In an ongoing quest to improve my C4, I decided to try the RS engine mounts. I didn't expect a lot from the change: more noise of course, but hopefully a more controlled and secure feel from the rear of the car. My expectations of limited effects were completely wrong - the RS mounts make a BIG difference to the car.

To begin with, the car feels SO much more solid. The feeling of undamped masses moving around on corner entry/exit is completely removed. I had been steadily stiffening the rear dampers to try and control this effect, but it turns out most of the movement I was feeling was from the engine on its mounts! Once the RS mounts went on, it was immediately obvious that the rear dampers were harder than they needed to be - I backed them off to be the same as the fronts (6), but the rear of the car is so much better controlled than it was. I would not have believed how much influence the engine mounts could have on the overall damping of the rear of the car. The car also reacts more positively to steering input, it feels really 'together'.

The next improvement took me by surprise, though in hindsight it makes sense. Many will have noticed that progress can be less than smooth in a 993 in stop/go traffic and under throttle on/throttle off conditions. I had always assumed this was hamfisted tuning of the ECU's overrun fuel cutoff/reinstatement functions combined with a bit of driveline shunt from the 4WD system. Well, with the RS mounts this behaviour is completely eliminated, the car is now smoothness itself in conditions where you really had to be so careful with clutch and throttle to make smooth progress before. It is well worth fitting the RS mounts for this alone, it makes such a difference in everyday driving.

Finally, there is a distinct increase in engine noise. Those of us who enjoy the aural accompaniment of the flat 6 will be pleased to note this additional benefit comes at no extra cost All adds to the thrill of driving the car.

The car was really so good already (with PSS-9, RS bars, monoballs etc) I hadn't expected much from this latest mod, but I'm delighted to say I was wrong. I can't believe how the car just keeps getting better and better. Now I'm counting the days until next Saturday's track session. <img border="0" alt="[burnout]" title="" src="graemlins/burnout.gif" />

 

Thanks for the post, John. I know it's hard to quantify here but how much louder is the engine, how did vibration and resonance increase and what aural characteristics have changed?

 

John, can you post the part numbers for the RS mounts?

-Steve

 

John M,
It sounds like you are really happy with your most recent modification.

Did you do the work yourself, or have a shop perform it? How complicated would you say this procedure was, and how much did the mounts cost?

Cheers,

 

Here is a photo of the parts. Ignore the upper part which is an RS transmission mount. The lower parts are the engine mount pieces. The order of parts from left to right in photo (top to bottom in car) is bolt-washer-seating washer-mount-seating washer-washer. The parts list is:

2X 900.082.030.02 12 X 105 Bolt
4X 999.025.074.02 Washer
4X 901.305.311.00 Seating washer
2X 964.375.311.80 Mount

Not shown are the 4X 999.025.134.02 washers to go under the bolts to the chassis.

<img src="http://boards.rennlist.com/upload/RSenginemount.jpg" alt=" - " />

 

Chuck, I had my dealer do it, their labour charge was 1 hour. There's a DIY for it on Robin's <a href="http://www.p-car.com" target="_blank">www.p-car.com</a> site, which lists the parts and their prices (which are a lot cheaper in the US than the UK <img border="0" alt="[grrrrrrr]" title="" src="graemlins/cussing.gif" /> ).

Mark, I haven't noticed any extra vibration. It is basically the same stuff as before but louder, the noises from the engine are maybe getting on for twice as loud as they were -&gt; but bearing in mind there's not a lot of engine noise to start with, i.e. it is still not especially loud. Don't forget that an RS has these mounts, plus a stiffer transmission mount (which I couldn't get hold of -&gt; no stock in the UK or Germany), plus no rear seats plus less sound insulation and you don't hear their lucky owners complaining too much .

 

Thanks for the great thread. That's another thing to add to the list then...

What was the price of the parts in the UK?

 

I found that the transmission shifted easier under load after I switched to the RS mounts.

George

 

I can't comment on the change to RS mounts as my car had them originally.

I changed from the RS type to the factory RSR/Cup solid magnesium mounts pictured and the noise and vibration in the car increased quite a bit but the gearbox shifts like a rifle bolt and the car seems to throttle steer more precisely.

Changing the mounts is not a big deal if you have a floor jack to support the rear of engine but be careful not to drop it!

<img src="http://boards.rennlist.com/upload/RSRcupenginemounttop.jpg" alt=" - " />

 

And one could go somewhat further with the carbon fiber/titanium version!

<img src="http://boards.rennlist.com/upload/cartridgeenginemount2.jpg" alt=" - " />

<img src="http://boards.rennlist.com/upload/cartridgeenginemount3.jpg" alt=" - " />

 

Any part numbers on the carbon/titanium parts?
I imagine they're cheap, right?
Will these things withstand a turbo engine?

 

No part numbers as we made them. They will withstand a turbo.

 

Replacing the rear motor mounts may be a one (1) hour job: Replacing the transmission mount ain't so simple. The old tranny mount has to be pressed out...probably about 2 hours worth of work for this change .

I have changed out my mounts to 993RS mounts...the primary end result, I feel more confident shifting gears on the track.

As Cup Car will tell you, there are two tranny mounts available, a 993 RS mount and a RSR mount. The RSR mount seems to be nearly solid to me.

Cup Car has the solid motor mounts and the RSR tranny mount. In addition, he has the RS light weight flywheel, and a few other goodies that I will let Cup Car reveal, if he so wishes.

I had the opportunity to drive Cup Car's ride around the Qualcomm Stadium. If you love gear and motor noise, you'll love your car after you do the Cup Car mods. If you love to hear your stereo, you may have a bit of a problem with the set up .

Lastly, it seems logical to me to change all three (3) mounts at the same time. It's a system guys, just like suspension, IMHO, of course. <img border="0" alt="[thumbsup]" title="" src="graemlins/bigok.gif" />

 

I think if shifting is your game, then a change to the 993 RS short shift kit is the way to go. Not only is the shift linkage geometry arranged for a shorter shift but the universal coupling is improved as well to eliminate slop. Pictured is the kit in a photo shamelessly stolen from <a href="http://www.carnewal.com," target="_blank">www.carnewal.com,</a> a source for the kit. Also there is a close up picture of the universal joint, it is the one on the top, the one on the bottom is from a 964 RS, the standard 993 piece is even more bogus than the 964 RS part, as it has rubber in it. You can see the slop in the elongated pin hole in the original piece.

I have to admit, Martin is right, my car with a LWF, RSR solid mounts, RSR trans mount, the short shift kit with the solid universal and my Clubsport G50/32 close ratio gearbox with steel syncros on all 6 gears shifts pretty cool. It also really feels like a racing car....

<img src="http://boards.rennlist.com/upload/P1010252Small.JPG" alt=" - " />

<img src="http://boards.rennlist.com/upload/RSshortshifter.jpg" alt=" - " />

 

John M,
Thanks for the reply. On my many trips to Robin's site I never noticed the motor mount DIY. I guess it always slipped from my attention since I wasn't thinking of it as a performance enhancing mod until I read your remarks at the top of this thread.

Thanks to everyone else who added to this thread, it has been very informative. The RS motor mounts seem like an almost must have item to me. The transmission mounts may have to wait.

Cheers,