Exhaust system for a NC1

[Penguin]

Well I think I am going to have to bite the bullet and make some changes to the induction/exhaust system. I was considering the Cosworth supercharger system, but there seem to be too many problems. So to get a few more usable kW's, changing the exhaust system seems to be the way to go.

I have been reading with interest the debate about cold induction systems and whether they are of benefit - the jury seems to be out on this one. Changing the exhaust system seems to get the thumbs up.

I was considering an extractors to tail pipe change.

Are there any systems that people would recommend and any ones that people would like to avoid.

Penguin

[Charlie Brown]

Penguin,

I’m using the Good-Win Racing 4:1 system
http://www.good-win-racing.com/Mazda-Pe ... -0080.html

and Monte5 is using the MX5Parts 4:2:1 system http://www.mx5parts.co.uk/product_info. ... ts_id/1288

I can report that on the track there is no difference between the two cars in acceleration however the GWR set has more low down torque. Monte notices when the air con clicks in and out where I don’t.

In both cases we are using the standard exhaust system from the extractors back. You need to have the local exhaust shop drill and weld in new oxygen sensor plugs before and after the second cat and then extend the original cable to suit. You can either cut and splice the original or buy a cable from Goodwin. I spliced mine.

Power output on mine went from 91.6rwkW to 105rwkW.

MX5 Parts also have a 4:1 system, so you need to do your sums on exchange rates and transport costs before making a decision.

Good luck.

[Penguin]

Charlie Brown

Is there any reason that you only changed the headers and not the rest of the exhaust. Is it just cost, or that changing the rest of the exhaust only changes the noise it makes rather than the performance?

Penguin

[broady]

Power output on mine went from 91.6rwkW to 105rwkW.

Holy crap! That's quite a gain just from headers. The stocko ones must suck?

[reflex]

[quote="Charlie Brown"]

I can report that on the track there is no difference between the two cars in acceleration however the GWR set has more low down torque. Monte notices when the air con clicks in and out where I don’t.


Power output on mine went from 91.6rwkW to 105rwkW.

[quote]

thats a very interesting bit of feedback CB, thank you for sharing. I've always been under the illusion the 4-2-1 gives more down low punch, and 4-1 is a better top end power delivery option. I've been considering the UK sourced 4-2-1 set, but now given your results (plus i've got the Goodwin race single muffler) the GWR 4-1 set is looking the goods. I'm going to go look for a dyno sheet from your garage post. thanks again!

[Charlie Brown]

Charlie Brown

Is there any reason that you only changed the headers and not the rest of the exhaust. Is it just cost, or that changing the rest of the exhaust only changes the noise it makes rather than the performance?

Penguin

I haven’t changed the midpipe for two reasons. If you look at the Goodwin site you will see that there is very little gain (maybe 2rwkW) from increasing the size and for the cost it’s just not worth it.

I would like a ‘Q’ muffler (have a look at the Goodwin site for the power gain) just for the added sound but again, by the time you land it here the cost is way up there, even with the $AUD being 93c/$.

I bought a 5Zigen muffler from Robbie that had tips the size of drain pipes and when combined with the header, boomed and droned enough to remove the fillings from your teeth. It did feel that it revved a lot freer but I didn’t run it side by side with another NC to test it. It also weighed the same as the stock unit, which is very heavy and something I was trying to avoid.
I sold it to Paul (PAU61L) who ended up cutting the tips off and putting on some more sensible sized outlets that reduced the sound level.

For the track I have tried a small muffler that Paul had made up. VERY loud but very light. By loud I mean you need to wear ear plugs and Mr Plod would take a very dim view. I’ve only used it once at Eastern Creek and once on a very wet Wakefield and the jury is still out as to whether it has any significant gain in power. Eastern Creek is a high speed circuit compared to Wakefield and I think the huge hole left by removing the stock muffler affects the aerodynamics causing drag down the main straight.

I also investigated getting a twin muffler system made up. Cost was around $600 – 700 but I thought that I’d be better off with the ‘Q’ and the known sound and power output rather than take a chance going with a one off.

thats a very interesting bit of feedback CB, thank you for sharing. I've always been under the illusion the 4-2-1 gives more down low punch, and 4-1 is a better top end power delivery option. I've been considering the UK sourced 4-2-1 set, but now given your results (plus i've got the Goodwin race single muffler) the GWR 4-1 set is looking the goods. I'm going to go look for a dyno sheet from your garage post. thanks again!

Reflex,
Monte5 thought the same thing that's why he went the 4:2:1, however when he drove my car he said it had better low down torque besides his air con comment.
Sound wise with your race muffler I think you'll find the noise level will be too much for the road.

