Step away from that lap top Bill. Some programming advice.

Okay, going to try some of this new fangled computer stuff.

Just recieved an interface cable (thanks Nick) so now my laptop can speak LT1. Have datalogged a couple of runs and have played around with line pressure. Suprising enough I haven't blown up the ECM, or for that matter the tranny yet. So with my new found expertise (or luck) I am now ready to attack some tuning tweaks but I have a few questions:

According to an article I downloaded a couple of months ago, to achieve max mileage, you want the LTFT (long term fuel trim) as close as possible to 128 in all fuel cells at part throttle. The article also suggests changing the air flow/MAF frequency to raise or lower the LTFT. My first question is, what is the relationship between long term and short term fuel trim?

After cleaning the MAF and the throttle body (the EGR is next tomorrow) my short term is dead on at 60 MPH, fluctuating between 124 and 132, while my long term is 108 to 112. My air intake is steady at 24 to 28 grams/sec. (4th and 3rd gear). Are the short term counts just the reflection of a base line established by the long term counts or are they showing the true fuel air mixture?

My second question is about the physical operation of the MAF. Based on my observation of this thing, it looks as if the ECM is reading the resistance of the three resistors, using the intake air temp as a baseline, and extropolating the air flow by how much the air cools the resistors. Am I correct in this assumption? If so then why is the reference given in the programming tables comparing frequency to air flow in grams per second? If not, then how does this thing work?

Am really a newbie with this stuff so any help would be appreciated.

Bill

First off, I's suggest there are a few better forums for this question. There are likely few here who've done much programming. I see you've also posted at:
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Find more forums that deal with LT1 reprogramming. I'm not sure if [You must be registered and logged in to see this link.] will be of benefit., but I'd check it out there as well. In answer to your question, from my limited knowledge, YES, you are trying to get BLM cells to approximately 128, but unless you have turned off certain functions you'll be chasing your tail forever.

WHY?

Two reasons that come to mind are Highway Mode and Idle Mode. Both are designed to go lean intentionally under specific conditions. The easiest way to turn off Highway Mode is to set the speed parameter to a ridiculously high point such as 200mph. It will never engage, you can tune your cells without interference. Once you are happy with the changes you've made reset Highway Mode again, If it was set at 50mph you could consider knocking it down a few more points to 45-48 mph so it engages sooner on your travels at a lower rpm and saves a bit more gas during your day There is a similar way to disrupt idle as well, one way involves changing the ideal microvolt level of the O2 sensors that that the ECM will accept as Stoich, but I haven't bothered to mess with it yet. I got mine to idle nicely by pulling gas from tables that don't exist in a MAF system, so I m not going to screw with it's O2 sensor. (yet)

I worked in a different ECM mask than you. I use speed density on a 730ECM from '92 Corvettes Camaro's and Firebirds, so hopefully this is of some value to you, Dave.

Thanks for the input Dave. As I suspected, its obviously not just tweaking here and there. The MAF tables just seemed to me to be the most direct route to where I want to go. Going to have to investigate the hierarchy of the program (what effects what etc.) before I dig into this further.

Diesels are not nearly as dependent on maintaining a close AF ratio. Lean it out and it either slows down or stops, richen it up and it goes faster till it runs out of air then it blows black smoke and the EGTs go off the map.

Much more research is needed. By the way, [You must be registered and logged in to see this link.] just defaults to one of the many product specific search engines. Is there a back door into this site?

Bill

thirdgen.org is what you are looking for

I apologize for the wrong site link. It should be: [You must be registered and logged in to see this link.]org.

I am in error saying ".com"

In particular if you find out the specific part number of your ECM is. You'll better able to match up with the specific "mask" and ".bin" that will help narrow your research. Don't be too surprised if you need to end go to a GM diesel pickemup truck site for your knowledge base. I have no idea if the LTI was ever the basis of a Stock GM Diesel engine. If so, that particular make and model forum would be where I'd go to cash in on answers.

lakeffect wrote:

In particular if you find out the specific part number of your ECM is. You'll better able to match up with the specific "mask" and ".bin" that will help narrow your research. Don't be too surprised if you need to end go to a GM diesel pickemup truck site for your knowledge base. I have no idea if the LTI was ever the basis of a Stock GM Diesel engine. If so, that particular make and model forum would be where I'd go to cash in on answers.

