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

I have a 4" PVC FWI. i was thinking about getting a larger cone filter. Does a larger cone mean more power and a louder SC whine?

Probably a little more power. I felt something extra when I upgraded mine.

well i have the short spectre filter i think and i was thinking about upgrading to the huge long one, cuz i have plenty on room in my fenderwell. So will i see any gains? what about a little louder whine?(thats what i really want, even though its really loud now)

I don't think you'll notice any difference, unless you are running a GenV cammed with a 2.8" pulley, stage 3 heads or so... but try it and let us know!

well i dont really want to spend $50+ on a new filter if its not noticable.

i too doubt you will see, hear or feel a difference in upgrading a cotton filter to a larger cotton filter. the car is only pulling in so much air through the tube and TB. unless the filter you have now is restrictively small, you shouldnt see a gain IMO.

if you want louder whine, get a gen V or port the gen 3.

okay thanks guys you help is appreciated

Here are a couple of shots of my new ram air scoop. It is larger than others I have seen here. I made it larger as I don't have a FWI filter, this scoop feeds a 4" pipe that goes directly into the bottom of my stock airbox.
I used a piece of 6" corrugated plastic pipe to fabricate the scoop, and I have a 4" flex drain pipe connected to the bottom of the airbox.
I noticed immediately that the little bit of hesitation I had is completely gone. Now I will be looking to make a road trip to see if the colder air and better flow will improve my mileage.




Here's one from out front:

Thanks for posting the pics! I am gathering info to try and decide what to do with the wifes 99 Riv. I like your air scoop.

But I am concerned about your statement that you had a "slight hesitation" before the installation. With a Fuel Injected vehicle like a Riv a hesitiation of any sort would indicate some sort of problem, such as a vacum leak.

Thanks again.

Bert

Maybe hesitation was the wrong word, more like sluggishness. Not an absence of responce, but not as pronounced as the response to throttle is now. The car definately seems quicker, like there is more low end. BTW there is no significant sound difference that I could tell. I thought that I would have a lot more SC whine but I dont hear much. When I have the top of the airbox off I will post shots of that too.

Did you replace the air filter? That usually accounts for a big difference. To get the whine, you need to gut the air box. See write-up here:

https://rivperformance.editboard.com/series-ii-engine-transmission-f4/write-up-gutting-the-air-box-t680.htm

AA,
I read this legacy thread and will likely pursue a similar mod. One thing... where are you getting the temp data from? I noticed in the recent track video (where you encountered the piston chip) that you have some kind of comprehensive monitoring panel, measuring blood pressure, heartbeat, stress, etc. Can you tell me about that thang?

FYI, the scoop mod was removed some time ago, however the heat shield stayed in place. Results are just as good without the scoop - air enters the hole cut in underside panel.

The IAT sensor is mounted inside the FWI intake, just beyond the filter cone (your OEM air box also has an IAT sensor). The PCM is aware of the intake air temp at all times. The HVAC system also uses IAT data - AC won't run without it. I use an Omega sensor in place of OEM - it gives quicker response time. More:

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

The diagnostic panel you see in the vid is called Torque, an app for Droid. Any decent scan tool will report IAT. Read the Scans & Tuning forum for more info on scan options. My personal favorite app for logging/tuning purposes is AutoTap. My preference for real time data monitoring is the Aeroforce Intercepter gauge. More on Aeroforce:

https://rivperformance.editboard.com/t3986-faq-aeroforce-interceptor-scan-gauge

RE: ram air approach
Just a thought.
Members familiar with the front end mechanics, and FWI mods... IYO, does this slant on the ram air mod seem structurally feasible?
Opinions?

Should be feasible to build this. You may need to remove the horn on driver side. Imo, it would be mainly a visual enhancement; it would work just as well pulling air from the bottom. There would actually be no "ram air" effect, since the blower is taking in the air at a faster rate than would be forced through the vent at speed.

Thanks.
Ram air is just a convenient description.

I'm a little fuzzy on the end product of the usual FWI mod. I've viewed all the photos available, but still can't determine if enough of the inside fender well remains to protect the filter jammed in there. In any case, I can't help but think that the tire is kicking up dust no matter the surface.

Thought perhaps a closed route from the bumper fascia, maybe using a flat filter installed in a gutted box might reduce cleaning maintenance. And it would sample theoretically cooler air from ahead of the engine compartment.

Sure, it's a more involved answer to reduce IAT and increase flow, but may make filter maintenance a simpler under-hood procedure, and of course, create a different look.

Thoughts?

I would suggest next time you have the front wheel off, pull all the plastic fasteners and remove the fender well lining. You'll see right away how much room exists. There is some mild structural bracing, the cornering lamp housing, and the horn. The space is a tight wedge, but I think you could cut a hole in the bumper just fine.

Depending on what you mean by "protect", structurally, the filter itself is suspended by the intake tube, although I built a small support in the bottom of the well to support the filter, in case it decides to wiggle off. With the support installed, mine hasn't yet for over 150k+ miles.

If you meant protection from road debris and the elements, consider that even rolling 5 mph, air sucked into the bottom of the forward fender area is for all intent purposes the same air that would be sucked into a front vent, because the air supply is freshened as the car moves faster. Dust and water particles from the front tire really aren't going to move upstream in the gust of oncoming air, even at 5-10 mph. Driving in reverse gear would be the exception.

