If I made my own ghetto intake, would I get any real power?

[SaabJohan]

Of course we want cool air to the turbo, and if it's possible we want the air to have above atmospheric pressure. Some racecars have also used air cooling for the compressorhouse like this:

http://www.fastdetails.com/historic/...s/FmAturbo.jpg

[Bryan8412]

well its simple physics, i cant remember the law, but as volume decreases, the velocity of the particles increase, thus the temperature of the particles increases.

its pointless to waste time and power to cool the air, then compress it and make it hot again, then cool it again. thats why aftercoolers and intercoolers are used. Why don't they use those on n/a cars? no need, thats why they use a cold-air intake.

[Grendel]

Originally posted by Bryan8412
well its simple physics, i cant remember the law, but as volume decreases, the velocity of the particles increase, thus the temperature of the particles increases.

its pointless to waste time and power to cool the air, then compress it and make it hot again, then cool it again. thats why aftercoolers and intercoolers are used. Why don't they use those on n/a cars? no need, thats why they use a cold-air intake.

I can see what your saying, but listen to this for a min...

I'm just pulling numbers out of my ass here, but...

Say the air temp outside the car is 85 degrees, and the air temp under the hood is 95-100 or more...

Wouldn't having a pipe running to the front of the car sucking up that 85 degree air be a bit better than sucking in the hotter air from inside the engine compartment?

I know the turbo will make it hot again, but wouldn't the temp w/a cold air type intake be a *bit* cooler than the air sucked from the hot engine compartment?

It would make an interesting experiment... hook up some sensor to measure the temps of the air coming out of the turbo on the same car using each different intake system... *shrugs*

-Grendel

[Bryan8412]

well thats dependant on alot of factors, most importantly the psi of pressure the unit is compressing at. and im not sure what kind of power the CAI uses in it's function (in fact im not sure how it works at all), but i think the power used cooling the air isn't worth the possibility of slightly dense air before it hits the intercooler.

consider this analogy with a more tangable substance. if you took a glass of water at room temperature, then lowered its temperature 10 degrees in the freezer. now in an effort to purify the liquid, you heat it for a short period. however, it remains above room temp because it was previously cooled. now you want it back to 10 degrees below room temp so you cool it again. See the unnessicary step here? Sure it brought it slightly cooler after purification, but it takes longer to cool the water 10 degrees and compensate for the boiling then just cooling it 10 degrees. now in reality, you'd have to boil the water and thus the initial temp change was unnessicary, as would cooling before compression i can only imagine.

now i dont know if intercoolers or CAI's cool to a certain degree or just plain cool, but irregardless, running the air through 3 devices instead of 2 is just foolish. remember, simplicity is the king of reliability. the less that can go wrong the better.

[sciguyjim]

If I could add my .02 here. Sorry Bryan, your example isn't quite the same as Grendel's. I believe Grendel is correct, in fact I'm positive. Also, it's the same basic argument for having a normal cold air intake vs letting the open air filter under the hood suck in the hot air around the engine. I've never heard anyone say how much it helps, but everybody wants cooler air rather than warmer, even if they have to pipe it in from another location.

[Bryan8412]

your post suggests nothing that hasn't already been said. If you know this for a fact give me a link to where this is done. Did you even read my post? Why would you cool the air in hopes that SOME of temperature raised will remain afterwords to save on the intercooling process? It's complexes the setup more, and is completely useless.

Please, someone who can give me a substantial reason why this would be worthy of doing, or at least some numbers or a link, not someone who thinks they're right.

I may not be right, but before you assume its something give me more tangible proof thereof, instead of an opinion.

Texan? Enginerd? Ivymike?

[sciguyjim]

Originally posted by Bryan8412
Please, someone who can give me a substantial reason why this would be worthy of doing, or at least some numbers or a link, not someone who thinks they're right.

I may not be right, but before you assume its something give me more tangible proof thereof, instead of an opinion.

