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The rear window gets dirty because the flow separates as soon as it comes off the hatch spoiler, creating a giant area of vacuum behind the car, which sucks dirt up from anything your wheels kick up off the road (blue regions below). Increasing the height of the hatch spoiler means a bigger area of low flow/ vacuum in blue below. So even more dirt sucking! Plus that area of vacuum is literally pulling on the rear of your car as if you have a parachute deployed
Would a reversed spoiler like seen on some GM product from the 90's help keep the rear window cleaner?

 

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Mechanical engineer, engine dynamometer testing. But fascinated by aerodynamics. I aeromodded my 03 Jetta TDI from 47 mpg hwy to 56 (some of the engine mods probably helped too).

The rear window gets dirty because the flow separates as soon as it comes off the hatch spoiler, creating a giant area of vacuum behind the car, which sucks dirt up from anything your wheels kick up off the road (blue regions below). Increasing the height of the hatch spoiler means a bigger area of low flow/ vacuum in blue below. So even more dirt sucking! Plus that area of vacuum is literally pulling on the rear of your car as if you have a parachute deployed (hence aforementioned mpg loss if you make it bigger).

View attachment 216237
Where is the graphic that demonstrates how the spoiler creates drag? I’d like to see that. I’ve got a 3D model of my car. Maybe someone with a paid Fusion 360 subscription can do some analysis on it.

If you really think about it, the spoiler is designed to create a sharp end to the rear of the body to more effectively detach the laminar airflow from the car vs having it curl under the rear end and create drag. Like when you pour water out of a glass with a wide radius on the edge. The water will tend to cling to the lip and pour down the side and all over. The sharper the edge, the better the water separates from the lip of the glass. Air being a fluid, it behaves in the same way.

NDB
 

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I'm getting ready for a road trip to watch the SLS rocket launch in Florida and then drive up the east coast! Got some early maintenance in these past couple of days: oil change, air filters, and rotated my tires. First time I'm using my modded oil extractor with a vacuum gauge, it worked out really well! I only had to pump it a few times instead of every couple of minutes. Also first time using a floor jack and jack stands lol.


I followed this for the jacking:
Bummer on the Artemis launch, are you gonna resked to Saturday?
Speaking of which- gotta be more car nerds interested in this, and I wonder if any are going to Bolsa Chica for Starship (whenever*, separate thread to follow...)

PS: on the extractor mod: very cool! How does one get a clean sample for an oil analysis, for Blackstone Labs as an example, when using an extractor, I wonder?

(I've been following and want to copy the example of a couple here, to assess changes in my use, for example before and after towing or softroading in hot summer to see if anything changes in the oil, metals, etc.)

Gonna get a Harbor Freight extractor (and I'll call the Blackstone folks on this query)
And/or use it every other change to save on the extra work jacking up and taking off/on lower engine shield. (In order to sample the oil mid stream).

I got a busted T20 nutzert in one corner that requires a bit of extra fiddling each time to reattach a nut which is part of that minor PITA the extractor avoids.
 

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Where is the graphic that demonstrates how the spoiler creates drag? I’d like to see that. I’ve got a 3D model of my car. Maybe someone with a paid Fusion 360 subscription can do some analysis on it.

If you really think about it, the spoiler is designed to create a sharp end to the rear of the body to more effectively detach the laminar airflow from the car vs having it curl under the rear end and create drag. Like when you pour water out of a glass with a wide radius on the edge. The water will tend to cling to the lip and pour down the side and all over. The sharper the edge, the better the water separates from the lip of the glass. Air being a fluid, it behaves in the same way.

NDB
This is a fascinating topic, and because I'm the worst offender at thread jacking...🤷🏼
I've created a thread on it for more detail, here:
 

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Bummer on the Artemis launch, are you gonna resked to Saturday?
Speaking of which- gotta be more car nerds interested in this, and I wonder if any are going to Bolsa Chica for Starship (whenever*, separate thread to follow...)

PS: on the extractor mod: very cool! How does one get a clean sample for an oil analysis, for Blackstone Labs as an example, when using an extractor, I wonder?

(I've been following and want to copy the example of a couple here, to assess changes in my use, for example before and after towing or softroading in hot summer to see if anything changes in the oil, metals, etc.)

Gonna get a Harbor Freight extractor (and I'll call the Blackstone folks on this query)
And/or use it every other change to save on the extra work jacking up and taking off/on lower engine shield. (In order to sample the oil mid stream).

I got a busted T20 nutzert in one corner that requires a bit of extra fiddling each time to reattach a nut which is part of that minor PITA the extractor avoids.
Just dump it out of the extractor tube.
 

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Where is the graphic that demonstrates how the spoiler creates drag? I’d like to see that. I’ve got a 3D model of my car. Maybe someone with a paid Fusion 360 subscription can do some analysis on it.

If you really think about it, the spoiler is designed to create a sharp end to the rear of the body to more effectively detach the laminar airflow from the car vs having it curl under the rear end and create drag. Like when you pour water out of a glass with a wide radius on the edge. The water will tend to cling to the lip and pour down the side and all over. The sharper the edge, the better the water separates from the lip of the glass. Air being a fluid, it behaves in the same way.

NDB
No you're definitely right about that, you want sharp edges all around the rear for flow detachment. Most new sedans and crossovers (for example the prius rear end) have sharp edges all the way around. But IMO, the stock alltrack/sportwagen hatch spooler is sharp "enough" already - so increasing the size of the rear wake can only hurt - i think. When I still had my alltrack, I was contemplating a hatch spoiler extension, that could gently increase the taper to the rear and end with a nice sharp edge; never got around to fabricating anything.
 

