Ram air intake (first power mod)
 

http://img47.imageshack.us/img47/9701/dsc08666pi4.jpg

Bought the kit off of eBay. It took a little ingenuity and a radiator hose from a '65 Mustang, but everything works great and it feels like I've gained a good amount of low-end torque, plus the turbo spools faster now. :icon_tup:

Plus it looks great- and it was worth the price (twenty bucks!) just so I don't have to say I'm running stock anymore. :rlaugh:

-Tetsu

not exactly "ram air" but its a nice TID

Yeah, true. For some reason I've just grown accustomed to calling it that.

cut a hole in the hood then you can call it a ram air =D

Build a cold air box around that filter, otherwise you're just sucking in hot engine bay air and making less power. :)

nice, I did the same thing on mine a while back. Now I have the cone under the passanger side head light so it sucks fresh air instead of the hot engine bay air.

I cut the a hole and took of the windshield fluid bottle if you are wondering how I did it.

i'd like to do this mod, but i like my wiper fulid ;) where do you move it to?

up in the bay, probably back by there the cold start and cruise control would be if ya take them out, or up in front of the radiator in that well

Yah know..this is true on NA's, but with the boost increase on a turbo, I'd say thats completely false :-O


Now, if the wastegate is ported, than yeah, your right :-P

But you would definately get more power with a cai.

And I'd say your wrong. the turbo adds heat as the air as it's compressed, this is true. however, if you start with a lower intake temp your still going to get a lower output temp and thus more power. Also, porting the wastegate will not lower intake temps either. the Turbocharger is still adding the same amount of energy (heat) to the air weather is't ported or not. It will keep you from overboosting tho.

Yep, creating a Cold air box for the TID would be another step in reducing the chances of detonation. That combined with an efficient intercooler would go a long way.

Heat Kills Apex Seals

The End

Any suggestions on fabricating a cold air box? I didn't remove the duct that supplies air to the stock box, so there's still that outside air blowing directly onto it.

Do we have to go through this again? Everytime we have one of these threads, someone says something like that...

ANY time you introduce more heat into the intake, you will make less power because your air is less dense. In a turbo system, it's even more important to get cold air in there because the turbo heats it up so much and the intercooler must remove as much of that heat as possible. Hotter air into the turbo means hotter air into the intercooler which means hotter air out of the intercooler.

i would think the turbo would do most of the raming... :uhh:

is there any effiecient way to make an intake WITHOUT removing the washer bottle?

^^Still wondering...

Yes

But wait wait! Most people see a 2psi or so increase from a 3" TID. So...80* air, 7psi...versus 140* air, 9psi...the 7psi would make more power? :-O This might make me rethink my turbo's TID plans!

Actually, compressing air magnifies the intake temperature, so a CAI is even more important in a turbo. Though a good enough intercooler could theoretically do 100% of the cooling. Any intake that let's in outside air and completely seals the air under the hood from the intake should make a good CAI. There are pics of some very nice looking CAI's if you search.

Estimating Power Increase From Pressure and Temperature
density ~ P / T
T2 = T1 x (P2/P1)^0.286

Where P is absolute pressure (gauge pressure + 14.7psi) and T is absolute temperature (rankin = fahrenheit + 459.67).

So if I have 10psi of boost and I intake 100F air from under the hood:
T2 = 559.67R x (24.7psi / 14.7psi)^0.286 = 649R = 190F
density2 / density1 = (24.7psi / 649R) / (14.7psi / 559.67R) = 1.45, i.e. a 45% increase in air (and horsepower) versus N/A, minus whatever the turbo consumes

Or if I use an intercooler to cool this back down to 100F:
density2 / density1 = (24.7psi / 559.67R) / (14.7psi / 559.67R) = 1.68, i.e., a 68% increase

Or if I have a CAI drawing in air at 80F:
T2 = 539.67R x (24.7psi / 14.7psi)^0.286 = 626R = 166F
density2 / density1 = (24.7psi / 626R) / (14.7psi / 559.67R) = 1.50, i.e., a 50% increase
Compared to a N/A with a CAI (T1 = 539.67) the increase is 45% like before.

Cooling the air down to 100F yields a 68% increase as before, but it is much easier to cool from 166F to 100F than it is to cool from 190F to 100F; in the 2nd case the intercooler must be larger or the air will be hotter than 100F. And dumping 80F air over the intercooler is much better than 100F air: 100F air will never quite get the intercooler down to 100F, it might be 110F or 120F instead.



These same equations may be used to determine the gains from a CAI in a N/A, or from driving on a cold day:
80F air provides 559.67/539.67 = 1.037 times as much power as 100F air, i.e. a 3.7% increase (5HP for a stock S4, 6HP for a stock S5, 7HP for a stock turbo).
-10F air provides 559.67/449.67 = 1.24 times as much power as 100F air, i.e. a 24% increase (36HP for a stock S4, 39HP for a stock S5, 44/48HP for a stock S4/S5 turbo). Time to go driving in Colorado.

Absolute zero is 0R or -459.67F. The temperature in deep space is about 5.5R or -454F. The pressure in a perfect vacuum is 0psi absolute or -14.7psi gauge.

80F, 7psi: T2 = 539.67R x (21.7psi / 14.7psi)^0.286 = 603R = 144F
140F, 9psi: T2 = 679.67R x (23.7psi / 14.7psi)^0.286 = 779R = 319F

I can only guess what the temps will be after the intercooler. But you can imagine an intercooler designed for the 1st case won't do much in the 2nd case. Let's assume 95F and 140F after the intercooler (75% of the heat dumped into 80F air).

(23.7psi / 600R) / (21.7psi / 555R) = 1.01
9psi & 140F is 1% better than 7psi & 80F.

With no intercooler:
(23.7psi / 779R) / (21.7psi / 604R) = 0.85
9psi & 80F is 15% worse than 7psi & 80F.

So if you have a good intercooler it's slightly better to intake 9psi & 140F; if you have a bad intercooler it's better to intake 7psi & 80F. If it's a better intercooler giving you 9psi then no, power won't decrease. The reason you get +2psi is because the air is cooler so it's easier to compress. The air won't get hotter because it's cooler. That's silly. That's like saying: "If I take the easy road I will travel faster. But if I travel faster it will be harder. Therefore it will be easier to take the hard road."