Cold Air Intake (CAI) vs Fender Well Intake (FWI)

I see. Well and im shur that car isnt a DD

Lots of people run the hot air intakes with no problem. It's not the best way in my opinion, but it works in the cool months, and when the car's moving at speed. It also probably works fine for a track car. I met a guy at Norwalk with an open tube sticking through the fender wall of his L67-transplanted Olds 88 - no filter. His car ran mid 13s. Now who's really gonna try and tell him he's wrong for doing it? Not me.

Everyone does things a little differently. As long as you know the risks and have a good reason for it, make the best choice you can and do however you see fit.

I agree with Aaron and have to clarify my statement above about CAIs on these cars as I'd hate to spread misinformation.

Most times when I see CAI, I assume the person is referring to a box that is built around the filter in the engine compartment. To date, I haven't seen one that seems really effective.

If by CAI, you are referring to something that is completely out of the engine bay, then it definitely would work. I would never dispute that getting colder air to the engine is best in order to have it run efficiently and without knock. People run intercoolers to keep the blower air outlet temps constant and cooler (better for tuning and performance with less detonation obviously).

There seems to be a majority who say that FWIs are not as great as one would think---> The biggest problem would appear to be any sort of drastic bend in the duct required to get the filter in the fender. I'm not sure about Rivieras but I know that my Regal required a 90* bend. I lost 1 psi at WOT with this setup. Not a huge deal. I used roof flashing that I sealed on that side of the bay and cut it to the diameter of the 4" duct going to the fenderwell. When sitting at a traffic light, I still saw my IATs go up while the engine bay heat expanded outward. IATs would be anywhere between 20-40* higher than ambient.

HTH clarify any misconceptions about my previous statement.

90º bends are bad, but I don't know why anyone would need to do that for a FWI install. I agree the fender well is not a foolproof location for the intake, as it puts the cone near an opening to the engine bay. I created an aluminum heat shield to block off my engine bay from the fender, and this helped some.

as far as 90deg goes, I think we all can understand it adds some restriction.
I can't remember the actual numbers(Had it worked out for a job), but in 3.5" pipe I think the restriction of a 90deg bend is the equivalent of having a pipe that's 5 feet longer. Each 90 adds to the length for equivalent flow amount if the pipe was straight(best scenario). Granted it depends on the material, joints, etc...

Karma wrote:

as far as 90deg goes, I think we all can understand it adds some restriction.
I can't remember the actual numbers(Had it worked out for a job), but in 3.5" pipe I think the restriction of a 90deg bend is the equivalent of having a pipe that's 5 feet longer. Each 90 adds to the length for equivalent flow amount if the pipe was straight(best scenario). Granted it depends on the material, joints, etc...

Wouldn't that be for a naturally aspirated intake.?
I've done similar calculation for naturally aspirated intakes to determine the optimum runner length based on cylinder volume and other parameters.

How does adding the equivalent of 5 feet to an air intake tube on a Supercharged engine make a difference in efficiency. ?
Once the engine and supercharger are turning you have a certain amount of airflow. Isn't that based on the SC's capacity for drawing in air and the diameter of the tube bringing that air in.?
Am I missing an ingredient here.? I am curious, it's been a while since I had the books and formulas out for the subject.

Intake restriction is intake restriction, whether it's NA or FI - it's going to hamper the ability of the blower to pull air into the engine. Yes, you can say a blower will pull 'harder', but remember to whole point of a supercharger - you're bringing a lot more air in to begin with, and using engine power to do it. To look at it another way, if the blower is capable of bringing in 30 cu.ft/min of air, and the engine is tuned to run on that amount, putting a 90º bend in the intake will lesson that amount of air, and performance will suffer.

With the exception of the PVC intake, we shouldn't need to use 90º bends. And in the PVC intake's defense, the diameter is bumped up to 4" after the TB, so this would offset most of the restriction caused by the bend, imo.

Rickw wrote:

Karma wrote:

as far as 90deg goes, I think we all can understand it adds some restriction.
I can't remember the actual numbers(Had it worked out for a job), but in 3.5" pipe I think the restriction of a 90deg bend is the equivalent of having a pipe that's 5 feet longer. Each 90 adds to the length for equivalent flow amount if the pipe was straight(best scenario). Granted it depends on the material, joints, etc...

Wouldn't that be for a naturally aspirated intake.?
I've done similar calculation for naturally aspirated intakes to determine the optimum runner length based on cylinder volume and other parameters.

