Musings on the AEM Bypass Valve

Adding the AEM bypass to the AEM intake will loose HP from turbulence created by its “abrupt” area change (Loss confirmed by AEM, but the exact amount is not).

The AEM (and other non-short ram) intakes pull their air close to the location of the stock air intake. The factory intake and aftermarket intakes, that are NOT equipped with an air-bypass device, pull all of their cold air from the same general area, near the splashguard. IMO, the AEM bypass valve opens a bit too easy. WOT operation allows hot air, at the top of the engine compartment, to mix with the desired cold air. If the air-bypass opens too easy, it means that it could actually hurt the car’s performance by pulling in super hot air – something the factory unit without air-bypass would never allow. (A stock CLS’ can succumb to hydro-lock, as a recent member can attest!) The hot air issue should probably be ignored by “freeway flyers”…

So hit the dyno and test. Right?

All of this could probably be sorted out with a dyno. However, the dynos are typically done with the hood of the car open. The “hot air” sitting near the underside of the hood (in real-world conditions) is not being simulated by “typical” dyno tests. A “typical” dyno session would NOT reveal the losses caused by hot air mixing with cooler intake air. The air temperature of an engine compartment can get rather hot (depending on length of idle, ambient air temperature, and other factors). For example, if only 20% of the air flow getting into a CAI was near 200-degrees, with the (lower) main opening pulling in 70-degree air, the effective air temperature would be closer to 96-degrees. Given the general formula that relates air density to air temperature, a drop of 40 degrees would result in a 6% gain in HP. 96 – 70 = 26 degrees would be equivalent to a 3.9 percent drop based on the data above. 3.9% * 200 wheel HP = 7.8HP drop! So, considering the gains that most people show on their dynos, the hot air mixing (caused from idling, hot day, etc) would totally negate the gains from the intake! Toss in the turbulence from abrupt changes in internal pipe diameter, and a 50-percent loss – compared to an unmodified AEM CAI – is possible.

Well, so what?

The temperature near the top of the engine compartment, during slow traffic or idling, can get rather high (especially on a hot day, in slow traffic). Here is a Miata forum posting on how hood temps respond to various influences (temp, speed, etc): http://list.miata.net/miata/1997-05/3156.html

Note: The under hood temperature data came from various “Googled” sources and range from 120 to 240+ degrees F depending on conditions. Feel free to juggle the 20% air volume contribution from the bypass valve. (Please, before you jump on me, be sure to see how easy the valve opens and how “leaky” it is. The flaps open with the slightest inhalation (you could breath through the thing, and you wouldn’t notice!).

$0.02

 

So, get a Cold Air Box...

 

I knew you would be along...

If I had it to do over, I would have gotten yours…

AEM, could have put a "circular slide valve" with an "Open" / "Closed" lever with detent, by the side of the valve, and this issue would be moot. (Think two circular bands with holes that would alternately line up (open to air) or not line up (closed to air) and that would have resulted in a minimal price increase, minimal turbulence, and a 2-second "mode change"...

But..... NOoooooooo!

Can you PM me on status, more info?

 

Good post and though process, Eric. I've yet to install my bypass valve (hell, I've yet to receive it!) When I do finally get it, I'll test as you stated. It sounds very logical it will cause a loss in power, no matter what AEM tells you.

I ran an AEM CAI on my civic for about two years (prior to the invention of said valve,) and never once had trouble. Of course I avoided high standing water at all costs, but that's plain common sense. I'll have to re-think cutting up my intake to install this little devil, as I really think that it sux it's not done at the factory for you!

Good work - Jim

PS - ooooh looky, post 333

 

I looked over on the Weapon-R site and got some helpful advise from moomaster_99

Notes:

$160 for the short ram alone (price found via link on Weapon-R)
$200 for the cold-air box (until 2002)
--------
$360.00 until beginning of 2002

After that time,

$160-175 for short ram.
$250 for cold-air box
-------------------------------
$410 - 425.

The AEM CAI plus bypass lists for $365, but Tim sells the combo for around $265. The price difference runs $5 to $100 (depending on vendor)!

