94 LT1 massive re-program- Where to start?

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11-25-2019
Sleeperwagon

94 LT1 massive re-program- Where to start?

Apologies in advance for the long-winded post-

Well, I may have bitten off more than I can chew. I own a '94 Buick Estate Wagon, and have limited experience with the ECM. I have done some basic changes, ie EGR delete, rear end gearing and tire correction change, max speed fuel cutoff, etc. But then, I lost oil pressure at the drag strip. That led to a rebuild, which led to a stroker crank, which led to a huge cam, which led to a port nitrous kit, which led to a T-56 conversion, and on and on and on. It may be easier to list the parts that haven't changed. But here I am, with the engine back in, transmission installed, and almost ready to fire it up. EXCEPT, I am certain that it won't even come close to running with the tune that was in it when I parked it. I bought 4 books on EFI systems (Both books by Banish, one by Strader, and one by Cramer and Hoffman) and while I now have a fairly thorough understanding of how the systems work in general, there wasn't much specific on early OBD1 stuff. Here is a basic list of the things I have to account for. I'm sure I have forgotten a few and will need to update as I go-

displacement increased from 350 to 383
11.5:1 compression
ZZ409 cam
heavily ported iron heads
Long tube headers
port matched intake
1.6 roller rockers
44lb/hr Accel injectors
smog pump delete
EGR delete
OEM throttle body bored to 54mm
F-body MAF
Converted to dual electric fans
T-56 trans from 96 camaro
3.73 gears
3inch x-pipe to dual 2-1/2inch exhaust
Aftermarket coil and colder plugs, gapped .035 and electrodes rounded for nitrous

The nitrous system is essentially completely separate from the EFI:
direct port with 8 fuel/nitrous nozzles
Fuel is supplied by a separate electric pump at 7psi from a separate tank
Entire nitrous electrical system is separate. Fuel pressure, nitrous tank pressure and fuel supply safety interlocks incorporated to ensure nitrous supply is interrupted if fuel flow is compromised. Intention is to tune nitrous separately for essentially neutral burn, so any minor rich/lean conditions are within the range of ECM adjustment when nitrous is engaged.

Where to start? I know data-logging will be necessary to get a final tune, but the car has to run first. I have injector specs from Accel, I think I understand how to adjust cylinder volume, injector flow rate and offset. I will need to disable all settings relating to the auto trans. I intend to completely tune the car NA before I ever start messing with the nitrous system. Should I try to find a BIN from an f-body manual trans car that has been stroked as a starting point, or make massive changes to my existing BIN? I kinda feel a little overwhelmed and I'm scared to death of killing what has now become an extremely expensive engine before it's even broken in. Any advice is very much appreciated!

Tom
11-25-2019
steveo

i’d try to stick with the b body bin i think your bbody dash candy might misbehave otherwise. there are lots of bins on my site if you want to compare
unset the auto trans flag and if any dtcs show up deal with that after
copy the speedometer settings from an fbody 3.73 bin
input your new injector flow rate (and offsets if you have them)
copy the fbody maf tables
increase idle speed targets and add a bit of closed tps timing advance
you’ll probably have to enlarge the idle bypass hole in the throttle body
get eehack running and if it has trouble idling you can play around with timing and targets until you fund out what it wants
i’m sure it’ll run well enough to not blow up while you break it in and you can fine tune from there. you can get a maf table dialed in really quickly once you start logging.
11-25-2019
Sleeperwagon

Thank you sir! I have eehack on my laptop but haven't tried interfacing with the car yet. One thing I noticed on the Accel injector specs sheet VS what I see on tunercats is that the factory chart has a very wide range of voltages, but the new injectors tables only go from 8 to 16 volts. Since the new offsets are much higher (in some spots nearly double the OEM injectors), should I just estimate the extended ranges of the table, knowing the engine should never go there? I'm not sure if the car uses finite points from the table or if the computer uses a continuous curve. If it does and I only replace the 8-16v numbers, then it seems like as it approaches the ends of that range where the table has large shifts back to the factory numbers the curve would be quite inaccurate. Sorry for being uneducated on the actual computer processes at work here.
11-25-2019
Sleeperwagon

Also, you mention having BINs on your website. I'm starting to make the connection that you are the guy who wrote eehack? What website am I looking for? Thanks!
11-25-2019
steveo

yeah that’s me

see fbodytech.com bins > factory calibrations

if you post your injector data i can generate a spline and get you a proper lt1 table since the points are almost certainly different

its fine to just guess for values outside 10-15 volts or so as it will run like crap with low voltage no matter what
11-25-2019
Sleeperwagon

https://documents.holley.com/accel_i...ons_150144.pdf

This is the spec sheet for the injectors I am using
11-27-2019
Sleeperwagon

Got all the program mods done as suggested other than the offsets. I can possibly approximate the spline using Mastercam (I run a CNC machine shop) and get the numbers I need. One other quick question though- I have seen a few people mention the possibility of bricking the PCM when using eehack to actually re-flash the bin into the car. I still have tunercats from when I was playing with the car before the engine build saga, and used it for all previous bin modifications. Is it safer to just use it for the flash, and then switch to eehack for the datalogging part? I failed to mention that I installed a wideband o2 sensor with an LC-1 controller before the car was parked, but never got around to wiring it through the A/C pin for data logging. Is there a more elegant way to incorporate the wideband that has cropped up in the 5 years the cart has been collecting dust?

