Will H4 ECU work with the EZ30? **Edit: Topic Solved**

[Kasmodean]

I know GM uses the same ECU for some of its 4 cylinder engines as its LS engines. Just attach the right engine and reflash the ECU and you good to go. How does this work for the EJ2xx and the EZ30? Can i use a EJ2xx ecu and reflash it to work with the EZ30? I see most people that use the EZ30 just use a standalone, but in my state this is problematic for registration and annual smog. It is much easier if I can use the stock ECU.

[Wayne Presley]

No it wont

[aquillen]

I don't believe any of the 4 cyl ECU's have the hardware inside (two more drivers for injectors, 2 more for coils) and some other things. The worst of that is pinouts, additional timing pulses and no doubt other odds and ends specific to the 6 cyl motor vs the 4. There has been quite a bit of effort now and then by some folks on the Romraider project to decode the H6 ECU logic. One or more said the code was very strange, no one posted a breakdown, even though one guy kept talking about a friend who was supplying him test code that worked - he never divulged a contact for the rest of us, and it was some time back - threads all are dead now, and in the end I think he got rid of the vehicle without ever being happy with it.

I'm doing an '02 H6 JDM motor, a US LL Bean Outback ECU although I don't think the "mix" matters at all here. I'm in stingy mode where my time is cheaper to spend than my money, hence no drop of $2K plus just yet on aftermarket ECU stuff. I'll fight the factory ECU for quite a while before I cry uncle and write off emissions compliance in my project. As to the JDM motor, at one point I thought there was a difference in one or two of the engine sensors, but a while back I was studying all the parts of the engine controls puzzle and concluded this JDM has all the stuff the US ECU is looking for. We'll see...

This is a complicated effort, and I've not run it yet - easily 6 months or more away from that step. So I can't prove to anyone as yet whether it will work. My plan is to keep all the emissions stuff and so on so it does have what it needs to not throw errors, because I've not found an ECU hack or Romraider mod that will work around those signals, inputs, etc. If you are facing "hardcore" emissions testing, that means the testing system will expect the ECU to report that it has completed specific "drive cycles" and is ready to report results on those sensors. For example, the testing process done by the ECU to detect fuel system leaks is sophisticated and only happens under specific driving conditions, if you clear codes this will not show as satisfied until the ECU can run all the sensors, valves, and so on needed to test the tank and such - a rigorous emissions testing site will require you present the car with that drive cycle testing "ok". Romraider guys figured out how to make this sort of stuff go away on the 4cyl, but not the 6cyl.

This means you could "clear codes" and maybe look good on your dashboard for perhaps a few (at most) drive cycles, but the testing system will know that some tests have not been performed by the ECU since it was cleared - and you'll fail and be asked to come back after either a service visit or driving the vehicle. Since the states still have testing all over the map, who knows what you could run into with an emissions testing program. I don't even have testing here but live adjacent to counties in Indiana that do (lived in a couple of them before - what a PITA). But I might sell this someday and want to be able to take any buyer without this being an issue.

There is also another driveability piece - the H6 in the US and most of the world was only sold with automatic transmission. So the engine ECU program (that I haven't found code changes for) expects to talk to the auto's Transmission Control Module - TCM- another computer. No comm = check engine. I've put together a board (pretty much collection of resistors, couple transistors) and tucked it inside my TCM to make it think it is connected to the solenoids, temp resistors, etc. of the missing automatic. So I can go manual. This also tries to solve reported issues with idle-dying engine at stops when you don't have the auto. I have an '02 and an '03 ECU and have had each one connected to this '02 TCM, with my poser circuit setup inside the case. Without my circuit, the Subaru Select Monitor (freeSSM version, which by the way works very nicely) was reading solenoid faults from the TCM. With my circuit added, I was able to satisfy each solenoid, set a specific transmission temperature value, see my neutral/clutch in-out changes get read by the TCM and so forth. So I have expectations that the setup will work.

To be fair and open about this I didn't invent much of this - I dug it up in a few dozen spots on the Internet. There are some Vanagan project guys (Subi motor in the Volkswagen vans, etc. that have fought and written about some of these issues, and other guys around the world who posted their 4 banger to 6 conversions woes and solutions). I've made some changes here and there, but I'm working with others' information.


Lastly, to really make it interesting, loose about 30 pounds of cast intake manifold, and for the look, I'm fabricating a carbon fiber intake setup, so I'll be missing the intake control valve setup that changes runner effective lengths at about 3800 rpm (forget the exact number), and I know there is fuel mapping that gets jumped at that changeover spot so I'll either deal with a hiccup each time the engine goes through that RPM, or rig up an external microcontroller that monitors RPM, the control valve signal, etc., and fudges the injection pulse width. Some of that mapping stuff is probably one of the items that was catching out the guys trying to decode this version of ECU. I've dumped the code easily enough from these two ECU's but have not had time (I looked at it for a couple hours but this is a time black hole - decoding the H6 engine maps), and not sure I have even the inclination at this point, to spend a zillion hours trying to unscramble the rom data. Others with experience in Subaru decoding didn't get there so not sure I want to spin my wheels on it.

So in other words, my take on this is different from what some have written - that is you HAVE to use an aftermarket ECU for the 3.0 ($2000+ later and no emissions testing allowed). I'm betting a lot of time and energy that it is possible to get the EZ30 to run on it's original ECU, even with a manual trans, if you satisfy the TCM need by having it there, then fooling the TCM with some connection signals, jiggle the clutch and neutral signals into the TCM & ECU to satisfy them on that stuff too. There is very little known on how to squash the check engine stuff if you start deleting emissions, so I'm keeping it all in my build just to keep it happy. It ran in the original cars, it can run in this one too. Part of my thinking here is I can read and understand the info on each emissions device in this "system" and incorporate that back into the build, make it work as part of the project challenge.

That said, until it works it is all just plans of mice and and a man. So we'll see.

[Kasmodean]

Thanks Wayne and Art.