OAI Outside Air Induction....... Creating a W-3.8?

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Hello Everyone,
I was going to wait until the temps were above freezing to post this thread but Brazilgoal mentioned he was considering installing a cold air intake on his 88 so…….. there’s not time like the present I guess.

This is my winter/rain/poor weather car and is far from pristine. It is a beater I got on ebay for $400 and I am having some fun with it. It is a pretty nice rust free car from PA with 89,000 miles. The car was stolen and joy ridden and recovered with the radio stolen and column broken. I bumped/painted the fender, repaired the suspension, and gave it a new header/lamps/grill. I still can’t find the right front bumper so it has some ’89 pieces on it. I have done a lot of cool mods to the car not mentioned in this post.

Most people now call them CAIs, but true to Oldsmobile and its outstanding engineers, we’ll stick to their nomenclature and call it OAI. In an ocean of applying new technology to old cars, why not apply some old technology to new cars? There is no denying that OAI systems are functional and very cool so I pulled out the stops and put one on my 1990 88.

Here’s how it went:

In planning the whole system I knew the most difficult part would be the intake scoop. After some debate I decided the air intake should be pretty much like the original W-30 cars’ under bumper scoop. Browsing the local salvage yard for just such an animal proved to be a lame attempt as there was none to be had. So I made one. After surveying and contemplating the evident constraints, I made a scoop that would fit them all. The front opening of it was my best guess at enough area to take in plenty of air and not be too much of a hindrance when parking or attract too much attention. The leading edge would parallel the shape of the lower bumper. The rear would go up against the factory air dam so the shape had to mirror it as well. The provision for the air tube would be 3” so it would clear the header panel where the tube enters the core support, and that was also the size of the air box inlet. I modeled the scoop out of clay, then made a mold of it, and then made the scoop out of fiberglass. Here is a picture of the mold:

To do the installation I removed the header panel that houses the headlamps and grill. Then I used a hole saw to hack a 3” hole in the core support. Feel free to release any pent up aggression or think of an X spouse or similar on this step. The hole had to be kept low so the tubing would clear the header panel. I then deburred the hole and brushed some primer on it to keep it from rusting (go ahead and laugh, it ain’tpretty). Bare metal here in MI has about the same life expectancy of an unattended Corvette in downtown NY city.

Then I bolted the scoop to the bumper and began installing the tubing. It is just standard aluminum tubing available at Home Depot. Using adjustable elbows was best as in enabled me to align it and snake it around any obstacles. The whole system utilizes three 3”elbows. One elbow to go from the scoop to the core support, one to go through the core support, and one to go from the core support to the air box. I did not use any straight tubing. Some of the ends had to be trimmed a bit. I did not have to drill any holes in the bumper or trim the bumper in any way, or modify anything else to install the scoop and tubing.

After all the plumbing was done I insulated the tubing with standard adhesive backed foam heat duct insulation from Home Depot. It is about ¼” to 3/8” thick with foil on one side. After insulating the tubing I wrapped it with gaffers tape.

Had to take out this image, post only allows 4

Here is a picture of the scoop as installed. A silver pin stripe might look cool around the opening perimeter too. Of coarse my stripe stock includes 2 reds, 5 different blacks, 3 copper/golds, white, but no silver. Sigh.

I would have included more pictures but the post only allows 5. I did not do a before/after test with a thermometer in the inlet tube or anything but it did make a difference in performance. The only downside to this system is that air filters last about half as long as they used to. I remove the scoop for winter and just let the tubing hang behind the bumper.

I have done a second approach to OAI on one of my other cars but it is not as elaborate or efficient. It isolates the air intake and opens it up from what the factory provided but is not plumbed all the way outside. That car is a pristine car from CA and I do not want to cut the core support. That makes it a LOT more difficult to plumb. It has additional constraints as well, due to having heavy duty cooling and a load leveling compressor.

STAY TUNED! ! !

Phase II of the 88 system has been completed. I doubled the size of the air filter with an upgraded air cleaner box. I will make another post on this subject soon.

I have conceived what I consider to be the ultimate OAI system for this body style that I will install first on my TS. It will install without cutting the core support. I have not even started it yet but you can count on two things: It will be cool, and you will see it first here on Oldsmobilefourms.com. Here’s a clue. First I have to acquire a tool I do not have. A SAWZALL! ! !

 

[Brazilgoal]

!!!!!!

I sit in awe reading how you installed your air intake! My route is simpler. I just ordered a short air intake off ebay. A Honda Civic air intake fits on the Olds 88. We'll see how much it really helps.
I do have drop in K&N box air filters in my Altima and Camry. This will be my first air intake without the factory issued maze box.

 

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OAI K&N Filters?

Thank you for the complemtent Brazilgoal and Davedbusman, I thought you'd like that : )

Anyone who already has or is considering getting a K&N with or W/O an OAI system should read this air filter test report.

http://home.usadatanet.net/~jbplock/ISO5011/SPICER.htm

I had a K&N, and after reading this I replaced it with a new AC Delco filter. BUT, my filter is now twice the size of the stock filter too. The stock filter is very small, and the stock air box is a restrictive design. I'll try to get the updated air box post done by next weekends end.

