rxspeed87

going to go with a true dual system on my 87 sport

curious as to what I should use as the muff though

N1 uni with a 2.5 core
n1 uni with a 3.5 core
or apexi dunk?

any ideas on which would give me the most power
would the 3.5 core be to large for an N/A car ?

RX-7 GT

yes i think the 3.5 is way to much. especially since you will x2 it. most n/a dual exhaust anyways stick between 2.25 and 2.5 if you had a turbo then its never to big

go with the n1's they are cheaper

Node

iTrader: (1)

A POTATOE

Turbo Timmy

fastrotaries

Sorry Dan Quale....oh i mean NODE.. it's P-O-T-A-T-O..
I think the 2.5 are just fine. My friend has a full 3" and it's overkill on his N/A. He'd definitely win a dcB contest

gxlbiscuit

i myself prefer some crack in my pipe

Agent_D

iTrader: (2)

X-TEC

www.xtecmotorsports.com

i like those

gonna stick an N1 uni on my friends AWD camry in a few weeks.

pineapple racing

An unmodified n/a , in my experience, makes the best power on the dyno(all around) with 2 1/4. We run p port motors on dual 2" pipes through racing beat presilencer, walker super turbo (2") on cars like rx3's with limited space. Paul Robinson's runs almost 107 mph through this. His car is not loud either and is a full street trim ride w/ road race susp. Don't over do the pipe size on the n/a. The idea is to keep the exhaust moving as fast as possible with out being restricted. The exhaust is like a train, the faster it is moving the better it "sucks" the exhaust out of the engine. At slow exh. speeds, the "momentum" in the exhaust is lost on the flow wandering around. Next time you are at the road race track, check some of the faster cars. Most bridge port motors will run dual 2" primaries w/ 3" muffler(Darryl Drummon-a #1 nice guy and great builder likes 4" muffler) single tail pipe. The primary pipe size is usually 2" o.d. for the 13B. This is on a full race motor that will never see less than 7500rpm on the track. Do the math, sq. area is the important #. A refresher for those that forgot, area of circle= pi(3.1415)x[(radiis)(radiis)].Rob

FPrep2ndGenRX7

Rob has spoken. We must listen and learn.


I'm not worthy! I'm not worthy!

Audiofight

That's the info I needed to hear.

I have been wondering how big I should go with my exhaust.
Dual exhaust setup, 2" pipes to 3" mufflers.

Thanks alot Rob.

the krza

...some of that good leftöver crizack

MaxRX7

a banana

don't get a pipe with diameter over 2.5" unless you plan to boost in the future

mazdaspeed

I am going to put exhaust on my 88 Convertible i see you have a header and a pre silencer. Is that a better choice than a downpipe i heard that it is really loud? Did it make a big performance improvement.....basically is it worth doing?

turboren

Actually, pi is 3.14159...... (round up to 3.1416)



Good info otherwise, thanks.

Ren

rxspeed87

I was thinking of running the 2 inch pipes off the dual out header and then before the muffler put it out to 3 1/2 since they dont have a 3 inch N1 muffler

but I dont want to run 3 1/2 inch all the way b ack
kinda think the 3 1/2 would give me a nice deep *** sound that would be loud and since it is further down from the motor I did not think I would lose that much low end torque

avrfan

Rob,

2 1/4" isn't that the same size pipe used on the stock 13B NA's? So I guess Mazda knows best too as far as pipe sizing goes.

What about sound quality. Does anyone know how pipe diameter affects the exhaust sound? Does large pipe give a lower tone and smaller pipe higher freq. sound?

Dave

Felix Wankel

Maybe 2.25'' OD counting the heat sheilds and all. I had a dual 2.5'' ID on my NA, and it was too big. The 2.5'' looked alot more than 1/4'' OD bigger than the stock stuff. It almost felt like it slowed my car down in the low end. I think 2.25 would have been perfect.

NCsublime

I agree. I have the larger N1 dual, and it cut my low end down quite a bit (keep in mind I'm speaking from when the exhaust and intake were my only mods). I'd stick to Rob's advice and wouldn't go any larger than 3" if you can help it.

-Derek

avrfan

So I guess just to confirm things, ideal pipe sizes are:

[2" for dual exhaust on NA's regardless if its stock or ported engine]
[2 1/4" for NA single exhaust regardless if stock or ported]

What about the crossover pipe? Does engine guru _ROB_ have any comment on those? They're really popular with V8's, I've seen numerous reports of increased HP on the dyno with the xpipe on V8's what about rotaries?

Dave

rxspeed87

please guys
would like some info before I do it
if not dont mind being a test dummy but if any out there has any ideas please let me know