Thanks!
11-27-2019
NomakeWan

In my experience, it depends on how well EEHack communicates with your particular vehicle. I have two Corvettes. On one, I get constant communication errors (which EEHack discards from the logs properly), so it is not safe to flash using EEHack. I have gotten away with flashing using TunerCats's flash tool and have been perfectly fine, because it has an incredibly aggressive checksum/retry algorithm in place. On my other Corvette I don't get any communication errors, just random momentary disconnects during long logging sessions which may be related to vibration or other physical disturbances. Sitting in my driveway or a parking garage I've had zero issues flashing with EEHack, and love it since EEHack takes only 40 seconds to flash, compared to over 3 minutes with TunerCat.

steveo is shooting for a new flash routine and possibly even an "unbrickable" flash system for version 5.0 for 2020, so there's that too. Basically, in my personal opinion, I would just connect using EEHack, see if you get random comm error increments while the car is sitting, and then use EEHack to read your BIN. If you don't get random errors and the program successfully downloads your BIN without issue, then I'd say it's perfectly safe to flash.
11-27-2019
steveo

Quote:

Originally Posted by Sleeperwagon

Got all the program mods done as suggested other than the offsets. I can possibly approximate the spline using Mastercam (I run a CNC machine shop) and get the numbers I need. One other quick question though- I have seen a few people mention the possibility of bricking the PCM when using eehack to actually re-flash the bin into the car. I still have tunercats from when I was playing with the car before the engine build saga, and used it for all previous bin modifications. Is it safer to just use it for the flash, and then switch to eehack for the datalogging part?
Thanks!

tunercat has bricked a few ecms for me and so has eehack. it's always a risk. the rate of failure is LOW. if you run a few flash READS first and they're successful, go ahead and take the plunge.

during a flash, we basically load the ecm with a special program loop in RAM (super temporary) and transfer execution there, then erase the EEPROM completely, and we slowly load your new program into the EEPROM. if that fails somehow, the ECM will no longer reboot successfully, so there's no way to start over. eehack tries its best to re-erase and start over. tunercat/winflash does a good job of retrying individual packets but doesn't do well with the 're-erase and start over' thing. both programs can fail and you are buying a new ecm or soldering sockets in your old one.

tunercats is good software and if you want to flash with it, go for it. it was professionally written and i just muddled through it with my flash routine.

i think you'll be fine with eehack's flashing though, not a lot of people have trouble with it. it's definitely got some more advanced features and flashes WAY more quickly but it's possible that tunercat has a better success rate...? i don't know, some people have told me the opposite. nomakewan's car is an oddball case and does not apply to most

as mentioned i plan to improve the flash routine in the next release and i know exactly how to make this procedure better, but consider i live in the bush and drive a jacked up jeep with an AMC straight 6 engine now so none of this actually helps me anymore... might be a while.

Quote:

I failed to mention that I installed a wideband o2 sensor with an LC-1 controller before the car was parked, but never got around to wiring it through the A/C pin for data logging. Is there a more elegant way to incorporate the wideband that has cropped up in the 5 years the cart has been collecting dust?

yep way ahead of you there. use D27 (pin 27 on the blue connector).

on some b-bodies apparently it runs to an EGR position sensor that never actually gets used for anything but logging so just cut that thing off if it's already wired. eehack supports D27 AND the a/c wire in both the stock datastream and its custom speed logging stream, but i'd recommend D27.

i think you'll really like eehack for this stuff. i've tried to think of everything the tuner will need and it's built just for the lt1.
11-27-2019
Sleeperwagon

Thanks so much! I hope I wasn't coming across as bashing on your program. I have mad respect for your abilities and I know just enough about programming from writing CNC code to be completely confident that eehack is far beyond anything I could accomplish in a hundred years. I'm just super paranoid because in all my years of junkyard scrounging I have only come up with 2 spare ECMs. The stupid cash for clunkers program pretty much led to every one of these cars within 200 miles of me going to the crusher. I will be sure to check all my chassis and engine grounds and make sure the laptop and car battery are fully charged before I try to re-flash. My daily driver is a Cherokee 4.0l so I know what you mean about getting to things when you can on hobbies. My LT1 has been parked since 2015...