Debunking Edelbrock's Air Gap Intake **UPDATE!!!**

[Aussie XAXB]

First, I like Edelbrock but nobody is perfect. I just want to get out some info about this  before anybody interested in this intake makes a purchase.



Edelbrock's big selling point about the Air Gap is that the runners are raised from the part of the intake that is exposed to "hot engine oil" of the galley and this is supposed to be responsible for the intake charge being cooler and more dense as opposed to a typical intake manifold. That sounds good but now let's consider the metallurgy aspect of it.

Aluminum is highly thermal conductive. This is one reason it is used in some wiring and why practically every heat sink ever made is constructed out of aluminum.

If you hold a piece of steel and heat the other end with a torch the hand you are holding it with will be fine. However, if you heat a similar piece of aluminum with a torch at one end while you hold the other you will very soon be dropping it to the floor as the heat migrates to the end that your hand is at.  That is due to the thermal conductivity of the aluminum.

Suffice it to say, whatever temperature your cylinder heads are is the same temperature that your Air Gap will be since it is aluminum. Also, the heat from the oil in the galley that is supposedly isolated from the runners also contributes to heating the rest of the intake. The metallurgical properties of aluminum make's Edelbrock's claim bunk. Also, heat rises so whatever heat is below the intake also comes up to it.

I thought perhaps that the angle of the runners would make it an ideal intake as a high rise intake. However in a recent article, in one of the "regular" magazines, it shows in a comparison on a dyno that the Air Gap compared to a Performer RPM only had a difference of about 1 to 3 horsepower, sometimes in favor of the Air Gap, sometimes in favor of the Performer RPM depending on engine RPM. So there is no advantage there either.

One situation where it might be advantageous is in drag racing. I have heard of people placing a bag of ice in the gap of the intake. Now you have cooler air!!!! But for daily driving I see no gain.


Steve

[W.O.T. Stang]

It's good to see that people like you actually sit and think things like this out.  I would have never thought about that until you mentioned it (Not just the air-gap intake, but all parts in general.)  Otherwise, you could listen to what they say, be fooled and think you have an advantage when you really dont.  Thinking for yourself is what more people need to do.  The world would be a lot better (and smarter) place.

The people who win at the races, are the ones who plan together their own combinations for what they want to do with it, not just build the same setup as his buddy.  If everyone has the same setup, how are you ever going to win!

Excellent writeup though.  Definitely made me think about how different "horsepower techniques" may help or hurt you, and how I want to plan any kind of buildup in the future taking the metallurgy into effect.

[Aussie XAXB]

Hello Jim,

Well thanks for the kudos but I think you are giving me more credit than I am due. I am a Toolmmaker and have some metallurgy education as it applies to my occupation. I also have to apply what I know and what I continue to learn on an almost daily basis. While talking with one of the guys at work about cars he brought up the Airgap and mentioned how many magazines were doing their build-ups with it. I decided to look into it and the first thing that occured to me was the aluminum ramifications in the goal that they were trying to achieve. On top of that I happen to stumble onto the dyno test with that manifold while the article I was reading actually dealt with another engine aspect. I was actually surprised that the Airgap didn't flat outperform the Performer RPM if not only by 10 HP on a regular basis.

I am glad someone is able to benefit from my post though. I agree with you exactly; how is anyone going to do any better at the track if everyone does what the next guy (or girl) is doing? ( I didn't want Michelle to kick my but for not including the ladies )

I ask around for input on certain parts but I use that info to put together my own set-up. I didn't include ALL my plans for the Mustang engine in my "Ride" page.


Thanks again,
  Steve

[Freakingstang]

You do bring up a couple good points Steve.  What article/buildup/ comparison are you talking about between the RPM and the airgap?  I don't think I have seen that.  I've run the RPM and the Weiand Stealth in the past.  I had better results with the stealth handsdown.

[Aussie XAXB]

I've been going around the house collecting up all the magazines trying to find that article. I'll let you know.

What was the rest of your set-up and your goal with the Stealth intake? Did you get good low end with it?

