KR elimination

[Foghorn]

Your boost gauge is dependent on the accuracy of your MAP sensor. Get a mechanical gauge on that thing at least temporarily to see what you really have.

Sensors as in plural. The gauge sensor has no effect on the pcm. Test them by looking at the other. If the pcm sensor reads differently than the gauge, further diagnosis would be warranted.

You can even swap the wiring connectors between the 2 MAP (1 is for the PCM and the other is for the guage) sensors to see if they agree.

The boost values you see don't seem out of range (about 68 kPa over atmosphere) given the temperatures. But as you know, I'm a little suspect about your resonator and other exhaaust work on your car.

Did you ever try raising the BCS about 1/4"?

Cheers,

[99ssei]

You can even swap the wiring connectors between the 2 MAP (1 is for the PCM and the other is for the guage) sensors to see if they agree.

Can't hurt to give it a shot. I know the one MAP sensor is on top just after the TB, however, where is the other MAP sensor?

But as you know, I'm a little suspect about your resonator and other exhaaust work on your car.

I agree about the exhaust. Don't have any $ now to start swapping out parts to find out. However, if there was exhaust issues, then wouldn't I be stacking pressure?

Did you ever try raising the BCS about 1/4"?

No, what are the effects with raising it again? I know it affects boost levels but forgot how.

EDIT: Just thinking aloud again...what if the MAP sensor is dirty? Will that have an impact? My brother has a GXP and he took his TB off to clean it and also cleaned his MAP sensor. He claims it was night and day.

[Foghorn]

The 2 MAP sensors are mounted side by side on a bracket above the rear valve cover.

If you raise the BCS you will have less part throttle boost.

The sensor near your TB is the MAF sensor, that's the one that could benefit from a good clean with electronic cleaner.

Cheers,

[99ssei]

The 2 MAP sensors are mounted side by side on a bracket above the rear valve cover.

Ahhh...okay, so I should try switching the plugs that go to each and see what happens?

The sensor near your TB is the MAF sensor, that's the one that could benefit from a good clean with electronic cleaner.

Umm...the MAF is 3 months new. I think I'm confused.. what's underneath the spot, on top of the SC housing, just past the TB that has 3 hoses going to it (not the PCV)? I thought that was the MAP sensor, however, now I'm guessing it's just a hole for the MAP sensors to measure the air pressure in the upper intake?

[Foghorn]

Umm...the MAF is 3 months new. I think I'm confused.. what's underneath the spot, on top of the SC housing, just past the TB that has 3 hoses going to it (not the PCV)? I thought that was the MAP sensor, however, now I'm guessing it's just a hole for the MAP sensors to measure the air pressure in the upper intake?

The MAF could use a clean, wouldn't hurt, doesn't mean to say it was clean when you installed it.

That fitting with 3 hoses on it is a vacuum tap for the power brake booster and other vacuum related devices.

Cheers,

[99ssei]

So the two MAP sensors above the rear valve cover both go to one opening just underneath the SC snout, right?
Just curious, why two sensors for one vacuum line? Is that some fail safe GM put in just to make sure both are reading the same data accurately?

[Ragsdale]

totally ignoring the rest of the thread - where'd you mount your Scangauge on the 99?

[2000Silverbullet]

If you raise the BCS you will have less part throttle boost.

Best suggestion I've seen in a while on this thread.

[99ssei]

This is probably a bad angle, but I put the tape measure right on top of the BCS mount, just above the hold down bolt for the SC housing.

[99ssei]

Grrrr!!! Replaced the ICM and moved the grounding wire from the mount (which was aluminum with metal bolt) to the engine block. No change. Still seeing only 5* timing @ WOT. WTF!?! Here's the scan data.

http://www.scandepot.net/viewscan.php?pk=5653

I noticed that my PCM is calculating Delivered Trans Torque ft.lb in the 450's but I'm not so sure that's happening. Perhaps this is a trans issue? I tried flooring it off the line and I got the tires to spin a 1/2 rotation. That's it!! When I did that, I got 2*KR but overall, KR is down to less than 1* (total counts were 34 out of 3300 frames where I had >0 KR).

Since my KR is under control, should I start a new thread?

[PDXGTP]

But as you know, I'm a little suspect about your resonator and other exhaaust work on your car.

I agree about the exhaust. Don't have any $ now to start swapping out parts to find out. However, if there was exhaust issues, then wouldn't I be stacking pressure?

Disconnect the exhaust right at the collector coming out of the manifolds or headers, and yes I'm suggesting running no cat, no exhaust what so ever.. it will be loud but you can test this way without spending money.

[Allmachtige]

Ken, can you please send me or post your HPT scan file so I can load it into the histograms/graphs?

