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I guess if it's not DI, but what new cars aren't DI these days? If you have a DI engine doing rev hold, it's not about mixture ratio.


The difference between DI and port injection is only which thing is escaping the catalytic converter. With port injection the engine is rich after lifting off the throttle, and hydrocarbons escape. With direct injection the engine leans out, and NOx escapes. In both cases the rev hang exists to keep the emissions system in its effective air/fuel ratio range. Every hanging MT car I ever owned was DI.


That's very odd. DI should only be firing a full shot injector as the air is coming in, or already came in. It really shouldn't lean out. If your DI car had rev hang, it's for other reasons.

https://www.roadandtrack.com/new-cars/car-technology/a329586...


We were discussing the 2015 WRX after all, it is port injected. The guy who wants to delete the rev hang from his VA WRX is advocating to blowing unburnt gas right out of the tailpipe, like a psycho.


Not true. Without rev hold it actually can go lean. The main reason for rev hold is to reduce oil vaporization.

https://www.carthrottle.com/news/what-rev-hang-and-why-do-pe...




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