[42395_skyline]

I thought it was just a tuning thing in sport, but after I got the JB4 and catless DP I figured that being on a set map I wouldn't have any difference with overrun in any mode but it still has little overrun in comfort and a lot in sport. What's going on?

[3.0L]

Originally Posted by 42395_skyline

I thought it was just a tuning thing in sport, but after I got the JB4 and catless DP I figured that being on a set map I wouldn't have any difference with overrun in any mode but it still has little overrun in comfort and a lot in sport. What's going on?

What do you mean by, "Overrun?"

[42395_skyline]

Originally Posted by 3.0L

What do you mean by, "Overrun?"

The pops and burbles that are heard when you let go of the gas but stay in gear when in sport or sport+ in lower RPM.

[K8_M235i]

Originally Posted by 42395_skyline

I thought it was just a tuning thing in sport, but after I got the JB4 and catless DP I figured that being on a set map I wouldn't have any difference with overrun in any mode but it still has little overrun in comfort and a lot in sport. What's going on?

Catless will do that. I have a resonator delete and it burbles more in both modes.

The car is tuned to burble with factory exhaust. When you take away noise canceling things, such as cats, it makes sense that it would burble more.

[Ron Jeffries]

I have m240i with MPE. It definitely burbles more in Sport than in Comfort. I believe that ALL burbling is done by fiddling with fuel and such. It's art: they could suppress it entirely by just shutting fuel flow clean off.

My 135is popped and crackled, and it continued longer, essentially forever as you coasted down in gear. I liked that better. I'd pay to get that sound back.

[SlickShift]

Originally Posted by Ron Jeffries

I have m240i with MPE. It definitely burbles more in Sport than in Comfort. I believe that ALL burbling is done by fiddling with fuel and such. It's art: they could suppress it entirely by just shutting fuel flow clean off.

My 135is popped and crackled, and it continued longer, essentially forever as you coasted down in gear. I liked that better. I'd pay to get that sound back.

Same. I had a performance axle back and a resonated midpipe on my 135i and loved those burbles way more. They were actually real and sounded better too. Still love this car. Just so much more "synthesized" though.

[42395_skyline]

Originally Posted by K8_M235i

Catless will do that. I have a resonator delete and it burbles more in both modes.

The car is tuned to burble with factory exhaust. When you take away noise canceling things, such as cats, it makes sense that it would burble more.

I know that, but my question is why when using a JB4 tune it doesn't have equal overrun since the tune is the same regardless of comfort or sport.

Originally Posted by Ron Jeffries

I have m240i with MPE. It definitely burbles more in Sport than in Comfort. I believe that ALL burbling is done by fiddling with fuel and such. It's art: they could suppress it entirely by just shutting fuel flow clean off.

My 135is popped and crackled, and it continued longer, essentially forever as you coasted down in gear. I liked that better. I'd pay to get that sound back.

I figured it was a fuel thing, but why does it not do it when I have it on map 2 in comfort the same as in sport, since fueling should be the same using the same map?

[Ron Jeffries]

are you saying you have somehow overridden comfort and sport to use the same map? then I don't know, unless there's more in there than just the map, which quite possibly there is.

[XutvJet]

Exhaust overrun in later model BMWs and other cars is the result of injecting a small amount of fuel once the throttle is released (no spark). The air and fuel enters the hot manifold and combusts somewhat randomly causing the sound.