idea for a CAI

me and my buddy was talking in school the other day about CAI, i had the idea to run a hose from the a/c unit to the intake, any one ever try this??? if so does it work good or should i not do it. open for advise

Not sure exactly what you mean. Are you saying that you want to run A/C cooled air from the cabin back into the engine?

haah! I like the sound of this!

LARRY70GS wrote:

Not sure exactly what you mean. Are you saying that you want to run A/C cooled air from the cabin back into the engine?

I think that's what he's talking about. Very interesting indeed.

ghpcnm wrote:

LARRY70GS wrote:

Not sure exactly what you mean. Are you saying that you want to run A/C cooled air from the cabin back into the engine?

I think that's what he's talking about. Very interesting indeed.

The blower motor could never keep up with the CFM demand of the engine. How would you plumb it to begin with?

i havent exactly made a plan, just the idea of it sounds like it could help run cold air to the intake, but i dont know alot about cars yet, im just getting started. why i opened a topic to see if we/yall could come up with a way of making it work. sounds possible.

Nitrous is colder than AC

An idea would be to find a small evaporator to plum up to the ac lines and put it in place where you would mount an inter cooler under the supercharger in theory you should be able to keep all air going in to the motor at below 50 degrees

crstump should get together with coryel.I'm sure they would come up with something.....

weird. I just had the same idea Friday. I was going out for lunch at work and my AC was on auto and it kicked on immediately and cooled the cabin nearly instantly. I thought, "Why couldn't I redirect this to to the engine bay and to my intake?

No one has ever done this? It seems like a pretty straight forward modification. With these Ohio summers though Im not sure I would sacrifice my AC for HP....

charlieRobinson wrote:

weird. I just had the same idea Friday. I was going out for lunch at work and my AC was on auto and it kicked on immediately and cooled the cabin nearly instantly. I thought, "Why couldn't I redirect this to to the engine bay and to my intake?

No one has ever done this? It seems like a pretty straight forward modification. With these Ohio summers though Im not sure I would sacrifice my AC for HP....

Charlie,
See my last post.

With my idea you wouldnt be sacrificeing ac in side the car you would be adding another evaporater core in the ac system. It would be like the vans with a rear ac unit and a front all off of one compressor napa in my area has the ability to make custom ac lines so very probable idea.

This is an interesting video that has to do with CAI

Remember, believe only half of what you see, and none of what you hear.

It's a good test, but it actually shows how important intake air temps are to performance, not that they don't work. The tests were controlled, but there were some flaws in their modifications, and choice of vehicle used. I wouldn't agree that cold air intakes don't work, or aren't worth adding to your mod list. If you consider some details of their test, like the car they used, it paints an entirely different picture.

For starters, the OEM intake on that car is actually a CAI design from the factory, and likely a pretty good one. Not all cars have such a good system, so they were starting with the bar pretty high.

Notice how they measured no power gain when they ran the intake without any filter. What this means: because the rest of the stock intake design is rather well designed, the engine is getting all the air it needs, and is not limited on the intake side. It's probably limited more either by exhaust or engine breathing restrictions. Basically, they picked a car that cannot benefit from increased intake air, unless the engine or exhaust is also modified for the extra flow. Not all cars are this way. In fact, I'd say MOST cars ARE intake limited to some degree.

Also note their "CAI" designs were actually reading 15ºF or more above ambient temps. That makes them "warm air" intakes, which we all know can hurt performance. Only when you snake the intake outside the engine bay do you see a real difference - this is because intake temps match ambient exactly.

Here is why a FWI works so well. It's exactly like having a tube snaked outside the bay. How do we know? Because we can look at IAT and see that it matches ambient, and know that that's as good as it gets. You don't have to do as these guys did - making a ridiculous snorkel to see gains - you just have to know how to design a proper intake. On our cars, properly shielded FWI is one tried and true way to keep IAT at ambient.

Another issue that they conveniently failed to mention: the car in their test was turbo & intercooled, so the air charge is being re-cooled after compression by the turbo. That means they're not getting any KR, no matter how high the intake temps are. In contrast, our cars are not IC, so the intake temps do matter much more than with a car like they tested. If too warm, we'll get spark knock, and KR, which does hurt power. We also can see timing gets cut by the PCM, just because intake temps are high, even if there's no KR.

So the demonstration is consistent with what Kenne Bell Superchargers has said for years about warning people NOT to use short ram or other "warm air" intake designs, which are unfortunately labeled as CAI. A true cold air intake does what their crazy snorkel tube does - keeps IAT at ambient.

One last thing: CAI designs can't really be tested effectively on the dyno, simply because the car isn't moving. Even with fans blowing at the dyno, which they only did for part of the testing, it's still not the same as a car moving 50 mph+ and getting a full blast of fresh, cool air to keep the engine and trans else cooled, as well as providing actual ambient or even slightly sub-ambient air to the intake. No surprise, the head lamp trick wasn't effective. Would anyone expect it to be with the car sitting still?

Quote :

"Why couldn't I redirect this to to the engine bay and to my intake?

No one has ever done this? It seems like a pretty straight forward modification. With these Ohio summers though Im not sure I would sacrifice my AC for HP....

