Category Archives: 2.4L Ecotec

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 ECOTEC Engine

Quick post for today…  Just wanted to show what the whole shebang looks like these days…  The ECM box has a nice cover on it.  Looks pretty cool, huh?

Click on each picture for a larger image…

Intake Repaired

After careful inspection and a thorough cleaning, the intake was repaired by my cousin Jim.  We did find another small crack that had developed on the outside of the plenum – not a leak, but more of a stress crack.  At any rate, with some new weld beads, the runners are all repaired now.  This is what things look like, after the repairs:

Here is a closer look at the affected area:

The face of the flange was found to be ever so slightly not 100% flat.  With a little machining, it is now level and flat.  I started putting this all back together last night.  Should have it all running today…



Looks like 2011 ends in a bang.  Literally.

Yesterday morning the sun was out so I decided to take bowtie6 to work.  Unfortunately, I did not press the “Start” button long enough, the engine turned for just a split second and backfired when I let go of the button.  I’ve had this happen twice before with no serious consequences but this time, we had a problem: the “bang” cracked the intake.

There is nothing wrong with the design of the intake or with anything else.  This was my mistake 100%.  I just call this a risk of running non-factory parts.  The new intake is all aluminium; this is what the intake looks like:

We had to make this intake up because there is no room for the original plastic intake.  Actually there is, but it would have required the steering column to be relocated bigtime and it was just not worth the trouble.  The intake you see above is made in several pieces.  The flange that bolts to the head came from GM Performance Parts and is water jet cut aluminium.  This all has to be made in pieces and welded in place as such.  The four intake runners are aluminium tubing, cut and bent to fit the oval ports on the GMPP flange.  They were welded to the flange from the outside otherwise there would be a lot of machining to make the flange perfectly flat again.

The runners then were fitted to a flat piece of aluminium which made the intake side of the long plenum on the top.  There was a bead ran on the inside of that plate.  Then, the rest of the plenum was shaped and welded in place.  The seams were filed smooth and it all looks like one solid piece.  Finally a flange was made and welded where the throttle body gets bolted with four screws.

All good, except that the four runners ended up with a delicate bead around them, on the inside of the intake plenum.  So, when the backfired occurred it caused the seam on number 4 runner to assplode.  Take a look:

Obviously, it doesn’t take much for the thing to have a major vacuum leak and cause the engine to fail to run.  Needless to say, with this crack RPM’s went through the roof!  One interesting thing about all this is the ECM was smart enough to figure this out, and basically shut things down.

The outside of the runners needs to be welded again (duh!).  Had we not had the backfire, this would have not been a problem.  The seal has been flawless but unfortunately the thing just could not cope with the force of the assplosion.  As you can see, the intake has been removed and will be welded back today.  I hope to be back on the road hopefully tomorrow.

Here is a picture of engine-side of things:

Sorry for the picture being so dark, but you can see there is not much distance between the intake valves and the actual intake itself.  Not at all.  Also, the gasket seems out of place because it is not pushed all the way up against the head – in reality it fits perfectly with the intake opening.

No worries though – this should be a quick fix…  🙂


ECOTEC Drive by Wire

All modern GM engines (LSx’s, Vortec’s, Ecotec’s, etc.) use the so called “drive by wire” or “fly by wire” throttle bodies.  Long gone are the days of actuating the throttle butterfly by mechanical means – ie, a cable – from the accelerator pedal to the throttle body.  Instead, the throttle butterfly is now controlled by a servo motor actuated by inputs from an electronic accelerator pedal attached to the ECM.  If you Google any of these terms, you will get plenty of info on how it works so I won’t go into the details.  This hangs up a lot of folks doing conversions and they end up using a throttle body with a cable.  We did not want to go that route.  What I do want to show here is how we solved some of these problems on bowtie6 while still retaining all the electronics.

