MX-5 Miata Forum - Too header or not ! (2024)

He's right about 99-00 having an ugly, heavy, inefficient header. Get a header and a TrackDog blanket for it to prevent it from cooking the brake master cylinder.

For spirited response, a Fidanza flywheel also helps a lot in the first three gears.

The combo of a good intake, 2.5" exhaust pipe, and the above two items make the NB feel like an ~180 HP Miata.

The first thing I did to my (non-California model, thank god) '00SE was to replace that agricultural cast iron header with a Racing Beat stainless steel, four-into-one, tubular header. Not only did it fit like a dream and improve the underhood appearance tremendously, it also (probably) resulted in at least a little better efficiency. I didn't do any dyno testing and my butt dyno isn't sensitive enough to tell any difference but, it certainly gives the impression of working great, even if it makes no difference at all. (I'm not using the car for competition of any kind).

It was well "worth it" to me, even if just for the 'eye candy' value alone. I also installed a set of red Racing Beat ignition wires and it makes the little NB look really good. I haven't noticed any problems with heat or radiation damage to other underhood items, even though the headers (which do take up some room in the engine compartment) don't have those tin heat shields like the old cast-iron collector did.

I've been considering adding the RB stainless muffler and twin tail-pipe assy too, but I'm concerned that it might add to the noise level. I kind of like the sound the car makes now and don't really want it to get any louder in cruise.

Louder... Perhaps... But not much louder.

I haven't noticed a significant difference in mine from the co*ckpit, at least not when it's not running at "full thrash".

When at cruise power, I notice no difference in sound at all.

But, it looks rather handsom when you pop open the hood.

It is certainly louder, it is not...IMHO anyway...an objectional louder.

The increase in soound volume is almost all in the low bass and is only really noticeable under hard throttle.

It also helped eliminate the annoying 3500 RPM drone the car makes stock.

It will be louder, but a symphony is louder than a barking dog also. I like it, and for many more reasons than sound.

LWW

i have a 99 CA car with the intergrated converter *shivers* , but i replaced mine with a OBX unit from ebay. Before installation i wrapped it wit hheat wrap. I also have JRSC. Before the header, i was runnign 5-6psi, normal. After the install i was running ~4psi because i freed up that much restriction! I later added a BBK crank pulley to get back to 7-8psi.

But, the header is well worth the $$$, especally if you're planning to go with a supercharger. Unfortunatly, my S/C was installed before the header, so when we did the header, we had to remove the S/C!!!!

A question/comment for our distinguished moderator. Isn't a 2.5" exhaust simply too large and will result in insufficient exhaust velocity? My handy-dandy flow calculator (produced by a reputable exhaust manufacturer) shows that a 2.5" exhaust is not req'd until HP production is somewhere in the region of 200+ HP.

I figured a correct step up from the stock 1.875/2.00 w/b 2.25", unless of course I was contemplating a supe/turbo mod. My comments assume use of a normally aspirated motor.

Panos mentions "a good intake", and I've heard a lot of people say "don't bother with an intake". Just wondering what constitutes a good one. I've been trying to tally up a nice dream list for my '00 and so far it entails: header, exhaust, and flywheel. If a good intake would add a few hp to the header and exhaust, it's worth my contemplation.

Thanx in advance.

I have the Monsterflow. Past discussions credit it with up to 3 HP. Results for headers vary between 6 to 12 HP. Exhaust (muffler only), 2 to 5 HP. So mine may have a "base" improvement of 10 HP (never dyno'ed.)

The header and the flywheel made the most detectable difference.

The car with the setup I described above (and a completely stock engine) is very fast, and reasonably torquey, in both autocross and open track.

In any race I work the engine very hard, pretty much staying in the 6000-7500 rpm, so the large exhaust pipe likely helps.

The RB Powerpulse exhaust I got may not provide a consistent 2.5" of equivalent tubing diameter. We simply don't knw what restriction is there.

By the way, the RB PP has been on the car for exactly 6 years now. A true OEM quality (or better) part.

You won't be disappointed.

For me, installing the unit was easy except for loosening the bolts at the engine/bell housing that are also used to mount a bracket that holds the original factory down-pipe. I had to go out and buy a longer breaker bar to do the job. Everything else went textbook easy. I haven't seen any Racing Beat parts that don't fit well and look extremely well made.

According to their 'unbiased' web site data, the RB four-into-one header added about eight (8) horsepower (starting around 3,500 RPM) to a stock '01 model (which already has a tubular header) with no other mods from what I could tell. While I find that to be amazing to the point of being sceptical, I'm sure that it would do more for a '99-'00 model with the cast-iron collector than it would for the later cars.

But, even if it don't help power much, it certainly adds to the 'look' of your engine.

That too is part of the MX-5/Miata experience.

BRADNESS:
i agree, i have read many places that a 2.5" exhaust is too big for a n/a engine or even a Supercharged engine. from my readings 2.25" is just right for these applications.

now the 2.5" is good for a turbo system

I believe the RB header documention recommends that anyone putting a header on a "California model" mount the rear O2 sensor in a place where it is connected (wired up) but not installed in the exhaust stream.

That way, while it don't actually do anything, it is reading a 'cleaner' value than the front one that is in the exhaust. That isn't legal in California, I suppose since it might even be possible that the 'free stream' O2 sensor might then be in 'dirtier' air than the front sensor inside the exhaust stream. ;)

I've got a 2000 with a JRSC. I'de like to add a header and from what I've read, the OBX was a Racing Beat knock off and the Racing beat doesn't fit with the super charger. What if any fitment problems did you run into with the OBX header and the Supercharger?

I don't know but the answer likely exists in the POWER forum.