Do factory Toyota ECUs actually tune themselves? if so by how much?

[adamaw11]

At some point in the past I was led to believe they do to some extent (I'm talking about a stock standard 20v silvertop ECU).

Surely they wouldn't actually self-adjust their fuel and ignition maps? unless they had wideband O2 sensors from the factory.

I'm thinking that back in the 90s, the extent of self-tuning would only be things like closed loop mode on cruise and idle, and temperature adjustment etc.

The reason I'm asking, is I've just tried fitting 380cc 1jz injectors to a silvertop 20v, bog stock standard ECU.
I only had a mix of about 15% ethanol in the tank, and after some cranking, it then started, idle hovered around a bit, then settled and idled fine!
No massive smoke clouds, or rich smelling exhaust, it just idled ordinary. How could the ecu adjust itself that much from 295cc injectors to 380cc injectors?!

with ~20L in the tank, I then threw in 10L E85, and took it for a drive, and it seemed to drive just fine, revved nicely and everything
Then I added another 15L E85, drove it again, no difference, no issues, cruises fine, makes normal power and revs happily, no hesitation or anything - as though the ECU just doesn't care, just adjusts for anything.

Are 380cc injectors not as much of a jump as it seems?

[trdee]

the ecu would at most have long term and short term trims via the o2 sensor. under what conditions those trims work and how much leeway they have i dont know.

bear in mind that with full e85 the mixture needs to be about 30% richer than petrol for the same lambda. your 380cc injectors are, conveniently, about 28% bigger than the original 295s. E15 would need only about 5% more fuel for the same stoich AFR, but at idle you can have quite a rich mixture and the car will still idle fine. also i have no idea whether there is any difference in injector deadtimes etc, which can also significantly affect AFR at idle.

at E50 or so you would be running no more than 20% richer than the ideal, which is near enough imo that the engine would probably not have too hard a time running on it. especially if the ecu is pulling fuel via feedback from the o2 sensor

[Shakotan_Aaron]

You dont have a wide band gauge? Could be a good thing to check out what its doing. You could potentially do some minor tuning with adjusting base timing, a adjustable fpr and air flow controller (silver top are Afm?)

[adamaw11]

So it seems its not as odd as I thought, when looking at all the numbers like that. The ecu might have only needed to adjust slightly if at all to cope with the variations, to at least idle properly.
So now I'm doubtful that factory ecus ever actually tune themselves over time, and its just a myth that some people say occasionally.

I havn't done any calculations to include injector dwell time or anything, but it would be good to figure that out.

I Don't have a wide-band on this car, but it would be interesting to see what it says.
I've wondered about using adjustable fpr, I guess that could make up for a few % if I need it.
Yes its AFM, I hadn't thought of playing with that, could be an idea.

meanwhile I squeezed in another 13L, making it currently about 39L E85 in a 50L tank. Still drives good, goes harder if anything, probably just the colder night air though.

I'm pretty sure by this stage it'l drive fine on full E85 with the 380cc injectors. The variations from the injector dwell time or them being less than 30% bigger I think are insignificant or compensated for slightly by the ECU.

[wilbo666]

A little bit of information in this document that used to be on autoshop101...


44 Fuel System#3 - Closed Loop Fuel Trim wqu.pdf

Cheers
Wilbo

[oldcorollas]

can fuel trim data/info be extracted from a Toyota ECU? those from particular era onwards?

[wilbo666]

can fuel trim data/info be extracted from a Toyota ECU? those from particular era onwards?

Pretty sure the data is available as part of the OBD data stream that is available from the Vf? pin...

The only problem is that the exact details and format of the data isn't particularly common place! (Or at least isn't documented in an open fashion!).

Cheers
Wilbo