aerodynamics?

[the bruce]

Bruce, I'll take a measurement on the outboard portion of the rain tray if you want to verify.

'Highly requested' !! :thumbsup:

Maybe a couple of spots along the hood. I'm curious about whether some of these after market hoods with vents are actually functional.

I remember VW used hoods with vents as well and I bet they proved engine bay ventilation in the wind tunnel.
You can buy these at Bildon. They are exactly the same. :thumbsup:

 

[ryeboy]

Interesting. I've heard good things about Bildon.

 

[ryeboy]

Possible to get an engine compartment P measurement back to the left of the master cylinder?

Pulling it all together. Again pressures are measured using a Dwyer Magnehelic gauge with a 1/8" id tube running to the indicated location. The tube opening is placed at 90° to the airflow in all cases except "License total" which has the tube opening facing into the airflow. Underbody measure is taken from a bracket attached to the underbody about 2.5" off the tarmac. It probably has a bit of a "ram" effect because I was trying to simulate a duct opening.

Measures are in inches of water at 60, 70, and 80 mph:

UNDERBODY 2.0, 2.5, 3.5
LICENSE STATIC 0.9, 1.2, 1.8
LICENSE TOTAL 1.9, 2.5, 3.5
ENGINE (PASS SIDE) 0.8, 1.2, 1.7
ENGINE (ABOVE MASTER CYLINDER) 0.8, 1.1, 1.2
WHEEL INTERIOR -0.5, -0.2, -0.1

RAIN TRAY (PASS SIDE) 1.1, 1.6, 1.8
RAIN TRAY (CENTER) 1.0, 1.8, 2.0

Bruce, the rain tray pressure at the far side of the tray where it extends over the strut towers is not that different than the measure taken near the center of the vehicle--maybe a little less, but still more than the engine compartment.

The engine bay behind the air box and above the master cylinder has maybe slightly less pressure at speed. Is this a function of the air intake?

As expected, the wheel hub pressures are negative to atmospheric. This trends towards a neutral pressure with increased speed. Nonetheless, there is always a decent pressure differential to any airflow collected at the front of the car (fog openings) or from an underbody air collector like a NACA duct.

 

[GTIIII]

That's sweet.

 

[ryeboy]

Any other measurement requests before I dismantle the Magnehelic and its manifold?

For those who want to take your own measurements, it is really quite simple. Dwyer Magnehelic gauges can be snagged off of ebay at ~$30 for a used one. I had a couple on hand and found the 8 inch of water scale very useful. A 4 or 5 inch scale would be even more precise. Don't worry it it looks a bit beaten up...those things last forever. I used 1/8" id aquarium tubing for the measuring end and to make my life easier, I also bought a 8-way switching manifold for aquariums (<$10) that allows up to 8 pressure points to be read in one run. After securing all the tubing with painter's tape, and assigning a spot on the manifold, just find a nice abandoned stretch of highway and set the cruise control at your desired speed (60, 70, 80 mph in my case). Since I didn't have a partner, I had an iphone video record the Magnehelic gauge while I switched the manifold levers one by one. I just narrated the speed and the channel info so I could sort it out later. That way I could keep my eye on the road and make more precise readings after the fact.

Perhaps unsurprisingly, nearby cars can really affect the pressure readings if you are in their lateral wake or their turbulence wake if they are in front of you. If you do your measurements early in the morning on a weekend, the other cars are not too problematic.

 

[the bruce]

ENGINE (PASS SIDE) 0.8, 1.2, 1.7
ENGINE (ABOVE MASTER CYLINDER) 0.8, 1.1, 1.2

RAIN TRAY (PASS SIDE) 1.1, 1.6, 1.8
RAIN TRAY (CENTER) 1.0, 1.8, 2.0

Bruce, the rain tray pressure at the far side of the tray where it extends over the strut towers is not that different than the measure taken near the center of the vehicle--maybe a little less, but still more than the engine compartment.

The engine bay behind the air box and above the master cylinder has maybe slightly less pressure at speed. Is this a function of the air intake?

I expected a larger difference. In fact it isn't worth considering
where to cut or remove the seal. :frown::frown:

LICENSE STATIC 0.9, 1.2, 1.8
LICENSE TOTAL 1.9, 2.5, 3.5
WHEEL INTERIOR -0.5, -0.2, -0.1

As expected, the wheel hub pressures are negative to atmospheric. This trends towards a neutral pressure with increased speed. Nonetheless, there is always a decent pressure differential to any airflow collected at the front of the car (fog openings) or from an underbody air collector like a NACA duct.

