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How to retro-fit the front subframe cover from the VW Tiguan (2016->)

golfdave

Drag Racing Champion
Location
Scotland (U.K.)
Car(s)
MK7 Golf GT Estate
Part 1 of 4

WARNING:- this modification might be superseded by whatever undertrays VW fits to the MK8 Golf. However, the MK8 Golf has the Audi aluminium front subframe which does not lend itself to this modification. I strongly suspect that the MK8 will have a one-piece tray from the front bumper to the rear of the front subframe like the current 2019-> VW Polo.

EDIT Feb 2020:- I have photos of the underside of a Mk8 Golf & it does NOT have a cover, or a longer skid tray. The exposed front subframe looks like our Mk7/Mk7.5 one, & has no more mounting points etc.!

Vehicle used in this guide

UK spec, 2014yr model, Mk7 Golf Estate (GSW), GT (Highline) trim, 1.4lt TSI (140PS) CHPA petrol engine, MQ250 6speed manual gearbox, multi-link rear suspension.

Vehicles that this guide is applicable to
Any VAG cars with the MQB pressed steel front subframe.

Introduction
As you may know I have a “thing” for fitting aerodynamic undertrays to my car to make it as streamline as possible, & also to provide maximum protection to the car from grit/salt/snow/mud etc., that comes off the roads that I drive. One area which has annoyed me is the front subframe, which has loads of large holes in it which also expose the electric motor & cables for the power steering rack.
Earlier this year whilst doing some “Google-fu” I found a photo of the current (2016 ->) VW Tiguan which had been involved in a crash & was on its roof. I noticed that the whole underside was very well covered in plastic undertrays, including the front subframe!

Research
I have never seen anything like this tray in the MK7 Golf ETKA parts diagrams, or on the previous Tiguan or any other VAG cars. The nearest is the one piece metal (aluminium) skid tray which goes from the front bumper to the rear of the front subframe on the Audi Cabriolets (convertibles), or the similar plastic aero tray which is fitted to the new 2019-> VW Polo.

This Tiguan subframe undertray has a wavy edge (on the leading edge) which contours around the lower engine/gearbox mount bush. On the Tiguan, the thin plastic aero tray (diesel engine noise insulation) & optional reinforced skid tray have a matching wavy rear edge to join upto this subframe tray. The current Tiguan is the same MQB platform as the MK7 Golf, however due to it being an SUV, there has to be more ground clearance etc. Therefore, the front bumper assembly & crash rails appear to be higher off the ground & further away from the cars floor pan & front sub frame. The front subframe has taller legs which connect it to the crash rails, & the front skid tray is deeper & more angled at the front section. Therefore, you cannot use the Tiguan skid tray on the MK7 Golf!

To fit this subframe tray with a full cover engine bay tray, you either have to use the MK7 Golf thin plastic aero tray which has the wavy rear edge, or cut your reinforced skid tray which as the straight rear edge! Realising that I would be required to drill three new holes in the subframe, & cut my VW skid tray, I put this modification on hold. However, I decided to revisit this modification a few months ago & found that somebody on a forum in Romania had actually done it! However, this person only had the full aero tray which has the wavy rear edge, & they had just fitted the Tiguan subframe tray as VW does to the Tiguan with NO modification.

https://vwforum.ro/topic/135866-gol...inamice-si-nvh-noise-vibration-and-harshness/
 
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golfdave

Drag Racing Champion
Location
Scotland (U.K.)
Car(s)
MK7 Golf GT Estate
Part 2 of 4
Parts required

VAG ETKA illustration for VW Tiguan/2016/Engine/Assembly Carrier/No.199-150

To fit as per VW Tiguan
Parts list & approx. costs in UK £
Item No.16:- 3Q0 199 110 B,
Underbody trim, £18.83 (x1)
Item No.17:- N 906 312 02, Riveted cap nut M8/0.5-3mm, £2.05 (x2 quantity)
Item No.18:- WHT 000 729 A, Hex head bolt self locking with captive washer, M8x20mm (Z12), £1.45 (x2)
Item No.19:- WHT 008 023, Plastic spreader rivet (light grey with foam washer) (8x10), £1.52 (x3 quantity) (new version of the old plain black N 038 549 4)

Modified parts to fit as per my way
I decided to not use the plastic spreader rivets (Item No.19) or the M8 combi bolt/washer (Item No.18), for several reasons. If the plastic rivets fail the tray is held up by just the two bolts at the front. This makes the tray hang at an angle which is ok if you are driving forwards. However, if you reverse, the tray will dig into the road. This is not much of a problem on the Tiguan as it has more ground clearance than my MK7 Golf.

