Anyone running a PMS sump guard? - Increased vibration?

[frayz]

All,

Guessing this will mostly be the rally/race guys and chances are you wouldnt be able to tell anyway due to the nature of your vehicles use.
But ive just fitted a PMS sumpguard to my road car, its not fauling the engine or transmission, yet ive a significant increase in cabin vibration, similar to the first time you fit Vibratechnics engine mounts. Ive noticied a huge increase in subframe stiffness and am assuming this is attributing to the increase in NVH.

Anyone else have one and report your findings please?

Thanks

 

[Robbie Corbett]

Must be because of that missing bolt Frayz, car looks mega as always

 

[frayz]

Must be because of that missing bolt Frayz, car looks mega as always

Bloody bolt nipped up in the RivNut Rob. Then spun the insert as i tried to undo it. Grrrrrr. I'll live without it, as the other 6 million bolts should cope!

 

[Robbie Corbett]

Bloody bolt nipped up in the RivNut Rob. Then spun the insert as i tried to undo it. Grrrrrr. I'll live without it, as the other 6 million bolts should cope!

Hate it when that happens! Once they spin your doomed. Anyway hope someone who actually has an answer for you joins in

 

[Sash]

Bloody bolt nipped up in the RivNut Rob. Then spun the insert as i tried to undo it. Grrrrrr. I'll live without it, as the other 6 million bolts should cope!

Should have used one of those shiny hand tools you’ve got, might have caught it before that happened 😉

 

[frayz]

Should have used one of those shiny hand tools you’ve got, might have caught it before that happened 😉

Oi, you leave my tool collection out of this.

 

[massiveCoRbyn]

Rivnuts are a bit of an odd choice for this application in my view. Fine for your use, but I think I would want something a bit more substantial on a rally car, as the sump guard is going to be on and off a lot, and it is so easy to damage them.

Anyway, that's nothing to do with this I suspect that you're right in that you have added some stiffness to the subframe and its caused some additional vibration somewhere else, or changed the frequency of something. Does it do it at any particular times/speeds/loads?

 

[frayz]

Rivnuts are a bit of an odd choice for this application in my view. Fine for your use, but I think I would want something a bit more substantial on a rally car, as the sump guard is going to be on and off a lot, and it is so easy to damage them.

Anyway, that's nothing to do with this I suspect that you're right in that you have added some stiffness to the subframe and its caused some additional vibration somewhere else, or changed the frequency of something. Does it do it at any particular times/speeds/loads?

Most severe on idle, pulling away at low rpm and oddly increases with low speed steering lock, but i think thats the PAS putting load on the motor to be honest.
It feels like ive just put a very very stiff set of engine mounts on. Im gonna have it off again tonight and tripple check for fouling, but im 99.9% certain its not making physical contact with anything.
Spoken to Nick @Pms too just to see if anyone else was daft enough to fit one to a road car? Of course not lol

I agree, if this were a competition car, id be welding in threaded boses and using hardware with dogpointed ends. For my use, this is adequate and i'll start and finish them all by hand and use a small 3/8 gun to wind in and out.

 

[massiveCoRbyn]

It does sound similar to the engine mount vibration. How stiff is the guard? If you were getting contact between it and the engine/gearbox, I wondered if you might hear it more but, if it's pretty stiff, you may not I suppose.

Yeah I would 100% use threaded bosses if it was on a rally car. Given that it's aimed at those sort of users, I'm surprised they didn't go down that route really. Makes it easier for you I suppose though!

 

[Louis]

I mean you've just put a massive bit of metal underneath so you'll get some weird resonants. Might find the PMS shifter has some new frequencies.

 

[bozothenutter]

Yup, and yup..

Mine was juuuuust touching the bottom of the box......souden like it was about to explode!
Stiffness is incredible though, even when already running the PMS strutbrace!

 

[frayz]

Had it off again tonight as I had a pair of Ktec/Vibratechnics mounts to fit anyway.
Found no witness marks at all on the underside of the sump guard but I did find of the bolts that hold the linkage protection plate was polished on the top. It was just touching the large M12 bolt head that mounts the dogbone to the engine.
Oddly those fasteners which hold the linkage protection plate are just nut/bolts which means they protrude quite a lot from the back of the sump guard.

I’m thinking either some half nuts and shorter hardware or adding Helicoils to the guard and doing away with the nuts completely.

Even with the new VT mounts I’ve no more sump guard resonance, but I’ll know better when I drive to work tomorrow. It’s nice knowing the underside has at least some protection now.

 

[frayz]

I mean you've just put a massive bit of metal underneath so you'll get some weird resonants. Might find the PMS shifter has some new frequencies.