Check the dynos between the two and the power gains and area are very similar. However, the Weapon-R has numerous advantages:

Maintainability:. Viewing and cleaning the filter is easy and can be done from the top. No more pavements licking to get at the splashguard for AEM filter inspections.

Excellent 4-season operation. NO chance of water ingestion (no bypass needed) *and* performance isn’t compromised by hot under-hood temperatures (as is the AEM with bypass).

Trivial installation:. Cold air box attachment with single bolt (that's the info I received).

IMO -- if this were available when I ordered my AEM CAI (months ago), I would have been on the phone, instead of writing this blurb.

$0.02

 

If enough of you guys buy it...I think that a group buy discount can be done...
email
leonow@weapon-r.com for info about a group buy.

 

Shit, mine sits RIGHT next to the engine. How do I go about testing it? If it's leaky, I'm going to rip AEM another AH!!!!!

 

Well, there is no real way to test it unless you are willing to sacrifice an engine in the name of research..

 

What you got is what you got....

They are built leaky by design... If you did the "suck on it" and "blow into it" test, you would find that it doesn't require much pressure to get the flaps to open. IMO -- I would have made the sucker to open at 1 PSI, but what do I know...

It does what is supposed to do. Nobody said they had to "come clean" with all of the other details.

It's called an air-bypass valve (not a loose power and bypass air valve...)

Please don't call, they were already responding with harsh tone and complaining about my inquiry and pronunciation of their moniker. Comment from AEM, "Why do you keep saying AIM, we ARE NOT pronounced AIM! I mentioned A.S.A.P vs. ASAP, but… they don’t like being called AIM (think acronym) in lieu of abbreviation = A.E.M.!!!! :rolleyes

(Shades of a recent car magazine critic...)

 

I dont have a intake with bypass valve, (want one though) but after reading the post. What if you tape over the bypass valve with tape, that doesnt leave crappy tape residue. And when its wet just take the tape off. It wouldnt elimintate the turbulence, but it would eliminate the hot air comming in. A better idea whould be to build some container our of metal, so tape doenst get sucked in by accident.

 

That gets rid of the heat (IMO -- biggest power loser)...

There is still that turbulence (sorry, no dyno figures available)...

You can (as AEM and friends-of-AEM suggest) replace the bypass valve with a silicone (or other) 3" hose. (Hose clamps not included) There will still be a little bit of turbulence (from the ledge of the pipe's inner diameter), but no hot air will be sucked in. I still wonder how the flex of the HOSE would impact the location of the K&N/AEM cone filter (with G-forces and vibration)?

Hmmm.... Do i want aluminum foil and duct tape hanging in the engine bay?

 

I may be interested in this. What is involved in the installation? How are the gains compared to the AEM CAI? How loud is it? Anyone have pics of one installed in our cars? Dyno plots? Thanks

 

Ok, ok. I just got my AEM CAI and bypass valve from LandSpeedRacing.com today ($247 for both and S/H). I haven't cut the damn thing yet. In your opinions, do I just install it w/o the bypass and cross my fingers while enjoying pure bliss in acceleration or cut the pipe and enjoy a little bit of blah. I live in Seattle (rain, rain, rain...)

 

If your thinking about hitting an intersection with water filled to curb level *and* want to power through with out a care in the world, just pop the sucker in (and do it soon)…

As I mentioned, you can always get a 3" rubber/silicone hose to replace the bypass valve in the summer.

AEM told me to remove the bypass if I was going to do any "track" runs...

Don't blow your engine on my account -- OK? Seattle can get awfully wet, but I don’t know how deep the water gets…

 

As posted in a previous message...the board rate is $300 for the Cold Air Box and intake + filter.

If you want just the box....$150 a piece with at least 10 people purchasing.

 

You have a PM coming in 2 minutes...

 

I sent one too!

 

Once upon a time when I was interested in Integra and over on site they talked about dynos that indicated 2-4hhp. loss on the 170hp. GSR. I live in a very rainy area and know the roads well. Have not encountered high water but if water over 12 inches would naturally turn around. I don't travel during the winter in my car but take my wife's car. Even with heavy rains got under car and examined my monster cone filter and it was completely dry! Since I have a custom CAI I could even remove lower end and install filter for a short intake but will only do so if it rains for 40 days and nights!

