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Undertray question

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My vRS is lowered by a fair old way, makes for a fantastic stance but it does scrape the plastic cover occasionally. I can't find any details of sump guards which will fit with a Forge FMIC installed (else I'd be looking into buying TrevorB33's :(), but I've read that there's actually a little bit of clearance between the existing plastic tray and the sump. What I'm wondering is whether I could somehow reinforce the OEM plastic tray with some thin metal on top of it, using this space. It wouldn't be quite as good as a nice, thick, purpose-built metal guard but it would still offer more protection for the sump than just having the plastic which could just end up punctured if you hit the wrong kind of obstacle.

If I could somehow get a sheet of metal which almost exactly followed the contours of the OEM tray but didn't obstruct the standard mounting points (maybe drill some extra holes through the plastic for the metal to bolt through so it all comes off in one piece), does that sound like something which could work? I'd be a bit worried about the weight of it as the standard tray fasteners are a bit naff, but I'm sure it could be reinforced with liberal use of cable ties, that's already how my plastic tray is held on in various places...

This may be a total non-starter, it's just something that occurred to me while I was looking around for sump guards, and there's a small chance of picking up some metal offcuts from work which might be big enough to do the job if I fancied it.

Even a custom tray in metal will need bracing, without it, the sump guard would simply bend and contact the sump anyway. The sumps pretty fragile to save on weight.

Now to state the obvious, raise the car slightly. It may look nice the way you have it lowered, but is it nice enough to risk engine damage?

  • Author

Yeah, that's what I think I'll have to do. It's just a shame, I bought it that low (they must not have speed bumps or bad roads in Manchester where it came from) so it was part of the appeal of it, not realising that it was going to be a problem until I'd got home and been running around in it for a few weeks.

I realise that unless there's a good thickness of metal it won't absorb all the impact, but I was working on the fact that it's likely to be quite a "sharp" object to be able to put a hole in a sump (i.e. lots of pressure going through the plastic tray and directly into the sump) whereas if there was something a bit more substantial behind the plastic, it was more likely to at least make the pressure less due to having to punch through that, even if the force was the same.

The problem with bracing, is you effectively remove some of the sump guard to sump clearance, if you brace any area of the guard that sits directly below the sump.

If you could see how the sump drain plug thread can get worn by only slight over torquing of the drain plug, you would notice these sumps are like chocolate.

You could raise it, and go a tyre profile up to fill the arch, but check with insurance first. Better still, air suspension :rofl:

  • Author

Different tyre profiles would throw the speedo out though (can't remember whether bigger profile would make it overread more or underread more, but either way it makes it less accurate than it already is!). And yeah, not heard good things about the sump quality, maybe I'd be better off looking at one of the steel shallow sumps, I assume they're a bit beefier than the stock item as well as offering more ground clearance?

As long as the steel sump has the same capacity, and enough clearance for the oil pickup head. I don't see how they maintain the oil capacity and make it shallower, unless they make it wider. The car would get enough oil will a shallow sump, but oil temps would go up if there is less oil in the sump (thermal dynamics 101). So you might need an additional oil cooler.

  • Author

I'm assuming the capacity is fine as the ones I were looking at are VW OEM parts, not aftermarket, which would also take care of the oil temp issue. Of course it's possible that if VW fit them themselves then their technical documentation advises of a different oil capacity, but it's not been mentioned in any of the forum threads I found this afternoon or on vendors' websites. Apparently there's also a revised oil pickup for use with these sumps as well, which should take care of that. However I did find a side-by-side pic, and there doesn't seem to be much difference in the actual depth, just that the part-steel sump is shaped differently and the bottom is made of steel and is therefore stronger.

If it's OEM I would say go for it if you really must keep the slammed look :thumbup:

  • Author

Haven't decided yet. Still haven't had a free weekend to get together with someone and put my rear adjusters back in (after having it about 8 weeks) so the longer I leave it, the more I find myself making excuses to keep it slammed. But then again it's probably a bit silly to do that knowing that some of the roads around here are in such a poor state I risk hitting the sump even if I do hardly ever drive on them :)

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