Tag Archives: ecotec ecm

ECOTEC ECM Tuning – Changes So Far

I mentioned in the last post I’d go into more details about HPTuners.  This time I want to talk about the Ecotec ECM tuning changes done so far.  I’m far from being an expert however one needs to start somewhere…

Vehicle Anti Theft System (VATS)

The first and most important task is disabling VATS.  This is a prerequisite when doing an engine swap such as what we did here.  Failing to disable VATS renders the engine inoperable.  On earlier ECM’s GM devised a system by which the ignition key had a special resistor that would match a receiver in the ignition key tumbler.  This “match” would enable the ECM to fire the engine.  With those early ECM’s it was possible to wire an inline module and basically fake out the key resistor.  With modern ECM’s such as the one controlling the Ecotec, the VATS became more advanced.  With the aid of HPTuners though, this is a simple change in the flash file burned into the ECM.

Mass Airflow Recalibration

In bowtie6, we replaced the stock plastic intake with a smaller, more direct intake manifold.  The reason was not for performance but because the stock intake was too big and got in the way of the steering shaft.  The air filter housing was also replaced with a cone-shaped K&N air filter.  There is simply no room under the hood of the TR6 for the large box that holds the stock air filter.  These changes forced relocation of the Mass Airflow (MAF) sensor.  As expected, the stock settings for the MAF did not match the new configuration.  This manifested itself in a rather rough idle and poor performance.

Tuning the MAF took some doing.  I won’t go into all the details but suffice to say it took a few hours worth of driving down the road and logging data with the VCM Scanner.  Using the VCM Editor I was able to dial in the low and high MAF tables to more desirable values.  This resulted in smoother idle and better performance.

Seeking Professional Advice

This is where the tuning process gets a bit pricey.  After going through several  books and reading many long hours’ worth of posts I decided to find a local expert.  Sure enough I found a person with a great knowledge and familiarity with HPTuners and tuning GM engines. However this came at a price.  The results though, made a huge difference.

As expected, fuel efficiency is the ahead of pure performance in the  stock ECM.  This shows up the way the commanded air fuel ratios are pre-set across the RPM range, spark tables and the way that power enrichment activates proportional to throttle angle – among other things.  After quite a few alterations the ECM is delivering more performance at the expense of fuel efficiency.  The results are astounding:  throttle response is much more livelier resulting in more power being delivered and overall the engine is much smoother across the entire rev range.  It is now very easy to make the Ecotec reach its 7000 RPM redline.

What next?

The next step will be to take bowtie6 to a dyno.  Been there, done that before but this time we will be tweaking the ECM  This will allow even more accurate dialing in for extracting that last bit of power.  Also, something that is yet to be modified are the VVT tables.  The 2.4 Ecotec has variable valve timing and this first tuning did not touch VVT.  Who knows what we can do with this?

Another avenue left for exploration is E85 Ethanol.  I’ve been intrigued for a long time about this source of fuel.  FlexFuel vehicles have a special metering device that allows the ECM to calibrate itself on the fly.  I don’t have that metering device but I have HPTuners and this will allow a special E85 calibration flashed into the ECM.  Where I live E85 is very easy to find – there is a very large fuel station just down the street from my house – so this will be a fun experiment.  Granted, flashing the ECM to run E85 without a metering device means E85 has to be burned exclusively.  However, changing back to straight fuel is easy to do, simply by reflashing the ECM.

In Summary

I realize to each his own and this is not for everybody.  However, having all this technology at your fingertips (literally) is remarkable.  Why would anyone want to waste time on those relics of fuel metering called carburetors is beyond me.

Stay tuned…  Soon bowtie6 will be the first E85 Ethanol powered TR6…  🙂

ECOTEC ECM Tuning – Intro

Gone are the days of “burning a chip” for engine computers.  Modern Engine Control Modules (ECM’s) can now be monitored real-time and then modified based on readings done after driving down the road.  Pretty cool stuff indeed but it adds a whole new dimension to engine performance adjustments.

The factory install of the Ecotec in a Pontiac Solstice at its core consists of the engine, wiring harness, ECM and the Body Control Module (BCM).  The ECM reads and controls engine signals while the BCM controls such things as gauges, door locks, lights, etc.  In addition, the BCM supplies data used in the information center on the instrument panel showing fuel consumption, engine temp, outside temp, etc.  Furthermore, the ECM and BCM talk to each other via a digital high-speed bus integrated into the factory wiring harness.

So, one of the challenges in getting the Ecotec to run in bowtie6 was making all this work outside of the factory install.  After doing a ton of research and reading the Factory Service Manuals, we were able to figure out what wires actually control engine sensors and what goes to the BCM.  This enabled us to change the factory harness to fit our needs.  Since we did not run the factory instrument panel and did not need to control lights and such, we did not use the BCM.

