R33 Popping / Cracking Exhaust Noise.

[skins]

Recently I have noticed a increase in the volume of the popping and sometimes cracking noise from my exhaust when I'm de accelerating. What could cause this? The engine is stock with stock intake it has the usual 3.5 inch exhaust with cannon and a high flow cat. I haven't changed anything on the car but have been told that my oil rings could be stuffed. Would the popping noise increase due to worn rings? Also if your turbo is on it's way out, would this increase the pops?

It used to do it when it was over due for a service then when it got serviced it would go away. Anyone have any ideas? I'm stumped.

[Ethan33GTR]

Yeh funny you mention it becuase my r33 gtr is completly stock down to the exhaust system and occasionally i get a little poping when de-accelerating, never really crackling but.

how does your car perform with the 3.5 inch exhaust sytem on stock internals? only becuase im about to get a system made up but i was gonna go 3 inch? how loud is your system?

[skins]

From inside the car it's not that loud. I run the stock manifold with 4 inch dump and 3.5 system, highflow cat and a drager cannon. I have been told that when you get on it it is a tad rumbly from outside

I was going to put a different cat on it to make it even louder but then you would get that droning noise through the car

Car runs fine. Only draw back is you can't have the car to low because of the zorst. I've been told that it sits higher than most 33's.

[vetter2769]

Its got to do with your exhaust, now that its opened up and is more free-flowing you should notice a slight increase in boost as the turbo is able to flow more freely, and thats why it pops, because now its "out of tune" but the slightest amount. nothings really going to fix it until you get a tune, i.e. nistune or something.

but as to why it actually pops I just assumed is was unburnt fuel, but I'm no expert, just sharing my knowledge.

[Ethan33GTR]

sounds legit, becuase i rang castle hill exhaust and the quoted me $950 for a 3'' Mandrel bent (Mild steel/stainless cannon) with 100cell

hi flow cat. you think this would be suitable for my setup or should i go 3.5 for when i do more work? i just dont want the drone like you mentioned and i dont want to loose back pressure

[skins]

Its got to do with your exhaust, now that its opened up and is more free-flowing you should notice a slight increase in boost as the turbo is able to flow more freely, and thats why it pops, because now its "out of tune" but the slightest amount. nothings really going to fix it until you get a tune, i.e. nistune or something.

but as to why it actually pops I just assumed is was unburnt fuel, but I'm no expert, just sharing my knowledge.

The exhaust was on the car since I bought it and it never used to have this popping issue that bad.

sounds legit, becuase i rang castle hill exhaust and the quoted me $950 for a 3'' Mandrel bent (Mild steel/stainless cannon) with 100cell

hi flow cat. you think this would be suitable for my setup or should i go 3.5 for when i do more work? i just dont want the drone like you mentioned and i dont want to loose back pressure

I'd probably go the 3 inch and then get a decent resonator. That should give you the drone your after.

[zoomzoom]

"i dont want to loose back pressure" and "That should give you the drone your after"

Wait, what?

Anyways, its just unburnt fuel. You could double check using a consult cable. Maybe the "closed throttle" signal isn't working properly when you let off the throttle.

[skins]

If it is the closed throttle signal, how would you check that?

[niZmO_Man]

You most certainly want to lose back pressure, you have a turbo car + you shouldn't be worrying about scavenging effects. Get a 3.5" exhaust with good mufflers (e.g. Magnaflow), you won't have drone issues then. I run a 5Zigen 3.5" cat back (two mufflers), no drone at all and car went harder. Shame the mid muffler cracked and had to replace it with an inferior muffling Xforce one.

Popping and crackling is unburnt fuel in a hot exhaust. When is the last time you changed the spark plugs?

[skins]

A couple of months ago with those iridium plugs.

[zoomzoom]

If it is the closed throttle signal, how would you check that?

The easiest way I can think of is with a consult cable. You can see the signal in realtime or you can create a log over a period of time, ie going for a drive. I think theyre a must for any skyline etc owner who needs to track down a fault.

[PN-Mad]

I'm going to lock in broken exhaust stud/s.

Documented RB25 issue over time. The release in torque on the manifold could have introduced air into the exhaust on over-run, causing the unburnt fuel to ignite with the extra presence of oxygen.

[skins]

Huh?

Do they snap off over time? Is that what you are saying? Or are you saying that they snap when you change the manifold? If this is happening wouldn't I hear a exhaust leak on the manifold itself?

[zoomzoom]

Yes the studs weaken and snap after many years, especially if yours have not been replaced from the factory.

However mine are new and my car still makes little pops and burbles on the overrun. Was particularly noticeable after fitting a new 3 inch exhaust. If you don't notice any issues with fuel consumption I wouldn't be too concerned.

[skins]

I'm getting around 500km's per tank. I got the studs replaced 50,000kms ago. So there would be a exhaust leak at the manifold if they had broken?

[Cassbo]

I'm going to lock in broken exhaust stud/s.

Documented RB25 issue over time. The release in torque on the manifold could have introduced air into the exhaust on over-run, causing the unburnt fuel to ignite with the extra presence of oxygen.

Now that you mention it, my Skyline used to pop on decel even with a standard exhaust. Since replacing the manifold with one without a crack it doesn't pop any more!

[PN-Mad]

I don't doubt that 3inch exhausts pops and carry on at all, but none of that explains why the popping has actually increased over time with no other mods.

You might not hear the exhaust leak on throttle over the exhaust, or it may be a very small leak.

It's just my theory, take it or leave it

Nothing to be all that worried about anyway.

I guess it could be any gasket on the exhaust side too, by this logic.

[skins]

So it could be cracked studs, leaky exhaust gasket or a crack in the manifold?

[niZmO_Man]

Now that you mention it, my Skyline used to pop on decel even with a standard exhaust. Since replacing the manifold with one without a crack it doesn't pop any more!

Now that you've mentioned it, my rear turbo gasket started leaking. I had some good pops.

[skins]

Sounds like my turbo could be shagged.