I know the difference between something that’s right and wrong though chap, and there was deffo something not quite right.
🙂

 

[bozothenutter]

I have now put some rings between the plate and the subframe, plate is now level with the two triangles, and no more touching the box.

 

[Robbie Corbett]

How did you get on with this frayz?

When you say you have noticed a huge increase in subframe stiffness what do you mean, is this from a driving perspective ie, its positively changed?

 

[frayz]

How did you get on with this frayz?

When you say you have noticed a huge increase in subframe stiffness what do you mean, is this from a driving perspective ie, its positively changed?

I found that the transmission was kissing some of the bolt heads that holds the gear selector rod protection piece. I removed one or 2 pieces of hardware in those locations. It has massively reduced the NVH but its still kissing somewhere at full load WOT that i need to investigate. Even with VT engine mounts controlling the torque reaction of the motor, it still manages to touch somewhere.

As for stiffness, you can feel the whole subframe has less flex in it, so much so that it did induce some on power understeer and ive backed the dampers off a click to compensate. The steering feels more imediate and front end feels more darty and keen to change direction.

Significantly more noticable than when i fitted my PMS strut brace.

 

[Robbie Corbett]

Awesome, nice result. It makes sense too as the plate is reinforcing the lower wishbone areas significantly, was curious if you noticed it when driving and I think your answer is a clear yes! Similar to an E46 M3 which also ties into the rear lolly pop bushes where a regular E46 doesn't. Wonder if you could get similar results with an X brace between legs and not have clearance issues like an E36 M3 does:

 

[Daz...]

That sounds like it's reduced the flex between the lower arms, much like it did on my MK2 Golf when I fitted a front "lower strut" brace as it was called. That bolted directly where the arms are attached though.

Made a massive difference to turn in.

 

[frayz]

See no reason why not. Its deffinitely noticable Rob.

 

[JamesBryan]

I think a stitch/seam welded subframe would provide a bit more strength too.

Probably something i'd look at if i had the subframe off.

 

[frayz]

I think a stitch/seam welded subframe would provide a bit more strength too.

Probably something i'd look at if i had the subframe off.

I'd say so James. This is only a 5mm hard alloy plate but the difference with it than without it is markedly noticable.

 

[Robbie Corbett]

I think a stitch/seam welded subframe would provide a bit more strength too.

Probably something i'd look at if i had the subframe off.

I watched an interesting video some time ago where a whole shell was stitch/seam welded, the torsional rigidity was tested before and after and was actually slightly reduced, they thought because the welds had annealed the metal around seams. The best way to increase stiffness is to add more stiffness (haha). I think if you could somehow tie the plate into the wishbone mounts it would be even better.

 

[RustyMojo]

So would you say, excluding the current challenges it’s a worthy upgrade @frayz ? My car is missing the undertray, so maybe a good opportunity to push the buy button!

 

[frayz]

So would you say, excluding the current challenges it’s a worthy upgrade @frayz ? My car is missing the undertray, so maybe a good opportunity to push the buy button!

Tough one really mate, as new they're quite spendy and i didnt buy it new.
If you can pick up a used one and make sure you get it fitting with no fouling then absolutely. Significantly improved front end feel and the obvious protection under the car when pressing on. I haven't caught it yet that i have felt or heard, but it does offer quite a bit of peace of mind knowing the oil pan and gearbox are protected when the car is occasionally asked to land or tackle a particularly bumpy section of road. All id say is spend the time making sure you get it fitting right and be prepared to space it further or dress any protruding hardware that may foul it under load.

 

[Krarl]

Is it just a piece of bent plate with a cutout and a dog kennel for the shifter rod?

Or has it been swaged for stiffness?

 

[frayz]

Is it just a piece of bent plate with a cutout and a dog kennel for the shifter rod?

Or has it been swaged for stiffness?

Nope thats pretty much it. But the subframe isnt that massive and the sump guard is incredibly rigid as it is. I dont think it needs any swaging personally as its hard alloy and not the usual soft sheet stuff.

 

[Krarl]

Yeah just read its a 5mm thick sheet. Did you have to drill and rivnut the subframe then?

 

[frayz]

Yeah just read its a 5mm thick sheet. Did you have to drill and rivnut the subframe then?

Yup, 11mm drill and big b*****d RivNut installer. I used a Cobalt bit but i could have used an 11mm sausage thus is the thickness and integrity of the stock subframe.

 

[Usr117063]

@frayz If you feel the car more darty with the sump guard your mind will be blown when you replace the weak links in the steering!

 

[frayz]

@frayz If you feel the car more darty with the sump guard your mind will be blown when you replace the weak links in the steering!

Honestly dont feel the steering has much play in it to be honest. If a solid UJ comes up i'll change it, but im not that fussed at the mo.