ive searched and nothing much on it.

i have a 91 gxl....stock everything. i was planning on:

-high flow cat (bonez)
-catback system (borla)
-replacement filter (K&N) with the stock airbox drilled out like Icemark
-headers ...if needed (custom)

or

-racing beat true dual system
-replacement filter (K&N) with the stock airbox drilled out like Icemark


question: which will get me more HP?
question: which will is the better suggested route to take?

any other suggestions bout this r appreciated.

 

I'd put money on the true duals making more power. simply vecayse a cat is retrictive and the true duals have none of that. But you whould know that Racing Beat doesn't make that setup, Mazdatrix does.


Santaigo

 

Mazdatrix makes it using RB parts. RB header and mufflers, but I'm not sure about the presilencers.

 

The pre-silencers are from RB aswell.

Santiago

BTW incase you two don't know I own true duals.

 

The true dual exhuast will make more peak power, but *GENERALLY* makes less HP below 4000 RPM on a STOCK port motor. The true dual exhaust will make the most power with a ported engine.

The Highflow cat and Borla catback will give you more HP than stock throughout the RPM band but with a lower peak HP number than true duals. Why? Backpressure.

The real question is: How loud do you want your car? The true dual setup is very loud. Many people like it, others think it's obnoxious. To each their own.

 

Can I have some of that weed?

I thought this myth was over already. geez

Ok here we go again: The True Duals make more power everywhere. They are the best for a non-ported engine and are still great for a ported engine. The True Duals still have the aux ports functioning so they have just as much pressure as the cat. And there are way more than one sound clip of My car and another member's car with true duals both are not loud. If you take a listen to something like N1's or the CS cat-back on an N/a they are way louder so please do not say they are loud because I bet if you take a db meter to each on the same car they will be a lot quieter than most other exhausts out there. Oh yeah and uh why would we want peak power below 4k? The stock peak is at 6500 with true duals the peak is at 7k(S4 numbers) What better place to have it than at or close to redline?

Santiago

They have a dyno graph on the site. check it out. Its layed back to back with the stock dyno run.

 

My NA had full duals.
Duals do not really require tuning to work well.
Plus they sound cool.

Check out the links in my sig..

 

A lot of what you said is your opinion.

True duals open up the exhaust completely. We agree on this. When the exhuast is open and free flowing, there is zero/very slight back pressure. This is bad for low RPMs. Why? Because during low RPM operation, backpressure keeps the combusting fuel in the engine longer. Thus more energy is exerted onto the rotor face. Hence you get more power down low when you have *SOME* back pressure. True dual dyno graphs usually show less torque below 4000 RPM. However there are always excpetions depending on the condition/porting of the engine.

As for the volume of true duals, each person has their own *opinion* of what's loud. I just wanted to make sure that the original poster was aware that true dual exhaust on an NA is way louder than stock.

 

FOR EXAMPLE...

Lets take a look at two recent dyno posted on the forum:

Here is RarestRX's Dyno: (True DUAL exhaust)
https://www.rx7club.com/attachment.p...postid=2552379

And here is Icemarks: (Stock manifold and single)
http://www.mazdamark.com/FCDyno2.jpg

IGNORE THE NUMBERS and LOOK AT THE SLOPE of the torque. Notice anything? Single exhaust has peak torque before 4000 RPM. The Dual setup hits peak at redline. It doesn't look like a "Myth" to me!

 

All I see is gains I don't see it dip below the stock dyno run's line.

And I didn't say anything about oppinion I said that if you take a db meter it will likely be way quieter than the other exhausts people use on N/a's which are usually N1's, HKS, or CS which are all basically fart cans. The True Duals have back pressure otherwise they auxilary ports would not work but they do. The true duals are only noticably louder than stock under WOT which is to be expected.

Santiago

 

Save your money, true duals is not worth it. You will add a boat load of weight with those two heavy *** presilencers and RB's mild steel construction. The extra power you make with true duals will be just enough to push that extra weight...LOL

Seriously though, the extra piping makes the car a pig. I had a GTU's with Greddy's PE exhaust and I smoked some 7's that had true duals. My opinion you should use the extra cash to buy an aluminum flywheel. The key to an NA is how much weight you can remove.

 

First off your comparison is a stock ported(RarestRX) to a Ported(Icemark) engine. You can't say that this has nothing to do with tourque and horse power curves. And I don't see where RarestRX's tourque peaks at redline do you? I just see a normal flat curve of tq and a lot of power from 7k-8k rpms Your wording is very deceptive first your tell people to look at the Tq number's and then you talk about peak power which is HP not Tq.

 

This graph only shows HP. Where are the torque numbers? Also, I never trust a manufacturers claim. Take a closer look at real world dyno runs...

The key word here is "likely". IE: Opinion.

 

Opps. I was looking at the HP number there...

 

RB uses SS for their Canisters not mild steel. The piping is mild steel but that is made by Mazdatrix. And compared to the stock bricks it isn't heavy not does it make the car a pig. Your comparison of your car to another car is bullshit. You can't compare one car to another like this. You can only compare different things on the SAME car with no other changes to maintain things scientific. Btw I have beaten my friend in another FC with collected headers/silencers and Magnaflow muffflers which are "light weight" which only helped him make the thing louder and slower. Therefore this disproves your "story"

 

Well Since noone else has made before/after dyno runs we can't say they lied or not.

