2006 Mazda MX-5 NC 2.0 Sport

[gazzarose]

Whats the deal with MOTs and decat manifolds these days? I'd love to do a manifold on mine, but the difference between a non cat and cat'd one is just too much money. But reading the faff its taken to change yours, it's not looking like something I fancy swapping back and fore like you read about folks with normal decat pipes doing. Because it has another cat, is the deal just hoping the tester doesn't notice it and the exhaust readout will still be fine? The place I have my MOTs done does alot of performance cars, but are also quite proper in how they do most things, so don't know which way it would go with them. Also one of those things I don't want to ask in advance in case that just tips them off.

[Cambs_Stuart]

That looks like a painful job. Good work getting through the issues and completing it! Also good to read that you can feel the benefit.
If you were to do it again, would you do it differently?

[geraintthomas]

Accelebrate said:

No problem at all, glad you got there in the end. I felt a bit bad for suggesting it was a relatively straightforward swap - with the bolts on my heatshields coming out relatively easily, along with the sensors I managed to get both manifolds out and in without touching the engine mounts or the alternator cover.

Flex head ratcheting spanners are such a godsend for this job!

Technically it is straight forward, but Murphy's Law was prevalent throughout the whole job...

freedee said:

Great write up, thanks.
I have a decat manifold sitting next to me waiting to go on. I will ask the garage to fit it and remap the car at the same time

Make sure it's not the same garage that does your MOT's!

gazzarose said:

Whats the deal with MOTs and decat manifolds these days? I'd love to do a manifold on mine, but the difference between a non cat and cat'd one is just too much money. But reading the faff its taken to change yours, it's not looking like something I fancy swapping back and fore like you read about folks with normal decat pipes doing. Because it has another cat, is the deal just hoping the tester doesn't notice it and the exhaust readout will still be fine? The place I have my MOTs done does alot of performance cars, but are also quite proper in how they do most things, so don't know which way it would go with them. Also one of those things I don't want to ask in advance in case that just tips them off.

That's exactly what the deal is. If a mechanic was none-the-wiser, they'd look at the car, see a cat installed, see it pass emissions and will think everything is fine. However if a cat is present from the factory and you remove it, it's an automatic fail, regardless if there's one on the car still. If the garage doesn't know that there should have been one on the manifold in the first place (and it's pretty hard to see with the heat shields back on), then you can quite comfortably get away with it.

Similar to Xenon bulbs. If you install them into projector headlights and they have the correct colour and cut-off pattern, then they're fine with it, even though it's not legal. On that note, the MX-5's head lamp cut-off pattern is that of a xenon bulb, even though it has halogens. Really interesting...

Cambs_Stuart said:

That looks like a painful job. Good work getting through the issues and completing it! Also good to read that you can feel the benefit.
If you were to do it again, would you do it differently?

Thanks, it was certainly an experience. It wouldn't be half as bad the second time as I know what to do - leave the lower heat shields in place, un-bolt the rear cover off the alternator, and slightly silt the engine, and it'll come out fine. If the guide I followed had mentioned that from the start, it would have been an easy job. It was the fact that I ran into problem after problem, and finding those solutions the hard way.

I wouldn't want to put anyone off doing it, I'd just recommend that you have a flexi-head 10mm spanner (for the heat shields), an offset swan neck 14/15mm spanner (for the bolts under the car connecting it to the mid-pipe), but the most important set of tools was a 3/8" socket set that had a mini breaker bar, and a large selection of extensions and deep sockets. These were critical for the manifold bolts to get to those under the pipes. The 3/8" head could fit where you needed it to fit, the deep sockets allowed the bolts to sink into the socket while undoing the nut, and the mini breaker bar gave you the force to crack them loose.

Secondly, a set of shock absorber ratchets - I wouldn't have been able to complete the job without these. The two bolts that are right at the back are so close to the bulkhead that no ratchet could fit there. A shock absorber ratchet is very stumpy, which gave me access to them. My neighbour came to the rescue with all of these tools; I don't know what I would have done had he not given them to me.

So I'd like to say "I'd make sure I have the right tools", but the only way I found out was by doing the job. If anyone's thinking of doing it, I'd be happy to give advice.

[gazzarose]

Good to know its tricky to see if its got a cat when the shields are back on. My MOT isnt until Oct/Nov, and I probably won't be in a position to do the manifold this year, so it may be a good winter project post MOT this year or next then at least I get most of a year before I need to worry about it.

Let us know how it feels after you get it mapped, and also where, I'm in Bridgend so will be looking as and when I do mine.

