Intake fix on the E28

"HoustonRunner" (houstonrunner)
08/31/2020 at 12:42 • Filed to: None

One of the main cosmetic items that has bothered me since buying the E28 (just over a year ago now) has been the intake. It has the right intentions but Home Depot execution. Here is what it looked like before this weekend.

Stock airboxes are around, but not necessarily cheap for ones in good shape. I wanted to keep the “cold” air for now, maybe go back to stock later. Once again I enlisted the help of my brother in law.

We set off Sunday afternoon to the local auto parts store in search of some aluminum tubing that would work. The general plan was to find 15" or so of 3" tubing, then figure out the rest. We found a “Spectre” brand intake kit that was just about right. It took a few attempts, but we were able to find the right fittings and location to get it installed without having to bend the tube. There are a couple of ports on it, which I assume are for either mounting or a temp sensor, we put one to use as a mounting point.

The original “cold air” surround was cheap galvanized metal that literally looked like it was taken from a bucket. Using some aluminum sheet metal my brother in law cut and bent a new surround, and we mounted it to the side and front of the engine bay.

It doesn’t look perfect, but I think if I paint the aluminum a flat black it will blend in better with the rest of the engine bay. And it looks miles better than the dryer vent tubing that was in there when I bought it.

Easily +5hp. Now if I only had an Oppo sticker for another 5hp....

DISCUSSION (17)

onlytwowheels > HoustonRunner
08/31/2020 at 13:00

There is a common belief that metal tubes hold more heat. This will raise the temperature of the intake air. Therefore, plastic tubes are better because cold air makes more power.

The temperature theory is not necessarily wrong. However, the temperature difference is so small that it won’t make a difference in most cases. The reason plastic (and rubber, and carbon fiber) tubes are generally better is because of their shape.

Metal tubes are much better than the restrictive factory intake of most vehicles. But, the shape of metal intake tubes is limited. The tube can only be bent and welded so much.

Plastic and other materials are molded into shape. Often times, this allows for a more efficient air path.

Plastic tubes can be made less restrictive. This makes it easier for the engine to breathe, speeds up the incoming air, and makes a little more power.

This is what we'll show whenever you publish anything on Kinja: > onlytwowheels
08/31/2020 at 13:19

Iirc metal will heat more quickly, but also cool more quickly. Plastic will take longer to heat soak but once it’s hot it retains the heat and doesn’t cool as quickly. So while both might heat up while sitting at a light the metal will tend to drop temp rapidly once it starts getting more airflow, thus giving more power. The plastic will stay hot longer, thus reducing performance in comparison.

But this isn’t a racecar and in practice I somewhat doubt anyone would notice a difference if the materials were switched back and forth unbeknownst to the driver.

onlytwowheels > This is what we'll show whenever you publish anything on Kinja:
08/31/2020 at 13:29

All true. The aircraft ducting that w as replaced was possibly the better choice though.

Heat shielding around that aluminum tube would be beneficial and look the part.

Kinja'd!!!

HoustonRunner > This is what we'll show whenever you publish anything on Kinja:
08/31/2020 at 13:32

Agree on all points above (I still have some recall of fluid dynamics and thermo from college ). In the end I’m pretty sure this results in better airflow than stock and at a temperature that is about the same or slightly cooler.

Overall I expect to have more of an impact in driving dynamics with the 3.26 to 3.63 differential conversion I’m planning.

RacinBob > This is what we'll show whenever you publish anything on Kinja:
08/31/2020 at 13:34

Oh,,,, Metal transfers heat more efficiently than plastic, so all things being equal plastic is the better material for a cold air system. For example, I would rather have plastic gloves instead of metal ones if the goal is to keep my hands cold. I don’t think thermal mass is a deal as long as everything warms up to equilibrium .

Now, If we want to split hairs, the one thing about metal is that shiny metal is reflective so it will have less radiant heat absorption. That is probably not a big deal unless the tube is next to the exhaust manifold.

As somebody else pointed out, a smooth tube has better maximum flow than the rough ID corrugated drier hose.

Arch Duke Maxyenko, Shit Talk Extraordinaire > HoustonRunner
08/31/2020 at 13:48

https://www.redbubble.com/i/sticker/Oppositelock-The-Logo-by-Maxyenko/43021303.EJUG5

HoustonRunner > Arch Duke Maxyenko, Shit Talk Extraordinaire
08/31/2020 at 14:41

I forgot the stickers were there....order incoming.

Remind me - have you ever done a BMW E28?

HoustonRunner > onlytwowheels
08/31/2020 at 14:45

I do have some heat wrap tape that my brother in law tossed at me as I was leaving. Maybe that instead of paint?

Arch Duke Maxyenko, Shit Talk Extraordinaire > HoustonRunner
08/31/2020 at 14:48

Not in Inkscape yet, but I could try to redo this one without BMW logos on it so it doesn’t get pulled

https://oppositelock.kinja.com/this-will-be-the-last-shoop-for-a-while-1786739027

onlytwowheels > HoustonRunner
08/31/2020 at 14:54

Are you refer ring to the exhaust wrap stuff, or reflective gold stuff?

Or something else?

Kinja'd!!!

HoustonRunner > Arch Duke Maxyenko, Shit Talk Extraordinaire
08/31/2020 at 14:58

How about from a picture? M5 is nice, but I’d prefer my more pedestrian 535. And I’m cool with no logos.

Arch Duke Maxyenko, Shit Talk Extraordinaire > HoustonRunner
08/31/2020 at 15:01

Largest Hi-Def picture you got, or just google one

HoustonRunner > onlytwowheels
08/31/2020 at 15:06

Pretty sure it is exhaust wrap, definitely black not reflective, and didn’t look at carefully at it.

onlytwowheels > HoustonRunner
08/31/2020 at 15:16

Use it on the exhaust manifold. It will keep the heat in the exhaust and lower the under hood temp.

HoustonRunner > Arch Duke Maxyenko, Shit Talk Extraordinaire
08/31/2020 at 15:55

This is definitely my favorite picture. Just the outline (similar to the M5 one) on a light blue shirt I think would be great (but also, you are the creative one, so what do I know?). If kinja posts it in too low res, I can send you the original.

Kinja'd!!!

Arch Duke Maxyenko, Shit Talk Extraordinaire > HoustonRunner
08/31/2020 at 15:59

You want a US spec and not a Euro spec? Can do either way.

HoustonRunner > Arch Duke Maxyenko, Shit Talk Extraordinaire
08/31/2020 at 16:07

That is a tough one....mine clearly has the diving board bumpers, but if someone handed me a set of Euro bumpers I’d ditch the US ones in a heartbeat. Euro spec, if definitely looks better.

Off to search for a set of Euro bumpers for a price I can slip by my wife....