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Discussion Starter #1 (Edited)
I had never really considered an engine damper on my Miata but the motor is tired and it tends to shake a bit at lower rpms. I've got low compression on one cylinder, so my theory is that on the relatively slower stroke of low rpm, compression is impacting the combustion cycle. At higher rpm and a faster stroke, the rings don't have as much time to bleed off pressure and the compression is a little better so the motor smooths out. At just about anything other than idle, the car feels and sounds perfect. Even at idle the rpms are consistent, just a little rough. In trying to get rid of the shake, I changed out the motor mounts, which were both broken. Minor improvement.

I've done a bit of research on dampers and found there are three common types.

Mechanical - Several types of mechanical I found. Back in the muscle car days, guys would weld or bolt chains around the mounts to limit travel upwards. The mounts were able to compress as they normally would. There are also piston type mechanical dampers, that use essentially bumpstops. I bought one of these off eBay just to check it out.

Gas - gas shock style, like a hood raise shock. These come at a specific pressure and pretty much absorb some of the movement by resisting with air pressure. As you compress the shock, the pressure increases, increasing dampening with increased compression.

Hydraulic - oil shock style, like suspension shocks. These are valved, again usually at a specific rate and not adjustable. Since the valving is designed to increase the dampening rate and that rate is the same over the length of travel, this is really the best option (and most expensive).

I bought a mechanical damper off eBay for $40. I'll try it out but don't expect this to do the job. I didn't know exactly what I was getting until I took it apart:



Here's the guts of the damper - it is pretty much two black rubber bump stops inside the shock body. The two white bushings are either nylon or delrin. The longer bushing is cut specifically for the Miata to get close to the proper distance, then the adjustment threads on the end fittings can be fine tuned to fit.



So the two bump stops limit the travel of that washer. Seems like a lot of force to be asking this assembly to absorb. It probably comes down to how well those bump stops do their job and how long they last. If they do start to break down, at least I can take it apart and replace them. I might end up pouring a couple RTV molds to see if silicone might work better.

The shock body came red anodized but I painted it to match my Valve Cover and Manifold.

I'm not sure I can install it exactly where it was intended because of my aftermarket intake. Might have to make custom brackets.

Anybody try out this POS model specifically?

Interested in specific experience with any damper - post up your story and a photo if you have one. If it helps at all - I'm interested.
 

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I don't mean to knock you down or anything, but wouldn't changing out the motor mounts be more effective than the engine damper?
 

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I bought the same thing. But, I am going to modify it, and remove the spacer (white thing) and substitute it with a rubber bushing. This way I get more damping from it, instead of bump stop it be more absorber style. PM, we should do joint project together.
 

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I have the same Ebay damper. Before my engine will shift under load (engine mounts are in good condition) and I had some clutch chatter due to the light flywheel I am running. After installing this damper, the engine remains stationary even at high RPM and my chatter is gone.

Found these videos on Youtube:
http://www.youtube.com/watch?v=laFiMYU5e-4
Without damper installed


http://www.youtube.com/watch?v=FSIjNoUKRJE
Damper installed
 

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Discussion Starter #5 (Edited)
I don't mean to knock you down or anything, but wouldn't changing out the motor mounts be more effective than the engine damper?
Very first paragraph of my OP, last two sentences. Already replaced mounts.

I bought the same thing. But, I am going to modify it, and remove the spacer (white thing) and substitute it with a rubber bushing. This way I get more damping from it, instead of bump stop it be more absorber style. PM, we should do joint project together.
I've taken it apart and now, understand it and last night installed it. I don't plan to change the design at all. In fact, I'm actually impressed with the design. The two rubber "bump stops" are actually what is compressing under load. You can actually twist the whole cylinder after you have it installed and preload the bumpers so that it starts out under a little compression. If you replace the spacers with another material that is more forgiving, you might not get the benefit of this design. I think it might be too soft. Too soft means movement and movement equals larger travel compression cycles on the bump stops. Give it a try like it came - you might be really happy with it. I am (so far).

I have the same Ebay damper. Before my engine will shift under load (engine mounts are in good condition) and I had some clutch chatter due to the light flywheel I am running. After installing this damper, the engine remains stationary even at high RPM and my chatter is gone.
I drove a little over two hours this morning and the difference is absolutely noticeable. The car doesn't feel any different at all while I'm driving. At idle, the damper holds the motor in place and vibrations at lower speeds are definitely reduced. Great mod for the money. I can expect the quality isn't stellar - good heim joints cost $40 by themselves.

Anyway, I removed the heat shield so I could modify it - I cut out the space for the damper to pass through.



Here is the damper installed:



I actually like the design of this bracket but would really like if it attached to the motor with more than one bolt. As it stands, the bracket itself really works like a big stiff spring. Combined with the damper tube, it does what it is supposed to - it stops my motor shake. I might look for some grade 8 hardware to replace the heim joint bolts.



And here's a shot from directly above the brake booster. I'm thinking I could make a nylon/delrin brake stop that clamps to the damper. I'm lucky to have the clearance around the STB and the brake lines.



Heat shield will be going back in soon.
 

