Simple torque/power improvements for NA

[Mr nanotech]

Any pics of your car? Should start a build thread if you haven't already!!

[Gordo]

Noddycar, it could be gear roll over? I have an nb8b and i have that rattle/ grinding sound at the same rpm. I did a quick search and found out all most all mx5's have it. From what I've heard its nothing to worry about, its just there is no sound proofing between you and the gearbox, so you hear everything going on down there.

[Noddycar]

Not sure what the cause is... I drove it into work this morning and the noise eventually returned. As it was too early for Mazcare, I thought I would take it to our company mechanic while the noise was still there. He got in - the noise disappeared. I drove the car back to work and it reappeared....

He was talking possible gearbox noise, given my description of the sound, but he said it could be a hundred different things (like heat shield/cat etc). I will keep driving it and if it re-appears consistently, will take it to Mazcare for a look. The mechanic this morning told me NOT to install a CAI.... Another opinion. I am only a little confused....

He did point out my rear suspension seemed a little softer than the front, so there is another job....

[Guran]

Sorry for the OT post, but I couldn't help but wonder if you could use this image as an avatar?

[Guran]

Back on topic ...

That vibration/rattle is definitely something you should get checked out. Doesn't sound normal to me. Being forced to change gears below 5000rpm is something I couldn't live with in my NA6. Of course, I run at lower revs for constant speed cruising, but mine regularly lives in the 5000-7000rpm range for "spirited drives", and the sound is truly glorious.

[Noddycar]

Hi Guran

Great pic!!!! I was intending to use a photo of my car, but you may have changed my mind....

Yes, the rattle is a pest. Impossible to diagnose unless it is actually doing it when it goes to the mechanic. I will just keep driving it around and if it starts, will drive it straight into Mazcare... I feel stupid when the mechanic drives the car and it disappears, but that's life!

[GP14]

The mechanic this morning told me NOT to install a CAI.... Another opinion. I am only a little confused....

If your in 2 minds i have the Loch Stewart CAI. PM me and you can see the difference for yourself. Which side of Brisbane are you?

[bruce]

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

[Noddycar]

Hi GP... I am Southside... I assume you are firmly on the "improved my car" side of the argument?

[GP14]

no just giving you the opportunity to make your own mind up without people saying what you should or shouldn't do. I am also south.

[Noddycar]

Thanks GP14

It would be good to see these systems before I stick one on my car..... I will be away this weekend, but will send you a PM next week to see if I can grab your contact details. I appreciate the offer to see yours. Unfortunately, I think I am starting to get a little obsessed with the little red car!

[Mr nanotech]

I was thinking about this today and I remember I too had a vibrating sound coming from the front of the car.
It seriously pissed me off for ages having to hear the gvrrrr noise of something metalic buzzing. I'm not sure if you checked this but I can tell you first hand that mine was the heat shield. You can live without it. I mean, some people will tell you that you should keep it on but to be honest I don't see it making a huge difference to performance.
But if you take that off, you'll know straight away if fixes your problem, it's just a straight bolt on item so I think if you get a 14mm socket you should be able to happily pull it off in 5mins and cruise down the road. If the buzz is still there, that wasn't your problem.
Also try tightening the heat shield if all else fails. The other thing I'd look at is your manifold.
Mine was cracked so I could hear the buzz from that too, so just be weary. If it's the original pipe from 199- it's time could be up. Try tightening the nuts once you have the shield off though.

Other than that, I'm not sure what else would be causing the sound so I'd be inclined to see the mechanic like you mentioned before. If it's exhaust related it could even be your cat. I haven't heard the sound so I'm just speculating here. But i've heard a dead CAT before and it's not pretty, it's a dodgy buzzy vibrating noise.

But the main reason I'm thinking it could be the heat shield or manifold is because you say this only happens when you push the motor harder. I'm guessing when you give it hell and start revving it, the engine is rattling and causing what I said. Anything is possible and I'm just guessing here but I hope it's some help to ya!

[Noddycar]

Thanks Nanotech

I will definitely take a look at this on the weekend. Murphy's Law dicatates the noise will disappear when I drive into a workshop, so I may need to find it myself. It is a hard noise to describe, but someone else had a similar noise and described it like your gearknob was vibrating loose. That's the same as mine, but it is probably a completely different issue.

[Noddycar]

Fingers crossed, it looks like the rattle is gone. I removed the heat shield last night. It looked fine, but one of the bolts was not quite as tight as the rest. I hope that was the cause, as I re-fitted the heat shield and the rattle is gone. I noticed when I re-fitted that the top bolt was slightly offset from its original position, so the heatshield may also have not been seated correctly (unlikely, but who knows - there is a little bit of wiggle room on the bolt holes before they are tightened).

Thanks again for the advice everyone.... Hopefully this was a win!

[Noddycar]

Hmmmm. So much for that! The noise is back with a vengeance. I can't seem to isolate it when the vehicle is stationary, so I may have to replace the heat shield and take a punt.... I expect that as the noise did go away for a while after taking this off, it will be the heat shield.