FTDI Serial Latency, and Threaded EEHack

I’ve found that lowering the latency on an FTDI serial device to 1 or 2 milliseconds gives improved performance for datalogging and other communications, at least at the 8192 baud rates we work with.


Give it a shot!

The next version of EEHack, which uses a threads, message queues, and switchboards instead of simple order-of-operations and timers, approaches 17 samples per second in ‘patched’ mode on several test systems with the reduced latency.. which is probably about the maximum you’ll ever see on this old ECM.

EEHack 4.1 Released

EEHack’s 4.1 release is now out!

For those of you running 4.0, hopefully the automatic version notification worked, and this notice won’t even be necessary…

Highlights include improvements to the graphing module, the knock analyzer module, and some minor tune-ups to flash write timing to decrease the chance that errors will occur.

This release is also important as I’ve changed the way font sizes are displayed.  Some users with modern high dpi displays with enlarged fonts found the program unusable.  This should help a lot.

See the full list of changes, or go download it!

EEHack 4.0 Released!

The new version of EEHack is (probably) stable enough to use!

Download it here!

It records, modifies, tunes, analyzes, graphs, and flashes your LT1 in almost every conceivable way to help you nail the perfect tune more quickly.

This thing is now a monster with many tens of thousands of lines of code, and exponentially more features than any LT1 datalogging utility on the market, for free.

I worked hard on this one.  Just a small sample of stuff I’ve done (there’s TONS more, see changelog and features & screenshots):

  • An appearance makeover
  • A proper windows installer with all new libraries included
  • Flash write improvements and enhancements, better recovery modes, will salvage a ‘bad flash’ most of the time!
  • Passive datalogging improving patch insertion enables AFR display and faster data rate
  • Tons and tons of bug fixes and performance improvements
  • Automatic transmission functions
  • New and improved analyzers
  • Presets for graph combos
  • Major wideband improvements
  • Display percentages and optionally round them off for easy readability
  • More actuators (fans, air, ac, etc)
  • Cylinder drop test should work well now
  • Graph CL/WOT enable/disable as a transparent overlay


This thing clobbers commercial LT1 dataloggers now, if you use the ‘donate’ button in the about tab and throw me a few bucks, I’d appreciate it a lot!



I’d like to take a moment and thank everyone that’s recently pitched in a few bucks to my paypal beer/carparts fund, and mostly from the gearhead-efi crew.  Some donations have been especially generous.

I know that none of us LT1 folks are rich, especially after dumping so much into keeping these beat up old sports cars running.  Every time I get an email that someone has thrown me a tip, big or small, it makes my day.

I’ve never really directly asked for anything for my time and efforts (…outside of putting a big ‘donate to beer fund’ button in the about tab of eehack, which will be in the next version…)

The timing has been really great, my wife has been out of work for some time now, so my car budget is shot, and my clutch throw-out bearing is starting to sound like it’s possessed by demons.  Now I can afford a proper replacement.

Your donations have really demonstrated to me that:

  • I did the right thing investing a lot of my free time into this project
  • Taking the high road with “Free and open source” is the right way to go
  • People actually do still tune LT1s!
  • People find the tools useful and appreciate it, instead of seeing them as just a novelty

Just a few more things to tidy up, and 4.0 should be released soon!

Comparsion of $EE Dataloggers


  • Free!
  • Logs all useful engine and transmission data
  • Reads and clears ABS and SIR codes
  • Records and exports log files
  • Test IAC, idle target, A/C, AIR, ABS, other actuator tests
  • Advanced electrical faults readout
  • Simple 4 channel data graph (Large)
  • Retrieves VIN, CAL ID, lots of other info
  • Supports 1993 LT1 engines too

TunerPro RT

  • Free! (With nag screen, and registration reccommended)
  • Some beginners find configuration difficult (but highly customizable)
  • Integrated data tracing and bin editing (hilight active cells in tuning tables)
  • Can potentially read/log/display ANY datastream element (depends on ADX)
  • Multiple graphing (requires manual configuration)
  • Customizable dashboard (requires manual configuration)
  • Running average history table analysis (no record filtering capability)
  • Can tweak ANY engine parameter available in the mode 4 message (like eehack), but only to fixed pre-defined values in ADX, and new commands clear all previous ones. Requires datasheets and manual configuration, so difficult to use for many practical purposes.
  • Wideband input no problem (requires raw configuration, knowledge of datastream, and some math)
  • .. It also edits bins!