How does adding the equivalent of 5 feet to an air intake tube on a Supercharged engine make a difference in efficiency. ?
Once the engine and supercharger are turning you have a certain amount of airflow. Isn't that based on the SC's capacity for drawing in air and the diameter of the tube bringing that air in.?
Am I missing an ingredient here.? I am curious, it's been a while since I had the books and formulas out for the subject.

A supercharged intake is still having to draw the air. And the Eaton blowers are best at pushing, not sucking. Any reduction in work to suck through the inlet provides gains, such as going N* in the TB. Do 90deg bends make much of a difference in our application? I personally doubt it. A perfect smooth walled intake with a few 90 deg bends IMO probably flows better than the slightly ribbed flexible intake tubes. But our lengths make it negligible, and the main restriction in our system would be the throttle plate. I should have clarified that my statement was academic in nature regarding 90 deg bends in general.

im debating on witch one i should try out spend the 40$ off ebay for the cold air intake when i get back from basic or should i try the FWI?

btw this is his son that he has talked about with the fuel pump problems about it i read all about the CAI and the FWI just worried about the elements but im up for opinions?

I hooked up my ScanGauge II to the Riv to see what's happening under there...

I have not made any mods to the car since I got her home last week. Bone stock 1996 SC with 49k miles. Running 93 octane.

61 degrees outside tonight as I drove home from work.
Coolant temp was in the 195 to 200 degree range all the way home.

On the open road and holding at 50-60mph, the air intake temp was about 10-15 degrees hotter than outside temp (around 72 to 78 most of the ride on the highway).

I got off the highway and sat at a couple of red lights. The coolant temp went to 202, then to 204... never higher than that (I will be putting in a 180 degree thermostat in the next few weeks, along with the Autolite 104 plugs).

The idling caused the intake air temp to spike! It went as high as 104 degrees as I sat... Even once I got moving again, it took almost 10 minutes before it came back into the mid-80-degree range.

Point is, even the factory air box is a bit of a "Hot Air Intake" system, IMHO. I certainly would advise against an open element air filter under the hood. I will be looking to do a gutted factory air box first and see how that does in terms of air intake and intake temperatures.

Your observations are accurate, and typically what we see with stock intake systems. You may find reading the following threads interesting:

https://rivperformance.editboard.com/t1209-write-up-installing-fwi-filter-heat-shield-air-scoop

https://rivperformance.editboard.com/t8404-write-up-omega-intake-air-temperature-sensor-iat

Thanks, Aaron. Read the first one earlier tonight and just read the 2nd posting.
Excellent info. Thanks for passing this along!

http://intense-racing.com/Merchant2/merchant.mvc?Screen=cp-tips-and-tricks
Thought this was interesting. Lot of discussion on it here and I wasn't sure which thread to post it under.

Should I purchase an IAT Spoof Module?

The Intake Air Temperature module is simply a resistor packaged impressively and marketed to customers who don't know any better. These can sell for as much as $25 and many are lured into purchase by its low price and easy installation. It tricks your PCM into thinking it's cold outside and therefore 'optimizes timing'. In reality it does little to nothing and cannot change commanded timing by more than one to two degree (and that's on a hot day where you probably can't use the extra degree or two of timing advance anyway). Save your money and don't buy it. If your curiosity gets the best of you, buy an 8k-Ohm resistor from Radio shack and save $24.50.

But isn't the IAT module where we get our IAT readings when we scan?

No, the IAT sensor is what gauges the IAT. The IAT module is basically a resistor that goes inline between the IAT sensor and the PCM, altering the resistance and tricking the PCM into thinking the air is colder than it actually is. INTENSE is absolutely correct. Our timing tables do not add timing when IAT reads cold. Waste of money.

Even if you did want to do this mod, you could just as easily go to Radio Shack and buy the same thing for $0.25, like they say.

There is one IAT module, sold by ZZP, that does actually work. Of course, you must first program the ZZP PCM tune, in which they've altered the timing tables for boosted timing at extremely low temps (like -50F). The module tricks the PCM into thinking it's -50F, even though it's really not.

I'm lookin to do the fwi to my 95sc. My only big concern is, its generally quite wet where I live. Seattle, WA. 80% of the time its at least raining and the riv is my daily driver. Backroads, interstate, city. That means high speed heavy water pickup by the tires, puddles, general wetness. Is an fwi out of the question?

