Going lean at a specific rpm.

Odrapnew · Post by **Odrapnew** » Tue Jul 01, 2008 8:14 pm

So I did some more tuning tonight after some good advice by a few people.

I made a few changes, but didnt really get anywhere.

After cruising for a while and making changes, I stumbled upon an odd occurrence.

Between about 1600 and 1800 rpm, my afr's go lean(above 15.5). I checked afr compared to load, tp voltage, maf voltage, loadx, and none of them have any correlation with the lean afr at those specific rpm. If I hold at about 1700 rpm, my afr goes to about 16, or more. Doesnt matter what gear or speed as long as its in that rpm range.

Anyone ever have an issue like this? I'm thinking something mechanical like fuel injectors, spark.....i guess that about it.

I was just thinking, I dont have a breather line running from between the blower and the maf which could be causing unmetered air enter in through the pcv valve. Its weird that I didnt have this problem a few days ago and all of a sudden its there. I tried old tunes and they all seem to have this problem.

What do you guys think?

Nick

Cougar5.0 · Post by **Cougar5.0** » Tue Jul 01, 2008 8:32 pm

It's remotely possible that it's some sort of air leakage issue (though why at just one RPM?)

It could also be a reversion misfire - perhaps due to your cam.

You may have a HEGO timing issue associated wit your longtubes - I didn't notice before that you had these - have you adjusted your HEGO Delay for these? Longtubes could be causing much of your AFR deviations.

Lastly - are you certain there is no MAF issue in this area?

Odrapnew · Post by **Odrapnew** » Tue Jul 01, 2008 9:07 pm

I forgot one detail. The lean conditions happen even when I force OL.

I did change my hego delays to account for the longtubes. Not sure if its correct, but here are what they are.

140 10.00 10.00 10.00 10.00
100 10.00 10.00 10.00 10.00
90 10.00 10.00 10.00 10.00
80 10.00 10.00 10.00 10.00
70 12.00 12.00 12.00 12.00
60 12.00 12.00 12.00 12.00
50 14.00 14.00 14.00 14.00
25 18.00 18.00 18.00 18.00

I'm pretty sure the maf isn't part of the equation because this lean condition happens at different maf voltages depending on road conditions(up hill, down hill, level road). The only thing that seems consistent is the rpm and afr relation.

If it was the cam, could it be caused by the injector timing? I have tried to run EA for injector timing, but I haven't implemented the injector timing because it just didn't seem right. Maybe I should try that to see how that affects the lean condition. I also notice that when I run the injector timing calculator, I get a lot of red numbers indicating the timing exceeds the event. Is this going to be a problem? Another edit, when I change the injector firing event to intake open, I get all black numbers(no red). What should I be using for calculating injector timing to be able to use in BE?
EDIT(again): I searched injector timing and found some possibly useful information. Im going to subtract 100* for light loads and 50 on loads at 40%(scaled to go up to 150% for blower).
Thanks for the help, at least I'm eliminating some of the possible causes.

Cougar5.0 · Post by **Cougar5.0** » Tue Jul 01, 2008 9:50 pm

Hmmm, injector timing - that might have an effect - just change the region where you are seeing an issue - try exhaust close to try to eliminate any possible exhaust interaction. Don't worry about the red cells - just make sure the injection is completed before the intake closes - perhaps 540 deg max. As an alternative, you can try to completely fire the injector before the intake opens (supposed to help vaporize fuel). Let us know if this helps.

I don't know if your HEGO delays are correct, but it's good that you've addressed this issue already.

Edit - yes, there is some good reading on the injector timing issue recently here.

Odrapnew · Post by **Odrapnew** » Wed Jul 02, 2008 12:04 pm

Well, out of curiosity I looked at an Inj. PW vs. afr graph and it seems like the PW is not decreasing during the lean conditions which leads me to believe I possibly have a misfire at that point. I think I'll pull the plugs and see what they look like and check the cap and rotor while Im at it. Then I'll pull my ignition box and see if that helps.

Odrapnew · Post by **Odrapnew** » Thu Jul 03, 2008 7:43 am

Well, I tried my first change, and that was changing injector timing. The car seems to idle a little better, but I still have the same leaning issue.

I'll be checking out the plugs next, probably end of the weekend.

Odrapnew · Post by **Odrapnew** » Tue Jul 08, 2008 8:18 am

I was thinking of when this started to happen.

I think it started after I hooked up the hego ground. I dont know why this would have any negative effect on anything, but could I be getting some odd signal that would be causing these problems?