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No you're definitely right about that, you want sharp edges all around the rear for flow detachment. Most new sedans and crossovers (for example the prius rear end) have sharp edges all the way around. But IMO, the stock alltrack/sportwagen hatch spooler is sharp "enough" already - so increasing the size of the rear wake can only hurt - i think. When I still had my alltrack, I was contemplating a hatch spoiler extension, that could gently increase the taper to the rear and end with a nice sharp edge; never got around to fabricating anything.
what’d you replace the Alltrack with
 

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what’d you replace the Alltrack with
A pile of CASH. Lol. Carvana kept driving up their offer to me until I finally couldn't say no; way more than I bought it new for.

Picked up a low-mile '09 Jetta 2.5 manual for a daily, it's actually been pretty fun to mod.

 

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A pile of CASH. Lol. Carvana kept driving up their offer to me until I finally couldn't say no; way more than I bought it new for.

Picked up a low-mile '09 Jetta 2.5 manual for a daily, it's actually been pretty fun to mod.

I love that progression. 08 Salsa Red MK5 Jetta 2.5 was my first car, and what started my lifelong love affair with VW. My Alltrack did not make me feel the way my MK5 did. Granted, I was also 17 at the time.

I too sold my Alltrack for 7K more than I paid new, after 21 months /19K miles of ownership, with a 5K down payment and 0% financing to boot. I bought a Touareg TDI exec with the massive influx of cash instead of pocketing it and going for something fiscally responsible. That said, my Touareg DOES make me feel the way my MK5 Jetta did way back when. Couldn’t be happier with my decision.
 

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Bummer on the Artemis launch, are you gonna resked to Saturday?
Speaking of which- gotta be more car nerds interested in this, and I wonder if any are going to Bolsa Chica for Starship (whenever*, separate thread to follow...)

PS: on the extractor mod: very cool! How does one get a clean sample for an oil analysis, for Blackstone Labs as an example, when using an extractor, I wonder?
Yea I'm gonna stick around for the Saturday launch. Still not sure what I'll do if they scrub again.

This particular extractor only sucks, you have to pour it out like a bucket to empty it. My old Mityvac pushed and pulled through the hose.
 

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Yea I'm gonna stick around for the Saturday launch. Still not sure what I'll do if they scrub again.

This particular extractor only sucks, you have to pour it out like a bucket to empty it. My old Mityvac pushed and pulled through the hose.
Have fun! Historic event, and its a too long drive or I'd be there too.
Was hoping to see Starship launch this fall in Bolsa Chica but thats slid too...
Maybe we need a space geek thread here on vortex and drum up interest in launch parties...😎
 

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65k. Finally got around to replacing the trans oil, 2nd 4motion flush/fill/filter clean, front and rear bevel gear flush/fill. Tell ya what, the trans feels a lot smoother with fresh oil. All oem oils from FCPeuro. Did motor oil as well with liqui moly 5w40. Fresssshhhhh!
 

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I love that progression. 08 Salsa Red MK5 Jetta 2.5 was my first car, and what started my lifelong love affair with VW. My Alltrack did not make me feel the way my MK5 did. Granted, I was also 17 at the time.

I too sold my Alltrack for 7K more than I paid new, after 21 months /19K miles of ownership, with a 5K down payment and 0% financing to boot. I bought a Touareg TDI exec with the massive influx of cash instead of pocketing it and going for something fiscally responsible. That said, my Touareg DOES make me feel the way my MK5 Jetta did way back when. Couldn’t be happier with my decision.
Ya, whatever floats your boat! Cars are emotional things...👍
 

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Have fun! Historic event, and its a too long drive or I'd be there too.
Was hoping to see Starship launch this fall in Bolsa Chica but thats slid too...
Maybe we need a space geek thread here on vortex and drum up interest in launch parties...
Dood! It’s spooky just how similar our minds work. You’re going to have to swing through San Antonio to meet and I can take you to dinner. Then we can proceed to go down to somewhere with a good vantage point and watch it together. I’ve been following SpaceX’s progress since before the Falcon. I even accidentally managed to see a launch the night I moved back out of Kalifornistan while driving out.



Wasn’t sure what I was seeing because it launched from VSFB and I was leaving Ridgecrest which is right there by China Lake NAWS and not far from Palmdale’s “Secret City”. Lots of secret military poop going on in a concentrated area. I thought I was seeing some Area 51 stuff until I saw the booster descending. lol
So sorry once again for the OT post. Let’s start a thread or join a Texas Tank-watching forum.

NDB
 

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Dood! It’s spooky just how similar our minds work. You’re going to have to swing through San Antonio to meet and I can take you to dinner. Then we can proceed to go down to somewhere with a good vantage point and watch it together. I’ve been following SpaceX’s progress since before the Falcon. I even accidentally managed to see a launch the night I moved back out of Kalifornistan while driving out.



Wasn’t sure what I was seeing because it launched from VSFB and I was leaving Ridgecrest which is right there by China Lake NAWS and not far from Palmdale’s “Secret City”. Lots of secret military poop going on in a concentrated area. I thought I was seeing some Area 51 stuff until I saw the booster descending. lol
So sorry once again for the OT post. Let’s start a thread or join a Texas Tank-watching forum.

NDB
You got it! I'll pm ya...may be passing thru early Oct!

Your story reminds me of a VAFB early evening launch that had my wife and daughter texting me while driving "WTF" and half of LA freaking out about UFOs...🤣
 

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Picked up a second hand Van Der Veer Haldex Controller. Pretty cool. Allows you to adjust from 50/50 split to front wheel drive only for burnouts and better fuel economy. Pretty fun. Still messing with it and trying to learn all the settings. Anyone have one of these that could offer any tips?
How much do they go for on the used market? does it have the app to control it on the fly?
 
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