The Tiguan subframe has a slightly different underside, which the tray has been made to perfectly match. This causes slight problems when trying to get a perfect fit on the MK7 Golf subframe & I think the plastic rivets may not hold (over time) due to the “twist/torsion” force of getting it to fit! Therefore, I also had to “trim” the tray to shorten parts of the lip/upstand which caused interference.

The combi bolt/washer is a new item from VW which has blue thread lock on it. Apparently VAG are treating these as use once/throw away & fit new due to the pre-applied thread lock! I prefer to fit Marine grade A4 stainless steel if I can find it & also I decided to use DIN washers on each side of the tray to clamp the tray in a nice “sandwich”. You don't have to use a washer each side of the tray, thus only requiring half the quantity of washers.

To fit as per my way
Parts list & approx. costs in UK £
Item No.16:- 3Q0 199 110 B,
Underbody trim, £18.83 (x1)
Item No.17:- N 906 312 02, Riveted cap nut M8/0.5-3mm, £2.05 (x5 quantity) (you could get similar from “Accu” below)
M8x20mm, A4 grade stainless steel bolts with flange heads, (x5 quantity)
M8x DIN size, A4 grade stainless steel washers, (x10 quantity)

https://www.accu.co.uk/en/797-shop

ETKA diagram front subframe cover.jpg
 
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golfdave

Drag Racing Champion
Location
Scotland (U.K.)
Car(s)
MK7 Golf GT Estate
Part 3 of 4
Fitting


As per VW Tiguan

Basically, the same as “my way” with the following alterations:-
1. Do not enlarge the three rear holes in the tray to 13mm.
2. The three new holes in the sub-frame for the plastic spreader rivets, drill to 8mm using a cone “step-drill”, then enlarge to 9mm using a 9mm drill bit.
3. You can trim the tray as I have done for a better fit.

Modified fitment as per my way
Safely jack up the front of the car to gain access to the underside of the front sub-frame. I you have the VW reinforced skid tray fitted remove it now (the full aero tray joins to this Tiguan tray correctly). Clean the metalwork around the two existing hex shaped holes near each of the front pivot bushes for the lower wishbones (I used WD-40). Install a rivet-nut into each hole as per your rivet-nut tool instructions.

WARNING:- most of the positioning & trimming is not measured, but done using your “eyeball”.

Enlarge the 3 rear holes in the tray to 13mm, & smooth the lip/upstand “humps” in the areas marked in the picture. Please fit & refit the tray to ensure you have trimmed the correct amount! You still require the “lip”, but the finished lip has to be shorter & more even in height.

Temporarily fit the tray using the front bolts with a washer each side of the tray & loosely tighten up (using a 13mm hex socket) to hold the tray to the subframe. Position the tray making certain that it 100% covers the whole of the gearbox/lower engine mount bush & metal “ring” (actually it should “clip” over the front edge of this). Also align the notches in the sides of the tray with the edge of the sides of the wishbones. Then using a scribe tool mark the centres of the two rearmost holes. Drill these carefully to 10mm using a cone “step-drill”, then enlarge to 11mm using an 11mm drill bit. Use an old toothbrush/etc. to remove the metal swarf from the rear area of the hole, otherwise it will sit there & rust!

