merc 93

So far, with my 1993 FD, with 50K miles on it, I've replaced the battery, and it started right up. Nice. Then, I decided on the wheels and tires I'd be putting on this car. Then I thought about additional body stuff like a front R1 spoiler and side body skirts. Next, I bought some new audio gear for the inside...

Finally, I decided to concentrate on those items which would be required to actually pass Texas inspection... stuff like CAT converters and my overly rusted original exhaust...

So, what do I need to consider when I buy and have installed a new exhaust muffler and pipe? What if the pipe running back to the muffler is also too rusted?
Which acutal units do you recomment that I install to insure passing of emissions while also being cost effective?

Thanks for your expert advice!

rynberg

Anything after the main cat has no effect on emissions. Buy any "cat-back" exhaust you want. They all come with the connecting pipe to the cat (actually, most are 1-piece units).

If you want a good mellow quiet exhaust, go Racing Beat or M2. If you want a loud agressive exhaust, get an Apexi GT or Dual N1s.

EDIT: If you need to replace the cat converter, just buy a hi-flow from rx7.com or n-tech. Make sure you hook the air pump back up to the new cat (the rx7.com hi-flow comes with the tube for this already, the n-tech doesn't).

Once you've done these mods, verify with your boost gauge that you are not spiking or overboosting. If you are, install an electronic or manual boost controller.

dclin

iTrader: (4)

If your exhaust pipes/muffler is rusted out, you *might* get some patches from Autozone, etc to maybe get your car to at least pass (if your tech isn't too picky) - but replace everything as soon as you can.

You can probably still pass with a hi-flow cat. What brand is out for debate - I have had a Random for the last two years, but others swear by Bonez (RP private label hehe), and others.

I've heard of people passing with a downpipe in place of the pre-catalytic converter, but YMMV.

Contact Mazmax (290/W Little York, 713-896-8005 IIRC) for your serivce needs. Byran is the service manager, 2nd and 3rd gen owner, and dedicated Houston RX7 Club member.

Come out to the next Houston RX7 Club meeting, July 1st - location TBA.

http://autos.groups.yahoo.com/group/htxrx7/


http://www.houston-rx7.net/

Also, it's normal for the stock exhaust system to develope oxidation - but it's fine as long as it's not rusted all the way thru. Patching it maybe fine as a quick measure, should you need to get it inspected right away, but's not something you should really be driving around on. Carbon monoxide is dangerous, and safety is not a place you want to save pennies.

dclin

iTrader: (4)

Here is a search on 'emmisions', limited to the 3rd gen section, which should get you pointed in the right direction:

https://www.rx7club.com/forum/search...der=descending

Contact Bryan, he knows a Harris county inspection station that is rotary friendly. Seems there are some tricks to a successful emmsions test, including a slowwww roll up in rpms.

rx7dave77

Hey dclin, do you have any idea where that July 1st get-together may happen? I am originally from Houston and am going home on the 1st of July to see my family. I am flying out so I wouldn't get to drive the FD, but it would be cool to check out all y'all's rides back home! I asked on the forum but figured you may have a clue too. Later...

merc 93

Hi Dave,

If I can get my FD running in a decent form, I'll be there. How about you?

dclin

iTrader: (4)

Have not heard yet, but remember discussing it will definitely be within the 610 loop - Azetca's on Richmond (btwn Kirby and Greenbriar) was the last meet location, and it was ok. I prefer Doneraki's on Fulton, but it will have to be a place where they have a meeting room (that they don't charge for), and Azteca let us use it for free as long as we eat there. We need some more 3rd gen guys (and you old timers/orginal members too) to show this time.

