goran - I saw a clip few days ago - on You tube I think- of a 911 evading police in a late night run thru a city in Sweden. Hmmm. Test driving a customers tune up??
Regards
Alan
Old 07-27-2008, 06:32 PM
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Goran - can I pick your brains for a couple of questions?
My air plate opening at idle is extremely small - less than 0.5 mm. My problem with the AFRs is that as I move off idle in the 1-3000 rpm range, the AFrs lean off by about 3 numbers from idle AFR, and stay there, until boost fuel hits. So, if my idle AFR is 12, once I am moving I end up with AFR 15, and misfire, lack of power etc. This says the metering piston needs to be higher in the fuel chamber (1/4 turn on mix screw) for this air plate opening. If i make my idle pig rich (10) I can get down to 13 AFR at around 2000 rpm, and it begins to respond to throttle.
So, possibly the idle air plate setting is wrong? What if I knocked the air plate down a fraction - this would lean my idle AFR off, and have less effect on intermediate openings AFR?
Maybe my airplate is just set too high? I cannot go any higher - it won't lift any further than its current rest position.
Or will my piston just compensate for any air plate adjustment. I think this adjustment is independant of piston setting?
Second Q. My WUR system has another complicating piece stuck between WUR and fuel head. From previous discussion on this forum the conclusion was it is a fuel enrichment device (Bosch) that is normally found on Mercedes. A small chamber which my WUR feeds into and exits to the fuel head. I can only conclude it is some sort of diaphragm ballast thing that allows temporary softening of WUR pressure. I would dispense with it - but I need another WUR fuel line to do so. It has an adjust screw in the base of it - but all I can feel is nothing, until it comes up hard against the internals. Any experience of this? Maybe I should fiddle with that screw?
Thank you for your time.
Regards
Alan
Old 07-28-2008, 11:48 AM
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Alan, I'm only guessing really but it would seem you need a digi wur.

Why not hook up CIS gauges and compare the readings with the chart in the factory manual while you drive.
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Needs Fitting - K&N CO Sensor, Round A/F Dial Gauge, Factory Short Shift Kit.

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Old 07-28-2008, 01:02 PM
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Nathan, I don't have any way to hook gauges up inside car - but the idea is right. If I'm going to go to that bother, I suspect I'm better just to get digi WUR.
If I can convince myself that the WUR is the issue, I will get a digi one. What concerns me a little is that the digi unit may be correcting in many cases another fault. If you can identify the fault, I suspect the system would run better if fixed, rather than asking digi WUR to compensate - brilliant that they seem to be.
If for instance my air plate is simply out of adjustment because someone monkeyed around with it previously, it would make sense to fix it first. Altho the digi would compensate for it pretty well. But it is looking increasingly like the option. It just tees me off that the system should run better than this, and not being able to nail the issue.
Alan
Old 07-28-2008, 02:31 PM
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Quote:
Originally Posted by Alan L View Post
Goran - can I pick your brains for a couple of questions?
My air plate opening at idle is extremely small - less than 0.5 mm. My problem with the AFRs is that as I move off idle in the 1-3000 rpm range, the AFrs lean off by about 3 numbers from idle AFR, and stay there, until boost fuel hits. So, if my idle AFR is 12, once I am moving I end up with AFR 15, and misfire, lack of power etc. This says the metering piston needs to be higher in the fuel chamber (1/4 turn on mix screw) for this air plate opening. If i make my idle pig rich (10) I can get down to 13 AFR at around 2000 rpm, and it begins to respond to throttle.
So, possibly the idle air plate setting is wrong? What if I knocked the air plate down a fraction - this would lean my idle AFR off, and have less effect on intermediate openings AFR?
Maybe my airplate is just set too high? I cannot go any higher - it won't lift any further than its current rest position.
Or will my piston just compensate for any air plate adjustment. I think this adjustment is independant of piston setting?
Second Q. My WUR system has another complicating piece stuck between WUR and fuel head. From previous discussion on this forum the conclusion was it is a fuel enrichment device (Bosch) that is normally found on Mercedes. A small chamber which my WUR feeds into and exits to the fuel head. I can only conclude it is some sort of diaphragm ballast thing that allows temporary softening of WUR pressure. I would dispense with it - but I need another WUR fuel line to do so. It has an adjust screw in the base of it - but all I can feel is nothing, until it comes up hard against the internals. Any experience of this? Maybe I should fiddle with that screw?
Thank you for your time.
Regards
Alan
Hmm. Honestly, I don't know much about CIS. But yes, your door might be sitting offset to cone and whole cone VE "mapping" is thus shifted.

There is a small entry in manual which says that flapper can be forefully adjusted if it sits too high.

I would start with bypassing the Mercedes device. I suspect it contains some sort of spring. Maybe accelleration enrichment device?