Larry is 100% correct. The AC could not possibly provide enough air to supply the super charger. And if it could, the air would be moving much faster past the condenser, so the air wouldn't get cooled down as much. Even if you directed the air from the AC to mix with the outside air, the % would be so small that it probably wouldn't affect much at all.

Lastly, a little humidity in the intake air is a good thing, because it turns to steam during the combustion process, helping to keep temperatures slightly cooler as they release into the exhaust. This is the idea behind water and methanol injection. By routing intake air from the AC, yes it's cooler, but it also contains near 0% humidity, so the cooling effect is limited.

Of course, there is an easier, more effective way to condition the air in your intake that auto makers have been doing for years. It's called intercooling.

Great write-up, Aaron. I wish I was just 1/2 as smart as you about cars (no kidding)

Thanks, Dave. But honestly, most of what I know comes from 4 things: fixing older GM and Chrysler cars growing up, modifying and tuning the Riviera, talking to 3800 guys like the INTENSE team and Ed Morad, and learning from the membership at this and a few other online bulletin boards. I would know almost nothing without support from you guys here at the forums.

I'm glad that you brought this up AA. I was talking to my brother about the video, and we were discussing that the car they were denoting was a skyline! These cars obviously come stock with a high performing intake system. And also they were exposing the cone filter to more heat as compared to the stock box blocking engine heat.

Exactly. Shame on those guys for picking a car they knew would work for "busting the myth". If they had picked a more average vehicle, the cone filter would have provided more air flow (more HP gain) and the colder air source also would make a slight difference.

Our SC 3800s are probably more effected by a good cold air set-up than most NA engines, because the blower is going to be limited by the intake and filter (more so once you drop the pulley size), and since KR is such a big issue with our engines, cooling the intake air becomes much more important. The same would be true for any SC non-intercooled set-up.

Good points AA, so with an intercooler underneath the supercharger, would you say it would make sense to have a fender well intake, or would it be smarter to have an open cone filter close to the throttle body? I'm just curious if the initial temperature of the air is going to matter, because of the effects that the intercooler would have in the intake manifold.

RidzRiv wrote:

Good points AA, so with an intercooler underneath the supercharger, would you say it would make sense to have a fender well intake, or would it be smarter to have an open cone filter close to the throttle body? I'm just curious if the initial temperature of the air is going to matter, because of the effects that the intercooler would have in the intake manifold.

Cody has his intake close to the TB in Turtle. I still don't understand why you would want it so close but he is a genius so I do not doubt his decision.

Ha that is the same example i was thinking of Charlie. I'm thinking if the air is going to be cooled to a certain temperature at the intercooler, the previous temperature may not matter. I'm not sure, but i think have the filter closer to the throttle body can help with throttle response.

You have a better chance at getting away with open cone or other warm air intake design if you're running an IC. But really it depends on how much KR you're seeing with the IC installed, which depends on boost level, the size IC used, and other mods. In some situations the intake could still make a difference.

Say it's 70ºF outside, and your FWI is sucking in 70ºF air, with stock SC pulley boosting 7 PSI, the blower adds a certain amount of heat from compression. We'll say the compressed air increases +100ºF as it moves into the LIM, so the result is 170ºF at the intake valves. Assuming the timing and fueling is correct, this should result in near 0ºKR - for safe 240 HP operation.

Let's say you drop to a 3.3" SC pulley and do nothing else to the car. Boost is now 12 PSI, creating a +180ºF increase through the blower, for a resulting 250ºF in the LIM. The likely scenario is a sharp increase in KR from the extra heat, perhaps 8º or more. The PCM cuts timing (power) to compensate.

Now let's say you add ZZP's Stage II IC, which offers 144ºF temp drop. That 250º air charge becomes only 106ºF, which is way cooler than stock. The same engine that was knocking with 8º KR at 12 PSI can now run KR-free all day long, with correct fueling. In theory, you have about 45ºF of added headroom to play with, so you could probably run a hot-air intake and get away with it.

BUT - if you run a FWI and keep IAT at ambient, you might be able to add hotter timing or added boost to get some use out of that 45º cushion. Maybe drop down to a 3.2" and be just fine - even on a hot day!

Imo, you're usually better off sourcing cool air, even using an IC, because suppressing the knock gives you more options to build extra power. Of course, you could also do more breathing mods, also suppressing knock, and in that case it could make more sense to run an open cone, since the intake becomes more of a restriction at that point. So, if your goal with an IC is more boost & torque, probably should run the cold air intake. If your goal is more air flow & HP, an open cone might work, as long as KR is kept in check.

I would want the air as cool as possible in any scenario. If you've ever taken an advanced chemistry course in High School or College, you'll remember the gas laws. If you increase the pressure of a gas, the temperature goes up as well. The gas molecules have increased kinetic energy, and hit each other, and the gas is less dense. Diesel engines run such a high compression ratio that the heat the intake charge to a point that the fuel spontaneously burns when injected into the cylinder

Running the intake air through a turbocharger or supercharger raises it's temperature significantly. More boost equals hotter intake charge. An inter cooler is like a radiator. It cools the compressed intake charge and drops the temperature, and increases the density of the intake charge. Cold air intakes help lower the temperature of the charge after it has been compressed, and inter cooled. That makes even more power. There is a huge difference in the Turbo Regals and GN's when driving them in cold weather.