[byanchu]

The RPM on my Q60 is no different at 30 seconds after a cold start than it is at 25 seconds, but the exhaust loudness is considerably different. Again, both my superbikes have EFI, one has an Akrapovic open exhaust.

I don't know about you but during a morning cold start, my Q60 definitely drops RPM (from 1k to about 650) after 30 seconds. I imagine though that your bikes are loud because you don't have mufflers.

 

[Bevo]

I don't know about you but during a morning cold start, my Q60 definitely drops RPM (from 1k to about 650) after 30 seconds. I imagine though that your bikes are loud because you don't have mufflers.

Next time you start your Q60, take note of the RPM and the time it changes. I regularly sit in my car for 2 minutes after a cold start and watch the RPM the whole time. FYI, an Akrapovic is a muffler.

 

[Bevo]

I don't know about you but during a morning cold start, my Q60 definitely drops RPM (from 1k to about 650) after 30 seconds. I imagine though that your bikes are loud because you don't have mufflers.

Is your exhaust loud AF for 25 seconds? Is there a slight bump in the RPM along with a dramatic drop in exhaust volume, while the RPM stays at the cold start level? Mine has always behaved that way.

 

[byanchu]

Is your exhaust loud AF for 25 seconds? Is there a slight bump in the RPM along with a dramatic drop in exhaust volume, while the RPM stays at the cold start level? Mine has always behaved that way.

Yes it is loud for 25 seconds, then the RPM drops from 1k to 650. What RPM does your car cold start at? At idle?

 

[Malmby]

Akrapovic is a muffler.

I feel like that downplays just how high quality Akrapovic exhaust components are; some of the absolutely best exhaust components you can find.

 

[MW17Q60RS]

The high revs at cold start is for emissions. CATs are not fully effective until they are up to a high temp (~800 degrees). The engine is set to idle at higher RPMs for a few seconds to get the CATs up to temp quicker, preventing fewer emissions from entering the atmosphere.

This is why this happens on both Gs and Qs.

Spoke to Infiniti and they said there was a separate module on the motor. I think they said timing control module maybe. Whatever it's called, it fluctuates fuel delivery during start up to heat the Cats quicker, so what you're mentioning sounds similar to what Infiniti told me.

I do think that cold heat shields, cats, wastegate positioning, etc all contribute to the rattling. I like Bevo Horn's fix, removing the heat shields and adding Sport exhaust ?

 

[Bevo]

Yes it is loud for 25 seconds, then the RPM drops from 1k to 650. What RPM does your car cold start at? At idle?

Saturday morning it was 60 degrees Fahrenheit in my garage. Idle at cold start was around 1200 RPM, as usual. At around 25 seconds into the cold start the exhaust volume dropped considerably as usual with no change in the RPM except a slight bump when the exhaust volume drops. Two minutes into the cold start the RPM was still around 1200 RPM as usual. After two minutes I put the car in reverse and backed out of the garage. After driving, when the car reaches normal operating temperature, the RPM is around 600 - 700. If I turn the car off for a short time, when I restart it the idle is 600 -700 and the exhaust volume is not at cold start volume.

 

[Hoopair01]

It is normal I'm told. Mine does it for 17.5 seconds, when it's cold. it is the waste gates, per our dealer. Normal