cold start hunting / still rich under boost

[gorskined]

I finally have my 3.0l 76 row 930 turbo motor drivable. it actually runs really nice . But
i have two minor issues I'm looking to correct .
Problem 1
i have a cold start surge issue ( sounds like its hunting). The motor starts right up 65 deg ambient temp but surges between 500 and 700 rpms when cold for the first minute. Then the surging subsides and the idle holds in at around 800 for about 2 minutes then once the wur is up to temp its a nice steady 900-950 RPM idle
i am smack dab in the middle of the cold fuel temp pressure curve. my 02 screw is about a 16 turn under injector squeal at rest.( i was leaner but it had a gurgle so i richened it up now im about 12.7on the afr at warm idle ) . my afr is low 10 when it first starts but quickly starts to rise to upper 12s as it warms.
i understand the idle afr screw how it adjusts the sensor plate stop . and the big idle screw how it meters the air bypassing across the butterfly . so how do i adjust the cold without screwing up the warm? what am i missing?

problem 2
just before boost my afr is at low 11s my warm fuel pressure is 2.9bar 42psi (2.6-3 bar is the range ) under boost my afr drops to 10.5. I had adjusted the boost dump to 2.6bar 38 psi just to get it up off of the bottom of the gauge to hit a afr of 10.1 -10.5 my wur boost hold out solenoid is set to 4800 rpms i can run up over 6k still very low 10s. My wastegate and bov are working very nicely a gradual dump and holds .7 bar ( btw love the evergreen raptor k27 turbo really nice gradual spool )

so what the next logical step ?
do i go further on closing the gap on my boost dump fuel pressure adjustment
or adjust my warm up fuel pressure to lean out the entire fuel curve
or do i up my rpm hold out to 5,000 ???
what's the typical afr. i should be shooting for just before boost ? i currently have a nice curve high 12 low 13s regular driving as i get on it it drops to mid 11s before boost the under boost drops into low 10s


Thanks in advance cant tell you how much i appreciate the advice and wealth of knowledge here on the forum.
Regards Ned

[908/930]

Does the 76 use a AAR (auxiliary air regulator)? If so possibly not opening enough when cold.

[Alan L]

Yes - it sounds a bit rich on early idle. Typically if you have that surge and lean the idle a fraction, it jumps up to a steady faster idle - ie hit the sweet spot. But all your settings sound good - so yes - a bit of a quandry where to go from here. Basically your fuel system sounds like too much fuel overall when warm. I think what I would do from here is consider the WUR specs a guide - and trust the AFRs. So my first choice I think would be to raise the WUR pressure to say 3.2 and see if that all works better.
For that inital idle - yes some more air would help. But if you are comfortable that you have the idle mix correct for warm idle I would look elsewhere. It is possible your AAR can be adjusted to open a bit more when cold. Dunno if you have ever taken one apart - but it is possible you don't have the full slit opening. What you could do is look at it at typical cold temp - take a pic down the throat. Then drop in freezer for an hr and check again. If the slit has gotten bigger then you have some room to play with. What does happen over time is the bimetalic finger can get a 'set' in it - loosing a bit of range. It means drilling out the plugs and fitting bolts/nuts (4mm I think) to close it back up. But when you see inside you will see you can re adjust it to make the slit more open at a cold/ambient temp.
Good work getting this far.
Regards
Alan

[Toddrivers]

Do you have an adjustable WUR that you can change the wcp by turning the allen screw on the bottom of the wur? I have rarely had to adjust my idle mix screw on the afm or the air screw on the throttle body. I think your cold cp is close, not sure why the idle is slow and hunting unless it relates to your AAR like 908/930 said. I would not try to adjust WCP at the idle screw but use the allen screw on the bottom of the wur if you have one.
WCP should be about 53 psi or 3.65 bar depending on the car. As a comparison and this may or may not be ideal but when I start up cold at around 70f my afr is 11.5 to 12. Warmed up afr will hover around 13.5 depending on rpm and will read 11's when under boost.

[gorskined]

Originally Posted by Alan L

Yes - it sounds a bit rich on early idle. Typically if you have that surge and lean the idle a fraction, it jumps up to a steady faster idle - ie hit the sweet spot. But all your settings sound good - so yes - a bit of a quandry where to go from here. Basically your fuel system sounds like too much fuel overall when warm. I think what I would do from here is consider the WUR specs a guide - and trust the AFRs. So my first choice I think would be to raise the WUR pressure to say 3.2 and see if that all works better.
For that inital idle - yes some more air would help. But if you are comfortable that you have the idle mix correct for warm idle I would look elsewhere. It is possible your AAR can be adjusted to open a bit more when cold. Dunno if you have ever taken one apart - but it is possible you don't have the full slit opening. What you could do is look at it at typical cold temp - take a pic down the throat. Then drop in freezer for an hr and check again. If the slit has gotten bigger then you have some room to play with. What does happen over time is the bimetalic finger can get a 'set' in it - loosing a bit of range. It means drilling out the plugs and fitting bolts/nuts (4mm I think) to close it back up. But when you see inside you will see you can re adjust it to make the slit more open at a cold/ambient temp.
Good work getting this far.
Regards
Alan

no aar i always assumed the row didn't come with one. The Motor didn't have one and it was pretty stock when i got it. i didn't even know what the purpose of the aar was until now . i always thought it had something to do with the us emissions. \ so if i should have an aar that's obviously the hunting issue. currently looking trying to find a diagram on how its plumed .

