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I have not put the car through it's paces since the install but I figure some of you are probably interested in the solid bushed install vs the non bushed install. I drove the car for normal transportation last night, approximately 1 hr or a little more. Absolutely no down side perceived as far as vibration and noise. Maybe its the placebo effect but the car just felt tighter and more "focused". I originally wanted to do this mod because of the 4 times I launched the car at the dragstrip twice no hop (once with modded ECU and once with stock ECU) once one hop on launch and once 5 hops on launch. I am not sure when I will get to the strip but I'll will definitely post my impressions. I am hoping this will eliminate all the hopping.

Since I have a spider I could not see the engine movement while driving. But before the mod at idle the engine used to shake like a heroin addict who hadn't had a fix for three days. Now if you didn't hear the engine visually it's hard to tell if its running. I watched through the air inlet just behind me when I put in gear and no movement. It would move once when the clutches engaged but that was it. So far very happy with the mod.
 

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Find this video it helps a lot.
From the video you can see the bolt has a lot of movement in the engine mount hole, is it possible to insert a metal sleeve to it to reduce the movement?

https://youtu.be/tcSweYCuv1M

This is the video I was referring to about "adjusting the handling by offsetting the drive shafts"

Anybody can explain more on that please?
 

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Thanks to [email protected] for ordering a spare rear mount in 2 days.



Planning on installing Black (track) insert into this spare rare mount.


Upon analysis, this brand new rear mount has ZERO thread markings in the center channel. So, good start for the purpose of this experiment. :)

 

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Onto the experiment, I inserted the Black insert.

If there is any movement on the rear mount due to the lack of a channel bushing that would theoretically center the vertical chassis bolt, there should be new thread markings on the interior channel (like the video) and potentially some metal wear from slide friction between rear mount and the washer bushing and/or chassis right?

With ZERO thread markings in the channel of this brand new mount, we should see what happens. i did mark up the SS bushing side surface fo the rear mount to maybe see if I see any disruption of the ink due to friction wear.


One potential variable that may affect this experiment is the Powerflex insert, whether Yellow or Black, has the polyurethrane circular disk "foot" which contacts the chassis on final retorque. Would this large amount of polyurethrane surface area prevent the rear mount from sliding fore and aft minimizing bolt travel in the center channel?



Please feel free to provide insight or feedback if you like. :)

Onto the garage! :)
 

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Btw, this is the chassis contact point and surface area of the lower part of the rear mount *without* the insert for reference.


 

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Perhaps a stupid question but are we sure that the couple mm play in the middle is not intentional and doesn't serve a purpose?


Regardless, appreciate the effort Docron :grin2:
 

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Perhaps a stupid question but are we sure that the couple mm play in the middle is not intentional and doesn't serve a purpose?


Regardless, appreciate the effort Docron :grin2:

Thats what i was thinking too.....why not put a delrin or poly bushing in that channel to absorb the movement?

Anywho, done!
Time to hit the road. :)
 

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So I inserted the Black (track) insert yesterday and drove around yesterday and today really hard, much harder than the yellow insert the previous before that. I wanted to really see if there was any significant difference or improvement over the yellow insert and more importantly, if there was any noticible increase in NVH.

1. I guess there is a difference between black and yellow under very hard acceleration in terms of crisper throttle response and butt dyno power especially in the lower power band and lower gears when torque is applied the most. Under casual or sem-spirited acceleration, I could not tell too much of a difference between yellow and black. I do have a track day coming up in 4 weeks so I will definitely try to determine if there is any significant difference over NO insert.

2. I tried to determine drivetrain torque out of a dead stop through 4th, out of rolling second gear thru 4th and holding steady acceleration throug 4th, 5th and 6th. Regardless of yellow vs. black, you can tell that the engine moves less in the rearview mirror during acceleration as well as seemingly increased linear push of power through the lower gears.

