Best cold air feed for BMC?

Ant_43 · Post by **Ant_43** » Mon Jun 12, 2006 7:50 pm

Hello everybody,

As you can gather, i have now invested in a BMC CDA induction kit for the gti. I must admit, it sounds lovely when pushing the foot down from low revs - a real nice grrrrrr sound!

Anyways, i have tried a few different ways of connecting the air feed to it, but am still convinced that it's not working as well as it should, and there must be a better way of getting the all-important cold air to the filter. It's currently set up like this, using the standard cut out at the side of the engine bay:

I have tried using the standard part coming from the side of the bay and connecting to that, but that left an unconnected pipe open to the hot engine air, and also didn't seem like the most direct route for the airflow. I also tried using some more piping connecting to the feed for the bottom part of the engine from the passenger fog, but that just seemed to make it louder, and possibly reduced the performance (it also seems like a long way for the air to travel to the filter).

Could it be that the metal piping is heating up the air as it flows through it?

Any ideas would be very helpful, cos i want to try to get the most out of this BMC, not just for the sound of it!

Thanks for reading my essay,

Ant

Ant_43 · Post by **Ant_43** » Thu Jun 15, 2006 1:36 pm

Hello again,

I know that the BMC CDA has been discussed a lot on here recently, but i just thought someone might have a definitive answer for the best place to route the intake piping?

Any ideas or suggestions?

Sorry to moan!

Ant

Prash · Post by **Prash** » Fri Jun 16, 2006 11:50 am

I don't think there's a definitive answer to placement of the air feed i'm afraid

Most of the gti owners have air conditioning which means you're not able to get a feed from the front of the grille very easily (the pipes get in the way). I also tried routing the piping to the front passenger foglight grille, but like you say the piping was too long !

In the end I removed all the original air feed piping that goes down into the driver side wing and fed some good size tubing into the space provided by the wing, for me this was actually the best place to have it. The temperature in that area was actually nice and cold most of the time and provided all the air needed (and the tubing length was quite short to the filter), and as long as the bmc isn't getting hot air then it'll be fine !

popeye · Post by **popeye** » Fri Jun 16, 2006 1:18 pm

Whats wrong with using the existing air feed pipe? seen a few of you do it that way on hear! i know that in the winter the inductions can have the opposite effect on the car and give problems coz the air going in is to cold! thats also why there is the other tube connecting to the main air flow pipe from the front of the engine the really small one. i know it also has other purposes aswell ut in the winter it does introduce a bit of heat back into the engine.

Ant_43 · Post by **Ant_43** » Fri Jun 16, 2006 1:26 pm

Hi,

Thanks for the reply mate. As you say, the gti engine is very cramped for space, so i agree there aren't many options for the feed.

I have routed it like you did, (check pic above), into the original place, seems to be allright, but still unsure if it's increased performance that much.

Do you know the effects of smaller or larger diameter tubing for the feed?
Also, i thought maybe rubber tubing would be better for thermal conduction reasons?

Cheers,

Ant

Prash · Post by **Prash** » Sat Jun 17, 2006 10:07 am

Ant_43 wrote:Hi,

Thanks for the reply mate. As you say, the gti engine is very cramped for space, so i agree there aren't many options for the feed.

I have routed it like you did, (check pic above), into the original place, seems to be allright, but still unsure if it's increased performance that much.

Do you know the effects of smaller or larger diameter tubing for the feed?
Also, i thought maybe rubber tubing would be better for thermal conduction reasons?

Cheers,

Ant

Hi Ant,
I'm not really sure of the specific effects of different diameter tubing but the stuff that comes with the bmc is I think 70mm, and I doubt you'll get a performance increase above that. I used a slightly bigger diameter tubing but most importantly it was double layered heat reflective tubing (for as you say reduced thermal conductivity), the inside is very smooth and keeps the air cool through the warm engine bay. Rubber tubing would probably be fine too !