AFM Relocation Procedure
The original article lead to a link that was hosted on Fullboost, here.
Unfortunately that link now leads to a 404 page.
I have made an effort to resurrect the original guide posted on N12 Turbo. You can see the guide below.
There has always been a great need for someone to complete the Airflow meter (AFM) relocation article as seen on Fullboost you can view that article here. It is only now that someone has had enough time to actually write this up. I will try to better explain what was said in the Fullboost article (as I know some people have had problems) and will extend it to cover plumbing the original log back up to include the idle sensors again in the system to regain a perfect cold/warm idle after the relocation is complete.
Here is a picture of the standard position of the Airflow meter for those of you that don’t know what we’re talking about; the idea of this modification is to move the AFM (within the red circle) from where you see it in the picture to a better position right off the turbo, the reason for this is to eliminate the 6 or so feet of intake piping to leave you with a nice short air intake. The results of his mod are as follows; your turbo will spool up much quicker, will increase your turbo’s life and will also cause a huge increase in the sound that your turbo makes while spooling up (sounds great).
Stuff you need to get first:
First of all you’ll need to purchase a pod type filter (these retail at Autobarn for around $50 or less, you can go for a more expensive filter such as K&N however I’ve never bothered with an expensive one so I can’t comment on the results).
Next you will need a small length of pipe which will go between the turbo and airflow meter, I will discuss this more in detail later when we get to it (I just don’t want you to pull your car apart like I did when I relocated mine and have no way to get anywhere to buy the parts).
Also depending on the way you choose to set it up you may need some flexible pipe to go between your AFM and pod filter.
Time to get started:
First thing to do is remove the airflow meter from the car; this is a simple task of undoing a few bolts and undoing the clamp that holds the rubber piece to the airflow meter. There is also a plug on the airflow meter (with a wire coming out of it) for now just unplug this from the AFM and leave it where it is (we will need this later).
When you have the AFM removed from the car just leave it somewhere safe for later.
It is here you should also remove the flexible piece of pipe that was previously connected to the engine side of the AFM, along with the old air box (bottom left corner of the above picture). I recommend leaving the removal of the old air box for later as I remember having a fun time pulling the thing out. There are quite a few nuts which are near to impossible to get to, which makes this task fun.
The next step relates to the hose in the picture to the right (in the red circle). If you are planning on keeping the idle sensors in the system then this part doesn’t affect you, however if you don’t necessarily need a cold start idle you can do as the Fullboost article and just plug this pipe up, this makes the relocation process a little simpler however cold start idle comes in useful in colder areas (you can just plug this pipe up with a bolt or something simple like that).
We now need to familiarize ourselves with the ‘log’ (shown in the green rectangle) this pipe runs from where the AFM was previously connected to the other side of the engine.
Next step is to disconnect the other two pieces remaining in the system; there is a big metal pipe which goes from the other side of the log down to a rubber piece which connects to the turbo (this will have a rocker cover breather line attached to it, just leave the breather hose for now), unclamp both pieces and remove them.
Now we need to free up the plug from the airflow meter (we moved this from the AFM right at the beginning). What we need to do is slit along the wiring loom that it runs in to give us some slack so the plug is able to reach the AFM at the new location. The wiring loom (as shown on the picture to the right as shown by the red lines) needs to be slit from the other side of the log all the way to where you see it in the picture (in the green circle). Just be warned that it’s a little tricky to reach it all the way through. You now need to feed the plug through the gap to the other side of the engine bay.
The difficult/annoying parts are done, now we just need to make some decisions. First of all you need to decide what to do with the breather line from the rocker cover; this will also influence how to connect the AFM to the turbo, these decisions should be made together.
With the breather you can choose to do a few things:
- You can simply cut the breather pipe shorter (so it’s not in the way) and leave the hose to breathe to atmosphere, I cannot recommend this though as this is illegal.
- You can try something like in the picture to the right and put a filter on the breather (A filter like this will cost around $10 from Autobarn).
