Str8ridin

I perused quite a few SAE articles regarding intake temperatures and their effect on different engine applications and found an interesting standard: By using the SAE correction factor "B" for temperature's effect on horsepower, we see that the correction factor for temperature is approximately 1% per ten degrees. That is, you get a 1% increase in horsepower for each 10 degrees you lower the temperature of the incoming air into your filter.

I am certain that many of you have personally felt the difference, on a cool, perhaps damp
(there is another correction for that) morning, when your car seemed to have more power than usual, and that those of you who have been lucky to participate in track days have posted lap times in the cool of the morning you could not equal on the warmer afternoon sessions.

This finding prompted me to swing by the local Radio Shack and purchase a digital thermometer with the sensor attached to its 10-foot wire. I attached it to my door.

http://images.cardomain.com/installs...72_17_full.jpg

I then routed the wire connected to the thermometer’s display out the window, under the hood and inside the cone filter to get the exact temperature of the air entering the throttle body.

http://images.cardomain.com/installs...72_19_full.jpg

Here is what I tested:
1) Intake Temperature at IDLE (8 minutes) with Pop Charger
2) Intake Temperature at IDLE (8 minutes) with CAI (I placed sensor in drainage hole in fender where the CAI would reside)
3) Intake Temperature with Pop Charger
4) Intake Temperature with CAI (I placed sensor in drainage hole in fender where the CAI would reside)
5) Intake Temperature with OSCAI (A 2” tube connected to a scoop under the car bringing cold-air to the filter. SEE

http://images.cardomain.com/installs...72_11_full.jpg

Here are the results:

Outside Temperature: 34 degrees F
Test length: 2 Miles/Run
1) Intake Temperature at IDLE with Pop Charger: 95.8F and increasing
2) Intake Temperature at IDLE (8 minutes) with CAI (Sensor in hole in wheel well): 51.2 Steady

3) Intake Temperature with Pop Charger

Temp @ 40 mph: 47.6F
Temp @ 70 mph: 44.2F
Notes: The temperatures were volatile and increased when accelerated hard or came to a brief stop. Temperatures would not reach their low until the end of the run. When stopped for more than 2 minutes, the temperature would rise quickly to between 60-65 degrees.

4) Intake Temperature with CAI
Temp @ 40 mph: 45.1F
Temp @ 70 mph: 39.8F
Notes: Idle temps were already low, so low temperatures were achieved quickly. The temperature did not vary and stayed relatively constant when accelerating hard or stopping. Extended periods of idle would bring the temperature up, but not significantly. I suspect using the fender well as a heat shield aided in the temperature consistency.

5)Intake Temperature with OSCAI
Temp @ 40 mph: 45.0F
Temp @ 70 mph: 40.9F
Notes: The rate of change for the temperature was dependent on the speed I was going. The temperature increased when accelerating hard or coming to a stop, but quickly returned to it’s low under steady driving. Again, as the basic pop charger set-up did, momentary stops for 2 + minutes would send the temperature up to 60-65 degrees.

Conclusion/Serendipity

I was surprised that the Pop Charger by itself, without the CAI or OSCAI set-up was able to produce almost same temperature reading as the other two at speed. I guess, from what I gathered, the CAI benefits the most by creating a ceiling for temperature not to exceed (in this case 50 degrees) whereas the other two allow the intake temps to climb at the engines heated will. This 40 degree difference can be a factor in ¼ mile times where the car must idle for extended periods of time before launching. But as the outside temperatures increase, so will the air in the wheel well, thus making the differences slight. Additionally, I am not certain what adverse affects the longer tube combined with a bend may have on the intake airflow. Perhaps the tube may heat up thus warming the cooler air.

In the end, when comparing the extremes of winter and summer weather, say 10F vs. 100F (engine temps) and using the 10degree/1% power gain correction factor equation, in the Maxima’s case:
100-10 = 90 * .10 = 9% power increase for a 190 hp car which is somewhere around a 17 horsepower difference between the extreme summer and extreme winter case, then I guess cold air should be taken seriously. But when the difference between the ways of obtaining the cold air and inducing it into your engine yield almost the same results at speed, then what should you do? Who knows…

But maybe you could get a head start by using my write up! Enjoy and feel free to comment or add variables or conclusions that I have left out.