Here is a picture of the 2 filters side by side:

 

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More W-3.8 Pictures

As you can see, these are with the new air box.

The '92 and up air box filter is twice the size as you can see from the pics.

 

[thejmfc]

Looks nice. I'd never seen it done that way before, using the stock airbox. I'll bet you get a nice forced-air effect on the highway. On the other hand, that's a lot of tube to be sucking air through in the city, etc.

I just got done with my new one for the LeSabre a couple of weeks ago. I took an entirely different approach, using nothing at all of the stock intake. My main goals were to eliminate the factory intake duct and box restrictions, while pulling cool air from behind the headlight and from the inner fender area. Here's what it looks like:

I did have to lengthen the IAC sensor lead, so that it could reach the filter. Not a hard job at all with a solder gun and shrink tubing. The box is open, but it does more or less seal itself against the hood liner. Eventually, I might add some of the reflective insulation to the polycarbonate box. It it still a work in progress.

As for the risks of using a K&N filter... I understand that it doesn't filter quite as well as a stock paper filter would, but on the other hand, I do very little driving down dirt roads and the like. I think that for my use, the increased airflow of the K&N (and the expected mileage/performance gains from that) outweigh the danger of slightly dirtier air. It's open for debate, of course...

 

[Brazilgoal]

This is a very short air intake made for the 3800 engine from some of these sellers on e-bay. But it is not far enough away from the engine to satisfy my quest for cooler air.

 

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Giant Sucking Sound

jfmc,
Looks great! I think that clear plex is really nice looking.

Did you make and fit all that plex? Nice Job!

Is that pipe diiamter smaller than the throttle body diameter? It looks like it is downsized coming out of it.

What supports the filter? Is there a bracket not visible in the picture or does it kind of just hang out there?

BTW, I think I do get a nice induction effect on the highway. Last week I sucked up a whole plastic grocery bag into the duct! Only the bag's handle was wrapped around one edge of the scoop.

 

[thejmfc]

Brazilgoal: Ebay? I'm insulted! No sir, this is a custom job with only the highest quality components, including a genuine K&N filter, light weight aluminum tube, and silicone coupler.

Also, the distance from the engine to the filter is really not an issue as far as heat goes. In fact, some have said that the shorter and the straighter your intake pipe is, the better. The key to getting cold air is to insulate the filter compartment from the radiator, exhaust, or the entire rest of the engine compartment. Ideally, I'd have some reflective insulation on that polycarbonate sheet, and a better fit in some places to seal and insulate against heat even better, but it's a good start.

Rocketguy: I can appreciate your post subject. It does indeed make a "giant sucking sound" when cold and at WOT.

The plastic is actually polycarbonate, which looks like plex, but is much more resistant to heat and scratching. Stronger too, less brittle. Also expensive, but I have a connection.. It was actually far simpler than I thought it would be. Some intakes have a bottom, two sides, and a top. This one only needs one side, because it seals decently against the hoodliner and the bottom of the area. I was pleasantly surprised. The key to doing anything like that is to first make a template out of cardboard. And then, when that one doesn't quite work, make another one based on the first. If you do that until you've got the exact shape you want, then you can just trace it onto the PC, and you'll be good to go. For cutting, I just used a hand saw for the straight cuts, and a dremel with a drywall cutting kit for the odd shapes. Worked great. As for the bend, that was tricky... Using a torch, I heated up the line of the bend until it started to bubble just a little, then we clamped the shorter part to a table with a board, and bent it to the angle we needed. If you look closely, you can still see the bubbles in some places, but I'm still quite happy with it. As nice as it looks though, I think eventually I'll add some reflective insulation for maximum coldness.

The pipe is indeed smaller than the TB opening, despite it being 3" pipe. The silicone coupling makes it look worse than it is though. There is no coupling that fits well on the TB without using a bushing of some kind to take up space. It's an odd size. So, between the coupling and the TB, there is 1/8" of rubber from a plumbing coupling. On the other hand, I do think that the size of the pipe is similar to the actual size of the throttle body at the butterfly. It should flow plenty of air, it's just an awkward transition. Some of the S/C 3800 guys run a 4" pipe, but even for that application, most run the 3". I figgure it'll be just fine for my N/A.

The filter is supported only by the TB. The pipe is extremely light, thin aluminum, and the filter is not too heavy at all. That allows it to move with the engine as the motor mounts flex under load. That's not uncommon with this kind of setup, unless they use some kind of super flexible, corrugated coupling, which would hinder laminar air flow.


Really, this kind of setup would be even easier for you guys with older H and C bodies. As you can see in the pictures, I had to work around my PCM, which I ended up laying down under the filter. It's tight, but it works. I also had to work with the washer fluid tank, which you guys have on the other side. So really, you'd have tons more room to work with than I did.