[geraintthomas]

gazzarose said:

Good to know its tricky to see if its got a cat when the shields are back on. My MOT isnt until Oct/Nov, and I probably won't be in a position to do the manifold this year, so it may be a good winter project post MOT this year or next then at least I get most of a year before I need to worry about it.

Let us know how it feels after you get it mapped, and also where, I'm in Bridgend so will be looking as and when I do mine.

Ah! You're not far away at all. Shall do. It looks like I'll be going with a company called Fab9, who specialise in tunes. They're american, and they send the map to you along with the software for you to upload to the car yourself. You can ask them to post a cable (though from the US it can be pricey), but they've emailed me a list of cables that are compatible, and more importantly, ones that are not.

The software also allows you to disable the O2 sensor too. In all it's about £279. The beauty is that it's tailored for the MX-5 NC, and you have the opportunity to tell them that you've made modifications (exhaust, headers, intake) so they can modify the map. They've been super helpful so far, so I'll most likely go with that. I'd rather that than some generic VAG tuner.

If you ever wanted to have a look/drive of the car with the manifold, give me a shout - I can pop over.

[gazzarose]

geraintthomas said:

gazzarose said:

Good to know its tricky to see if its got a cat when the shields are back on. My MOT isnt until Oct/Nov, and I probably won't be in a position to do the manifold this year, so it may be a good winter project post MOT this year or next then at least I get most of a year before I need to worry about it.

Let us know how it feels after you get it mapped, and also where, I'm in Bridgend so will be looking as and when I do mine.

Ah! You're not far away at all. Shall do. It looks like I'll be going with a company called Fab9, who specialise in tunes. They're american, and they send the map to you along with the software for you to upload to the car yourself. You can ask them to post a cable (though from the US it can be pricey), but they've emailed me a list of cables that are compatible, and more importantly, ones that are not.

The software also allows you to disable the O2 sensor too. In all it's about £279. The beauty is that it's tailored for the MX-5 NC, and you have the opportunity to tell them that you've made modifications (exhaust, headers, intake) so they can modify the map. They've been super helpful so far, so I'll most likely go with that. I'd rather that than some generic VAG tuner.

If you ever wanted to have a look/drive of the car with the manifold, give me a shout - I can pop over.

Thanks for the offer. I may well take you upon on it in the next year or so.

Interesting with the Fab9 thing, can you just keep changing things and they keep sending new maps? People on various forums and facebook groups talk about this throttle limiting thing in the first few gears, does it get rid of that? If its a one time deal, then I'd wait til I had done some actual mods, but if you can keep requesting new maps it would be interesting he difference various steps make.

[geraintthomas]

Had an issue last night. My neighbour rang the doorbell at 11pm, telling me that I've left my lights on. I looked, but the tail lights and interior lights were all off. Stumped, I checked the cabin to find that I didn't leave them on at all; they've come on by themselves, and I couldn't turn them off.

It was also raining heavily, so you've probably already put 2 and 2 together.

It's common for these to leak under the windscreen scuttle, but in my first few pages of this thread I replaced the grommets to prevent this from happening. But it looks like even new grommets aren't fit for purpose, as I've had a leak, straight down into the fuse box. I disconnected the battery, and left it until today where (until now) we've had good weather.



That's not a great sign, but also not uncommon. Running my finger underneath the heater blower confirmed that there was a slight leak.



Here is where they leak.



I've removed the grommet to seal underneath it.





Not the prettiest, but you won't see it anyway.



I let the hair dryer dry the area, though by this time there wasn't any obvious signs of water by the fuse box, thankfully.



I'll leave this silicone bag here just in case. I'm not too sure how effective it'll be, but it's better than nothing.

The car seems back to its normal self now, with no gremlins to be seen. Hopefully that was caught early.

[geraintthomas]

Accidentally snapped one of the legs off the windscreen scuttle gromet caps.



Time to 3D print one. Thankfully, someone had already modelled one, which made my life a little easier.





It'll do until I buy some genuine ones.

[geraintthomas]

The car has been performing awfully recently. A steady throttle feels like someone feathering it. It was all over the place, so I read the codes and found something unusual.



I'm expecting a CEL as I've obviously removed sensor 2, but I didn't expect a code for sensor 1. After some investigation, it looks like my extension job for the O2 sensor was at fault. I presumed it was the soldered areas somehow shorting.



I wasn't wrong. It's not that clear in this photo, but two of the wires have quite sharp bits on the solder. The heat from the manifold had shrunk the shrinkwrap further making a lovely fit, but also causing the sharp solder bits to pierce through, causing a short.



