So, since I put pics up of my Boost Gauge Air Vent on the "What have you done to your A3 (8p) this week" I've had a few PMs asking for details on what parts I used, so thought I'd try and write up a guide on how I went about it.
Parts Needed:
The dial is fast, and the boost pressure is bang on what it should be so I'm happy.
As this is a vac-line boost and not an OBD2 one, you'll need a boost tap:
BCS fitted mine as part of the Powervalve exhaust but that's the one they used, super easy to fit onto the right hand side of the inlet manifold and then clip the PCV hose back on. You then fit one of those small cylinders into it (remove the plug first with an Allen key) and that's what your hose connects to (see photo). There are 2 taps off mine as it goes to the exhaust valve, but you'll only have 1.
Part number - 8p0820901c
If yours is black and not silver then the part number is 8P0820901A. Plenty of those on Ebay also for about £10-15.
Take the air vent apart and remove all the fins and the back plate so that it's empty. Taking the air vent apart is a little tricky, I found a guide for an Audi TT, it's identical to the A3/S3 air vents and helped massively:
http://www.p3cars.com/content/pdf/a3tt-vent.pdf
- Misc electrical wire and connectors, electrical tape - Depends how you're going to wire this up, but you'll need a few feet of insulated electrical wire to connect the gauge to power and earth. A few misc connectors would help here also. B&Q sell all this sort of stuff, I got a pack of ring connectors (for the earth bolt) and some crimp male/females for making the extension cables.
- Socket set for removing the glove box.
Installation:
Removing the existing air vents are easy, they just pull out. Get something thin under the edges like a knife and slowly pull it and wiggle it until it comes out entirely.
You then also need to plug the AC vent behind the air vent so that you don't waste air con blowing into the back of your boost gauge. I did what I've seen others do and shove something in it. I got an old pillow case, cut it in half and unceremoniously stuffed it into the hole - (see photo). Not the most elegant solution, but when I tried to make a piece of cardboard to block it instead it was impossible to get the air vent to fit all the way back in. This was way easier and just as effective.
You'll need to consider how you're going to connect the boost gauge to a 12V power supply as well as earth it.
The red cable is live, and wants a +12V. The black cable is neutral/earth and needs connecting to a grounding point/chassis.
I've got an aftermarket Xtrons Android head unit and one of the wiring looms has a 12V output wire for a camera which I used for the live. If you don't have this and use a standard head unit you've got a bit more work to do as you'll need to wire this into the fusebox to the right of the steering wheel. If that's the case for you then you'll likely want a fuse holder adapter like this.
You'll have to make a longer wire and then wire that under the steering wheel (no idea on how to do this, there are guides around I think) and to the fusebox and choose which fuse to connect it to, usually people go for the cig lighter as it's on with the ignition.
For earth that's easy, make a small extension wire and connect it to the chassis. If you choose to install yours into the vent I did (centre, right) above the head unit then there is a bolt on the chassis a few inches below the hole where the head unit sits which is easy to wire upto, just get a ring connector and make a little earth wire. Unscrew the bolt, put the ring connector on and do it back up. Here's what mine looks like when I did it for the Xtrons which is also earthed to the same point (see photo).
I've not got any pics of the extension wires I made for mine but it's easy to do with some cable and crimp connectors so you plug/unplug it as needed.
Once that is out completely, remove some trim from the piece directly behind where the glove box was where the carpet ends in the footwell and you'll see a huge bundle of cables that go through the firewall into the engine bay. If you can't see it you're not looking far enough up.
What I did was get a large blunt Phillips screw driver and shove it gently through this hole slowly until I could get past the green sealant and then see it from the engine bay where the battery is (remove the battery entirely, and the plastic box it sits inside) and then you can feed the vac line onto the end of it and slowly pull it back through. I've seen people do it with an old wire coat hanger also, there are some videos on YouTube but maybe someone has a better method they can share with us.
Then I just fed and weaved the vac line through parts of the dashboard to keep it out of the way of the glovebox until I got it to behind the head unit and then that was it. No pics of this part sorry, I'm not removing the glovebox again in a hurry as it's a pain to do, but it's straight forward really.
Here's the finished product:
Photo - Daytime Ignition Off
Photo - Daytime Ignition On
Photo - Nighttime Ignition On
Parts Needed:
- Gauge
The dial is fast, and the boost pressure is bang on what it should be so I'm happy.
