Thread: Here's the SCOOP for 'ya

literally.
Just made up an under bumper scoop for my Tdi this morning.
Would'a done it yesterday arvo .. but bloody work got in the way again.
Actually, health almost got in the way this morning too .. but another story for another time.

Short Version:
Does it work .. much better than I thought


Long Version:
Anyhow, had the idea to make an under car scoop for my Tdi to help with it's running hot on a hot day with AC on .. issue.

Ummed and ahhhed a lot, as I have a D2 part car, and it has what could have been a more ideal solution.

D1 seems to have a plastic 'plate' type device, sits along the top of the chassis rail, and what it appears to do is minimise the amount of air coming through the grille, being deflected downwards and under the car.
It doesn't scoop air under and up and through the radiators at all .. just minimises the loss of air through the grille, and maybe the amount of muck coming under and up to the radiators.

D800E_DSD_3087.jpg
Sorry for the bad pics, but it's hot out and can't be stuffed!
As should be easily noticed but mine is half busted. Trans cooler pipes have melted it, basically into half. If I replace it, at some point it will disintegrate.
The crack on the RHS is repeated on the other side too.

D2 scoop is a much better design(from a cooling point of view tho).
D800E_DSD_3085.jpg
The major difference is, it actually scoops air from under the bumper mid level. Scoop sits on the bottom side of the chassis rail, easily fixed/removed with self tappers(8mm head).

So, as anyone in the right mind would do .. I got the idea that 1+1 =2 .. I have the scoop from the 'D2 parter' .. why not use it.
I can see it'd be easy enough to fit. D1 chassis has the 3 square holes needed for the rear side of the D2 scoop to attach .. just not the two front/side locations. Easy enough to make up a bracket or two to sort that.
So that was my "Plan A".
Recover, or buy the plastic bung thingies needed for the chassis(rear attachments) and make up two brackets to secure front/side tabs locations.

But I changed my mind(mainly cos the D2 scoop is in really good nic(after I gave it a cleanup) .. and thought .. maybe better save for another day(car??)

So, instead I got myself a sheet of 600x450 gal(1.2mm I think) .. and thought maybe just as easy/easier to work with this(for now).
Again, this is more of a proof of concept, than anything else. And it worked absolutely better than I thought it would/could.
Some strange anomalies, but I'm ignoring them as user induced for the time being.

Pics first:
D800E_DSD_3089.jpg
It's literally just a flat sheet, 600mm is ideal between the D1 chassis rails, as will be shown in other pics.
Front 'air dam' is roughly 1" 25mm .. ish. The way I set it up in the end was simply two nut/bolts, where I can(if required) adjust the air dam opening, under the bull bar. The leading edge of the scoop sheet was just shy of the trailing edge of the underside of the bullbar .. my bad on that.
I had to cut the fore/aft length of the sheet to about 340mm(keeping the 600mm width(between chassis rails).

D800E_DSD_3091.jpg
As seen it's just a flat sheet. Reason I thought to go this way was that I just wanted it simple .. thinking just a flat sheet may do the job.
To use the D2 scoop and do the job properly, I'd have needed a sheet of gal anyhow, as the scoop would have sat too far back from the bullbar, and the bullbar may have deflected air away from the scoop, thus defeating half it's purpose. Dunno!!??
But I thought to use the D2 scoop better, a sheet for the back half, with the D2 scoop further forward with it's front edge against the underside of the bullbar. Anyhow, that's why I changed tack and went with the simple flat gal sheet.
Bolt and nut holding the sheet(from flapping about) same at the bullbar end, two nuts to hold the bolt firmly. May try a simpler solution to make it easier to adjust the scoop opening, but as is now, it works.

D800E_DSD_3095.jpg
Shows the rear attachments too. Brackets used were the cheapie Bunnings multi use brackets I used on my Load cover mod. Cut and drilled and just screwed to the scoop/sheet for now. Wanted to tack weld them, but I wanted to get this done in less than half hour before the heat came, and so I could get out for a drive before the cool change .. so time was a factor here too.

D800E_DSD_3097.JPG
600mm wide gal sheet slides perfectly between the chassis rails, and using the bull bar(or shipping/tow loop) bolt points ideal for rear placement. Sheet is about 10mm shy of the trans pipes to be sure not touchy-rubby goings on back there. As as clearly seen, trans pipes would require a vut in the D2 scoop had it been fitted as it is in the D2. Another reason why I wanted to use the D2-gal sheet idea to fit it too.

So, it was between 32-39 out there today. At 32, I don't really remember seeing coolant temps over 100°C, usually occurs from mid 30's and above.
With one eye on the temperature readings on the BoM site, other eye on coolant temp, oil temp, and EGT, quick drive up the Hume, headwind(northerly) of about 40-ish k/h .. so it was going to tax the Tdi heading up and out .. and it did.
Max EGT temp hit 698°C .. which in itself is a win too.
Having done similar drives against similar winds in similar heat .. I've had well over 720 and rising before I've had to back off .. down to unlocked 4th of 3rd .. which means less than 80k/h, or hold 3rd and 4K RPM .. or whatever.
But I just kept foot down, maintained 95 easily, until I got partially blocked by a slower van, down to 90 .. still no worried.
The real win tho ... coolant temps on average in the lower 90's .. as oppose to what I'd have expected in the low 100's and rising!