I'm just adding to the list of things that could be wrong, but for some reason this one sticks out the most.

Thoughts?

Odrapnew · Post by **Odrapnew** » Tue Jul 08, 2008 7:00 pm

Just out of curiosity, I checked out my distributor inside and its very, very loose. The plate that the distributor armature bolts to can rotate somewhere around 10 degrees and I can pull it off by hand. I dont know how much its affecting the leaning issue, but I know its can be good for it. Anyhoo, I have to get a new distributor before I do any more tuning.

Odrapnew · Post by **Odrapnew** » Fri Jul 11, 2008 6:07 pm

Got a new/used distributor and put it in today and took it for a short drive. The car runs much smoother, especially at idle. I'll do some more tuning early next week but the car runs much better now that I'm giddy like a school girl.

Odrapnew · Post by **Odrapnew** » Tue May 26, 2009 3:00 pm

Bump an old thread. I changed the distributor last fall and the car ran a little better. I still have the leaning issues. Anyone have any new ideas?

Odrapnew · Post by **Odrapnew** » Thu Jul 09, 2009 2:02 pm

Going up one more time.

This leaning issue is bugging the hell out of me. Every time I shift while cruising, the rpm's drop enough to run right through the 1600-1900 rpm range and the engine leans out and the car hesitates until I pass 1900 rpm. After that, everything clears up and it runs a little rich but smooth. I've looked at maf voltage, maf flow, inj. pulsewidth, throttle position, lamse's, and the only thing that I have determined to have most of the affect on afr's is the rpm.

What happens in a tune at 1900 rpm that would cause the car to run richer, or what happens at 1600-1900 rpm to cause the car to run lean?

At WOT, the car pulls like a raped ape. Afr's are right at 11.5 from 3000 all the way through 6000, and injector duty cycle never gets much above 80%.

Could there be a vacuum leak that I can't find? I still don't think that would answer the question about why afr's drop right around 1900 rpm. I also thought about a sticking valve, but the heads were rebuilt within the last 5k miles or so, and I would think that would create issues at more than just the small rpm range.

Post by **cgrey8** » Thu Jul 09, 2009 2:05 pm

Is it going lean on tip-in? Or is it lean throughout the drop in RPMs?

Odrapnew · Post by **Odrapnew** » Thu Jul 09, 2009 2:35 pm

If I start a pull from say, 1200 rpm, and keep a constant throttle position, the car will be running in the 14.5 afr range(with the maf transfer I have right now). Once it gets up to the 1600 rpm range, it starts to lean out to around 15.5(or greater) afr and usually peaks around 1800 rpm. Once I pass about 1900 rpm, afr's drop quickly to the 14.5 range again. I can richen the maf transfer in the approximate range where it leans out(anywhere from 1.3V to 2.5V depending on throttle position), but then it's running rich everywhere else.

It's not tip-in because if I shift(manual tranny) into the 1600-1900 range, afr's will drop to about 12.5 and then increase to 15.5 or more once I am out of the acceleration enrichment zone and once it hits 1900 rpm, its like a switch and afr's drop to normal again.

Post by **2Shaker** » Thu Jul 09, 2009 3:18 pm

So do you see this only when you force OL, or even when in CL? If you log the MAF, are the MAF voltages where you would expect them to be in the RPM range in question when the event occurs? Is Load doing anything odd at those times?

Post by **cgrey8** » Thu Jul 09, 2009 3:48 pm

It almost sounds like Injector Slopes aren't setup right. But that's about all I can tell from just a rough description.

Odrapnew · Post by **Odrapnew** » Thu Jul 09, 2009 4:21 pm

I am running OL full time because I've had issues in the past with running CL(excessive lean conditions because of improper maf xfer). I could try to run CL and see what happens, but I should be able to get the car to run well in OL, then switch CL on.

I don't see any odd problems with maf voltages or loads in this range(no spikes or dips), and as far as I know, they are about what I'd expect in that range.

Injector slopes could be off, I have them set at 42/48(or 46) high/low, with breakpoint value of 2.5 lb/rev. I had this problem even running with both slopes at 42. If slopes were off, wouldn't I have other issues at different rpm and loads? I have run a full throttle run through the lean range(actually 1200-2200) and it still has the drop in afr at about 1900 rpm.

