dyno results and A/F ratio

[Craig 94 TA GT]

Steve and I tested a short WOT run with the stock tune...reading the fuel pressure, scanning it, and trying a Delco plug in there.
The fuel pressure showed no loss. It was high, steady and well at WOT...around 48 psi, exactly the pressure with the vacuum line off the FPR at idle.
The NGK plug, previously cleaned, turned a bit white, but not as white as before. I'm thinking it's because it was only a sprint to 50. The Delco plug has white spots, and wasn't as white as the NGK. But it still showed hot, in my opinion.
And after quickly viewing my scan, one thing popped up. At 5500-5800 RPM, the MAF reading showed 280 to 282. That seems awfully high considering it should be around 240 Does this mean anything?
Could this have anything to do with rocker adjustment?
Thanks again for your guys' help.

[Kevin - Blown 95 TA]

And after quickly viewing my scan, one thing popped up. At 5500-5800 RPM, the MAF reading showed 280 to 282. That seems awfully high considering it should be around 240 Does this mean anything?
Could this have anything to do with rocker adjustment?
Thanks again for your guys' help.

If the MAF reported more air than you were really getting, wouldn't it then command the PCM to add fuel resulting in a richer mixture? What did the O2 sensors read at WOT? And what were your injector pulswidths at the highest RPMs for all of your runs?

[Craig 94 TA GT]

We thought the same...if the MAF reported more air than actual, then it should be richer Doesn't make sense, so either it doesn't have anything to do with the problem, or maybe a faulty MAF in general will screw up everything

Pulse widths showed between 20 and 21 at the highest points. I'm not sure what units they use to measure it though. I'll recheck the scan in my other computer but the O2 readings, if I recall correctly, was > .9

[Injuneer]

Pulse widths are measured in milli-seconds. 21mS is pushing close to 100% duty cycle at 5,800rpm (it only takes 20.690mS for the engine to complete 2 revs). Might be on to something. Injectors don't like to be pushed that hard, and fuel flow can be reduced seriously when the injector starts to lose control, never fully closing and never fully opening.

On the other hand, what scan system are you using? If its DataMaster, the BPW numbers that it shows are often unrealistic, at least from the many DM scans I have looked at.

[Craig 94 TA GT]

Thanks as usual Fred for the great info.

I hope this will lead to finding the problem. I'm using Freescan. The injectors hang between 19 and 21 at 4300+ RPM. I just noticed that it only hit 21 once, though. The MAF is reading 233 gps at 4800 and gets up to 282 at 5775. The O2s show .95/.924 at the highest point, 5775. Well, I'll just post the CSV file.

http://s94938520.onlinehome.us/stock_tune_wot.csv

EDIT
I don't know if this will help, but I just found a previous WOT run, long before the headers, before cleaning the MAF, and with the MBA ends on. Not sure if I had a lean condition then, but I'm pretty sure if I did, it wasn't as bad as now. At the highest point, 5925 RPM, the MAF read 252.83 gps, pulse widths were at 17/18, and O2 readings at .955/.959. At 4800 RPM, the MAF read about 220. At 4300+, Injector pulse widths were at 17-20, hitting 20 at only a couple points. I'll try to get it posted, but I'm not sure if it'll be of any help.

[Z Ya Later]

Pulse widths are measured in milli-seconds. 21mS is pushing close to 100% duty cycle at 5,800rpm (it only takes 20.690mS for the engine to complete 2 revs). Might be on to something. Injectors don't like to be pushed that hard, and fuel flow can be reduced seriously when the injector starts to lose control, never fully closing and never fully opening.

On the other hand, what scan system are you using? If its DataMaster, the BPW numbers that it shows are often unrealistic, at least from the many DM scans I have looked at.

Ya know Fred, that actually sounds like a logical source of the lean condition. If the MAF is reporting the wrong amount of airflow and the PCM starts pushing the injectors too hard, that would result in the lean condition. Am I right on this? If so, that would mean the MAF is causing the problem, right?

You da man Fred

[Injuneer]

Yes... when the duty cycle hits 85-90%, the injector flow rate and spray pattern can start to deteriorate. So seeing a higher mass air flow could call for large pulse widths the hurt the injectors.

Just keep in mind, a 21mSec pulse width at 4,300rpm is not a problem, since at that rpm, there are 27.91 mSec available in 2 revs of the crank. It would only be at 75% duty cycle.

The thing that bothers me is that is goes lean (at least on the dyno chart) almost immediately. That isn't consistant with our theory. If it was a duty cycle problem, the A/F ratio would start out OK, then go lean as the engine reached higher RPM.

