Cold air intake vs. K&N Air filters for Weber DCOE 45s

[z boy mn]

Hey everyone, I have a car now with a cold-air return on it for my triple webers, 3.1 stroker motor. Runs great, plenty of pull, all good. But, the air box hits the hood, so I've been considering just changing over to individual filters that mount to each carb.

I know the cooler air helps, especially as the carbs sit right over the header, but I'm not sure how much. Is it worth building another air box? (The current one has other issues, too, like it leaks, has too many screws, messed up gasket, so I'd have to start over.)

Top performance has some filters that would allow me to use my horns still, so the air coming into the carbs would still be streamlined. How much is the "cold" air worth to the engine?

http://www.classiczcars.com/forums/attachments/open-s30-z-discussions/65515d1377530600-mechanical-throttle-linkage-whats-probl

There's the airbox as it is now...

[gnosez]

I had the TWM cool air box on my triples which has the inlet in the front (cone filter fitted via hose from in front of the radiator). The box was slanted so that it became smaller towards the rear (designed so air flow stays constant which a equal sided box will not do).

All that means nothing on the dyno when it lost nearly 15 hp over the ITG filter set-up (single large unit).

However in real life the hot air in the engine bay may cause a decrease equal to or greater than a cold air box.

I have the box and need to put it up for sale.

3.2L NA making 358hp@crank, triple 44 Mikunis, yada, yada

Edited February 6, 2014 by gnosez

[Zed Head]

Hot air under the hood is likely when sitting but has anyone actually looked at air flow and temperature while driving? The air through the radiator has some extra heat energy but at speed it seems like most of the air flowing through the engine bay is excess and probably at ambient temperature. Hot air in to the intake probably only happens at stop lights. It may also happen on the dyno unless they have some really good fans. Measuring the temperature would be a little difficult since a probe could pick up radiant heat also. It would have to be in the intake opening to really know.

Just thinking. I've always wondered about this when I hear about underhood temperatures and cold air intakes.

[Zedyone_kenobi]

For any normally aspirated car, for the most part, looking for huge gains in intakes, is a waste of time. AS long as their is not a huge restriction I would buy would will provide the cleanest air, and what is easiest to service, and what looks the best. IF you net 2 HP more from a cold air set up, you will never notice it.

I have chased Cold air intakes on other cars for years, and most of it is placebo. Go with what you like, and makes you smile when you pop the hood

[Stanley]

My engine is closer to stock, but I wanted cooler air for trips to the desert. There are those two round holes about 3" diameter on each side of the radiator. One gets air into the engine bay, the other has a plastic connector for the interior vent. I pulled off the plastic and stuck a shop rag in the vent to get more air to the engine. When it's 115F the air coming out of the vent is hot anyway.

Seems like it would be easy to improve the setup with some large-diameter flex tubing to direct the air to the air cleaner or that general area. Also seems like having a cone-shape air funnel in front of the holes (pep boys sells them or else improvise one) would get still more air flowing. It would take some thought for it to not look crappy.

That air box looks nicer than a lot I've seen, maybe just modify it.

[z boy mn]

Thanks everyone for your suggestions...I love the idea of all this extra HP the cold air is generating, but I'm just not sure it's a reality. I've seen the math (see

Engineering Explained:

) but...

Right now, the air box is a real pain to work with, but at the same time it helps hold the heat shield under the carbs in place...my original plan was to build something like this:

http://www.classiczcars.com/forums/attachments/carburetors-s30/22848d1209041965-some-triple-weber-pics-car%2520shows%2520084%5B1%5D.jpg

If I dump the air box, I'll have to come up with another heat shield...one that doesn't rattle.

I also did some thinking about how the air gets into the airbox. The photo doesn't show it, but in the front there's a flexible hose that connects to a filter in front of the radiator, but gnoze points out, unless the airbox is shaped properly, it seems the air inside the box won't be equally distributed.

Gnosez do you have any photos of your airbox? How did you figure out its dimensions? I'd be interested in it if you want to PM me.

With individual filters, I also like the idea of flowing in fresh air...hmm...I'll think about that some more. Maybe some kind of funnel...

As for individual filters, those little air horn filters look super cool, and they don't take any room...but I wonder if they filter well enough.

Weber Redline Air Filter Assemblies

Questions questions!

Edited February 6, 2014 by z boy mn

[Zed Head]

Post #6 here looks fairly non-restrictive, but is not "cold air" - Carbon Fiber Weber/Mikuni Velocity Stacks - Vendor's Forum - HybridZ

[gnosez]

TWM-Air Filters-TWM Air Box

ITG Air Filters - performance air filters for road and race vehicles | Megaflow Introduction

ITG Air Filters - performance air filters for road and race vehicles | itg E-Catalogue

Box requires the use of much shorter velocity stacks which can reduce HP. Slightly shorter and quite expensive stacks are the thing to have for the ITG filter.

Edited February 6, 2014 by gnosez

[z boy mn]

Thanks for the links...I love the look of those carbon fiber horns. But, I bet those are out of my budget...just like the Top End Performance box, which looks great. I am thinking maybe I can borrow the dimensions to adjust the squareness of my box...might increase the air available to my rear carb if I stick with what I have and tweak it some. Also, I know it's sheer vanity, but I'm not crazy about the "look" of the ITG filters...I'm sure they work well, but if I go with singles I think I'll stick with the KN kind. There's a lot of muck on the roads here in MN, especially in the spring, and it seems like they'd just absorb every bit of it like sponges.

It's hard to imagine all the air they need is able to come through a 3" tube, but of course that's where it leaves, so maybe it's just fine in terms of breathing.

[madkaw]

Next time I get to the dyno I am going to do a comparison or atleast see if my box costs me HP.

Probably more bling then anything, but this was my option over the TMW box.

http://www.classiczcars.com/forums/carburetors-s30/44244-cai-triple-mikunis.html

[John Coffey]

I've put air temps sensors in the engine bay of a S30. The underhood temps are within 5 to 10 degrees of ambient at any speed above 20mph, except withing 6" of the radiator exit. By design the underhood air exhausts down under the car at road speeds. On my race car I ran a cone filter in front of the radiator mainly for packaging reasons (custom intake manifold with the throttle body at the front) and because that cone filter would be about 2" from the radiator exit.

[gnosez]

Just for Ss & Gs it would be interesting to put in several TCs (thermocouples) within the engine bay and one in the air intake (hose from in front of the radiator and then run a test without the hose).

The loss in HP was determined after an engine with different air filters were run on the dyno at Rebello's. Dave also noted that the Pace exhaust was needed for higher HP engines (300+).