Texan? Enginerd? Ivymike?

For some more tangible proof, here is an example done with real atmospheric density numbers. The temp rise due to the turbo was simplified to just being 10°. The starting temps were a very likely 80° to 90° vs 70° to 78°. In the last sentence I used Grendel's temps of 85° vs 100°.


How about this analogy, take a container of air at room temp (say 80°) and pressure and compress it like the turbocharger does. The compression will cause the temp to go up, say 10° to 90° or (90-80)/80 = +12.5% (just using simple figures here). Now, take an identical setup and put it in the fridge to cool the air inside, say by 10° again to 70°. Now when it's compressed, because the air is starting out cooler, it will still rise in temp by 12.5% when compressed the same amount, but this rise is added onto the lower starting temp, so the final rise in temp is maybe only 70°*12.5%° = +8.75° to 78.75°. Thus, the compressed air is 90°-78.75°= 11.25° cooler than the original experiment and maybe about 3% denser (if my quick calcs were right). Then the intercooler cools it even more, and the degrees cooled is subtracted from the starting temp which is already 11.25° cooler than in the first example, so the air going into the cylinder is cooler than in the first example. Even though it'll be heated up again by the compression, it is once again starting out cooler and will end up cooler.

Using the original example by Grendel, the density of 100° air is roughly 1.1277 grams/liter. 85° air has a density of about 1.1649 gm/L, so the 15° cooler air is about 3% denser at 85° vs 100°.

How's that?

[SaabJohan]

The temperature rise depends on compressor effiency and pressure ratio over the compressor. The total temperature also depends on air inlet temperature.

Under the hood the temperature is high, therefor should you NEVER take the inlet air from there. Just take a look on serius racecars, you will not found a car with the inlet under the hood. If you do find such a car it's constructed by a moron (like many strretcars with open filters under the bonnet).

Lets say the ambient air temperature is 20 degrees celsius (68 F), the temperature under the hood is maybe 50 or 60 degrees C (122-140 F).

If we now use a turbocharger with the effiency of 75% compress the air to 1,5 bar (around 22 PSI). If the pressure before the compressor is normal the pressure ratio is 2,5, if it's lower the pressure ratio will be higher and if the pressure is higher the pressure ratio will be lower.
With an inlet temperature of 20 C the outlet temperature will be 135,7 C (226,3 F) and if the inlet temperature was 60 C the outlet temperature should have been 191,5 C (376,7 F). If you now take a look on theese numbers you will find that when the intake temperature rises the outlet temperature will rises even more.

So now to the intercoolers, we use and intercooler with the effiency of 75%, and remember that the ambient air temperature is 20 C.
With the intercooler the temperature will drop to 48,9 C (120 F) and 62,9 C (145 F). This means that the one with a cool air intake will have approx. 4,2% more power than the one taking inlet air from the engine compartment. The cooler air will also lower the combustion temperature which means less NOx and less stress on exhaustvalves, pipe and turbine. The engine will also be more knock resistant.

If we can pressurize the inlet air before the compressor we can run with lower pressure ratio and the spool up will be done faster. Lower pressure ratio means colder air in the compressor outlet and less power to compress the air, and this gives more power on the crankshaft. If the turbo runs on high pressure ratios where the compressor effiency is low the effiency can increase due to lower pressure ratio.

[Bryan8412]

Originally posted by sciguyjim
How's that?

Hmm. No links, no actual numbers, you used ones in the first which was useless, then proceeded to make up your own experiment of pure fabricated numbers (correct me if im wrong). I need a little better than your make-shift physics. Besides that, why add a CAI in addition to an intercooler, to cool it further, why not get a bigger intercooler? Simplicity rules, and none of my other Q's were answered either: does the CAI use power? does it slow the process at all?

