Write-Up: Flexible Tube Fenderwell Intake

Anthony, thanks for the reminder. It's in the write-up index now.

I did a very similar install in my 98RIV. I just cut a small slit in the tube and inserted the IAT into that. I used grey sensor safe silicone to seal it up. It looks ugly, but works fine for me.

Has anyone used this ducting from Spectre Performance?
http://www.summitracing.com/parts/SPE-9751/

Is this rigid enough that it won't sag, or flop around?

I can't decide whether to use this, PVC piping, or a 4" flexible aluminum duct from Menards that is only $10.00.

I'm going back and forth in my mind if I should do the FWI, or open up my gutted air box more and buy the K&N panel filter that fits the car.

I tend to fall into the trap of over thinking these things.

I used the 4 inch aluminum duct (home depot 10 bucks) for mine, I like the way it fits and works, the only downside is that it dents easily so you have to be careful when installing it.
I would like to have a custom stainless steel one but the cost is too high for me at the moment.
you can see a picture of mine in the showroom section under "some pics of my ride"
(not sure on how to link you to there)

woggy wrote:

I used the 4 inch aluminum duct (home depot 10 bucks) for mine, I like the way it fits and works, the only downside is that it dents easily so you have to be careful when installing it.
I would like to have a custom stainless steel one but the cost is too high for me at the moment.
you can see a picture of mine in the showroom section under "some pics of my ride"
(not sure on how to link you to there)

Probably the same aluminum ducting I came across at Menards when I was there pricing out PVC tubing.
It seems to be fairly sturdy, not like the flimsy dryer duct.

Sweepspear wrote:

I tend to fall into the trap of over thinking these things.

Paralysis from analysis.!!!!

I've never seen the stuff from Summit so can not comment on that. But for mine i decided to just open the existing air box up and use a flat K&N filter. I think the stock dimension filter provides enough air flow for the mod's I have.
I would like to add the air duct from under the car to the air box though. And that's cheap enough to do with hardware store supplies.

Rickw wrote:

Paralysis from analysis.!!!!

I like that! That is exactly what it is too!

Rickw wrote:

I've never seen the stuff from Summit so can not comment on that. But for mine i decided to just open the existing air box up and use a flat K&N filter. I think the stock dimension filter provides enough air flow for the mod's I have.
I would like to add the air duct from under the car to the air box though. And that's cheap enough to do with hardware store supplies.

Openng up the box, and adding a K&N filter I'm sure would be more than adequate for my car.
But since these filters cost what they do, I figure I should just go for the FWI.

Dale. find a pep boys.. they have 4 inch stainless steel intake parts.. i made mine for like 75 bucks with the filter.. you pay by the piece..

where did you get the 4" intake tubing @?

One source ($10): INTENSE Racing

I think I got mine from Jegs actually, but I remember it being a Spectre brand piece. I was very happy with it, and you can 'screw' it into the hole in the fenderwell to get it to just fit.

Hey IBx1 where did you find an iat extension for the 95? Is it the same as on the series 2 engines? also where did you place the filter so that it doesn't wiggle around or fall off in the fender well? does it reach until it is sitting on part of the body? thanks

I'm about to make one myself, however I have the ZZP 4" tubing and a 4" K&N air filter...what would be a good way to connect them together since obviously they can't slip on each other? Inside tubing or pipe that is slightly smaller then 4"? Or something to go on the outside of both parts?

If i remember correctly both the filter and the zzp tubing should be 4 inch inlet diameter. meaning they are the same size and that you will need to get a piece of hard piping like pvc that both of the tubing and the filter can slide onto and be fastened. The spectre tubing that Ilan and i bought came with couplers that could slide over it and the outside diameter of the coupler was 4 inches and could fit into the filter inlet. So basically the zzp tubing is larger because it is 4 inch inlet diameter and the spectre tubing is 4 inch outlet diameter. Hope this helps!

Here is a video that should help!

I finished building my Fender Well Intake today, very similar to the first post on this thread. I used 2 feet of the 4" intake tubing from ZZP, as well as a 4"x 9" K&N filter. To connect the tubing and filter I used a short piece of round HVAC ducting. Used roof flashing for the "base", and drilled a hole in it for the Air intake temp sensor. You need to move horn out the way for this large filter to fit.

I noticed a very nice improvement in pickup at higher RPM's and a noticebly louder whine/air noise.