-Raceen
str8ridin

Yomie

Hmm... Interesting

hokiemax

iTrader: (2)

I think I have a pretty good handle on the affairs of intakes. I used to have Stillen pop, OSCAI, and PRCAI. I settled on the PRCAI. I'm not sure if a 10F in diff yields only 1% HP improvement, but I TOTALLY agree with you that the diff between a hot summer day and a "so cold you were never born" night is AT LEAST 10HP. With my stillen pop, stillen y, and catback, my car was VERY VERY fast on VERY VERY cold nights of Blacksburg, (home of Va Tech). I felt like I could take on a Corvette. hahaha

If any of you is thinking about getting an intake, dont get one unless you gonna get ypipe too. Of course, if you're getting a CAI just to clean up the engine bay, thats fine.

My recommendation of intakes?

Warpspeed CAI. It's cheap, ready in stock, and those guys seem to be cool guys. But I like cold airs because it cleans up the engine bay. Thats the primary reason I got mine.

Rob'sAE

Much grass on your a$$. (muchas gracias) This was a damned good write up. How much was the thermometer from radio shack? I might do some testing of my own this summer when I get my car back.(if I get it back) It will be interesting to see the differences down here in houston with 90+ degree weather with 75%+ humidity. You did this on a 4th gen right? I believe that my OSCAI might provide better temperature consistancy the way mine is setup. Again, much grass.

madmax2k

I think your "guesstimates" for power change with ambient temperature are in the ballpark. I tested my car in a 72 F dyno room and then later in a 90F dyno room. At 90F, ACTUAL WHP was 205. At 72F, ACTUAL WHP was 211. Barometric pressure was 30.0x both days.

When corrected to SAE, both came in right around 206 WHP.

Keven97SE

Great experiment! Good, unbiased data collection. Your summary is right on regarding the primary CAI/OSCAI benefit being a cap on intake temperature.

Str8ridin

$20 and batteries included. Yes, it was tested on my 4th gen.

thurmer85

nice job that helps me in my decision on what to get cause i just got my max thx for the hep!!!!

poorcollegeboy

nice write up. i have the same gizmo did the same experiment. got the same results. however, i'm looking into how much of an affect the longer tube has on the CAI. it's a given that colder air is better, but i'm a pop-charger believer and would like to make my pop charger have CAI benifits too. debates about CAI and pop charger are usually focused around air temp, but not enough emphases is made on the shorter (non-existent) tubes of the pop and long tubes of the CAI.

here's the low down on the effects of the CAIs tubes....
i've read that the longer tubes in CAIs provides readily available air that doesn't have to go through the filter (hence is slowed down a bit) creating a "static ram air effect".... kind of like an air storage tank. that's why CAIs pull harder at the start - more (colder) air. however, at high ends the long tubes create too much turbulence and that's where the pop charger is better because it almost a direct connection to the intake. if you look at frankencar's intake, the reason why thier intake claims to have better low end power than pop chargers is because it's basically an extended pop charger/shortened CAI. the frankencar uses the upper piece tube from a CAI - this is the "air storage tank" like in CAIs but shorter.

my conclsion... what do you want? high end (pop) or low end (CAI) or a good combination of both (hybrid). i'm personally working on a hybrid (frankencar style) for the 3rd gens and also having a "system" that blows colder air into the pop charger when the velocity is not high enough to cool the engine bay.

sorry so long

http://forums.maxima.org/showthread....hreadid=110111

OriginalMadMax

Great use of the thermometer. When I was comparing placement of the Weapon R intake with and without the tube, I used a couple of oven thermometers, just strapped them to the locations I was comparing and drove for an hour, then checked the temps. The intake tube placed the filter behind the radiator, and that was 40º warmer than behind the battery! I still think a vent in the hood right over the intake would release the heat and make the popcharger more even with the CAI.

