Air Intakes

[Julian Edgar]

Interesting... Can you link something so I can see the testing done? I'm not familiar with the TDI's, but i dont remember well the water test or how it relates to actual power curve or efficiency for the engine.

"Inches of water" is just another another way of expresisng the pressure drop, ie the restriction. It doesn't matter what sort of engine is on the other end, except for the total airflow. Browser Warning (for which I write) has done many tests showing how to measure intake restriction. The testing is extremely accurate and can be done for basically nothing. The Roomster intake will be covered in AutoSpeed in 2011. An example of such testing is Browser Warning

I want to try things that many people wouldn't bother with without spending big cash.

That's almost the perfect definition of a DIY intake!

[sssstew]

the PD160 intake is as big as you can get into the gap on the GTI, its a very very tight fit, so doing the home made mod wont give you any bigger diameter as the PD160 is at max for that location anyway. And the simple remove old and plug in new pipe is so simple that its this appeal to most people who want to upgrade it. Oh and cutting out the flap in the adapter which fits to the front panel.

[Julian Edgar]

the PD160 intake is as big as you can get into the gap on the GTI

Well, I don't agree! The width is constrained in a few places but the height is not. On the Roomster I used 80mm plastic pipe and shaped it in those few places to clear obstructions. Looking under the bonnet of my GTi, I'd be pretty confident I could do the same thing - the airbox and air pick-up points are identical, and the other dimensions very similar.

I agree that the PD160 intake is quick and easy, but if you want to achieve better flow* at a lower cost, I think DIY is certainly worth considering.

* = larger duct cross-sectional area, smooth inner walls, larger entrance to the airbox

[Julian Edgar]

Can you really generate a ram air effect travelling around on "normal" roads ?

I was under the impression you needed to be doing a very fast speed - ram air works for jet engines - it is the same with most aero kits ... they look good but you aren't going to get any noticeable benefit driving at 110km/h on a freeway.

Hoping someone who's played with this stuff has some definitive answers and not more speculation as I'm skeptical about any benefit trying to "ram" air into the inlet ... you may get a benefit from colder air (not drawn from engine bay) but I just doubt you have the speed to generate an air mass great enough to create a ram effect.

It's not hard in a non-diesel to generate sufficient intake pressure that at highway speeds the pressure drop across the air filter is entirely cancelled (ie generate ahead of the air filter 1 inch of water pressure, which is about the pressure drop across most good air filters). In a diesel it's harder because they use so much air, even at low loads.

[ellie]

Hey guys, I have used Julians method (Soft drink bottle/broom stick and water) for many years ever since I bought 21st century performance and read practically ever page of Autospeed since. I've made several straight forward custom intakes to the airbox on different cars with testing. I could not tell you the amount of times someone had told me catagorically that I should have put a pod in until I challenged a guy with the same R32 on a dyno with only my intake and exhaust (which was way to quiet with too bigger mufflers to make any power according to them also). With his pod and 3.5" straight through, I made more power everywhere, with 17 more horse power than him at the peak with the gap growing with every run as he started inhaling more and more hot air.
My point is = don't get so single minded and trapped up inside your VAG box without any testing past bigger must be better. I personally bought the PD160 intake because it is a darn site better than the stock with a factory finish. But julian is right also in it not being optimal and It's great that he is sharing what he has found with us.
All these questions have been covered, not only by him with tests to confirm or discredit the theories many times. I surprised how many people are asking questions of him when they were giving advice earlier in the thread.

Julian, I have a TDi myself, so you'll have to fast track your findings with the roomster to auto speed. Have you been mucking around with any thing else on the 1.9 diesel to look forward to?

[vwthunder]

How would a BMC CDA or something along those lines go
I see Guy had one on his Polo Gti

[Julian Edgar]

I have a TDi myself, so you'll have to fast track your findings with the roomster to auto speed. Have you been mucking around with any thing else on the 1.9 diesel to look forward to?

intake, exhaust, reflash, intercooler - and now need another reflash... intercooler is so much better than std.

[ellie]

intake, exhaust, reflash, intercooler - and now need another reflash... intercooler is so much better than std.

Mustard has nothing on how keen I am to read these! Seeing as VW warranty isn't worth the paper it is printed on, I'll most likely go down this route. Any heads up on when you'll have them out?

[Julian Edgar]

At this stage the series starts Jan 25 and goes for six parts. Note it is specific to the 1.9 TDI. I am very pleased with the results, with one more modification step yet to occur.

[noone]

My point is = don't get so single minded and trapped up inside your VAG box without any testing past bigger must be better. I personally bought the PD160 intake because it is a darn site better than the stock with a factory finish. But julian is right also in it not being optimal and It's great that he is sharing what he has found with us.
All these questions have been covered, not only by him with tests to confirm or discredit the theories many times. I surprised how many people are asking questions of him when they were giving advice earlier in the thread.

Have you read the pressure testing done on the Polo GTI? its in one of the intake threads. Same story as most VAG Cars, restrictive MAF, filter is fine, intake pipe is restrictive and the box is somewhat restrictive.

I've read a lot of the Autospeed guides, very handy for me as this is the first car I've tinkered with.