thoughts on cold air and turbos

[jdmawd]

feel very strongly about this idea, and i will leave my opinion out on this idea until later in the thread. some things are knows facts. cooler air is denser thus more air can occupy the same space, which is the whole idea of forced induction correct? next air compression generates heat that's why intercooling is important correct? now since the air compression generates heat, is the pre turbo temperature important. to the intercoolers ability, to cool the charged air down to a more operable temperature. To be ingested by the motor? or in other words will the intake air temp be lower pre intercooler if the air temp is cooler or will the compression by the turbo increase the temp to a consistent temp regardless of the temp coming into the turbo.

PS: part of my new setup will include an intake temp gauge vpc and buschur cold air pipe. I am very anxious, to see if air temps will be cooler with the cold air pipe as opposed to an under hood filter and stock mass air

 

[greyforestgst]

i can honestly say it does

i have a heat shield / cold air duct set up for my k&n filter, and the before & after was a noticable change. I just have a 5" wide french drain flexible tube running to my old intercooler hole on the fascia 90 degrees up right below my filter. then, i rigged a sheetmetal box that encloses the filter. although i haven't recorded intake temperature, or anything like that, i'd say i've netted a 5hp gain. it makes up for having my ac on, if nothing else.

my next step will be co2 intercooler spraying, but thats on hold while i nab me a turbo

 

[jdmawd]

greyforestgst:

Great review, that's the input I was looking for. If anyone else can add it would be greatly appreciated. IM going to do some runs once my setup is done, one with engine bay air, and the other with outside air.

 

[Mitsu_Racing]

GreyforestGST

 

[Mitsu_Racing]

GreyforestGST: you have any pics?

 

[larryd]

im planning on doing this same exact thing soon

 

[dsmtrance]

I have also done a CAI mod to my 91. I too noticed a difference. How much HP gain? Not really sure. But I started reading up to 45 degrees difference on the logger. Stopped my temps can climb to 130+deg. Once moving though my temps are always within 10 or so degrees of OAT. Not to mention my knock counts went DOWN when at WOT. I wholeheartedly believe in CAI's. Once I receive my IRC IC Kit (hopefully it'll be ready to ship in the next couple weeks!) I am going to be saving for a VPC. And once I get it I too will be purchasing the Buschur CAI that JDMAWD mentioned.

 

[TurboSpyder98]

thats exactly what i was wanting to do when i upgrade to a fmic.. i mean that hole has to be used for something.. right? question is.. exactly what type of pipe did you use? can you take any pics and post them up? im interested in your box design as well.. is it something easy to make? how thick of sheetmetal... and finally.. how bout a vfaq??

 

[crankbender]

Now that you have some real world data (and I am back on the comp from vacation) I will give you some of the theory on why this is the case. First off how hard the turbo has to work, IE speed and efficiency, is based partly on how dense the air is before it hits the turbo. This is to say that if you double the density of the air at the turbo intake you will basically double the output pressure at the same speed (if you are running 30 psig at atmospheric intake pressure and you are somehow able to get 14 psig before the turbo you will get 60psig after it). This of course doesn't take into account losses. This is why high pressure compressors are done in steps (shop air etc). Now that means the turbo doesn't have to work as hard so it has less mechanical loss and transfers less heat to the air when it compresses it. On top of that any heat carried to the intake of the turbo will be there after the turbo. compressing the air adds a base ammount of heat using the equation

p1v1/t1=p2v2/t2

increasing temp one without changing the pressures or volumes of the equation will demand that you increase t2.

now that isn't exactly how it will work because you will have some changes in pressures and volumes but it shows that the temps are related.

 

[jdmawd]

OK (trying to convert your post back into English ) i gather from your post, that the lower the intake temperature. the less heat is generated when the air is compressed by the turbo. is this to say that the intercooler will not cool the charged air lower than the temperature at the intake? if this is true then cold air would be even more important than previously thought. in total it is optimal to have an intake system that collects air at the coolest place possible before it reaches the turbo?

also where would be the best place, to tap for a intake temp gauge?

 

[crankbender]

The intake temp has no effect on how cold the IC can cool the air (other than a higher intake temp will give the IC higher temp air). Yes it is very very important to pull the air from the coolest point possible. Not only will this give you less heat going into the turbo but the turbo will be working less adding less heat. In effect hot air is a double wammy, hotter (bad) and thinner (turbo works harder also bad).

 

[Bohrn]

as we all have stated, colder is better when we are talking about intake charges, so anything you can do to improve that will help. those with dataloggers and intake temp guages will tell you how much.

As for where to plumb in the temp guage, I vote for the intake manifold, preferably in the middle. This location will give us the most realistic temp reading as putting it in other places could result in false warms and colds. eg, put the probe before the intercooler and it would be too warm(good for diagnosis and before and afters tho). Or put it on the upper ic pipe and it might read too hot as it is over the engine. Whereas in the intake manifold, you will have the tempurature of the main air charge JUST before it hits the intake valves.

just my 2cents, but it seems logical

 

[crankbender]

That would be the best place...but I would put it as close to the TB as possible instead of in the middle. Dataloggers measure the temp before the turbo...they are not a very good diagnostic tool for intake temps unless you are testing out a cold air intake setup.

 

[jdmawd]

hey guy's i want to say thanks to crankbender,and everyone who responded for giving an educated justification for why cold air is better. i always felt cold air was better. however i never REALLY new the science behind why cold air is better. i have posted this question in the past at other dsm sites, and im sure you now what kind of answers i got. thanks again for FINALLY clearing this Up.

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[crankbender]

BTW pressure is just as important because of the thinner air at lower pressures the turbo will have a harder time getting a good bite. This is why you would love to have a ram air on a turbo and run below sea level.


Now if we could only figure out how to get cold pressurized air to the turbo we would be fat with honda kills (not that that is a problem now).

 

[Boosted97GS-T]

Originally posted by crankbender
This is why you would love to have a ram air on a turbo and run below sea level.

hey i live like a foot below sea level , humidity blows chunks though and also it was 95 degrees last week

 

[crankbender]

You live just a hop-skip-jump away from me. houston here and I have to agree with the humidity and hot temps sucking. That is why I will be custom designing a cold ram air intake for my car. I donno if I can make it work for sure but I can try my damdest. I don't expect the ram air to make a huge difference but even a little help getting the air through the filter into the turbo is worth it.