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As I wrote somewhere else on the Forum, my PowerFlex bushing has made on and off throttle transitions seem less and smooth. Even in the passenger seat my wife noticed how much better the car behaves.
 

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This is what I have been owing you guys for some time now. The exact stiffness of the mounts. Here are the specs:

Stock: 50 ShA
Blue / street: 55 ShA (10% stiffer than stock)
Black / sport: 65 ShA (30% stiffer than stock)
Red / race: 75 ShA (50% stiffer than stock)

Maybe some insights from those of you who run these engine mounts?
Hello Rudi,
Is there a limit to the use of each mount? Can using the race mount for road use e.g. damage the engine because it's too stiff?
Do you feel a significant difference between sport and race?
I drive 20.000km and 2-3 trackdays a year. I have a standard exhaust, so a bit extra noise won't kill me :wink2:.
 

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Discussion Starter #23
Running too stiff engine mount on normal daily driving will have no benefit and just make the car harsher. Due to increassed rigidity and ShA stiffnes, also more vibrations are transmitted to other components (exhaust mounts etc.), which can cause cracking in the material after a prolongued use.

On the other hand, for the track and fast street driving, running soft engine mount with a lot of flex and movement will cause stress, wear and tear on it and the other components as well.

So it is the best to select the engine mount stiffness according to your type of driving. In your case I'd recommend 65 ShA (Black / sport). Barely noticable increase in harshness and decent rigidity increase over stock engine mount.
 

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Discussion Starter #24
Few weeks ago I drove clients bone stock 4C on a hometrack Grobnik. He wanted me to set a lap time with his car for his reference so I pushed it quite hard although it felt a bit wrong to me. The brakes, the seats, the feedback, tires, pretty much everything felt wrong. :LOL:

Regardless of my best effort I was still 9s behind our GMS 4C. First thing I have noticed was the lack of confidence and feedback driving stock rear arm rubber bushings. The second thing I noticed, was how violently the car kicks on the upshifts due to the stock engine mount. So I asked myself how many of you still run stock engine mounts? Do you notice any kicking on the upshifts? I bothered me a lot, it felt like it is gonna tear out the engine and the car wasn't even remaped.
 

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You'd be surprised what people can get used to... i.e. without having a comparison, humans are fairly adaptable to most things.

To be fair, I've mainly used stronger/solid engine mounts (or engine braces) on my other track cars due to what it did for shifting. In higher g-loaded corners, the movement of the engine would make it car to get into certain gears (powering out of a right hand corner in 2nd gear, where you need to grab 3rd before you are completely straight for example). While I'm not running super sticky tires on the 4C, the lack of manual shifting would make my normal use case for stronger engine mounts not as important.
 

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@GMS - Funny you say that, I have been thinking just how violent/rough the shifts are..... Partly this is because I have been driving a big 2019 truck around that has a super smooth transmission. (but the braking really annoys me as it is not consistent and a bitch to do smoothly).... I remember the first time on track with the rear bearings, you could feel it INSTANTLY! So much nicer feeling and confidence inspiring. So, I might actually have to try the engine mounts...
 

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Discussion Starter #27
Shifts definitely feel much better with upgraded engine mount. Stock are so soft that when you are accelerating the engine is tilted foward all the time and the moment you shift, the torque drops and engine kicks back and then forward again and that is why the shifts feel jerky. Launch control? It feels downright scarry
 

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More Gale goodies installed... This time the engine bushing. This is one of those WTF things Alfa did. The OEM bushing is soft, which is fine for smoother shifts, but has a huge amount of slop between the bolt and actual bushing. I got the Sport version from Gale as part of a larger order. It is a fairly quick press job to push the old bushing out, and install the new one. I don't have a press, so I had my local race shop do it for me. Install and removal is quite easy. The hardest part is simply pushing/rotating the engine enough to get the part reinstalled. I had to end up "lifting" the engine with my jack to finally get the bolt in.

Simple job, and one of those no brainer orders if you have other Gale parts coming (like rear arms). I'm excited to see how it effects the shifts, but it will be a day or two before I get everything done...

110568

110567
 

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Just took the car for a quick run. Two initial observations... 1) Idle is definitely rougher from a NVH perspective, and notice more vibration in the whole car and steering wheel. Once you push the giggle stick, you really don't notice it 2) The few shifts I did do (local street only), things feel smoother when shifting. Doesn't seem to upset the car balance as much. I definately need more time to truly form an opinion.

@GMS - Stupid question, does that small aluminum spacer go on top of the bushing, or under?
 
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Discussion Starter #30
Engine mount will be a bit more rough on idle, yes, but it shouldn’t be too bad, especially with the medium compound mount you run now. As you mentioned, on the go it is hard to tell the difference. As usually, there is a trade off between comfort and sportiness. With 265 semislicks at the rear, I wouldn’t go with softer engine mount as the engine tilting on acc. / decc. is already pretty bad on stock car with much less grip from tires. The stock metal spacer remains in the same position as it was (top).

Try a launch control to see the difference and smell the clutch. :D
 

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Ahhh, fudge. I think I put it on the bottom as I couldn't remember which way it was when I took it out (doh), which could be why i'm getting more vibration... Will check and swap it if needed...

Is it wrong of me? I have never done a full launch before.... :whistle:
 

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Just took the car for a quick run. Two initial observations... 1) Idle is definitely rougher from a NVH perspective, and notice more vibration in the whole car and steering wheel. Once you push the giggle stick, you really don't notice it 2) The few shifts I did do (local street only), things feel smoother when shifting. Doesn't seem to upset the car balance as much. I definately need more time to truly form an opinion.

@GMS - Stupid question, does that small aluminum spacer go on top of the bushing, or under?
Tougher idle definitively, but not in a unpleasant way. However I wonder if the TCU should be changed, shifts are not THAT smooth. Opinions?
 

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My transmission control unit (TCU) was recently updated to the newest firmware/software. I had been running the original one since 2015, and have never had an issue (i have the cooling duct on the side skirt). When they upgraded, I swear it was far rougher when shifting gears high up in the RPM range. I don't know if it was because they had the car for more than a month to repair, and i just forgot or it was really an issue.... So I don't really know.... Give me some time to really thrash the car and I can give better feelings.
 
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So I have gotten a few hours of driving the car with the Sports Engine Bushing. I'm convinced that they specifically designed the OEM bushing to be larger than the bolt, to prevent idle vibrations from shaking the car. The engine isn't the smoothest in the world, and the CF transfers A LOT of vibration easily. So the engine can rattle and vibrate quite a bit at idle, and that slop allows you to decouple the engine from the chassis. When you add the GMS bushing, you recouple the engine, so you will notice that things shake quite a bit more at Idle. However, as SOON as you tap that throttle, it goes away.

Once you start shifting and pushing RPM, you barely notice the engine moving as you slam the gears at 6000 rpm (unlike before). So you don't notice the engine rocking as much, and the shifts (when in Auto) are smoother. I have about 3 weeks before I can get back on track to really see how it preforms, but so far so good...
 

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Discussion Starter #36
Thank you for your feedback and interesting observation. I believe I will have to re-calibrate my observation, as I would desribe the increased vibration with GMS engine mount in idle, as minor, barely noticable. :D
 
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