I too have to apologise. My reference to diesels was just that a reference. I am working on the LT1 in my Cadillac, no diesel yet. Been many years (20 yrs +) since I fooled around with gassers and even then with non-computer controlled versions, mostly big block Pontiacs and aircraft engines. Been more involved (some say obsessed) with diesels since the early 80s. This is the first true computerised gasser I have ever looked at closely.

If I can get the normal highway mileage up to the 28-30 MPG (IMP) mark plus input a tune that will allow me to pull my 26ft. RV without significantly impacting the stock prices of the oil companies, then it won't justify me doing the diesel conversion for now. I know I can achieve 40 MPG with the diesel but would have to put on a ton of miles to make it feasible if the gasser will get me anything over 25 MPG.

Bill

...waiting patiently in line for a Diesel Bill economy tune for my wagon...

thanks for clarifyingt the diesel stuff.

There should be much correlated info at the [You must be registered and logged in to see this link.] site, as well as the Impalasforum where many have done the programming stuff ahead of you.

It's incredible as to how much of a knowledge base you can tap into out there. One issue is ALWAYS learn to use the "search" function first. Some sites will tear your hide off since it's the 1000th time a question has been answered.

It will be great when the old info is restored on the ISSF. Not much to search there these days. Apparently the data from before the forum switch to VBulletin has been located (pre 2008) and will be reinstated during a hosting change. Data from 2008 to last summer will be lost forever, but the old stuff is a gold mine...

When I first got started, I found a good basic tutorial at:

[You must be registered and logged in to see this link.]

A good overview but I was looking more for the principals of how the thing was programmed, what it was looking for and how it converted that information into a useful format. My problem with most search functions is that typically, the topics covered assume you have the go pedal welded to the floor. My interest is elsewhere. Found the proliferation of the term WOT rather annoying during my search before posting this thread.

My preference is always to gain enough knowledge before I start, then to use the trial and break method. It has to make sense to me before I'm willing to dive in.

Thanks again

Bill

pcm is an 8051.

nick

anacronyms I've seen listed

A/C Air Conditioning
A/D Analog to Digital ( sometimes ADC)
ABS Anti-Lock Brake System
ADC Analog to Digital Converter
AE Acceleration Enrichment
Aero Aerodynamic(s)
AFCO All Fuel Cut Off
AFPR Adjustable FPR
AFR Air Fuel Ration
ALDL Assembly Line Diagnostic Link
ALPHA-N Form of EFI
BBC Big Block Chevy
BDC Bottom Dead Center
BIN Binary
BLM Block Learn Multiplier
BP Barometric Pressure
BPC base pulse constant
BPW Base Pulse Width
CAFÉ Corporate Average Fuel Economy
CAN Controller Area Network
CARB Carburetor. (Also California Air Resources Board)
CAT Catalytic Converter
CC Combustion Chamber
CCC Computer Controlled CARB
CDI Capacitive Discharge Ignition
CE Check Engine
CFI CrossFire Injection
CL Closed Loop
CNP Coil Near Plug
CPU Central Processing Unit
CTS Coolant Temp Sensor
DAC Digital Analog Converter
DC Duty Cycle
DE Deceleration Enleanment
DFCO Deceleration Fuel Cut-Off
DIY Do It Yourself
ECM Engine Control Module
ECT Engine Coolant Temperature
ECU Electronic Control Unit
EEPROM Electronically EPROM
EFI Electronic Fuel Injection
EGO Exhaust Gas Oxygen
EGR Exhaust Gas Recirculation
EGT Exhaust Gas Temperature
EPROM Erasable PROM
ESC Electronic Spark Control
EST Electronic Spark Timing
F/A or A/F Fuel-Air Ratio
FEEPROM Flash EEPROM
FP Fuel Pump
FPR Fuel Pressure Regulator
GM General Motors
GN Grand National
HEGO Heated EGO
HEI Heigh Energy Ignition
HW HighWay
IAC Idle Air Control or Intake Air Control
IAT Intake Air Temp
IC Injector Constant
INT Integrator
KS Knock Sensor
Lean AFR greater than Stoich
LT Long Tubes
LTC Long Term Correction
MAF Mass Air Flow
MAP Manifold Absolute Pressure
MAT Manifold Air Temperature
MIL Malfunction Indicator Lamp
MPFI MultiPort Fuel Injection
NB Narrow Band
NETRES Network of Resistors
O2 Oxygen
OBD-I On-Board Diagnostics pre-95
OBD-II On-Board Diagnostics post-95 pre CAN
OEM Original Equipment Manufacturer
OL Open Loop
PA3 Peripheral Address # but with GM it's the Knock Counter
PCM Powertrain Control Module
PE Power Enrichment
PFI Port Fuel Injection
PIC Programmable Integrated Circuit
PROM Programmable ROM
PW Pulse Width
PWM Pulse Width Modulated
RESNET Resistor Network
Rich AFR less than Stoich
ROM Read Only Memory
SA Spark Advance
SAE Society of Automotive Engineers
SBC Small Block Chevy
SD Speed Density
SES Service Engine Soon
SFI Sequential multiport Fuel Injection
STC Short Term Correction
Stoich Stoichiometry
TBI Throttle Body Injection
TCC Torque Converter Clutch
TDC Top Dead Center
atdc = after top dead center
btdc = before top dead center
TF = throttle follower
TGO ThirdGen.Org
TPI Tuned Port Intake
TSA total spark advance
TPS Throttle Position Sensor
VAFPR Vacuum referenced ADFP
VATS = vehicle anti-theft system
VE Volumetric Efficiency
VS Vehicle Speed
VSS Vehicle Speed Sensor
WB Wide Band
WOT Wide Open Throttle



