Aftermarket Exhaust and Torque

I know aftermarket exhausts are not exactly popular on here as it is, but I am curious as to people's experiences with aftermarket exhausts on the 3.5 and torque loss. While doing some research on the aftermarket options, I noticed a lot of companies are selling straight through mufflers and calling the factory baffled style muffler restrictive as if that were a bad thing.
My understanding was that this train of thought was true with the engines of yesteryear, and that the engines of today need the backflow/baffling to hold torque.
Let me know! Genuinely curious.

 

i don't have numbers so this is a seat of the pants discussion for me.

i have completely redone my exhaust four times. it's all custom front to back starting with OV dump tubes, and all open flow from there out (media-less aside from the high flow cats).

after doing version 1 & 2 of my exhaust work, i was having a hard time with weakness under 2k rpm and an extremely mushy throttle and no torque there despite big improvements with power above 2k. the whole mid section of my exhaust at that time was 3" diameter, because that's what the URD mk2 Y pipe came with at the merge and downstream toward the muffler. when i did version 3, i decided i wanted to tighten this up to maintain back pressure and keep a steady pressure more or less, which was a big issue with the previous iterations. that big 3" section would buffer the pressure causing back pressure at the motor to fluctuate a lot, and it got very uneven and at times unpredictable and sudden power changes. so i replaced the first of my two 3" resonators with a 2.5" resonator, and it surprised me how big an improvement this made. then i knew i needed to complete the exhaust with version 4, and that was simple: remove all 3" and 2.5" pipes and resonators, and replace all with 2.25" diameter: mid pipe, both resonators (Vibrants), and the muffler's inlet, which i had downsized from 2.5 to 2.25" .

going from 2.5" to 2.25" all the way through turned up the torque, the usability of it (throttle response), and the steadiness/predictability massively. it's a totally different motor now. huge improvement, not subtle.

it's not just about baffling, etc, it's about maintaining steady flow pressure through the system, and the biggest hit to that is with excessively wide piping. this little motor doesn't need or like 2.5" or higher even with dump tubes and the tune turned all the way up. of course in my case it's just one element of the whole package of mods, but dialing in the exhaust over the last 3+ years has been probably the single biggest performance change after OVT.

 

This is exactly what I was looking for, thank you!

 

if you want to see more about my system, look here: https://www.tacomaworld.com/threads/daves-drivers-truck.659667/#post-23055718 (i'm not sure it's totally up to date).

the main thing i did want to mention to you and forgot...
i had done a bit of the exhaust including installing the Y pipe with rear cat delete, and there were performance changes. but when i removed the TRD muffler, everything opened up like crazy, and i never found that kind of restriction anywhere else in the exhaust after that... the cats are not even close to being as restrictive. that muffler sounds good, but it's so restrictive that, when combined with a fat 3" mid pipe upstream, things were noticeably wonky. so the back pressure and all that is managed by more than a restrictive item like a muffler. rather, it is best managed by having no sharp restrictions in your flow, like a media stuffed muffler, and instead manage pressure with consistent volume, which is why i reduced pipe size throughout. does that make sense?

 

Ughhhh, I need to cut that dumb 3" out of my Y pipe. One day I'll get around to it

 

I agree with su.brat. You'll lose torque by losing back pressure by going with a larger diameter exhaust. You wont need it with the n.a. v6 in our trucks. If you were supercharging or going turbo on it you could go slightly larger but even then 3" might be overkill. I've had my tacoma exhaust stock, stock with a borla weld in, and the trd ss exhaust. There is a noticeable power difference from going stock to the weld in muffler but depending on ur age and how many miles you put on ur truck, it may be too loud for daily driving. The exhaust seems to resonate louder than my jeep with full borla exhaust including headers. Since the tacoma is my daily driver, I ended up getting the trd ss exhaust. Lost a little torque compared to the weld in but it's quieter, stainless, and has an ok exhaust note.

 

Do you mean power gain or power loss? I've been wanting to put in a new muffler for a while just for some more sound.

 

Very interesting lads you have caught my attention

 

Man I love the deep sound of my 3in cat back mrbp xp performance exhaust but reading through here it makes sense

 

No difference with a new muffler if anything it might be a little worse. Leave it alone imho.

 

I put a Magnaflow SS on my 2016 and now a Flowmaster 44 on my 2020. No change in power for either. Not anything noticeable anyways. Magnaflow sounded good but was too tame for me. Flowmaster is perfect. Has great grumble and sound and does not drone.

 

Slight power increase with the change to the borla muffler. Some ppl dont notice it but it's not only the sound that changes. Your power/torque band changes which is why you feel a difference and makes you change the way you drive ur car/truck. It's the learning curve a week or 2 later that forms your opinion on whether or not you got ur money's worth from the mod.

 

Thanks for the input. I want to go with a Black Widow Venom 250 or 300. I had a 300 on my old silverado and it sounded fantastic so I'm curious how it would sound on the Taco. I know they're not even remotely comparable though.

The only time I've personally noticed any notable power difference with exhaust systems was when everything from the cat back on my old XJ fell off one day because the PO chopped it after the muffler and never supported it. Rolled around on just a cat for a few days and the thing couldn't get out of its own way. Put on a 3" catback from IRO and it was a night and day difference. I just know this truck can't afford to lose anymore low end. Speaking of, what is our stock exhaust piping diameter? Black Widow only goes down to 2.5"

 

I’ve noticed no power gains from my Borla s-type, sounds amazing though. Definitely no power loss.

 

I noticed the difference with all 3 of my set ups. It's not a huge difference by any means but there is a difference.

 

What's the drone situation with that set up?

 

No drone at cruising speeds on highway or city. When taking mountain passes you can definitely hear it, I don’t mind it at all, I wish it was a bit louder at times. The cool thing about this Borla, is it doesn’t get ricey at high rpms, it just maintains the same growl, awesome exhaust and quality product. The steel looks brand new and it’s been a year, the black tip needs a bit of love though.

 

Nice, which systems did you run?

 

@BobcatSR . I forgot to add, the exhaust got a bit louder with the tune, which is great.

 

Backflow/backpressure/etc are terms made up to justify the anecdotal observations of the ignorant, IMO. The exhaust design is to effectively and efficiently allow removal of the exhaust gases from the cylinders. The pipe diameter is one important aspect of how well exhaust can do it's job. If a pipe is too large of a diameter, the hot exhaust gas rushes from the high pressure area in the cylinder to the low pressure area in the exhaust manifold. If the pipe size is too large the velocity drops so much and it effects the scavenging properties of the exhaust manifold. So velocity is critical to performance. Too large of a pipe, velocity is low and scavenging suffers. This also happens at the collector where the primaries join the main pipe. If the main pipe is too large, it will have the same effect on velocity. Since it's further away from the exhaust valve/port, it's to a lesser effect.

C/N: unless your engine is pumping more air/fuel somehow, larger exhaust will probably only hurt performance or best case, shift the peak power rpm higher and low end torque will suffer.