DavidHolmesIII

Alright, Ive been doing a lot of work with my 88 GXL am trying to free up the exhaust since ive recently replaced the catalytic converter with a high flow (rotary specific), air pump, line etc. I have seen several headers avaliable and am curious if it would be worth the 125-300 dollars.
Specific questions:

1.Emissions here in TN are a concern hence the emissions replacment.
2. Heat. This is a weekend driver so the streetability must be maintained. (wouldnt want it melting my charcoal canister, etc)

If you guys know if any of these concerns are justified I wouls appriciate it.

PS, My intention is not to increase performance as must as it is to increase efficiency. I know the HP gains for a header would be minimum.

meteoro

near of 18 at 22 hps gain


nice work, do it

Twins80s

iTrader: (3)

DO IT! I dont have any dyno to show there is a HP gain but it was the first thing I did. Got the header/cat combo from rx7.com and it added some spunk to the old rx.

DavidHolmesIII

I had a buddy who put a header on his FB and it would glow red hot after a drive, and that made me wonder if that would be a problem. Maybe wrapping them would help?

FelixIsGod29X

iTrader: (50)

Shouldn't be glowing, prob a clogged cat if he still has it. Just adding my .02

DavidHolmesIII

God, I dont know. That was back in 1999. Wouldnt have been surprised though if that were the case.

RX7freak08

Ummm I was told all rotary engines do that if they have been running at high rpms for a while.

FelixIsGod29X

iTrader: (50)

Alright if you guys say so.

j0rd4n

do it! besides, i think exhaust is one of the things you'd see the most gains from compared to a stock 7. you've already replaced the cat, just get a nice header now

George84

Just get the downpipe because the header would be alot louder and you said "streetability must be maintained". The downpipe is going to offer almost the same gain without as much noise.

ericgrau

iTrader: (1)

I'm still waiting for a private person to provide a before/after header dyno. Theoretical loss from 2 sharp 90 degree bends is 2 horsepower at high revs and WOT (less otherwise). Carefully selected pipe lengths might make a little difference at certain rpms (while hurting other rpms), but I haven't heard of any header maker attempting or claiming such a thing.

Your real concern are the auxillary ports. They activate via exhaust backpressure at around 4000rpm. With your high flow cats they might not be activating anymore, which means you gained less than 17 horsepower from your new cat and lost 25 horsepower from not using the aux ports. Do a forum search to see how to test them and how to set up another way to activate them.

Besides that you can get 7 or 8 horsepower from good mufflers, if you haven't done that already. You could also get a cone intake with a box around it to keep hot engine bay air away and with a duct to let in air from outside. That should net 2-3 horsepower. A cone intake sucking warm air probably makes you lose power. You can also get about 3 horsepower from Royal Purple oil, from reduced friction.

The exhaust and intake are about all you can do to an NA without getting crazy. Next would be aggressive tuning (can't do much on a DD), then engine porting (big help even when kept mild for a DD), then replacing various engine parts to raise the redline (can't think of any issues on a DD except maybe the carbon apex seals). Unlike other NA mods, porting will reduce mpg a little and increase emissions a little. And you won't get more power from raising the redline without porting. You can also try to reduce the car's weight, which would make it a little faster without adding power and it'd fit your goal of efficiency.

DavidHolmesIII

Thanks Eric, and the rest. Ive been seriously contemplating the borla cat back. And someone had offered a bonez superflo midpipe. Doesnt that keep the stock manifold?. Its not a daily driver. I drive the **** out of a 2000 Saturn SL1 and baby the rx7. 90% restored. Im only limited by the emissions and my tolerance for noise. I dont want it to be too loud.

George84

Really all you want is a downpipe and catback.

RX7 allnight

+1 ^

unless your ported or have a carb you really dont need the header.
all is needed is downpipe + cat back.

DavidHolmesIII

No ports. midpipe replace the pre-cat?

