Ok guys, I have a lean spike at 1800 rpms. I have the VE tuned perfect at 1600 and 2000 cells.....I get a nice 14.3-14.6 in those cells(open loop tuning). So, I'm think its more MAT inverse table......I can't tune VE at 1800 rpms only 1600 and 2000 and those are great so.....why the spike at 1800....?

If it is the MAT inverse table....where do I need to start modifying it?

I guess I should say when I hold it at 1800 rpms in a constant throttle...the A/F ratio is 15.1 and when I accelerate to it and hold 1800 its betwee 14.9 and 15.4.....so I'm thinking that at that rpm that airflow might be off base......?

You could tweak inverse MAT table (intake tract heating model table), but it is airflow dependent. Which will affect all areas of RPM & MAP at that airflow.

Along the same lines the small injector PW compensation could be tweaked. Again it is a universal change.

Can also increase the VE slightly in the 1600 and 2000 RPM rows.

Maybe a combination of these would do the trick without overly affecting other areas.

What you are running into is why I like large VE tables with lots of resolution. At first glance it seems that they are a lot more work to tune in. But in the end they aren't any more work and are actually less work. And the engine runs better.

If there isn't a driveabiliy issue, I consider it good enough. Sometimes we get caught up in what the data is showing. When we need to shoot for driveability.

RBob.

Well..I would love to get a table of 1800rpm VE table...maybe someone will do this.

It is a performance thing not just a data thing, I saw it on the data but I usually look at the data then the feel of the engine and at 1600...power is fine and 2000 power is fine but at 1800....I'm down what feels to be like 20-30 ft lbs...it kinda throws you forward instead planting you in the seat at part throttle.

LARGE VE tables, especially in the lower rpm range, where you are going to spend 95% of your time are GREAT. I would trade resolution above 4,500 rpm for more under 2,400 rpm ANYDAY.

I decided against the 7730 ECM and have used both the 7427 PCM and the EBL to run my TPI setup. I have had good luck getting both of them to run properly. I even ran the TPI setup on the 85mm LS1 MAF setup with the 7427 PCM without too much difficulty. The EBL has thus far been the easiest to tune and ran the strongest at all operating conditions. I am tuning ALL the setups in OPEN loop using a Wideband and directly inputing the information into the datalogs. For the EBL setup, I let the HUD software self-tune the VE tables. Got some interesting results, especially on the low-speed table, but I have also run several 100+ mile trips with the laptop and logged over 200 MB of information through the EBL. I just let it do its thing and have tweaked the timing, AE, and DE. I am currently running with the EBL. It is working GREAT with TPI, the little exception being a slight surge as I exit DFCO and the injectors stick to asynch for a second or so (WANT TO DISABLE ASYNCH!, but have not been able to yet).

Fast,

I had a similar spike in VE in my LOW speed table right in the 18-1900rpm range.

Fast...nice tables...I would love to do that...I am using Tuner Pro RT at the moment. The thing is....1700 and 1900 are perfectly fine....1800 is where it goes crazy.

When I say perfectly fine, I mean they are the same A/F as 1600 and 2000. 1800 just goes lean for some reason.

Although the info might be posted, what code are you running?

SAUJP

We have noticed a simlar issue on code59 at a different rpm level. (2600).

Being both are still GM code, wonder if they are related. I think this is something most people have never noticed, yet may have been there all along.

Something with interpolation maybe. Hopefully somebody else has some input.

It was really bad in closed loop then since I've been tuning in open loop its gone away until recently when I relocated the air filter from the throttle body to sit on top of the radiator. And being it really started with that...just leaves me to believe its air flow related.

What mods were done to the EBL to be able to drive the 8 injectors? Which injectors are you using for this? Since we're "local" to each other, I may have to see this set up....

The EBL is back from the BETA testing days, box stock, no modifications. It is firing Saturated injectors from 2 Peak and Hold drivers. The only little thing I am still fighting is the darn Asynch mode. TPI and Asynch do not get along. RBob, can this be disabled?

If there is a meet in Grapevine again this year, I might attend. I work right around the corner off of William D. Tate, @ the Jeep dealer.

To disable async mode set these two parameters to 0:

INJ - Async Transition Lo
INJ - Async Transition Hi

As long as the injector resistance is above 14 ohms or so, the PnH drivers are OK. When the 8-cyl Port Mod is done the PnH function is disabled in the ECM. Unless the 4-inj mod is also done, then the PnH function remains (can be used for 8 PnH or saturated port injectors or 4 PnH TBI injectors).

RBob.

Sorry for the hi-jack, we now return you to your regularly scheduled program. . .
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If you plan on staying in open loop try increasing the VE in the adjacent rows. No INT/BLM to pull the fuel back out. Have you checked the injector PW to see if the short PW compensation table could be used? Does it happen at all loads at 1800 RPM, or at one particular load at 1800.