Not sure if the duty cycle thing holds water....... (or gasoline )

[Kevin - Blown 95 TA]

I looked at that CSV and sorted the data by RPM, then Throttle Position. The only thing that data shows is that the Left side is reporting richer than the Right side, but neither seems out of line except for the split. I am more comfortable with the Left side numbers, though. There might be some imbalance from left to Right, but the average coming out of the tail pipe (before the cat) shouldn't show a problem unless both of your O2 sensors are really out of whack. None of your part throttle BLMs are abnormal. The engine appears to be the leanest in the mid-rpm ranges with it richening up just slightly at the higher rpms like the stock PE/RPM table tells it to. I couldn't tell what gear you were in, but the road speed numbers don't make sense if you were in a higher gear like you're supposed to be.


Got any more data?

[Craig 94 TA GT]

Fred, you're right...looks like another theory possibly out the window.
Even though this doesn't explain the lean at part throttle lean condition, I'm still wondering why the stock internal motor is pushing well over 90% duty cycle at very high RPMs. Have you seen MAF readings that high at WOT on stock internal motors? Or pulse widths/duty cycles this high?

Kevin, I noticed the imbalance too. I've always seemed to have this problem, probably years back. Looking at a longer scan, at part throttle the driver's side generally shows more pulse width, but sometimes the passenger's side will exceed it. Of course, at WOT, though, the driver's side seems to be on top most of the time. And the WOT run was done in all of 1st gear, 0-44 I believe, and continued for a few MPH in 2nd. I have more part throttle data, but not WOT data. Once I clean the MAF, I think I'll try another WOT scan and post it.

I'm now out of ideas since these scans don't seem to show why it's lean throughout the band. Maybe I'll try another MAF cleaning, or just replace the MAF just for the heck of it. Maybe trying to solve why the duty cycle is high at high RPM would lead to finding more about the problem?

Thanks again Fred and Kevin for your help. I really appreciate you guys taking time to help me in this situation

[Craig 94 TA GT]

This may not be anything, but I just looked at the part number on my injectors. They're 17124187. They cannot be found much anywhere. All I know is that they're ~24 lb/hr, most likely, according to some sites. The stock injector is 17124248

EDIT:
Well, I guess the injector p/n doesn't matter so much. I don't know how accurate this source is, but it says 17124187 superceeded 17095004 which is 260 cc @ 3 bar, or ~24.7 lb/hr. http://www.witchhunter.com/FlowDataPix/rp17095004.jpg I guess the p/n is not the same, but the ratings seem very close.
Sorry, that kind of lead to nowhere.

[Craig 94 TA GT]

I cleaned up the MAF again, and replaced the O-ring seals between the MAF and the ends. Then, I did another WOT run. But apparently I was letting off at some RPM. I could swear I had it down to the floor, but the scan shows otherwise
It looks like very similar readings. At 5600, the MAF reads 262 gps, very similar to the previous scan. And injector readings are similar, maybe a bit lower, at about 90% duty cycle at peak RPMs. The NGK plug showed "powdery" white again, and the Delco plug showed more of a grayish white tone..but again, not nearly like the NGK.
I'm not sure what else to do. I think I may have an exhaust leak because everytime I'm driving by a curb, I can hear what sounds to be a leak. That should make the leaking side run richer, and completely invalidate a lean condition though. Maybe I'll get that fixed and go from there

Sorry, I forgot to put the link for the csv.
http://s94938520.onlinehome.us/stock_tune_wot2.csv


EDIT
I didn't even look until know...I just noticed up to 4.3 degrees of knock retard, and I see knock retard for the whole WOT run until I let off the gas. And I also scanned normal driving conditions...and notice up to 0.4 degrees of knock retard for no reason. It could be cruising on the freeway: steady on throttle position, MPH and RPM, for a few seconds, knock retard will appear (.1 to .3). Or from a stop light, accelerating normally in 1st, I've seen up to 0.4. I don't know what is causing this, why the KR is appearing now, and if this is related to the problem?

[Craig 94 TA GT]

I am going to go out on a limb with a new, completely different theory. I'm no expert, so this may not make sense to some. I thought of this because the lean theory just doesn't add up regarding the scans, and the "no appearance" of vacuum leaks.