My car tested 192 hp on a cool day after sitting for an hour or more. On a hot day, on the same dyno, it ran about 175 hp right after getting off the freeway during rush hour traffic.

OriginalMadMax

They're not necessarily in stock. I guess there was a production problem with powdercoating or something, because I ordered an upper CAI 3 weeks ago and still haven't heard anything directly back from them, except for a reply 4 days ago to a post on here, saying to be patient. I might make my own while I wait ...

Anachronism

Great writup, I was thinking of doing something similer when I finally get an intake. I am still undecided about what to get, your write-up will definatly help. How long after leaving a short stop before the underhood temps started to drop?

Does anyone else think the fenderwell temps would be even lower with the CAI filter in there sucking in a constant fresh supply of air?

It would be interesting to see the temp difference in warmer weather.

ivolley

iTrader: (1)

Raceen,


Great work and research. I am glad that I went with intake and just removed the intake resonator. I am sure your Max is enjoying the the nice cool weather in Northern Illinois. I am very happy with my intake set up.


Great Job!

Prodeje79

nice write up!

I think it would be better to "control" the measurement better by having the sensor in the same locations.
Now this location wise, I think it should be RIGHT in front of the throttle body at the last point where the air goes in.
It is obvious the air will be colder coming from near outside the engine bay. I only wonder if the temp gets higher on its way to the TB coming thru the engine bay?

Just my 2 cents. =D

Str8ridin

Interesting, you're implying that the tube for the CAI can actually get hot and transfer that heat to the air passing through and yield higher temperatures, possibly more at idle. Good point. I wish I had a CAI to actually test it on!

Str8ridin

Within the first 10 seconds of meduim acceleration, the temperatures changed on all set-ups. It took about a full 1 mile minimum (1+ minute)for the CAI & OSCAI set-ups to get within 2-4 degrees of their lows, and a full 2+ miles for the Pop Charger to realize it's lows.

OriginalMadMax

This is where the aluminized dryer duct could be useful. Even if it isn't conducting air, by going over a CAI it can help insulate it from engine heat.

dmbmaxima2k2

iTrader: (1)

i love you, finally someone to back us what i said, once you are moving there is almost no difference in temp from a CAI to a POP/Frankencar setup. once again, thank you very much

BriGuyMax

iTrader: (1)

I have a pop-charger...and I have a 30-minute commute every day...sometimes after I park I pop my hood..and feel my PR middle section and it's still ice cold...even the manifold is pretty cool....I'm also in Northern Illinois

dmbmaxima2k2

iTrader: (1)

ya i've done that before too, drive some where and the pipe is still cold to the touch, liek leave frosted fingerprints cold.

BriGuyMax

iTrader: (1)

so much for the HOT air aspect of the "hot air" intakes....

Cumalot

iTrader: (8)

Guess it depend on where you live right? Down here in Louisiana, it doesn't take long for the engine bay to get really hot.

Dave B

Excellent write up. I did the same kind of test last summer with my POP charger, custom heatshield, and fresh air ducting around the filter. Underhood temps climb fast, but once I get moving, the intake temps drop like an anvil with all the fresh air I've got coming in the filter.

I will say this though, once the intake manifold heats up, it doesn't matter that kind of intake you have.

Dave

JAIMECBR900

I don't know...from reading the write up it shows that really the only one that maintains "cooler" temps no matter what is the CAI. I guess there are a few variables that come into effect here. I understand what you are saying is that when both are in motion the difference is small, but that is only because of the obvious. Look at it this way, the engine pretty much if unchecked just continues to get hotter as long as it's running. When you drive, the airflow from the street thru the bay lowers the temp, but the second you stop the ambient temp inside the engine bay rises quickly and isn't that what the pop charger is sucking in? So, it does suck in hot air but just not all the time. I dunno, I'm still not convinced that a pop or oscai give better overall results as a plain CAI when all the real world variables are put together. I personally think that the pop and oscai are worlds better than stock, but not quite a CAI. So, it offers a great solution for someone who wants the benefits but doesn't want to cut a hole in their fender. Kinda like the Valentine one vs Passport 8500 debate. You know what I mean?

