Exhaust opinions?

[1990Cheyenne]

Hey guys, new member. My first vehicle ever was a 91 s10 with a 4.3. I've also owned two 2012 Sierras, a 5.3L and a 6.2L, both fbo and cammed. Now I find myself with a 1990 c1500 rclb with a 4.3 again. I went from 500hp to 160hp, lol.

The exhaust on my truck is QUIET. I have a buddy with a 2006 4.3 silverado, and his stock exhaust is FAR from loud, but nowhere near as quiet as mine and sounds great. I am thinking about going with a cheap hi-flow cat and a SI/DO cheap Flo-Pro muffler. I do not want loud exhaust, but I want it to sound like a truck.

I will have to measure because I can't remember if the stock piping is 2.25 or 2.5. If I get drone, I will have a J-pipe welded in. If I find it raspy, I will add a resonator. I currently get 18mpg on the interstate (77-78mph).

My questions:
1. What kind of effect will this have on my fuel mileage?
2. As long as I have a cat, A/F ratio should remain the same, correct?
3. Does anyone have any recommendations for me?

Thank you all. Good to be here.

 

[df2x4]

Shouldn't have much effect on fuel economy, if any at all. Not sure what you're getting at with AFRs and the cat...

Probably not what you're looking to hear since it seems like you're looking at cheap options; but I have Pacesetter shorty headers, a Magnaflow Y-pipe with high flow cat, and a Gibson single 3" cat-back system on my red '97 with the 4.3. It sounds great. I've been complimented on how good the V6 sounds many times.

 

[1990Cheyenne]

Shouldn't have much effect on fuel economy, if any at all. Not sure what you're getting at with AFRs and the cat...

Probably not what you're looking to hear since it seems like you're looking at cheap options; but I have Pacesetter shorty headers, a Magnaflow Y-pipe with high flow cat, and a Gibson single 3" cat-back system on my red '97 with the 4.3. It sounds great. I've been complimented on how good the V6 sounds many times.

I was mildly concerned about a cheap cat not doing its job as well as the stock cat, causing the o2 sensor to send different info to the ECM, ultimately affecting fuel economy.

You're correct, I'm trying to keep this cheap. How did your setup effect your fuel economy? Did the engine seem to run better?

What is the most restrictive part of the stock exhaust (muffler, cat, manifolds)?

 

[df2x4]

The cat shouldn't effect fuel economy at all unless it's clogged and causing excessive backpressure. The oxygen sensor that effects AFRs is in front of the cat. The post cat O2 is only there to monitor the efficiency of the cat and let you know if there's a problem.

I don't think my exhaust effected much other than sound, to be honest. I didn't notice any change in fuel economy. Maybe a tiny bit of extra pep off the line but nothing drastic.

IMO the most restrictive part of the V6 exhaust setup (at least on the 95+ Vortec trucks) is probably the factory Y-pipe, mainly because of how bad the bends are. I couldn't tell you for sure, though.

 

[1990Cheyenne]

Thanks for replying

 

[Little Jeff]

I have a 98 c1500 with the 4.3l what I ended up doing is getting another universal cat from AutoZone and a flowmaster super10. I had it turned down at a 45 degree angle Midway between the axle and the rear of the cab. It definitely sounds like a V8 at 600-2200 rpms. All bets are off above those rpms. Hope this helps with your decision.

 

[Franks]

Shouldn't have much effect on fuel economy, if any at all. Not sure what you're getting at with AFRs and the cat...

Probably not what you're looking to hear since it seems like you're looking at cheap options; but I have Pacesetter shorty headers, a Magnaflow Y-pipe with high flow cat, and a Gibson single 3" cat-back system on my red '97 with the 4.3. It sounds great. I've been complimented on how good the V6 sounds many times.

was your y pipe and cat separate or did you buy them welded together?

 

[df2x4]

was your y pipe and cat separate or did you buy them welded together?

The Magnaflow Y-pipes come with cats installed.

 

[fancyTBI]

Don't put a cheap thrush on it. You'll be embarrassed to be seen. I know from my own experience.

 

[b454rat]

I had an S-10 Blazer with the 4.3, and put a flowmaster on it. I think I got rid of or gutted the cat, it was 10 years ago and can't remember. But at idle it sounded like a V-8. Once RPMs got higher, it still sounded good, but didn't sound like a V-8. Rest of the exhaust was stock.