And I used "likely" because I don't have access to all the exhausts on the market for N/a's but I have heard and compared many sound clips and Have heard more than a handfull of other FC's with various canisters.

Likely:Possessing or displaying the qualities or characteristics that make something probable.

 

First off junior, I was refering to the presilencers which indeed are made out of mild steel. And yes, the rest of the piping is mild steel (same thickness as RB) As far as comparisons go, Ive owned 4 Rx7's, 3 of which were FC's. I think I can safely say after 7 years of experience with them what works and what doesnt. The only thing mild steel is good for is quieting down the exhaust. BTW - A mild steel exhaust better be coated with something or it will be a rust bucket in a year.

Edit: dont mistake chrome presilencers for stainless steel numb nuts!

 

So in 7 years you have bought everything available? I don't thinkso grandpa. You might have some experience but you can't say this works and this doesn't. Because infact you do not know everything! No one does and no one ever will. My True duals aren't rusty at all. They have a bad *** coating on them. They polished up to brand new. I have some pics of that **** before and after cleaning. Still shines. And why would a different type of steel quiet down anything? Its just a pipe that doesn't have any muffling capacity. I didn't condone them using mild steel for it but SS would only add in to cost. And other company's use mild steel for cat-backs. APEXi N1's anyone? Jame's N1 Duals are ugly looking the cans are ok but the pipe ain't.

 

I didn't say anything about the pre-silencers. ;]

And they still shine. cept for the part I hit a rock

 

The reason they use mild steel is plain and simple, its cheap! I didnt say that a different type of steel would help to quiet it down. There is a two fold reason why RB and mazdatrix piping is so thick. It helps to take the T'ing out of the exhaust note but more importantly, they make it thicker because it will last longer that way.

 

Ok so you want to sacrifice weight at the expense of durability? If I had a huge budget and the car didn't see over 30k miles a year I would buy thin exhaust pipes. Oh wait then it would sound like ****.

 

No, I have stainless, so I didnt sacrafice ****

And this discussion is regarding NA's, my car is a turbo and is much quieter.

 

N/a to Turbo II comparo's from a sound/volume perspective is apples and oranges.

 

Here we go again the great N/A exhaust debate. Between Kevin and I we have almost had or driven all the major possibilities of exhaust systems. Here is my analysis

1 - Stock manifold, Bonez down pipe pre-silencer, HKS 50mm cat back. Good down low and midrange power. Medium weight combination (only because of the manifold). Good exhaust note little to quiet for my taste, super loud shot gun back fires!!
2 - Stock manifold, Racing beat down pipe-pre silencer, HKS 50mm cat back. Good midrange and top end power (but still not 100% up near redline). Heaver combo than the one above but not by much. Louder/raspier exhaust note, sharp crisp back fires.
3 - Stock manifold, Bonez down pipe pre-silencer, Racing Beat cat back. Just about the same as the first one except the exhaust note is louder and the Racing Beat is heaver than the HKS.
4 - Stock manifold, Racing Beat down pipe pre-silencer, Racing Beat cat back. Good midrange and top end power. Heaviest set up out of the 3 set ups above. Good rotary sound, poppy deep back fire sound.
5 - Racing Beat streetable header, Racing Beat pre-silencer, Racing Beat cat back. Good all around performance. Lightest system so far due to the removal of the cast exhaust manifold. Good “loud” rotary sound but back fires are now gone
6 - True Dual system w/Racing Beat components. Insane upper midrange and top end power but bottom end and off the line power suffers (I would suggest to any one that gets this system if they have there 6th ports tied open to fix what ever is wrong and make sure they work cause you will suffer even more lower end power loss). Heaviest system out of the bunch but damn does the under side of you car look BLING BLING. The best exhaust note out of the lot of them. Deep clean idle with small blurbles resonating from each rotor, that signature weed whacker on crack sound up top!!

I LOVE the tue duals, but it is expensive a little louder, and a bit on the heavy side. If you don’t have that much cash and want to keep your car on the light side I think system #5 is your best all around performer.

- Dana “Damn, Team GTUs goes through a lot of exhaust systems!!”

 

No ****!

Listen all you perspective true dual exhaust buyers. Mazdatrix sells the true duals for 1,250.00!!! Thats a **** load of money for a mild steel setup. Im biased but take a look ...

http://www.jic-magic.com/productsjic_bullet_twin.htm

This is a nice stainless exhaust with a deep tone. Its 1,180.00 for the catback but im sure you could find it cheaper.

Then you have the Greddy PE...

http://www.rx7.com/cgi-local/2catalo...at=11&part=130

Ive also heard this tone, a little louder then the JIC and not quite as deep. Its 898.00

Then you have the Apexi duals...

http://www.rx7.com/pics/fc-apex-dn1.jpg

This is probably the loudest of the 3 but you can buy it for $719.00

There are little details about the apexi that I really like. For example, has the ground cable at the rear of the bumper (like stock) It has silencers if needed to quiet down the car for daily driving. I realize that for 1,250.00 you get the header and presilencer but there are other alternatives out there. You could make a test pipe for practically nothing.