As this is a vac-line boost and not an OBD2 one, you'll need a boost tap:
- Boost Tap
BCS fitted mine as part of the Powervalve exhaust but that's the one they used, super easy to fit onto the right hand side of the inlet manifold and then clip the PCV hose back on. You then fit one of those small cylinders into it (remove the plug first with an Allen key) and that's what your hose connects to (see photo). There are 2 taps off mine as it goes to the exhaust valve, but you'll only have 1.
- Spare Air Vent (Optional)
Part number - 8p0820901c
If yours is black and not silver then the part number is 8P0820901A. Plenty of those on Ebay also for about £10-15.
Take the air vent apart and remove all the fins and the back plate so that it's empty. Taking the air vent apart is a little tricky, I found a guide for an Audi TT, it's identical to the A3/S3 air vents and helped massively:
http://www.p3cars.com/content/pdf/a3tt-vent.pdf
- Other Misc Parts:
- Misc electrical wire and connectors, electrical tape - Depends how you're going to wire this up, but you'll need a few feet of insulated electrical wire to connect the gauge to power and earth. A few misc connectors would help here also. B&Q sell all this sort of stuff, I got a pack of ring connectors (for the earth bolt) and some crimp male/females for making the extension cables.
- Socket set for removing the glove box.
Installation:
- Assemble your gauge into your air vent:
Removing the existing air vents are easy, they just pull out. Get something thin under the edges like a knife and slowly pull it and wiggle it until it comes out entirely.
You then also need to plug the AC vent behind the air vent so that you don't waste air con blowing into the back of your boost gauge. I did what I've seen others do and shove something in it. I got an old pillow case, cut it in half and unceremoniously stuffed it into the hole - (see photo). Not the most elegant solution, but when I tried to make a piece of cardboard to block it instead it was impossible to get the air vent to fit all the way back in. This was way easier and just as effective.
- Wiring
You'll need to consider how you're going to connect the boost gauge to a 12V power supply as well as earth it.
The red cable is live, and wants a +12V. The black cable is neutral/earth and needs connecting to a grounding point/chassis.
I've got an aftermarket Xtrons Android head unit and one of the wiring looms has a 12V output wire for a camera which I used for the live. If you don't have this and use a standard head unit you've got a bit more work to do as you'll need to wire this into the fusebox to the right of the steering wheel. If that's the case for you then you'll likely want a fuse holder adapter like this.
You'll have to make a longer wire and then wire that under the steering wheel (no idea on how to do this, there are guides around I think) and to the fusebox and choose which fuse to connect it to, usually people go for the cig lighter as it's on with the ignition.
For earth that's easy, make a small extension wire and connect it to the chassis. If you choose to install yours into the vent I did (centre, right) above the head unit then there is a bolt on the chassis a few inches below the hole where the head unit sits which is easy to wire upto, just get a ring connector and make a little earth wire. Unscrew the bolt, put the ring connector on and do it back up. Here's what mine looks like when I did it for the Xtrons which is also earthed to the same point (see photo).
I've not got any pics of the extension wires I made for mine but it's easy to do with some cable and crimp connectors so you plug/unplug it as needed.
- Vac Line
Once that is out completely, remove some trim from the piece directly behind where the glove box was where the carpet ends in the footwell and you'll see a huge bundle of cables that go through the firewall into the engine bay. If you can't see it you're not looking far enough up.
What I did was get a large blunt Phillips screw driver and shove it gently through this hole slowly until I could get past the green sealant and then see it from the engine bay where the battery is (remove the battery entirely, and the plastic box it sits inside) and then you can feed the vac line onto the end of it and slowly pull it back through. I've seen people do it with an old wire coat hanger also, there are some videos on YouTube but maybe someone has a better method they can share with us.
Then I just fed and weaved the vac line through parts of the dashboard to keep it out of the way of the glovebox until I got it to behind the head unit and then that was it. No pics of this part sorry, I'm not removing the glovebox again in a hurry as it's a pain to do, but it's straight forward really.
Here's the finished product:
Photo - Daytime Ignition Off
Photo - Daytime Ignition On
Photo - Nighttime Ignition On
Last edited:
