Write-Up: Installing FWI Filter, Heat Shield, Air Scoop

Today I serviced my FWI filter. It's been in there 2 years, and in that time I've only cleaned it once. That's one of the downsides to FWI. Cleaning/changing the filter can be a hassle... the price we pay for better performance.

What I found surprised me a little. The old cone filter was very dirty, the metal parts rusted. Although not directly exposed to the outside elements, the fenderwell does not protect the filter as well as an airbox or CAI mounted inside the engine bay. This means frequent filter changes should be mandatory, at least inspect every 6 months. K&N filters, which are normally good for the life of the vehicle, may not last 5 years in a FWI install, unless they are serviced more frequently, I'd say every 6 months is a safe interval.

The filter I used to replace the old cone is a K&N, and it's a bit bigger in size. Here's a pic of the old cone, measuring 5.250" long, 5.875" wide at the big end, 4.750" wide at the small end:



Here's the new K&N straight, round filter, measuring 7.250" long, and 5.813" wide at both ends:



One reason I went with the K&N is: I feel they really are better than your basic off-the-shelf filter. I believe in their ability to flow more air and clock more dirt than the other brands, and their lifetime warranty implies they are well-built. They use rubber instead of chrome/metal parts, which should hold up better... After seeing the effects of the weather on the old filter, I felt like stepping it up a notch.

Obviously, I went with a larger filter to see increased air flow. The K&N model E-1009 I used is the biggest unit I could fit in the fenderwell (I tried 3 sizes). It has a 3.375" opening to connect to the FWI tube. You could also use the E-0774, which has a 3.313" opening, or the E-0773, which has a 3.625" opening. Both of these have the same filter dimensions as the E-1009. FYI, the horn must be removed to use these filters.

Now with the new filter installed, I decided to do some exploring inside the fenderwell. This is when things got interesting. The reason I was curious, I've noticed IAT to be pretty high at idle, then it goes down pretty fast once moving. It's always been this way, and a few may remember my post at RegalGS.org regarding this behavior. I once tried sealing the tube where it enters the fender, but no luck. Somewhere, hot air was getting to the filter, but I never figured it out.

So after sitting idle one 95º day, and watching my IAT go as high as 135ºF, I decided to open the plastic fenderwell cover from the bottom and see what was up (the cover is still attached to the wheel well area). Here's a view from below:



See anything? Look closely. Here's a zoom of right side, you can see the bottom edge of the filter:



Here's a close-up of the left side. You can see the traction control unit and the transmission:



The traction control and the transmission... what's wrong with this picture? If you said, "Those are in the engine bay!", you know where the FWI sources its hot air. The dotted outline shows a direct window, a hole between the engine bay and the fenderwell. It's hard to see from the top side, but when I held my camera down next to the transmission (in the engine bay) and aimed at the fender, here's what it sees about 8 inches away:



While it's true that this hole is low in the engine bay, I think a lot of hot air gets sucked into the filter. This would explain why the high IAT during idle only. Once air starts flowing through the engine bay, it's not really a problem.

What to do? A heat shield is in order. I'm thinking a piece of stainless steel or aluminum sheet mounted across the hole, separating the fenderwell from the engine bay. Also, venting the fender could help. For starters, I cut some crude slots in the bottom of my cover. Hopefully, this will help remedy the problem. Here's a shot from the bottom with everything put back together:



More to come as more is learned...

AA wrote:

More to come as more is learned...

i have all that stuff pulled off the bottom of my riv anyways. just got the plastic covering the underside of the front bumper. and both interior fenderwell lining removed. but the right one causes the belts to squeal for a few seconds at idle when I nail a big puddle of water.

too bad we cant re-route our a/c lines to wrap around the filter and intake hose
Aaron, if you wernt obsessed with performance then non of us would lean anything. how hot does the TC motor get sitting idle? let us know if you feel a difference in the filter sizes.

