this is from PMO's ad in the october '03 panorama.

I was thinking about solid motormounts for my racecar but this article makes you think. Maybe the 911 clubsport mounts are better.

dave

well - ya gotta consider his perspective - he doesn't like them because they may increase vibration on the engine and make his carburetors run bad due to sloshing and vibration.

been a while since a serious 911 race car ran carburetors ...
i don't even have caarburetors on my street 911 - and i just installed solid mounts this weekend.

i'm doing solid engine, clubsport transmission - in my 914.6, i plan to do it the other way 'round. (solid-mount the most-aft thing, compliant mounts up close.)

i'm glad he likes the WEVO approach to improved shifting - still not quite there as an option for midengine 901 transmissions AFAIK...

i'm with him. fix your shifting problems where they occur and leave the old mounts in (make sure they're not broken) or get the sport mounts. they are there for a reason. if you car shifts bad, it's NOT because you have rubber tranny mounts ...


Andy

He doesn't state that they're for HIS carbs, just carbs in general. And he also points out that FI gets its fair share of beating.

In the import street scene I see kids installing solid mounts...stupid!

i've got stock mounts front, solid rear (trans).

It's unclear to me that Parr has actual data to support the contention that solid mounts harm horsepower, put a significant strain on the sheetmetal and engine, destabilize the carbs, or caused the Romans to eat lead. He just has some musings and a a single anecdote about this guy who gets a lot of power out of his car and airplaine engines. There's no evidence that the motor mounts had anything to do with this horsepower gain.

Conversely neither do I have any actual data that solid motor mounts don't degrade horsepower, or damage sheet metal, or cause "harmonic" disturbances, or fuck with your circadian rhythms. But my guess is: probably not. I don't think the solid mounts do any significant damage to the structure of the car and I really doubt it has any measurable effect on horsepower.

That said, I don't like solid mounts for street driving. They connect the engine to the body directly so all the engine vibration gets translated directly to the body. The body turns into a big speaker and helps to amplify engine noise (that should have been suppressed through isolating the engine vibrations at the motor mount level). This is partially why new cars are so quiet. On top of having counterballance rods that rotate in the opposite direction from the cam and crankshaft, canncelling out vibration, they also have liquid filled motor mounts that isolate engine vibration, and thus sound, from the passenger compartment.

The second major problem with solid mounts is that I've found that if you have a lot of power under the hood, say around 200 hp or so, is that the engine's own twisting force (under rapid acceleration or rapid deceleration) will press the suspesion down on one side or another of the car (depending on whether the engine is suddenly winding up or suddenly winding down) and this will destabilize the rear of the car. Essentially the car gets squirly at the rear end because the engine rocks hard to the right or hard to the left. Normally this sort of engine twist is cushioned by the soft motor mounts but with solid mounts all the force gets directly translated to the chasis, and thus directly translated to the rear suspension. This can be dangerous.

So for me, the sport mounts are the better choice, and not for the reasons Parr has given but for the reasons I discussed above.

Douglas

99.9% of PMO's business is the sale and support of carburetors. this does not make for an objective observer. yes, he -says- EFI components take a beating. i'm certainly not going to fund the shaker-table environmental testing program to prove anything one way or the other.

i agree they're not a pill-cure for shifting problems, nor do i ever think i said so. my car shifts fine, and actually the rubber OEM mounts i took out appeared to be in pretty good shape - as did the transmission mounts i looked at (that aren't compatible with clubsport -or- solid mounts ...) some of the mounts i've seen look pretty cheesy - i've got Tarrett mounts via Paragon. i have 0 miles on them. if i don't like 'em, i'll put the ClubSports in...

I agree with Andy.

Take this comment for the secondhand gossip it is, but I have "heard" of top-end performance and drivability issues with the PMO's in race applications. I betcha those full-blown race cars were running solid mounts too, and that was used as the explanation for the problems.

Now, I don't see many race cars with PMO's and would venture a guess that Richard's main market is Zenith/Weber/MFI/CIS replacement for street cars.

