Okay, new reasons why I'm a ricer. (yes the pushbutton start wasn't enough!)

I now am the proud owner of an Apexi WS (maybe WSII? I dunno) muffler. ITS SO SHINY!!!! And I can shove my fist up the tip of it!

Next up I have an aluminum Apexi badge that's one inch tall by 5.5 inches across. I'm going to use it to cover up the paint discoloration on the rear where my Mazda badge was. The Mazda badge fell off shortly after winter and cracked into many pieces. Lucky for me the Apexi badge color matches my I <3 my RX-7 bumper sticker, so its all good in the hood. Pic coming soon!

On the interior I got a little punk rock button that I put on my bandanna shift boot. YEAH I'm a rebel!"

Oh and last but not least I have what I like to call "The Boost Gauge for N/As" aka a Vacuum Gauge. Since vacuums suck and so do N/A's (just kidding, screw turbos and their premium fuel and nifty blow off valve sounds)

 

where did you get that botton, that awsome

 

http://www.cafepress.com/ohio_rotaries

 

thanks, damn they got a **** loada stuff sweet

 

I like your sig.

Make sure and post some audio clips of the Apexi muffler. I'm interested to see how well it works for you.

 

Yeah, originally my exhaust setup was supposed to be this!



but since I got a $300 muffler for FREE, actually its the AE86 Corolla Cat Back System, it was my friend's but he gave it to me in favor of the Tanabe system.

I'm just being cheap, I'm getting an emissions complete and passable exhaust tomorrow for free as well, and then I'm going to mix and match piping and other things. If all else fails I still have my original plan, but that's $400 I could spend on suspension and brakes.

 

Sorry to break the news to you, but your vac gauge isn't ricer until you mount it in an A-pillar pod, lol That's where mine is, I'm still NA, but it has boost too. Planning ahead.

I like the bandana shift boot, I wear them all the time, can't stand ball caps. I got ragged on how big my Magnaflow tip is, but your's is bigger, ***** envy.

Do you think the Car Chemistry insert really helps? I'm not familiar with what they are supposed to do.

 

A local mustang guy I met at Autozone one day has one and spoke to me about it when he overheard me talking to a friend I randomly met there.

He says they work great, all the magazines I've read say they work great, and a few of these guys on these boards say they work aiight.

Here's how they work. Rather than just using restriction and backpressure to slow down exhaust gasses and waves to quiet the exhaust note. Since of course less waves going out means less sound. Instead it spirals the air through the drilled baffles raising exhaust velocity while cooling the exhaust gasses.



The backpressure is only enough to provide the effect of having a complete exhaust system. Example being that you gain more horsepower with a full exhaust rather than open headers. Well this reverses that and adds the neccesary backpressure to regain the lost HP. That's why they market these as header silencers and not exhaust silencers. Only nutjobs like me want to test stuff like this out on a normal exhaust, but they were engineered to be done as such if used correctly.

That's why, complete with the kit they give you tunable backpressure plates. If you're only running open headers you can tack weld one of these or both on each end for more backpressure.



You have to place them in the hottest part after the header collectors. If you google these if you find a negative review, its just some idiot that shoves it in his tailpipe, that doesn't really cool the already cooled exhaust gasses, now. Does it?

There's a review on RX7club on these and they gave them two thumbs up, lemme find it.

 

I do have an A-pillar pod, but I took it out after I realized how lame it really was. I think this is much more discrete, and dare I say it almost stock, and it doesn't give me that nasty blind spot.

 

Mine doesn't give me a blind spot, but I keep knocking the ash off the end on my cigarette because the pod sticks out too far.

Increasing/maintaining back pressure is good for pistons, but not nescisarily good for a rotary. If it does cool the exhaust, that in itself will reduce back pressure which is good on both points.

 

https://www.rx7club.com/3rd-generation-specific-1993-2002-16/car-chemistry-header-inserts-64896/ some third gen guys

But I still can't find the actual review from the 1st gen section. The RX-7club search engine blows so much I started using google to look for threads by using the "site:https://www.rx7club.com" command.

I was just talking to that mustang guy again and he told me it cooled not only through velocity but also through pressure zones. He just called me up to see if I got the 7 on the road again. Why is it everyone calls me to see if the Rx-7 runs but not to hang out? Lame

 

I finally found that one review

https://www.rx7club.com/showthread.p...=summit+review

 

Ewww! Louvered core is bad, no matter what other funky stuff that thing does.

 

DUDDDEE You need to learn. No amount of back pressure is good. PERIOD ALL BACKPRESSURE IS BAD!!! You're parroting false information. You want velocity in your exhaust not back pressure. in fact back pressure reduces velocity therefore killing all hp and tq... Please read up on real info instead parroting what some mustang guy at your local autozone says..

 

As a side thought, and I agree backpressure is bad, perhaps this might work if the exhaust was bumped up to a 4" diameter for the insert. And what is the price of this little gem?

 

They're $50 a piece, but one day at Summit me and Peejay found two for $20 and I couldn't say no.

Yeah and my mustang guy, just because we met at Autozone you think he's a moron? Ironically we were both there for fuses. Anyone that has a 10 second and QUIET mustang, oh yes I want to know them.

 

But the difference between what's good for a piston engine and what's good for a rotary is often what makes the difference.

Rotary : NO backpressure is beneficial in any way. You can't find anyone who can give a solid, valid reason for backpressure having any positive effects without them referring to parts that our engines just don't have, or exhaust dynamics that aren't an accurate representation of what happens with our cars.

This thing will definitely make your car quieter, no doubt about it, but if you took your car to to the dyno and ran both with and without it, I guarantee that you'd run more hp and tq without it.

