I searched....
Ended up finding a thread that ended in flames with an na guy claiming 12's in teh 1/4....keep that out of this thread please.



ANYWAYS I have an 88 TII and and upgraded BNR stage 3 turbo with standalone, fuel mods, blah blah...pretty much everything is upgraded. Soo I currently have a 80mm downpipe that ends in 60mm which connectes to a 60mm midpipe then from there is the Greddy Power-back catback...it consists of the y-pipe leading out to two 2 1/4" pipes then to the resignators then the mufflers and out through 4" tips. I like the fact that it's quiet, but I really think this system is restricting my power a lot.

I have heard that single exhaust is lighter, but both should flow the same...I dug through pages of threads and none of them really had any info I could confirm..so can anyone reccomend any dual exhausts that flow REALLY well? I don't think the racing beat does... I was thinking one that has 80mm all the way back to a y-pipe that then had two 2.5" pipes going to the mufflers...or something ANYTHING that flows better. I don't mind weight, but if singles flow the best I'll end up buying a single exhaust system...just have to think about quieting it down. I know a local member has the SS autochrome with a Borla XR-1 welded on....I just want to go duals if I can, if not I have no choice but single.

(While we're on topic, does anyone know of a place that sells 80mm gaskets that connect the downpipe to the turbo?)

 

What are your goals? How much money do you want to spend?

Neither a dual or a single is superior to the other, in certain regards, but either can be inferior if executed impropperly. If you're on a budget, the most effective exhaust you can have made is a single exit. They're easier to make and require much less time. If you've got money to throw and time to waste, a dual can flow just as well as a propperly executed single exit...but it will require more time and effort and material to make.

If you intend to keep catalytic converters and baffled/chambered mufflers, it really doesn't matter which road you travel, just so you know.

 

Why do you personnally think that the RB system doesn't flow well enough for your application? And I think Mazdatrix has the Turbo-to-DP gasket that you're looking for.
-John

 

This is for my 350+ rwhp rx7...no cats, I don't want to make an exhaust as I don't even know how to weld. I can tell the RB doesn't flow well enough because it's 60mm to the catback...much like my setup. I want 80mm to the catback..then I want to hear ideas on the catback portion of the exhaust...and again I don't even know how to weld ....I was thinking of an exhaust that costs up to $600 w/o shipping.

 

Dual will be quieter for the same restriction, but heavier, more expensive, and harder to make.

 

You can have one built that'll be just as effective for half that.

Not necessarilly...

 

Any ideas then on piping sizing or anything? I am going to buy a 80mm dp and 80 mm mp though that take the stock cats positions...pretty much just like the ones I have now, but 20 mm larger. So piping sizing on the catback section?

 

Check out the RB Turbo Back exhaust, that meets your size requirements. That's the exhaust I've got and I absolutely love it. When I get my car tuned I plan to be in the 350 rwhp range too (running a LT8s and T04e). Personnaly I think that exhaust flows great and it's super quiet!
-John

 

You should buy the JIC Spec 90 "downpipe" and have a dual exhaust fabricated from where that ends if you want a really nice flowing dual for a reasonable price.

It is ~$250 from what I remember and it is all stainless, mandrel bends and has a velocity stack starting the size of the stock turbo outlet you have and then it goes to 80mm for the 1st bend and then 90mm for the rest.

Then get a GOOD shop to fab up the rest using a 3 1/2 to 3" Y pipe and two 3" inlet mufflers. Finding a good shop is the hard part.

I switched from the LOUD JIC Spec 90 single turbo back to the Racing Beat 80mm dual turbo back and the RB exhaust is a real restriction with its small piping and 3 cheated radius cuts/welds. RB killed the low end power by spooling so much later, but top end seemed the same.

I am now fabing the JIC Spec 90 "downpipe to a 3 1/2" to 3" reducer to the RB turbo back dual. It will be quiter than just the JIC Spec 90 and have much more low end than the RB.

Fabbing these to fit together should be very easy as the JIC downpipe is just a little longer than the RB downpipe/presilencer and the outlet is in exactly the same spot!

 

I don't know of any dual setups that are 80mm all the way back. Just get a big single. I am running the jic spec 90 so I am biased. I think a lot of people run a rb dp/ps combo and then from there run a 3" single catback of their choice. Be sure and check before you go quoting me. I believe I have read this but would do more research just to make sure. That would probably break your budget of $600 unless you go with the corksport catback. Check the for sale section. That's where I found my exhaust.

 

Single is the last resort....and a 3 1/2" exhaust...isn't that a bit overkill? haha I don't plan on going with a huge turbo for at least another 5 years...

-...might as well look, any links to the JIC spec 90?

 

I think the spec 90 itself was discontinued about a year or so ago.

http://www.hopupracing.com/jicmabuspcae2.html

That is a description of it. I bought mine used from a forum member.

 

Nick, you also need to remember how bad the SMOG ****'s are going to be in our area now with that new "Anti-racer team" that Sacramento has put in to effect. You don't want to attract too much attention to yourself bro. And you can hit 350rwhp with the exhaust you have now.

