NOMOREWORK

I just recently purchased an 89 Coupe with 38,000 miles on it and
I am making my first upgrade. I am putting on TBiS headers and a dual exhaust front to back without cats. Do I have to change the stock mufflers to get the maximum performance gain ? Do not want drone as I will be driving this car on some long trips this summer. Thanks in advance for your help

HlhnEast

I would have to say yes, to get ALL the performance out of it a free-er flowing muffler would be necessary. How much you gain or lose may be negligible. I would think you pretty much made your gains with I am assuming the long tube headers you installed.

There are mufflers out there that dont have excessive drone so search a little bit here to find out which are suggested by members. I personally have muffler eliminators and you cant make a call at 70 mph and hear it so they are definitely out for ya!

Good luck with your car, drive the snot out of it.

kenmohr

I put Corsa cat back 5 years ago. I could feel a performance diff and can now hear the radio on the highway. I am pleased with them.

WVZR-1

Headers less cats and "stock" mufflers I'd think make many very happy. I believe that I'd certainly do it this way for starters. If I were to suggest anything it might be to consider maybe an LT '92+ for the exhaust with your header choice of course. The LT tips look very good on the earlier cars I think.

Try local and see if you might land one "for cheap".

c4cruiser

My '87 autocross car has Hedman Elite headers, true duals, an X-pipe at the location where the main cat was located and DynoMax UltraFlo mufflers. The car is pretty quiet on the street and no noticeable resonance at freeway cruise speeds (60-70 MPH). The X-pipe will be the key to reducing the interior resonance. There are some good mufflers you can use such as Magnaflow or Corsa. Avoid Flowmasters like the Plague....

At high RPM such as 5000 or so, my car with the above setup has registered at 97dB on local road courses.

aklim

You will get drone. I know mine does and it has 1 cat (Random Technologies) and a Borla Stinger system. Supposedly the LT1 exhaust system will not hit you too much on power and is reasonably quiet and cheap. OTOH, I'd be afraid of getting some low buck exhaust made unless they are using 304 steel or 409 and decent thickness for durability. Good exhaust isn't cheap and cheap isn't, as a rule, good.

With just headers, I don't really think you are going to be too worried about performance. I'd say the first step in that direction would be intakes and a dyno tune. That will set the foundation. Besides, a few HP loss isn't an issue unless you are racing for some prize purse.

0Magna_Flow

You dont really HAVE to change the stock mufflers, but if you're already doing a full exhaust, you might as well throw on 2 aftermarket mufflers. The universal ones we offer have a straight-through design to maximize flow and longevity. If you have any questions about sizing, just shoot us a PM or call!

GREGGPENN

A LOT of people have tried the catless route only to put them back on. Watering eyes and the smell are common reasons....drone is another.

I've always lobbied for people to keep performance cats since they also serve as resonators. I'd try a couple of bullet cats (random tech or magnaflow) with no mufflers. Then, if you don't like the sound, add the appropriate amount of muffling further back.

I have ridden in an LT1 with headers, no cats, and stock mufflers, I doubt those stockers hurt much...but the LTx system has larger diameter pipes/tubing. There was ZERO drone. Perfect sound quality. That said, I think L98s are a hair more prone to drone.

Prone to drone....good one! LOL


BTW....Good choice of headers!!!

aklim

Not sure what they are talking about concerning eyes. You don't stand around and sniff the exhaust. I get in the car, start it and drive. As to the drone, not sure if it was because of the headers or whatever. Didn't bother me either but it bothered the wife and hence bothered me indirectly so I got a Random Tech cat and that made it tolerable in her opinion.

bjankuski

I do not believe you need to change the mufflers to get a decent gain with the headers and dual exhaust. Try it and see how it performs and sounds, if you change the mufflers I would be concerned with drone.

THE 383 admiral

Technically. Slightly mixed Post TPI & LT1.. If you are removing the CATS, adding headers. you should adjust the BLM constant table. I will mention specifically for the 94 - 95 PCM. GM has the AFR Very rich. in all 95 & under platforms. They offset this with a UN-necessary combo WOT ~ AFR % @ temp VS AFR % VS RPM. Older platforms Same method in openloop.
As for the idle. AFR in the 94 - 95 PCM. the BLM constants table. Absolutely. Needs to be corrected. And narrow the BLM window. To lean out GM's very rich calculation. I recently learned this on my Current 94 PCM upgrading to headers H pipe & mufflers. Open loop tables would NOT balance out. the AFR. till closed loop.
The drone is mostly from the muffler design. I know the OBX mufflers sound very good. Many High end mufflers still give you that drone in the 2000 - 2400 RPM range.

NOMOREWORK

Thanks that's what I was hoping for. Its not a race car so I figured if there was minimal hp loss who cares.