honda fit L15A ECU matters

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howardyin

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Joined
May 23, 2020
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23
I am now studing things about convert the L15A or L15B engine , I wondering the reasons and the way the orther guys change the engine ECU.
what if just use the ECU used in the car? If changed to the new one, which ? where to buy?
 
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rv7charlie

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Nov 17, 2014
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1,451
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Jackson
Automotive ECUs are rarely just EngineCUs these days. They typically run everything from the door locks to the transmission and traction control. Pulling it from the car and convincing it to run the engine in the a/c involves 'tricking' the controller into either believing that all that other stuff is OK, or into ignoring it. Since the mfgrs don't share the hundreds of thousands of lines of source code in a typical controller, we can never know whether we've worked around every condition that could cause the controller to go into 'limp mode', or stop outright. While some have done it without incident, a lot of others have had all sorts of problems, up to and including fatal ones. Even if you've bypassed all the dangerous failure modes, you still need some method of leaning the engine, for anything intended for more than around-the-patch puddlejumper operation.

Numerous aftermarket options exist, from the open source Speeduino to Micro/Megasquirt, to purpose-built aviation controllers like the SDS. All require money, of course, and some level of tuning skill.

Charlie
 

Kiwi303

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Jul 22, 2015
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286
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En Zed. Aka The Shire.
Any car which has Electronic stability control, which these days has been a mandatory govt/DOT requirement to be allowed on the market as a new car in most of the developed world has the ECU running the ESC natively, since to control wheelspin and so on they often pull the fuelling or retard the ignition to reduce power until the wheels pick up. It's easier to program if it's part of the electronics that is running the fuel/ignition in the first place rather than piggybacking in.

It's to the point that you cannot engine-swap many new cars, no replacing your V6 with a V8 because the ECU looks for factory installed chassis monitoring sensors and freezes if it's not identical to what it was first installed in.

Personally, LINK ECU, just local bias as they're NZ and I'm NZ ;)
 

howardyin

Member
Joined
May 23, 2020
Messages
23
Automotive ECUs are rarely just EngineCUs these days. They typically run everything from the door locks to the transmission and traction control. Pulling it from the car and convincing it to run the engine in the a/c involves 'tricking' the controller into either believing that all that other stuff is OK, or into ignoring it. Since the mfgrs don't share the hundreds of thousands of lines of source code in a typical controller, we can never know whether we've worked around every condition that could cause the controller to go into 'limp mode', or stop outright. While some have done it without incident, a lot of others have had all sorts of problems, up to and including fatal ones. Even if you've bypassed all the dangerous failure modes, you still need some method of leaning the engine, for anything intended for more than around-the-patch puddlejumper operation.

Numerous aftermarket options exist, from the open source Speeduino to Micro/Megasquirt, to purpose-built aviation controllers like the SDS. All require money, of course, and some level of tuning skill.

Charlie
thanks ! great info for new guys like me
 

pfarber

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Joined
Feb 21, 2019
Messages
768
Location
Pennsylvania
Automotive ECUs are rarely just EngineCUs these days. They typically run everything from the door locks to the transmission and traction control. Pulling it from the car and convincing it to run the engine in the a/c involves 'tricking' the controller into either believing that all that other stuff is OK, or into ignoring it. Since the mfgrs don't share the hundreds of thousands of lines of source code in a typical controller, we can never know whether we've worked around every condition that could cause the controller to go into 'limp mode', or stop outright. While some have done it without incident, a lot of others have had all sorts of problems, up to and including fatal ones. Even if you've bypassed all the dangerous failure modes, you still need some method of leaning the engine, for anything intended for more than around-the-patch puddlejumper operation.

Numerous aftermarket options exist, from the open source Speeduino to Micro/Megasquirt, to purpose-built aviation controllers like the SDS. All require money, of course, and some level of tuning skill.

Charlie
Actually ECU's are really still JUST ECUs. But they will want to talk to a data bus (CAN) and also to the OTHER modules like the body control, stability, ABS, gauge cluster etc. Take away any of those other controllers and the ECU will refuse to do anything.

I would not want to run a stock factory ECU in an AC. Either find a way to load an aftermarket ROM for program or replace it all together with a Megasquirt or SDS type replacement.
 
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