PhillipM

Yes, bit of a strange question this one, but basically we are limited to 98dB in our line of competition, so we've got to make up our exhaust system with that in mind.

Now, the headers are 2", 2mm wall stainless so they should dampen some of the noise down (37.25" to the collector for the interested, bar the merged centres, which join earlier to keep mixed pulses out of the way of the ones we can actually use to good effect), after this we are switching to 2.5", 1.6mm wall stainless, and we are hoping to get away with a 14"x7"x5" oval muffler.


Now, we are hoping that would be just enough, but if need be we can squeeze anther muffler in there, but if anyone has a similar setup - tubular headers + big single muffler - how loud is your car?

expo1

Could this Racing Beat exhaust be of help?

PhillipM

Anything relevant helps

I've been flicking through the forums for a while looking for small power gains (reluctant to pull a new crate motor apart for machining, so bolt on for now), and read the snippet about the original HP claims being for an engine with no ancillaries, now, given we'll never be below 5krpm, we could probably run a seriously under-driven crank pulley, maybe half-speed, but how much difference does that really make to the cars?

PhillipM

While I'm at it, is it possible to blank off the intake oil feed system (running pre-mix), or will it have to be kept in addition?

romycha1

Are you talking about the Sohn Omp Adapter?

PhillipM

I have no idea!

The little oiler unit that feeds to the intake ports to lubricate the rotor seals.

Keef

Putting a breather filter on the intake oil part of the feed system, then blocking the intake part creates a slightly different response in throttling...

Also running pre-mix all the time, after 2,000 miles has given me a different change in exhaust tone under WOT. You could probably achieve the same thing by running different oils, but having run Idemitsu's pre-mix such makes 7,000 RPM roar almost too loud at times... It all flies though, so I have no worries... And to run pre-mix all the time your going to need this!!!

romycha1

This is a forum member's(GTAW) website I believe.

http://www.turborenesis.com/ompadapter.html

PhillipM

So it can't just be blanked off and just use purely pre-mix in with the fuel then?

romycha1

If you block it off, then how would you lubricate the seals?

PhillipM

2-stroke oil in the fuel?

Or have I missed something here?

PhillipM

Cleaners in the 2-stroke oil lifting carbon off the exhaust ports perhaps?
Seen it with a few 2-strokes when they've switched oil brands.

TeamRX8

iTrader: (25)

loud

how loud depends on the silencer

PhillipM

I guessed that, just (perhaps in vain) hoping someone had a similar setup and knew the rough noise output.

romycha1

I don't think that would be enough to oil the seals... would it?

PhillipM

Can't see why not, doesn't inject a lot of oil anyway does it?

Brettus

iTrader: (2)

you'll be fine as long as you run a rich mix . Racing Beat recommends 80:1 for maximum power .

PhillipM

Thought so, cheers, so how do I stop the engine burning my lovely Millers synthetic then?

Brettus

iTrader: (2)

Someone suggested to me that you can take the oil metering pump apart and put the return spring on the pistons on the other end - rendering the pistons inoperable without triggering the computer into "limp mode"
MM also suggests buying another OMP and connecting it electrically and strapping it out of the way somewhere ....

PhillipM

be running a Microtech ECU so fault codes aren't a problem!

I can blank it off without any problems then? As you can guess I haven't taken it off for a look yet!

Brettus

iTrader: (2)

BTW - they are running an 8 in production class here with a single muffler . No numbers on it but they seem on a par with other cars on the track noise volume wise . They dont have a header and the stock cat is in place with all its internals removed .

Brettus

iTrader: (2)

You won't be able to drive the car if it goes into limp mode so being able to reset the codes will not help you there - you kneed to do it in such a way that electrically the computer thinks it is still working . You probably don't want to blank off the hoses - oil does not compress

can I suggest you don't go with microtech unless you are very intimate with them - I think they don't cope well with the drive by wire . The interceptor x sold by Mazsport is a modified Microtech made just for the 8 . I run a unit from Aussie (Powermod)which works really well and is cheaper than the Int x. There are others around as well .

PhillipM

That's promising then, saves some length on the rear frame if we only need one silencer!

We have the RX-8 specific unit, but we're using a duratech throttle body instead anyway, as fly-by-wire is not allowed under our regulations.

Brettus

iTrader: (2)

What kind of car is it ?

PhillipM

Little 2wd buggy, similar to a 1600 class but a lot smaller and narrower for rally work.