celbii

iTrader: (2)

The exhaust on the na s4 I just picked up is hacked together, and of course the 5th and 6th aux ports tube is just hacked off and hanging. I have a friend that will make me an exhaust, all I need to do is pay for piping and other materials.

I was thinking of getting the Road Race Header for 86-88 RX-7 - Racing Beat Racing beat road race headers, for their true dual setup, as it already has the pickup tube and 02 installed and ready to plug and play.

1)So a few questions, since I'm clueless. Obviously from what I've researched, a system that has a tube in place, but has all the cats removed and is essentially a straight pipe setup, wont have enough back pressure regardless to operate the 5th and 6th ports. However this racing beat setup should work, even if straight piped after the header, because the pickup tube is facing the exiting exhaust gases, therefor working off the exhaust pulses instead of the backpressure?( Is this correct, and if so does this open the 5th and 6th ports the same as it would operating oem?)

2) So say that this header will allow me to use the 5th and 6th ports again, I would like to just pick up the matching flange from RB, and then convert that dual exit into a single 2" exit out the passenger side, exiting a muffler, and possibly with a resonator(Is this worth it?) in the middle for some noise control. Is this whole idea a waste of time, and power loss etc, going from their dual header to a single exit instead of making a dual exit? I don't think it would be the end of the world if it was worlds better to go dual, but that would just mean more money in materials, another muffler etc. http://www.racingbeat.com/RX7-1986-1...ges/16197.html

3) Last question, it says this header is 2", it seems like most are. I read alot of people going 2.5" on NA. Would that make a difference getting this 2" header, the matching flange has 2" opening also, and welding 2.5" pipe to it? or would it be better to just make the exhaust 2" back? Any difference at all really?


Thanks for taking the time to read and answer! Hope I don't sound too dumb!

misterstyx69

iTrader: (142)

just use the collective header,not the road race header.There is no sense in having a 2 pipe header,and essentially making a collector when you can buy a header that is complete already.

celbii

iTrader: (2)

Yes that makes sense to me, are you talking about this one? Streetable Header for 86-92 RX-7 NT - Racing Beat My only thoughts of using the Dual is because it already has the pickup tube installed.

On an unrelated note, just curious, does it matter at all that they recommend this header for a carb setup instead of FI?

Thanks!

misterstyx69

iTrader: (142)

No idea on Carbs.(almost typed Crabs..no idea on those either..lol!)
The old street header had a tube to hook up to the actuators,the s5 version didn't.I'm seeing no pick up tube on the new style.

Now,I had a setup and the header had a tube installed right where the collector joined the two pipes at the end near the rear flange.
You could do the same thing really with a drill,a tap,screw in fitting,etc and make your own pick up tube location.
It's a thought.

celbii

iTrader: (2)

I thought about that but I was under the impression with a straight pipe type setup, the only way the 5th and 6th ports would open with the RB header was because the pickup tube was located so the exhaust was flowing/pulsing into it? Where as a fitting just screwed into the exhaust as ive seen in a picture earlier wouldnt do the same thing?

archaphil

iTrader: (1)

im running the streetable (single collector) on my s4 NA to a modified stock cat and stock y pipe/mufflers. Works nice, and noticeable power increase as well.

the stock pickup tube for the aux ports from factory is on the cat. and as long as you are not doing anything silly like throwing a 3" straight pipe exhaust on our little wimpy s4 NA, you should have no issues with back pressure opening the ports, should you choose to fabricate your own pickup tube

misterstyx69

iTrader: (142)

The presilencer from Racing beat has a pick up tube on it.
If you have an Old cat you can also "punch it out" and use the body of it to utilize the pick up tube too.
Doing the "collective Tube" thing that I suggested should also work fine.( did on my NA).
The actuators do not need a heck of a lot of back pressure to activate and the best ares is at that collector.
You can also make a section to hold a tube,like the cat or presilencer.