I think what the dyno saw was a fake lean condition. I believe I have an exhaust leak, which seemed to have made itself louder now. SLP shipped me a shoddy workmanship y-pipe, such that the ring that holds the gasket is off-center. http://s94938520.onlinehome.us/pictures/gasket2.jpg
Thus, the gasket is off center, and never seals the header->y-pipe. I thought I tightened this hard enough for no leaks, but now I'm beginning to think otherwise.

I believe the dyno operator placed the wideband in the driver's side bung. That places the sensor 2 inches from the possible leak. At WOT, it was reading so much air from the leak, that it showed the very high A/F ratio. But in reality, since the BLMs were previously higher under part throttle, that made the PCM attempt to compensate for a fake lean condition. So now, the overly rich driver's side has enough unburned gas. It burns in the headers, which makes the exhaust overly hot. This, combined with the lean A/F reading made the motor appear lean.

So the overly rich condition would have some part of why it's down on some power. And why the injector duty cycle shows to be over 80% at 4800+, and 90% at 5375+.

This doesn't explain, however, why the plugs are white, not black or carboned from a supposed overly rich condition. Nor why the plugs on both banks are the exact same color. And I'm still wondering why the injector duty cycle hits 80% at 5000, and 91% at 5750 for the passenger's side too.

That's why, now, I'll get the exhaust fixed at a professional shop, to make sure there are 0 leaks. Then, I guess more testing, observation and dynos can be done to see what's really going on.

[fastTa]

I am going to go out on a limb with a new, completely different theory. I'm no expert, so this may not make sense to some. I thought of this because the lean theory just doesn't add up regarding the scans, and the "no appearance" of vacuum leaks.

I think what the dyno saw was a fake lean condition. I believe I have an exhaust leak, which seemed to have made itself louder now. SLP shipped me a shoddy workmanship y-pipe, such that the ring that holds the gasket is off-center. http://s94938520.onlinehome.us/pictures/gasket2.jpg
Thus, the gasket is off center, and never seals the header->y-pipe. I thought I tightened this hard enough for no leaks, but now I'm beginning to think otherwise.

I believe the dyno operator placed the wideband in the driver's side bung. That places the sensor 2 inches from the possible leak. At WOT, it was reading so much air from the leak, that it showed the very high A/F ratio. But in reality, since the BLMs were previously higher under part throttle, that made the PCM attempt to compensate for a fake lean condition. So now, the overly rich driver's side has enough unburned gas. It burns in the headers, which makes the exhaust overly hot. This, combined with the lean A/F reading made the motor appear lean.

So the overly rich condition would have some part of why it's down on some power. And why the injector duty cycle shows to be over 80% at 4800+, and 90% at 5375+.

This doesn't explain, however, why the plugs are white, not black or carboned from a supposed overly rich condition. Nor why the plugs on both banks are the exact same color. And I'm still wondering why the injector duty cycle hits 80% at 5000, and 91% at 5750 for the passenger's side too.

That's why, now, I'll get the exhaust fixed at a professional shop, to make sure there are 0 leaks. Then, I guess more testing, observation and dynos can be done to see what's really going on.

Well unfortuntely plugs don't lie, widebands, MAF's, and O2 sensors can. The insulators on your plugs definitely appeared to be abnormally white which reads lean. But something is definitely up.

It appears that your PCM is adding pulsewidth to compensate for a condition in which it believes that requires adding more fuel than normal. If your pulsewidths exceeded 21 ms above 5500 RPM, I would be concerned. But so far your PW's don't seem that unruly. Weird to say the least. Could be something is up with your PE vs. RPM or PE vs. Temp tables, maybe a faulty TP sensor?

Is your MAF and ends stock? Do you have the screen in place?

[Craig 94 TA GT]

Kevin, thanks for pointing out the theory holes It seems that no explanation, at the moment adds up.

The MAF ends are stock, with the screen and all. I used to have MBA ends, but put the stock ones back on about a year ago. I just cleaned it throughly again, but seemed to have no effect on gps readings.

According to the scans, the TP sensor seemed accurate, but I can't be 100% sure. Would faulty PE vs. RPM, or PE vs. temp tables be due to a bad PCM? Or would it be due to the current program? The scans were done with the stock tune, and dyno with the PCMforless tune, if that makes a difference.

How would carbon deposits look on plugs? They wouldn't appear to be white-like or darker in color? I was able to clean the current white NGK plugs with a wire brush and a bit of seafoam. Does that still mean it's lean...if you can clean them off fairly well?

[fastTa]

Craig, if you can post a csv scan file showing your PW and RPM's with your PCM4Less tune, I will make you a duty cycle chart. It just helps sometimes to look from different perspectives you know.