[302Blue]

Has anyone else noticed with the manual in the V6 that if you heel-toe or downshift to use engine braking that there's a weird spot around 3,000RPMs where the vacuum braking effect abruptly loses it's effectiveness?

This isn't really an issue or anything, I don't think it's at all detrimental to the car. I was just curious if anyone else had observed it and knew what it was from. My guess is it may be caused by the engine switching from the larger overhead cam to the smaller one.

[mvp88]

I honestly haven't noticed it. That's not to say it doesn't happen. Also I've got the6 piston Brembo's up front so I don't engine brake as much maybe.

[Danelt2017]

I have the same thing happen. I always assumed it was the displacement on demand kicking from 6 to 4 cylinders. When it happens to me the exhaust sound gets quieter and as you mentioned loses the engine braking effectiveness.

[302Blue]

Originally Posted by Danelt2017

I have the same thing happen. I always assumed it was the displacement on demand kicking from 6 to 4 cylinders. When it happens to me the exhaust sound gets quieter and as you mentioned loses the engine braking effectiveness.

I thought the manual didn't have the AFM (cylinder switching) on it for the V6? I thought I read somewhere only the V8 has it on the 6 speeds.

[cryssm]

Originally Posted by 302Blue

I thought the manual didn't have the AFM (cylinder switching) on it for the V6? I thought I read somewhere only the V8 has it on the 6 speeds.

You are correct — only the auto V6s. I'm not sure about the SS M6.

I've experienced it before; though, I can't say for certain it's around 3k RPM. I'll have to devote more attention next time it happens.

[302Blue]

Originally Posted by cryssm

You are correct — only the auto V6s. I'm not sure about the SS M6.

I've experienced it before; though, I can't say for certain it's around 3k RPM. I'll have to devote more attention next time it happens.

Ah wait I think the SS just has the skip-shift, not the AFM.

[Danelt2017]

You all are right about the autos being the only ones to have AFM. I pulled out my owners manual and it says all V8 and v6 with auto have it, at least for the 16-18 I assume. I cant believe I thought I had it all this time. Must be something else with fuel and throttle being controlled making it feel slumped at 3k on deceleration.

[302Blue]

Originally Posted by Danelt2017

You all are right about the autos being the only ones to have AFM. I pulled out my owners manual and it says all V8 and v6 with auto have it, at least for the 16-18 I assume. I cant believe I thought I had it all this time. Must be something else with fuel and throttle being controlled making it feel slumped at 3k on deceleration.

Yeah, it's just really a weird affect. Nothing during acceleration, only when engine braking on deceleration.

Wish I could find out from GM engineers directly if it's the dual cam switch or something else like the throttle control you mentioned.

[cryssm]

Originally Posted by 302Blue

Ah wait I think the SS just has the skip-shift, not the AFM.

Originally Posted by Danelt2017

I cant believe I thought I had it all this time.

No worries!