A disadvantage of this approach is the lack of cruise control.  In the Ecotec the throttle body is electronically activated – there is no cable in the traditional sense.  Instead, the electronic “gas pedal” inside the car sends a signal to the ECM via a small wiring harness.  This gets accomplished by coarse and fine potentiometer readings of the throttle pedal position (Click here for my Drive by Wire article).  There is also no Idle Air Control (IAC); instead idle is now controlled by the ECM cracking the butterfly angle as needed.  This is very amazing stuff.  As a side note, it is interesting to pay close attention when turning the ignition to the “on” position:  there is a very short “click” heard from under the hood.  It is the throttle body going through its pre-check.  But I digress… Bottom line:  my goal is to be able to integrate the BCM into bowtie6‘s wiring and by doing so, have a fully operational fly-by-wire cruise control.

Among the wires going to and from the ECM is a group that end up in a special plug called an ALDL connector.  This special connector is normally found in production GM cars under the dash on the driver’s side.  It is by the ALDL that the GM TECII scanner/programmer gets connected to the car’s ECM.  In my case I use my laptop along with an interface made by HPTuners to read and change the ECM’s settings.

Enter HPTuners

HPTuners is a commercially available ECM tuning package.  It consists of a Windows-based software running on a laptop and an interface with a USB connector on one side and a matching ALDL connector on the other.  This software package is quite remarkable in what it does; equally remarkable is the lack of documentation.  Sure it has online help but it is very lacking in detail and content.  In the hands of a newbie it can spell disaster to the engine; in the hands of an expert it makes an already great engine even more remarkable.

HPTuners has two main software components:  the VCM Scanner and VCM Editor.  The Scanner is the means by which the engine’s parameters get monitored real-time.  There are a number of different ways to display data:  charts, a gauge panel and tables.  Scanning is accomplished by connecting the laptop to the ALDL connector via the interface, starting the engine and pressing the “Scan” button on the Scanner.  Then you drive down the road and start logging data – the more, the better.  This data can then be saved to a log file for further analysis.  Another feature of the Scanner is to load a log file and play it back – this is very helpful in determining what to change.

The tool used to re-flash the ECM is the VCM Editor.  The process is quite simple:  read the ECM, make adjustments and re-flash.  The hard part though, is figuring out what to change and in what order.  It has been my experience so far this is a bit of a black science.  Information on the interweb is vast about tuning.  However, discerning truth from fiction is the true challenge.  There are several books on the subject and then there are tuning courses available, however they are pricey.  HPTuners is the tool but what to do with and how to use it, is a very time-consuming task!

In the next installment I’ll go into more details about HPTuners…

bowtie6‘s Custom Wiring – Under the Hood

After nearly 1,000 miles on bowtie6 since the ECOTEC conversion, I have a ton of stuff to detail out.  This is where you spend tons of time for little to show for.  Sure, I could just leave it “as is”, but there is no fun in that.  Sweating the details is what sets my car apart from all others.

Today, I spent some hours refining things in the main fuse box under the hood.  I’m not 100% done with it yet, but I figured I’d take a few pictures of it so far and write about it.  Maybe somebody might get some inspiration from all this work.

This is what the main engine-compartment fuse box looks like…

Big deal, huh?  Well the silver box is located in the area where the windshield washer bottle used to be and also the area where the dealer-installed air conditioning system was installed.  What is so special about this?  Well other than the fact this is all hand-made aluminium, take a look at what is inside the box…

Now it gets interesting…

  • Starting at the bottom of the picture are six circuit breakers.  Today, I added the little red “booties” to prevent any short circuits.  The middle breaker shows what they look like under the red “bootie”.  Two terminals stick out and this is what the “booties” protect.  Don’t want any electrical short circuits to happen here!
  • Above the circuit breakers are seven relays.  They control the most important basic functions underneath the hood.
  • Above that towards the right is a fuse panel with 8 modern spade type fuses.  These are used on the control side of the relays.  Basically they make the electromagnets in the relays trip when a switch makes ground.
  • The finned box with the three big connectors is the Engine Control Module (ECM) running the show on the ECOTEC.  This is “factory” supplied from the donor engine.
  • To the left of the ECM is the solid state electric fan controller.

Circuit Breakers

These guys act as fuses.  They feed the hard voltage from the B+ terminal through the firewall to the relays.  What B+ terminal?  Since the battery is located in the trunk, we ran a welding-machine cable from the battery’s B+ terminal through the firewall by means of an insulated bolt.  This is where we get voltage to the underhood fuse box and also to the inside of the cab (on the inside side of the bolt)

This is a close up of what this all looks like:

At the very left you see the post where full B+ voltage is supplied to the circuit breakers.  The body and frame is ground so how does this keep from shorting out?  The bolt is fully enclosed in a phenolic ring thus insulating the terminal.  On one side of the circuit breakers is the hot B+ terminal – this is the one nearest to the camera.  On the other terminal is the supply of power to the relays shown above.  On the middle of each circuit breaker you can see the little black dot that acts as a “reset” button.  I used circuit breakers because these are 100% essential to the electrical operation of the system.  If they trip a simple push of the black “reset” button has me back in business.


Seven relays run the show for the main switched hot lead, ECM, headlights switch, high/low beam, electric fan, horn, starter and ignition switch.  All the switches on bowtie6 break ground.  There is no hard voltage going through any switches.  The advantage of this is longevity.