Perhaps the biggest concern I would have with a front sourcing intake would be the direct introduction of water and foreign debris into the fender well area and filter, since those things come from the front, not the bottom. It's a straight shot if driving in the rain, or if close to a truck kicking up dirt/rocks in front of you. The duct opening could act like a funnel to capture things that shouldn't go into the intake, unless you install countermeasures. If you examine front sourcing air ducts in OEM applications, such as used on the Audi S4, they use a thin opening positioned high up in the grill, with an elaborate snake of ductwork that moves uphill even more, turning sharply before the air filter. There is also a pre-filter to catch "crumbs".

Regarding IAT, there would likely be no difference between front sourcing the air or bottom sourcing it. Pulling from the bottom gives me ambient temps any time the car is rolling, even slowly. You might see a slight improvement while stopped with the front sourcing duct.

I wouldn't want to talk you out of doing this. Sourcing cold air is a great idea. Just raising some points to consider before cutting into your bumper. As an aesthetic mod, this could be sweet, fitting into my favorite category of exterior features: functional.

Yes, I would have to use an appropriate screen up front, and maybe a catch basin at the point where flow is directed upwards to the box. Material and water to should settle. The basin might have drip holes and a drop-down clean out door. I think that might be enough. After all, the air must flow a considerable distance upward to the box, shedding most everything before being thoroughly filtered. I suppose it's conceivable water could be atomized and provide additional cooling through evaporation (?). Not sure how that concept would affect other parameters.
And, if the inlet is too small or water can't be evacuated as quickly as taken in, a good splash could choke the whole shebang
Does need work.
BTW, by protect, I meant from dust and whatnot, not structurally.
I'm not sure I buy that the well is purged from road material at speed. It's a dirty place, moreso in different seasons. Tire and wheel are constantly spinning, creating there own turbulence, and covering new ground (and crap) all the time.
I wonder if you have ever seen a stock application as naked?
Thanks for the input. It's all good.

Quote :

I'm not sure I buy that the well is purged from road material at speed. It's a dirty place, moreso in different seasons. Tire and wheel are constantly spinning, creating there own turbulence, and covering new ground (and crap) all the time.
I wonder if you have ever seen a stock application as naked?

The point I'm trying to make is, any turbulence and ground covered by the wheel is passé relative to the position of the underside air inlet, which is positioned ahead of the wheel. Since the fender lining protects the back side of the filter, the only way water or dirt from the wheel is going to find it's way to the intake is to travel upstream against oncoming winds from moving 20,50, or 75 mph.



Having used this set-up for over 100k miles, and also having used stock and K&N panels as well, I can verify there is more dirt and moisture in the fender well, but it isn't drastically more than what I saw with the flat panels. This is partly due to the addition of the aluminum shield that protects from the opening under the engine bay. The current K&N set-up has been in place for about 4 years, and very little damage from water or debris. It's dirty, but that's what a filter is supposed to do. I clean it about once per year. In contrast, the OEM flat panels got very dirty in only one spot, indicating most of the panel area wasn't being used to pull in air.

It was interesting to hear back from the engine builder that my engine was in top shape except for the chip in piston #1 (detonation-induced). He said the cylinder bores were not scored, valve guides & seals were in great shape. Also no evidence inside the throttle body of anything entering the intake that shouldn't be there. Original blower rotors still have their teflon coating. I was a little concerned about water and debris in the beginning, but this report seems to indicate the FWI isn't damaging the engine. I agree that any water that makes it to the filter gets atomized on its way up the tube and through the blower.

Case dismissed. Congratulations, Counselor

Still, I think I prefer a closed system. Maybe a short cone will fit into the box without compromising flow. Or a different box with insulation.

Just doing the research right now.
Thanks.

I think the important thing is that you are sourcing fresh, cool air. Where it comes from doesn't much matter. I guess we are overthinking and overdiscussing the "how" of it. If you want to see a visible inlet in the bumper, I think you should give it a shot. Personally, I wouldn't change what I have, since it performs well; just can't be seen from the exterior.

Keep in mind that the OE airbox already does a good job of this. If you remove the airbox and look at the inlet hole, and the hole the grey baffle thing sticks through, you have two good sources of air from outside the engine compartment already. My first gutted airbox - I removed the grey baffley thing, the orange curved thing, and added a bunch of foam insulation on the outside of the box so that it was forced to take all the air through the two existing holes in the sheetmetal. This draws all of it's air from the area you describe AA. If you want to get really picky about the air source, you could block the opening to that area from the lower engine compartment, but I think you are already getting cooler air simply by drawing air from that area.

Thanks for the input, Deeks.
I'm just kicking around an idea for a closed intake. Am fully aware it needn't be more complicated than the FWI commonly used. It seems fine. I'm just looking for a different, maybe more effective answer, with my own dna.

So I've got a couple pals who work at Everett engineering (make custom parts for Boeing and the like) who have helped me with a lot of other car experiments and now I'm planning to use em again. This time, instead of a typical scoop for the fwi, I want a naca duct! I've doddled with precipitation in that area and think that a double screened naca duct would be great here! Essentially acting as the scoop but literally pulling in extra air instead of just catching it. Counterthoughts?

I think that could work great if done right. You can buy NACA ducts unline for pretty cheap. Keep in mind, the supercharger is going to pull the air it needs from wherever, reducing pressure inside the fender well. The duct's "pulling effect" might increase the proportion of cool ambient air to the filter (a good thing), but it won't supply enough so that the all the air feeding the intake is from outside - UNLESS you create some sort of shroud that connects the duct to the filter. That would be pretty cool. Maybe not necessary, but pretty cool.