Boost and Bushings

[jeepmor]

I've searched a bit and don't see many threads about boosted cars and bushing changes that follow. I'm specifically posting in here for FI owner feedback.

For reference, car is 14 FRS, HKS SC kit with their gas tune, Whiteline trans bushing, and Perrin shift bushing. South Bend 350 ftlb clutch, CSG MXP cat back and a uber hp adder Perrin air filter.

In my case, I'm getting wheel hop occasionally on launch. Especially in this three digit weather and driving for a while. I plan on adding some Whiteline bushings to the rear assembly. Unless there's something else to consider and STI makes it all in a stiffer durometer than stock. I see solid fit kits and urethane bushings. I'll go urethane as this car is still a commuter.

I also see Whiteline has kits to change about every bushing in the suspension assembly, but that's racecar level changes, so I'd have to do the front too. Not averse to it, just a lot more than fixing some wheel hop.

Don't mean to make this a Whiteline bushing thread, just appears they cover this car in that respect way better than others.

[TurboBRZ_UAE]

Rear subframe mounts + diff mounts should go most of the way to eliminating your issue. Can't speak to whiteline Vs others, but they do seem to have the most extensive catalogue

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[Grady]

Had to do rear subframe/diff bushing and engine mounts along with the others to eliminate all driveline hop.

[B T]

No wheel hop here with Whiteline diff insert and Racecomp coilovers.

[DarkPira7e]

Having tires with a little sidewall height will help as well. 235/35 tires are more likely to skip than a 235/50.
There's a tradeoff there, but every modification is a compromise on some level.

[jeepmor]

Originally Posted by Grady

Had to do rear subframe/diff bushing and engine mounts along with the others to eliminate all driveline hop.

Which brand engine mounts if I may? STI, Cusco and are there others?

By your reference diff/subframe/mounts. What were the others? Are you into the control arm bushings as well. Don't mind doing the work, just trying to get the biggest offenders first and see Whiteline has a pretty extensive bush kit for front and rear of these cars.

Also, where did you end up on NVH, mild or wild in the end?

I can definitely feel more deflection of everything with the added SC power. I'm starting with Whiteline KDT922, KDT923 and KDT925 bushings in the rear since my wheel hop on launch is stemming from that area.

[Grady]

Originally Posted by jeepmor

Which brand engine mounts if I may? STI, Cusco and are there others?

By your reference diff/subframe/mounts. What were the others? Are you into the control arm bushings as well. Don't mind doing the work, just trying to get the biggest offenders first and see Whiteline has a pretty extensive bush kit for front and rear of these cars.

Also, where did you end up on NVH, mild or wild in the end?

I can definitely feel more deflection of everything with the added SC power. I'm starting with Whiteline KDT922, KDT923 and KDT925 bushings in the rear since my wheel hop on launch is stemming from that area.

With the transmission mounts you will see almost no change. I did Whiteline subframe and diff inserts. This will bring dif noise into the cabin on deceleration. I did torque solutions mounts to keep the engine from flexing due to the turbo. It does increase NVH but does not bother me. I drive this car for what it is and have done 600+ mile road trips. I just turn the stereo up louder.

[jeepmor]

Originally Posted by Grady

It does increase NVH but does not bother me. I drive this car for what it is and have done 600+ mile road trips. I just turn the stereo up louder.

My deflection is excessive, I'll take the tradeoff. Thanks for the input that it's not too obnoxious.

[jeepmor]

I added a 3 Whiteline bags'o bushings to the rear and Torque Solutions motor mounts.

NVH is the motor mounts for sure. Hella noisy in first and reverse moving slow, fine after that. But you definitely hear and feel it more while driving. Keep the radio off and cabin engine noise is up. These cars aren't quiet anyway. With these motor mounts and the previously installed Whiteline trans connection insert, much better for driving feel hard throttle to hard braking and vice versa.

The rear end Whiteline kits are impressive. The complete bushing change on the diff itself didn't add near the NVH expected. Hysteresis feel when laying into the power and suddenly out is much better. not entirely happy though. The rear kit that bolts to the diff, still chatters occasionally on some launches. At least it's the easiest one to change should I decide to go to the dedicated kit instead of the add on kit.

Overall, car feels much better when getting sprited, it did cost me some cabin noise, and I think that's nearly all from the engine mounts.

[jeepmor]

Now living with this setup months later, still happy with it. Only get the chatter on the slow stuttering start stop moves. Still happy with the performance, but am continuing to think STI N motor mounts may be in my long term future. I've talked myself in and out of it couple times now.

[Decep]

Originally Posted by Grady

With the transmission mounts you will see almost no change. I did Whiteline subframe and diff inserts. This will bring dif noise into the cabin on deceleration. I did torque solutions mounts to keep the engine from flexing due to the turbo. It does increase NVH but does not bother me. I drive this car for what it is and have done 600+ mile road trips. I just turn the stereo up louder.

I know this was posted months ago but i noticed quite a bit of change with the transmission mounts and rear shifter mount. I find it easier to downshift and also i get less fore and aft jerky movement when pissing around in stop and go traffic.

[WC-BRZ]

Originally Posted by Decep

I know this was posted months ago but i noticed quite a bit of change with the transmission mounts and rear shifter mount. I find it easier to downshift and also i get less fore and aft jerky movement when pissing around in stop and go traffic.

You really should not be taking a piss inside the car - stop and go traffic or not

[Steve Bodalenko]

Originally Posted by jeepmor

Which brand engine mounts if I may? STI, Cusco and are there others?

i fitted the STI mounts and no noticeable difference in NVH but improvement n power to the ground was very noticeable. Also running the Whiteline trans bushes and subframe/diff inserts minus the the diff front ones. Just found it was just to mechanical and race car noisy to enjoy. Nowhere near the NVH with just the rears in and delivers plenty of stiffness to drive train.

Consider the MCA traction mod. Pretty sure there’s a US equivalent now. Well worth the effort and cost.

I’m also running the Verus CF driveshaft but that’s next level in cost and no longer available, I think.

[jeepmor]

Originally Posted by Steve Bodalenko

i fitted the STI mounts and no noticeable difference in NVH but improvement n power to the ground was very noticeable. Also running the Whiteline trans bushes and subframe/diff inserts minus the the diff front ones. Just found it was just to mechanical and race car noisy to enjoy. Nowhere near the NVH with just the rears in and delivers plenty of stiffness to drive train.

Consider the MCA traction mod. Pretty sure there’s a US equivalent now. Well worth the effort and cost.

I’m also running the Verus CF driveshaft but that’s next level in cost and no longer available, I think.

I'm close to your setup minus the driveshaft, plus the front diff bushings and the MCA brackets. The Torque Solution mounts are my issue. I'll finally going to pull the trigger and get some N-group ordered soon. I've been on and off the fence several times, but the NVH from the Torque Solutions is just too much for me for a commuter. Really like them otherwise, the in/out of throttle feel is astounding now. But watching the rearview mirror rattle at a stoplight and finding several resonances in the cab at parking lot speed, it's just too much. Great product, but more racecar than daily for me is all.


Pivoting to the rear end, I still have occasional wheel hop issues when I have the feather the clutch a lot, any comments on STI bushings in the rear end. It's all in the diff bushings that mount to the end of the diff. I've seen STI units for these, curious if anyone has tried them. I have the Whiteline kit in now, helps a lot, but still doesn't address that low speed suspension windup. I blame this on the 350ftlb stage two clutch, just need to find the right rubber to keep it in check, hopefully not with more glaring NVH like the Torque Solution motor mounts.