Help Moving Restriction From Rear Cannon!

[Harey]

Hi,

I was reading through some of the other exhaust threads and thought I would check my own fujitsubo catback exhaust on my R34 GTT. It seems I have one too!! Looks to run for about 4-6 inches from where the rear of the muffler starts and then after that it just looks like normal 3" muffler honeycomb sidewalls. The restriction is quite severe and looks to be around 2.5".

Boostn0199 mentions a bit in this thread with a few pics:

http://www.skylinesaustralia.com/forums/topic/339046-opinion-on-kakimoto-regu-06/page__hl__silencer+weld__st__20

He mentions the use of a mini air grinder. I have never seen one of those nor do I have access to one. Any ideas on how to remove it? It looks terribly restrictive.

Pics below are looking into the tip of the exhaust.

[scotty nm35]

Can you get your hand in there? I have a die grinder you can use, it will make it louder though, it acts as a resonator.

[Harey]

Yeah you can get your hand in there. Its 5" until the first restriction to 3" and then another restriction to 2.5".

Yeah I am happy for it to be louder. I really want the flow of a full 3" exhaust, if its too loud then I will have to get another exhaust or muffler.

[chiksluvit]

the restrictor might be what capped your max power..

[scotty nm35]

2.5 inch, I would say so. PM me for my details if you like Jeff.

[ARTZ]

just had a look in mine cause its a fujitsibo too and had same restrictor, though it is about 70-75mm so about 3inch anyway, which is good for at least 300kw it seems, so dont think its a problem in my case..rest of my system is 90mm so a small restriction at the end shouldn,t upset it any more than the cat would

stick your hand in there Jeff until it touches the sides then measure across your hand how wide it is..if your exhaust is 90mm (3.5 inch) id say its at least 70mm at the restrictor which should flow plenty for your power mate it may not be worth the effort..

[Harey]

the restrictor might be what capped your max power..

Trent at Status did a test for me without the catback and then without the cat. Just without the catback lost between 5-8 rwkw although my cat looks to be restrictive as well. So the cat might be reducing the amount the restrictor is holding power back.

We also confirmed that the intercooler is the worst restriction. See the way the boost before the intercooler holds steady but the pressure after the intercooler drops away considerably. I have just purchased a better turnflow intercooler so will fit that very shortly. I would like to sort out both this restrictor and the cat and then go in for a retune and then E85

[Harey]

just had a look in mine cause its a fujitsibo too and had same restrictor, though it is about 70-75mm so about 3inch anyway, which is good for at least 300kw it seems, so dont think its a problem in my case..rest of my system is 90mm so a small restriction at the end shouldn,t upset it any more than the cat would

stick your hand in there Jeff until it touches the sides then measure across your hand how wide it is..if your exhaust is 90mm (3.5 inch) id say its at least 70mm at the restrictor which should flow plenty for your power mate it may not be worth the effort..

Just stuck my hand in there then and its no bigger than 2.5". Measured to ~60mm. My exhaust is based off a 3" exhaust not 3.5". I definitely think its worth it.

[ARTZ]

yeah understandable 65mm is 2.5 inch so its way off

damn nearly 5psi drop through the cooler..

whats pressure WG do you have, or is it EBC .

might have to rig a nipple up in mine for curiosity sake..

[SiR_RB]

such a nice exhaust and they go putting these silencers in it, if its too loud, maybe the factory should of added another resonator/and or a bigger one :S

[Harey]

yeah understandable 65mm is 2.5 inch so its way off

damn nearly 5psi drop through the cooler..

whats pressure WG do you have, or is it EBC .

might have to rig a nipple up in mine for curiosity sake..

Just running off the wastegate pressue. The pressure drop includes all intercooler piping. So from a nipple that I installed on the hot pipe from the turbo to the intercooler then the other side is measured by the boost pressure in the manifold.

Trent said he wasnt necessarily looking for the pressure drop but more the shape. If both shapes are the same then the cooler is most likely working ok where as if the pressure drops off after the cooler then there is a restriction. And yeah from the dyno sheet above there is a serious restriction!!

[Harey]

such a nice exhaust and they go putting these silencers in it, if its too loud, maybe the factory should of added another resonator/and or a bigger one :S

Exactly why not just put bigger/better mufflers that still flow well. Its not like their cheap!

[eron]

Honestly, removing that restriction might net you a few KW on top, but it will be louder, and you might lose some low down KW.

Edited June 26, 2011 by eron

[ARTZ]

yeah the turbo seems to hold boost well from 3-6k

so which nipple does the WG run off, the manifold one or the hot pipe one..

do you know if its a 20psi actuator..

[Harey]

Honestly, removing that restriction might net you a few KW on top, but it will be louder, and you might lose some low down KW.

Nope exhausts after turbos are different. Bigger is better everywhere in the rev range. Better flowing exhaust only has the potential to reduce lag.

Whats the point in a 3" exhaust when it reduces to 2.5" in one location, might as well have a 2.5" exhaust.

[RRob]

Had a Stagea on the dyno recent that went from 630hp to 720hp by unbolting the rear muffler. Looked about 2" I.D.

[Harey]

yeah the turbo seems to hold boost well from 3-6k

so which nipple does the WG run off, the manifold one or the hot pipe one..

do you know if its a 20psi actuator..

The wastegate runs off the hot pipe just like the factory setup.

Its a hypergear actuator, not sure what its official rating is.

[tridentt150v]

Is the restriction s/s? Make it harder to cut out of it is, s/s is a pain.

[ARTZ]

Whats the point in a 3" exhaust when it reduces to 2.5" in one location, might as well have a 2.5" exhaust.

yes and no..having a big exhaust with a small end wouldnt be as bad as your whole system to small..If The whole pipe has time to fill up with exhaust gas, then by the time it has to force through the restriction at the end your revs and therefor pressure is up to push it through..it could no doubt cap your top end somewhat though

The wastegate runs off the hot pipe just like the factory setup.

Its a hypergear actuator, not sure what its official rating is.

Doesnt the factory WG run off the intake pipe? I cant remember but mine is connected to the inlet manifold now..u think would it be any better off the hot pipe?

Is the restriction s/s? Make it harder to cut out of it is, s/s is a pain.

yeah i think a new muffler would be an eaiser way to go about it..I looked at mine today and thought stuff that

[mad082]

Trent at Status did a test for me without the catback and then without the cat. Just without the catback lost between 5-8 rwkw although my cat looks to be restrictive as well. So the cat might be reducing the amount the restrictor is holding power back.

We also confirmed that the intercooler is the worst restriction. See the way the boost before the intercooler holds steady but the pressure after the intercooler drops away considerably. I have just purchased a better turnflow intercooler so will fit that very shortly. I would like to sort out both this restrictor and the cat and then go in for a retune and then E85

looking at the graph, i'd say that only a small percentage of the difference in pressure is due to restriction in the intercooler. the reason being that as airflow increases both the before and after pressure decreases at roughly the same rate. if it was a restriction the pressure before the turbo should increase while the pressure after it should decrease reletive to each other. you have to remember that the pressure after the intercooler will always be less than before the intercooler due to cooler air being more dense. depending on your before and after temps this could account for up to 10% of the drop you are seeing, and would defininately account for between 5 to 7% of the drop.

oh and FYI, the stock setup actually runs the wastegate off the cold pipe. when i put my fmic on i cut the stock nipple off and welded it onto the hot pipe. this made it hold boost much more stable. was getting spiking with it running off the bov line.