[gorskined]

Originally Posted by Toddrivers

Do you have an adjustable WUR that you can change the wcp by turning the allen screw on the bottom of the wur? I have rarely had to adjust my idle mix screw on the afm or the air screw on the throttle body. I think your cold cp is close, not sure why the idle is slow and hunting unless it relates to your AAR like 908/930 said. I would not try to adjust WCP at the idle screw but use the allen screw on the bottom of the wur if you have one.
WCP should be about 53 psi or 3.65 bar depending on the car. As a comparison and this may or may not be ideal but when I start up cold at around 70f my afr is 11.5 to 12. Warmed up afr will hover around 13.5 depending on rpm and will read 11's when under boost.

Thanks yes i do have that wur been fine tuning it over the last few weeks but given the top of the range is 3 bar on a 3.ol wasnt sure how much more i should go.i had a bunch of popping close to 3 bar but that was before i adjusted the o2 setting . first i need to find out if my motor should have an AAR.


Thanks

[gorskined]

Originally Posted by 908/930

Does the 76 use a AAR (auxiliary air regulator)? If so possibly not opening enough when cold.

i don't have an AAR . I always assumed that was an emissions thing on US cars . need to look into see if a 3.0L76ROW should have an AAR and if so where does it connect to.
That defiantly could be the problem . i know i don't have an electrical connect for one .

[gorskined]

so after hearing about this AAR thing
i started googling it appears they call multiple items an AAR .. There is the 930-110-275-01 that is the vacuum controlled gold pan cake bypass thing when under a vacuum bypasses from the ic back to the intake side of the turbo not sure why they are referring to it as an (AAR) i do have that . There is also the 930-606-102-01 that is electronically controlled bi-element thing that heats up similar to the wur that is referred to as an AAR. and apear to have its owne set of issues . That i do not have. I'm assuming this bypasses from the back side ic to below the throttle body?? there are also many aftermarket 12v aar that look like they may work. any one using an aftermarket aar ( or idle control valve ) not very excited about spending $1300 on a NOS bosch AAR. i do not have a connector nor did i ever see a spot for one on my engine wire harness for an aar but my intake manifold looks to have the mounting holes .

[flightlead404]

Originally Posted by gorskined

no aar i always assumed the row didn't come with one. The Motor didn't have one and it was pretty stock when i got it. i didn't even know what the purpose of the aar was until now . i always thought it had something to do with the us emissions. \ so if i should have an aar that's obviously the hunting issue. currently looking trying to find a diagram on how its plumed .

That doesn't sound right to me. Maybe someone more familiar with the early turbos can chime in, but afaik the AAR is an integral part of how the K-Jet systems worked.

Looking in my workshop manual I believe I see an AAR for 1976 models. The Porsche workshop manual calls this an Auxillary Air Valve, or AAV.

I suspect you have multiple issues.

For cold starting sounds like your cold start valve is working and putting in additional fuel at crank. The other functions in cold start are the low and increasing WUR control pressures which start rich, and get leaner. Those #'s are documented.

Additionally there is the AAR (or AAV) which allows more air for a while. This should give you a higher idle, around 1,800 rpm for a few seconds, by allowing more air to bypass the throttle place. Thirdly is the ignition, which is advanced by 10 degrees or so during the warm up phase.

[908/930]

Yes, the 930-606-102-01 is what I was asking about. Yes you could fit in a 12v solenoid controlled air valve or idle control valve, some are voltage driven others are current, pretty sure the old BMW ones are voltage (pre 1989), all you need is full open so not sure it matters. If you search some were using these to bump engine speed when AC is on. I don't remember where the hose ties into but you are likely correct somewhere below the throttle body, not sure if you have a location for a hose there.

[Alan L]

I have heard of people deleting the AAR/AAV. Yes it is the bit controlled by a bimetallic finger, and has it s own plug. You should have a spare plug lurking in your wiring harness - to the RHS of your WUR? In fact I suspect it is the same bimetallic finger that is in the WUR. They both work the same way - 12 V applied from Key On. The finger works against a spring - in both cases. In the AAR case it allows the cold start air to slowly shut down - in tandem with the WUR changing the fuel head pressure from CP to WP. They work in tandem. If you can find a spare Bosh plug in the harness, you can likely refit one. I think people dumped them because they are not trouble free and the warm up circuit causes a few headaches. They can work perfectly well if understood and maintained. Some people just decided to get rid of the hassle and troubleshooting and put up with an erratic warm up phase.
If you find a spare Bosch plug - or a chopped harness, my suggestion would be to install one.
Regards
Alan
You could of course just leave it deleted. Your cold start symptoms are exactly what you would expect in that case. The part is generic to all CIS 911s, so should be relatively findable. My bet is you have a spare plug or a cut piece of harness. from memory it parts out of the loom at the same point as the WUR plug. Can check the wiring for you in a day or so.