JAIMECBR900

I don't know...from reading the write up it shows that really the only one that maintains "cooler" temps no matter what is the CAI. I guess there are a few variables that come into effect here. I understand what you are saying is that when both are in motion the difference is small, but that is only because of the obvious. Look at it this way, the engine pretty much if unchecked just continues to get hotter as long as it's running. When you drive, the airflow from the street thru the bay lowers the temp, but the second you stop the ambient temp inside the engine bay rises quickly and isn't that what the pop charger is sucking in? So, it does suck in hot air but just not all the time. I dunno, I'm still not convinced that a pop or oscai give better overall results as a plain CAI when all the real world variables are put together. I personally think that the pop and oscai are worlds better than stock, but not quite a CAI. So, it offers a great solution for someone who wants the benefits but doesn't want to cut a hole in their fender. Kinda like the Valentine one vs Passport 8500 debate. You know what I mean?

BTW, excellent excellent write up. Great research and quick reference for us to point people to when they ask the inevitable question about which intake to get. There's at least one a week asking that.

Rob'sAE

As for the intake manifold, and possibly the pop intake heating up problem, how about "louvering" the hood. Over the manifold, angle the louvers like a cowl hood, so the heat is blown out by the fans. As for the pop, angle the louvers to cut into the wind and blow cold air directly onto the pop. It's not going to be 100% efficient but it be the the best of all 3 combined, IMO. My old 280ZX had the "louvers" on the hood. It might not look too great, but IMO I don't think carbon hoods do either. IMO function is a beauty in and unto itself

dmbmaxima2k2

iTrader: (1)

hopefully i can get him to run a test with the heat shield i'm designing and it won't rise quite as fast and settle this forever.

and dave, i never thought about that, intake manifold connected to engine gets HOT HOT HOT and the air will get hot no matter where you get ti from.

jaime- when your stopped and the temp starts to rise, not that fast, but semi fast why would you need all that power, your not moving, and if you accelerate hard to 40 which takes about 3 seconds the temps are almost teh same at that point.

OriginalMadMax

I've been asking about louvres on here for a few weeks. What was posted in response was the "Fast & Furious" Maxima has Dodge Viper louvres. Looks pretty cool to me I think the real trick would be a way to keep the intake manifold cool. Maybe some kind of freon cooling system

neutron

How about stock? I think stock intake would have similar temperatures as CAI.

dmbmaxima2k2

iTrader: (1)

i'd say not based on the OSCAI result, that's the stock with a air vent. i think it would be around pop temps WITH less variance.

JAIMECBR900

You are correct that the temp rises dramatically at standstill, but from the reading (correct me if I'm wrong) it also says that the lowest temp is not reached until the end of the run (some 2+ miles later)which in no way can be reached in a few secs. I guess it's correct to assume that at highway speeds or prolonged non stop-n-go driving the pop is going to be near the same performance as the CAI (setting aside the discussion/debate about the length of the tube and it's performance benefits/hinderances) but in real world situations this is not always the situation we face. I'm not saying that the pop or OSCAI is bad or anything I was just pointing out that the write up/experiment TO ME proved that the CAI is much more efficient and does the best at maintaining the coldest air intake possible under everyday conditions and for the longest time. I'm just thinking that it is a well known fact that the colder the air the denser the charge which translates to better engine performance. If you agree with that then doesn't it stand to assume (from reading the results of the experiment) that the CAI will offer you the best performance (w/o taking into account the above stated debate on the tube length which may or may not have an effect on top-end performance)?

OriginalMadMax

All the more reason to consider a hood vent. Thinking about it from this thread, it seems the filter intake gets enough cool air, but the hot air at standstill needs to escape. Since the manifold is the hotter side of the engine compartment, perhaps if a single vent were used it would be better on the passenger side to pull hot air away from the intake. That might be another experiment, to see if there is a difference on the left and right sides, where the heat builds up the fastest.

