Backfire issue

[Kingsford G]

I`m having a backfire issue with my P2 2.4t5.The car is MTE remapped and doesn`t feel as responsive low down as my unmapped one felt.Also there is over 30 vacuum reading on the gauge when I let off the throttle while driving and it goes back to normal 25 once I press the brakes.The cambelt was done while it was an explod.It does less mpg than my other car did tho had a cleaned set of greens fitted.The backfire was present with the stock injectors too.Any ideas?

[960kg]

I`m having a backfire issue with my P2 2.4t5.The car is MTE remapped and doesn`t feel as responsive low down as my unmapped one felt.Also there is over 30 vacuum reading on the gauge when I let off the throttle while driving and it goes back to normal 25 once I press the brakes.The cambelt was done while it was an explod.It does less mpg than my other car did tho had a cleaned set of greens fitted.The backfire was present with the stock injectors too.Any ideas?

Just to help!......

A Quote.........
• The vacuum gauge reads in either millimeters of mercury (mm Hg) or inches of mercury (in Hg). Those measurements mean the vacuum is strong enough to support a column of mercury in a tube to a height of so many millimeters or inches.

• 0 in Hg is equal to atmospheric pressure. A fully loaded engine at wide-open throttle will reach close to this reading.

• 30 in Hg is referred to as a perfect vacuum. It is a point where there is no pressure at all. It is a theoretical number because it is impossible to achieve. An engine decelerating on closed throttle will reach close to this reading.

• Healthy engines will create more vacuum in their inlet manifolds than worn engines. So a pressure comparison between a known healthy reading and the engine you are testing can assist in determining the state of wear of the engine.


So your Vac. reading is OK...


Backfire in the exhaust is not only as one thinks a rich mixture being blown off!

Do you remember school in the science lab. ...teacher had a tin with two holes in it ...gas was put in the tin from a tap and turned upside down on the bench one hole was lit as the gas escaped and the other hole let in oxygen to replace the gas used ...when the mixture was weak and correct the tin blew up in the air from the explosion!

In other words you may have a leak in the exhaust system that you cannot hear or see.....an O2 sensor may even richen the system as it susses out the problem in the exhaust explaining the mpg...

[LeeT5]

It is well known for P2R models and P2 T5's that are mapped to backfire now and again. Mine does it especially if I come off throttle at low revs whilst pulling away from standstill and going for the gear change.
Normal mate AFAIK. I believe its unburnt fuel being dumped into the hot exhaust when you come off throttle. (if anyone wants to correct me on that...feel free)
Mine has also popped in the exhaust ever since ownership, especially after remap. It's not like a full blown backfire that causes everyone to "TAKE COVER!!!!!!!!!".....more like a loudish pop!

[stribo]

Ours pops too after the remap, and has been seen shooting flames.

[LeeT5]

Ours pops too after the remap, and has been seen shooting flames.

Yes. I'm going to stick my iPhone to the back window and record mine at night to see if mine spits flames!

[Kingsford G]

It is well known for P2R models and P2 T5's that are mapped to backfire now and again. Mine does it especially if I come off throttle at low revs whilst pulling away from standstill and going for the gear change.
Normal mate AFAIK. I believe its unburnt fuel being dumped into the hot exhaust when you come off throttle. (if anyone wants to correct me on that...feel free)
Mine has also popped in the exhaust ever since ownership, especially after remap. It's not like a full blown backfire that causes everyone to "TAKE COVER!!!!!!!!!".....more like a loudish pop!

Mine is just the same so nothing to worry then.My S60 didn`t backfire tho and had a Rica 300 map,pulled better too.Today I came back with a leaky turbo return seal topping up oil,200mile trip.

[960kg]

When you take your foot off the throttle the fuel shuts off to the injectors...there is no feeding of any fuel unlike a carburettered motor to the engine!.......so if the fuel is not burning in the combustion chamber at that point to it`s best there may be a problem to why it isn`t burning as it should...

[Dream3r]

The backfiring can actually be fixed. I believe it might and been an unwanted result during their original calibrations that they elected to keep.

It gets more pronounced with exhausts etc.

It's a mixture of the on demand pump and injectors causing it.

Kingsford, I'm assuming you're running the correct map for greens?

[Harvey]

It is well known for P2R models and P2 T5's that are mapped to backfire now and again. Mine does it especially if I come off throttle at low revs whilst pulling away from standstill and going for the gear change.

Like this video then,I wouldn't call it a problem

.

[Kingsford G]

The backfiring can actually be fixed. I believe it might and been an unwanted result during their original calibrations that they elected to keep.

It gets more pronounced with exhausts etc.

It's a mixture of the on demand pump and injectors causing it.

Kingsford, I'm assuming you're running the correct map for greens?

All I know it is an MTE stage 1 mate done bfore I bought it by the previous owner with a receipt.I`ve run a set of greens on my unmapped 2.4t5 with GW made exhaust before with no issues and I had this exhaust on the S60 Rica mapped.This car seems like an old fart,push,some power and pop lol I changed the turbo when I bought it cos the original one was making noise under a slight boost and found the back wheel had a slight damage which could only be caused by a carbon from the engine so now the concern is can this backfire cause the kind of damage?I was lucky to get a decent turbo for a decent price from Shem(thanx to him).It was backfiring with the blues too John.