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2012 Si coupe
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Discussion Starter · #1 ·
Full disclosure - I’ve been driving Honda’s a long time, I am fully aware of the power loss and drag the a/c puts on these cars/motors…
My issue is this, the car runs completely different when the a/c is ON compared to when it’s OFF, like it’s legit night & day. It’s not just the power loss, the drivetrain acts way different too. Every single gear change I can feel it going into and out of gears, I can hear it changing gears and there’s all sorts of thumping and bumping when I engage the clutch and disengage it - it’s just not smooth no matter how hard I try to drive perfectly. When air conditioner is OFF the transitions between gears is pretty seamless and the car runs pretty smooth

Does anyone else experience this?
 

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A lot of Honda Civic drivers report strong vibrations or a rattle when they drive their vehicles or switch gears. This is often due to faulty engine mounts that are no longer providing suspension and support. Engine mounts are typically expected to last the lifetime of the vehicle. However, many Honda Civic owners have reported that their mounts need to be replaced with less than 75,000 miles on the vehicle.
 

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Truck? What truck?!
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I have also owned my 2015 five-speed since day one, and although the car is a bit slower when the AC is on there is no thumping and bumping, or, in fact, any difference at all when changing gears when the AC is on or off. In fact, none of my many MT cars have done any of that.

I would probably begin as X83 suggested and check the mounts.
 

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Full disclosure - I’ve been driving Honda’s a long time, I am fully aware of the power loss and drag the a/c puts on these cars/motors…
My issue is this, the car runs completely different when the a/c is ON compared to when it’s OFF, like it’s legit night & day. It’s not just the power loss, the drivetrain acts way different too. Every single gear change I can feel it going into and out of gears, I can hear it changing gears and there’s all sorts of thumping and bumping when I engage the clutch and disengage it - it’s just not smooth no matter how hard I try to drive perfectly. When air conditioner is OFF the transitions between gears is pretty seamless and the car runs pretty smooth

Does anyone else experience this?
bone stock?
 

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2012 Si coupe
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Discussion Starter · #6 ·
bone stock?
It has a K&N Typhoon/short ram (w heat shield 🫤) … other than that it is stock yes.
HOWEVER I am uncovering little hints here and there that let me know the car was definitely modified before and then returned to stock upon selling it I suppose. I know it had suspension and was super low before, it had super thick dark tint before, obviously has the intake still on it, almost positive it had exhaust on it etc…
 

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2012 Si coupe
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Discussion Starter · #7 ·
A lot of Honda Civic drivers report strong vibrations or a rattle when they drive their vehicles or switch gears. This is often due to faulty engine mounts that are no longer providing suspension and support. Engine mounts are typically expected to last the lifetime of the vehicle. However, many Honda Civic owners have reported that their mounts need to be replaced with less than 75,000 miles on the vehicle.
Two things:
1, it makes me feel way better to know most everyone else experiences this
2, thats a fantastic thought man!! I strongly agree with that, I really think that’s a large part of it
 

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Truck? What truck?!
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Seriously?^
 

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My Si does this too, its always been my biggest complaint with the car. When I was in college I would also just turn the AC off when shifting or driving spiritedly. The way I always thought of it was that the Si actually has a pretty lightweight flywheel that changes speed very quickly. With the AC off the rev hang keeps the revs from dropping too quick but with the extra drag on the motor with the AC on, they tend to sink like a rock. But it becomes unpredictable because you don't know if the compressor is on or off and makes shifting kind of unpredictable.
 
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