3. I did not notice any significant increase in NVH if any at all. Besides the rumble of the exhause and engine as well as the road surface through the steering wheel, i could not detect any increase in NVH while cruising at 30, 40, 50, 60, 70, 80+ mph. Nor could I detect any NVH during casual, spirited or hard acceleration. So I think whether yellow insert or black onsert, we are pretty much safe from any undesirable NVH.

Onto the experiment with pics. :)
 

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Ok, so in the posted video, in my pics and Spidermans observations, we do know that the vertical bolt of the rear mount in the metal channel moves and contacts the metal channel as evidenced by bolt thread markings. Why AR engineering designed the rear mount bolt to have that much play in the channel much less let it contact the channel is puzzling but like John asked, was the design intentional? For driver comfort, to mitigate NVH? It must also be know that there are two other engine mounts in the bay so its not like this rear mount is the only absorbing engine mount.

Let's first look at the thread markings that were created before any insert was used. Its located at 12o'clock. Pretty deep and extends throught the entire height of the channel. Is this really concerning from even a bone stock rear mount standpoint? No TSB yet....lol.



Notice at 11 o'clock, there is a new set of markings....this was created with the yellow insert after 3 days of relatively hard driving. But, from the looks of it, the thread markings are only 2/3rds into the channel.

Now let's line up the yellow insert rear mount next to the black insert rear mount.
After 2 days of really heavy driving, there were very faint thread marks and only 1/4th extended into the channel. You have to look very carefully and closely to really see thread marking in the balck insert rear mount.


 

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Let's take a closer look at the new thread markings in the yellow insert and the balck insert and how much the markings extend into the channel.

Bottom view:



Top view:



For those of you following, i did try and color stripe with a purple sharpie on the top surface of the channel of the unmarked new rear mount to see if if there was sliding. i could not tell if there was sliding metal by studying the purple sharpie lines. however, since we now can assume based on the thread markings only a quarter up the channel with the black insert, we shouldnt see any sliding smears of the purple sharpie lines.
 

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My summary (and please anyone else, provide their interpretation):

Stock without insert: bolt contacts center channel a lot.
With Powerflex insert, less bolt travel and movement with less contact with black < yellow.

I don't know if a surrounding bushing press fit in the channel, whether metal, Delrin or Polyurethane would be advantageous or not or would significantly imcrease NVH or not. It would definitely keep the vertical bolt centered in the channel but also how feasible would it be for the weekend garage warrior.

But, with either insert, there is defInitely less movement than not having any insert at all.
I will drive another few hundred miles as well as on the track for the next month with the Black insert and restudy the rear mount and report my findings.

But bang for the buck, this is a great mod.

I am afraid of the fixed mount option....i installed a fix mount on my Abarth, went for a drive and immediately removed it and threw it in a basement tote. Waaaay too much NVH and made driving intolerable only after one drive. Just my humble $0.02 USD. :)
 

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Thanks for taking the time to do this, Docron.

A few stupid questions (partly because I've been too lazy to take my car apart to check):
-so, there is only one rear mount (or is your install just typical for two)?
- your observations from driving both black and yellow (albeit only briefly) now? Comparison?
- could the large hole relative to the bolt be designed in as either an assembly alignment thing (like is done with subframe bolts on most cars these days), or perhaps to protect the engine or chassis from a sudden major jolt (the bolt will move in its hole, dampened by bushing and compression)? Basically to prevent shear in such a situation?
- could the difference in interference markings on the post-bushed mounts be just from minor installment differences (alignment of engine, mount, and bolt upon reassembly)?
- given that you have 2 hard years driving on the original mount, and two days on the yellow-bushed and brand new black-bushed version, do you not think that the markings will go all the way through the hole and be much deeper (like the original one) after a couple of years?
- how badly was the bold thread mangled where it contacts inside the hole? I'm not worried about the mount, but bolt failure would be a definite possibility (long term, and even in the stock configuration).

None of this is meant as a criticism of the mod. I think it's a great idea and plan to do this myself at some point. But I ask these questions in the interest of discussion and knowledge.

Thanks.
 

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My summary (and please anyone else, provide their interpretation):

Stock without insert: bolt contacts center channel a lot.
With Powerflex insert, less bolt travel and movement with less contact with black < yellow.