[99ssei]

Disconnect the exhaust right at the collector coming out of the manifolds or headers, and yes I'm suggesting running no cat, no exhaust what so ever.. it will be loud but you can test this way without spending money.

I'm actually debating about pulling the cat anyway.... I'd like to change my exhaust to 3" all the way into the muffler and keep my dual 2.5" outlets. If I do a swap, I won't put the resonator back in just to be certain that's not the issue. That would be at least an additional $200 that I don't have and I don't have a welder.

[Allmachtige]

Ken I took a look at that scan file you sent me and I noticed some very erratic fueling going on.

Your Injector Duty starts to settle itself as your RPM's reach 6k, plus the Injector B1 graph follows this trend. On my scans I see a nice level msec until a shift, at which point it might spike up to 21, then settle between 19.5-20.1. You are spiking above 22msec at what seem to be random points.

Again, I'm expecting your Inj Duty to keep climbing to near 97% (especially with the msec graph as high as it is) and your injector msec is "bouncing" around .

Did you clean your injectors recently? Maybe run some Seafoam through the intake and put some in the gas tank for good measure. Fuel filter? Obvious things to ask, but just want to be sure.

EDIT: A good way to describe it: it looks like you're injectors start out strong in gear, but fall flat on their face.

[99ssei]

I think we may be on to something....I started another thread on another site and a member there showed histograms how his wideband O2 was reading WOT AFRs of:

11.6:1
11.4
10.6
10.9
11.0
10.5
10.3
9.9

however, the narrow band was showing:

841
903
901
895
889
896
895
908

respectively.
We've been trained that 930-940 is "ideal" however, I'm wondering if this is reality seeing the results above. I'm thinking the wideband O2 is my only hope to get this right (on my x-mas wish list). I've restructured my MAF, added back in the AFR spark correction:


Since then, I've lowered my 7500+hz range by 10% and tonight I'm lowering it another 5% (seeing O2s in the 940-950). With the AFR spark correction and 10% change, I've noticed more power in the butt dyno. Hoping I'm onto something here.

[Foghorn]

Go back and have a look at my suggestions on calibrating a WB. If the voltage offset is 0.2V then the WB results could be quite far off

Cheers,

[99ssei]

Just wanted to give those in this thread an update...

I had an opportunity to swap out my 3.5 for a 3.4 pulley for $20 and I jumped on it. I know, making mods while trying to fix a problem is not the right thing to do here...but I did it anyway. I still had low timing issues, so I did a little research into the whole timing mystery and I found this graphic that might be helpful for anyone.


W/ the 3.4, my first WOT run had no KR, and timing was at 8*. This really baffled me considering I was commanding 11*and my AFR correction is supposed to increase timing by 3* at 11.7:1, then theoretically, the PCM should try to command 14* in those same cells, but it wasn't.

On foghorn's suggestion, I put the BCS all the way up to the highest it can go and virtually all part-throttle KR was gone and the transition from normal to PE felt smooth! Before, I can tell when the car went into PE mode because it felt like it would bog down.

I smoothed out my timing table, changed my Hot PE Enable TPS vs. RPM to 28, made my PE AFR to 11.6, put the factory PE Fuel adder vs. TPS back in, and loaded the PE adder vs. RPM vs. Time back in (we originally zero'd out this table thinking it would remove any fuel adders to the equation). I think adding back in this table really helped out. My O2's were low, but timing was waaayy up!! I've increased the PE adder vs. RPM vs. Time by -.4 to the 3200+ range to get the O2's close.

This morning, my LTFTs were rich by 9% and I adjusted it accordingly.

Now it looks like I have some minor tweaks with the MAF (2% lean). That might clear up some of my KR. If not, then I'll put 1* of timing and see what happens. For the most part, this thread is pretty much over. I've finally got the car back where it should be. And I can tune out the remaining KR.

Thanks everyone for being so patient with me and helping me learn how to tune. I really appreciate all the guidance you've given me. In the words of Paul....Cheers!

http://www.scandepot.net/viewscan.php?pk=5688

[Allmachtige]

Ken, I'd still like to know if its safe that your commanded AFR drops down to 9.8.

[Foghorn]

Mid 13's on a stock valvetrain?

Don't count on it. You'll need at least rockers or a cam to hit that.

True statement.

Anyway, have you replace the fuel pressure regulator yet? Sorry this post is kinda long and I might have overlooked that.

Ummm, you guys are out to lunch, I did on a stock valve train.

I had a CAI, 3.5" pulley, headers and a PCM that I tuned;



Cheers,

[willwren]

Foghorn, if you read my post, I said don't COUNT on it. It's not very common. I didn't say it would never happen. (somewhat of an old topic anyway)