mse c = milli second .001 seconds
usec = micro second .000001 seconds
nsec = nano second .000000001 seconds
pph = pounds per hour
gps = grams per second
bsfc = brake specific fuel consumption
mvdc = milli volts dc

Good list. Maybe we should think about making it a sticky.

Bill

time to step up, leave the old 8051 stuff alone,. add the better reluctor wheel,. the coil on plug setup and use the ls2 pcm, way more involved, and you can force any program you want on it,
Wasn't you that always said "i don't want a computer controlling my engine?"
switch the intake out, add a distributor, and a carb, and you,re good to go,..

Nick

phantom 309 wrote:

time to step up, leave the old 8051 stuff alone,. add the better reluctor wheel,. the coil on plug setup and use the ls2 pcm, way more involved, and you can force any program you want on it,
Wasn't you that always said "i don't want a computer controlling my engine?"
switch the intake out, add a distributor, and a carb, and you,re good to go,..

Nick

Still convinced they are not needed on diesels, though the stuff they are getting away with on the common rail set-ups is starting to look interesting. Still contend that the same things can be accomplished without getting Bill Gates involved. The stuff doesn't intimidate me, its just that all the little gizmos and sensors that the computer depends on to make the right decision are all working in a terrible environment (freezing temps, in the exhaust stream, on or beside a hot engine block or covered in oil and grease.

From what I have seen over the past 20 years, most of what we have had to pay for is a result of lazy design engineers and regulators that have forced the manufacturers to invent increasingly smaller chisels to split smaller and smaller atoms. Not to say there hasn't been an up side but just figured that I should get my head out of the 80s and learn something new. Never know what might crop up as a result.

Bill

Quote :

... just figured that I should get my head out of the 80s and learn something new. Never know what might crop up as a result.

Bill

80's..... hey... ya never know when disco might come back!

[quote="lakeffect 80's..... hey... ya never know when disco might come back![/quote]

Don't look now but I think its back

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Bill

[You must be registered and logged in to see this image.]



....but then again , it's only one disco cat's opinion.

Okay a little update. I have been trying to absorb what Kevin and Scott are discussing over on the same thread on the ISSF board, and what the two guys are saying makes some sense. However, I do think they are assuming I have more experience then I actually have when it comes to programming.

Up to now I have been addressing the basics and just finished cleaning up the EGR (it was hanging up). I re-loaded the original program and logged another 20 mile run, mixed driving country roads and highway. From what I have read, when you load a program, disconnect the battery or pull the ECM fuse, the LT and the ST reset to 128.

