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Hardrace Gen 5 Engine/Transmission Mounts


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Hardrace have a new set of engine and transmission mounts for the 5G...

 

[ATTACH]201021[/ATTACH]

 

[ATTACH]201022[/ATTACH]

 

[ATTACH]201023[/ATTACH]

 

[ATTACH]201024[/ATTACH]

 

I haven't had a chance to try this kit yet, but at least one set is being installed soon and I will report back on how that worked out. Has to be easier than following in Big Bopper's footsteps! :eek:

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Obligatory '[URL="http://legacygt.com/forums/showthread.php/2008-gh8-238668.html?t=238668"]build thread[/URL]' Increased capacity to 2.7 liters, still turbo, but no longer need spark plugs.
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Hardrace have a new set of engine and transmission mounts for the 5G...

 

[ATTACH]201021[/ATTACH]

 

[ATTACH]201022[/ATTACH]

 

[ATTACH]201023[/ATTACH]

 

[ATTACH]201024[/ATTACH]

 

I haven't had a chance to try this kit yet, but at least one set is being installed soon and I will report back on how that worked out. Has to be easier than following in Big Bopper's footsteps! :eek:

 

...more parts to add to the list :lol:. I found the parts (7751, 7737, and 7720) on the Hardrace AU site, but how can these sourced in the US? Also, the AU site says these are for AT use, but there shouldn't be any issue w/our manual LGTs over here right?

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I don't know if the trans mount will be the same. I feel like the mini-6MT mount should be the same as the traditional 5MT item. No idea who handles this stuff in the USA I'm afraid. The two 'engine' mounts that bolt to the bellhousing and the one above the turbo are the same MT vs. AT, that much I can tell you. If I get more info I'll share it with you guys.
Obligatory '[URL="http://legacygt.com/forums/showthread.php/2008-gh8-238668.html?t=238668"]build thread[/URL]' Increased capacity to 2.7 liters, still turbo, but no longer need spark plugs.
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Try pulling something fairly heavy across your floor with a bungee cord. As you apply tension to the cord, it takes less force to stretch it than to overcome the inertia of the load. After a bit more force has been applied the inertia is overcome, and the object moves with not only the pulling force you're applying but also all the kinetic energy stored in the cord. So, the load jumps forward and then stops again as the energy in the cord is used up and inertia again exceeds your pulling force.

Now apply that idea to the car, where the force is engine torque, the load is the mass of the car, and the bungee cord is all the rubber bits fixing the powertrain to the body of the car.

 

TL;DR Improves throttle response and traction.

Obligatory '[URL="http://legacygt.com/forums/showthread.php/2008-gh8-238668.html?t=238668"]build thread[/URL]' Increased capacity to 2.7 liters, still turbo, but no longer need spark plugs.
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Try pulling something fairly heavy across your floor with a bungee cord. As you apply tension to the cord, it takes less force to stretch it than to overcome the inertia of the load. After a bit more force has been applied the inertia is overcome, and the object moves with not only the pulling force you're applying but also all the kinetic energy stored in the cord. So, the load jumps forward and then stops again as the energy in the cord is used up and inertia again exceeds your pulling force.

Now apply that idea to the car, where the force is engine torque, the load is the mass of the car, and the bungee cord is all the rubber bits fixing the powertrain to the body of the car.

 

TL;DR Improves throttle response and traction.

*potential energy stored in the cord?

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Try pulling something fairly heavy across your floor with a bungee cord. As you apply tension to the cord, it takes less force to stretch it than to overcome the inertia of the load. After a bit more force has been applied the inertia is overcome, and the object moves with not only the pulling force you're applying but also all the kinetic energy stored in the cord. So, the load jumps forward and then stops again as the energy in the cord is used up and inertia again exceeds your pulling force.

Now apply that idea to the car, where the force is engine torque, the load is the mass of the car, and the bungee cord is all the rubber bits fixing the powertrain to the body of the car.

 

TL;DR Improves throttle response and traction.

 

your example is static vs. dynamic friction - the static coefficient of friction is larger than the dynamic one - so it takes more force to get the object sliding than it does to keep it sliding.

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Which doesn't apply to a car, on wheels. The entire point of a wheel is to dramatically reduce static friction.

 

The rubber bits absorb the energy that would otherwise break things or loosen clutch linings or tires (wasted as heat) and release it some time later. While that effect might feel less good and may result in drive train deformation that is undesirable when taken to an extreme, if does NOT hurt performance. The opposite in fact, because the firmer your bushings are, the more work your clutch and tires have to do, and the more energy is wasted as heat.

 

I hate drive train slop too... But its not going to help acceleration to take it out. ;)

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It's kinetic energy once it's at work. Potential energy is stored, available but not in use. I could have been more clear but didn't think it necessary.

 

And yes, there is coefficient of friction to think about in my example (just as there is in an engine mount) but I was trying to keep it simple. Yes, a more accurate way to describe the effect would be that the cord's force plus that of the constant pull is needed to overcome both the static friction of the load on the floor and it's inertia, and that once the force from the cord had dropped to a certain point it would no longer be enough to overcome the dynamic friction, at which point it would stop until sufficient potential energy had again accumulated in the cord to again overcome static friction and start it moving again.

Mass moment of inertia is enough of a factor for the illustration and it applies to the example of the load on the floor and the powertrain. While internal friction does exist within the engine mounts it's tiny compared that in the example, making the analogy more of a stretch of the imagination than necessary. The way that friction makes the load dragged by bungee behave in a more obvious way, just makes the demonstration more effective.

 

Anyway, the phenomenon is colloquially known as 'rubber-banding'. Lots of info on that concept if anyone wants to Google it.

