Simple torque/power improvements for NA

[Guran]

There are also heat shields further down the chain on the exhaust pipe itself. Might be worth putting your car up on jack stands and having a look at them too.

Are you able to replicate the noise with the car parked in neutral, and gradually applying throttle to increase the revs through the range? Or do you have to be on the move to hear it?

BTW, nice avatar!

[emx005]

Exhaust heatshields are well know to go 'zing' at certain RPM. Common problem for NAs.

2800rpm for me

[Noddycar]

Hi Guran

No, it seems to only want to play when the car is in motion. I did get a small inkling of it being there this afternoon when I parked and revved the engine, but not enough to be able to isolate it. As you suggested, I may need to stick it on stands and check the whole system. I would prefer to let the mechanic isolate it, but it seems to be a bit shy when near a service centre!

[Juffa]

Here is a couple of links that may help with your rattle issue.

This one is good as it includes photos. In my experince, having owned 3 NA6 MX-5s the likely suspect is the heat shield on the exhaust manifold prior to the cat. It is the 3rd photo in the link. -->> http://forum.miata.net/vb/showthread.php?t=371939

This is a link to all MX-5 related noises. -->> http://www.miata.net/garage/noises.html

Hope this helps.

J.

[Noddycar]

Thanks Juffa

I spoke to Kevin at Mazcare and have organised to take it to him, if it happens to make the noise on my way into work. If it doesn't, I will be getting it into some stands this weekend to take a good look at the whole system.

This is all good information, as I had no idea where to start...

[michael]

Nobbycar,

I had an NA6 with exactly the same problem, particularly during engine braking. After having checked heat shields, clutch plate springs and several visits to different gearbox specialists, the consensus seemed to be that it was gear chatter due to the gear space tolerances in the early gearboxes not being as fine as they perhaps should be. It affects some but not all gearboxes and is more prone in higher mileage examples. Apparently it will not do the gearbox any harm but if this is the cause it is likely to be permanent and I found it quite annoying, particularly with the soft top up or hard top on. Speak to Danny at MX5 plus service at Geebung. He is quite familiar with the issue.

Regards
Michael

[Noddycar]

Juffa

I finally got the a noise to occur with the hood up. It doesn't sound the same as what I hear when in the car, but obviously it distorts by the time it gets into the cabin. The small shield near the base of the manifold sounds quite "tinny" when revved and seems to be occurring in the correct rpm range. Well, that's the general direction of the noise, so it could be lower. I have taken a photo of the shield, but am not sure how to load it here...

[Noddycar]

Hi Michael

That is something that had been suggested to me. My car has 135000 k's, so it is pretty low for a 17 year old car. It is still a possibility (unfortunately). The only positive I have is that this only started after a drive up Mt Glorious, which was followed by a very bump ride around Somerset Dam. This gives me hope that is more likely to be something loose, but if it is the gearbox, I will need to deal with it
I have my fingers crossed it is a loose component.

[Noddycar]

Pic attached.

[Juffa]

Pic attached.

That looks like one end of the cat? Looks like the heat shield has come away from the spot weld. I would putting a host clamp around it to stop the vibration.

If you are hearing a grinding sound when lifting off the gas this has long been suspected to be gear box related. Mine only occurred when I had the clutch changed in two of my 5s. I found the noise went away when I upgraded the diff on my last 5 to a LSD from a later model. The LSD has rubber vibration isolation pad where the tail shaft connects to the diff. While it did not fix the suspected underlying issue with the diff, it did stop the sound. I drove both cars for a number of years with the grinding sound and did not notice it getting any worse, or other related issues appear. So it was never a high priority for me to fix, especially given the labour cost of removing, overhauling and reinstalling the gearbox.

J.

[Noddycar]

After messing with that small heat shield last night, I did not get the noise this morning after extended driving (but this also happened after playing with the heat shield over the manifold). I actually stuck a long screw driver under it and tried to pry it, to see if it was loose. No noise since. I just read the FAQ on Miata rattles and read "After crawling all over and under the car, I isolated my loud buzz (tinny rattle) at 3000 RPM. It came from the heat shield just below the header heat shield. It was designed with an open joint running parallel to the pipe on the drivers side. Long screwdriver fit under each side at the top quite nicely. I pried both outward gently about 1/8 to 1/4 of an inch. Cheapest and easiest fix I've ever had, once I found it". Hopefully that was my problem as well and my screwdriver fixed it.....

Juffa, the noise was occurring at 3000-3500 RPM, regardless of whether the clutch/gearbox is being used actively. As a precautionary measure, I will pick up a hose clamp tonight and place on that section, as it seems strange that it disappeared after I messed with it last night. I am going to drive the little beastie everywhere this weekend to see if the sound returns....

Once again, all great advice! I am constantly cutting and pasting pages from this forum, FAQ's etc to make my own electronic bible on the MX-5. After enough reading and research, hopefully I will actually be able to help others rather than pester them with questions!

[Noddycar]

A huge thanks to Geoff for dropping in to show me his car on the weekend. While I was extremely impressed with the cool racing stripes and the minor engine mods , the best thing by far was feeling the handling of the car after the suspension and body changes. Wow!

As much as the growl with the cat and airlfow change was nice, the ride was the thing that really got my attention. Suspension and stiffening will be my first job, before I worry about the air intake etc.

Thanks again Geoff! I hope to be able to repay the favour, or at least help someone in the future if I can get mine to handle as well as yours!

[malstc]

Hey Noddycar - Are you going to let it rev a bit more now??

I had a similar buzz from my header heat sheild - I put some washers under the bolts which didn't completely fix things but this gave me the confidence to let my 1.6 have it's head occasionaly.

I've always let my cars lope along to the point of labouring them. My na1.6 has taught me how to use the revs on offer. To me it feels like it wants to change at 6500-6750 rpm.

[DaveWA]

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Re: Simple torque/power improvements for NA

New postby nanotech » Mon Aug 02, 2010 2:40 pm

DaveWA wrote:Drop a LS2 motor in.....



Because that totally won't gimp the handling and weight distribution..

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nanotech
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Joined: Sat Jan 23, 2010 2:20 pm
Location: City of Greater Geelong, Victoria, Australia

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nope! approx 12-25kg heavier.... however not a cheap option

[Mr nanotech]

Woah I thought it would have been waaaaaaaaaaaay heavier than that! So what kinda moneys does this conversion cost and is it all usable power?