So basically when a switch is activated, it “makes” ground.  This in turn causes the electromagnet in the relay to trip and that makes the circuit hot.  There is no hard voltage through any switch except for one:  ignition.  I am using an industrial strength switch for this, rated for much higher amperage than what the Optima battery delivers.  This will last past my lifetime.


There are 8 fuses under the hood.  These supply power to the control side of the relays as well as to the ECM and the electric fan controller.  I used modern style fuse housings and bladed fuses.  Glass fuses are just too poorly made and prone to failure and that makes them very unreliable.  Not acceptable for bowtie6.

ECM and Engine Harness

The “brains” controlling the ECOTEC is the GM factory E67 ECM.  The wiring from the ECM to the multitude of sensors on the ECOTEC is basically a factory harness from a Chevy HHR, modified to act as a Pontiac Solstice.  We modified the harness by changing pin-outs and removing unnecessary circuits.  This makes the harness much simpler to work with.  Furthermore we cut many wires to make them shorter or longer depending on where they were located.  This is the beauty of doing it “yourself” as opposed to buying something.  Anybody can “buy” stuff…  It takes talent to make you own.

Like I said before, the harness came from an HHR.  GM went through a lot of work in making a very durable and well engineered harness.  In my opinion, the quality of the wire is superb and the connectors are not only expensive but of very high quality.  The harness is basically divided into three “plugs” (you can see them in the picture above).  One has 56 pins; the other two have 73 pins.  Not all are needed though and having a Factory Service Manual will be instrumental in determining what circuits are kept and which need to go.

To make the ECM work outside of the “factory” setup, one must remove the VATS.  This is the “Vehicle Anti-Theft System”.  You do this either sending the ECM out to somebody or by using a software package such as HP Tuners.  We used HP Tuners.  This also enabled us to tune the ECM.

Speaking of the ECM:  make sure you get the right one.  The ECM’s come in two varieties depending upon the type of gearbox used.  An automatic gearbox ECM will not work on a 5 speed gearbox.  Also, there are certain E67’s that will just won’t work.  You will need to make sure you get the one with the right OS, otherwise it won’t work.  This is why it is very important to get the ECM that came from the donor vehicle.

Solid State Fan Controller

This little device is trick.  It has a built in relay and has B+, ground and a wire hooked up to the temp sensor on the block.  This is where the device gets its temp signal.  Here is the beauty of this device:  on 99.99% of all street rods I see, folks stick a nasty looking probe in the middle of the radiator core.  This not only looks awful but eventually wears a spot in the radiator’s core causing it to leak.  I think this way to wire a controller not only looks crappy as hell but is very sloppy.  The controller we use is not cheap, but it has a fully adjustable rotary knob that enables setting the proper temp to kick the fan on.   In the photo above the controller sits on top of the ECM but I am planning to move it to a different location to make it look a little more elegant.  Again, it is the details that count!

In Summary

I realize this is not everybody’s cup of tea (a polite way of saying “I don’t like it”) but once again this works for me and the car has been built to suit me not anyone else.  I wired the thing, I know each circuit and quite frankly I am proud to say it is bullet proof.  I blew a fuse one time, but that was my dumbass-self making a mistake.  Again, one can source a ready made wiring harness but what do you learn by doing that?  I spent a lot of time learning about circuits and how relays, fuses and circuit breakers work.  This takes time but the result is very rewarding.

If you do decide to undertake something like this, there are a few things I would highly recommend:

  • Every single terminal (and there are many) is soldered – nothing just crimped.  This is extremely time consuming but worth every moment you spend on it.  Soldering ensures a perfect connection and if you are going to spend this much time, you want it to be dead-nuts-accurate.
  • I used the expensive shrink wrap that has the sticky stuff inside of it on every joint, every terminal and every splice.  Why?  This makes the connection water and moisture proof.
  • Anytime I had to join parts of the harness, I used Weather Pack connectors.  They are not cheap, take a long time to crimp and assemble but they are water and moisture proof and last forever.  This is the only way to go.  By doing the harness this way you can ensure certain parts can be take apart without removing the whole shebang.  There is a bit of strategy to play here but you will be very happy with the result.
  • I spent quite a bit of resources on only the best quality wire.  All my wire came from an industrial supplier, not from a home-improvement store.  This is industrial strength. The real-deal.  I did this the first time with the V6 and it lasted flawlessly for 5 years.  This time around I expect it to last much longer since we are braking ground instead of switching hard voltage.
  • Relays – buy only the best (mine are Bosch) and don’t be stingy.  Relays are the way to go.  Once you get the basic principle of how they work they are fantastic.  This folks, is not rocket science and is not black magic.  Relays work and if you do it right, they last forever.
  • Use the proper tools.  I say again:  use the proper tools  I used good quality nippers, soldering gun, heat gun and crimping pliers.  The Weather Pack connectors require a special crimper.  Use the best you can afford.  Otherwise you will have crappy connectors and this will lead to electrical problems and the dreaded “Lucas Syndrome” where wiring turns into very expensive blue smoke.

I could write about this forever but then again, I would bore the hell out of you.  If you have any specific questions let me know and I can address them in a separate post.

Go do some wiring!  It is not as complicated as the harness “makers” make you believe it is…  🙂