Long primary or short primary exhaust?
 

Does anyone have solid info on N/A short primary exhaust that collects right after header into a 2.5" pipe, then 2.5" RB presilencer, and 2.5" muffler after the axle?

Vs. the traditional 2.0" long primary exhaust, dual RB presilencers, that collects right before axle into a 2.5" muffler?

In terms of:
Width of Powerband
Peak HP
RPM Peak HP is at
Amount of noise supression
Tone quality


This is for a 13b Streetport 4-port N/A.

^

I'm interested in this info as well as I'm going to rework my exhaust again this spring and was contemplating going to a long primary setup.

Well i have a header 2.5" is what i looks like into 1 silener to 2" all the way back into a dynomax muffler... (bought the car with this system on it) and i made 109.5 hp @ 6776 rpm and 91.6 tq at 5000 rpm... on a mustang dyno here video it sounds tinny prolly due to the shity muffler http://videos.streetfire.net/video/f...d901169e62.htm
i also have the dyno sheet posted if youd like to see it https://www.rx7club.com/1st-gen-general-discussion-207/dyno-results-701299/

not sure if it helps but im trying damnit lol

ill take pix as soon as i can get my camera...

I've had both systems on both stock and streetported engines so I know which does what. However everytime I talk about it someone who's never had either usually fires back with how I'm wrong. Therefore I'm just going to sit back and watch the responses that come in. If anyone is curious what my opinion is between them, and please don't ask for dyno chart bs, you can just pm me.

Your Wrong!!! Pm sent

screw that. post what youve got on here. all the haters can crew off. put it here for the forum to see!

the 84 rx7 i have how has the same engine that i had in my 808 before it was wrecked in 05. it's a '74 streetported 13b with RB's long primary system which is offered on their site for sp 13b. it was surprisingly quiet and very nice tone. i think it restricks the lower end. the way it is now in the 7 is still long primary, but missing the presilencers. it's of course louder but i think it's tollerable. but then again, noise is't as a factor here as other places. the 808 would cover the 8th mile in 9.381 and speed was 76.xxx. i'm sure it would have been faster but at the time i got to the strip, and the crowd, i was only able to get 2 runs. haven't gotten time to take the 7 as it would need a clutch before going.

I use RB's long primary or street port system, even though my motor is stock port. I love the sound!! I think the advantages to this system are in the upper RPM range, it sounds really great at WOT and seems to really rip then. Dyno results and graph are posted in the 1st Gen Dyno sticky. However when I got on the dyno it was free, i.e. no wideband hookup. I later found after installing a wideband that I was super rich so I'm sure that robbed me some hp.

I have a collected header into a single RB presilencer and a Primaflow muffler on my rallyx RX-7. It's quiet. Like in stock quiet. It needs to make more noise.

I have the RB streetport exhaust on 2 of my other RX-7's. On the non-ported motor it sounds just right. On the ported motor its just a bit tinny.

Power wise I can't tell you the difference. The rallyx RX-7 is a 12A, the others 13B.

SgtFox has the book, How To Modify Your RX7 on his website. I suggest reading the chapter on exhaust of the book, very interesting read. The book was written by Dave Emanuel and Jim Downing, 2 of the biggest names in rotary racing back in the day. There may even be a link in the FAQs, of all places, lol.

Dude great responce but you need to go to the GG/BG section and clear your name.:shocking:

url
 

anyone have a url for this sgtfox website?

The following is the link listed under his profile. However, I couldn't get it to come up.

http://rx7.foxed.ca/

link no workie