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Ahhh I see now, my mistake
 

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Discussion Starter #8 (Edited)
That aluminum bracket wont last long....
http://clubroadster.net/vb_forum/showthread.php?t=33231&highlight=ebay+damper

It would be better if you attach the damper directly to your STB using steel seat belt L brackets. But your intake is in the way.....
They are steel brackets, not aluminum. Pretty heavy. Looks like they have been zinc coated. But that has got to be the same eBay kit and based on how it is mounted, that's exactly what I would expect to fail and where. There's a second bolt hole - I'm going to try to use it for another mounting point.

I don't think it would be better to attach to the STB because the STB really wasn't designed for taking loads like that. You want to attach it to chassis/frame structure - the Strut tower itself, which the supplied bracket does perfectly, it just looks like I need to worry about the material used on the motor side. Since the bracket that comes with the kit actually mounts under the STB directly against the tower, it couldn't get any more stable. Forcing the load path through the STB into the tower isn't the best way but it might work if the STB is strong enough, the damper works like it should, the motor doesn't shake much to begin with and your luck holds out. Personally, I wouldn't.
 

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There's a lot more to this than I previously thought. Going back now to read in detail. Thanks for making this thread.
 

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I have the same Ebay damper. Before my engine will shift under load (engine mounts are in good condition) and I had some clutch chatter due to the light flywheel I am running. After installing this damper, the engine remains stationary even at high RPM and my chatter is gone.

Found these videos on Youtube:
http://www.youtube.com/watch?v=laFiMYU5e-4
Without damper installed


http://www.youtube.com/watch?v=FSIjNoUKRJE
Damper installed
Wow, that's a dramatic difference.
 

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Very cool to see those videos. I have the red eBay kit in my garage. Thanks for the new motivation to install it.

Wasn't there a member here who used a golf cart shock mounted between the engine crane bracket and the shock tower?
 

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Discussion Starter #12
Finished up the heat shield and installed it.





Having to dip down under the damper makes a big enough hole that I wonder how much good this will even do. Certainly can't hurt.

Took a look at supporting the motor side bracket a little better than with the one bolt. I don't have a permanent solution, But I do have an idea for one.

There is a second hole in the provided bracket but it doesn't line up with anything. I pushed a nut/bolt through it in this photo:



The valve cover bolt is very close to this spot as well, so if I got a longer valve cover bolt, I could use it along with the damper bracket 2nd hole to get another solid mounting point. I just need to make a small steel bracket to bridge the gap. Looks like a simple section of L-stock will work fine.
 

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Very cool to see those videos. I have the red eBay kit in my garage. Thanks for the new motivation to install it.

Wasn't there a member here who used a golf cart shock mounted between the engine crane bracket and the shock tower?

yep

I used 1 club car DS shock, and 2 seat belt brackets from a 63 corvette seat belt kit haha.

I used the bolt location for the engine lift bracket, and drilled a hole in the strut tower brace and used some large washers and grade-8 hardware.



here is a pic when I was mocking it all up. It has pretty much eliminated the 2nd-3rd mis-shift issue. I ended up using two bolts on the strut bar tower to keep it from moving. I have had this setup now for quite a few miles with no issues.
 

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Guys.. golf kart dampers. Look it up. There is a how to/review somewhere buried on CR.

edit: yup ^
 

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Discussion Starter #15 (Edited)
Guys.. golf kart dampers. Look it up. There is a how to/review somewhere buried on CR.

edit: yup ^
Thanks but I'm not really interested since the mounting points don't physically work for me (intake) and I'm still not a fan of mounting a damper to a STB that wasn't specifically designed for side loads at that location.

That being said, here I am modifying the damper brace. Of course, this is an eBay damper and my STB is a Carbing. The price of failure is much lower with the damper in my case and I'm trying to increase stiffness by adding on reinforcing structure that won't impart new loads on the system.

I'll be keeping an eye on both the motor side bracket and the slop in the cylinder (there is none right now). This week I'll cut a couple inches of steel L-stock and drill a couple holes in it. Guess I need to find a valve cover bolt or two about 15mm longer. I've been meaning to replace all of them with grade 10.9 cadmium coated anyway - like everything else in the engine bay.

Anybody know what the thread pitch and length of the OEM Valve cover bolts are? I located a part number and torque specs, but can't find the printed length. Guess I will just measure one.
 

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Discussion Starter #16
Thought I would report back that I have had ZERO issues with my eBay damper - it's been installed since I started this thread and seems to be rock solid. It doesn't move at all and the mounting bracket doesn't show any stress I can see.

My motor now has 216,000 miles on it and I have nothing but positive things to say about the damper - it has done more than I expected it to do and it has lasted much longer than the price would justify.

 

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Thought I would report back that I have had ZERO issues with my eBay damper - it's been installed since I started this thread and seems to be rock solid. It doesn't move at all and the mounting bracket doesn't show any stress I can see.

My motor now has 216,000 miles on it and I have nothing but positive things to say about the damper - it has done more than I expected it to do and it has lasted much longer than the price would justify.


Link to the damper you used?
 

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So this work well I guess I'll add to my bucket list what the name on eBay or what ebay seller?
 

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Discussion Starter #19

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Hrmmm... wonder if it'll clear on a Mazdaspeed. Thanks!
 
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