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Piggyback tuning

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Hey guys,

So basically Andre explained to me before that when using a piggyback, it is not possible to tune under steady state conditions since the stock ECU operates in closed loop mode at this time and it will just correct out any change you make with the piggyback.

Is it fair to then say, a piggyback is only useful for tuning WOT? Meaning it will only be the 100kpa row for instance in an NA car that you can effectively "tune" ?

Or are there piggybacks that can do full tuning just like a stand alone would?


I think if you look for ecu that can co-operate to manipulate closed loop or open loop, its better to get a standalone ecu management.

Mostly piggyback are restricted to the adjustment and range increment certain rpm to interpolate roughly idea. depending on brand. But it is hard to compete with standalone. I prefer a cheap standalone such as MegaSquirts , Haltech. They got good help support and a lot tuner using it.

But this all depend what are you using this ecu for, drag race ? street purpose ? if street purpose, a piggyback is just nice to play around if you manage manipulate and tune it perfectly.

Andre, correct me if I am wrong. One could disconnect the O2 sensor (and remove the engine check light-bulb) to put the factory ECU in open loop mode to enable the piggy back to take control without restraints.

Depends on how your ECU reacts to that - I've had the misfortune of having to tune a car with an E-Manage Ultimate and we tried this method to get around the stock closed-loop setup battling us and the ECU threw a code and went into a limp home mode which resulted in some really erratic timing and fuelling decisions to be made by the stock ECU, very much stuff you didn't want to have to work with.

As Lith says, some times a CEL will cause all sorts of ugly side effects that make it impossible to tune the engine. I'll admit that I'm not a huge fan of piggyback ECUs but they do have their place for lightly modified engines - Note that imho the only place for an e manage ultimate however is in the bin :)

Usually the closed loop aspect isn't a deal breaker though as under those conditions you will normally want to be targeting stoichiometric. Of course it eliminates your ability to target leaner for economy but that's hardly a deal breaker. Generally the only time you're likely to need to make changes in the closed loop (cruise/idle) area is if you've changed to larger injectors. One mistake I often see with this situation is where no changes are made in closed loop as the AFR 'appears' to be ok due to the closed loop trims dealing with what would otherwise be an overly rich situation. As soon as you transition out of closed loop though this causes all sorts of headaches/driveability problems.

In this sort of situation the key is to adjust the fuel map so that the closed loop trims are as close to zero as possible.

So Andre, will the piggy backs be able to do steady state timing tuning via the MBT technique?

It should really. Ignition timing is open loop on the factory ECU side.

Nice part about my job, I only tune motorcycles. We just "flash" out the O2 sensor and never have to worry about closed loop operation.

chris1388, tuning ignition timing depends on the type of your piggy-back ecu. Sometimes it has no engine position sensor connected and one thing you could do is to retard the timing. Which piggy-back ecu would you use?

The ignition system isn't really closed loop, although it may be affected by feedback from the knock control system - This is dependent on the stock ECU. So in short, yes you should be able to use the MBT tuning technique to optimise the ignition timing. The only other consideration is that there may be multiple factors (or tables) at play inside the stock ECU that result in the final ignition advance that is delivered. This means that often the ignition timing may move around somewhat even under steady state conditions and this can make our job a little more tricky.


I hear you on the Emanage Ultimate. It is however installed on the Suzuki Ignis via a custom plug and play harness and has been "tuned" on an inertia dyno by local "tuners". It has shown a noticeable increase in both torque and power throughout the entire rev range.....which means it is doing something right....I think at is responding to input from the emanage.

When it was installed and tuned I was not as versed as I am now so I plan on getting my equipment, wide band, knock monitor etc and having a go at tuning it myself.

I know for sure they did not do any part throttle tuning, only WOT.

There is one load bearing dyno here in Trinidad so my plan is to go and get some experience/practice steady state tuning the ignition map and also see how safe these guys have the WOT area of the map tuned.

What do you think of this plan Andre?