NA6 Intake/Exhaust Mods

Matty · Postby **Matty** » Fri Jul 29, 2011 6:28 pm

gslender wrote:Matty, are you therefore stating that an incoming airflow (from driving the vehicle forward) is unable to compress/force air into the engine beyond what it can suck in itself - eg. thinking that you can produce the outcomes of a Supercharger/Turbo are just not possible - even when standing in a 100km/h wind?

I don't disagree, but just don't fully appreciate why this is so?

No, what I'm saying is that you will get a very (very!) small benefit from ram air, but it is largely insignificant at road legal speeds, and of course will only be of benefit if your intake is right on the nose of the car (picking up from the mouth in front of the radiator might give similar benefits though).

The pressure loss created by sucking air through the piping, AFM and filter works to cancel this out though.

It's not about having one value bigger than the other - they're additive (the pressure loss is negative though). Any ram effect is good, but you're better served by minimising losses in the intake system rather than trying to site the pickup at the best point. You can do a little of both though.

There's plenty of articles on autospeed reviewing intake siting and the measured effects.

Postby **NitroDann** » Sat Jul 30, 2011 8:14 am

Not 2 psi, 1psi.

Also all tests are with engine off, so intake restriction wont help, as its fully stalled airflow.

Hellmun also has a well built, sealed and sheilded intake setup, which regularly blows itself apart. He hasnt managed to find a way to keep it together due to the pressure.

Dann

gslender · Postby **gslender** » Sat Jul 30, 2011 8:48 am

Dann, I think the point is you've only got 1psi of static pressure. Dynamic pressure you've probably got bugger all of sweet nothing.

So whether you think the JR setup or your setup is better, without larger intake runners the difference is not worth debating.

End of the story, both are doing the same (or not).

G

Postby **NitroDann** » Sat Jul 30, 2011 9:00 am

Mines not emptying anyones wallet.

Bigger intake runners wont help, they would show even less pressure.

Back on topic..

OP how are you getting along?

Dann

gslender · Postby **gslender** » Sat Jul 30, 2011 9:59 am

NitroDann wrote:Mines not emptying anyones wallet.

Mines not drilling holes into the firewall and doesn't look home made by my mother

So for the benefit of the OP...

You can do many things to improve the MX5 intake; from my experience a 2nd hand JR kit worked fine, was cheap (for me) and was easy to install. Many others are available and will probably do the same. Some require permanent damage to the originality of the car (and require you to be capable of wielding a power drill and own metal circle saws), others are simple bolt ons where you only need a bunch of ring spanners and screw drivers (taking only 30 mins to install). All of them are very likely to be equal, as long as you are getting cold air into the intake, allow you to install a free flowing filter, and collect air from a location that is positively pressured (and it seems that last point is one of splitting hairs and marginal benefit at best).

After you've done extractors, exhaust, intake (filter and CAI) and advanced the timing to 14 deg, you should have a fairly reasonable and noticeable change.

Other changes like changing ECU, cams, shaving the head etc, are fine improvements, but we're now getting expensive (in total) and you need to have the former things done to really get all the benefits of these last items.

Way up the options, use "common sense in context" and don't listen to just one persons opinion - including mine. Ask a few and go with what most are saying - they are usually correct.

G

Postby **NitroDann** » Sat Jul 30, 2011 10:25 am

I agree, with all but the last point.
Popularity proves nothing.

Dann

Postby **NitroDann** » Sat Jul 30, 2011 10:46 am

also im getting some clear tube and testing everywhere intakes are put.

Dann

93_Clubman · Postby **93_Clubman** » Sat Jul 30, 2011 2:52 pm

Cerberus wrote:Benefits/detriments of shorter intake tract?

viewtopic.php?f=29&t=27062

See Matt9111's post near bottom of page for hub dyno before & after numbers:
viewtopic.php?f=29&t=33837&st=0&sk=t&sd=a&start=60

Alternative view to the torque dip believed created by removing the Helmholtz resonator from the intake pipe across the front of the engine:
viewtopic.php?f=29&t=34361

Russellb's OEM filter v no filter dyno numbers:
viewtopic.php?f=29&t=33840&p=437814#p437814

Matty · Postby **Matty** » Sat Oct 08, 2011 3:04 pm

tommop wrote:OK so here is an easier question to answer - will a pod fiter replacing the stock air box make me lose power due to radiant heat from the stock exhaust manifold even though the stock intake tube is in a similar location?

Also it seems a little pointless putting a heat shield between the exhaust manifold and an open pod considering it's full effect would only be when there is no circulation in the engine bay (stationary - not needing the ponies anyway)

I'd like to improve the intake sound with a pod - am not too concerned how much extra power it will make at this point however dont want to lose power.

great read btw

It might lose you some power when travelling really slowly, eg in traffic. At other times, the reduced restriction should more than cancel out any losses due to heating.

Unfortunately it's a very hard thing to determine, really the only way would be by directly measuring the on-road performance.

BTW a cowl intake will give you more noise

ak_perth · Postby **ak_perth** » Sat Oct 08, 2011 5:11 pm

ROAR, ROAR!!!!!

I love my MX5 Mania cowl intake :lol:

Postby **NitroDann** » Sat Oct 08, 2011 5:18 pm

I run my intake pipe filterless straight off the throttle body out the bonnet and in through the drivers side window.
It terminates just next to my head.
Sounds awesome until your face gets sucked through the engine. :mrgreen:

Dann

ak_perth · Postby **ak_perth** » Sat Oct 08, 2011 5:51 pm

^^^ Lol!

zephyrus17 · Postby **zephyrus17** » Tue Oct 11, 2011 12:36 am

*sigh* my exhaust system has seen it's end of days.. Lift-off throttle, and it starts sounding like a bunch of coins jiggling in it. It's not the heatshield, either.

So I'm now in the market for a cat-back. I've been looking at all the common names like Borla, FM, Good-win, Racing Beat, Cobalt, Magnaflow, etc, and listened to them on youtube, but I know how reliable that can be. I just want something that's not raspy, doesn't scare children when I'm cruising around, but gives a good howl when I push it and downshift. So a resonator is a must. Bassy and mellow. I'm leaning towards the Cobalt since it's the cheapest of the bunch and not eBay. Any opinions?

Postby **NitroDann** » Tue Oct 11, 2011 9:39 am

Bassy and mellow basically means you need a chambered muffler, which is a shame because that costs horsepower compared to a race style muffler like a magnaflow. Id also consider getting it made in mild steel for the deep roar sound.

The rattling is one of your mufflers or cat, it you get underneath you will be able to determine which one and just replace it if you want.

Dann

zephyrus17 · Postby **zephyrus17** » Tue Oct 11, 2011 10:13 am

It's the muffler. While I got the mechanic (John Keen from Southern Hi Tech) to do the timing belt, I asked him to check the noise and it's the muffler. He gave a price of $400 to weld a new muffler on, but I wanted to take the chance for some aftermarket ones.

Sadly, after a round of emailing, the shipping costs from Moss Miata, GoMiata, Good-win, FM are way too expensive ($500) so I'll have to source them locally from wreckers or Mania. Does anyone have experience with the Mania 2.25" Cat Back for the NA?