I recently rode in a friend's 2001 K24 swapped Spyder. This k24 was stock, but the balance shaft had been removed. It was dyno'ed at over 200 to the wheels, around 220 if I remember correctly.
The performance of this car on the street was fantastic fun, with one glaring exception:
The vibration from the motor was excessive, VERY pronounced, (relative to a stock experience) more so in the passenger side than the driver.
I drove, and rode as a passenger. The power delivery was very satisfying for a street car. The car could easily lay down rubber if desired. The (just above stock level) clutch was easy to use. The shifting was delightful. The foot pedal responses were precise and predictable. However, the engine vibration was more of a obnoxious "race car" feel, as opposed to an enjoyable daily driver experience. The girlfriend would not want a Sunday afternoon drive in the car. (Unless she's a track racer =0)
The engine mounts are a few years old, and not the hardest material available for a Spyder. They aren't drag racing mounts.
Are there any solutions to reduce vibration? Does anyone really know how much horsepower leaving the balance shaft in robs in a k24 option?
Will a shop build a high performance K24 and leave the balance shaft in?
Are there any soft (reduced vibration engine mounts) on the MR2 Spyder Market?
Do the Toyota engine swaps like the 2AR-FE, or even the 2GR-FE offer a less vibrational experience?
(1zz and 2zz builds/swaps are not on my list)
I should state that I'm not trying to build a focused race/track car. I'm looking for a fun street car, that won't give my passenger a headache from vibration and exhaust drone. I have observed that most new enthusiasts who build a performance car have no idea how extreme the experience of driving the car will be until it's built, and then they learn how obnoxious certain aspects of the car are. A performance level that requires painfully irritating quirks is not my goal these days.
I'm coming from a history with:
Old V8 classic cars, turbocharged fwd and awd 4cyl cars, 220 hp Ariel Atoms, rides and some drives in dialed in (350 to 650hp) light weight sports cars, and most recently a stock MR2 Spyder.
Thanks in advance for your input.
Topic starter
Posted : June 11, 2022 2:26 pm
If the vibration is that excessive,
I would question the build (engine)
I’m not sure what the balance shaft is
but
it sounds like it may have something to do with reducing vibration
just spitballing
Posted : June 11, 2022 7:02 pm
Most of the vibrations are going to come from the motor mounts. The stiffer the mount, the more those get transferred to the chassis.
Posted : June 11, 2022 11:12 pm
1
What - No "rotaries are smooth" comments for Gabe. I am kidding, though I like the rotary - not worth the swap.
As TJ stated Motor mounts are the transfer path - harder (typical aftermarket parts) - More vibes. And as CSPIDY noted (Guessed correctly) balance shafts are designed into engines to reduce vibrations - usually to attenuate some firing frequency mode - sometimes these really light up a chassis - particularly when you are already working on an engine that was not designed for a certain car. Removal of a balance shaft is not something I would suggest.
NVH is a really cool mystic art - I used to work in the field at GM. Once you plug in something other than a 1zz 2zz on stock-ish mounts, you are spinning the wheel.
I am not saying a good 2GRE swap (or other eng) won't be vibration free. I have only ridden in one V6 - I found the NVH acceptable for the other perf benefits - but the 2GRE can be a complicated swap from what I understand. Just saying once you rip off the stock/oem isolation - you have removed a lot of dedicated NVH work.
I recently had to replace the drivers mount (177 miles on chassis) the stock mount was my choice - though I contemplated DEVs previous Widow-weld post and should have done it - just lost the game with time. I have a single (both sides) Kirky urethane insert in my 1zz jdm swap - I find the vibes a little obnoxious at idle, but I am delicate - Ha.
Anyway - long reply - but the key is isolation and firing modes of the engine
Posted : June 12, 2022 6:45 am
Its for sure the aftermarket mounts that were made for the K20 swap. I had similar transmission and passenger side mounts from the same company and they were the less shore hardness version which I don't think was available for the K20 version.
The main culprit is with the passenger mount that is by the serpentine built side of the engine. It was unbearable even though I tried to put up with it as the resonance was so loud. I replaced it with a brand new stock mount and it toned it down a lot but it also removed the benefit of the stiffer mount when taking off from a start or getting on the gas. The stiffer mount made the gas pedal very responsive and it felt like a more powerful car. I miss it but my hearing is better for it.
I would say the window weld mounts I made were actually good compromise compared to the poly mounts.
Posted : June 12, 2022 9:31 am
As Dev said, the passenger -side mount makes the most difference relative to transmitting engine vibrations to the chassis. I started out with the full Innovative mount kit for my k20 swap (less vibrations than a non-balance-shaft K24), and found the vibration level to be pretty bad. Switching back to the OEM Toyota mount (which is internally-damped) made a huge improvement, even without changing the Innovative driver's side mount. I also got rid of the Innovative rear - mount and went with MAP's front and rear mounts. These manage rocking movements pretty well.
Dave
Posted : June 12, 2022 9:39 am
Also note that the main reason for removing the K24's balance shafts is that the oil pump that is part of the balance shaft assembly is not as good for extended high-rpm operation as the K20 oil pump. The K24 balance shaft/oil pump is fine for a K24 as long as you observe the original redline. When you swap you will need a Hondata ECU and you can set the fuel cut-off rpm to whatever you want. The balance shaft system probably doesn't use more than 1 or 2 HP at rated speed.
Posted : June 12, 2022 9:45 am