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A few years back when we got my wife's 4runner, we outfitted it with lots of parts to make it look like the Pro version. We did the OEM Pro exhaust which turns out resonate horribly. I added exhaust dampers from another Toyota vehicles (typically bolted to the exhaust pipe near the cats) which did help some, but not enough. We sold the exhaust and went back to stock. Since I had the dampers laying around, I bolted one to each side of the Cayman's exhaust using an exhaust U-clamp. My God, it makes quite a difference in the smoothness of the engine at all rpms, especially below 4000rpms. It's not BMW inline 6 smooth like my M235, but it's definitely an improvement in refinement and engine smoothness.
Weird mod for sure, but I always felt the 2.9 had a bit of roughness to it even with brand new trans and engine mounts and a new dual mass flywheel. It's not terrible, but certainly not very refined.
Is the 2.9 less smooth than the 3.4? Because the 3.4 in my 2010 CS is *really* smooth, and a flat-6 should have similar balance/smoothness to a straight-6.
I'm not saying you didn't see an improvement, but are you sure it's not something in your exhaust that was causing the vibrations? The rods supporting the exhaust are adjustable: maybe they require some tweaking? I know on my car one of the mufflers was hanging slightly lower than the other and I had to do some adjustments to the rods: it's possible if they're not sufficiently taut you could be getting vibrations.
so you added mass to change the resonance frequency of the exhaust pulses as they pas thru the exhaust system??
It may change your perception of the exhaust operation, but very unlikely to affect affect engine "smoothness".
Glad you liked your DIY work.
Is the 2.9 less smooth than the 3.4? Because the 3.4 in my 2010 CS is *really* smooth, and a flat-6 should have similar balance/smoothness to a straight-6.
I'm not saying you didn't see an improvement, but are you sure it's not something in your exhaust that was causing the vibrations? The rods supporting the exhaust are adjustable: maybe they require some tweaking? I know on my car one of the mufflers was hanging slightly lower than the other and I had to do some adjustments to the rods: it's possible if they're not sufficiently taut you could be getting vibrations.
I would not say my 2.9 is overly smooth below 4000rpms when compared to my 2016 M235. Above 4000rpms it's pretty decent, but nothing like an inline 6. Definitely way better than my wife's 2020 4Runner with a V6 or my son's 2020 Mazda 3 2.3 liter I4. I've never driven a 3.4, but have driven a 3.2 and another 2.9. Both weren't overly smooth in the lower rpms.
How does one adjust the exhaust "rods". My stock exhaust has been off numerous times and see nothing to really adjust. There's definitely nothing wrong with the exhaust itself though.
so you added mass to change the resonance frequency of the exhaust pulses as they pas thru the exhaust system??
It may change your perception of the exhaust operation, but very unlikely to affect affect engine "smoothness".
Glad you liked your DIY work.
Oh, it absolutely makes the engine/drivetrain smoother from the seat of the pants/pedals/steering wheel. Toyota, BMW, and tons of other makes add dampers to exhaust, suspension, etc. My M235 has a 4lb damper bolted directly to the subframe by the differential and multiple dampers on front subframe.
My guess is the exhaust system vibrates/pulsates a bit and causes some vibrations through the chassis since exhaust is only really supported to two band-style clamps and no rubber hangers like most other makes use. There's a big difference on cold starts. It's much smoother and almost feels like a hot start now.
Like I said earlier, I've replaced all mounts and the dual mass flywheel with all OEM parts. The engine mount and dual mass flywheel were toast. Adding these dampers definitely makes the car smoother in its feel which I prefer.
In the smoothness department, I consider my 2.9 to be more of a turbine versus engine. It’s an extremely smooth engine, and matched with the PDK, an otherworldly matched powertrain.
How does one adjust the exhaust "rods". My stock exhaust has been off numerous times and see nothing to really adjust.
Well THERE'S your problem, lol.
Here's the exhaust mounting support (less the two outside pieces that clamp around the mufflers or cats or whatever). You see those brackets on the ends? if you loosen the bolts clamping them to the rods you can adjust their position on the rods and then tighten again when it's where you want it. This lets you adjust where the support is holding the exhaust.
On mine one muffler was a tad low: I loosened the bolts, jacked that muffler up slightly with a floor jack, and then retightened so that the upper rod was holding it slightly under tension. It's been a long time but from what I read (assuming I'm remembering right) that's how you want set it.
No guarantees but it's entirely possible yours is not adjusted right: I've heard of that causing noise and vibration. Unless the 2.9 is a lot different than the 3.4 it seems really unusual that you'd have that much vibration: I'm always amazed at how smooth my Cayman is through the rev range.
Here's the exhaust mounting support (less the two outside pieces that clamp around the mufflers or cats or whatever). You see those brackets on the ends? if you loosen the bolts clamping them to the rods you can adjust their position on the rods and then tighten again when it's where you want it. This lets you adjust where the support is holding the exhaust.
On mine one muffler was a tad low: I loosened the bolts, jacked that muffler up slightly with a floor jack, and then retightened so that the upper rod was holding it slightly under tension. It's been a long time but from what I read (assuming I'm remembering right) that's how you want set it.
No guarantees but it's entirely possible yours is not adjusted right: I've heard of that causing noise and vibration. Unless the 2.9 is a lot different than the 3.4 it seems really unusual that you'd have that much vibration: I'm always amazed at how smooth my Cayman is through the rev range.
I've had that off when I painted my muffler cans black and added an X-pipe last year. Can't say I noticed any change in NVH messing around with it and getting the exhaust aligned. I did make sure to tighten things little by little, side to side. The rods and spring cylinders are definitely there to quell some NVH.
Guess my 2.9 is an odd ball. It has a ton a character and screams to redline while making glorious sounds. It's relatively smooth, especially once warmed up, but i certainly wouldn't call it turbine-like. Maybe I'm just too used to my BMW that I've had for nearly 9 years.
If there was something inherently wrong with my 2.9, i would have expected to see some indicators of failure over 10k miles and 1.5 years of ownership, something in the oil, oil consumption, or smoking. It doesn't have any of that.
Flat-6 is a naturally balanced motor. No roughness unless something is worn out or broken.
Nothing is worn or broken.
I did mess around with the exhaust mounting support, specifically the rods. I loosened everything but nothing seemed to move. I then took a vice grip to the rod and twisted it to get it to move. Then I heard a "pop" from the exhaust mounting support. I have no idea what exactly popped as nothing seemed to shift. I tightened everything down and subsequently noticed a smoother running engine??? I guess there is something to be said about what those rods apparently do. Can't say I ever came across any threads noting that the exhaust mounting support had some level of adjustment or was responsible for reducing NVH. I am curious to what's inside those upper cylinders at the end of the rods.
I still left the dampers on because why not? The motor is real smooth now at all rpms. Still not BMW inline 6 sewing machine smooth, but smooth none the less. Sounds way better too.
I think the upper cylinders are rubber mounts but don't quote me on that.
The procedure I found somewhere on the intertubes (but cannot find again) was to loosen the brackets, slightly jack up the muffler, and then tighten. This puts the upper rod in tension, which supposedly is what you want. Worked for me but, again, no guarantees.
Anyway sounds like what you did helped, so that's good!
Have you changed out the transmission mounts? That made a big difference on my 22k mile 3.4.
Yep, the engine and trans mounts were replaced with OEM parts 1.5 years ago. They were toast after 12 years and 70K miles, especially the engine mount which was ripped straight thru.
05-23-2024, 05:30 PM
Exhaust dampers to improve engine smoothness