If you want a test drive just let me know and we may be able to arrange to have both cars there on a Club run.

[reflex]

Sound wise with your race muffler I think you'll find the noise level will be too much for the road.

If you want a test drive just let me know and we may be able to arrange to have both cars there on a Club run.

Your probably right about the noise level for the road, it is my daily, 50%-60% of all driving done with my wife in the car, although theres no complaints so far.

If i'm being honest, i've no plans for any maximum track attack time in the forseeable future, and even then I think my driving skills learning curve would far out weigh any performance chasing, daily use innapropriate mod requirements.
Springs and whiteline sways will stay at the top of my to-do list for now.

[Penguin]

Penguin,


You need to have the local exhaust shop drill and weld in a new oxygen sensor plug just before the second cat and then extend the original cable to suit. You can either cut and splice the original or buy a cable from Goodwin. I spliced mine.

Good luck.

CB

From what I am reading, is there a second O2 sensor after the second cat?

Also as your cunning cold air inductio? Would the extractors alter whether this is worth it or not?

Cheers

Penguin

[Charlie Brown]

CB

From what I am reading, is there a second O2 sensor after the second cat?

Also as your cunning cold air inductio? Would the extractors alter whether this is worth it or not?

Cheers

Penguin

Penguin,

I didn’t explain myself properly in the original post.

The stock header / cat system has two O2 sensors, one at either end of the cat.
When you replace the stock system with a set of extractors you need to relocate these two sensors by having new threaded plugs welded either side of the second cat/resonator to prevent a cell light being thrown up on the engine management system. If you don’t do this the computer will switch to safe protection mode and run a full rich mixture.

When you move the O2 sensors the stock connector cables aren’t long enough to reach the new location so you need to either plan ahead and order Goodwin’s long and short extension cables or buy some 4 core cable and cut, splice and solder in a new length of cable to extend the original cables. I bought 2 metres of 6 core trailer light cable and did the work before I headed to the muffler shop.

From memory I spliced in a metre on the rear cable and 700mm on the front cable. I wrapped the cables with heat proof tape for added protection and made sure the front cable was pulled well clear of the headers. The rear cable was fed through various braces to keep it way from the exhaust pipe and finally a hole drill through the gearbox flange and a bracket attached as the final cable support. Sounds hard but it’s not when the cars up in the air getting the O2 holes put in. Make sure that the O2 sensors are located to the side and higher than the bottom of the exhaust so they can’t be torn off over speed bumps etc.

On the cold air side of things I’ve fitted the Cobalt CAI from Moss Motors in the US, nice and cheap at around $100. It’s the same tuned length as the stock one and hangs vertically with the intake open to the grill rather than sitting horizontally behind the bumper as the stock one does. I’ve read that the Mazdaspeed CAI, being longer, develops more torque but at $400 it wasn’t on top of my must have list. I found no increase in induction noise or any noticeable power increase when I fitted the Cobalt along with the K&N panel filter.

[Penguin]

Thanks CB

I am currently negotiating the best way to get the exhaust goodies from Good-win.

I will let you know how I get on with the muffler.

Cheers

P

[Penguin]

Okay

Got the Bits. Had a few issues but Brian Goodwin was very good to deal with.

I ended up with a cold air intake (on special), extractors and the Q exhaust. I want to use my own midpipe.

For those who have put on the extractors, where is the best places to put the O2 sensors.

I am really looking forward to see what the change is in the car.

Penguin

[Charlie Brown]

For those who have put on the extractors, where is the best places to put the O2 sensors.

The stock header / cat system has two O2 sensors, one at either end of the cat.
When you replace the stock system with a set of extractors you need to relocate these two sensors by having new threaded plugs welded either side of the second cat/resonator to prevent a cell light being thrown up on the engine management system. If you don’t do this the computer will switch to safe protection mode and run a full rich mixture.

[Penguin]

Thanks CB

I bought the long and short extender leads from Goodwin when I bought the extractors.

I suppose what I was asking was, in others experience, is the best place to weld the threaded plugs either side of the cat, or it really doesn't matter?

Mounting the CAI is going to be the most work from the look of it.

A couple of weeks I hope to have that 10 odd kW improvement.

P

[russs]

Hi Penguin.
I am considering the same mod. I presume the plugs are welded in the side of pipe, a few centimetres before and after the CAT. How has it worked for you? How is the noise level for street use?
What was the total cost including freight and any import duties?
Russ

[Sailor]

One from left field.
http://grassrootsmotorsports.com/projec ... x-5-miata/

http://www.ppeengineering.com/products/ ... miata.php#

Expensive, but may just pass an inspection.