Finished the mechanical work on my 86 Vette - new TFS heads and camshaft, Edelbrock intake & runners, new 24# SVO injectors, new plenum and TB. Got a chip burned from Alvin for the new equipement, but seem to be having a problem with the idle. Did min air adjustment, TPS adjustment, and even upped the min idle in the last BIN in the coolant temp to rpm table.

Have attached a link to a data log file to give you something to look at. 86 Upgrade Data Log

From my very limited understanding it looks like it is running lean (160 BLM) in BLM cell 0 (TPS at .53), which must be the idle cell of one the tables I need to know and understand. With any throttle movement the motor quickly goes to BLM 128 and looks and feels good. Despite lean idle indication the car smells and seems like it is running rich however (upgraded from stock '86 injectors, 22# I believe, to the 24# Ford SVO injectors - where whould I see this difference accounted for in the $6E mask?)

Appreciate both detailed assistance and any general "here's how to get smart and get started" direction. Have read various articles describing Integrators, pulse widths, and VE tables, but all I see in my TunerPro $6E template are much more detailed and confusing tables and constants. Where are the best resources to gain how to analyze your data log and then know what items to change.

Ross

 

Im in the process of tuning my vette also. I've been doing alot of reading for about a month and the best site to learn from is thirdgen.org. There is a vast amount of knowledge there regarding our ecms.

 

Doesn't Alvin keep updating your chip till all looks good ??

 

Disconnect your battery.

It seems that you have some bogus blm data stored for cell 0.

Go for a drive to get the O2 sensor nice and hot so it goes "ready" to put you into closed loop. Then try and get it to idle briefly while its still in closed loop. If it drops out of closed loop at idle quickly, start driving to re-heat the O2 sensor and bring to idle again.

Next time the car goes into closed loop the blm will be starting from 128 and should correct itself as required.

Repeat as necessary. Cell 0 should contain similar BLM values to the nearby cells.

 

Thanks for the inputs. Agent86 - Have sent request for help and $$ to Alvin - want to do whatever I can while waiting. To Tequilaboy - thanks for the tip - I did reset by disconnecting battery and from the datalog the 160 BLM left - but then it varied both higher than and less than 128. Can you help explain where I could find the table that has the cell zero. Also I installed a heated O2 so am guessing there is not a problem with it not running in closed loop, and was getting various millivolt readings on the datalog from the O2 sensor. Is there a good place you recomment in the $6E mask to check closed loop parameters?

Thanks

 

Start reading

http://www.thirdgen.org/techboard/di...uide-book.html

 

Cell 0 is under 700 rpm and under 12 grams/sec.

The primary tuning parameter that comes into play for this cell is MAF table #1 which covers the MAF calibration up to approximately 23 grams/sec.

How far is it deviating from 128? I would consider +/- 4 to be pretty good.

The MAF calibration and temperature compensation is not likely to be perfect all the time, so it is not uncommon for the BLM to vary over differing ambient air conditions.

If the BLM is consistenly deviating above or below 128, you can adust the MAF calibration via MAF table #1 value adjustment to raise or lower the airflow as necessary for a good fit. More air flow for a given sensor output voltage means more fuel and vice-versa.

Fuel pressure and the injector constant also come into play, but these will result in global changes, so only use as necessary.

How big is the camshaft? You may be getting some extra air in the exhaust that is interfering with the O2 sensor readings, or you may have exhaust leaks that could be introducing air.

 

Here's an update - took everyone's inputs and got serious about this tuning. Got up and running with a TunerPro $6E mask with an AutoProm as the ALDL connection. Also started dataloging with TTS DataMaster (what Alvin requires) using the AutProm in it's passthrough mode.