RBob.

not trying to pirate the thread, however, are you saying there are additional bins/hacks availability that allow greater detail in MAP kpa for the uppper ve.?
While I have spent a great amount of time on my tune and it is locked at 128 w/very little int. movement, there are places that are in the "cracks" that can only then be comped w/ timing. I always thought if there were more flexability like the lower table that split (ie. kpa 35, 45, 55, etc.) the cells, much greater accuracy can be gained in the tune (same w/timing table).
mine is the 727/730 ecm

Well...I plan on tuning in open loop to get the VE closer and then trying to switch back to closed loop just to see if it will work this time. I couldn't ever get it right....if not then stay in open.

Its at all loads I've seen at 1800......its about 14.9/15.0 in lite throttle/cruise or if the converter is locked and moderate throttle is applied then it shoots up to 15.4-15.7:1. However, 1600 and 2000 as I've said is fine...nothing above 14.6:1 in those cells and cruise is 14.1 @1600 and 13.6@ 2000 rpms. I know I need to lean those out more but with it spiking in the middle and power being down....I'm not really wanting too.

I have made a new tune....I increased the 25-40 table .35 to .7 in VE at 1600 rpms and 30 kpa at 2000 .35 and lowered 50-60 at 2000 just to get the cruise at a more desirable A/F ratio.

I have more of a feeling its an airflow thing b/c its done this since I relocated the filter from the throttle body to about 13" away from the engine.

Where are the break points in your BLM cell MAP and RPM definitions?

Vernw, I'm in open loop so I don't see why BLMs would be the case.

But anyway...the BLMs in map are set to 25 low, 47 mid and 65 high. Rpm low is 800 and high is 2400.

Does your PW do any decreasing at 1800, compared to 1600 and 2000 (at exact same MAP)?

If so, maybe you have some lingering codes running such as EGR, lean cruise, purge.

If not, then the (likely) either the airflow has a resonance peak there, or the fuel rail has a resonant pressure dip.

If it's at light throttle (MAP less than half of Baro), (as far as I've learned) it's not possible to have an upstream resonance (flow is sonic through the throttle at pressure ratios of 2:1), so only the manifold/fuel side of the throttle has any effect.

If it's at high throttle, anything is game.

What MAP are you at when it goes lean?
There is quite a jump in SA between 70-75 Kpa. (5*) Just a thought that the higher SA would require fuel right at that point.

DUH! Sorry for the stupid question.....

Not a problem man.....happens to the best of us...I just thought you didn't see I was in open loop.
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I have the HSR...EGR is deleted in the tune and on the manifold.

I'm having it from 30-65 kpa lean condition....lite throttle...less than 50%.
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I have the SA tuned around it....I thought about lowering the SA in the 1800 cell just to see if that helps.

Any more advice........

Any way to get a 1800 rpm cell.....looking at it...I dont think the inverse table will help.

Try moving the TV cable 1 click or 2 and see if the lean spot moves.
Could be a point where the motor is waking up and the trans loading changes due to converter efficiency.
Other than that, don't drive at 1800 rpm

What about the SA tables? Maybe you can make the change there instead by lowering the SA.

I have thought about that....that is one my list....right now I have 34.10 degrees right there. 1600 is 33.75 and 2000 is 34.80.
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I'm trying to avoid it but in the city..1800 rpms is common and at 60 mph...I cruise there so...its kinda hard.

Question did you apply a patch to SAUJP? I had a lean problem in that particular area and no matter what I did it was still lean at WOT. It finally boiled down to a bad bin. The only thing I could figure out was that it may have been because of an applied patch.

Well, I noticed teh spike after relocating the filter so....I think the bin. is fine.

I messed with the timing a lot...lowered it in some and raised in others now it is between 14.6-15.1 plus the popping in the exhaust is gone and performance seems to be fine.

Also...got a new question, since I am in open loop....I removed the narrowband o2 just so I wouldn't mess it up and now I have a SES light.....anyway to deal with this?

What filter? If fuel line changed maybe there is a drop in supply at a particular point. Change line length or something and see if the lean spot moves.
8249 bit 6 = Err 13 o2 sensor
824B bit 3 = Err 44 Lean
824B bit 2 = Err 45 Rich
Turn them off, clear your codes and no more light

I meant air filter....I moved it from the throttle body to the top of the radiator using a 3.5" pipe...I'll post a picture to help you see it. Only reason I did it was to get it away from the belt dust and heat from the engine...plus the filter was hitting the TPS sensor a little bit(around the harness).

I guess those bit are in FLAGS correct? They aren't labeled like that in TunerPro RT....I've looked and can't find them....I'm either blind or just not looking in the right place....thanks for the help.