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Mark, im jealous of your steady cruise afr. I know no 2 cars are alike, but just for reference, happen to know what your warm cp is set to? And do you have the rpm switch installed? If so, whats your switch set at?

Have you got any afr plots that I can view, or that you can describe to me? Im mainly interested in seeing a nice third gear WOT pull, as thats when I do most of my testing.
Old 10-21-2009, 04:21 PM
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Originally Posted by DailyDriven'88 View Post
Mark, im jealous of your steady cruise afr. I know no 2 cars are alike, but just for reference, happen to know what your warm cp is set to? And do you have the rpm switch installed? If so, whats your switch set at?

Have you got any afr plots that I can view, or that you can describe to me? Im mainly interested in seeing a nice third gear WOT pull, as thats when I do most of my testing.
Warm cp at 3.75, enrichment cp at 2.5, idle CO% about 2.5%. RPM switch set with 4800 chip. 3rd gear WOT settles in at 12.0 most of the time, sometimes a touch into the high 11's (I should probably tweek the afr's down to the mid-11's on boost, but I'm not really too worried about 12.0 for short bursts). I don't have an afr plot, just watch the gauge with one eye while the other watches the boost, the tach, the speedo, and finally the road.
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Mark H. 1987 930, GP White, Wevo shifter, Borla exhaust, stock everything else. The result of a massive Pelicanite good will fire recovery effort. Truely an open book, ready for the slippery slopes to modification.

Last edited by mark houghton; 10-21-2009 at 05:43 PM..
Old 10-21-2009, 05:40 PM
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Real interesting set up you have there. I guess it REALLY goes to show how different each 930 can be. Man, if I try a 4800 chip, I'd be lean for quite a while before enrichment kicks in. Can you tell me what your afr is from 4000-4800rpm at WOT?

On a dyno pull for mine, I see peak torque occur at exactly 4k rpm.

Last edited by DailyDriven'88; 10-22-2009 at 12:40 AM..
Old 10-21-2009, 08:25 PM
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Originally Posted by DailyDriven'88 View Post
Real interesting set up you have there. I guess it REALLY goes to show how different each 930 can be. Man, if I try a 4800 chip, I'd be lean for quite a while before enrichment kicks in. Can you tell me what your afr is from 4000-4800rpm at WOT?

On a dyno pull for mine, I see peak torque occur at exactly 4k rpm.
Oops...correction, I'm running with a 4600 chip. It progressively lowers as the rpm's build and is around 12.4 well before 4600 rpms. Everything happens so quicky that it's hard to visually plot stuff while blasting down the road.

Sure would be nice to put her on a dyno some day, but my guess is the nearest one is over 100 miles away and I don't know of a tuner familiar with the 930 (other than myself) around here. I run the car, listen closely, feel how it's performing, watch the data stream, and tune accordingly. I think these cars are quite a bit more forgiving than we're often lead to believe, especially for a street driven car, but if I were a dedicated trackster running full-on boost for extended periods, I would want to entrust it to a dyno and professional tuner for safety sake.
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Old 10-22-2009, 09:27 AM
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I was seeing 12.6 to 12.7 prior to my 4k switchover at 3.75 cp and IMO thats a little bit too lean, especially with a faster spooling turbo and where the torque curve is. It did give me a good crusing afr though. So I lowered it and lowered it and ended up at 3.4 cp, and now Im at about 12.3 afr now before 4k. Cruise afrs are a bit down, but under WOT everything looks good. I have been doing a TON of searching on here and looking at dyno graphs that have afr plots. It seems lots of folks are delaying the enrichment well into the 4k rpm range (as you are) but all the afr's prior to that are in the 13's! Something to note though, on the dyno it was set at 3.7, and it sounded good and pulled good. IMO that goes to show you not everything can be felt or heard.

And yes, everything does happen quickly! I use an LM2 and thats where the record feature is real nice.

I also think you are true when saying that they are a bit more forgiving than we like to think. Its risky business though, as errors or mistakes on our part can be costly!
Old 10-22-2009, 11:09 AM
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Originally Posted by DailyDriven'88 View Post
It seems lots of folks are delaying the enrichment well into the 4k rpm range (as you are) but all the afr's prior to that are in the 13's!
I think many are able to get away with a longer delay (4800-5000 rpm...and some even higher) before boost enrichment because the risk of detontation becomes more of an issue at the higher rpm echalons. Besides, you really don't want full boost enrichment giving you 10.0 AFR's at 3000 rpms just because you've got full boost and the WUR is doing it's thing early. Just robs you of power. Such is my understanding, anyway, of the logic behind it all.