SpeedOfLife

iTrader: (16)

Downpipes are for bringing the exhaust down from a turbo, which he does not have. Increasing the exhaust efficiency almost guarantees an increase in exhaust noise because you'll usually do one, some, or all of four things:
1) Use a more efficient header
2) Remove/replace the cat(s) with something more efficient
3) Use an overall larger diameter exhaust pipe
4) Use more efficient mufflers

Quality street exhaust systems are usually made from thick material though, if you want to make a custom system that isn't obnoxious try to use thick pipe.

ericgrau

iTrader: (1)

If you want something quiet and indestructable, albeit at a higher price, then get Racing Beat mufflers. And they still provide like any other loud muffler.

Larger diameter pipe will do next to nothing, especially at near stock power levels.

SpeedOfLife

iTrader: (16)

I second that, I've heard them and they're nice sounding. Often a technically louder sound is much more tolerable if it has a good tone to it, and the RB systems do.

SpeedOfLife

iTrader: (16)

Yeah, you're right, I just listed it because it's a common one.

George84

Racing Beat makes downpipes for the n/a rx7 also, its still the pipe between the stock exhaust manifold and the cat.

SpeedOfLife

iTrader: (16)

So they do. My bad.

DavidHolmesIII

So im getting from this that I need a down pipe, and cat back. Prefer borla on the cat back simply because the sound. Which downpipe is prefered? Keep in mind im trying to keep it as quiet as possible while keeping it as free-flowing as possible.

1SWEET7

iTrader: (1)

It is hard to get a quiet, free flowing N/A exhaust. My exhaust setup is completely tolerable, and is only loud when I get on it good.

DavidHolmesIII

I understand that its going to be hard to get what im looking for, Im willing to sacrifice and just deal with the noise; just trying to put this "Frankenstein Exhaust " together with as much input from experienced owners such as yourselves.

ScrapFC

iTrader: (5)

I'm very happy with my exhaust. The power gains are very noticable, especially on top. When I modded my car, I did it a piece at a time, so I got the feel for a lot of changes.
When the car was stock, it was nice and quiet and the power came on gently but firmly from 3800-6000RPM. The motor was DONE at 6500RPM.
I installed a Mintrain header, Bonez cat and big-*** Corksport single catback, which came with a silencer insert. With the insert removed, power was much-improved up top and now the car would pull to 7000RPM, but the exhaust note was EAR-BLEEDINGLY LOUD. With the silencer in, the noise was only a little annoying, but the top-end power was gone by 5000RPM.
I replaced the Corksport with a stock TII catback (Thanks, Blue TII!) and got the noise under control at the expense of a little bit of top-end power. The exhaust note was raspy and metallic. Not very pleasing, but much more bearable. Power held until 7000RPM.
When I finally ponied up for the Racing Beat mufflers (I wouldn't bother with their Y-pipe. The ID is no larger than stock, and the build quality is pretty disappointing.), the top-end power seemed very slightly better, but that may have been optimism. The important thing is that the sound is AWESOME! Pure rotary music at 94Db. (Measured per BAR regs)
With a cone filter, modded TB, ported/lightly polished intake and Pineapple inserts, power stays on until 7500RPM and Aux-port actuation is dramatic. I've had wheelspin a few times at the changover point. Fun!
At this level of modification, I went out to the local "street drags" and made a few passes. They don't run timing at these events, but I had fun and crossed the line at about 92-94MPH. I am assured that (With a driver who can launch) those speeds should mean a low-14sec pass.
I haven't run at the drags since I swapped the 24lb stock TII wheels for my sexy 16lb Enkei RPF1s and also swapped the 24lb cast iron flywheel for a 9-lb Fidanza, but I can tell you that the butt dyno says these two things have made as much difference in 1st and 2nd gear as everything else put together. I am traction-challenged with Falken Azenis RT-615s in 255/40-17!

Sorry if I rambled too much. Here's the short version: After making sure that the the rest of the car is in tiptop shape, (All maintenance up-to-date and no "issues") buy the best exhaust you can afford. Rotaries respond very well to (quality) exhaust mods. Stay away from the cheapass systems. They usually don't make as much power, they don't last as long and they always sound like ***.