- Or you can put the breather back into the system, if you choose this way it will also make it more convenient for the later part when we re-fit the idle control sensors. If you choose this way leave the breather hose alone for the moment as we will need to incorporate this in the next step.
Now with the pipe that connects the Airflow meter to the Turbo we also have a few choices. If you chose not to keep the idle sensors nor put the breather back in the system then you can simply connect the AFM to the Turbo with a pipe and some strong hose clamps. I would recommend using what’s called Turbo pipe; this is high temperature/high pressure rubber pipe so it is the best stuff to use. For fitting to the AFM you will need 2″ Pipe (~56mm), this size pipe will also fit onto the turbo inlet if you have a standard T2 turbo or smaller T25.
Another option is to do as the picture to the right, if you intend on putting the breather or the idle sensors or both back into the system. For this you can you the standard rubber join which came off the turbo originally however this will leave your airflow meter at an angle which requires you to mess around with other things so I don’t recommend using it.
For this method you will need to go to a hose company such as Enzed and buy a threaded hose fitting along with a steel bolt or as I was given a steel joiner, you will need to take this to an exhaust shop and get approximately a 2″ length of 2¼” Exhaust pipe and get your fitting welded into that (Cost me $5 at an exhaust shop). If you want the breather hose back in without idle sensors then I recommend getting a hose fitting which will connect straight into the breather hose, otherwise it doesn’t matter on what size you get just as long as you buy hose to match the hose fitting.
Once you have all of this you should buy 2 small lengths of 2¼” Pipe (I again used turbo pipe) and 4 hose clamps and as shown in the picture above simply place the pipe between the turbo and pipe you had made up and clamp together and the same at the AFM side.
If you have no need for idle sensors in your system this is the end, from here you now just need to plug your AFM back in and attach the pod to the other end of the AFM. Be warned here you must have your AFM upright! This means that the plug will be on the underside of the AFM (should look like in the picture shown above). You will also need to adjust your idle at the screw on the throttle body as your idle will likely drop a fair way.
Putting the Idle Sensors back in:
Now we come to the simple task of putting the idle sensors back in.
The simplest way to do this is as shown in the picture to the right. To do this you should go back to the hoses company you previously went to and buy 2 pieces of 80mm hose approximately 2½” long (I just got radiator hose) along with 4 hose clamps (2 for either side). Now the last piece you need to buy is 2 PVC end-caps (These sell at Bunnings for less than $2). The one you need is called a 60mm PVC end-cap however the outside diameter measures to 80mm.
With one of these end-caps you will need another threaded hose fitting (I also got a nut to hold it in) You will need to drill a hole in the PVC end-cap and insert the hose fitting into that, remember this needs to be air tight (something such as silicone will do to seal the join).
All we do now is place the radiator hose onto the end of the ‘log’ and clamp it on then place the PVC end-cap inside and clamp that on. From here you just have to attach your hose which goes from the piece at the turbo to the top of the log, if you also want the breather back in the system you can purchase a T-Piece and join the breather hose to the pipe also (just cut it in the middle and join the three together)
Last step is to attach the pod filter to the other end of the AFM, you can do this a few ways, mine angles down towards the ground thanks to some flexible pipe (this gets the air coming in from under the car) Others have chosen to keep the pod in a straight line with the rest of the system, it’s just personal preference and how you feel is the easiest way to get it all to fit.
It’s my advice to somehow tie the airflow meter in (so it won’t move), this is just to keep everything safe. I would also recommend making sure the pod is held fairly tight so it won’t move around too much, again this is up to you I just tied some wire around my AFM and fastened it to the battery box (nice and simple and it doesn’t move).
The whole thing should take no more than a few hours to complete and should create at least a 5kW gain on standard boost (according to the Fullboost article).
The whole thing should cost you somewhere around $80 depending on the kind of pod you chose to use. Will also require around 3 hours of your time plus lots and lots of patience!!!