I think your data prooves the efficiency of brake ducting. :thumbsup:

 

[ryeboy]

I expected a larger difference. In fact it isn't worth considering
where to cut or remove the seal. :frown::frown:


There is always the Bildon hood vent mod :smile:


I think your data prooves the efficiency of brake ducting. :thumbsup:

Now if only someone made something like this for the mkV brakes:

That said, the Binary Engineering Evo duct would not work for my purposes, but that location is a sweet place to force air.

It's not obvious how to feed air into the rotor hat area of the mkV given the physical constraints of the spindle, the ABS sensor, steering linkage, etc. :frown:

Inevitably it will be a compromise, but what in life is not? :wink:

 

[the bruce]

Two years ago I had a chance to get a original VW Motorsport hood (yes, the one the Bildon sell) for
only 600,-- €.
I didn't buy them because of these visible vents. Non-TÜV-approved carbon hoods aren't legal here.
Even more the seller first offered it for 400,-- €, some days later he wanted 600,-- €, not the kind of
business I like.

But I now regret my decision though.

I posted a pic of a Mk. ventilation behind the hub earlier in this thread. Between hub and (stock) caliper
isn't the necessary space.

 

[ryeboy]

Two years ago I had a chance to get a original VW Motorsport hood (yes, the one the Bildon sell) for
only 600,-- €.
I didn't buy them because of these visible vents. Non-TÜV-approved carbon hoods aren't legal here.
Even more the seller first offered it for 400,-- €, some days later he wanted 600,-- €, not the kind of
business I like.

But I now regret my decision though.

I posted a pic of a Mk. ventilation behind the hub earlier in this thread. Between hub and (stock) caliper
isn't the necessary space.

Yes, you did post some nice pics, but except for the Borla example, most ducts direct air onto the inside rotor face which seems like a questionable design. I've heard of cracking coming from uneven cooling of inner and outer rotor faces.

There is about 3/4" of space where one can direct air into the rotor hat around the wheel hub on the downstream part of the spindle. The ABS sensor however is smack in the middle of this ducting "real estate" opposite the caliper. It's not impossible to work around the ABS wire, just adds a complication. Sigh...

 

[junker]

Rear Axle Cover

Today I received the TDI BlueMotion rear axle cover and want to confirm the parts list:

1K0501713D Axle Cover
1K0501682 Bracket
N90548305 Bolt
N90183802 Nut

I made the mistake of ordering a few extra mounting pieces based on the exploded EKTA view. You do not need two plastic nuts as they are pre-mounted on the cover and you do not need the threaded stud, as the bracket already has it. So, you only need the 4 parts listed above. I'll try to install later and see how it goes.

Thanks for the great info Bruce:thumbsup:

Here are a few detailed pictures:

 

[the bruce]

Yes, you did post some nice pics, but except for the Borla example, most ducts direct air onto the inside rotor face which seems like a questionable design. I've heard of cracking coming from uneven cooling of inner and outer rotor faces.

There is about 3/4" of space where one can direct air into the rotor hat around the wheel hub on the downstream part of the spindle. The ABS sensor however is smack in the middle of this ducting "real estate" opposite the caliper. It's not impossible to work around the ABS wire, just adds a complication. Sigh...

First one is a Mk.V "Edition 30" (which came with a K04 from factory, but with the same poor
brake system). Second is a Mini but with some talent you'll manage to get it fitted on a Golf.

Unfortunately I have S3 hubs which are much bulkier than the steels hubs. There's even less space.

 

[junker]

My 2007.5 GTI (build date 1/07) did not have the required axle bolt for one side of the shield so I'm glad I ordered a few extra parts.

I'm going to drill a small hole in the axle for placement of this bolt:

Blindnietschraube
N91001101

Today I received the TDI BlueMotion rear axle cover and want to confirm the parts list:

1K0501713D Axle Cover
1K0501682 Bracket
N90548305 Bolt
N90183802 Nut

 

[ryeboy]

First one is a Mk.V "Edition 30" (which came with a K04 from factory, but with the same poor
brake system). Second is a Mini but with some talent you'll manage to get it fitted on a Golf.



Unfortunately I have S3 hubs which are much bulkier than the steels hubs. There's even less space.

I have the passat hubs--same problem I imagine as the S3. Very bulky.

 

[junker]

RS3 Front Brake Vents

Here are a few pictures of the front RS3 brake vents that I will be installing during my upcoming brake upgrade project. I'll update with install photos and let everyone know how well they mount up to steel GTI control arms and whether they needed any modification to fit. Thanks for turning us on to these Bruce! :thumbsup:

 

[the bruce]

:thumbsup:

If there are issues use a second nut instead of the alloy tube.
This may be easier.