So your AFR's may seem a little high on full boost (especially with the faster spooling turbos) but your rpm's haven't caught up yet. With my setup I could go with a higher rpm pill (and I did for awhile run with a 4800) because my turbo isn't really getting with the program until around 3800...and it takes only a second to get from 3800 to 4800 and the boost enrichment to begin.
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Old 10-22-2009, 02:39 PM
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Up top, im fine. 6800rpm and its at 11.7-8.

I guess you could say I tuned it around the peak torque curve, and thats because I had the luxury of knowing where it occurred. The dyno operator and Brian Leask were both in agreement about what should be done to correct my particular situation.

We all see what happens when people tear down their 930 engines here. Most of the time its not cool. I wonder how many are delaying for too long (creating lean conditions just prior) and what the consequences are. If its working for you though, cool. It may not hurt, other than a long drive, to see your power curve on a dyno.

I appreciate all of your input though Mark and I guess we'll have to see what I do to cure the surge.
Old 10-22-2009, 05:23 PM
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In 2nd gear, just rodding the crap out of it (for me, that's just over 6 grand), I see about 11.5

I wish I could help with your weird surge problem. I had a surge at steady cruise 25 mph that drove me nuts, but just had to tweak the mixture screw on the fuel head. That was in the very early days way before I knew squat about these cars and just didn't have the mix right. You've got a lot of good input here, but also have pretty much ruled out everything. Try stuffing a gas soaked rag down the fuel tank and torching it when all else fails.

Just curious: Have you put a timing light on when it's doing the funky chicken? I wonder if your timing is dancing around appreciably. Could be an erradic vacuum retard signal getting to the dizzy...retarding, then advancing rythmically. Why, God only knows. Leaky diaphram in your advance/retard can attached to the dizzy? And I can't remember if you're running with all Lambda O2 emissions crap or not (O2 sensor, electrical solenoid and/or temperature sensitive valve to the vacuum lines to the dizzy, frequency valve that leans her out based on the sensor input, etc.). Major long shots....
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Mark H. 1987 930, GP White, Wevo shifter, Borla exhaust, stock everything else. The result of a massive Pelicanite good will fire recovery effort. Truely an open book, ready for the slippery slopes to modification.

Last edited by mark houghton; 10-22-2009 at 06:25 PM..
Old 10-22-2009, 05:55 PM
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At this point, Im all about long shots! I have not put a light on it to see what the timing is doing. If i had to guess though, it would probably be moving just like the afr does when its surging. I will confirm that though this weekend. I had the entire dizzy apart 6 months ago for a general cleaning and lube. At that time, I made sure the diaphram held vacuum, which it did. I will also re-confirm. Car ran fine afterwards.

No O2, but the dizzy does have the thermo valve and the other switch still inline with the vacuum lines. I believe they are working correctly. The idle will kick down after a minute or so during cold starts. I believe thats one of the functions of either one, or both, of those dizzy devices? Can I simply leave those items out of the loop for testing purposes? I think the answer is yes but just double checking. Frequency valve still installed. How do you check its function?

I also want to say that I dont mean to or want it to look like I'm shooting people's suggestions down (in a rude way) because when I say Ive checked everything, Im not kidding! The amount of research and testing Ive been through is no joke.
Old 10-22-2009, 09:17 PM
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[QUOTE=DailyDriven'88;4968462]No O2, but the dizzy does have the thermo valve and the other switch still inline with the vacuum lines. I believe they are working correctly. The idle will kick down after a minute or so during cold starts. I believe thats one of the functions of either one, or both, of those dizzy devices? Can I simply leave those items out of the loop for testing purposes? I think the answer is yes but just double checking. Frequency valve still installed. How do you check its function? [QUOTE]

You can just route arouind those solenoids and valves, and you would primarily just lose the additional advance for the first minute of cold start. Instead, the vacuum retard would be there right from the start instead of being delayed. To be honest, I suprised the solenoid even works since your O2 sensor is disconnected, but it's obviously an isolated function controlled by the same box under the seat that controls all the other Lambda functions. I was just wondering if the solenoid was being spassmic; stopping retard/allowing retard either because it's triggering when it shouldn't be or it's internal mechanisms are beginning to fail (i.e. leak). If you were to unplug and then plug back in your retard vacuum line at the dizzy once every half second, would you get the same weird idle?

Testing the frequency valve....well, all you can really do is listen to it buzz (engine off, key on, force the pumps to run and you'll hear it buzz away). Unplug the connection, plug it back in and listen to it. If it failes, you'll have problems with very lean conditions. Can't run without it (at least not without adjusting all 6 fuel plungers in the fuel head to compensate).

This is a diagnostic mystery. I just seems to me that you're chasing a vacuum issue somewhere.
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Last edited by mark houghton; 10-23-2009 at 11:06 AM..
Old 10-23-2009, 06:57 AM
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Roger that. I will bypass them and see. Your theory about the dizzy retard sounds like it could happen.

Doubt the frq. valve is bad then, since I dont have 'very lean' conditions.

I asked this question on the first page, but didnt get a response. An opinion, or possibly fact, that idle surge is caused by a rich condition. A vacuum leak creates a lean condition at idle correct? Its unmetered air, which equals less fuel. How does that hold up to the rich surge theory?

Last edited by DailyDriven'88; 10-23-2009 at 11:30 AM..
Old 10-23-2009, 11:27 AM
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"An opinion, or possibly fact, that idle surge is caused by a rich condition. A vacuum leak creates a lean condition at idle correct? Its unmetered air, which equals less fuel. How does that hold up to the rich surge theory?"

A rich idle mixture in a fuel injected car will always cause the rpms to oscillate up and down and thats a fact. I used to work on German cars for a living and I've seen this with CIS or K-jetronic, L-jetronic, Motronic, and the kugelfisher mechanical fuel injection used on the old BMW 2002 tii's
I have never experienced this with a carburator running rich at idle though.

The answer to the other question is more complicated.
All air leaks in a turbo cars intake system are often called vacuum leaks even though some are actually air pressure leaks because it's easier to group them all together in conversation without getting overly techanical and people that are familiar and experienced with turbo cars understand the differences.

An air leak below the throttle butterfly will be a vacuum leak of unmetered air at all times and cause a lean situation unless the turbo is boosting and the throttle is open far enough to let in more boosted air pressure than the intake ports and cylinders can swallow, then it will cause a rich situation because metered air is leaking out to atmosphere while metered fuel is being injected into the intake ports.

An air leak after the turbo and before the throttle butterfly, or blow off valve will be a pressure leak at all times other than when you first snap the throttle open before the turbo spools up.
The turbo is making pressure in the intake before the throttle body at idle and steady cruise, it's just low enough to not show on the boost gauge.

This is metered air so if any is leaking out between the turbo and the throttle body it will cause a rich mixture.

Have you tried lowering boost control pressure with your Brian Leask adjustable warmup/control pressure regulator yet?
Old 10-23-2009, 12:38 PM
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Quote:
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Have you tried lowering boost control pressure with your Brian Leask adjustable warmup/control pressure regulator yet?
Jim,
Great job describing how vaccum and boost leaks differ in their affect to mixtures in boosted applications. That's always a tough one to internalize.

But you lost me in your final comment re: lowering the boost control pressure. Are you referring to that as a possible cause of rich idle?
It's been my understanding (fact or fiction?) that the WUR boost enrichment is fully in by around .3 bar or so. Correct? So even though at idle where there isn't enough boost to register on the gauge, we will still see some level of enrichment occuring via the boost signal at the WUR? And if you were to lower the boost CP at the WUR, then affectively you would get even more fuel vs. air at these very low idle boost conditions due to the lowered fuel pressure resistance at the control arm? So, if a surging idle is the result of being too rich as a result of the WUR's boost circuit, wouldn't he want to try increasing the boost CP to lean out the mix?

I must be missing something in the translation. You da man with all that German- Beemer experience.
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Last edited by mark houghton; 10-23-2009 at 01:56 PM..
Old 10-23-2009, 01:21 PM
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I said that because I asked him to raise steady warm cruise CP a few days ago (which would also raise idle CP a little) to see if it would push the metering plate up a little higher leaning out the idle mixture a hair and see if that would stop the rich mixture rpm oscillation at idle.

He says he can't do that because it will lean out his boost CP at the same time. Fine, that is correct to a degree, but that is why I suggested lowering the seperate boost CP adjustment to compsnsate for raising steady cruise/idle CP.

All 4 seperate spring pressure adjustments on the BL adjustable WUR affect each other and once you get one set right you have to go back to the others and reset them too until you find a balance that works on your car and it's state of tune.