July 1st is rolling up pretty quickly, so Keith needs to decide pretty quickly hehe. Anyhoo, stop by - more the merrier.

dclin

iTrader: (4)

Come if your 7 is not running/showable anyways - what counts is member representation. My FD will not be buttoned up until August's meeting, so I've been crashing the meetings with my Civic hehe.

rx7dave77

Cool, I will definitely try to make it as long as I find out where it's at in time AND everything is cool with the flight and all. Sometimes it's hard to get going after being in airports and planes all day! Thanks for the invite, I'm sure my rental would look good with your Civic!

merc 93

Will I still need to worry about this even if all I do is replace my muffler with an Apexi N1 muffler?

dclin

iTrader: (4)

Maybe - the Apexi N1 (the Dual at least) is a very free flowing exhaust. Simple answer is the more free flowing your exhaust, the harder it is to control your boost. It's not uncommon for major boost spikes or boost creep when you start opening things up.

YMMV, as that you're situation will depend on how clogged the main cat is (precat should be removed and replaced with a downpipe, irregardless). I had some heart stopping spikes with a DP, original main cat, and a N1 Dual.

Should find some more info on this in this search, terms 'exhaust' and spikes', limited to the 3rd gen section:

https://www.rx7club.com/forum/search...der=descending

merc 93

Are there any aftermarket stainless exhausts which restrict flow just like the original exhaust and do not require boost testing or a new boost controller? Alternatively, are there any sites which list the flow of the various stainless aftermarket mufflers available?

Thanks for your help on this...

dclin

iTrader: (4)

I don't think there are any cat-backs that are as restrictive as the stock. The Racing Beat Dual is quietest of the three I've had, but quiet does not neccesarily mean more restrictive (if the manufacturer knows what they are doing).

All you have to do is get your boost under control (if it becomes a problem), it's not that hard. You don't need a electronic boost controller either, changing the boost control pill or using a manual boost controller may work fine for you. Here is another search, with some refinement in terms - 'control' 'boost' 'spikes' limited to the 3rd gen section:

https://www.rx7club.com/forum/search...der=descending

And a search for 'boost' and 'pills', assuming your still using stock twin turbos:

https://www.rx7club.com/forum/search...der=descending

dclin

iTrader: (4)

Here is another good source of info on an affordable way of controlling boost:

http://www.rx7turboturbo.com/robrobi...controller.htm

I'll also add that 'testing' your boost pattern is nothing more then accelerating in third gear and watching your boost guage to see what it does.

merc 93

Thanks for the info, dclin!

I spoke with Brian(MazMax) earlier today and he also recommended the Racing Beat or the GReddy SP mufflers. He said that as long as I only changed out the muffler to one of these two units, I'd have no problems with boost? He said if I changed two of the three sections, then I might have to start worrying...?

My intent here is to not get this car track ready, but for it to get back on the road in a dependable manner for the least amount of money. Right now, everything in and on the car is stock. If I have to go and buy(and have installed) a boost controller or even go and buy an instrument to measure my boost, I'm defeating my own purpose. Maybe what I really want is just a replacement original equipment muffler with the chrome twin tips? I wonder how much that would cost?

merc 93

My FD doesn't have a boost gauge... at least not that I know I do? I have a fuel, oil pressure, water temp, speedometer and tach gauges, but no boost gauge that I can find.

Is my car supposed to have a boost gauge? I am the first and only owner of this 1993 Touring purchased in Nov of 1992 directly from Mazda Corp. It was originally brought into the country for use by visiting Mazda executives and was also the used in the Houston Thanksgiving Day Parade by Grand Marshall Mayor Bob Lanier. Did they add a boost gauge to later productions?

dclin

iTrader: (4)

100% stock is actually bad for the car. The problem is you (likely) still have your precat in place, and it's best for you to get rid of it. It causes problems, of which is discussed else where in this forum. In fact, the only mod that Bryan's shop will do (they only do stock cars) is replace the precat with a downpipe.

DP + catback = 2 of 3 exhaust mods, which puts you at risk.

Of course, if you have an engine or turbos that are near the end of it's useful life, then just leave the precat on. I will say that removing the precat will take an emormous thermal strain off the components in the engine bay, and less heat is radiated into the cabin as well too. Get a dp ceramic coated for even better results.