If i was building a turbo charged super machine, I wouldn't waste the added complexity and maybe power for a CAI when the intercooler is supposed to be doing that. I'm sure you can sit there and cool the hell out of the air to absolute zero (yes i know it wouln't move im exagerating), but the power wasted to do so probably isn't made up by the increased density after a certain point.

[Jimbo_Jones]

bryan is right, cool air compressed can become EXTREMELY hot as the particles are not space apart but are collideing and rubbing with eachother... its really depends on the amount of pressure your turbo is running at, the higher the pressure the more useless your cold air intake becomes due to the air just getting hotter and hotter, although you may experience some of the benifits of having cold-air intake it wouldnt really be worth the trouble

if there was some way of letting the air that had been compressed to cool down you would have very noticible changes in hp, but this is not possible unless you have some kind of storage tank in your car which is not gonna happen because its basically not practicle...

cold air intakes should be left to non-forced induction cars like normal diesal engines were it would kick ass, as diesal mostly rely on the air having a high expansion index as the compression levels are very very high

if you really want the formula for calculating temp. rise under compression post back and i'll get 'em for ya

[sciguyjim]

Bryan, I give up. I've tried to explain using simple examples that you should have been able to follow but you continue to complain about insignificant things. It's not possible to argue with someone who won't follow the argument. I did my best using as many true numbers I could find, that's all I can do.

SaabJohan gave an example using better numbers, argue with him next.

(sorry to dump him on you SaabJohan, but he won't listen to me.)

Is there anyone else out there who can explain this better? Why don't we take a vote for who's more correct and see who wins that way?

Jimbo, I know compressing the air makes it hot. The point is compressing hot air makes the result hotter than if you compressed cold air. The cold air is free for the taking, I'm not doing any work to get it.

[SaabJohan]

Bryan8412 and Jimbo_Jones, have you read my post at all? Read it and maybe you will learn something.

Take a look on this intake
http://www.mulsannescorner.com/Audi-PM1.jpg
it's from the Audi R8. It have two intakes, one for each turbo, the intake is sized for around 300 hp and the use of a FIA restrictor (according to the regulations). The intakes feed the two Garrett turbos with cool air.

[ivymike1031]

Originally posted by Jimbo_Jones
if there was some way of letting the air that had been compressed to cool down you would have very noticible changes in hp, but this is not possible unless you have some kind of storage tank in your carp which is not gonna happen because its basically not practicle...

either that or an intercooler, right?

[sciguyjim]

Please look over the recent previous posts. We'd like to hear your comments. Is anybody right? Or, have we got our facts mixed up somehow. We'd really like your opinion on the above discussion about using hot air vs cold for a turbo intake and which would be better (result in more horsepower.) Waiting eagerly for your opinion. Jim.

[Bryan8412]

sciguyjim nothing against you at all, but i'm just curious why you think so and specific real life examples is what i need is all.

Originally posted by SaabJohan
Bryan8412 and Jimbo_Jones, have you read my post at all? Read it and maybe you will learn something.

Take a look on this intake
http://www.mulsannescorner.com/Audi-PM1.jpg
it's from the Audi R8. It have two intakes, one for each turbo, the intake is sized for around 300 hp and the use of a FIA restrictor (according to the regulations). The intakes feed the two Garrett turbos with cool air.

sorry i didn't notice your post, but thanks for the substantial example (the audi). so are you saying that taking in hot air and making it even hotter is dangerous? i see the logic there, but thats probably an issue only with high boost cars (like the quad-turbo 2000hp car in PHR mag) or a dual turbo such as the R8, not grendals car. But if the intercooler cools if farther as you say, why not have a bigger intercooler, or have the intercooler cool it longer? but thats dependant on my other questions that i wish someone knew: does a CAI take horsepower? and does it take "time" and slow the process a la a muffler?

is this the intake?: http://www.adrenalinmotorsport.com/s...bmc_carbon.asp

i tryed looking up about it but couldn't find much, can you link me where it says its cold air? thanks