Ok, here's the deal. I have a friend who swears by "free flowing" exhaust systems. I used to have a 94 jeep wrangler 4 cyl and he convinced me to get one when my original exhaust was shot. All it did was make it sound like a ricer and kill my gas mileage, which he said would be helped.

I talked to him again for the first time since buying my 2002 blazer and he suggested I get one for this. When I brought up the argument of the poor gas mileage on the jeep he suggested it was because of the O2 sensor, something about with more exhaust flow causing the O2 sensor to cause a rich condition.

Anyway - I don't know much about exhausts but I understand how a free flowing exhaust can add power, and should help fuel economy, I would think. I just don't my blazer sounding loud or raspy. I enjoy not hearing my engine/exhaust and riding around town quietly. But I also would like the benefits if they're real.

So, can someone educate me on this - should I just avoid the exhaust and be content? Would it only be loud when I really get on it?

Thanks.
-Sean.

 

Welcome! What exactly did he or you do to your Jeep for a "free flowing" exhaust? If it was hacking off before the muffler or even the cat, then that is a terrible "free flowing" exhaust. You lose backpressure and throw off the 02 sensor, which does kill your MPG. Now, hi-flow cats (you have 2 cats on yours), and/or a catback exhaust kit will probably help you out. The key when upgrading the exhaust to allow for better flow, is to not go overboard on the diameter of the pipe. A good general rule of thumb is to not go more than a 1/4" - 1/2" bigger than your stock pipe. On the Blazer the pipe from your cat to your muffler is 2 1/4" (outside diameter).

For muffler selection, check out Youtube for "4.3 exhaust" and see what you like.If you want something that has a nice, not so loud tone, then checkout Dynomax or the Cherry Bomb Turbo. For a nice rumble Flowmaster 40 (I think thats the one anyway), Magnaflow, and Edlebrock give a good overall tone thats noticable but not annoying/ricey. If you want LOUD then some of Flowmaster's mufflers are loud as hell, so is the Cherry Bomb Glasspack, and any style of bullet muffler.

I haven't done the exhaust on my Blazer yet, but on my Firebird I got like a 2MPG gain. Any more questions feel free to ask.

 

On my jeep we actually purchased a full exhaust including hi-flow cat that bolted on at the back of the header.

I'll take a look at the videos on youtube and check back in. Thanks for cluing me on to that.

-Sean.

 

The Edelbrock SDT has a real nice low tone... I was going to buy one but decided to save my money lmao.

A good thing to go with exhaust is also an intake... check out my build thread to see what I did for mine, I picked up a bit of MPG I think, but I had a lead foot because of the sound with it lol, so if there was a difference I didn't notice.

Also once you're done, a PCM tune will get everything in check.

And I think the problem with the jeep, is it was a Jeep lmao. Sounds like your O2 sensor was bad.

Good luck.

 

Thanks for the info. I've got a cold air intake on it now, along with a throttle body spacer that the previous owner put on. I'd like to fab up a heat shield for it so it actually gets cold air instead of hot, but that is down the road.

I'm not going to do an exhaust any time soon - the one I have works just fine. But if it ever rots out or starts leaking I'll consider one of these more seriously. A PCM tune on the other hand is something I am considering in the near future.

-Sean.

 

Do the exhaust before the tune so you'll only have to tune it once. Just do 2.5" pipe after the cats and go with a turbo muffler if you want it to sound nearly stock or a chambered muffler like a Thrush Welded if you want a bit of a rumble, then get a 2.5" tail made for it and you'll be good, it'll flow better and not be overly loud, in fact it'll still be rather quiet.

 

I had a flowmaster 40 series muffler and I got sick of it and now I have the stock muffler back on. I've actually noticed my gas millage has gotten a little better. If you don't necessarily want your truck to sound loud a new muffler is pretty much a waste

 

You can get a muffler that flows better than stock but isn't loud. Guarantee you a turbo muffler will be just as loud as stock but flow much better.

 

I've been eyeballing the kit from Gibson, seems to be pretty sedate sounding, but I wonder about mileage. I'm concerned, like benedict1337 experienced, that it will be worse.

So we'll see. Thanks for the continued input.

 

Thats probally because your not on the gas as hard to hear the exhaust