mikymu

In order to combat 2nd to 3rd gear shift sloppiness I installed WEVO semi-solid engine mounts in my RS to help minimize side to side swaying of engine+tranny mass (which accounts to 25% of the sprung weight of the car) and beefier Cup car shift cable. Despite of all these efforts I still encounter occasional difficulties getting into 3rd gear under high G load on the track. This is mostly due to operator error ... I grip the shift **** too hard which prevent shift linkage from getting into proper alignment for the 2nd to 3rd gear change.

This makes me wonder what will a solid engine mount feel like? Will it shake my teeth loose from excessive noise vibration harshness from marrying together the mass of the drivetrain and the sprung mass of the car? Cup cars have solid engine mounts ... and my mini-Cup car should have one too

So, curiosity got the best of me and here is what I found out with the Rennline solid engine mount.

Rennline solid red engine mount next to the WEVO semi-solid unit



Rennline supplied a self locking nut and a small washer which I felt is not large enough to cover the square opening at the base of the engine mount compare to the wide base factory nut





I got a larger washer and also a wide base nut from Lowes shown on the top of the picture. The washer matches the larger diameter of the factory nut





Another difference I encounter with the Rennline engine mount is that it does not contain a square base to fit into the square opening of the engine mount bracket. Here is the Rennline supplied round bolt in the square opening of the engine mount bracket and next to the factory engine mount





The diameter of the factory square base is 15.9 mm compare with 11.8 mm of the Rennline supplied bolt





Fitting an wider outer sleeve can help solve the size difference in the square opening of the engine mount bracket ... but I come to find out after you situate the Rennline engine mount it sits off line to the center opening - so it's best to not use the wider outer sleeve





OK, back to fitting of the Rennline engine mount. Some work is needed to shave the edge that come in contact with the center bolt that secure the chassis mount. The left side barely fit without modification but I have to grind away the lip of the right side Rennline engine mount to fit







Another difference I noticed between factory and Rennline engine mount is that Rennline engine mount is taller which means it will sit the drivetrain slightly lower by 1/4" toward the ground



I applied some thread lock on the nut to help secure the bolt and torque the bolt to 60 ft/lbs and two smaller upper bolts to 18 ft/lbs







What it looks like all installed



So, what does it feel like once I turn on the engine? Well, good news is that I have not call my dentist to repair fillings that fell out from all the shaking. On the contrary, the engine was baby butt smooth!? I was expecting to see alot of tremor from the rear view mirror and there was none. The engine is smooth, quiet and it actually transmit less noise to the cabin. My Cup cable used to transmit a loud mechanical noise to the cabin when it's not in gear and that noise is now gone? Driving wise it is as smooth as having the WEVO engine mount and sudden side to side movement of the car is a surgical operation. Wow, what a surprise! Less vibration and noise from a solid engine mount. I will have more feedback once I try it out on the track ...

911SLOW

placebo effect? : )

cfjan

So the new screw does not have the square base to center it around the engine side of the mount. Would that create possible side to side movement? (Probably not a big deal if it is tightened properly)

Serge944

Dibs on wevo mounts if you decide to sell

chardonet

Thank you very much for yet another well-documented DIY!!

"Another difference I noticed between factory and Rennline engine mount is that Rennline engine mount is taller which means it will sit the drivetrain slightly lower by 1/4" toward the ground"

Curious as to how above may contribute to less vibration and noise? Also, what are your impressions on the road so far?

I was surprised that the Rennline part did not fit without slight modification. Looking forward to your on-track observations! Thanks again.

996FLT6

Ne idea what cupcars use for the tranny mount? Is that solid too? Mike

Nizer

I hope you're receiving development consulting fees from the boys in Wilton.

P.J.S.

nice thread... again... thank you for documenting and posting

911SLOW

Yes.
That's what I told Mike to check his.
Got mine oem's rubbers shot in less than a year from previous check.
Maybe it plays a role in trouble changing gear under load.

mikymu

lol

I was wondering the same when I start up the engine for the first time. I am happy to report it is not a placebo effect. I was really worry when I did not feel the expected amplififed engine vibration and check the engine bay three times. Stange ... solid engine mount and less vibration?

Yes, I worry about that too that's why I got the wider out sleeve. Looks like it's holding well as long as I tighten down the bolt. I will check the torque from time to time to make sure everything is fine. The square base on both factory and WEVO engine mount still have room to move in the square engine mount opening. It is not a perfect fit. I suspect left to right movement of the engine/tranny assembly is minimal and fro/aft movement is negligible since you have the tranny mount at the end to hold it in place

Sure thing ... will let you know if I decide to keep Rennline

Yeah, I was hoping there will be no modification needed but as you can see alot of modification is needed to make it fit right. lowering the drive train slightly by 1/4" maybe a good thing since you will lower the center of gravity. SO far no sift problem driving on the street. Will give more feedback once I try it on the track

Yes, it's solid as shown below ... pretty straight forward one bolt design





lol

I hope folks at Rennline chime in to answer some of fitments issues

Any time

cfjan

Mikymu,

Do you get these products for free to test or you actually have to buy them?!

MJones

A whole lot of modifications to an off the shelf item.

Doesn't make allot of sense.

cfjan

I think the reason is because the Rennline motor mount was initially designed for a different application (964/993)..

mikymu

I bought them from Rennline website. Unfortunately most aftermarket products need some sort of modification. I think Rennline can make some adjustment to make it fit better on 6 and 7 GT3

FFaust

Thank you

Concerning the Rennline mount being 1/4" taller: This might have to do with solid v. elastomer. The solid mount will NOT allow the engine to droop, whereas the elastomer mount might allow some slight drooping once loaded with the weight of the engine. If you had measured actual engine position before and after, you might have found the postition of the engine to be the same. The soft mount might allow the engine to droop down to the same lowered position as with the solid mount.

Not sure if this is what you meant above but, the square base v. staight bolt would allow for manufacturing tolerances. I am sure that even Porsche can not produce engine bays with tolerances within thousanths (then again, who knows?). So, because the solid mounts do not allow for any side to side movement, using a round bolt allows for the engine and mounts to be positioned properly and to "fit".