Revs bouncing off 1k rpm when shifting to neutral

[suhhh]

Title Edit: RPMs* bouncing off 1k rpm

Hi all,

Wondering if anybody has experienced this or knows the reasoning as to why this happens as I've found someone else with an aftermarket exhaust on their BRZ experiencing the same thing as me.

When I am driving in gear and shift to neutral to coast, the RPM will drop but bounce off of 1k before going back down.

I have 1800 miles that were all driven with a stock exhaust and I'm fairly certain I've never noticed this before until I installed my MXP catback last night.

Someone else told me that it seems to be normal and that the Hyundai i20n also experiences this. Could anybody confirm this and explain the reasoning why this happens? Thank you!

[mazeroni]

Originally Posted by suhhh

When I am driving in gear and shift to neutral to coast, the RPM will drop but bounce off of 1k before going back down.

GEN I does this. Usually it happens with the AC on due to the strain on the motor which has the tendency to dip the engine to around 500 rpm. So I think in that case it is to try and prevent a stall.

But it is most pronounced when backing into a space when doing a lot of quick short revs. The car will go to idle and then rev 3~4 times to around 1K before smoothing out. I suspect this behavior has to do with emissions and ensuring that any unburnt fuel combusts in the engine and not in or after the catalytic converter.

There might be other causes, but I think the reasoning of it being emissions related is pretty sound.

[sds]

Normal. This happens in all my other manual cars.

[suhhh]

Originally Posted by mazeroni

GEN I does this. Usually it happens with the AC on due to the strain on the motor which has the tendency to dip the engine to around 500 rpm. So I think in that case it is to try and prevent a stall.

But it is most pronounced when backing into a space when doing a lot of quick short revs. The car will go to idle and then rev 3~4 times to around 1K before smoothing out. I suspect this behavior has to do with emissions and ensuring that any unburnt fuel combusts in the engine and not in or after the catalytic converter.

There might be other causes, but I think the reasoning of it being emissions related is pretty sound.

Thank you for this! Yes, I've talked with a few others and it seems like this is normal because of emissions. First time I've ever dealt with this on a car so I was just unsure

[suhhh]

Originally Posted by sds

Normal. This happens in all my other manual cars.

Appreciate it thanks! Guess I just didn't notice it until I installed my exhaust

[timurrrr]

Originally Posted by suhhh

When I am driving in gear and shift to neutral to coast

Why are you doing this for though?
You're burning fuel while the engine is idling, and you don't have drive if you suddenly need it in case something unexpected happens.

[suhhh]

Originally Posted by timurrrr

Why are you doing this for though?
You're burning fuel while the engine is idling, and you don't have drive if you suddenly need it in case something unexpected happens.

Well in today's case, stop signs lol

Not throwing it in neutral on highway speeds, just residential roads when there is an upcoming stop

[timurrrr]

Originally Posted by suhhh

Well in today's case, stop signs lol

Not throwing it in neutral on highway speeds, just residential roads when there is an upcoming stop

Ah gotcha.