Started the log before starting the engine and the open loop idle fuel cell (16) LTFT immediately showed 120. By the end of the run all the cells were in the 108-112 range. In other words, its getting worse . This is getting a tad frustrating. Seems the more basic stuff I do, the more it resists my attempts to getting it running right.

Starting to look like the gentle rattle of a diesel under the hood would fix all my problems .

Taking the car on an extended trip (600 miles) on Thursday and we will see if things correct themselves.

Bill

convert2diesel wrote:

After cleaning the MAF and the throttle body (the EGR is next tomorrow) my short term is dead on at 60 MPH, fluctuating between 124 and 132, while my long term is 108 to 112.

convert2diesel wrote:

By the end of the run all the cells were in the 108-112 range. In other words, its getting worse . This is getting a tad frustrating. Seems the more basic stuff I do, the more it resists my attempts to getting it running right.
Bill

seems its the same,.
NO more diesel quips ok? IT IS NOT a diesel.
your airfilter clean? fuel pressure good? egr pipe not plugged up, intake not leaking,.

Nick

phantom 309 wrote:

convert2diesel wrote:

After cleaning the MAF and the throttle body (the EGR is next tomorrow) my short term is dead on at 60 MPH, fluctuating between 124 and 132, while my long term is 108 to 112.

convert2diesel wrote:

By the end of the run all the cells were in the 108-112 range. In other words, its getting worse . This is getting a tad frustrating. Seems the more basic stuff I do, the more it resists my attempts to getting it running right.
Bill

seems its the same,.
NO more diesel quips ok? IT IS NOT a diesel.
your airfilter clean? fuel pressure good? egr pipe not plugged up, intake not leaking,.

Nick

Air filter new, new fuel pump (will rig something up tomorrow to check pressure), egr pipe may be a problem but the rest of the exhaust passages are clean, intake checked with both propane and water and now visible leaks. Manifold vacuum steady at 20.5 at idle.

Bill

A tad off-topic but saw an interesting (disturbing) article that sort of underlines my concerns about computers and automobiles:

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The Canadian Press

Date: Tuesday Apr. 13, 2010 7:45 PM ET

TORONTO — Increasingly complicated vehicle software is making it "well-nigh impossible" to duplicate in testing all the real-world situations a driver could face, according to one expert.

"There is actually a serious problem in both identifying all the possible situations that can occur and simulating those situations so you can test to see whether the software actually worked correctly or not," said Tom Maibaum, principal investigator for the Centre for Safety-Critical Software Certification at McMaster University in Hamilton.

"It may actually be well-nigh impossible to duplicate some of the situations which may occur."

The average new vehicle today has approximately 100 different computers using close to 100 million lines of code, all of which are constantly communicating with each other and with hundreds of sensors, Maibaum said.

By comparison, the safety system at Ontario's Darlington nuclear plant uses one computer with 60,000 lines of code.

On Tuesday, Consumer Reports gave the Lexus GX 460 sport utility vehicle a rare "Don't Buy" warning due to the potential of rollovers. The magazine said the rear end of the SUV slid until it was nearly sideways before a stability system kicked in during a test of how it handled unusual turns.

In Canada, Lexus is the subject of a lawsuit by a Toronto woman who says software problems with the automatic transmission of her ES330 caused her to lose control of her vehicle and drive it into a tree.

Toyota acknowledged problems with the automatic transmissions in its Camry, Sienna, Highlander and Lexus ES vehicles and said it was seeing numerous customer complaints as early as 2004, according to documents filed in the Ontario Superior Court.

Maibaum said "a very simple problem" -- the complicated software -- is at the heart of problems like those faced by Toyota.

When dozens of computers are used simultaneously, they have to be prepared to deal with a dizzying array of complicated real-world situations, he said.

Unfortunately, the software is often designed cheaply and quickly by engineers who don't necessarily have the right education and experience, and badly designed software can make fixing a problem that much harder.

"It makes it much more difficult to know whether you're fixing the right thing or whether in fixing the right thing, because the software is not well designed, you may actually be affecting other parts of the software," Maibaum said.

The only way to overcome these problems is by spending the money and taking the time to properly design and test all the software that goes into a vehicle, Maibaum said.
Bill