In both software packages saw intermittent closed loop operation that resulted in both a code 13 (O2 sensor) and a code 45 (mixture rich). Ran through the trouble shooting guides (Thanks Agent86) and narrowed it to the sensor which I replaced. Still seeing intermittent closed loop, but had clear indications of overly rich mixture across the fuel trim cells. Had installed larger SVO 24# injectors along with the heads and camshaft - though I thought this was considered in my last BIN update from Alvin. Anyway here is a snapshot from DataMaster that shows the mixture problem:



Will work with Alvin on tune updates but appreciate and inputs, recommendations or ramblings on the following topics
1 - What is the likely cause for my intermittent closed loop? - Wiring to the heated O2 looks good, tested with VOM, and its a new sensor. Any chance it could be the richness of the mixture? What's best way to check that the heater works as desired - any engine variables in the datalog that can help - Also should I check for closed loop timing constants and O2 mV turn on constraints?
2. How do experts like Alvin use the data from DM to make BIN changes? The TTS program appears to only provide logging - doesn't seem to give acces to the BIN tables and constants like I have in TunerPro. They must use another program right? Also, is there any kind of an equivalent view like DataMaster's histogram in TunerPro (like it) - none of the TunerPro BIN tables that I can view seem to have a clear clean break out the VE by RPM and airflow with BLM and INT overlays.
3. What's best way to clear codes without having to loose all your BLMs? If the SES light extinguishes I assume that means the malfunction condition is no longer present even though the codes will stay for what 45 more starts or something. In TunerPro, in the ALDL datastream definition for the $6E there is a "Clear Trouble Codes" quick-send command along with a "send command" button, but it doesn't seem to work (at least while the engine was still running). Any TunerPro tricks here that I am missing?
Thanks!

 

If you've gone with larger injectors and have not lowered the FP, the BPW Constant (Base Pulse Width) needs to be modified to "tell" the ECM there's more fuel flowing for the same PW. If that hasn't been done, it would explain the "rich" condition. Also, a more aggressive cam with more overlap may require playing with the O2 sensor voltage v airflow calibration. Try this to begin understanding how guys like Alvin do it.

http://www.thirdgen.org/techboard/di...uide-book.html

 

To address the richness, you have a couple of options:

Increase the injector constant for global enleanment
Decrease the fuel pressure for global enleanment

Since this is a MAF car there is no VE table. The MAF measures the airflow and there are 2 options (switch settings) to determine basic fueling. Base pulse width calculation from airflow (default setting) or the BPW vs rpm vs load table can be used.

Load is calculated from airflow/rpm, so the MAF is still relevent even if the table is used. The table is usefull if you run into non-linear behavior vs rpm that causes too much of a comprimise in MAF scaling for one cell or another.

So far, I've stuck with the base pulse width calculation from airflow instead of using the bpw table. This is how the production bins are set up.

For fine tuning of the 16 blm cells, you can look at the classic histogram. This will show you the cell numbers and rpm and maf flow conditions for each cell.

To adjust the airflow up or down as required to enrichen or lean out a cell is a simple matter of adjusting the MAF calibration table in the region of the relevant air flow in grams/sec for the appropriate (and nearby) cells.

Try and achieve a relativley smooth calibration curve that is a good comprimise for all cells. It shouln't be too difficult to get all the blms in reasonable order.

If you get to the limit of any one MAF table, you can either adjust the injector constant again as required, or use the maf scalars to rescale the maximum value for each appropriate MAF table, and then rework the vaues inside the table again to fit with the new maf scaling. This shouldn't be necessary unless the maf calibration is way off in the sensor itself.

Regarding your intermittent closed loop, look at the O2 signal behavior. The O2 needs to be above 700 mv or below 300 mv to go ready, once it is ready and if the mixture is anywhere near 14.73, you should see rapid swiching with fairly large voltage swings. If it is spending too much time in between these voltage levels (looks like a cold sensor), you will drop back out of closed loop.

 

Making the BPC larger tells the ECM you have smaller injectors which will
cause an even richer condition. I think you mean make the injector look bigger to the ECM, correct?
Reducing the BPC will make the A/F mixture leaner overall. However, addressing the O2 sensor voltage will allow you to address mixture as the airflow is affected by the camshaft characteristics. Particularly helpful for idle condition of larger overlap cams.

 

So if you tell the ECM you have smaller injectors in the injector constant, the engine will globally run Richer?
IE a constant of 30 to a 29 will make it run richer?