Fit rivet-nuts to these two holes, refit the tray with the bolts & washers & move it as far forward as it will go. Now scribe the middle hole in the tray onto the metal. Remove the tray & measure approx. 4mm from the most forward part of the hole marking into the centre of hole, mark this spot & drill this to 10mm using a cone “step-drill”, then enlarge to 11mm using an 11mm drill bit. This is to get the bolt at the front of the tray hole & as far away from the power steering motor, as the back of the rivet-nut could interfere with it if too close! You can just drill on the centre point, as much of the positioning of the holes/tray is down to how the tray fits your subframe & the two rear holes you have drilled! When drilling the centre hole, I placed a block of wood behind the metal & in front of the electric motor for the power steering to prevent damage to it. Again, remove the metal swarf. Fit a rivet-nut to the hole, & re-fit the tray using a washer each side of the tray to clamp it in a “sandwich” (you don't have to use a washer each side of the tray). I used a small amount of blue thread lock on each bolt & did them up tight, but not too tight otherwise you risk cracking the tray!

Please also note that the yellow coating on the front subframe in the photos is "Waxol" wax spray on protector which I applied.

Modifying the VW reinforced skid tray (if you have this)
To cut the VAG reinforced skid tray to join up to the Tiguan tray, I first remounted the skid tray then mounted the Tiguan tray over it to mark the area to be cut. Mark/scribe onto the skid tray the outline of the Tiguan tray & remove both trays. You will need to use a “jigsaw” power tool fitted with a short length, thin blade, to cut curves, preferably for cutting Kevlar/Aramid fibre as the skid tray is reinforced with this! I only had short, thin blades, for cutting fine curves in wood, so used these. Set tool to “vertical” 90 degree, no “cant” & take it slow. I wore through two new blades as the fibres blunted the blades! Then I used several “Stanley” blades to trim/smooth/shape, so it looked factory like the Tiguan skid tray! It took me two trial re-fits & re-cuts to get perfect gap between the two trays! I also applied a thin layer of weatherproof clear glue to the new raw edges to seal them up.

Front subframe cover mod.jpg
 
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golfdave

Drag Racing Champion
Location
Scotland (U.K.)
Car(s)
MK7 Golf GT Estate
Part 4 of 4
Results

Enjoy a cleaner engine bay, with less salt/grit/mud etc. getting in! Also know that the electric steering motor & cables are better protected! I have also noted that there appears to be less noise coming from the lower areas in the front footwells, obviously there is less air turbulence, & therefore less noise!

Conclusions
Again, yet another perfect example of serious penny pinching from the bean counters at VAG!
 
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southpawboston

Drag Race Newbie
Location
Somerville, MA
Dave, I really wish you wouldn't keep posting these, because every time you do I have to pay E-Acca shipping all over again :p

Good work as usual. (y)

I did the thin aero tray, front exhaust cover and rear side panel additions last year. I've got the rear axle cover waiting to be installed, and I just placed an order for the rear axle resonance damper. If only I had waited two weeks. Damn, those shipping fees are adding up! :sneaky:
 

golfdave

Drag Racing Champion
Location
Scotland (U.K.)
Car(s)
MK7 Golf GT Estate
Dave, I really wish you wouldn't keep posting these, because every time you do I have to pay E-Acca shipping all over again :p

Good work as usual. (y)

I did the thin aero tray, front exhaust cover and rear side panel additions last year. I've got the rear axle cover waiting to be installed, and I just placed an order for the rear axle resonance damper. If only I had waited two weeks. Damn, those shipping fees are adding up! :sneaky:
Sorry!!!...….haha!!

Having the full aero cover which has the wavy edge, your job is simpler!....just take your time in positioning the tray to mark the places to drill...!!
 

golfdave

Drag Racing Champion
Location
Scotland (U.K.)
Car(s)
MK7 Golf GT Estate
Just corrected the bolt size I used...20mm long,... NOT 25mm long...!!
 
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quailallstar

WOB DJ496
Location
Ormond Beach, FL
Car(s)
MY19 MK7.5 GTI Bunny
This is great! More $ I will now need to spend :p
 

quailallstar

WOB DJ496
Location
Ormond Beach, FL
Car(s)
MY19 MK7.5 GTI Bunny
This is on my long to-do-list! I don't suspect the tray can be ordered from a US dealership :(
 
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