I don't know if a surrounding bushing press fit in the channel, whether metal, Delrin or Polyurethane would be advantageous or not or would significantly imcrease NVH or not. It would definitely keep the vertical bolt centered in the channel but also how feasible would it be for the weekend garage warrior.

But, with either insert, there is defInitely less movement than not having any insert at all.
I will drive another few hundred miles as well as on the track for the next month with the Black insert and restudy the rear mount and report my findings.

But bang for the buck, this is a great mod.

I am afraid of the fixed mount option....i installed a fix mount on my Abarth, went for a drive and immediately removed it and threw it in a basement tote. Waaaay too much NVH and made driving intolerable only after one drive. Just my humble $0.02 USD. :)
I believe metal spacer similar to the one I made is the best way to accurately locate the mount. I have been daily driving my car to work plus some spirited driving thrown in also and have experienced no ill effects. The car feels more planted and stable going through corners. I did not see where Docron noticed any differences in vibration/noise between the black and yellow so I am assuming not much noticeable difference. The change between yellow and black might be more noticeable with a bushing as with my setup. I would think the gap in mount sleeve was intentional but I can not think of any good reason to leave the slop for my use of the car. My bushing was listed as for use with the 4c and the Guilietta. The actual package only says Giulietta. So maybe the motor mount is used for both cars. I wonder if the Guilietta uses the same mount with a larger bolt?
 

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I believe metal spacer similar to the one I made is the best way to accurately locate the mount. I have been daily driving my car to work plus some spirited driving thrown in also and have experienced no ill effects. The car feels more planted and stable going through corners. I did not see where Docron noticed any differences in vibration/noise between the black and yellow so I am assuming not much noticeable difference. The change between yellow and black might be more noticeable with a bushing as with my setup. I would think the gap in mount sleeve was intentional but I can not think of any good reason to leave the slop for my use of the car. My bushing was listed as for use with the 4c and the Guilietta. The actual package only says Giulietta. So maybe the motor mount is used for both cars. I wonder if the Guilietta uses the same mount with a larger bolt?
Good to know.
Not likely a larger bolt -isn't the engine casting the same as ours? So the engine side bolt hole would match ours.

The more I think about it, the more I think it's an allowance for assembly. Like the way subframe mounting points have huge play in many modern cars. I wonder if there is a bushing kit for the bolt for the Giulietta? That would be just the thing...

Oh Chris??? :wink2:
 

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Discussion Starter #57 (Edited)
Good to know.
Not likely a larger bolt -isn't the engine casting the same as ours? So the engine side bolt hole would match ours.

The more I think about it, the more I think it's an allowance for assembly. Like the way subframe mounting points have huge play in many modern cars. I wonder if there is a bushing kit for the bolt for the Giulietta? That would be just the thing...

Oh Chris??? :wink2:
The Giullietta Mount is Identical for the 4C. When I was pushing Powerflex they said they had just started on the Giullietta and it would apply to the 4C. The part numbers are identical for the 4C and Giullietta for the actual mount according to an EU parts lookup.

I suspect as 4Canada stated its a build tolerance. I am looking at nylon or urethane shims to insert. I am hesitant utilizing a metal shim due to possible noise and difficulty of install. I also want the mount to have some "give". You are transferring a lot of loads to the other engine mounts and I want to disperse the load to the upper two mounts in a gradual fashion as to not shock the drive-train and upper mounts.

What may be a good fix is a simple silicone sleeve (we have plenty of silicone). This will slide on the bolt and fill the majority of the void. It will also be a bit more forgiving in regards to high transitional loads on the upper mounts.
 

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I was already thinking that I would be hesitant to use the black insert with my solid bushed setup. As I stated before I have not noticed much if any change in noise or vibration with the yellow insert but it is actually pretty soft. All that might change with the solid bush and black insert.
 

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I had the black insert installed today. In a shop, on a lift, with an impact gun, less than an hour! As others have stated, best bang for your buck mod hands down!

How did your channel look like?
 
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