I’m looking for technical help or recommendations on: exhausts and skinflintyness
This might be a question that’s been hashed out loads in the past but I couldn’t find a good answer for current prices…
I have a broken NC 2.0, which I’m going to drop a 2.5 into over the winter. Initially it’ll be totally standard but in the longterm I’ll likely look at cams or ITBs. But, it’s basically a cheap engine-stab for now.
I probably wouldn’t have touched the exhaust, but while it’s out I’m inclined to stick in a set of headers, since it’s no extra labour.
So, the age old question is, cheap or good. This isn’t a top-dollar car, but I don’t mind spending money on stuff that really works where it counts. But at the moment, the Gravity/generic 4-1 is £152. I’ve no doubt that the IL 4-1 is better, but is it £250 or 2.5 times better? (both will I think have the exact same considerations for EML/lambda sensors)
Basically this is just a bang-for-buck decision, I don’t mind losing a few horsies along hte way for a worthwhile saving, especially when that could be going towards something else. Also in my mind is that at £150 even if it sucks, I can’t lose out badly especially when selling the stock cat.
Hi, think carefully about how much noise you want / can put up with and about getting through an MOT.
I have done this twice on an NC - first time I went fully IL motorsport, front CAT deleted. It did make a difference to the power no question - never driven so well, BUT my god it was loud - not so much outside the car but inside the cabin! I mean headache inducing loud all the time, can’t hear radio. Ruined the car really. MOT wise it passed on emissions BUT the MOT guy said it should really be a fail as if it came from factory with two CAT’s it should have two CAT’s to pass MOT. Luckily the chap I use is pragmatic. I wish I had not bothered.
That said I have just purchased a complete tuned exhaust from Goodwin Racing that has some trickery on the mid pipe and back box so its quiet at low / medium revs and only makes a noise at high RPM (has an additional HELMHOLTZ tuned resonator box ) so you get the best of both worlds!
Thanks- I’m aware of the MOT issue, I don’t think my guy will raise an issue (not because he’s shady, he’s just not an MX5 specialist so won’t automatically know it should have 2 cats, as long as it passes emissions).
Volume wise, it’s currently totally stock exhaust- actually came with a venom end box but it was just horrible (not so much loud but just unpleasant) so that came off. I don’t mind a bit of volume but it’s interesting to hear how much difference the cat makes there
My experience is pretty different to be fair. For context, I used to reside in the Honda scene. Having had a SOHC VTEC 1.6 and the famous 1.6 DOHC VTEC, JDM variant with 170hp. Had them with and without cat, with straight through with and without silencer and a HKS HiPower Silent. I have also heard a lot of different exhaust on those engines in different Honda’s
Currently my 2.0 NC has the IL Motorsport 4-1 decat header and IL Motorsport center section with sports cat. All combined with stock backbox. I was actually surprised of the lack of drone in the cabin. I find the volume of my exhaust not even that much more, more like OEM plus. The tone of the sound has changed significantly, it’s a lot better. And it evidently freed up power in the top rpm range.
The volume of the sound is at most comparable to my Honda’s with cat and silencer, but I think even that was louder in mid range and treble. Also way less drone. Not to mention the sound type is better on the Mazda.
I would qualify decat header and center pipe with sports cat with stock backbox as OEM+.
actually I see the difference - you still have the stock back box which is the silencer so yes it would still be quiet.
I have complete end to end IL exhaust, headers to and including the back box to take advantage of the headers and mid pipe - but the IL backbone is basically two small and straight through silencers (one each side) which really don’t do much at all and are extremely loud.
So I guess it’s the back box only that really effects the noise. My new Helmholtz backbox has adjustable baffles so you can quiet it down or take them out for the track.
Just didn’t want anyone to spend £ks on an aftermarket exhaust and then hate the sound.
