Air Filter
Turbo Mini Forums

I have been pondering on best positions for my air filter

my latest position is cable tied to the alternator

I find that the alternators fan, and the radiator fan help draw plenty of cold air around the filter
Anyone else tried this ?

S

TurboLessTosser

The ONLY place for an air filter in a turbo is at the front, or anywhere it draws in air that is cool.

For typical figures - say ambient air is 18 degrees, and that with 1 bar of boost, the air leaving the turbo is at 100 degrees, it can be seen that you are heating the air to 550% of what it entered the compressor at.

Now fit your air filter at the back of the engine, behind the rad and near the heat of the turbo.
Now suppose that the air temp measured at the mouth of the entry to the turbo is 25 degrees compared to the 18 degrees seen if it was positioned the front of the car.
25 degrees * 550%/100 = 137.5 degrees leaving the turbocharger - so that's 38 degrees (or 38 % in this example) just for a 7 degree change in the intake temp...

Moral:
Stick the air filter at the front, nowhere near the radiator or other heat source!

I don't think that's quite right Dave.

If you compress air by a certain amount you give it a certain amount of energy (i.e. heat).

So, say ambiant temp was 20 deg and you compressed this to 1 bar and it's temp rose to 100 deg. If then the ambiant temp was 25 deg then the compressed temp would be 105deg.

Well that's how I understand it.

Either way, put the airfilter where it can get as much cold air as possible, as you say.

Wil

Fastest 998 mini in the world? 13.05 1/4 mile 106mph

Interesting information and totally new to me as this is my first turbo

I have cut two holes in the fron of the bonnet directly in front of the filter ;

the air flow would then be through those holes, and the grill

Straight over the filter and alternator through the rad and out the wing

My rekoning was it was a pretty good pos. so I can use the other side for my intercooler ?

I notice some people have them at the back og the engine bay near the wiper motor, surely that has to be even worse then Dave ?

Steve

TurboLessTosser

yeah it can be worse, i mounted one here for a std setup as i didnt have the space or pipe to move it anywhere else!
This time ill try to get it near the front, helped by the lack of oil cooler and intercooler on my std-ish setup.

just need some hose!!

Not so sure will -

As air temp rises, so the space between the air molecules increases. Hence why if you had a sealed vessel of air at zero psi, then heated it, the pressure inside the vessel would increase. The number of molecules is still the same, it's just they are trying to move further apart, and as they cant, they generate a pressure.
If you wanted to keep the same pressure in the vessel, you would have to increase its volume.... hence it takes up more space - or to put it another way, in the original volume, there are fewer air molecules present.

Compressing the air remains the same, as the turbo compresses volume, irrespective of the molecular number within that volume...

It all depends on the thernal co-efficient of expansion of air, which is pretty low admittedly, but it's all in there!

hmm, but if there are fewer air molewcules present, will the volume heat up by the same percentage...
Right that's it - i've confused myself!

Yes - air filter at the front! LOL!

yes - air filter at front! is the only bit of that i understood.lol

Everyone knows that instructions only have to be read if the thing doesn't work....

The equation for pressure change in a fixed volume against temperature change is

P1/T1=P2/T2 So that makes you right I think, in a way.

This equation only works for absolute temperature. basically if the asmospheric temp rises by 5deg (from 20 to 25) the pressurised air will be 7.5 deg hotter.

More studying needed to understand this I think. Especially as the volume dosen't stay the same.

Wil

Edited by wil_h on 11th Jun, 2004.

Fastest 998 mini in the world? 13.05 1/4 mile 106mph

"So what your really trying to say is ........ put filter at the front away from heat source of turbo and radiator ?"

I think so ...... lol

WWW.TURBO-MINI.COM

TurboLessTosser

It is simple..Air density muliplied by the force of latitude is equal the barometric pressure(northern hemesphere only) divided by sustained positive boost over ambient temperature..thus proving the coefficient thermodynamics of the required pre plenum inlet charge are within tollerences of the hydrosystematic efficient parameters laid out by the university of hydrothermostatic studies of Ipswich.

In laymans term pick up cold air into your filter..the front maybe?

All i was trying to say was

is it ok to cable tie it to the alternator as I wanna put my intercooler in front of my brake servo

TurboLessTosser

you ideally want to duct air to it... and also to the intercooler...

only cold air into the air filter... not engine bay heat or intercooler heat

alex

AlexF

B12..yes.

But at the front the filter gets dirty!!!!

Can i just mention to people, dont buy halfrauds silver air pipe things, they dont reach the front and are a rip at 6 quid.

Previous Engine: 1040cc Morespeed engine, 1275 turbo head T2 Turbo Mirage Manifolds Megajolt
Previous engine: STD metro turbo, megajolt
Drives: 399bananahp (flywheel) Honda Civic Vtec b18c4 T28 Turbo 1968 Mini

Megajolt maps to download: http://www.jamesfawcett.co.uk/cms/index.ph...&gid=3&Itemid=3

thanx guys
TurboDave and Wil_h you have made me go cross eyed !!!

AGaIn !!!!!!!!!

TurboLessTosser

Shurley the pipes arent a rip off at ?6??? avonbars is ?40!

what diameter is the pipe??? what airfilters are you using?? ive completely forgot about these things!!

Sooperdooperturbocooperexpertengineering!

ah its only flimsy tin foil stuff though not good stuff. Im using a bolt on K&N air filter i bought off a boy racer just after i saw him write off his new style corsa into the side of a caravan! gave him 15 quid for it!

Previous Engine: 1040cc Morespeed engine, 1275 turbo head T2 Turbo Mirage Manifolds Megajolt
Previous engine: STD metro turbo, megajolt
Drives: 399bananahp (flywheel) Honda Civic Vtec b18c4 T28 Turbo 1968 Mini

Megajolt maps to download: http://www.jamesfawcett.co.uk/cms/index.ph...&gid=3&Itemid=3

http://groups.msn.com/turbominis/shoebox.m...hoto&PhotoID=15

Use the real pipe, its much more sturdy than the flimsy tin things i used to use to get air to my turbo

theres got to be a decent 'cheap' version somewhere!

Sooperdooperturbocooperexpertengineering!

stainless pipe and silicon hoses will last a lifetime, just got to sort out a good shape for your engine bay, shouldnt be any more than the avonbar type stuff but will be 100times better.

i bought my turbo motor on its own already out of metro, not the best scenario i know as i couldnt see it running.
there is no air pipe with the motor where do i connect it ? straight to the turbo ? i mean just push the pipe on to it then zip tie it in place lol
please i hope im not sounding like a numpty here lol