It's not out of the question. You may need to clean your filter a couple times per year, but it won't hurt your engine unless you drive through a flood. I've been running my FWI for 5 years now. We get our share of rain and snow in OH. Recently I had the engine rebuilt. I was told it was very clean inside, no evidence of any water or foreign material entering the intake and scoring the bores, etc. FYI, I do change my oil religiously every 3000k.

See here about some shielding options I've tried to maximize colder air and minimize the exposure to elements:

https://rivperformance.editboard.com/t1209-write-up-installing-fwi-filter-heat-shield-air-scoop

Thank you VERY much for the help on that! So much extensive coverage on this topic and tons of very helpful visuals too. I love this site!

The weather has spoken! After our unseasonably long 70+ sunny day streak, the rain is back (and in full force!) It's been my first time driving her in the typical weather and I've found that where I had placed the cone temporarily (in the vacated spot where the original box was) there's an uncomfortably high amount of rain water and debris reaching this area. Small puddle and even some leaves! so I've decided that a true Cai is the best route to take. I'll be leaving the cone exactly where it is now, but will place a filter (much like the stock flat filter below it to cover up the existing access to the fenderwell (as there is on the 95s) in order to add an extra layer of guard against water/debris through there. In addition I will be creating a shroud to surround the cone completely within the engine bay. Lastly, I still intend to use my naca duct idea down below the fenderwell but will run it directly into a 4" duct straight into the Cai box. Essentially outside air > naca duct > 4" hose > flat filter > shrouded box w/ cone > 4" hose > tb. Sounds longer than it really is and I strongly believe there will be excellent COLD air flow through this method along with maximum protection from the elements. Debunk away if I've left any dumb ideas on the table

Gutting the air box or custom fwi wont this mod trip the computer? And make the maf crazy

No.

According to this chart:
http://www.engineeringtoolbox.com/thermal-conductivity-d_429.html

An intake primarily formed of silicone will be more resistant to heat soak than an aluminum based intake. Right?


Thermal conductivity is the property of a material to conduct heat. Thermal conductivity can be defined as

"the quantity of heat transmitted through a unit thickness of a material - in a direction normal to a surface of unit area - due to a unit temperature gradient under steady state conditions"

Thermal conductivity units are W/(m K) in

Aluminum 205
Silicone cast resin 0.15 - 0.32

for reference:
Phenolic cast resins 0.15
Stainless Steel 16
Iron 80

I would think you would want aluminum or copper because of their ability to dissipate heat. My logic is that they're used in heatsinks where the primary goal is to get heat AWAY from the object. Then again I'm not a thermal engineer so what I'm saying has pretty much no basis.

You want to dissipate heat away from the engine, but through the intake tube is not the best route. If the intake tube gets hot, the intake air will carry that heat back into the engine, defeating the benefit of CAI. Heat is the expected product post-combustion, but it is a bad thing pre-combustion. Also, heat soak will raise the temp of the IAT sensor upstream, throwing off the reading to the PCM, which can be a bad thing in regard to spark advance.

Keeping heat from the intake is the idea behind TB spacers, and is one reason why plastics and rubbers are used for intakes in modern cars. Silicone is not superior to other plastics for its thermal insulation properties, but can take very high temperatures (good for brake duct cooling hoses, way overkill for air intakes), but it is flexible and resilient to chemicals, so makes for a nice hose coupler connector.

Stainless steel is a much better insulator than aluminum, so if you want a metal intake, this is the ticket. Otherwise any plastic or resin tube will work, and will be less expensive than silicone.

But... There is so much air entering the intake under WOT, each Cu Ft is in contact with the intake tube for only a few milliseconds - not enough time to significantly raise the temperature of properly sourced intake air. Don't worry about heating the air itself - the increase is minuscule.

The real concern is IAT sensor heat soak. If the intake tube conducts enough heat to the IAT sensor mounting area, it will throw off the reading. My stainless steel FWI intake with silicone coupler is usually cool to the touch, and I've never seen the sensor report anything but the temp of the air itself. This is where aluminum could mess things up. I'd steer clear unless you have a good reason to use it.

AA wrote:

The real concern is IAT sensor heat soak. If the intake tube conducts enough heat to the IAT sensor mounting area, it will throw off the reading. My stainless steel FWI intake with silicone coupler is usually cool to the touch, and I've never seen the sensor report anything but the temp of the air itself. This is where aluminum could mess things up. I'd steer clear unless you have a good reason to use it.

cool to the touch!? What IATs have you been seeing this week?