Very lean on part throttle - Third Generation F-Body Message Boards

Ruiner · 06-18-2009, 11:57 PM

Sorry to make another thread, but I think it's a different enough topic to not go in my thread about my ALDL problems, which have since been fixed.

Just finished my L03 TBI to 355 TPI swap, worked out all the bugs (wiring, cylinder select, bad PROM, Y-pipe didn't fit, etc), so I can finally get into the tuning.

It's my first time doing PROM tuning (as well as my first SBC rebuild, first engine swap, all in the first Chevy I've owned), so I'm having to learn as I go (I'm 20 years old, just getting into all this, and loving it so far

), and could use a few pointers

First thing I've noticed driving the car is it goes VERY lean on light throttle off idle, say about 5-10% TPS from idle to 2500 rpm or so, to the point of missing badly and almost stalling. Once the RPM goes higher or I give it more throttle it gets a lot better and my O2 reads about 700mV.

I haven't gotten to the point of tuning the VE tables yet, but I backed off some SA and lowered my injector constant and it got a little better. I'm running about 48psi fuel pressure (with vac hose disconnected) with 24lb/hr LT1 injectors

The engine is a 355 TPI (speed density, '7730 ecm), 10.5:1 compression, 2.08/1.6 aluminum heads, Comp 268xfi roller retrofit cam, 1.5 rockers, ported intake base/plenum, shorty headers to a 3 inch catback

Any suggestions? Or is more information necessary? I can do some datalogs, but I really don't like running my brand new engine with it running this lean, I feel like I'm going to damage it or something, I need to get it running better before doing more tuning

thanks

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Ruiner · 06-21-2009, 01:28 AM

all right I played with the AE tables a little bit just to get the car drivable, did a few datalogs.

Most of my problems are in the 1400 - 2600rpm range, 80-90kpa, 5-10%tps. O2 voltage just goes to zero and stays there until I either let off the throttle or give it a lot more (going into PE???).

Quick question, when I reflash a chip, does the computer's learning reset? Or do I still need to pull the battery cable to do that

Also, when updating a bin using the NVSRAM GUI, it always hangs at 4% then says "ALDL error" but it seems to take effect, is this normal? If I "dump eeprom" I get the correct PROM image, but if I hit "dump bin" (assuming that dumps the eeprom plus NVSRAM changes) it just dumps garbage data. Ideas?

Posted log, rename to .csv

I deleted a few unnecessary columns to get the file size down (WB o2 stuff that's not enabled, my VSS doesn't work, etc).

My BLM's are pretty low across the board though (108-114), I had tried to raise the fuel pressure to see what effect that would have, primed at 48psi, just trying to rough in the tune at this point, I've read all the tuning articles so I'm pretty familiar with the terminology and so-so at using TunerPro, still learning how to use all the advanced features like data tracing, etc. Played with it a little bit in the VE table vs BLM, starting to understand how this works

djxib · 06-22-2009, 09:09 AM

Quote:

Originally Posted by Ruiner

all right I played with the AE tables a little bit just to get the car drivable, did a few datalogs.

Most of my problems are in the 1400 - 2600rpm range, 80-90kpa, 5-10%tps. O2 voltage just goes to zero and stays there until I either let off the throttle or give it a lot more (going into PE???).

Quick question, when I reflash a chip, does the computer's learning reset? Or do I still need to pull the battery cable to do that

Also, when updating a bin using the NVSRAM GUI, it always hangs at 4% then says "ALDL error" but it seems to take effect, is this normal? If I "dump eeprom" I get the correct PROM image, but if I hit "dump bin" (assuming that dumps the eeprom plus NVSRAM changes) it just dumps garbage data. Ideas?

Posted log, rename to .csv

I deleted a few unnecessary columns to get the file size down (WB o2 stuff that's not enabled, my VSS doesn't work, etc).

My BLM's are pretty low across the board though (108-114), I had tried to raise the fuel pressure to see what effect that would have, primed at 48psi, just trying to rough in the tune at this point, I've read all the tuning articles so I'm pretty familiar with the terminology and so-so at using TunerPro, still learning how to use all the advanced features like data tracing, etc. Played with it a little bit in the VE table vs BLM, starting to understand how this works

The only thing I would say is that low BLMS is rich, not lean (i.e. opposite to O2mv), so while raising fp might help your low throttle lean condition, it will worsen the BLMs. Part-throttle problems is often AE, but I would defer to others on this forum for expert advice.

Drumer919 · 06-22-2009, 12:49 PM

Why did you lower your injector constants?

You need to increase your VE's.

Ruiner · 06-24-2009, 03:53 AM

Ok I've lowered my FP down to 45psi w/o vacuum and returned the injector constant to match the injectors (24lb/hr)

I've just been tuning with the VE tables so far, had to raise them considerably in the 1400-2400rpm range, from 40kpa and up.

However I've noticed something weird when playing back my datalogs with data tracing, not sure if it's a problem with tunerpro, the .ads file, or the bin. When in the 1600rpm row of the VE table, the highlighted boxes in the lower VE table jump between the 400rpm row and the 1600rpm row, but in the same MAP column.

If it's in the bin it means S_AUJP_v4 isn't addressing the lower VE table properly, and definitely would explain my lean condition, especially around 1600rpm

Here's a screenshot to explain what I mean (look at the VE table and look below, 1600rpm)

Ruiner · 06-25-2009, 02:51 AM

Hmmm I just reflashed my prom with a modded AUJP off of moates and it's WAY closer to what it should be, still runs slightly lean at 1600-2000, but not to the point of misfire/hesitation. I've since richened the VE table in this range and it's pretty much gone, haven't done a datalog yet

So I'm pretty sure my S_AUJP got corrupted, I haven't noticed the wraparound problem with the lower VE table with this bin, too bad it doesn't support the NVSRAM.

I guess flashing with the willem isn't that bad, it's just that my laptop doesn't have a parallel port so I have to borrow my room mate's PC

bl85c · 06-25-2009, 11:50 PM

Stop trying to tune with the nb, it's little more than a switch. You really need a wb to tune effectively, otherwise you're just shooting in the dark unless you have more experience. There is a method to the madness when tuning with the BLM/INT though. As I assume you have already read the idea is to adjust your ve cells to get 128 BLM/INT at all points in -steady state- operation. You'll always have a small lean flash at throttle tip-in, messing with the accel enrich tables helps but it's very hard (impossible?) to eliminate that lean flash when you stomp the peddle.