Here's my plan. a 3.5" to 4" reducer off the throttle body. 4" flexi tube to the hole where the CAI used to be. tubing stops there and a 4" coupler will fit snug in the diameter of the hole in the fender well after the hole is expanded to size. half the coupler will be in the engine bay the other half in the fender well. The half in the fender will be drilled for IAT access. The IAT sensor will be extended. From there a 45 degree elbow will extend the coupler and be the final mount for the 4"x9" cone air filter.

My only concern at this point is the flexi tubing. Intense claims their tubing's " inside liner is .032" rubber and provides a smooth bore for maximum airflow and minimal turbulence." Which is what I want, of course. But looking at the picture provided:

it's hard to tell how smooth the inner bore really is.
I think a firm solution such as PVC or steel will have the smoothest inner bore. But hopefully this won't be so far off the mark.

Hard to say how much difference the flexible tubing will make. The fact that you are stepping up to 4" dia may offset the negative effects of the ribbing. Are you able to scan for MAF (not MAFF) using your torque app? Measure the amount of air entering your engine under full boost. Then after installing the intake, measure again. If there's an improvement, you've done well.

I like the placement of the IAT sensor. It looks like you'll be using rubber grommets, and that's a good thing.

Yes, I have been scanning and recording MAF since I got the car in November. I have plenty of numbers to compare with once I start scanning MAF with the new intake.

My main goal right now is to cool the IAT sensor the F out. That thing spikes so high when I park the car hot and takes forever to cool down. The only time I see good IAT numbers is in the first 10 minutes after starting the car from it's cold state.

Enough of that! I want those low low IAT numbers once and for all!

I highly recommend the Omega sensor. I experimented with the OEM sensor in the same location and found it was slower to adapt.

Thanks for reminding me. I was all about it when I first discovered the Omega but left it out of this project's details. Thank you!

Hey Charlie, just had a thought. Placing the IAT sensor inside the fender well might give optimum shielding from engine bay heat, but it also makes servicing the sensor more difficult. Once my sensor failed and needed to be replaced. It was nice being able to simply pop the hood and screw it out from the top side. The sensor is only a few inches higher on the tube, and still far enough from the TB to be free from heat soak. Just sayin'.

I haven't gotten so far to as to begin strategizing about the placement of the IAT and any features that would make servicing more convenient. But I can't help but wonder why the original engineering team did not make the Riviera this way from the factory. duh.

Does the sensor HAVE to be in the intake ducting? What penalties must be expected if the IAT is just mounted in the fender next to the ducting?

Really, they did a great job. When you think about it, the OEM air box is a fender well intake. We're just improving on their concept using some fabrication methods that wouldn't be cost effective at the factory. The average Buick driver (and pretty much everyone else) wants a design that's serviceable. Putting anything in the fenderwell that needs maintained really isn't a good idea from the serviceability standpoint.

Then there's the SC noise. Buick took great strides to keep the engine and intake sounds at ultra low levels. Putting a big cone filter in the fender well is great for performance, not so great for perceived luxury. And as John R. from INTENSE suggested, the engine bay offers protection from the elements. When you consider what most people expect from a $35k car, and that many don't perform even the most basic scheduled maintenance, it's easy to understand why they Buick did what they did.

Last thing: Buick didn't tune the IAT timing maps to take advantage of cooler air, so it's a wonder they even chose to mount the sensor where they did. I think there are other reasons for having the IAT be accurate. The AC for example won't work with the IAT disconnected.

I would not put the IAT sensor outside the intake tube for a couple reasons. First, the air filter protects the sensor from dirt and moisture. It will probably corrode faster if exposed to the elements, or it could become covered in debris. Second, we don't have any way to know if the air immediately around the outside of the filter will be the same as inside the tube, especially when driving at speed and dealing with pos/neg pressures under the car. It's probably about the same, but inside the tube we can be sure. Imo, there's no place better to measure IAT than after filter, as far ahead of the TB as is practical.

I was being facetious about Buick's engineering team, but at least they set us up for some easing modding!

I have seen those mini filters people have used to put over their IAT sensors. I agree, the best place for the IAT is probably inside the intake ducting but I can't imagine there being a major problem if you had the mini filter mounted next to the main intake filter.

You have me thinking about servicing and maintenance now. It's good to be a few steps ahead, right?

I probably won't even start digging into this project for a few more weeks. I will keep brainstorming until decisions must be made.

And we're back!

What size TB reducer do I want for a 4" intake? I have seen 3 to 4" and 3.5 to 4" and I have seen 4" intake tube clamped to TB. I want to go silicone reducer from 4 to the TB's OD. Can someone please confirm the dimension?