 

Lowering the BPC tells the ECM you have a LARGER injector and so the pulsewidth doesn't need to be as long. This LEANS out the mixture. The converse is also true if you want to make a "global" change. One other way of richening or leaning the mixture globally is to modify the
Injector Bias which tells the ECM how much "lead time" the injector needs to open. The change in IB isn't as dramatic as the BPC modification.

 

Here are the injector constants in $6E. Increasing the values with an editor makes the ecm think the injectors are larger which reduces the overall pw needed to deliver a quantity of fuel, making the mixture globally leaner. Reducing the values with an editor has the opposite effect.

Note: Since the actual values are used in the denominator in the calculation, reducing the value directly increases the constant and vice-versa. However, this is taken care of by the editor programs like tunerPro or tunercat, so you can increase or decrease the injector constants (lb./hr) accordingly for the desired effect.

;----------------------------------
; INJ FLOW RATE
; 22.3#/HR INJECTORS
;
; Double Fire #/h = 10158.8/cal val
; Single Fire #/h = 20317.6/cal val
;----------------------------------
LC3D7: FDB 0454 ; 0.355 sec/gm, INJ FLOW RATE, DOUBLE FIRE
; cal = Sec/gm * (256 * 5)
;
; (1/0.355/sec/g) = 2.819 g/sec
; 2.819 g/sec * 3.6 = 10.150 kg/hr, (22.3#)
;----------------------------------
LC3D9: FDB 0908 ; 0.3547 sec/gm, INJ FLOW RATE, SINGLE FIRE
; ARG = (GMS/SEC * 256) * 5
;
; (1/0.355/sec/g) = 2.819 g/sec
; 2.819 g/sec * 3.6 = 10.150 kg/hr, (22.3#)
;----------------------------------

 

TB,

You're looking at injector flow rate not BPC. BPC is an inverse of injector flow rate relative to engine displacement.

BPC = Displacement(Litres)/#cylinders/Injector capacity(gms/sec)*1461.5

The BPC (base pulse constant) is a ratio of the engine displacement vs. the injector flow. The larger the displacement the larger the BPC. The larger the injector, the smaller the BPC.

Therefore, the larger the displacement of the motor with the same injector flow, the larger the BPC meaning that the injector size is smaller relative to the size of the motor.
I have an .xls to calculate BPC for you. If you're interested send me a pm.

 

To me this is the best advice, after you have done some reading what I would suggest is to start with small changes and basic things first to get a handle on the effect of changes being made.
Depending on your combo, it may be possible to bring it around through using the single and double fire @40, (inj. flow rate) and maf tables.

 

Update to my original situation (starting this thread) - went to Corey Henderson and got a dyno tune that included a wide band sensor. My NB O2 was and continues to be erroneous (will post that next), and it was setting inacurate BLMs. Set the closed loop temp constant high enough to keep it in open loop. Made adjustments to the fuel trim based on the wide band, and had to take out some spark because of the increased compression - results were 285 HP and 375 TQ. Will post the saga of my O2 issues separately.

 

BLM of 128 in a stock situation doesn't mean the car is operating at 14.7:1, usually richer. and 14.7 is a number GM came up with based on emmisions using cats etc.
I agree...
The 02 errors can more than likely be corrected through the tables (constants). When you have a motor with a cam change, this means more overlap. More overlap will mean that some fresh unbrunt intake charge (O2 and Fuel) is being dumped into the exhaust. The O2 sensor can register a lean condition even if you are on target. It is doing what it is suppose to be doing, registering the O2 content. The O2 sensor was designed to read the results of combustion and now it is reading the results of combustion along with fresh oxygen that is being pulled through due to the overlap
Since it will be measuring some of the unburnt charge, even if you are at 14.7:1at idle, the O2 sensor is going to see something leaner (even with a wideband). The INT. will raise and fuel will be added until the O2 sensor registers 14.7:1., the real AFR will probably then be less than 14.7:1.
The stoichiometric AFR does not control the BLMs., it controls the BPW. The O2 voltage swing points control the INT. (based on the predefined mV constants). It is when the INT. swings a particular amount that the BLM then changes. Decreasing the AFR and the initial BPW will increase, O2 voltage swings will increase. The INT will decrease in order to stay in line with those O2 constants. The BLM will decrease and the BPW will return to normal even though a lower AFR.