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Discussion Starter · #1 ·
After driving the 3 w/ 6MT for well over a year now, I was constantly being jarred by the jerkiness at the transition point from accel -> decel, and the jerkiness at low speeds crawling around parking lots/over speed bumps and such. I could FEEL the motor shifting around in the engine bay as it went through the full action of the rear motor mount / torque strut, and decided that given the smooth nature of the engine I could experiment with filling motor mounts to stiffen it, reduce play, and hopefully add a more engaged feel when shifting/accelerating/engine braking.

My first attempt was a cheap $35 RockAuto motor mount which I filled with silicone adhesive. This was ultimately ineffective, as silicone is a ridiculously soft material, and just wound up working its way out of the motor mount over time. So, I went and bought some 3M WindoWeld, which has a ~60 shore hardness rating, and figured it would be a much less expensive mount compared to the Corksport/James Barone Racing urethane mounts. In addition, the 60 shore hardness of the urethane combined with the natural rubber already moulded into the mount should provide a much softer and more forgiving motor mount for daily driving comfort.

BOY WAS I WRONG.

I installed my urethane-filled mount, and everything was fine for 90% of the time while driving. It moderately improved the shift feel, only transmitted about 5% more vibration under acceleration, reduced the jerkiness by about 30-50%, and reduced the sloshiness of the engine on transition from accel -> decel by a lot.

BUT THE IDLE! Oh my goodness the idle. 500 rpm idle speed + Florida summer heat working the AC compressor makes the car vibrate unreasonably. The worst part is when the idle is around 800-900 RPM during cold startup, the car is almost vibration free! But as soon as the idle falls to 500 and the AC kicks on you can't ignore it shaking the whole car and making a wretched noise as it does. I was honestly a little afraid because of how aggressive the vibration noise was that I was gonna shake/break something loose.

Now, I will be experimenting with drilling holes in the mount and reinstalling it some other time, but for the time being the stock-design motor mount will go back in with no filling and stay that way. I used to have a Dodge Neon that shook almost this bad, and I SPECIFICALLY bought this car so it wouldn't wind up acting like or even reminding me of the $#!theap that car was.

As for alleviating the jerkiness of the motor, I can now more accurately attribute about 50% of the jerkiness to the fuel maps programmed into the engine. Almost as soon as you let off the throttle, the engine wants to switch over to a super-lean engine braking cycle to conserve fuel. This foot on - foot off action happens a LOT when cruising parking lots, and as such will still happen with a stiff motor mount. Not as much, because the engine is restrained not to flop around, but it does still happen. Maybe an OV Tune alleviates that? Not sure, not too eager to try.



tl;dr, solid motor mounts are a good mod, but if you idle with AC you will shake the whole car, and it will (in my opinion) RUIN the car as a daily driver. On top of that, it doesn't completely fix the jerkiness of the car, and what improvements it did yield were COMPLETELY overshadowed by the horrible idle vibrations.



Seriously ask yourself if you want your car to act like that before you buy! I am very glad I didn't splurge for the pro urethane mounts, because I would have been out an extra $80-$100 and hate it.

(If it's not your daily driver, you don't use AC often, or if you like to go FULL RACECAR, though, 3M WindoWeld is only ~$20 and only takes a couple of days to cure)

Long post, and highly opinionated, but any feedback or questions are welcome!
 

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This is why its been recommended that you find a way to move the idle rpm to ~800 or so when using stiffer mounts. Unfortunately you need to do this through the ECU.
 

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Discussion Starter · #3 ·
This is why its been recommended that you find a way to move the idle rpm to ~800 or so when using stiffer mounts. Unfortunately you need to do this through the ECU.
That's exactly what I was thinking, but since I'm less than 50k on the clock right now I'm well within powertrain warranty and don't wanna mess with ECU tuning just yet. Down the road, though I anticipate that I will, and that'll be a primary order of business.
 

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I 3M filled my rear torque mount years ago and Love it when coupled with a higher idle speed.

I had OV Tune mine to idle @ 950rpm. No more idle vibrations with the stiff mount. Motor still moves a bit too much under max torque shifting but it's doable vs the stock sloppy mount. Mine started to flex too much by like 10k miles.

I recommend you get a tune. Not only will it unlock power if you tune for premium fuel, it will raise the idle and allow you to enjoy that engine mount again.

