I have a 96’ Mk1 which has recently developed an annoying (and now almost unbearable) rattle which I was hoping someone might be able to help with. The rattle only begins once the engine is warm and sounds like a metallic rattle at the rear of the car. I have checked some more obvious culprits such as the heat shield and exhaust clearance but none seem to be causing it. After driving the car, the exhaust will also rattle if knocked, leading me to believe it is something inside the back box.
I bought the car with what I believe to be an IL motorsport catback system installed and I have a suspicion that the baffles may have come loose in the back box, but the only way I can see of checking this is cutting it open. The only other solution I can see is buying a new back box but many of the affordable options such as the MX5 parts and Cobalt systems are both out of stock!
I could be wrong but I think I remember reading something a while ago about the IL Motorsport exhausts not having a huge amount of clearance under the car and knocking against something. I have one on my MK1 (the only exhaust I could find for the 475mm cat) but not had that problem so never really looked much into it. Will do some digging to see if I’ve actually made that up or not.
Probably is the baffles because I’m not certain the ILM exhaust was of the highest quality.
If you have a 1996 UK car, its possible an off the shelf cat back system won’t fit anyhow, on account of the cat fitted. But yours might have been converted. If not, the non-availability of the Cobalt (or the SS MX5parts) system is moot; it won’t fit withut modification.
MX5parts has a standard system in stock for the later cat:
It’s really quick and easy for someone who knows what they’re doing to cut open the top of the back box, remove or re weld the loose baffle, then weld the flap shut again.
Try some smaller exhaust places, there’s bound to be one who’ll do it for you, and it shouldn’t take more than an hour or so if you take the box off the car beforehand.
Yea when I had a look under the car all of the clearance seemed fine. I drove the car for around 8 months or so with this exhaust setup even up to Scotland and back and never had an issue. It just suddenly started one day on a boring commute drive.
Thank you for the recommendation, I do enjoy the sound of the IL motorsport exhaust, however I could do with a quieter one as it does get a little annoying sometimes on longer journeys. I might have to buy a new cat to fit a new system but judging by the look of the current cat this may be for the better anyway.
I have tried to cut a very small hole in the exhaust previously as thought something loose may have been rattling around inside. As it turns out what appeared to be broken up carbon build up or something of the sort came out in loads and loads of small pieces. But after putting it back on this didn’t really solve the problem at all. May have to look into getting someone to cut it open before buying a new one just to see. Thanks for the help.
If you want to fit a shorter cat, in order to fit off the shelf exhausts, you need to replace the manifold downpipe as well, around £350 plus fitting. At that price, it might be work looking at a bespoke exhaust; they’ll be able to build the exhaust to get it to sound exactly to your requirements. Plus most of them will do lifetime guarantee on their systems, but the cheap catback systems will have none of that.
Thread from last year. MIJ come up quite a lot, but it depends where you are. And there are others. Depending what the rest of the system is like, you might just need a back box. On my 96, when I brought it, Powerflow had just cut the standard exhause at the rear subframe brace, and added a backbox, connected using a standard exhaust clamp.
That’s great thank you, I will have a look into some local companies and maybe get a quote. I would ideally be able to keep the IL midpide and fit another back box if possible but will check for dimensions.
If the cat is standard, its 475mm (and change) long, If its 440mm (and change) long, someone has done the change, and your options are open to complete off the peg cat back system.
Besides MX5parts, the only other company who did catback for the later model was Larini, which MX5heaven used to sell.
If you get a custom jobbie, make sure they don’t tack weld the hangers to the flat parts of the silencer. Mongoose did this to the first system I got off them 20+ years ago. The weight of the silencer caused the welds to crack and rip holes in the silencer. Something about stainless steel welds being more brittle than regular steel.
20 years ago there were a lot more exhaust options for the MX5, but they seem to have mostly gone now.
Yea, I have also found a review for the IL motorsport exhaust on MX5 parts saying that the baffle came loose on two occasions so think this must be the issue with it. The link you sent for BOFI racing has an M2 motorsports backbox in stock which I believe should fit with the current midpipe I have so might just buy it and see if this fixes the issue. Thank you for all the help!
I had the same system on my MK1 as the OP. I cut the box open, pulled out the offending baffle with extreme prejudice and took more or less all of the fibreglass wool type stuff out of it too. Welded it back together and it sounded AMAZING! Just the right side of noisy without being deafening. Could be worth a try?