Zach

 

Good point, if there's one thing I love about that RB exhaust it's how quiet it is. My car doesn't get a second glance from the man....and I like it that way! Also keeps the ricer boys from bugging me. ;-)
-John

 

I'd never pass smog in a million years....Ben's car with the SS autochrome and a Borla XR-1 muffler is the loudest I'd ever want my car. Pretty much like the corksport with an XR-1 welded on...anything quieter than that ahhaha....I mainly wanted to stick with duals because they are quieter since theres a muffler on each side...I bet theres over 15 rwhp being held up in my full exhast, increaseing dp and mp diameter by 20mm and making a better flowing catback.

After looking at the racing beat I like the dp...how much restriction do you think the presilencer places on the exhaust? Would a borla xr-1 restrict less? I don't like the RB batback section..the pipes are so tiny...just like the ones on mine, except mine has 2 resignators which reduce flow even more.

 

Here's what I'm getting at. With 2.5" or 3" exhaust you can EASILY make 350rwhp. Hell you can make 450rwhp on a 3" exhaust. So don't worry about these details since they won't keep you from hitting your goal. I would recommend the Racing Beat exhaust though if you HAVE to buy one. Just trying to save you some money lil' bro.

Zach

 

If you're comparing single and dual systems that use the same type of mufflers and the same pre-Y section, the dual will be quieter for the same restriction. Each of the dual mufflers is only dealing with half the noise energy.

 

As you've said yourself, it's 100% dependant on build. Saying one is quieter is, in your words, "ignoring too many variables" to be 100% accurate.

 

Used RB turboback will flow well enough to put over 400WHP down. Some guys I talk to in the racer car tech say the turbo back from RB is well adequate even for single turbo(read TO4) cars. Your BNR Won't no what to do to clog up the flow of RB's setup. You can find RB setups for under 600 dollars used and still in beautifull condition, specially the new FULL SS version. One of the older units went for under 500 on ebay recently.

 

I have a stainless steel single 80 mm URAS N1 catback on my car.. I weighed it on the shop scale and I think it came in at 18 #'s.. that's light!

 

I didn't say that at all; what I mentioned was muffler selection. Build quality has little impact on sound level (unless it leaks, but I think we can set leak-free as a minimum standard). By far the most important factor for noise level is what mufflers are used. There aren't really any other variables to worry about. If you compare a system using two 2.5" mufflers to a system using one 3" version of the same muffler, the dual will be quieter. If you compare a system using two crappy N1-style mufflers to a system using one quality big-barrel muffler, the dual probably won't be quieter. This should all be pretty obvious though...

 

Used RB turboback will flow well enough to put over 400WHP down. Some guys I talk to in the racer car tech say the turbo back from RB is well adequate even for single turbo(read TO4) cars. Your BNR Won't no what to do to clog up the flow of RB's setup. You can find RB setups for under 600 dollars used and still in beautifull condition, specially the new FULL SS version. One of the older units went for under 500 on ebay recently.

You are missing the point. Sure a 2.5" or 3" exhaust can flow enough CFM for tons of HP, BUT a larger exhaust will still lower the backpressure and therefore increase the pressure differential accross the turbine exhaust wheel increasing boost response.

The larger exhausts spool the turbo much sooner providing better LOW end power, just what you need for the street. Just what you need on the clipped exhaust wheel on the BNR Stage3.

I ran everything from 2.5" to 3" to 3.5" on my BNR Stage4 and the large exhaust made a HUGE difference in spool though top end power felt the same on all.

I agree there is a point where tons of low end power with a VERY loud exhaust means less usable power on the street because you will get pulled over; whereas, a very quiet exhaust with quiet (usable) top end power can be driven harder on the street without notice.

 

Good points from everyone. I guess all this really boils down to is personal preference. I'm willing to sacrifice a little low end to have a quieter exhaust. If you absolutely must have the quickest spool possible then you go with the biggest, most least restrictive exhaust you can find. It's not really debatable as it is totally up to what each individual person wants out of their car.
-John

 

Good post, but the RB is rather huge as it is. The mouth of the inlet had to be deformed so that it could actually bolt on to an FC turbine housing. How much bigger can you go without going V-band/full turbo?



In any case I think he's missing a few things about RB's turbo back:


Its 80mm at the DP
The silencer is 80mm straight
the Y pipe is 80mm at its mouth
the outlet pipes of the Y are ~60mm(2.375")



So he's saying that he wants 2.5" at the muffler inlets/y outlets


He's talking about ~3.17mm's on each pipe difference. Now I understand that larger pipes will flow more fluid but who makes that kind of a turbo back that ins't loud as hell? Specially in duals, i've not seen any like that. If he really wants to have it flow and be quite maybe he can have it extrude honed the 3.xxx mm's ?

 

Oh how I love supercharging. Boost response is not dependent on pull-over gradient.