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Odd turbo behavior, calculation error? (UE4)


In trying to reproduce the behavior of the ecoboost in the new raptor, I ended up with a turbo engine which doesn’t seem to ever open its waste gate, that is it never reaches the maximum boost set in the turbo page, and yet changing the max boost still changes how the engine behaves even though the boost curve never reaches the value set in the max boost value.

What’s going on here? Is this a bug or is the game simulating something about the waste gate changing?


Indeed that is a bug that has been with us for a long time, I don’t think we get around to fixing this until the FI revamp, as it doesn’t affect too many “normal” engines.


In spending some more time messing with this engine, I think the current turbo model seems to base the boost it’s delivering solely on RPMs, where typically, if given long enough, they’re able to spool up at considerably lower RPMs.

And just for reference, I found out that the actual raptor’s V6 does actually reach a set boost, but I wasn’t able to mimic its actual power curve. Trying to recreate an actual engines seems like a useful way to sanity check the designer, as I can’t get the turbo spooling characteristics accurate but if dyno sheets (that include AFRs) are to be believed the actual engine takes a lot more fuel to do what it does, which as far as I can tell, doesn’t help what I’m trying to do with this engine.

Also I’m finding that I kind of think the old version of the graphs might have been better? Tuning this engine has seemed like being able to see power, torque, boost, and efficiency all at once again would probably be better. Also seems the flowbench will never read less than 1.0 for the compressor?