Engine mounts - OEM vs aftermarket semi solid

[CB911C4S]

I read with interest the thread in the 996 forum
http://911uk.com/viewtopic.php?t=146610&highlight=engine+mounts
and the one on Rennlist
https://rennlist.com/forums/997-forum/1262434-jake-raby-on-semi-solid-engine-mounts-3.html

In summary, a stiffer engine mount makes the engine knock sensors believe that the engine is detonating and retards the timing, causing a drop in power.

Jake Raby is convinced and recommends standard Porsche engine mounts as a result.

There will always be differences of opinion, any thoughts or experiences to share?

 

[jonno_]

Even if knock sensors retard ignition as a result, there are a bunch of other, more subjective, enhancements with updated mounts.

I suppose someone with more time / inclination than I could run back to back tests of new OEM vs aftermarket mounts and capture live knock sensor data...but it really is so much better for weight control and gear change.

 

[MaxA]

I understood that solid mounts can interfere with knock sensors, but I have fitted RSS semi solids, and I am not convinced there is any issue. I understand that the race engine ECUs are mapped appropriately but I don't run a Cup car.

When we have compared peak speeds at the track, I am hitting the same peak numbers as other 9972 3.8s (ie 185kmh at the end of the short main straight at Alastaro) and we can't all have the exact same engine mounts...

I suspect that this is just one more thing on the internet to worry about.

 

[CB911C4S]

Even if knock sensors retard ignition as a result, there are a bunch of other, more subjective, enhancements with updated mounts.

I suppose someone with more time / inclination than I could run back to back tests of new OEM vs aftermarket mounts and capture live knock sensor data...but it really is so much better for weight control and gear change.

Jake Raby's test was exactly that re B2B tests. However those who have used aftermarket like RSS speak about the improved weight control and gear shift.

As MaxA said "just one more thing on the internet to worry about."

 

[jonno_]

I understood that solid mounts can interfere with knock sensors, but I have fitted RSS semi solids, and I am not convinced there is any issue. I understand that the race engine ECUs are mapped appropriately but I don't run a Cup car.

When we have compared peak speeds at the track, I am hitting the same peak numbers as other 9972 3.8s (ie 185kmh at the end of the short main straight at Alastaro) and we can't all have the exact same engine mounts...

I suspect that this is just one more thing on the internet to worry about.

Max - agree with your arse-dyno.
Have recently upgraded very saggy OEM > RSS Tarmac series and loving them. Not convinced that they have increased knock-detection at all. Weight transfer much tighter and gear change very slick.

:thumb:

 

[CarreraMonkey]

I think knock sensor issues are common on lots of engines when solid (metal on metal) mounts are used.

I doubt porsche would have fitted RS mounts to their cars if they were causing knock sensor issues. Most semi-solids are only comparable to those anyway, right?

 

[MaxA]

I understood that solid mounts can interfere with knock sensors, but I have fitted RSS semi solids, and I am not convinced there is any issue. I understand that the race engine ECUs are mapped appropriately but I don't run a Cup car.

When we have compared peak speeds at the track, I am hitting the same peak numbers as other 9972 3.8s (ie 185kmh at the end of the short main straight at Alastaro) and we can't all have the exact same engine mounts...

I suspect that this is just one more thing on the internet to worry about.

Max - agree with your arse-dyno.
Have recently upgraded very saggy OEM > RSS Tarmac series and loving them. Not convinced that they have increased knock-detection at all. Weight transfer much tighter and gear change very slick.

:thumb:

Hey I was driving to avoid the arse-dyno effect by looking at overlays from the same track but they're not empirical either, different cars, different drivers, different days...

But in short, however my RSS are staying put.

 

[jonno_]

Mine too

 

[Robertb]

I think knock sensor issues are common on lots of engines when solid (metal on metal) mounts are used.

I doubt porsche would have fitted RS mounts to their cars if they were causing knock sensor issues. Most semi-solids are only comparable to those anyway, right?

RSS even say on their own literature and descriptions that they do not cause knock sensor/CEL issues. I'd imagine the Americans would be all over that with lawsuits etc if they did cause problems.

 

[CarreraMonkey]

I think knock sensor issues are common on lots of engines when solid (metal on metal) mounts are used.

I doubt porsche would have fitted RS mounts to their cars if they were causing knock sensor issues. Most semi-solids are only comparable to those anyway, right?

RSS even say on their own literature and descriptions that they do not cause knock sensor/CEL issues. I'd imagine the Americans would be all over that with lawsuits etc if they did cause problems.

Quite. I've had them fitted for years and wont be removing them anytime soon, anyway.