Hey guys, iv finally been forced to make my FD legal. (got pulled over with a bunch of mods that need to be "certified")
It got ordered off the road by the cops, now i get in heaps of trouble if i get caught driving it on the road again..so im now driving a crappy red holden barina (nicknamed the granny pod)

Anyway, one of the last things I need to do till im all legal is quieten down my exhaust.
Currently it tested at 104db at about 4k rpm, and I need to get it down to about 94db..

Im not sure what route to go, I see a second hand Kakimoto Racing muffler for pretty cheap locally ($295 NZD) but really dont know if this will give me any improvement.(pic below). was even thinking it might be the way to go to just buy this then if its still too lound modify the Kakimoto (insted of my current one)


Currently my exhaust is basically 3" straight through with a couple of resonators in there and no actual muffler as such.

I dont know if i should bite the bullet and just take it to an actual muffer shop, or take the chance and buy the Kakimoto even though it may not pass my inspection. But then i was also thinking if it did fail i could probably weld a resonator from my current exhaust into the new one to make it pass...thoughts?

yea, so anyone got the exhaust pictured? how loud is it?
Is it worth getting the Kakimoto even thought it may/will probably still fail or should i just mess with my current exhaust?

 

Can't you just get a silencer for your current exhaust?

 

Depends what you mean by silencer, i dont think its allowed to be easily removable and whatever i have i want it to be straight through. I also dont want to loose any power lol...yea alot of demands i know.
I dont want a big barrel muffler thing on the back of my car either, and i like my flames.
Im currently leaning towards just buying another resonator and welding that into my current exhaust and seeing how i go. If its not enough its only a few $ spent i guess, as i dont have to repay inspection costs..

 

You might try checking with the guys over at fdrx7 (NZ/AUS area) to see what works best. Or PM a member here named GOMEZ. He might have some suggestions.

 

try to get a silencer. this is should be legal even if it's removable (it is in germany). those are also cheap. after you passed your technical inspection just remove it and keep it for the next time.

 

A lot of resonators/silencers are filled with fiberglass packing. The rotary exhaust is so hot that it melts the fiberglass. At that point, your silencer becomes a straight thru pipe with no silencing effect. Its possible that your current resonator is doing nothing.

 

This.

If you're in Auckland, check out Woolf mufflers in Mt Eden and get one of their stainless packed boiler muffers and a stainless packed resonator or 2.
Knowing Jap Spares prices, it'll work out heaps cheaper, and should be a lot quieter.

Woolf fab'd a 4" inlet/5" outlet oval muffler for my FD and run a single resonator and passed my cert easily.

 

My car came with a funnel like peace of metal that could be put in the end of the exhaust. It made a noticeable difference. It's removable of course.

 

yep im in auckland, im taking tomorrow off work to try get it sorted. might pay a visit to those woolf guys, thanks

 

Might be too far being here in the States but the rx7store.net midpipe has a muffler built in which dramatically reduces the noise level:

http://www.rx7store.net/product_p/resmidpipefd3s.htm

I have one on my 20B and it did the trick. A lot of guys will weld a Magnaflow or Borla muffler in the midpipe as well.

 

you should try out SMB - very quiet and flows really well. I had a resonated midpipe, then switch to their metal cat, did a before and after dyno run just to get numbers for comparison. With the metal cat, I didn't even loose any HP.

smb metal cat, with dual tip exhaust = very clean set up.

http://www.smb.net.au/fullexhaustsystems-mazdarx7.htm

 

+1

SMB in in Oz and they have some very high quality exhaust pieces. Not sure you'll pass emissions with their metal cat though. That will depend on your local standards. I run their mid pipe with a metal cat and a resonator and the Racing Beat cat back exhaust. The car is reasonably quiet but will hit 96-97db at the top of third gear running up the hill to the Corkscrew at Laguna Seca at full throttle. It should be OK at ~4k rpm.

 

we dont have emissions tests here, well only noise emmissions(and only if a cop decides he thinks your car is too loud!) so im thankful for that

An update, i went to several local muffler shops who really didnt want anything to do with it or wanted to charge me insane amounts.
Im not supposed to be driving it which limited the amount of places i was game to drive to, so i decided to just take it into rx7heaven as they are local and well, theyll know what to do
Dropped my car in there this morning and am picking it up this afternoon.
Im getting two new better resonators fitted in hopes that will be enough to get me to pass, and if not then they are going to fit a can on there aswell.
Now im kinda excited to get her back and see how she sounds!

 

picked up my car, looks and sounds sweet as.
not as obnoxious at idle but still sounds good and grunty under throttle.
ended up with 1 resonator and a round trust muffler.

 

Little late on this one, but here's some input -

I have one of those Kakimoto Racing cat-backs (not on the car, just in the collection ) and it's VERY quiet. That quite likely would have helped out a great deal.

If you're sequential, that helps a LOT. Non-sequential is just loud.