Another idea is RPM switch activation.(look that up,too much to type!)

celbii

iTrader: (2)

The car right now doesn't have any of the precats or main cats, they were already cut off when I got it. It is a Frankenstein exhaust the P/O had put on it since the old one fell off.

I was planning to go from the 2" headers, to 2.5" all the way back to the muffler. Only reason I didn't want to get the street header was since I would then need to spend another $300 on top of $300 header to get the pre silencer with the pickup tube. It seems easier to get the road racing header with tube + flange, and just make a collector at the flange for the rest of the 2.5" exhaust to a single exit on the passenger side.

So I just wanted to see if this was worth doing at all and if I did it this way it would still open the aux ports, despite basically being a straight pipe(muffler).

And I've read about RPM switch, but if this way works I would rather do that. I've also seen the analog way which I may just go ahead and do that since It seems simpler than getting the RPM switch and all the other goods and setting them up.

archaphil

iTrader: (1)

I picked up my streetable header for $50. WTB thread in the FS section will get you all you would need. hell I have seen guys pick up full RB N/A exhausts in the for sale section for $500 plus shipping. RB stuff is great, even used.

celbii

iTrader: (2)

From alot of reading I've done it seems even the RB pickup system isnt that accurate, so I may just bite the bullet and make an rpm switch, or do the analog method to open the 5th and 6th ports.

That said I'll just keep a look out for a RB header with single exit. So going from 2" collector exit to 2.5" for the rest of the exhaust shouldn't have any negative consequences correct?

Thanks All

RotaryEvolution

iTrader: (30)

they recommend it be used with a carb because carbs can flow more on the top end versus the stock manifold, taking more advantage of the overly large exhaust area which is more for track use and will lose bottom end response.

a collected header will give better all around power.

if the intake won't flow at high revs and the exhaust is made for high flow then you have a mismatch and might lose more than you gain.

bigger isn't always better.

Evil Aviator

Woohoo!

See the Racing Beat exhaust Tech Tip in the below link. Their Road Race Header is actually a little too long for an optimal Short Primary system, but your friend could build a pretty decent Long Primary system by following the sizing guidance. I had a Long Primary system on my 1Gen RX-7, and I really liked it.
Rotary Tech Tips: Exhaust System Configurations

I'm not sure how the Road Race presilencer would work with a Long Primary system, so I would contact Racing Beat to see what they think. If you search the Racing Beat website for "presilencer" you will see more options.

Here is a good example of a custom Long Primary system:
http://definedautoworks.com/prod2_1.html

I would trust it to operate the ports if Racing Beat says that it will. I'm not sure how it would affect aux port timing, if at all. This would be another good question to ask Racing Beat.

The 2.5" OD sizing is for after the point of collection.

I disagree. The Racing Beat Streetable Header is sized for easy fitment as opposed to maximum performance. If the OP has access to free or cheap fabrication, then there isn't much point in choosing the easy route over the optimal route. He could have the whole system designed for racing, with a slip joint and attachment points at the rear that allows for quick-change between a muffler for the street or a megaphone for racing.

Dak

I too would go with building a custom long primary system an Evil Aviator mentioned, and would like to do this myself one day. I think you will need some sort of pre muffler/presilencer setup as well as the main muffler or it will be way to loud for the street. Some even have trouble meeting sound at some race tracks with these cars.

celbii

iTrader: (2)

Hmm this long primary system does indeed look interesting if hes up to building it. I was planning on just going straight pipe to a muffler, but something like that I think I would consider some sort of premuffler or silencer just to quiet it down a bit more lol

Evil Aviator

If you look at the 1Gen RX-7 "Street Port" full exhaust systems on the Racing Beat website, you can see that they use two staggered presilencers leading to a single muffler. This configuration is fine for a street car as long as you use rotary-friendly components (Racing Beat, Apexi, GReddy, Rotary Performance, etc.). Don't use Flowmaster, Cherry Bomb, or other popular muscle car components that are not intended for rotary engines.