I wrapped the wires individually with insulation tape, and managed to fit the original heat wrapping over it.



That's better. The performance is solid, no hiccups and only the one expected CEL.

[MB140]

If your going to join two wires in a loom like that it’s better to stagger the joints if possible (I’m viewing this post in an old phone so the photo isn’t mega clear) to prevent this from happening.

I work in the aviation industry and when repairing looms on aircraft there is often a manufactures specified minimum distance between repairs in the same loom.

Nice work on the manifold by the way. Looked a bit of a pig of a job.

[geraintthomas]

MB140 said:

If your going to join two wires in a loom like that it’s better to stagger the joints if possible (I’m viewing this post in an old phone so the photo isn’t mega clear) to prevent this from happening.

I work in the aviation industry and when repairing looms on aircraft there is often a manufactures specified minimum distance between repairs in the same loom.

Nice work on the manifold by the way. Looked a bit of a pig of a job.

That's a great tip, thank you!

[geraintthomas]

DHL came bearing gifts





Four weeks from ordering to manufacturing and delivery. That's quite good, compared to how long others have waited. I wouldn't have minded waiting if the quality is good.

And the quality is good.











I'll need a cutting wheel for the dremel to trim some of the plastics before I fit this. To be honest, I could do with a new dremel. It's started making some horrible grinding noises, which I'm a little uncomfortable with considering how fast it's spinning, and the pressure I'm putting on the motor shaft. They're quite cheap anyhow.

As soon as I have a sunny and free weekend, I'll crack on with the fitment. I'm now on the lookout for a decent pair of seats, most likely used. I've seen some very good ones pop up on Facebook Marketplace recently, so I'll just have to keep an eye out. The harnesses will have to be ASM-type harnesses (or 6-point), and I'd need new mounts for the car. After that, the car is pretty much there for track use.

The only things remaining is the remap for the manifold, and some semi-slick tyres. The latter can wait, I'm very happy with how these Falkens have performed on-track and off-track, and how they're lasting. It's giving me no reason to purchase semi's at the moment, so that'll be the last thing I'd buy.

[geraintthomas]

I had some free time in the late afternoon/evenings over the past few days, so I put this time to installing the roll bar. The installation looked pretty straight forward, and aside from cutting plastics, it was.

First off, the plastics behind the seats, the side skirts, and boot plastics (for easier access) need to be removed.



Believe it or not, this wasn't everything.



Those rear speakers won't be going back in. Honestly, they're useless, and I could never hear them. There's also no mounting points on the new roll bar for them, which I'm not bothered about.



That's everything out, including the original roll bar.



The difference is enormous. The old bar is tiny in comparison, with only limited contact points. I'm not sure how good this would have been in a roll, but I suppose it couldn't have been manufactured if it had failed safety tests.

The new one mounts not only to the original mounting points, but to the top of the suspension too.



The belt guide was a little tricky as there weren't any areas for this to bolt onto the new roll bar. A little odd, as it wouldn't take much for GCFabrications to put in a hole for this.



In the end, I removed a 10mm bolt just above the retentioner and placed it underneath, lower down than where it should be. I was afraid that this would affect retraction, but after testing it with all plastics back in, it's made no difference.





The plastics need to be cut. I didn't take many photos of this as I just wanted to get the job done at the time.





I've not done the prettiest job because I'll be covering this later. Accelebrate has done a great job at covering his, so I'll no doubt be going down the same route.





It's quite amusing sitting in the drivers seat with this behind you. It gives the car a more purposeful look which is always a plus, but the added benefit on top of the safety benefits is chassis rigidity. I've not had a chance to really test this yet, a quick pop to the shop didn't prove much of a difference.



With the spoiler and roll bar, my rear view is slowly becoming less and less. It's still good considering.



I have to say, it looks great.

Edited by geraintthomas on Thursday 18th May 23:07

[trails]

looks 'right' nice work fella

[ChevronB19]

Looks good. Is there clearance with a helmet on?

[Pent]

i cant see any pics

[dapper]

Pent said:

i cant see any pics

Pics not loading for me either, may just be the work internet though. I'll have to try when back home. Really interested to see the manifold bits as I also have one to go on. Although mine has two o2 sesnsor points on it so I can put both back in. It will still give the CEL ofcourse.

[geraintthomas]

That's odd... try a different browser? Works for me at home, mobile and in work.

[Cambs_Stuart]

Works for me (Using chrome on a laptop). It looks really good. Very purposeful. I'm surprised Mazda didn't tie in the factory roll over bar to the suspension? Seems like an obvious and fairly easy thing to do?

[Pent]

its working now lol