The question becomes how much. Is the loss worth it to you to keep your exhaust at manageable noise levels? It probably is, since a 100% free flowing straight piped rotary has a sound that makes dogs run and babies cry. (ask me how I know, lol).

Thumbs up for the vacuum guage, and the sig.

Jon

 

I don't care if it's a pison engine or a rotary, louvered cores are pure ****. The turbulence they create reduce flow to to the level of OEM chambered mufflers.

 

Are you guys talking about back pressure as in exhaust gets shoved back into the exhaust ports of the engine? Or are you talking about a negative pressure wave that heads toward the engine, but actually shoves exhaust out toward the tailpipe?

See, the physics of it, as I understand it according to Paul Yaw (who everyone I've talked to pretty much considers a rotary god, and has done extensive flow testing in this area) and "Vizard the Wizard" (considered by many to be the best intake/exhaust man ever for piston engines at least), work like this:

First, the exhaust leaves the exhaust ports of the engine in a pulse of pressure, which creates a positive pressure wave heading out the exhaust, pushing exhaust gas out. As soon as that pressure wave hits a larger opening (cat, muffler, anything like that) the pressure wave reverses direction and sign. Which means it is now a negative pressure wave heading back toward the engine, which still pushes exhaust out. Now, a negative pressure wave will cancel out a positive pressure wave, so when the new pressure wave comes out it is weakened if the negative wave isn't back at the engine yet.

Cool thing is though, if the waves are timed right, you can actually strengthen the initial positive pressure waves leaving the engine by adding a weaker positive wave to it, and help shove the exhaust gasses out. This adds a few HP within a small RPM range. The two things that affect the timing of the pressure waves are RPM and the length of the exhaust pipe before the first pressure change.

So there is a perfect RPM at which you are shoving the maximum amount of exhaust out for your setup, any RPM above or below that will be less than ideal for flow. Even completely free flowing exhaust with 2.5" pipes and with no mufflers or anything will still produce the same pressure waves but they will be bouncing from the very tip of the exhaust back to the engine and back. As I understand it, the longer the pipes the lower the ideal RPM range.

Now, the stock setup is abysmal as far as tuning the pressure waves go, so pretty much any header will reduce backpressure and boost hp.

As far as my understanding goes these can potentially be helpful provided they are in a spot where there is already going to be a pressure change (like right where Tranquil is putting it) and as long as it doesn't block flow, which if it's made right it won't.

Mind you that's as far as my understanding goes, and I don't have practical experience with any of this other than how sweet my exhaust sounds.

Go here for more info, and from Yaw's exhaust writeups it sounds like these things might be beneficial if used properly. And if they cut the noise too that's great.

http://www.yawpower.com/techindx.html

 

Yeah, I'm surprised everyone always says its always NO backpressure.

Without backpressure the vacuum of exhaust would take a minimal amount of the intake and toss it out the exhaust at low RPM before it even gets combusted (from some of my learnings).

I am installing it with a flange, and I will be hitting a dyno in the springtime (Low_Impedence said it would be funny to do so, so his uncle's dyno is getting used). But in the mean time I'll give a sound recording sometime. I have a built in microphone in my iRiver which is damn badass.

 

Do let us know what the power is with and without the insert. Maybe the voodoo of the outer chamber/baffle will overcome the ugly louvers.

 

They're actually pretty well drilled. They aren't cheesegraters or anything of the like from a POS muffler. I took my blowdryer and put it on ultra hot and stuck this it in a PCV pipe earlier today, and the air wasn't even lukewarm even after 7 inches.

We'll see how I can work it into my exhaust system now. Since I'm short on cash my grand Borla exhaust system has been put on hold.

Right now its looking like header to y to 2 inch pipes to Apexi WS muffler. Since earlier today I got a free emissions passable exhaust system (brand new!), and after I pass emissions I'm going to use it with my header and Apexi muffler.

 

The fact that the lovers hang down in the exhaust flow is enough, no matter how well they're drilled on the opposite side. That said, the test will tell the tale and I'd be happy to be wrong on this one.

 

As a matter of fact: that's what's supposed to happen. Well, not like incoming mixture going straight through the exhaust of course. But the vacuum from the exhaust should "suck" the incoming mixture in. It will accelerate filling the chamber
Backpressure is not good on rotary engines because they work different then a piston engine. People talking about backpressure usually think piston engine-wise.
What works on a V8 most of the times will be unsuitable for a rotary.
In general the least exhaust is the best exhaust on a rotary. Same goes for a turbo engine, btw.
A very well setup exhaust on a rotary will be improving flow etc, but there's NO WAY you can build a DIY setup to those levels. It would take hours of testing (on rolling roads/dyno's) and experimenting to get it spot on right.
So the general idea is still: the least exhaust possible.

 

Son of a....

How many times must this idiotic idea be killed off?

ALL BACKPRESSURE IS BAD!

...its as simple as that, folks...

The problem is this, backpressure (which is easy to measure) gets confused with exhaust velocity (which is difficult to measure), leading to the confusion that backpressure increases low-end torque...

The fact is, the increase in low end torque is due to the scavenging effects of small diameter pipe (with HIGH EXHAUST VELOCITY) which at higher rpm have HIGH BACKPRESSURE!

THIS is why you should not stick a sewerpipe on your Normally aspirated car, as the scavenging effects of the HIGH EXHAUST VELOCITY increase the volumetric efficiency(? been a while since thermo...) of the engine. This is also why you will see more HP at higher RPM with a larger diameter pipe, but a reduction of low RPM HP (lower velocity at low RPM, get it?)

...this has gotta stop...

...oh, and this applies equally to a piston engine and a rotary engine.

Matt