Obligatory '[URL="http://legacygt.com/forums/showthread.php/2008-gh8-238668.html?t=238668"]build thread[/URL]' Increased capacity to 2.7 liters, still turbo, but no longer need spark plugs.
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Which doesn't apply to a car, on wheels. The entire point of a wheel is to dramatically reduce static friction.

... which is one reason I didn't mention friction.

The rubber bits absorb the energy that would otherwise break things or loosen clutch linings or tires (wasted as heat) and release it some time later.

That might be so, but it's not the entire reason why they are designed that way. And, since the rubber bits do not absorb or return energy with 100% efficiency, some power certainly is lost in them compressing and expanding in use.

While that effect might feel less good and may result in drive train deformation that is undesirable when taken to an extreme, if does NOT hurt performance. The opposite in fact, because the firmer your bushings are, the more work your clutch and tires have to do, and the more energy is wasted as heat.

 

I hate drive train slop too... But its not going to help acceleration to take it out. ;)

It's a question of degree. Look at spring-wrap on a leaf spring car to see an extreme example. Torque applied from the engine will move the items that have the least resistance or inertia. If you have say, summer tires on ice, that will be to spin the tires and not move the car. If you have summer tires on warm tarmac, the torque from the engine will try to rotate the entire powertrain before moving the car simply because it has less inertia. What then happens is rubber-banding. The mounting system loads up until it takes less force to move the car forward than to deform the rubber mounts any further. When that happens the mounts unload and drop their force onto the tires as well. You see two things happen. One is that there is a momentary delay before the car starts accelerating, during which time the mounts are being loaded up. You feel this as a kind of lag in the driveline. The second is that when the car does start moving there may be a bit more force than you were anticipating. It might not make too much of a problem on an AWD car with an excess of traction but on 2WD vehicles it can be enough to overpower the tires momentarily. In really bad cases it can cause the wheels to hop as the mounting system loads and unloads at their resonant frequency.

 

I agree that unnecessarily hard mounts will cause more load on components like the clutch and CV joints etc. I'd argue that mounts too soft for the torque the powertrain can generate introduce cyclic loads on these components just as likely to cause their early failure. I think it's pretty easy to understand that as torque is increased, the mounts should be stiffened to match so that deflection is kept within reason.

Obligatory '[URL="http://legacygt.com/forums/showthread.php/2008-gh8-238668.html?t=238668"]build thread[/URL]' Increased capacity to 2.7 liters, still turbo, but no longer need spark plugs.
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:eek:

 

I didn't say its not worth doing... Just that its not going to help you accelerate faster. Drive line slop vs shock loading parts, nvh isolation vs driver feel, directness vs durability. All great considerations. It just isn't going to help actual acceleration in real world driving.

 

So uh.. chill... :cool:

 

That rubber band effect actually helps you launch, especially in an AWD car on dry pavement. Also it helps keep your transmission from grenading and axles from snapping. There are pros and cons... Pick your poison ;)

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Chill? You haven't seen me upset this far.

 

No-one is talking solid mounts here, just stiffer. WTF? I just posted some products you guys might be interested in. I'm not selling them. Do your own analysis on the benefits.

Obligatory '[URL="http://legacygt.com/forums/showthread.php/2008-gh8-238668.html?t=238668"]build thread[/URL]' Increased capacity to 2.7 liters, still turbo, but no longer need spark plugs.
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Gentlemen, lets take this discussion to a separate thread. This sticky thread is a place to deposit info on parts that are available for our cars, not to debate the merits of hard engine mounts. I will start a thread and move some of these posts to it.
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I've just remembered why I didn't come here for six months or so.
Obligatory '[URL="http://legacygt.com/forums/showthread.php/2008-gh8-238668.html?t=238668"]build thread[/URL]' Increased capacity to 2.7 liters, still turbo, but no longer need spark plugs.
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I had solid motor mounts in my previous car and it transferred all the engine vibration to the frame of the car and onto me.

 

Will these mounts give the same results?

 

I'm all for better mounts but I'll never go back to solid mounts again.

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These are not "solid" motor mounts like a solid metal mount or polyurethane mount with a durometer hardness of >95, these are "hardened" rubber mounts that are approximately 150% stiffer (per www.hard-race.com.au) than the stock rubber mounts. They have a durometer hardness of about 80. They still have some give in them and will still isolate higher frequency engine vibration that would be transmitted throughout the chassis with "solid" type mounts. They are meant to keep the drivetrain from moving around as much as it does with the stock mounts under acceleration and deceleration forces.
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I don't think the example used to explain what's going on is particularly relevant. They are engine/transmission mounts - they prevent the drivetrain from moving around too much. The OEM ones are designed to manage the vibrations/motion encountered for normal use and to reduce NVH - as you increase the power output or drive very aggressively, they can't keep up with the system, and you get more motion than you want. The hardened mounts help prevent the large motions associated with the increased engine output or harder driving (rapid acceleration, launches, etc.) - but they do that at the expense of not really moving at lower vibration levels - hence the increased NVH. If the larger deflections are going to be damaging, or hinder how the system (engine/transmission) performs, then the hardened bushings are a good investment. For normal driving, they'll make things feel more mechanical (which many folks like - by removing the mechanical isolation of the OEM mounts, you "feel" what the car is doing a bit more readily) but don't buy you anything from a performance point of view in those situations.

 

to demonstrate the engine motions - watch what the engine does when someone depresses the gas pedal quickly to get to a certain rpm, vs. when you do it gradually (a whole lot easier to show this in a drive by cable car than a drive by wire car like ours, though) - if you can repeat that on a car with hardened bushings (find someone with a WRX that has installed the grp-n engine mounts in it) you'll see that the motion is much less.

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