Right now I have the club-sport engine mounts and Weltmeister (semi)solid trans mounts on my 914 (w/ Webers), and have been thinking about solid mounts on both ends. I know of no legit reason right now not to do so. It's a track car - I agree that solid mounts are craziness on pure street cars.

what benefit do solid engine and tranny mounts add to a pure race car?

Andy

I've read that ad many times. Normally I wind up laughing...

i can tell you based on my 20-mi roundtrip to work and back that i experience an immediate feedback to throttle application that i never experienced before. the engine is definitely much more responsive in applying power since it doesn't have to wind up and preload the rubber.

i don't feel much if any increase in noise or vibration but it was pretty load before. actually - there is an unpleasant vibration north of 5000 that seems more pronounced - but i also know for a fact my timing isn't spot on yet so it's too early to say it's objectionable.

now that sounds like something you would want, especially in a race car ...

Andy

Seems to me that the avenue of experimentation would be with higher durometer rubber compounds, or maybe delrin. Stiffer, but still allowing some compliance.
Patrick Pickerell

factory 911 sport mounts have a harder duro. rubber insert....AKAIK, they work with the 914's, at least for the rear transmission mounts....I think tailshift cars can use the 911 mounts for the engine

In our region, we cannot have solid engine mounts for most of the classes, but there is nothing that states we "cannot" have solid transmission mounts

I think one reason he condemns solid mounts is that they play havoc with the PMO carbs. A friend of mine replaced his perfectly good Webers with the allegedly superior PMO carb. He has had nothing but problems with the PMO's, and PMO claims his solids mounts are the culprits.

The Webers have been reinstalled, the PMO's are for sale, and the solid mounts are still in place.

The float assemblies in the PMO's look suspect, there is a teeny lil spring thats supposed to control things, and we think they just cant stand up to the vibrations from the solid mounts.



all that is a good thing.

The statement posted with the adds seems like a cyoa sort of thing. These new improved Webers are starting to show some flaws..

BTW I have solid mounts in my 911 w/Webers, have had them for about 5 years now

I never thought of it till I read the article but that may be the reason my carbs are consistently out of tune.

I only run the solid trans mounts

my solid mounts have been in for a week now and here is my impression (rears only).

There is a 'bit' more noise than the stock mounts, but in our cars its only noticeable during deceleration and it's not annoying. I kind of like the sound myself.

Front mounts? I dunno about.

Tim...interesting...that exactly echoes the story I was alluding to here in SoCal. 914-6 3.2 race car that had PMO's. They couldn't get it to run right, even with significant pro dyno tuning, so it was converted back to Webers. Makes you go...hmmmm....

Andy - I think on the 914 the trans mounts make the biggest difference in keeping things "in place" when shifting and under accel/decel forces; I am not really sure how much benefit the front mounts add to that. The main place the added stiffness can be felt IMHO is when downshifting under decel and especially also under g-loads; like those turns where you are going uphill, downshifting, and turning sharply all at the same time. With squishy mounts the gear you are looking for tends to "move" from its normal position on the shift linkage. I guess the trans is actually moving a slight amount on its mounts, which is exaggerated by the looong 914 shift linkage.

Ah, didn't realize they sold carbs.

I have stiffer (but not solid) engine mounts in my Jetta and it did make a difference in shifting. It also added a LOT of cabin noise! That was NOT going to do in my daily driver so I modified one of the mounts to slightly soften it -- worked better than I expected (yeay). I do understand the function of mounts and why stiffer ones are desireable for those of us in the performance mind set...but still, for street driven cars solid mounts are

I'm in a bit of a quandry. My 914/6 trans mounts work just fine, thanks, but I've got a set of solid mounts that I need to try out. Come spring, they'll be in there for a test.

Reading all this stuff reminds me to keep an open mind.....even if sumthin' falls out.

I've got them old Weebers and not them fancy-schmancy PMO thingys so's I ought to be OK.

i ran all hard polyurethane mounts and bushings in my SOLO-II ur-GTI so i can relate - but - a 914 is not a water-VW ...