I'm not sure if the bigger filter makes that much difference, but that plus going from dirty to clean made a detectable increase. I noticed more pull after the upshifts after installing. When it comes to filters, it's a no-brainer to use the largest size that fits. It can only be better.

As far as removing the fender panel entirely, I won't go that far. After seeing my protected filter 2 years, I can't imagine how an unprotected one would fair. If my plan to fab a heat shield works, I may create a "ram-air" scoop on the bottom, over the vented slots I cut.

Whatever the case, IAT must go down! There is no point in intercooling if you aren't first feeding the coolest possible air to the engine at all times. Finding a better air source should be a very effective KR-decreasing mod.

Wouldn't cutting slots in the bottom make it prone to water? I don't know if I'd want water splashing up onto my fitler anymore that what already gets in there with the liner stock.

Water splashing up from where?

From the ground? You are talking about cutting the fenderwell lining right underneath the filter right? Wouldn't that bring in water if you drive through a puddle or driving in the rain?

If I were driving in reverse, maybe. But since the slots are located ahead of the wheel and not directly beneath the filter, I don't know how water could splash in as long as you're moving. Yes, if you went through a puddle deep enough to submerge the front end, I can see that being a problem. Here's a sketch:

That drawing looks very nice

I agree with SPACE BAR. Haven't you ever hit a puddle of water and seen water splash towards the front of the car. I kinow i have. Even with relative speed, i can see water splashing forward.

by the way, have you seen any difference in air temp at idle?

Haven't scanned yet, but drove through a monsoon tonight. All systems are go!

Use the lining to build an airscoop.

Well I've decided to try and improve things. This hot air issue has plagued me for too long. The idea is to shield the lower portion of the fenderwell from the engine bay. Planning to cut some plastic or sheet metal to form a wall that covers the hole, so the filter breaths from the bottom rather than from the bay.

First thing I did was scan for some baseline IATs. At 90 F ambient temp and a 60 mph cruising speed, I am seeing ambient IAT - 90 F. I like that. If I go faster, my IAT goes sub-ambient, more and more until about 80 mph, where it reads 85 F. I really like that, but don't know if this is real, or if my IAT sensor is off.

Below 60 mph, a warming effect ensues. Slight at first, then more as I slow down. On the same 90 F day, cruising main streets with occasional stops, I see between 90-100 F IAT. In stop and go traffic, I see 110-115 F, and idle, between 120-130 F. Did a test sitting at idle for 5 mins, and was able to get a value of 149 F!!! Scary stuff happening here, and this is what I hope to change.

It's very hard to tell exactly what's causing the IAT to go up, whether it's just one thing or a combo of variables. On the freeway, going 60 mph and seeing a gradual rise as I slow, I assume this is from less cold air getting through the radiator, so the engine bay gets warmer. Interestingly, when I hit the gas at 60 mph, my IAT goes up quickly, so this may be the front header warming the air before it hits the air filter. Just theories at this point.

When I'm sitting idle , it may be a combination of factors creating hotter IATs: 1) warmer engine bay air reaching filter, as described above; 2) TB and engine bay air warming the intake pipe; 3) warm air flowing around the outside of the car (not much I can do about this).

Joe, I like the idea of a scoop under the car, just need to fab some sort of water deflector inside.

Removed my fenderwell plastic today. Here's what it looks like from the side:



And from underneath, looking up and toward the front of the car:



I took a piece of sheet aluminum, cut to fit, and bolted it into place between the TC unit's bracket and the frame. Seems to be very secure this way. Here's a pic installed before putting the fenderwell back together:



Another from the bottom:



From the top looking down (transmission at bottom left):



Now have to wait till it gets up to 90º again and log some new scans.

Just in from a test drive. It was only 80º out, not 90º. I think the shield is helping some, but not as much as I'd hoped. One good thing is the IAT seems to change from warm to cool more quickly than it used to.