347ranger · Post by **347ranger** » Thu Jul 09, 2009 8:09 pm

where is the maf in the intake tract? this is a stretch but you might be seeing some funky air flow from the blower through the maf right at that rpm. does this happen in neutral? maybe try running with the blower belt off and see if its the same through that rpm range. if the maf is in a blow through configuration or is mounted upstream but very close to the blower it may be getting washed by the blower turbine at that rpm. like i said its a stretch but its the only thing i can think of thats the same no matter the load at that rpm.

Odrapnew · Post by **Odrapnew** » Thu Jul 09, 2009 8:29 pm

The maf is before the blower. It is attached to a 180 degree bend which is attached to the blower. I did pull the belt off and it didn't have an effect on the lean condition. I could try revving it in neutral to see what happens.

I did update the binary to be able to use the fn1360 table, so I might try messing with that just to get a better control on afr's for now even though its just a bandaid.

347ranger · Post by **347ranger** » Thu Jul 09, 2009 8:51 pm

well i can't think of anything else that would only be rpm related. but using the fn1360 table and only running OL will fix this for sure. i would be interested to see what effect CL would have. but that would not fix the lean dip while WOT.

there is nothing funky with your spark tables right? if you had a column at 1900 rpm with funky spark timing it might cause this too. i doubt it but....

Odrapnew · Post by **Odrapnew** » Thu Jul 09, 2009 9:11 pm

Nothing odd that I notice in the spark tables. Logs also show pretty smooth spark values.

Oh well, thanks for the ideas. At least they eliminated a few possible problems. I still feel that its either a computer(tune or bug), or a vacuum leak that I can't find.

Post by **EDS50** » Thu Jul 09, 2009 9:32 pm

Shot in the dark here but could it be related to a leaky surge valve? There might be some air getting past the surge valve at that specific rpm range. I had a similar problem like this with my 92' until I upgraded to the monster size red Procharger Blow off valve since I run a blow through set up. If suspect that to be the problem you may want to upgrade your surge valve. If you are still using the bosch style valve like the ones that come in the vortech kits you may want to look into replacing it with the bosch 114n. It is the same size and style and will hold more boost ( I believe up to 14#, maybe more?) and can be purchased from any vw/audi parts counter. Just trying to think outside of the box, hope it helps. Also check and make sure you dont have a faulty pvc Though I doubt that is the culprit.

Odrapnew · Post by **Odrapnew** » Fri Jul 10, 2009 8:35 am

Hmmm, I wonder if that could be the problem. I'll see if anyone local has one I could try before I go and spend the money. I do have an HKS blowoff valve, but I would need the blower output tube(one that goes between the blower and TB) machined, drilled and tapped for the valve. I should have done that when I was working and had access to a machine shop. Would that cause a problem with max boost though? I still see 12-13psi at about 5500 rpm which is where it's been ever since I got the blower.

Post by **EDS50** » Fri Jul 10, 2009 9:12 am

Odrapnew wrote:Hmmm, I wonder if that could be the problem. I'll see if anyone local has one I could try before I go and spend the money. I do have an HKS blowoff valve, but I would need the blower output tube(one that goes between the blower and TB) machined, drilled and tapped for the valve. I should have done that when I was working and had access to a machine shop. Would that cause a problem with max boost though? I still see 12-13psi at about 5500 rpm which is where it's been ever since I got the blower.

Being that you have an HKS and you are not seeing a drop in boost you should be good. But yes if the blow off valve spring or diaphragm is weak it will bleed off and not hold boost. When not in boost conditions a faulty bov will also leak excessive vaccuum and not clamp down properly at lower loads. The window of rpms that you are going lean is miniscule; I would try to enrichen that 200 rpm window with the addition of a little fuel or the subtraction of a degree or two of timing in that area.

Odrapnew · Post by **Odrapnew** » Fri Jul 10, 2009 9:27 am

EDS50 wrote:
Odrapnew wrote:Hmmm, I wonder if that could be the problem. I'll see if anyone local has one I could try before I go and spend the money. I do have an HKS blowoff valve, but I would need the blower output tube(one that goes between the blower and TB) machined, drilled and tapped for the valve. I should have done that when I was working and had access to a machine shop. Would that cause a problem with max boost though? I still see 12-13psi at about 5500 rpm which is where it's been ever since I got the blower.
Being that you have an HKS and you are not seeing a drop in boost you should be good. But yes if the blow off valve spring or diaphragm is weak it will bleed off and not hold boost. When not in boost conditions a faulty bov will also leak excessive vaccuum and not clamp down properly at lower loads. The window of rpms that you are going lean is miniscule; I would try to enrichen that 200 rpm window with the addition of a little fuel or the subtraction of a degree or two of timing in that area.

