Sports Exhaust - Machine Gun Noise?

[pdavison]

I have a speed six Cerb with a sports exhaust and at around 2,700 revs once warm (in every gear) it sounds like a machine gun with consistant bangs happening quite close together.

Don't get me wrong this does prove very entertaining, but I want to find out if anyone elses does something similar.

Also, will it be causing any damage ?

[j_s_g]

pdavison said:

I have a speed six Cerb with a sports exhaust and at around 2,700 revs once warm (in every gear) it sounds like a machine gun with consistant bangs happening quite close together. Don't get me wrong this does prove very entertaining, but I want to find out if anyone elses does something similar. Also, will it be causing any damage ?

If this is just on the overrun (when you lift off the throttle), then "they all do that, sir". If it's when you're accelerating, I'd be a bit more worried. If your car's still got cats fitted, it won't be helping prolong their life, anything else'll depend on what's causing it (i.e. when it happens)

[andy4200]

They all do that sir!!!!

Mine has sports pipes and decat and is rather loud. j_s_g and a few others from the Boxing Day run will probably confirm that.

James is right though, if it's accelerating then I would be worried but if it's on lift off then get the window down and enjoy (and frighten a few grannies as well)....

[Rappa]

If you want to know the full blubrb etc. i.e the gap left at top dead centre and the dynamic cavitation propities of the engine and hence the travel of unburnt fuel to the hot exhaust, then vist theratpac.com and go to FAQ. If you don't want the noise then dip the clutch.

[pdavison]

The overrun noise is great, but this is when you hold a steady speed in any gear at just under 3k revs. It doesn't happen when you accelerate, just when you holding the throttle at one position.

[satman]

Mine doesnt do that, but i would guess that at that RPM the engine could be overfuelling and excess fuel burning in the exhaust manifold on its way out!....not sure if this will do the cats any good though!....go faster! (more rpm = no problem!)

[Habib]

Maybe one to check is that the exhaust is not banging on the chasis anywhere. I have had that on another car, not the cerbie and it sounded like a machine gun. Wiggle the exhaust stongly next time you get a chance. Also worth looking under the car whilst someone else revs it up. You may be able to see where exactly the noise is coming from (front or back of exhaust). When inside the car, it is not easy to ditinguish between a noisy/loose CAT or a rattle somewhere else in the exhaust.

[munir]

pdavison said:

I have a speed six Cerb with a sports exhaust and at around 2,700 revs once warm (in every gear) it sounds like a machine gun with consistant bangs happening quite close together. Don't get me wrong this does prove very entertaining, but I want to find out if anyone elses does something similar. Also, will it be causing any damage ?

It is a real asset.

[j_s_g]

pdavison said:

The overrun noise is great, but this is when you hold a steady speed in any gear at just under 3k revs. It doesn't happen when you accelerate, just when you holding the throttle at one position.

I never get it when accelerating, but when holding at around 3k RPM on the motorway in 5th I used to get a few pops and bangs when I first got the car. It felt like it was being overfuelled anyway, so I had the lambda sensors replaced, and the "problem" has gone away. Could be as satman says. Then again, as the S6 engine is quite different to the AJP, you might want to ask the Tuscan owners if theirs are the same?

[dannylt]

Pops and bangs are generally weak mixture, not strong. Sounds more like it was misfiring - dodgy HT leads and/or coil packs give this effect. I had a single HT lead go after the Red Rose conversion and was very worried for a 100 miles or so!

[pdavison]

I will check the HT leads, but I have found that the drivers side exhaust is knocking on the bodywork somewhere.

I will try to see if I can find out why, but without a pit that maybe harder than I think!

[andy4200]

pdavison said:

I have found that the drivers side exhaust is knocking on the bodywork somewhere.

Don't know if it will help but mine was knocking and when I got under it I found that one of the cats had no bolts holding it to the manifold side of the exhaust.

Couple of bolts and a decat later and all was fine.

Andy

[burriana500]

andy4200 said:

Mine has sports pipes and decat and is rather loud. j_s_g and a few others from the Boxing Day run will probably confirm that.

That's not a machine gun Sir.. it's a feckin flame thrower!

[andy4200]

burriana500 said:

andy4200 said: Mine has sports pipes and decat and is rather loud. j_s_g and a few others from the Boxing Day run will probably confirm that. That's not a machine gun Sir.. it's a feckin flame thrower!

You're just jealous aren't you

[j_s_g]

andy4200 said:

burriana500 said: andy4200 said: Mine has sports pipes and decat and is rather loud. j_s_g and a few others from the Boxing Day run will probably confirm that. That's not a machine gun Sir.. it's a feckin flame thrower! You're just jealous aren't you

To be honest, we've had scarier rear-views of Al than flames coming out!

[andy4200]

Too true, I saw the picture on PH a couple of weeks ago