I've readjusted my B.L. adjustable WUR around 40-50 times trying to tune around 2 different Flowtech/IA modified +20% fuel heads until I got things as good and consistant as I can get it.
I don't think there's many people out there other than Brian Leask that have spent as much time adjusting his WUR's as I have and know the results as well as I do. It takes an incredible amount of time to tune around a modified fuel head from the beginning.
Now I know where to start with one if you're using it on the street and you want to get decent gas mileage still.

The boost CP adjustment is the approximately 15mm round stainless steel interference fit disc on the bottom of the WUR. It is setting spring tension internally.
The 4mm allen head adjustment in the middle of this disc is the warm steady cruise/ CP adjustment.
These 2 seperate spring tension adjustments are very adjustable and sensitive and can make big differences in the CP's and AFR's under boost and or steady cruise.
If you have the rpm switch and vacuum solenoid on the MAP line to the WUR you don't even have to mess with the threshold adjustment because the boost clamp overrides it and is much more effective.

When you get all the other settings right, you go back and reset the cold start CP a little and you're done.
Old 10-23-2009, 03:12 PM
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Quote:
Originally Posted by JFairman View Post

A rich idle mixture in a fuel injected car will always cause the rpms to oscillate up and down and thats a fact.
I have never experienced this with a carburator running rich at idle though.

An air leak after the turbo and before the throttle butterfly, or blow off valve will be a pressure leak at all times other than when you first snap the throttle open before the turbo spools up.
The turbo is making pressure in the intake before the throttle body at idle and steady cruise, it's just low enough to not show on the boost gauge.

This is metered air so if any is leaking out between the turbo and the throttle body it will cause a rich mixture.

Have you tried lowering boost control pressure with your Brian Leask adjustable warmup/control pressure regulator yet?
I have also experienced on some electronic FI cars where a vacuum leak will cause a surge/oscillation at idle and if you combine that info with a rich condition on a carb'd engine not causing the issue, that just shows me just how different many of the systems out there respond to different situations. Thanks for the clarification.

You got me thinking about an air leak after the turbo but before the throttle plate. I have new O rings throughout but what if the BOV isnt sealing tightly? I put in new seals about 6 months ago but I did happen to hear a ticking noise from that area the other day (not while it was surging). It sounded like the recirc valve spring inside rattling. I havent heard it since. I may throw new seals in there again for the hell of it.

Jim, have I been mis-reading this whole time? Are you suggesting raising warm cp or boost cp? I thought warm cp. The car does have the rpm switch so how would boost cp have any effect on idle? I can see how it would be possible if I didnt have the switch.

Mark: I did bypass the 2 switches inline with the dizzy vacuum lines and no difference other than a lower and rougher idle during cold start. I will probably hook them back up.

Last edited by DailyDriven'88; 10-23-2009 at 03:23 PM..
Old 10-23-2009, 03:19 PM
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I said that because I asked him to raise steady warm cruise CP a few days ago (which would also raise idle CP a little) to see if it would push the metering plate up a little higher leaning out the idle mixture a hair and see if that would stop the rich mixture rpm oscillation at idle.

He says he can't do that because it will lean out his boost CP at the same time. Fine, that is correct to a degree, but that is why I suggested lowering the seperate boost CP adjustment to compsnsate for raising steady cruise/idle CP.
Now I think Im more confused, haha. If I raise warm CP, it will create a condition that I believe is too lean prior to my 4k rpm switch. Are you saying I can alter that lean condition by adjusting boost cp even though Im before my 4k switch?

Last edited by DailyDriven'88; 10-23-2009 at 03:32 PM..
Old 10-23-2009, 03:22 PM
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If you have a Brian Leask adjustable WUR like you said you do....
Most likely yes, but all cars are a little different so again I'm just suggesting things that have worked for me on my car..

But I guess you havn't tried the warm steady cruise +CP adjustment I suggested so why doubt or question the boost -CP adjustment I suggested twice now to compensate for it if you did.
Old 10-23-2009, 04:03 PM
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I doubt and or question it because Brian Leask himself suggested the warm cp adjustment only, nothing else, since the rest of the afr graph looked good.

I can and will try your suggestion this weekend. I did the dizzy switch bypass because it took me all of 2 minutes to do. Your suggestion takes a little bit longer, even if my WUR still isnt bolted down. To be honest, I missed the - boost cp suggestion until Mark asked about it. I assumed you just made a typo.
Old 10-23-2009, 06:02 PM
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