Restriction In The Exhaust

[rondofj]

Xforce oval muffler

[butterfly effect]

If there is a problem with the muffler or resonator a restriction point can sometimes be indicated by heat marks , brown usually. The only accurate way to find the culprit is to pressure test the system on load. The starting point is engine side of cat. The reading is the summation of all restriction in the exhaust.Repeat this process in front of the remaining components. Where the pressure drops indicates that closest component towards the engine is the culprit. If there is no pressure drop , remains high then it will be the rear muffler.

[XKLABA]

Have you got a dyno graph, HP v boost

The angle and location of where the WG rejoins the exhaust is less then ideal IMO, it should have been put into the back of the bend at a less angle

If the cat is 100 cell 5" bodied and intact it shouldn't be a problem

They should have dropped it to confirm, I'd agree on the CAS been a possible problem as already stated

[rondofj]

Dyno Graphs

Current one with Power FC and previous one with Nistune a year ago

[rondofj]

Boostdrop towards top end is 2psi in both graphs- expected as I use a Turbosmart T manual boost controller

[Dale FZ1]

If the cat core is intact it should be ok.

The WG merge point could have been a little better, and angled a bit more shallow. But it doesn't look too bad.

Offset mufflers - depending on internal construction - can provide bigger restriction. Some simply use a slight kink with a full length internal perforated tube. They are little different to one that has a straight internal tube. If yours runs bulkheads and chambers then yes it could be an issue.

That mid muffler definitely needs another look, the rear outlet seems to be necked down. Get that measured and be prepared to modify/replace/delete it.

[rondofj]

Thanks guys I have doubts on the mid muffler as well as its seemingly necked down at the back, unsure about front, will check. Is it a stock item, and if replacement needed then just get a generic 3' in/out mid muffler right? What about the xforce rear oval muffler, anyone here made 310+rwkw on that? Confirming that cat is intact, was dropped last week

[scotty nm35]

Unless there is something we can't see, like a piece of metal welded poorly inside the exhaust, it won't be your issue. We can debate it as much as you like Ron, but you could have dropped 2 bolts, seriously less than a minute, and you would have known if it was a problem or not on the dyno. There are a few issues that can limit power like that and jumping to conclusions won't fix any of them.

Get it back on the dyno, (make sure you have the cam timing checked first) drop the exhaust during the run, if that fails change the cas on the spot.

[rondofj]

Thanx Scotty - its goin back Monday for a quick check with Yavuz, will ask them why they didnt drop the exhaust seeing as the conclusion was made that its definitely the exhaust. Cam timing as set by me with timing gun and confirmed by Mark is spot on 15degs at idle and also on PFC. I took cat off last week to hammer out some welding dags where the flanges welded to the cat. Hope I havent shattered out the innards with the heavy hammer/screwdriver blows to thedags.. ;S.

Where is the thread about Anthonys CAS on the R34GTT, couldnt find the link, if you dont mind posting here? Would like to read cheers

[AngryRB]

Thanks guys I have doubts on the mid muffler as well as its seemingly necked down at the back, unsure about front, will check. Is it a stock item, and if replacement needed then just get a generic 3' in/out mid muffler right? What about the xforce rear oval muffler, anyone here made 310+rwkw on that? Confirming that cat is intact, was dropped last week

I used a 3inch xforce rear oval muffler for 320 easy kw's, doesn't look as nice as your one though. Can take a pic of the insides to compare if you want.

[rondofj]

Updates on exhaust study: discovered theres a taper at where the rear exhaust pipe joins with back of mid muffler. Exhaust confirmed 77mm outer dia (3 inch), that taper is 69mm (2.71inches) XForce rear muffler is fine, seems to have an angled inner pipe to offset at back entry. - inner dia looks small? !

[rondofj]

Ey Angry RB yes would be good if you can, thanks..! You can see mine above- just posted

[rondofj]

Last pic I hope- back of xforce rear muffler- 3 inch joint

[wolverine]

I have a cannon rear muffler sitting here in the Hills if you want something that is guaranteed 3"

Have you had a look at the overheating issues as well?

[Blackkers]

I've got the same rear muffler. made 306kw but no restriction was noted whatsoever and it holds boost without too much trouble.

[discopotato03]

I think there's a bit more to these Japanese cat back mid mufflers than meets the eye . They're more difficult to see on the car let alone look through and Jasma systems were made to be quiet . If your bolt on import only got modest upgrades some restriction may not have been a big issue . There are limits to how deep that mid muffler can be and from memory there is a bracket bolted across the tunnel in a 33 anyway that limits the length of that mid muffler . The numbers I wrote down are 5 x 10 x 16 inch and that's a Nismo in cat back one - no idea what it's like inside .

I spoke to Wolverine about this stuff yesterday evening and it's beginning to sound like the best mufflers need to be made because the generic ones are too big or too small .

The rear ones like that Xforce could be slightly longer and deeper for Skylines but they're obviously intended to go into other cars with a little less space - so one fits all .

The best scenario would be a run of the biggest straight through mufflers that will fit 32 33 34 made up and a group buy , 3 and 3 1/2" would keep most inc the GTR people happy if quiet .

A .

[XKLABA]

I find that magnaflow make a good center muffler that fits nice and neat and is in 3,3.5 and 4" sizes

I modified a HKS super drager rear muffler to make it 4" cause it has a big arse barrel around it meaning there was heaps of room for sound deadining around the 4" pipe

At these power levels custom is the best way to get the flow and keep sound to a minimum

[Dale FZ1]

Ron your pics on post 31 pretty clearly show the neck-down restriction, pics 3 and 4.

If pic 4 is the rear muffler, the guts of that thing must be somewhere around 2.25". There's the source of your problem Unigroup identified.

Adrian the best/biggest mufflers may well have to be made, but there are decent off the shelf units around provided you look.

There's not much bling factor with Hurricane or Mercury products, but they offer sizes and shapes that can fit and provide decent flow and muffling ability.

[rondofj]

Na Wolverine, I had a HKS cannon before, got rid of it, I much like my quiet oval, just hope its not a restriction, Blackkers do you mind taking a pic up inside your muffler tip like I did above, I want to see how big your hole is cos mine looks small lol..

Do you guys not think my mid-muffler could be the culprit with that tapered 2.71inch exit at the back?

[rondofj]

Oops your post didnt come through until after I posted, Dale, yehthe guts of that thing looks small aye .. I ordered a 3' oval xforce supplied n fitted by Western Mufflers in Fairfield coupla years ago and thought thats what I got, doesnt look like it now..wtf