Need some advice/ opinions

 

I'm trying to quite my zed down, it's currently fitted with 2.5 downpipes and a pg 3" catback (also decat)

 

Bungs in its too loud 103 db, don't even want to know how loud without ( childish but sometimes we need to bring the noise)

 

I'm just about to order the matching 3" labree ultimate downpipes, they are resonated apparently, but suspect it'll get louder,

 

Now, changeing the exhaust is out of the question, but I'm trying to fit a control valve into the system,

 

My first plan was to fit 2 one in each bank, after the h section, just before the mufflers, they are not safe for boosting but for low speeds and idling they are OK as they don't completely shut the exhaust off,

 

But could I run a single valve? just shut one muffler off, after the h? or would this give me pressure problems? I'm right in thinking it would quite it down?

 

I can partially close them to hopefully drop it to track noise levels, and close them more to not make so much noise getting home.

IMO you are attempting to treat the symptoms instead of addressing the root cause of the problem.

In engineering terms that is never going to produce a correct answer.

 

The root cause of the excessive noise is having the wrong/poorly designed exhaust on the car.

 

Tinkering about with bungs and valves is like putting an Elastoplast on a broken limb.

 

changeing the exhaust is out of the question

 

IMO changing/redsigning the exhaust is the best way to a long term result that will allow you to get out on track and drive on the road at an acceptable level of noise.

 

All of course IMHO

Thanks Pete

 

Worried someone would say that, it's brand new I imported it a few months ago... Was told when paired with the labree pipes it's the best performance exhuast available. Hadn't really thought about noise....

 

The labree pipes are resonated, maybe if I replaced the decat pipes with resonators too it'd bring it down, I really want to keep the 3" system for when I eventually get bigger turbos etc...

. Was told when paired with the labree pipes it's the best performance exhuast available

 

Who told you that then??

The person selling it to you?

Someone constantly tells me on the TV that their lager is probably the best in the world but I dont like the taste .. I prefer my SanMiguel. Im sure you get the drift of what Im saying.

I dont think our American friends are troubled much by the anti car/noise/pollution tree huggers that populate these isles.

 

Anyway I digress...

It may be the best exhaust system in the world but if you cant get on track with it and you personally cant live with the long term road noise then its not the best for you.

Perhaps splicing in some cherry bomb type silencers or resonators in the decats is a good place to start? I dont know personally as the technical aspects of turbo exhausts and tuning are not in my (limited) database of automotive knowledge.

Finding a balance between power, noise limits and driveability isnt easy and different cars/drivers will need different solutions.

There are no definitive guides to 300ZX building as you are finding out. Welcome to an expensive world of trial and error.

Fair point, probably means the labree pipes aren't as good either, maybe I'll see if someone can build me a better system once I've some spare money

 

I've only got lwb exhuasts in my lock up,

I'm starting to think maybe I'd have been better getting a 2.5" system...

 

Does anyone know at what point the 3" is necessary. Assuming until I upgrade my turbos it's probably costing me power,

 

I wonder if restricting the exhaust would actually help at lower Rpm, maybe hooking the valves up to an old actuator so it opens with boost? Anyone know how they do it on the corvette s etc?