The problem as I'm seeing it(recording it) is more along the lines of the engine oil temp.
Always, as I've been recording the issue, oil temps are the key data of note in this saga.
Engine oil once the issue starts, quickly rises to the low 90's, and is harder to cool down than the coolant.
Coolant temp increases along with EGT and engine temp.
With EGT(so Tdi specific here) .. once the hard slog is over and EGT drops, coolant drops quickly with it. This is what I've noticed in all the time I've spent noticing it.
But, even with lower EGTs, ie. 500-600 range, not 600-700 range! .. once the oil gets hot, it stays hot, and it's a struggle to keep the entire engine cooler.
eg. on my other runs where coolant hovers in the low to mid 100's range, oil temp runs on the low 90's, maybe 93 max, but I have seen 100 on occasion .. not a lot, but has happened.

SO on the run up north, got as far as Tallarook and turned back, headwind made it harder, but not arduous.
Max temp was 103°C where before scoop it'd be 110°C. But this only tells part of the story. 103 was got on the way back! .. tailwind, and me pushing hard up the steepest part of the freeway(up to just before Wallan).
Just wanted to see how it all went .. The last time I pushed the Tdi hard, was after a bit of other work like installing the boost controller, or the gauges .. again, more to see how it went.
Primarily it ran in the low 90's .. and couldn't believe my eyes seeing it drop into the high 80's
End result is probably 15°C cooler, and even as much as 20°C cooler depending on specific conditions out there.

Weird thing was that for a lot of the way back(tailwind) it actually ran hotter. The coolant that is. EGT maybe on average 100°C cooler, and oil temp about the same.
And here's the oil temp part of the issue rearing it's head again. Oil never topped about 83°C .. one spurious spike in readings .. mainly between 77 and 80 for 99.9% of the time. Both against the wind and with the wind.
Other effect noticed too, I spent some time slipstreaming, and whilst doing that, coolant would increase by about 3°C every time.
More on the anomaly of some hotter temps with the tailwind, compared to the headwind direction:
it only lasted about 15-20mins. Soon as the highest point on the road was hit just before Wallan, temps did drop again slowly .. very slowly. Wasn't until about 15mins later(or more) when I got onto the Craigieburn bypass, where coolant finally dropped back to 85°C.
I was seriously considering pulling over to see if the engine hadn't dropped out or something.
85°C coolant .. and 39°C ambient .. and AC on .. in my Tdi .. would have never thought it possible.

Further to all that .. final confirmation that the scoop is working is that back in the arduous thick of suburbian life ... coolant generally ran back up in the low to mid 90's for the 10min run home on Sydney Rd.
That was normal running before. You wouldn't expect the scoop to help in low speed driving and it didn't. So pretty happy with the result so far.

May do more mods:
If I keep it as is(ie. just the gal sheet) will add some pinchweld to minimise the risk of cuts/abrasions if working under car. will look nicer and may help with potential sound effects(none noticed tho).
Other possible mod is the D2 scoop mod, but as is this is working fine.

One definitely more mod at some point will be the addition of more vents on the face of the bullbar.
Noted over the past few days, almost all modern bars on modern off roaders(Hilux's and (lots and lots of) Rangers!!! ..) .. they seem to have more front side ventilation areas. Lots of narrow wide slots.

D800E_DSD_3101.jpg
So my last mod for this scoop mod will almost certainly be a couple of vents cut out of the bar up front like in the pic(greyed areas).
That gives a lot of air straight and through to the chassis(not directly at the radiators), and the scoop should deflect the air nicely to the radiators.

Mode definitely worth the effort at my end .. could be worth your while too, if you've thought it .. (looking at Jim here! )

May have taken 20mins to cobble(and very cobbled it was .. teck screws and bodge drilling with blunt bits .. etc).
Took me longer due to my new health problem .. but more so to-ing and fro-ing from under car to shed to try this bit, and then that bit.
I had no spare sheeting, but less than $20 from Bunnings for a bit of 450x600 1.2mm sheet.
I think they had thinner sheets too(maybe 0.9) maybe easier to work, but you don't want potential drumming effect(noise) with thin sheeting. 1.2 was the thickest they had tho.

Hope this helps someone out there too.

ps. what looks like old coolant leaks isn't .. it's laziness on my part not cleaning off the overflow effect of when I added pink coolant a year ago!

Originally Posted by trout1105

.... I will either use that JB weld or use some good old Sikaflex for the job.
....

Yeah.. easy to do. No question about that.
The only thing I found 'difficult' was getting the mesh into the exact right shape(curve) and not overly bent it, and have an inwards sag(looked ugly).
So best bet was to give it a bit of tension, so that it followed the natural curve of the grilles outer plastic shape.
This is where the JB Weld stuff came up trumps.
Needed a few heavish items to place onto the mesh to hold it against it's natural tension. tools, some boxes of stuff, etc all placed strategically on the mesh to hold it against the plastic while the glue cured enough to hold it own.
For the JB Weld stuff, 15 mins and good to go. (24 hrs to cure fully)

I have a few various tubes of Sika products .. totally forgot about them tho! So could be useful.
The problem with the usual epoxies is their 'runiness' or their tendency to spread out when applied. The glue needed to be built up, so had to have a high viscosity as it was applied.
If it wasn't built up as a 'blob' over the mesh, it wouldn't hold the mesh down .. just spread across the grille.
The black stuff(haven't tried the others) .. allows this with the right timing. Work the glue for long enough to almost start curing, it thickens a little then apply. It then doesn't run and builds up over the mesh.

I do still have a tube of Loctite GO2 GEL epoxy, and it could have been good too, but experience has shown me it's not very strong.

be sure to post your result when you get around to it too.