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by ilyt 1117 days ago
I can imagine bitflip in one of the tables could be pretty dangerous and not catched by watchdog
2 comments

Not really. What's it going to do, make the engine run rich for a fraction of a second until the next time it recalculates the mapping?
Yeah, the kinetic energy associated with a running engine (flywheel to entire vehicle mass) makes it rather difficult to stall from a single cycle problem, especially given that it consistently recalculates and checks everything multiple times before the timing signal is sent.

The engine feels like it’s running fast, but it’s really slow compared to ECU’s ability to observe it and respond to it. A single missed signal would just result in a misfire.

> kinetic energy associated with a running engine (flywheel to entire vehicle mass)

Like the notoriously hard to stall Citroën 2CVs and Dyanes, where roughly a third of the total weight of the engine was the ridiculous flywheel.

They could chirp the tyres in first, second, or third gear if you got all that mass spinning fast enough, not from power but from momentum.

Mapping is not recalculated in flight, it is loaded from flash (or via obd when tuning) and normally not reloaded till restart. You might have some luck with short/long term trim fixing it, or not.

If you're lucky ecu might crash or run rich in that one rpm/load point, if not it might run lean entire highway drive, if say a bitflip happens to flip lambda probe settings to always show mixture being too rich.

I saw a 30 second segment in something I'm sure was about F1 engines that had something on a dyno and they flipped (while running) from the engine map to an ai predicting the engine timing per-firing and you could hear the thing smooth right out.

So no I imagine there's actually quite a lot of wiggle room to be off. Less so if you want it to last a million miles. But 30k?

Well, yeah on top of one in billion chance of bitflip you'd also have one in million chance that the bitflip would cause it doing something incorrectably wrong.

There is a lot of protection in modern engine, like retarding timing when there is a knock or long/short fuel trims to correct for any changes in the sensors.