[Toddrivers]

I believe AAR is the correct terminology, bleeds air to the intake when cold. I think it uses the same 12v source as the wur. I have seen these in the parts classifieds for $50 - $75 from time to time. You should pick one up when available.

[tops911]

I had an issue sorta like that. When I bought my car it had all black relays. So I bought 2 new Red relays (fuel pump) and installed them. I guess they provide power to the WUR to help it heat up faster, too. At the time I did not know the relay issues. I chased this problem for a couple months before I ended up swapping the relays back to the old ones and the issue was corrected.
Good luck

[gorskined]

It's all coming back to me now. The early 930s used a plunger solenoid to advance something inside the cis box during cold start just under the Fd... The yellow wire was energized during cold start. Not exactly sure what it did but it was very short lived. Caused more problems that it was worth.most were removed under warranty.The first 50 or so cars had it . I no longer have this unit it was pretty rough and I traded it for a fully restored unit to a list member that had a concours early car but didn't have the correct early unit. so the unit i do have is a 76 3.0 but just a little later in the model year still has the side casting but no plunger assembly . so i probably could use a aav. but not sure where to plumb it into the intake manifold. I think I'm going to install a hand throttle. I always like that on my other 911s.

[gorskined]

As most of you know I have been plagued with fuel issue to rich to lean . Good one day bad the next all was good since I replaced my check valve so I figured I was on the right path .
So the other day I was adjusting my wur to lean out my control pressure. Because under load my arf is still low....I'm now at the top of my factory wur pressure settings. To the point it was not idling well . And still rich under load ... I took my remote fuel pressure sending unit off my control pressure line and moved it to the system pressure . So I could see my system pressure while driving. It fluctuated between 70 and 90 while driving... Back to Google. Come to find out my Bosch 044 is a counterfeit knock off.. I should have known seeing as both had faulty check valves. I just ordered the new Bosch 200 series from our host. ...

[gorskined]

Originally Posted by flightlead404

That doesn't sound right to me. Maybe someone more familiar with the early turbos can chime in, but afaik the AAR is an integral part of how the K-Jet systems worked.

Looking in my workshop manual I believe I see an AAR for 1976 models. The Porsche workshop manual calls this an Auxillary Air Valve, or AAV.

I suspect you have multiple issues.

For cold starting sounds like your cold start valve is working and putting in additional fuel at crank. The other functions in cold start are the low and increasing WUR control pressures which start rich, and get leaner. Those #'s are documented.

Additionally there is the AAR (or AAV) which allows more air for a while. This should give you a higher idle, around 1,800 rpm for a few seconds, by allowing more air to bypass the throttle place. Thirdly is the ignition, which is advanced by 10 degrees or so during the warm up phase.

how is the does the ignition advance during warm up work ?

[908/930]

I do not think the early cars used the ignition advance. There is a thermo valve tied into the hose for the retard pot, it opens to atmosphere allowing the vac advance on the other pot. Pretty sure this is intended to help the cat converter warm up faster. If it fails it can cause problems because your ignition will not back off properly during boost.

[gorskined]

Originally Posted by 908/930

I do not think the early cars used the ignition advance. There is a thermo valve tied into the hose for the retard pot, it opens to atmosphere allowing the vac advance on the other pot. Pretty sure this is intended to help the cat converter warm up faster. If it fails it can cause problems because your ignition will not back off properly during boost.

Thanks
good to know i don't have anything like that .. just an old school unmolested vacuum line.

[krasuskyp]

Hey Ned-

Quite odd for you to not have a plug somewhere to fit an AAR - hope you locate it, sounds like will likely help your issue. The round diaphram thingy is a decel valve and aids in mellowing exhaust popping on decel.

Yes, very lame on the counterfeit Bosch items - been an issue for years now, least you're now fully versed in how to discern. Hope your new 200 pumps solve your issue as well, I'm running a pair as well.

BTW, lmk when you wanna meet up - I'm in Tolland, near UCONN...

[gorskined]

Originally Posted by krasuskyp

Hey Ned-

Quite odd for you to not have a plug somewhere to fit an AAR - hope you locate it, sounds like will likely help your issue. The round diaphram thingy is a decel valve and aids in mellowing exhaust popping on decel.

Yes, very lame on the counterfeit Bosch items - been an issue for years now, least you're now fully versed in how to discern. Hope your new 200 pumps solve your issue as well, I'm running a pair as well.

BTW, lmk when you wanna meet up - I'm in Tolland, near UCONN...

no plug... look back a few posts the early turbos used some sort of plunger to advance the cis . we will defiantly get together once i shake out all my bugs.