Having the ability to tune the car for later is a plus. Or you can sell the tuning kit if you decide to sell the car and get a good chunk of cash back. It's a no brainer.
 

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Discussion Starter · #6 ·
I 3M filled my rear torque mount years ago and Love it when coupled with a higher idle speed.

I had OV Tune mine to idle @ 950rpm. No more idle vibrations with the stiff mount. Motor still moves a bit too much under max torque shifting but it's doable vs the stock sloppy mount. Mine started to flex too much by like 10k miles.

I recommend you get a tune. Not only will it unlock power if you tune for premium fuel, it will raise the idle and allow you to enjoy that engine mount again.

Having the ability to tune the car for later is a plus. Or you can sell the tuning kit if you decide to sell the car and get a good chunk of cash back. It's a no brainer.
Now here I am a year and a half later, out of the warranty, thinking about doing the OV Tune like you said. I dug the old filled motor mount out of the bin and think if I request OV Tune raises the idle to 950 like you said, I may go for it.

Does the OV Tune address the annoying jerky throttle response? When I'm in traffic (not too bad in Jax, FL, which is where I live, too) it pisses me off that the throttle stays open for a moment after I let off the throttle, then jerks shut, making it difficult to drive smoothly at part-throttle situations.
 

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Now here I am a year and a half later, out of the warranty, thinking about doing the OV Tune like you said. I dug the old filled motor mount out of the bin and think if I request OV Tune raises the idle to 950 like you said, I may go for it.

Does the OV Tune address the annoying jerky throttle response? When I'm in traffic (not too bad in Jax, FL, which is where I live, too) it pisses me off that the throttle stays open for a moment after I let off the throttle, then jerks shut, making it difficult to drive smoothly at part-throttle situations.
you can post that question directly to OVT
https://mazda3revolution.com/forums...td/233717-welcome-orangevirus-tuning-ltd.html
 

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Discussion Starter · #8 ·

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Discussion Starter · #10 ·
Just FYI yes OVT does throttle calibration. Not sure if it will fix your problem though.
Yeah, I saw that in the purchase page, I just couldn't find any information as to what exactly "throttle calibration" means... I assumed it was similar to a pedalcommander or the throttle map update where the throttle body reacts more drastically to a lesser throttle input on the pedal. Am I thinking right?
 

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You really gotta play around with the idle and find the sweet spot that works best for you.

I currently have it set to 800rpm using the Corksport rear mount. For some reason, it gave off different frequencies of vibration then the OEM 3M injected setup and required idle adjustment to make it smooth again when the AC cycles on / off.

Without AC it’s smooth as butter at all idle RPMs we tried, so it’s the extra load of the compressor that you’ve gotta tune for.

I don’t have the jerk you mention. Mine is smooth with throttle inputs, but maybe that’s the tune, so you’ll just have to wait and find out if it gets better for ya.


I 3M filled my rear torque mount years ago and Love it when coupled with a higher idle speed.

I had OV Tune mine to idle @ 950rpm. No more idle vibrations with the stiff mount. Motor still moves a bit too much under max torque shifting but it's doable vs the stock sloppy mount. Mine started to flex too much by like 10k miles.

I recommend you get a tune. Not only will it unlock power if you tune for premium fuel, it will raise the idle and allow you to enjoy that engine mount again.

Having the ability to tune the car for later is a plus. Or you can sell the tuning kit if you decide to sell the car and get a good chunk of cash back. It's a no brainer.
Now here I am a year and a half later, out of the warranty, thinking about doing the OV Tune like you said. I dug the old filled motor mount out of the bin and think if I request OV Tune raises the idle to 950 like you said, I may go for it.

Does the OV Tune address the annoying jerky throttle response? When I'm in traffic (not too bad in Jax, FL, which is where I live, too) it pisses me off that the throttle stays open for a moment after I let off the throttle, then jerks shut, making it difficult to drive smoothly at part-throttle situations.
 

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I remember the days when we could just turn a screw on the side of the carburetor and set the idle to whatever we wanted. Or turn the distributor to advance and retard timing to work best with different types of gasoline.

Ah, the good old days...

Of course, we also used to walk to school...uphill...both ways...in the snow...and we liked it!
 
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