  • Free!  (And open source) (beer money appreciated)
  • Highly portable, Windows version is well supported and tested but can run on Linux or MacOS with some work.  Source code available.
  • Displays and logs a huge variety of parameters, including some that can be patched in, such as Target AFR.  No ABS/SIR codes at this time.  “Fast” mode with increased acq rate available.
  • ‘Dashboard’ display for common parameters plus four user-defined parameters, as well as tabs with all data listed in table format, with optional ‘view level’ filters.
  • Real-time testing.  Temporarily skew timing advance in real-time for ‘by feel’ tuning or research, either manually or automatically with 3×3 map/rpm “AutoSpark” table. Temporarily set forced AFR target, arbitrary idle target or iac steps, closed loop, BLM learn, fans, auto trans geras, TCC, etc. in real time
  • Disable arbitrary injectors per-cylinder manually, or run an automated test that estimates cylinder balance.
  • Wideband O2 input two-point arbitrary configuration, presets, and optional smoothing, both using AC pressure and another unused pin.
  • Onboard notepad with limited parameter snapshotting
  • Full-time data recorder with optional log stacking. If you’re connected, you’re logging, all the time.
  • Proprietary log format for storing logs (stores extended data)  or CSV data output format.
  • Custom ‘raw’ command insertion with automatic checksum and length calculation, single-shot or loop mode
  • Two large synchronized anti-aliased graphs.  Can highlight graph areas with binary values such as closed loop enabled, wide open throttle, fan on, etc.
  • Very fast static parametric ‘one-click’ fuel and knock analyzer suite:
    • Global coolant or timestamp restrictions
    • Cellular BLM/INT trims or wideband REAL average in both VE MAP/RPM and MAF AFGS scope
    • Power enrichment analysis in rpm vs map
    • o2 performance analyzer
    • Seperate idle trim bank display
    • BLM population and range analysis
  • Reads and sets arbitrary VIN to any 17 digit string and CAL ID
  • Flash READ with or without RAM section
  • Flash WRITE with optional T/E side selection, bin compare feature with auto-save, 0xFF compression, aggressive failure recovery, and passive datalog-enhancing patch insertion
  • … More.

TTS Datamaster

  • Is now discontinued and unsupported
  • Retails for approx $120
  • Logs all useful engine data
  • Logs all useful transmission data
  • Custom RAW parameter definition, for widebands etc
  • Simple ‘running average’ BLM histogram analyzer
  • Clears DTC codes
  • Retrieves VIN number
  • Saves CSV logs (configurable)
  • Simple 4 channel data graph (Small)


  • Classic program works well on very old PCs, but no longer supported and has trouble on newer versions of windows…

Next EEHack Release?

What’s in store for the next release??

First off, since it’s now a flash tool, the next version will start transparently patching your bins as they’re programming for more/faster/better data to play with.  Since we’re the flash tool and the logger, we can slip in some code into the unused aldl modes and messages.  There is a bunch of unused aldl code that can be abused for more data.

These patches will be silent and safe, and have a persistently stored version byte (which can be fetched immediately on connection) so EEHack will tell you if your ECM version and EEHack version are out of sync, and enable enhanced features only with the correct patches installed.

First patch is an easy one, I have constructed a shorter message for speed logging which doubles the sample rate (if you don’t mind giving up error codes, a/c temperature, or anything else useless for actual tuning…)

A kind LT1 enthusiast is donating a wideband to me, which is a BIG deal since now I’m inspired a bit…

Tweaking the datastream opens up some possibilities, as does kur4o’s recent patch to enable memory dumps on the e-side just like the t-side already has.  With open loop AFR target in the datastream and higher sampler rate and direct access to the bin, this means the analyzer can compare open loop AFR target with actual wideband AFR at an increased resolution, giving you an accurately corrected VE table with no messing around or reflashing while you’re building it.  The existing tables themselves, if required, can be dumped from the bin without reading the whole thing…

Hell you can even force open loop without flashing, so the idea is, if you have a wideband and you feel your AFR is drifting out of whack, just click connect, force open loop, take a drive, and hit ‘analyze’ when you get home.

What about the flash tool?

Other than more stress testing and stabilization… It’s getting way faster data rates too, abusing the fact that EEProms erase to 0xFF (11111111) to decrease the serial bottleneck.  This means that 0xFF bytes don’t need to be transmitted for them to be programmed, they’re already in the correct state we just have to play with chunk sizes a bit to reduce write traffic in certain areas.

We can also blank out unused/unreachable sections of the bin, for example, automatic transmission tables in manual bins don’t matter, and MAF tables in VE only bins don’t matter either.  This is also transparent, and doesn’t involve modifying your bin as it’s stored on disk.  Could save thousands of bytes, and with our already existing single-sided write, we could be sitting around waiting for flashes a lot less…..

Stay tuned.

EEHack 3.5 – Flash Write & Wideband

New release of EEHack is ready.

Among other things, I think we can consider this the first release of my FREE LT1 flash tool!

I’ve put a lot of time into this flashing routine, and although I’d not officially recommend it to poor LT1 users that only have one car or one ECM yet (just in case a bug pops up) I think it’s ready for public use. Also, try reading a bin first, before writing your first bin!

About the Flash Routine

This flash tool has a ‘take any long shot to save your ecm’ philosophy to error recovery, which, on any unrecoverable error, tries its best to regain control, erase the chip again, and start over. It also tries to verify your serial connections integrity before even trying to do anything.

It also features single-sided flash, which will flash the e-side or t-side only if desired. It can also conveniently compare your old bin to your new one, to determine which parts need to be flashed. This potentially cuts flash time and risk in half if you’ve only made a small change or two!

This is a big deal to people tuning on a budget, as with a free copy of TunerPRO (Non-RT) and my EEX XDF file, you can have the most advanced tuning and analysis platform for your 94-95 LT1 for only the cost of an ALDL cable (I’m working on making that cheaper too….)

Not 100% sure on this, but perhaps now the 94-95 LT1 is the cheapest GM car to tune EVER!

Wideband Enhancements

This new EEHack release is also important to people with widebands. It has an additional analyzer feature to plot wideband readings in cruising range, a commonly requested feature.

Also has a brand new wideband input on a dedicated pin so you don’t have to use the a/c input hack anymore!


Let me know how it works out. As always, use at your own risk.


Full list of changes here.