For any add-on boards such as VR conditioners, optos and OEM interface boards
By HiramAbiff33
#52203
Hi, I'm new to the forum and I am very excited to learn about arduinos being used to open up a whole new world of engine management for everyone. I have a hypothetical question. Is it possible to use an Arduino in a way rather than for example a piggyback that steals and modifies the signal to the factory ECU you steal the signal going to the fuel injectors? you plug the factory fuel injector plug into the board it sees a signal to fire an injector and mirrors it on the output plug that connects to the fuel injector. The board then looks at a signal from a wideband sensor and determines if there needs to be an addition in spray duration or a reduction. The idea being if you can balance the fuel-air ratio for performance mods without the factory ECU even knowing it's happening you can pass smog checks because the factory ECU when hooked up to a diagnostic computer will appear completely normal and believe it is in control of the car. So instead of piggybacking, stand-alone, or parallel this would be hijacking. Is this feasible or are there a dozen complications with this theory that my lack of knowledge does not privy me to?
By Jason Green
#52312
To answer your question could this be done with an arduino, Yes...

But can this be done using the existing Speeduino firmware, No so this would need to be developed by someone who has a use case.

I would also add this is also going to result in the factory ECU fighting back on the next cycle as it will see more/less fuel than expected so this could result in a EML from the factory ECU and additonally this could result in RPM hunting.
By dazq
#53573
This statement
"without the factory ECU even knowing it's happening you can pass smog checks because the factory ECU when hooked up to a diagnostic computer will appear completely normal"

Makes what you are suggesting actually illegal in many places and countries .
This is why the speeduino obd port ONLY offers realtime (and fault codes eventually) and will NEVER support readiness or other legally required data.

Anyone offering such software would leave themselves liable to legal action by the powers that be!
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By Chris Wolfson
#53574
There is no point in designing something that does already exist and can be bought for the same price as a DIYS version would cost.
If you add up components for an Arduino based system with housing, in small numbers you will end up near to what this one costs.
https://www.ecumaster.com/products/digital-ecu-tuner-3/
Which is a perfectly working solution. You will need years to have something developed that comes only near its functionality.

The more you work with such piggyback solutions, the more you realize their limits and problems.

With some thinking, you can leave the stock harness, connector and sensors in the car. Just remove the stock ECU and wire in a second connector for the Speeduino, soldering into the cables running to the stock connector. You may run some additional wires for more functions. A clean installation should not worry any person locking at it in the engine bay.
For MOT you just remove the Speeduino and plug in the stock ECU. If you have removed any hardware, just put it back for a day.
You do that every two years, so an hour extra work is acceptable.
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By PSIG
#53580
HiramAbiff33 wrote: Sun Aug 01, 2021 4:33 am… The idea being if you can balance the fuel-air ratio for performance mods without the factory ECU even knowing it's happening …
Yet another issue is that cars and trucks have known if you alter AFR for 30 years or more. For example, when the EGR valve opens during various conditions, the stock ECM typically also alters timing and AFR and then looks for the change as confirmation. If your hijacking piggyback also alters the AFR, the OEM ECM will see it and throw a code for that emissions failure. BTDT

Using the same scenario, your new AFR will be less powerful or efficient as the timing is now wrong for your altered AFR, partially or completely defeating your purpose. Recognizing that is but one small example, could it be done somehow without alerting or confusing the OEM ECM? Sure, anything is possible with enough time and resources, but … :roll: Hey — try it if you like, but determine the numerous potential hurdles to quick or easy success before you get in that boat. IMO as an indicator, if it were either easy or legal, units would already be everywhere and cheap.

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