You can also get an Apexi ECV, search for my writeup on it. Pull a lever in the interior, the car is WHISPER quiet. No power, but SUPER quiet.

Dale

 

Racing beat cat-back. . .some might consider it expensive, very nice piece and incredibly quiet, but a nice tone to it. . .very clean as well. . .

 

Weeellll, I failed my noise test again.
Infact I somehow managed to make even more noise then last time! 107db @ 4825rpm.
it sure sounds quieter then before, especially at idle but obviously the noise testing equipment dosent like something about it.
Iv now going to go the route that i didnt want to go and throw stuff in there that i will remove later..(hopefully i can just secure the silencer with bolts and dont have to spot weld it in and drill it out again)

Im also thinking about getting my mate to make up some reducing plates on his cnc to go in between the flanges on the exhaust sections to ensure theres no chance I fail. Im getting sick of going back and fourth. The plates will be removed after completion of the noise test.
Can anyone see any problems with using reducing plates? Are they dangerous? Will they make my car quieter? (i figure they will after reading the review on that apexi thing)
Im thinking I will put two plates in there with only a 1inch hole or something and use a silencer also..think that will get the noise down!? or is that too much?

 

What about a Spun highflow cat?


http://www.jegs.com/i/Magnaflow/642/...oductId=763223 <-- 3 inch 75 dollars

or are cats just bad period?

 

^im trying to get away without having anything else parmanent welded into the system.
I like it how it is now, i just want to make it pass the test - then put it back to how it currently is.

 

http://enderw88.wordpress.com/2009/1...istry-inserts/

I used this on a custom exhaust a few years ago and I believe it reduced the noise level a lot. You can find bunches of info about these and cone type silences (mostly used in open headers to pass decibel levels restriction.) Also the amount of back pressure you'll gain will be negligible.

It can be tack welded in place and removed rather easily.

 

Or you could try something like this:
http://www.supertrapp.com/product_se...t.asp?CatID=27

Tunable and removable.

 

https://www.rx7club.com/showthread.p...ight=apexi+ecv -- apexi ecv might be the solution to your problem.

 

I have finally passed my noise test!
I ended up making a plate that goes in between one of my exhaust flanges.
Its basically just a piece of stainless steel that has been cut into the shape of a 3inch exhaust pipe flange with about 8 x 10mm holes drilled in it to restrict the exhaust.
I also put a simple removeable silencer in the tailpipe.(turns out it didnt need to be welded in, it just cant be removed without the use of hand tools! so a single allen head socket screw holds it in )
The restrictor plate + tail pipe silencer bought the noise down from 107db to about 93.5db so a huge reduction!
Car is quite gutless at the moment though, im going to remove the restrictions sometime very soon.
The good thing is this fix was free! and easily removeable! yay!

 

Wait I don't understand. So you put a restrictive piece in the exhaust to pass the test knowing it will hurt performance and it can only be taken out with tools?

Why did you go through all that?

You should've just bought an FD stock catback, which is cheap, pass the test, then install something permanent that wont give you future problems with the cops.

Ie: dale clark's writeup, kakimoto exhaust, racing beat etc.

 

^i dont think you quite understand our rules / certification process. Kind of a long post but you need to read it to understand why i would do this..

Anyway the rules state that an exhaust piece cannot be "easily removeable".
"easily removeable" according to the regulations means that it cannot be removed without the use of at least "hand tools".

My car needed to pass the noise test to be allowed back on the road - no matter what exhaust system I use.
Whatever exhaust system i pass the test with gets "certified" and gets a tag attached to it, and a diagram is drawn of all the exhaust components / measurements. (they do not take the exhaust to apart)

Now - we have to have basic vehicle check called a "warrent of fitness" every 6 months - and the car will only pass the 6 monthy check with whatever exhaust i get it "certified with"

So you see - if I got it certified for a stock exhaust im stuck with that - which i obviously dont want. And it would be stupid to get it certified with the stock exhaust then swap it out after my check for the free flowing exhaust because then im elibible to get in trouble if pulled over and im back at square 1.
As long as my exhaust has the "certified" tag on it and all VISIBLE exhaust components are there - it does not get tested again at the 6 monthy checks.

The catch here is the restriction plate is invisible -i.e you cannot see it between the flange(just appears to be a gasket), and so it cannot be drawn into the exhaust diagram.
This means once the exhaust is tagged/stamped - i can remove the invisible plates and i now have a certified exhaust that is free flowing. Albiet too loud again, but no more checks.

The only possible thing i may need to do to pass the 6 monthy check is install the tailpipe silencer which is 1 single allen head bolt to attach/remove...(because its visible and so drawn into the diagram)

Understand?

I will probably never need the restiction plate again. And its going to take me all of 10 minutes to remove it...and my exhaust has that wonderful "certified" tag on it.
Also - I wouldent think it was a big deal (especially for an FD owner) to jack up one side of the car - undo two bolts, slide a plate in there then put the two bolts back or vise versa.