 

You guys are just a bit too paranoid about water.
I had my 93 Probe GT with a Hotshots CAI for a good 5
years in Washington state with no problems. I had no
inspection shield and the filter was literally the lowest
point on my car. I would clean my filter every month
because it would be so covered in dirt... and my pos
ford probe NEVER had a problem. Remember, think of
it as a straw... you're not going to pull water except for
COMPLETE submersion. Ram Air Intakes, like on the
firebird and trans am pull more water into the intake
then we ever will. I say, skip that cheesy bypass and
don't drive your cars into swimming pools, small lakes
or the ocean and you'll be fine.

 

what about drops of water, I mean if the filter gets wet a little, and it sucks in some drops of water, will that kill the engine ?

 

If my memory serves me right, back in the days of my Prelude and CAI worries, drops of water will not damage your engine. First of all, the droplets have to make their way up the tube, which is not straight. Secondly, the few droplets that do make it into the combustion chamber, will be vaporized during the combustion process and heat.

So, to answer your question, no, your CAI will not damage your engine if it gets a little wet.

 

Just to allay your fears, I can assure you that "drops of water" or even a small continuous stream of water will not hurt your engine. I installed a number of water injection systems on 1968-1975 model cars with very high compression ratios.

The stream of water -- at wide-open throttle -- looked like the stream from one of those "super soaker" kiddy squirt guns!

 

95% of cases where people think they got hydro lock from their intake
is usually someone bs'ing them or a headgasket leak into the cylinders.

 

I'll chime in too.

In the two years I had my 89 Civic Si with an AEM CAI never did I encounter a problem with water intake. This was well before the invention of the "bypass valve." The car was low to begin with, and for most of it's life it rode on Neuspeed sport springs. The car was very low at that point.

Rain, snow, you name it, she ran like a bat outta hell. I did of course avoid large standing water encounters (this to me is just plain logic.) The filter really never got all that dirty for that matter. I usually checked it about once a month.

I've got a bypass valve coming (ordered with the CAI, before this thread started.) But when it finally gets here, it's staying in the box. It's been raining pretty good here in Ohio lately, and I'm not having any issues. Again, trying to surf the lakes in my CLS is not going to happen, but I wouldn't consider doing that with the OE setup either!

Let the paranoid people rest. It's really a common sense while your driving thing here. Don't get yourself in a situation that's iffy. Not that you can avoid it 100% of the time (flash floods, etc.,) but for the most part it's not an issue (at least for me.)

Jim

 

Ok, I will add my $0.02 too. I had the Hotshot intake on my 94 Probe GT. When I first bought it I too was paranoid about it so everytime it rained I would remove the pipe and just put the cone filter on. After awhile I got sick of doing that so I just drove with it on and did the cone filter thing in the winter. Never had a problem with sucking up water but the filter did fall off while I was driving once, I hit a pothole and it just flew off I watched as a couple cars swerved out of the way. I had to run across 3 lanes of traffic to pick the damn thing up, man to be young and stupid again...

 

Autophile1 - Holy crap!!! Talk about a freakout sight! I bet you about shit your drawers seeing that filter bounce across the pavement. That's hillareous.....

 

Well, put...

I've wasted some money (I could always use a spare K&N) *and* I won't be putting the bypass on (well, at least the one with the "current design). I'll just use some prudence as I try to *and* if I'm in some deep water (still below the bumper) I will drive "her" very slow...

Live and learn.


moonmaster_99: Just how bad is the UFO sound? Is there a sound clip and/or can you elaborate on this... (Does it happen at some speeds, high speed/WOT, and/or under any other conditions...) I hope you test the upcoming RES with the intake -- this would be very interesting!

 

EricL- Could you please give me some intelligent insight to my situation http://www.acura-cl.com/forums/showt...threadid=55753

I'd really appreciate it....

TIA - Jim

 

The UFO sound is pretty loud...it's only at idle...hmmm...lemme see if I can put a sound clip on.

 

http://www.acura-cl.com/forums/showt...threadid=55799