JAIMECBR900

I think that would possibly work for "cooling" down the manifold itself, but I dunno that it would offer necessarily cooler intake air. The reason I say this is because a scoop or louver of any kind only helps while in motion (mostly), so we would be back again to the same point the experiment showed which is that at motion (after a while) the intakes all bring in cooler air and basically at the same temp. (at the coolest point). My comment was basically that until THAT particular moment (when all the intakes reach the lowest obtainable temps.), the CAI is the most efficient and offers the best real world solution to ingesting cooler air.

ivolley

iTrader: (1)

The complaint by some CAI owners that @ higher speeds the long intake tube affects top end? If I had an automatic there is no doubt about it I would get a CAI. As far as the increase of temp @ idiling I believe a manual transmission can launch above any minuscule hp loss and as stated earlier by dmbmaxima88 by 40mph the temps are nearly the same. I do admit I am concerned about the performance of my car this summer in the GA heat, I have not driven with this set up in the extreme heat/humidity that we get. As far as the vented hood, what if you could manually control fan to help circulate air into the engine bay while idiling.


[QUOTE]Originally posted by JAIMECBR900

JAIMECBR900

[QUOTE]Originally posted by ivolley
The complaint by some CAI owners that @ higher speeds the long intake tube affects top end? If I had an automatic there is no doubt about it I would get a CAI. As far as the increase of temp @ idiling I believe a manual transmission can launch above any minuscule hp loss and as stated earlier by dmbmaxima88 by 40mph the temps are nearly the same. I do admit I am concerned about the performance of my car this summer in the GA heat, I have not driven with this set up in the extreme heat/humidity that we get. As far as the vented hood, what if you could manually control fan to help circulate air into the engine bay while idiling.

Quote:

Originally posted by JAIMECBR900

That's what I mean, I guess when the numbers come out about top end it will make the decision a bit easier. I don't know enough to state my opinion regarding the physics behind the long tube or short one. I think you're absolutely correct about the fact the 5spds will probably be able to overcome the initial heat build up by lauching a little higher in the rpm range. I dunno, I guess my opinion after it's all said and done is ANY AFTERMARKET IS BETTER THAN STOCK. I'm just impressed that real people took the time and effort to get some real answers and shared them with the rest of us. Once again, very good thread here.

ivolley

iTrader: (1)

Jamie I think we can further test various types of set ups. Perhaps we can meet this weekend and "swap" certain parts of your engine bay and install these parts in my engine bay and I can then "test" that setup for a few months and then provide sufficent information and add to this discussion.



Your are correct this is a good informative thread.

JAIMECBR900

You're my boy and all but you know what they say about women and cars don't you....don't lend out either one. BTW, we missed you at the track the other week, but don't worry I ran a couple of runs with just you in mind. Also, hopefully by thurs. my Y will be here (that ride in somebody's 5spd got me hooked) and maybe then I can keep up with you 5spd boys.

OriginalMadMax

I thought about that, but really it just adds more stuff. Heat rises, and so the easiest thing would be to give it somewhere to go rather than just recirculate it under the hood. This would do more than just cool the manifold because it would minimize the buildup of heat in the entire engine bay. If I could find a nice enough small vent I'd try it. Most are too big and would look bad. The old NASA style reverse scoops would work well. They were no bigger than one's hand, fairly low profile. At idle, heat would rise to escape, while at speed they sucked air down in a reverse flow.

95emeraldgxe

how about just a regular cone filter rather than a pop charger?

ptatohed

iTrader: (12)

First of all, we all owe str8ridin a big thanks for spending the time to not only do the whole experiment but to do a great write-up and share with us. I apologize if this has been brought up already but here is my thought on this. We all agree colder intake air is better. But I guess the argument for a OSCAI or popcharger Vs. CAI is the shorter intake tube. It appears that the OSCAI receives the same low intake temps that the CAI does, at fast speeds. The CAI, however, has a temperature 'ceiling' as you guys said when at idle. Well, what about an OSCAI and a heat shield? Could this be the best of both worlds? That's what I planned for my supercharger. I bought 2.5" vacuum hose with a scoop attachment. This would go from under the car to the stock K&N SC filter. I would then place heat shielding around my filter (not sure what material I am going to use yet). What do you guys think of this set-up?