After that is done, try shifting the flapper so you get more gas off-boost and then adjust down idle CO with usual Allen wrench.


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Old 07-28-2008, 03:42 PM
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Thanks Goran. My plate is central. But I'm not sure what excessively high is. But it is so high that it is physically restricted from being lifted any higher - by some internal mechanism. So, at rest, it is pushing hard up into the cone. You cannot lift it another mm.
Might try dropping it a bit.
I'm going to have to find some CIS plumbing to bypass the Mercedes bit - which will not be easy. Which is why it is still on there.
Regards
Alan
Old 07-28-2008, 04:03 PM
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Quote:
Originally Posted by Alan L View Post
Thanks Goran. My plate is central. But I'm not sure what excessively high is. But it is so high that it is physically restricted from being lifted any higher - by some internal mechanism. So, at rest, it is pushing hard up into the cone. You cannot lift it another mm.
Might try dropping it a bit.
Regards
Alan
It's restricted by a stop pin. Sits in top front of the venturi to the left side. Drift pin and hammer carefully to lower plate if warranted.
With pressure on the system, the top face of the flow sensor plate should be as close to possible to the top edge of the machine cut inside the top of the venturi. Give it +0.25mm/0.010” but don’t set below edge of cut line. When top edge of sensor plate passes the cut line, air-flow change begins.
Old 07-28-2008, 04:27 PM
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Many thanks.
That is pretty much how it is set now - top edge of plate in line with top edge of parallel machine cut.
Looks like it is where it is supposed to be.
Eliminates that option.
Thanks
Alan
Old 07-28-2008, 05:36 PM
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Alan, I recently bought some fuel hose and had connections crimped on to it so I could have a gauge inside the car to check while I drove my 3.2 carrera. I used the CIS gauge kit along with another gauge on the end of my new hose.
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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.

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Old 07-29-2008, 10:30 AM
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Nathan, this all makes good sense - and you gave me an idea. I have now found I can replicate the problem with the car not actually driving - but simply going thru the throttle movements that would cause the problem on the road. So I spent some time last night watching my CIS gauge on the WUR as I induced the lean AFR by raising revs beyond idle.
The pressures barely moved - altho did increase by about 3 psi at higher revs. I suspect this may be a voltage issue for the fuel pumps - at a guess. My battery is near the end, so this is about the only explanation I can think for that behaviour. But the leaness cuts in prior to this while the WUR pressure is rock solid. Every now and then it would clear itself and the AFR would drop down. This suggests the fuel head/piston - as Goran suggested.
I pulled the head again and played with both pistons in the bore. Every now and then both of them would catch slightly and temporarily. Go back to the same spot of rotation and travel next time, and smooth as. Given the minute clearances in the bore - about a thou, I am wondering about grit in the fuel system.
I am about to pull the fuel tank, and have ordered a new filter.
We will see.
Regards
Alan
Old 07-29-2008, 11:38 AM
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Nathan, this all makes good sense - and you gave me an idea. I have now found I can replicate the problem with the car not actually driving - but simply going thru the throttle movements that would cause the problem on the road. So I spent some time last night watching my CIS gauge on the WUR as I induced the lean AFR by raising revs beyond idle.
The pressures barely moved - altho did increase by about 3 psi at higher revs. I suspect this may be a voltage issue for the fuel pumps - at a guess. My battery is near the end, so this is about the only explanation I can think for that behaviour. But the leaness cuts in prior to this while the WUR pressure is rock solid. Every now and then it would clear itself and the AFR would drop down. This suggests the fuel head/piston - as Goran suggested.
I pulled the head again and played with both pistons in the bore. Every now and then both of them would catch slightly and temporarily. Go back to the same spot of rotation and travel next time, and smooth as. Given the minute clearances in the bore - about a thou, I am wondering about grit in the fuel system.
I am about to pull the fuel tank, and have ordered a new filter.
We will see.
Regards
Alan
Old 07-29-2008, 11:38 AM
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Alan, did you check the pressures against the factory manual?

Also I would try removing that addition to your CIS. I understand why someone used it but it would be a shame for you to be chasing a fault that does not exsist...
I think Mercedes used them?
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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 07-29-2008, 11:55 AM
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hmm...it shouldn't be so important with pump pressure as pressure regulator will make sure that fluctuations don't matter. It only cares about pressure difference between system- and control pressure. K-Jet is built this way so it can be immune to fluctuations in system pressure.

If leanness is not repeatable every time, there is something binding in there. After everything moves OK and you get same results every time, you can start fiddling with control pressure and cone steepness in order to produce AFR curve you fancy.

P.S.
DPHANS posted a link to K-Jet manual here:

Looking for a good book on fuel injection
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Last edited by beepbeep; 07-29-2008 at 12:40 PM..
Old 07-29-2008, 12:33 PM
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