Exhaust Crash Course for Dummies

RaYmO · Postby **RaYmO** » Sun May 06, 2007 1:27 pm

Hi Guys,

Been tickling the idea of upgrading my stock exhaust for my NA6 and had performed searches on this forum which had raised more questions than answers.

Where do I start?

1) What are the different (road worthy) exhaust set ups available (I see terms such as straight, cat-back etc to describe setups but have little idea what they are)

2) Headers/Extractors - Stainless steel seems the way to go, but there are also different setups (4-2-1 vs the standard 4-1) what's the pro's/con's of each setup? Which version will have the least amount of \"back-pressure\" by design?

3) Muffler - performs sound deadening on the exhaust (gotta get one of these) but what is the adverse affect on performance if the wrong muffler is installed?

4) Is it possible for the above exhaust upgrade to be compatible with a turbo upgrade in the future or will I have to rip and replace?

I'm kind of learning as I go so if anyone is able to list experience with exhaust/header setups/manufacturer brands etc it will be a great point of reference in my exhaust upgrade.

I need more Powa for my NA6!

Thanks in advance guys.

adamjp · Postby **adamjp** » Sun May 06, 2007 3:31 pm

Read this link.

1) Must have a Catalytic converter that works. Otherwise your only consideration is noise output. Cat back is catalytic converter to exhaust tip, normally retaining your old catalytic converter.

2a) Stainless is A way to go, but not particularly superior if you choose to go ceramic coated (Jet-Hot or HPC). These coatings reduce the under bonnet temperatures spectacularly and are well worth the extra $$.

2b) 4-2-1 is common and theoretically delivers efficiencies across the rpm range. 4-1 is less common and will deliver efficiencies in a more targeted rpm band. I would go 4-1 if you are looking for best power and can afford it. Most (all?) 4-1 systems come from the USA.

3) The wrong muffler can kill your exhaust system, choking your engine on it's own waste. If anyone tries to sell you anything BUT a straight through muffler (straight, flat S curve or offset), be polite but walk away.

4) Yes and no. Obviously extractors will come off and go in the bin when you turbo, but it is possible to put a 2.5\" system on the remainder which will not deliver best power for NA, but will still work OK.

The list of header/muffler manufacturer brands is a very large mixture, even for our car. I suggest you get with a few MX5 folks, find a car you like the sound of and ask what they have.

JSE · Postby **JSE** » Sun May 06, 2007 4:43 pm

i use the standard headers/extractors, a hi-flow cat, and 2.25ich cat-back. works a treat and sounds great. also stainless will set you back big bucks. I have mild-steel and it works perfectly fine.

PUR157 · Postby **PUR157** » Sun May 06, 2007 9:20 pm

a sort of related question on this... (sorry to hijack but thought Id append this burning question of mine in the appropriate thread)

Do you guys (owners of an exhaust modified NA) find the note farty (think overdone Civic Silvia etc.)?
and do you guys have CAI in conjunction with the modified zorsts?

Also my 2c
Isnt the \"least back pressure\" possible route mainly reserved for Turbo applications? letting the Turbo be freer to spool
Its beneficial for a lightly done NA car to have some backpressure yes?

adamjp · Postby **adamjp** » Sun May 06, 2007 10:13 pm

Its beneficial for a lightly done NA car to have some backpressure yes

No.

zoomzoom · Postby **zoomzoom** » Mon May 07, 2007 2:17 am

Firstly, unless you want to spend big bucks on extractors($350+) then don't even bother, I did get a set of ebay extractors and it isn't worth it, by the time you modify them to make them right, you might aswell spend the same time on the std headers diegrinding them out and spend a bit of $$$ to get the 2\" collector cut and replaced with a bit of 2.25\" or 2.5\" to the cat. 2.5\" would be ok to the cat as the exhaust gas cools a little in the cat and then use 2.25\" back, this will give it a nice zippy note rather than the drowny honda civic with a cannon note. Then get a hiflow cat and get 1 45* mandrel bend and 2 90* bends and with some straight pipe and one tiny tiny bend behind the cat you will have a mandrell bent system. Then a staight through muffler will complete the system and wont be that much louder then your origional, just a bit improved note and slightly freed flow.

About using it with a turbo later, you could but it is not perfect, as with an N/A car you want a bit of backpressure and a turbo you want none, so they really are two different systems.

Postby **orx626** » Mon May 07, 2007 10:51 am

adamjp wrote:
Its beneficial for a lightly done NA car to have some backpressure yes

No.

Correct!

adamjp · Postby **adamjp** » Mon May 07, 2007 7:49 pm

as with an N/A car you want a bit of backpressure

No, not if you are interested in performance.

Matty · Postby **Matty** » Tue May 08, 2007 7:46 pm

RaYmO wrote:Hi Guys,

Been tickling the idea of upgrading my stock exhaust for my NA6 and had performed searches on this forum which had raised more questions than answers.

Where do I start?

1) What are the different (road worthy) exhaust set ups available (I see terms such as straight, cat-back etc to describe setups but have little idea what they are)

Go straight through, more flow = more power (but more noise). Make sure you fit a mid-pipe resonator or second muffler.

2) Headers/Extractors - Stainless steel seems the way to go, but there are also different setups (4-2-1 vs the standard 4-1) what's the pro's/con's of each setup? Which version will have the least amount of "back-pressure" by design?

On a road car with a standard or mild cam, it really doesn't matter much. Just make sure they flow well, and are well constructed. But unless you're racing and want to eke out the last 1 or 2 hp, skip them, not enough BFYB.

3) Muffler - performs sound deadening on the exhaust (gotta get one of these) but what is the adverse affect on performance if the wrong muffler is installed?

Lack of top end power or fart-can noise.

4) Is it possible for the above exhaust upgrade to be compatible with a turbo upgrade in the future or will I have to rip and replace?

Yes, leave out a header upgrade. 2.25" should be OK for a turbo, maybe a tiny bit restrictive, but 2.5" will be very noisy NA.

At the end of the day, face the fact that you've got a 1.6, and in NA form it's just not that fast. So don't overcapitalise on it...

zoomzoom · Postby **zoomzoom** » Tue May 08, 2007 8:52 pm

I agree with adam, it is really not worth upgrading the headers on one of these.

Also a straight through muffler is the way to go, you will be very surprised how much sound deadening you will get from a muffler you can look right through. Infact alot of modern cars use straight through mufflers std. The std muffler on the mx5 is even straight through as far as I am aware. I used a 2.25 straight through which was I think about a 40\"x10\"x4\" and it is plenty quiet untill it is loaded up and even then it is not too loud. I didn't use a second resonator at all.

Tim

adamjp · Postby **adamjp** » Wed May 09, 2007 9:00 pm

does any body here run a 2\" hi flow cat into 2 2\" resonators and no muffler on the na6?

By resonators, I assume you mean a hotdog style muffler?

It would sound great, this is what many Alfas and Minis had when i was younger, before noise laws came in.

But it may be a bit too loud. Give it a try 'cause hotdogs are cheap and you can always get a bigger muffler spliced in at the back in place of hotdog #2.

Will sound VERY rorty. Share the sound with us.