Tomorrow will begin project "ram air".

so when is project "IC" ? your research and dedication is always interesting at the very least we all know not to race after sitting idle for 5 min KR is probable out-the-ass at those temps

I don't think the mesh on high quality filters (k&n, S&B) rusts. I have had my filter for 4 years (1.5 in the riviera's FWI) and it still look great. The crappy ebay filter I had on my old 323 rusted out in the engine compartment, far away from any water.

I took the riv's filter out today to clean it because I had the car rustproofed and they shot the inside of the fender with oil. It was dirty, but not as much as I expected after 1.5 years. Note that I didn't drive the car during winter.

Aaron, did you ever monitor the IATs when you had your gutted box? The stock filter ass'y takes its air from the area the FWI is located in, so you are probably sucking in warmer air during idle even with the stock system.

The filter I had before was a cheapo. Glad it's out of there.

I did monitor IAT when I had the gutted box, but don't have them recorded. My memory is that there was a sizable drop in temp after the FWI - while cruising, but sitting idle not much change from the stock air box. I never got IAT equal or lower than ambient with the gutted box, even in cold weather.

My problem wasn't as bad it seems before I put the headers on. It seems a lot hotter under the hood now. This is a big part of the problem, I think.

Air will do some funky things with a car when it is at speed. It's very turbulant around the radiator and you could have air coming from anywhere.

Sitting at idle and traveling slow you've got to consider the temperature of the surface you're on as you'll be getting a lot of the radiated heat when you're sucking air 6" from the blacktop.

You could try to seal the area between the radiator and the engine which would keep the hot air from dumping out towards the ground from behind the radiator when you're at idle and slower speeds.

Its hard to say unless you wanted to run the riv through some fluid dynamics and wind tunnel tests.

Good points. I think it will be hard to impossible to seal the radiator to the engine, so instead I tried sealing the fenderwell from the engine bay. Not quite sealed, but divided at least. I have to think that with the scoop installed, any heating caused by the road surface will be less then that of the engine.

The good news is, with the scoop being so low on the car, I don't need to worry about driving through puddles and sucking up water, as the filter is higher off the ground, and has other sources to draw the air from. Air will not be sucked in the vent, but rather forced in at speed.

so take the weatherstripping off at the back of the hood. That will lower your underhood temps a lot.

Thanks, but I already did that 3 years ago. I even leave it off in the winter.

Went shopping for a few items at Lowes this morning. Total bill: about $7. To be realistic, this will not be a true "ram air" system, but a simple vent. The intake will pull in air as it needs. What I'm trying to do is make sure as much as possible comes from outside the car.

First, I took a piece of 4" rain gutter and cut it at an angle, then bent it with pliers to form the scoop. I didn't measure, just cut to fit the underside of the well:



Using the scoop as a template, I drew a pattern and cut it out with a Dremel. The hole is in the same place as the vents I cut previously, Note in the background you can see the heat shield I installed, not the transmission/engine bay:



Here's the scoop in place, testing fit:



And here it is installed after painting "outlaw black":



From looking around the car, you really can't tell I've done anything unless you get down and look for it:







I'm planning to pick up some screen today to keep rocks and squirrels from getting in. Time to take a drive... it's almost 90ºF outside!

It's 92 F right now, and I've been driving around recording IAT at cruise, idle, and stop & go. Temps are a little lower now, even though ambient temps are a little higher than on Fri when I saw IAT go up to 149 F at idle. I cannot get IAT over 142 F. I know, doesn't sound like much improvement, but the new mods are helping in a different way.

When I sat idle on Fri, it took less than 5 mins for IAT to shoot up to 149, and it could've gone higher had I not quit the test. Today, I stayed parked for almost 10 mins. IAT rises much more slowly now than before. Similarly, when I'm in traffic I am seeing slightly lower IAT, but as soon as I get moving again, they start dropping much faster than before.

So far, I'm happy with the results. Slower to get hot, quicker to cool down, and slightly cooler IAT overall.

what are your coolant temps when idle for 10min? do you have a TB spacer or coolant block off?