Re Airbox and Cupra TDi intakes and CAI kits

Ok,

Now before i start, i have no proof of this, no airflow figures to back it up, and no scientific explanations, but this is what i have noticed on my 1.8T with regard tot he above.


Ok here goes.

I have now had 2 Dyna twist filters on my car, first off i tried the Small dynatwist on the car as per Bunnin's one. i liked it and yes it did make a nice dump valvey noise and is worthwhile, but performance wise i did not see any real changes, a bit more of a growl, but no real huge benefits.

I also found it worked better when it was used as a non-enclosed filter.

I then decided to sell this on, and change to an XL - Dynatwist filter. this was experimental as i wante to try more Air going into the car. Now for obvious reasons ( size of the unit) it was not possible to run this as a closed air intake system. So i dumped the cover and the ductig hose and ran it open filter.

It worked well, the noise was a lot more, especially from the DV, it did make a very loud satisfying whoosh noise. However it ended up making the car feel beter than the small dynatwist, but there was something different. it seemed to hesitate slightly, almost as if it was getting too much air in. The only way i can describe it is, try sucking o a straw, the air goes in at a higher pressure due to overall suck on small surface area. However now suck on a toilet roll and ther is less pressure as greater surface area and you almost take in to much and choke. Now this is what i feel the car felt like. So it bogged down on take up of drive then pulled hard.

So both were ok, the first being better.

However i have been having a tidy up on the car, and trying to get rid of the no standard look. So i wondered what could be done to the standard air box, as i kept it all. After reading James' posts on smoothed airboxes and a few othe rpeople who have done it, i decided to dsee how i could improve the standard intake system.

So on Saturday i decided to have a play. Got the dremel and got to work on the box. I smoothed completly the top part, this took a while, nearly an hour to get the finish i wanted, as on the tp side there is just all honey combe. I also took off the Trumpet the goes into the MAF connection. again this was restrictive so it came off. The bottom half of the Airbox i left as there was no real area that needed to be smoothed off on it.

i then looked at the cold air feed. now i know everyone changes to the cupra TDi on the diesels. But i though long and hard about this, as the hole into the box end does not increase in size, its just the cold air end that increase, so in effect it is like a funnel. Now in my logic, surely to get more air flow you need to increase the whole pipes diameter, not justone half of it. I mean picture, this , suck on a straw, now suck on it again with a cone at the other end,you don't get any extra air into your mouth do you, no.

So i decided i needed to mod the actually existing air intake, which is rather bad in desig, take it off and you can not see all the way through, there is a sort of flap in the way. So first job was to cut this out and smooth it all off. also this air intake sits directly above the radiator ( nice design) and half the air intake is exposed to the radiator, so you end up sucking air from this as well. So i blocked off the part that takes air from the radiator, i then refitted the new modded intake end and popped in a new paper air filter.

and went for a drive, now first thing i noticed was wow, it picked up so much better, it was instantly on boost with no lag and no noise when changing gear. the whoosh was gone ( thank god i was starting to have had enough of it) and the car picked up smoother and much better. I then took it to southend and the car behaved like never before,

All i put it down to is that the air bx is of good designe and the pressures in the box act as an aid t getting better air flow. The car sounds more refined and the turbo is agfain more noticable. so i was dead chuffed with the results, and now thinking on changing the paper filter for a green panel filter. Might try this at the weekend.

But i think this is a mod all can do, for just some time and effort and it looks no differnet to the original equipment so looks nice and neat. It seems to be worth it, but would have been nice to air flow test all 4 options i had.

so get your dremmel, and also mod that air intake as i think with that modded you will not need a cupra tdi one. dunno let me know.

Also i was going to consider cutting out the grills from the MAF sensor a ssurely this is slightly restrictive.

any thoughts all. i can post pics up next week.

jason leese said:

I wouldn't cut the grills out as the MAF is really delicate and I would think the grills are to protect it .
But what you are discribing is a good advert for "less is more" it might make slightly less power but the drive is better due to the delivery.
But the flap that you cut out is there to create disturbance in the airflow so larger particles of dust don't get in to the filter they sort of drop out of the air flow.
Also I wouldn't put too much into the intake being over the radiator because as soon as the air gets compressed in the turbo the temprature will rocket . the bit after the turbo is more important than the bit before.

Click to expand...

I think you may be right, it may not mak so much on the rolers, but by christ it is a nicer drive now, I also took the Strut brace off too, so there i s alot less harshness on it, i may kepe the strut brace to use for track days, but normal everyday use keep it off.

PS this was all my own opinion, but might be worth trying if you are bored one weekend.