Noob question re exhaust popping

[dbvw]

With the risk of sounding like a complete mechanical idiot I have a question. Can someone explain the reason for exhaust popping on deacceleration ? Ihave a Saggy and if I let the engine break from 4k-2krpm there are a few pops on the way down. Is this normal ? Sounds quite cool but what is the reason behind these pops ? Can someone please confirm if it needs to be looked at.

Thanks
Darren

[sidewayz]

Perfectly normal and one of the small pleasures of driving a TVR. It's just unburnt fuel igniteing and nothing to worry about.
In fact,onece the exhaust is nice and toasty if you back off after a accelerating hard it will make all sorts of entertaining pops's .
(Don't back off too quickly untill you are more used to the cars performance, don't want ot to be too exciting do we!!)

[broadside]

Basically it is unburnt fuel igniting in the pipes. The big "Flapper" Injection engines on the Wedges are brilliant at this, 390,400, 450 SE. With the advent of hotwire injection which cut off fuel on the over run the banging and popping is stopped. With modern TVRs with hotwire injection systems the programable ECU's can have this feature programmed into them to still deliver fuel on the overrun thereby giving you the pops and bangs and flames too if you want!!

[jagdpanther]

Is it normal??? IS IT NORMAL????????

It's one of the main reasons for people buying TVR's

Don't worry....it's orgasm in the key of G*

[mightymouse]

broadside said:

Basically it is unburnt fuel igniting in the pipes. The big "Flapper" Injection engines on the Wedges are brilliant at this, 390,400, 450 SE.

Yup my 350i does it as standard

[z_chromozone]

broadside said:

Basically it is unburnt fuel igniting in the pipes. The big "Flapper" Injection engines on the Wedges are brilliant at this, 390,400, 450 SE. With the advent of hotwire injection which cut off fuel on the over run the banging and popping is stopped. With modern TVRs with hotwire injection systems the programable ECU's can have this feature programmed into them to still deliver fuel on the overrun thereby giving you the pops and bangs and flames too if you want!!

My V8S is hotwire and still does this with a factory standard ecu, hotwires still fuel on the overrun.

Z

[RichB]

z_chromozone said:

broadside said:

Basically it is unburnt fuel igniting in the pipes. The big "Flapper" Injection engines on the Wedges are brilliant at this, 390,400, 450 SE. With the advent of hotwire injection which cut off fuel on the over run the banging and popping is stopped. With modern TVRs with hotwire injection systems the programable ECU's can have this feature programmed into them to still deliver fuel on the overrun thereby giving you the pops and bangs and flames too if you want!!

My V8S is hotwire and still does this with a factory standard ecu, hotwires still fuel on the overrun.

Z

Yeah so do most Griff 500's but I didn't want to tell the chap he's wrong for fear of starting yet another Pistonheads slanging match! But now you've said it so will I...

[dbvw]

jagdpanther said:

Is it normal??? IS IT NORMAL????????

It's one of the main reasons for people buying TVR's

Don't worry....it's orgasm in the key of G*

LOL. ^

Thanks for the replies. Im still a bit cautious with any sounds at the moment so good to know this is normal.

Flames ? out of the side facing exhausts. That would be interesting.



Now if you lot wouldnt mind I have just one more niggling question. After driving both before and after the car is warmed up there is a slight dip in revs when i press the accelerator from stationary.

for example. Oil temp 60ish. At the lights, revs 850 rpms, as i press the accelerator the revs dip to almost stall so i have to overrev a little before lifting the clutch.

Normal ? or should that be a little easier.

This is not all the time but quite common and I have stalled when turning into my drive at a very slow speed.

And no im confident this is not driver error..

[KillerJim]

jagdpanther said:

Is it normal??? IS IT NORMAL????????

It's one of the main reasons for people buying TVR's

Don't worry....it's orgasm in the key of G*

This is the 2nd reason I bought a Sagaris, the first being the looks

Weird how the performance is only 3rd on my sheet :P

J

[KillerJim]

dbvw said:

Now if you lot wouldnt mind I have just one more niggling question. After driving both before and after the car is warmed up there is a slight dip in revs when i press the accelerator from stationary.

for example. Oil temp 60ish. At the lights, revs 850 rpms, as i press the accelerator the revs dip to almost stall so i have to overrev a little before lifting the clutch.

Your car needs the throttles balanced, I recently fubar-ed the throttle balance on the Sag and had the servicer set it up again. He slightly missed it - I noticed that when she gets warm that she`ll want to stall when pressing the throttle slightly, you keep depressing until she rev's to about 1700rpm - so you can`t really get to the 1000rpm->1500rpm *sometimes*

If your idle is below 750rpm on hot (i.e oil 70c) and she stalls when air-con is on (at idle) she needs the idle adjusted too.

J

[dbvw]

KillerJim said:

dbvw said:

Now if you lot wouldnt mind I have just one more niggling question. After driving both before and after the car is warmed up there is a slight dip in revs when i press the accelerator from stationary.

for example. Oil temp 60ish. At the lights, revs 850 rpms, as i press the accelerator the revs dip to almost stall so i have to overrev a little before lifting the clutch.

Your car needs the throttles balanced, I recently fubar-ed the throttle balance on the Sag and had the servicer set it up again. He slightly missed it - I noticed that when she gets warm that she`ll want to stall when pressing the throttle slightly, you keep depressing until she rev's to about 1700rpm - so you can`t really get to the 1000rpm->1500rpm *sometimes*

If your idle is below 750rpm on hot (i.e oil 70c) and she stalls when air-con is on (at idle) she needs the idle adjusted too.

J

thats exactly what i have. the lack of 1000rpm-1500rpm sounds spot on when sometimes pulling away.

Thanks a lot. Will take it in to get tweaked.

[jagdpanther]

KillerJim said:

jagdpanther said:

Is it normal??? IS IT NORMAL????????

It's one of the main reasons for people buying TVR's

Don't worry....it's orgasm in the key of G*

This is the 2nd reason I bought a Sagaris, the first being the looks

Weird how the performance is only 3rd on my sheet :P

J

Can't argue with that, I would love a Saggyu if I could afford one

Main reason sound, second reason looks/presence, third reason performance fourth reason exclusivity

[RichB]

KillerJim said:

dbvw said:

Now if you lot wouldnt mind I have just one more niggling question. After driving both before and after the car is warmed up there is a slight dip in revs when i press the accelerator from stationary.

for example. Oil temp 60ish. At the lights, revs 850 rpms, as i press the accelerator the revs dip to almost stall so i have to overrev a little before lifting the clutch.

Your car needs the throttles balanced, I recently fubar-ed the throttle balance on the Sag and had the servicer set it up again. He slightly missed it - I noticed that when she gets warm that she`ll want to stall when pressing the throttle slightly, you keep depressing until she rev's to about 1700rpm - so you can`t really get to the 1000rpm->1500rpm *sometimes*

If your idle is below 750rpm on hot (i.e oil 70c) and she stalls when air-con is on (at idle) she needs the idle adjusted too.

J

a friend of mine had a Sagaris and it had the "won't idle when the air-cons on" problem...

[so called]

Nice looking Sagy Darren.