mx5cartalk.com

2000 NB8A 5 speed in immaculte condition without any mods. Full service history. Silver in colour.

I'd appreciate some constructive help with eliminating some of the NVH and finer tuning.

Using 98 fuel how far can the ignition be advanced ? I've read 14 deg ?

To reduce NVH ?
1) Brace across the car behind the seats.
2) front fender braces
3) 3 point engine bay brace between the firewall and shock towers ?

Use will be as a GT for long weekends away and a cruiser with the odd blatt on the back roads.
Is there any point in adding camber to the wheel alignment ? Front tyres are 80% gone so I can afford to experiment here.

Cheers

Code4 wrote:Using 98 fuel how far can the ignition be advanced ? I've read 14 deg ?

The NB8A is unable to have the ignition advanced as easily as the NA series cars.

On the NA series it was as simple as rotating the Cam angle sensor, on the NB the CAM angle sensor is fixed and cannot be rotated (it doesnt trigger the timing anyway, so even modifying it wont help)

The NB8A Timing is triggered from the crank angle sensor, right down near the front pulley on the engine, you can purchase timing wheels with slotted holes to allow you to adjust the timing, but it's nowhere near as simple as the NA cars.
You'll need to look into it, as I seem to recall that the timing wheels also affect injector pulse or something?

Code4 wrote:To reduce NVH ?
1) Brace across the car behind the seats.
2) front fender braces
3) 3 point engine bay brace between the firewall and shock towers ?

A brace behind the seats helps remove some rattles, but I've found the factory windblocker to be actually very good at that (granted, the flap part of mine rattles)

Fender braces supposedly do a good job, but i've not personally tried them.

Strut braces dont do much on an MX5, of the lot a 3 point will be the best, but I personally feel it's fixing the wrong area since most of the flex in an MX5 is futher back because of the gaping holes where the doors are.

Code4 wrote:Use will be as a GT for long weekends away and a cruiser with the odd blatt on the back roads.
Is there any point in adding camber to the wheel alignment ? Front tyres are 80% gone so I can afford to experiment here.

Just adding camber won't help handling unless your current setup and driving style are suited to it.

The point of camber is so that during a corner the entire face of the tyre is on the road and you are using as much of it as you can, camber helps take into account tyre flex so it flattens rather than tucks under.

An alignment is certainly worth the money though, but the specs really depend on what you're doing with the car.
My last alignment suited my driving up and down the mountains, but wasnt kind to the inner edge of the tyres when I was using the car for commuting.

from memory my settings were max caster, 1.5 degree neg camber front, 1.8 neg rear, and I think 2mm toe in? (can't remember the toe setting, but it's important to get right)

Code4 wrote::
Use will be as a GT for long weekends away and a cruiser with the odd blatt on the back roads.
:

The seats in the NB8A are considered the worst (ie. too hard) of all MX5 seats which you don't want in a GT.
If you can find some NB8B/C seats cheap, consider doing the swap.

I'm an MX5 Plus Roll Bar "fan-boi"; the built-in torque box really tightens the car up with regard to chassis twist (there's some debate on this but adding it to my SE made a significant difference I could feel even at slow speed turns). The roll bar provides added safety and looks good too but the additional chassis rigidity alone is worth buying the roll bar for IMO.

I've got Frog Arms fender braces too and they do minimise front scuttle shaking when going over corrugated surfaces but you can live without them (ie. if you have other things you want, you can buy the braces later).

The front strut brace has the most nay-sayers and your money is best spent elsewhere.

What are your shocks like?
If they're OEM you should get the struts serviced or replaced since by now they'll be knackered.

Some good pts, I'm learning. Was going to check the suspension was good first but didnt post that.

just like lokiel said the frog arms or the roll bar works well at stiffening the chassis. I have the brown davis roil bar on mine and it tighten it up immediately and when I added the frog arms it did the job even better.
too well in fact and I had shoulder pain from the heavier steering and could not go the distance with them. but if your in good health you will appreciate the benefit of both of the above add ons.
plus the delrin door bushes to hold the doors even more securely. I have not got them on yet but pretty close to doing it.

NVH is just a part of life with these cars, you'll never get high levels of refinement. However, you could look at:
Delrin door bushings - these reduce movement in the door pannel a bit. Do a search there are several manufacturers, reviews are mixed but mostly positive.
Dynamat (or equivilent) in the floors, boot, doors and parcel shelf - this will reduce pannel vibration. You could add a layer of Mass Loaded Vinyl over the dynamat stuff for added hush if you got really serious.
Tyres - as you aren't looking for huge levels of grip you should look at finding quiet tyres. I don't have any specific reccomendations sorry.
Windblocker - reduce the buffeting in cabin.
Suspension components - how many Ks are on them, what state are the shocks, springs and bushes? Any squeeking or knocking? Replace/repair/upgrade as nessessary.
Finally, hunt for anything loose! Find it, tighten it, maybe stick some rubber under it.

Things such as roll bars, fender braces, frame rails will tighten the chassis somewhat, maybe lessen a few creeks, they definietly can improve the ride and handling but I don't think they'll do much for NVH if that's your priority.

Lokiel wrote:The seats in the NB8A are considered the worst (ie. too hard) of all MX5 seats which you don't want in a GT.
If you can find some NB8B/C seats cheap, consider doing the swap..

It's more to do with the individual i'd think.

Personally I never had an issue with the standard seats in mine, even on long drives.

I found the NB8B seats to be rubbish though, far firmer, sat me taller, and generally just had the padding in all the wrong places.