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digs

Non-self learning ECUs (early Celica/Mr2s) prob daft question

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Hi, as above, might be a stupid question....

 

My rev2 3SGE in the MR2 has no o2 sensor or cat - and assume early Gen5s are similar (mine does not have a cat either).

 

In this case, can i assume the ECU is not self learning as it has no air fuel feedback going into it, therefore runs on set maps based on rev, load, etc. Possibly with knock adjustment ? Only feedback is from timing, but it wont know how much it is over fueling or not ? Hence the little pot that adjusts fuelling up or down.

 

Question being based on using piggyback ECUs to these - if not self-learning then perfect for piggybacks as the signal adjustment for fuelling will not be self learnt out of the set up ? 

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There's the air meter (MAF or MAP), so it very much knows how much air is going in. Self learning is a pretty grandiose term for switching LUT based on some basic sensor input, which is what most ECUs do anyway.

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Yeah so it knows Load, but doesn't try to match a certain air fuel ratio as it doesn't know the ratio ? ie always kind of on open loop (it never adjusts to get to stoic/14.7, its just has a map that assuming all is good at the right fuel levels, but would never know that its not ?)

 

Its that switching that buggers up some piggybacks I think, as it exaggerates to accommodate the piggyback tune.

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AS far as I'm aware, the only self learning on the later ECU's is idle RPM and knock retard.

You are referring to open / close loop mixture control. On the GT4's it only goes to close loop for idle and cruise, I suspect the same may be true on the N/A versions as there are power gains from running richer on full throttle and the regulations of the time only required accurate mixture at idle and light throttle.

I presume you are thinking of trying to run weaker on cruise to gain a wee bit of ecconomy ?

 

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Hi - kinda, trying to get my head round it. 

 

So if understand the na without o2 is similar - it tries to keep an idle but apart from runs on a set map, including cruise. 

 

So yeah in a way, its pretty straightforward to change the map - hence the adjuster pot. You could run that pot inside the car potentially if you wanted to lean out or enrich I guess. 

 

Might fit the wideband to the na just to see what the fuelling looks like :)

 

Currently just learning how ecu s control things. 

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