Opinions Pls. POP from exhaust on geaer change

[Boink Boink]

Dear Sifus,

After owning a turbo car for a while, its been great fun. I have noticed that sometimes, in certain situations which I cannot seem to figure out when, upon changing gear, there is a pop from the exhaust.

So far, it happens when your accelerating hard, I think, and happens just as you let go the accelerator, press the clutch for the gear change.

Not a problem as per say, I also noticed it a lot on other turbo cars before, can anyone explain the pop?

Many thanks

 

[Fluffy]

pop?? fire?heheeh

could it be back pressure?

 

[sta]

not only turbo cars , normal cars with modifed muffler will also have this sound

 

[Fluffy]

ohh..that *pop..pop prop prop pop* sound...haha yeah...i've heard a kancil have that sound too...

 

[Battousai]

When you run the car hard, and change gear there is a brief overrun. Petrol is being injected at a high rate, but no air enters the cylinder because the throttle is closed during gearchange. So the fuel cannot burn in the cylinder, but ignites when it touches the hot exhaust manifold. Then you hear the pop sound. This is especially apparent on turbos when you change gear, because the BOV lets all the air out of the intake tract.

 

[Fluffy]

OH! okay okay...i was damn curious on this topic for sum time...
thanx bro battusai.

btw..does this occurance also creates the "flames" in the exhaust?
the "flames" also happens when a downshift is done..
rite?

 

[Battousai]

correct

 

[Fluffy]

fuiyo..i bangga..hahah thanx battusai.

 

[Boink Boink]

Thanks. Great to have confirmation.

Just to add. The explanation is for the SINGLE POP.

The pop pop pop pop you hear from the heavily modded cars... that one, is it the same explanation?

 

[Fluffy]

its the same thing...

more pops is just because more escaping fuel that's running thru the exhaust manifold..

 

[kRiminaLz]

anti lag response...
evo3 is it?

 

[jinkl]

erm my evo3 oso pops it hehehe
i see flame in small once in a while
the person behind my car see it usually hehe and they tink im showing off , arggghhhh

 

[Fluffy]

erm my evo3 oso pops it hehehe
i see flame in small once in a while
the person behind my car see it usually hehe and they tink im showing off , arggghhhh

hahaha surely they'll be scared...ur car's a fire breathing dragon! heehe

 

[Joeker]

"Misfiring system"

 

[nashlovebrown]

dude sometime ur centre bullet changes also might course that pop sound...because i got 2.5" centre bullet with 2" piping i can hear that pop sound when i change gear...who cares but the pickup good, enough lorrrrr

 

[jinkl]

Joeker : where got misfiring system , only got meriam buluh

 

[RSI]

Normally happens on engine that uses airflow meter and blow off valve venting to atmosphere, less aparent on engine which uses map sensor.

Batusai is correct. To elaborate: Your turbo makes boost and this boost is metered by the airflow sensor, more boost the airflow sensor detects, the more fuel it will inject. When you lift off the throttle quickly, the boost that was made suddenly vents to the atmoshere, that boost was already metered by the airflow sensor hence fuel is injected but the boost didnt make its way to the engine so you get an overly rich mixture which does not combust in the engine. When the overly mixture hits the hot turbine it ignites. And you get the exhaust 'pop'. That's why it happens normally when you drive your car hard whereby the turbine gets really hot.

 

[jinkl]

so i guess its bad in sum ways

 

[Fluffy]

erm...im guessing in a long term..is not really good la..