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Okay,
So I need to know if the headers from an NB8B will offer any improvement to my NB8A, and if they will require any modification to fit.

1x (seriously - aslong as your in Vic ) for anybody that can answer the question.

Thanks!

I'm 99.9% sure the answer is no they wont but I'm sure you'll get a response with a definite answer. I'd be surprized if there's any difference in the 8A / 8B headers anyway. From what I've read the NB8A headers are very efficient and swapping to expensive after market headers only gains you about 1KW which isn't very good value for a cost of about $460 ! You're much better sticking with your factory headers and going for a stainless hi-flow cat and hi-flow system from Town & Country Exhausts in Geelong on which you'll find heaps of reports here in the forum.

Cheers,
Toymx5

Cant be. 8a headers are longer 8b there must be some difference.

Even the cat is moubted further back.

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You are correct slimx, I'd forgotten about that. Do you think they are any better though, would Mazdarati gain anything from fitting them ?

I have had both of them side by side and they are exactly the same, with the exception of the O2 sensor location. It is located further down on the NB8B headers.

I think the difference comes mainly from USA based forums.

I think the US had much different headers to us on their NB8As (perhaps an integrated cat?)

hks_kansei wrote:I think the difference comes mainly from USA based forums.

I think the US had much different headers to us on their NB8As (perhaps an integrated cat?)

I think you are right. I am sure I saw a picture that shows the cat mounted in place of the down pipe.

Great thread - exactly a question I've been trying to answer.

I asked Dave from Carco in Canberra and he said almost exactly what toymx5 said:

toymx5 wrote:the NB8A headers are very efficient and ... [y]ou're much better sticking with your factory headers and going for a stainless hi-flow cat and hi-flow system from ...

That said, Dave was big into recommending a 2.5" exhaust system on an naturally aspirated car. The view on these forums seems to be that 2.5" is good for turbos, but that 2.25" is right for NA cars (unless there is serious engine work warranting the larger system).

I've not upgraded anything because I'm terrified of having a loud droney exhuast.

what do u mean side by side there the same.

I have both side by side now ..

8B header is atleast.. a good 20-30cm shorter then the 8a.

Perhaps the "KW gain" is from America. Sorry mazdarati i think it only applies to the USA models that. Im prety sure i read that somewhere on miata.net maybe ..

slimx wrote:what do u mean side by side there the same.

I have both side by side now ..

8B header is atleast.. a good 20-30cm shorter then the 8a.

Perhaps the "KW gain" is from America. Sorry mazdarati i think it only applies to the USA models that. Im prety sure i read that somewhere on miata.net maybe ..

Iam pretty sure that on a couple of models where we had the tubular(NB8A and on )and better headers the US had cast for some reason I cannot recollect,but have read on the big forum.Their NA8 had tubular and we had cast from memory.

None have problems fittiing at the head but there are different manifold lengths and cat placements,plus the NB8B (or C?) has a secondary oxygen sensor towards the rear of the midpipe.

Probably not much to be gained by using the US forum feedback in this case.
Peter.

I have a AUDM NB8A and NB8B manifold downstairs which I just checked right then. Both are tubular rather than cast but the 8A has an oxygen sensor at the two secondaries and the 4 primaries look slightly squashed like they were press bent rather than mandrel like the 8B one. I'd say the 8B would be better but not by an awful lot on a stock motor.... 8A manifold is still on a motor about to be built so I didn't bother pulling it off and measuring. They look very similar length though. The 99-00 American manifold was cast I believe but not the 01+ and that is the manifold to be replaced for a good upgrade. Google will show you many of them if you go searching.

Thanks to all for your help...I'm kinda disappointed lol was looking forward to playing around in the engine bay!

hks_kansei wrote:I think the difference comes mainly from USA based forums.

I think the US had much different headers to us on their NB8As (perhaps an integrated cat?)

Yeah the US had a cast manifold on their early NBs (I remember sending pics of my exhaust to FM at the time).

Side note: The Japanese NB8A headers seem to be identical to the Aussie ones but without the ERG.

I forgot to mention the heat shields mount slightly differently on them both so aren't interchangeable.