Do a search for 'reliability' 'mods' for what needs to be changed on a 100% stock car to keep it healthy.

Your best bet is to replace the precat with a DP, and get a used, good condtion stock cat back. Very expensive brand new.

dclin

iTrader: (4)

The US models never came with boost gauges, JDMs did with the '99 year model (or maybe even earlier, not sure). You'll have to fit one, but it's very easy. How many miles do you have on the car?

edit - n/m, went back and saw your first post. I highly recommend you replace the pre-cat in any case.

merc 93

Thank you for all your help!
The money is certainly starting to add up. I guess I should fail the emissions test first, and then spend the money on the new DP and muffler, and then if I fail again, I can get a waiver based on how few miles the car's been driven in the past year. Then... I need to get the A/C fixed. Then new tires and wheels. Then a new paint job. Then... Cha-Ching.... yup, the money is starting to add up.

dclin

iTrader: (4)

Actually, the catch 22 about the precat is that removing will decrease your chances of passing emissions. It is, for a pratical purposes, the first 'catalytic' element ('cleans' the exhaust) the exhaust emmisions sees. Then you have the main (second) catalytic converter. I would just store it somewhere (if it's good still) and put it on temporarily in case you can't pass emmisions - though there have been cases of people passing w/o it.

The whole thing about the pre-cat is that is located right after the turbos, and retains alot of heat in the engine bay. The precat is known to breakdown pretty quickly, clog, and back up even more heat in the engine bay. There are reports of some people having their precats glow red.

The heat wreaks havoc on the vacume hoses and turns them hard and brittle, and the extra heat is just simply not good for anything else under the hood, especially coupled with the heat in Houston. How the hell can you stand to drive w/o A/C?

I thought I was going to keep my stock 3 years ago. Well over $20K later (not including the purchase price of the car)....

Silvia_S13

that was some sound advice, but i think the wastegate will be more of a factor than a boost controller for checking on spikes. manual b/c is good for raising boost, but you trade the cheaper cost for the possibility of more spikes depending on where you put it with regards to the actuator/wastegate.

trying to get back into the swing of things with the rotary world, im talking in reference to SR20DETs and their internal-type wastegates and adjustable actuators though. someone correct me if im wrong though

rynberg

You're wrong.

The stock ecu just blindly operates the wastegate. It doesn't know to open it sooner or more to maintain safe boost levels. Therefore the potential need for a boost controller to more actively control the wastegate.

Silvia_S13

doh, im sorry. SRs use the adjustable actuator that you just twist. you guys are way ahead of me, you got electronically controlled ones

merc 93

Well, I was gonna go with the Racing Beat Twin Tip muffler, because I was guesssing that it best approximated the resistance to flow of the original muffler, but, now that I'm replacing the downpipe as well, and will need to get a boost gauge and boost controller, I guess I don't really have to worry any more about back pressure. Right? Is there any reason to still get the Racing Beat Twin for $460?

That said, what is a decent quality stainless muffler for less? Are there any simple bolt-ons with integrated hangers that cost around $200?

How about downpipes? I've seen HKS ones being sold for $230. Is that a good DP and price? Are there equivalent quality DPs for less?

Finally, how about boost gauges and boost controllers...?

I'll be using the painfully slow search tool to look these questions up for myself, but in the meantime, if anyone can offer me advice, I'll be glad to take it.

As you can tell, money, and lack of mechanical ability, are problems for me...
Thank you all for any and all help you can offer me!

rynberg

I hate to say it but that is a VERY bad combination of problems to owning this car....I predict that you may not own this car very long...

As in most things, you get what you pay for, for the most part. The RB exhaust is actually cheaper than many of the other aftermarket cat-backs and is extremely high quality. You might want to try the Blitz Nur-Spec if cost is a big issue.

I would not get a mild steel downpipe like the HKS. Get a nice stainless steel one. It will be worth the slight bit of extra cash.

Go through the rx7store.net. Jason has the best prices around and you support the forum shopping there.