Woops, what I meant was that I am running the factory bypass right now, but I have an HKS on the shelf that I could install but I need some machining done to be able to use it. Reducing timing would cause the car to run richer? If so, I'll try that to see what happens.

Post by **EDS50** » Fri Jul 10, 2009 9:52 am

Odrapnew wrote:
EDS50 wrote:
Odrapnew wrote:Hmmm, I wonder if that could be the problem. I'll see if anyone local has one I could try before I go and spend the money. I do have an HKS blowoff valve, but I would need the blower output tube(one that goes between the blower and TB) machined, drilled and tapped for the valve. I should have done that when I was working and had access to a machine shop. Would that cause a problem with max boost though? I still see 12-13psi at about 5500 rpm which is where it's been ever since I got the blower.
Being that you have an HKS and you are not seeing a drop in boost you should be good. But yes if the blow off valve spring or diaphragm is weak it will bleed off and not hold boost. When not in boost conditions a faulty bov will also leak excessive vaccuum and not clamp down properly at lower loads. The window of rpms that you are going lean is miniscule; I would try to enrichen that 200 rpm window with the addition of a little fuel or the subtraction of a degree or two of timing in that area.
Woops, what I meant was that I am running the factory bypass right now, but I have an HKS on the shelf that I could install but I need some machining done to be able to use it. Reducing timing would cause the car to run richer? If so, I'll try that to see what happens.

Yes, if you pull a degree or two out at that specific rpm range it may fix your problem. Or you can just add a little fuel there. Either way should work. Try it and see if it fixes the problem.

Odrapnew · Post by **Odrapnew** » Fri Jul 10, 2009 10:08 am

Well, I just downloaded the new BE and the fn1360 table to be used with my computer(a9s-gufa strategy) so I'm going to mess with it a little bit in the lean range. I know my afr's wont be right where lamse's are, but if I can get my afr's in the right range(below 15) I'll be happy. Up until now, the gufa only had the Base OL table(fuel based on load and temp) and that was causing the inability to tune in the small rpm range.

Post by **EDS50** » Fri Jul 10, 2009 10:14 am

Odrapnew wrote:Well, I just downloaded the new BE and the fn1360 table to be used with my computer(a9s-gufa strategy) so I'm going to mess with it a little bit in the lean range. I know my afr's wont be right where lamse's are, but if I can get my afr's in the right range(below 15) I'll be happy. Up until now, the gufa only had the Base OL table(fuel based on load and temp) and that was causing the inability to tune in the small rpm range.

I noticed a difference when I updated to the fn1360 table. AFR numbers were mcuh more stable and where I expected them to be. That upgrade alone may fix your problem as it got rid of alot of my lean spots.

Odrapnew · Post by **Odrapnew** » Fri Jul 10, 2009 1:10 pm

Well, I just got back from messing around with fn1360. I still have some more messing around, but I noticed that the lean condition appears to be more pronounced coming off closed throttle(idle and shifting). It'll spike lean(>16) until I make it past 1900 rpm(commanded afr of 13.5), then it'll go really rich. At freeway speeds, it runs in the low 14's between 1600 and 1900 rpm, and once I get above that, it goes really rich(12.5) and stays there even with a commanded afr of 14.5.

Odrapnew · Post by **Odrapnew** » Fri Jul 10, 2009 2:19 pm

Something isn't right.

If I'm starting from a stop, afr's will increase to around 16(and will stumble) until I pass 1900rpm and it'll drop a little to about 15 until I shift at about 3000 rpm, this is with a commanded afr of 12.5 at 1750 and 14.5 at 2000.

If I'm just accelerating from about 1200 rpm through the range, it'll run up to 14.5 through 1800rpm, and drop slightly to 14 once I make it to 2000 rpm. This is all with a commanded afr of 12.5 at 1750 and 14.5 at 2000 rpm and up.

OH, and I did do a quick vacuum leak test by plugging the pvc and the line that goes to the vacuum tree, no change(except no power brakes).

347ranger · Post by **347ranger** » Fri Jul 10, 2009 9:50 pm

whats your oil pressure doing when this happens? i ask because its possible the lifters are pumping up a little at 1900 rpm causing a change in valve timing. also can you post your tune? maybe something else is off.

Going lean at a specific rpm.

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