The following pictures show what the throttle body looks like.  Since we are running a completely different intake manifold from the Solstice, the throttle body is bolted on a special flange on the new intake.  We could have used the plastic intake, but that would have been a major hassle with the steering mechanism.  In front of all this is flexible rubber tubing recycled from the Solstice.  The silver tube midways is the special housing for the MAF sensor and ahead of that (hidden by the radiator and ahead of the rubber bend tubing) is a K&N air filter.  On bowtie6, the air filter sits ahead of the radiator, right behind the factory grille allowing the coldest air to be pulled in.  However, this all comes at a price:  the MAF must be re-calibrated because of all the bends in the airflow.

This is what the whole shebang looks like…

Here is a closeup of the throttle body…

This is the stock throttle body as found in the Pontiac Solstice/Saturn Sky.  The grey plastic cover hides the stepper motor and the rest of the mechanism that opens and closes the butterfly activated by the ECM.  Here is another picture from the back of the throttle body showing the connector plug with the wires coming from the ECM.

Finally, here is what the inside of the throttle body looks like.  I reckon this all could eventually be fully polished, however I have doubts on how great that idea would be and whether there would be any benefit in that.  At any rate, it is what it is…

As you can see, there is no cable.  This is all controlled electronically.  Right before ignition, the engine does a “test” of the throttle body and yes, there is a split second delay.  If you pay attention, one can actually hear the stepper motor in the throttle body opening the butterfly to WOT and then back to the closed position.  Then ignition occurs.

If you are looking at all this and wondering where the traditional Idle Air Motor is then you are correct:  it is not here.  Idle is handled by the ECM and TPS.  From there, the butterfly opens to control idle.

Controlling all this requires the special matching throttle pedal.  Here is where things get interesting.  There are quite a few versions of these throttle pedals.  For example, Vortec engines have a certain version, GTO has another and Vette’s have yet another.  Along with that, some are all plastic, others are plastic with metal arms, some have 6 wires and some have 8 wires.  In our case, we used a throttle pedal used in the 2.4 Ecotec powered HHR.  The advantage of this pedal is that the actuator arm is metal, and thus can be cut and shaped to fit the location where it is mounted in.  This is what the one in bowtie6 looks like:

Sorry for the boring gray background (this is a sound insulating material glued to the Dynamat Extreme prepared body) but thought it be best to take this picture before I install the black carpet.  Otherwise we won’t be able to tell squat of what this looks like.  Some things to keep in mind about what you see above:

  • The pedal is still a little “crude”, if you will.  This is version 1.0 of the pedal.  So far even though it works perfectly there is some issue with the exact angle of the plastic pedal itself.  As you can see it is still a bit too straight.  I am planning to fine tune it by angling it a bit – the top needs to be brought down a little and the bottom needs to come up.  I just need to make up my mind on how far to make the angle.  It is also a bit long.  As you can see the top is rounded somewhat.  I need to make the bottom rounded as well.
  • The “travel” takes some getting used to.  This is a small compromise but this has to be retained because this is the way the ECM is expecting the signal to be sent.  If you look closely, there is a plug at the top with some wires going into a housing.  This is where the potentiometer that translates pedal movement into a signal resides.  This is what tells the ECM what throttle angle is being requested.
  • Looking at the picture above would lead you to believe the metal “arm” hits the red body of the car at the top, right?  Nope.  The travel is not great at all and the arm does not touch the body at WOT.  I also own a 2.4 Ecotec powered HHR and the throttle travel there is equally short.  However, believe me – this is not a problem at all when driving the car.  The throttle has the same “look and feel” as a mechanical system does.  It just takes a little getting used to.

For those of you considering an Ecotec conversion, this is going to be a very important issue to figure out.  Like I said before, there are many different varieties of thottle pedals.  I have read where there are some that are actually meant for the V8’s.  Once you settle on the correct pedal to use, placement will require some adjustments.  Mine is close but not quite 100% perfect yet.

There is yet another alternative and that is to use a Lokar fly-by-wire system.  I think these were introduced at SEMA earlier this year.  I have done some reading about them but I have not seen one in person and have no idea how helpful it would be.  On the downside too is the price – they are quite price.  The stock GM stuff can be had for a few bucks at your junkyard or from auction on eBay.