Cold Air Intake

[bugger]

Hi Guys,

thinking of doing CAI for my car.

is it worth it?

how much and how much power gain in return???

Comments and suggestions welcome~

[WogsRus]

It's not just about power gain, it's about sheilding your pod from the hot inside engine bay temperatures.

Cooler air means denser air, more air to compress, more bang = more power.

But the main differance is the reduction in heat soak with a proper sheild and CAI.

BIT like this

http://www.skylinesaustralia.com/forums/in...9816&hl=CAI

[cosworth1971]

1-5 kw (depending)

[Nismo_God]

....if that....

[mad082]

....if that....

+1. that is what intercoolers are for.

[TTT]

Hi Guys,

thinking of doing CAI for my car.

is it worth it?

how much and how much power gain in return???

Comments and suggestions welcome~

assuming you have a pod filter right?

CAI will just make it the way it should be.

getting cool air instead of hot engine bay air.

If it's possible, you'd be better off putting the stock airbox on and using a Panel filter (even the stock paper nissan panel filter is not a restriction until way over 200rwkw)

[tacker]

i didnt notice any more power but i did feel like the heat soak was much reduced then when i ran without it.

[mad082]

if you are going to make one don't make it air tight other than a single feed as you will choke the engine at high rpm. i made one up for my 33 and it wasn't all that well sealed, but with the lid on it felt like it was struggling up top. when i took the lid off and let more air (even though it was hot) get to the filter it felt much stronger. it was just choking. yes i was getting cold air, but at high rpm the box was to restrictive and i'd say i probably lost top end power from it while the lid was on.

[cosworth1971]

on my xr8 and other cars i have ran a 3 inch flexi hose to front bumper facing the air (with stocking on it to stop leaves n stuff) then to std airfilter box with paper element for fine filtering....but i stay away from dirt roads and stuff with this

but havent done this to sky yet..

[mad082]

yeah i had that in my box, and i have a stup like that in the missus pulsar.

[djr81]

if you are going to make one don't make it air tight other than a single feed as you will choke the engine at high rpm. i made one up for my 33 and it wasn't all that well sealed, but with the lid on it felt like it was struggling up top. when i took the lid off and let more air (even though it was hot) get to the filter it felt much stronger. it was just choking. yes i was getting cold air, but at high rpm the box was to restrictive and i'd say i probably lost top end power from it while the lid was on.

For my 10 cents, if you are going to make one you may as well make it air tight.

A few points before I make my, errr, point.

1. Charles law. Put simply this says that temperature & volume (read density for our application) are inversely proportional. So a 30 degree increase in inlet temperatures will give you a 10% DECREASE in inlet charge density. This makes the turbo work harder which adds even more heat. Your intercooler can only remove some of this heat.

2. There is a compensating gain for air density that can be used. If you plumb your air intake into the high pressure area at the front of you can feed the cold air intake at above atmospheric pressure. Obviously this doesn't work on a dyno.

My point is simply this. You need to have a substantial constriction in the air feed to get anywhere near the losses incurred by sucking hot air. Calculated approximately a 100mm pipe, plumbed correctly, can adequately feed a 500+hp engine.

Lastly the worst effect of not having a cold air feed is when you are at the start line for a hillclimb or at the drags. The hot air will heat soak the intercooler which will give you less horsepower when you need it most.

[RBwhatever]

I put a partition in mine lastnight. Note its a partition and not a box. I made it for something to do. It didn't do anything for performance. I had the cold air feed already.

Fact is, if you have a cold air feed already you won't get heat soak while your moving. When your stationary yes you will, but not when your moving.

Try it sometime, go for a drive and pull over and feel the pod straight away. Is it hot? No it's quite cool actually, because of the cold air feed. Let it sit and idle for a minute with the bonnet down after a drive then feel the pod. Is it hot? Its quite warm actually....it must be heatsoak.

Unless you want "performance" when stationary on idle, don't worry about sealing the pod, although it is law in some states.

But by all means, if you don't have a cold air feed, then get one.

Partitions and pod boxes are overrated.

[mad082]

you will get heaksoak with or without a cai feed, as the act of compressing the air heats it up. i have been trying to find out what happens to the temp of air when it is compressed while the air is hot or cold but i can't find any info about it. it may be like water where hot water cools/freezes quicker than warm water.

if you have a good intercooler then it should be working well enough to compensate for any difference in intake temps.

[RBwhatever]

you will get heaksoak with or without a cai feed, as the act of compressing the air heats it up. i have been trying to find out what happens to the temp of air when it is compressed while the air is hot or cold but i can't find any info about it. it may be like water where hot water cools/freezes quicker than warm water.

if you have a good intercooler then it should be working well enough to compensate for any difference in intake temps.

I'm pretty sure when air is in the process of being compressed it heats up. Let compressed air sit for a bit and it will cool down. Its like friction.

[RBwhatever]

The theory goes too, if you can drop temperatures at the pod, the cooler the air will be after the intercooler.

[mad082]

The theory goes too, if you can drop temperatures at the pod, the cooler the air will be after the intercooler.

but if the temp going into the pod is 10 degrees higher i bet it won't be 10 degrees higher after the cooler. i bet it will be less than 10 degrees higher.

also, if you have a stock bov, it will be recirculating cooled air at idle, so that will keep your intake temps down and help with heatsoak. heatsoak is just caused by heat radiating from the engine and radiator into the intercooler

[djr81]

Have a look at the attached data log. It shows the difference between a cold day (quicker) & a hot day (Slower). You can clearly see at the 37 second mark that in third the rpm trace is falling away in part because the intercooler cannot cool the air as efficiently as on the cooler day. Yet the car keeps up in 2nd gear & when the cooler has a chance to dump some heat (ie when cornering)

This is despite a cold air feed & a good sized intercooler. Heat soak in your intercooler is real & something you need to try & avoid. Cold air feed to the pods helps avoid it.

[RBwhatever]

but if the temp going into the pod is 10 degrees higher i bet it won't be 10 degrees higher after the cooler. i bet it will be less than 10 degrees higher.

Yeah I agree with you there. It still has too many variables involved to figure out how many degrees less or more it will be though.

also, if you have a stock bov, it will be recirculating cooled air at idle, so that will keep your intake temps down and help with heatsoak. heatsoak is just caused by heat radiating from the engine and radiator into the intercooler

Aha. I was thinking about a different heat soak, heatsoak of the pod. Yes heatsoak of the intercooler can come off the radiator and from the engine heat when your staionary, but wouldn't most of it come from the turbo and the heat generated by compressed air?

If you feel the intercooler core after a drive, one side will be warm and the other will be cool. That heat can't of radiated off of the radiator onto the cooler as the car is moving so it must of come from the turbo.

Edited August 16, 2007 by KeyMaker

[mad082]

yeah, you will get heat coming from the turbo, and the longer you stay on the throttle the more you get. on a track with lots of straights and fewer corners you would notice it alot more than a tight track where you are on and off the throttle more often.

i will admit that on a racetrack you need all the help you can get, but for everyday street use there isn't much point

[RBwhatever]

yeah, you will get heat coming from the turbo, and the longer you stay on the throttle the more you get. on a track with lots of straights and fewer corners you would notice it alot more than a tight track where you are on and off the throttle more often.

i will admit that on a racetrack you need all the help you can get, but for everyday street use there isn't much point

Agreed.