Steve

[Aussie XAXB]

I found the magazine article! Geesssh. It is in the summer issue of Hot Rod's "Engines" magazine issue it prints periodically. The article is where they are trying out several different cams in a 347 stroker motor.

*Announcement*
My bad in the Air Gap vs. Performer RPM intake. Actually they had the Performer RPM II intake on the engine which is the 5.0 style FI intake, not the carbureted Perfromer RPM intake. The Performer RPM II FI intake compared to the Air Gap carbureted intake showed virtually no difference between the two in performance. The intakes (and of course throttle body and carb) were the ONLY change in the comparison. This will give you an idea how close the two were. Dyno results started at 3,000 rpm......

3000 rpm
RPM II HP 223 TORQUE 389
AIRGAP HP 228 TORQUE 398

3300 rpm
RPM II HP 255 TORQUE 406
AIRGAP HP 254 TORQUE 403

4000 rpm
RPM II HP 316 TORQUE 415
AIRGAP HP 317 TORQUE 416

4500 rpm
RPM II HP 368 TORQUE 429
AIRGAP HP 371 TORQUE 432

5000 rpm
RPM II HP 415 TORQUE 436
AIRGAP HP 410 TORQUE 430

5600 rpm
RPM II HP 444 TORQUE 416
AIRGAP HP 443 TORQUE 415

Now admittedly, to me since I am an old school carburetor guy (I worshipped the Mopar 6-pack intake on a 440) this illustrates to me that the fuel injected guys, and gals, don't necessarily have anything over the old carbed guys when it comes to what is happening at the flywheel.

As fuel injection gained in popularity on factory produced American made cars it was believed, and most likely accurately so, to have an advantage due to more precise fuel metering and the fuel being injected right at the intake valve. I would have to believe though that there is more accurate fuel metering going into the engine for fuel economy and emissions purposes with the fuel injection.

But as far as a power advantage, with the elaborate 5.0 FI intake design, throttle bodies, and all the expensive electronics that goes with it, there would seem to be none. So for me and my dollar, where legal, I would prefer to bolt on a carb, toss the electronics, and have a ball without worrying about giving up any performance in a street or street/strip car.

Sorry for the inaccuracy of me believing the article compared the carbed Performer RPM intake against the Air Gap. I would still love to see a head to head (or intake to intake as is were) comparison of these two carbed intakes. Maybe there is an advantage for one or the other??


Steve

[TireSmoke]

gotta love having a huge hole on your hood blowing cold air on your intake, while the hot EGR gas is being blocked by your 3/8" spacer.  My upper intake stays stone cold on trips

[Aussie XAXB]

Got a pic of your hood?

Steve

[TireSmoke]

tons.

[Aussie XAXB]

Now that is nice!!!! Cool that it is functional too.


Steve

[quake101]

[tmoss]

Suffice it to say, whatever temperature your cylinder heads are is the same temperature that your Air Gap will be since it is aluminum. Also, the heat from the oil in the galley that is supposedly isolated from the runners also contributes to heating the rest of the intake. The metallurgical properties of aluminum make's Edelbrock's claim bunk. Also, heat rises so whatever heat is below the intake also comes up to it.


Steve

But if you can get some cooler air flow over the intake, you might run a cooler air charge.  Like using a ram air hood such as depicted above and letting the air flow over the intake to cool it?  Only works at speed though.

[TireSmoke]

its also a big friggin hole in the hood that lets the engine compartment breathe a lot more....the stock hood is like an oven!

[Aussie XAXB]

The hood pictured above, regardless of marketing, does not actually provide a ram air effect. With ram air the air is forcefully pushed into the scoop. But due to the aerodynamics of the hood, particularly the leading edge, the air flow is just a few inches above the hood so there is no real ram air effect. That is why drag racers use the style of scoop pictured below.



It is up above the hood and in the main airstream flow. True, if you have an intake connected to a hood scoop it will be getting cooler air than the underhood air, but no ram air effect. Another place that true ram air is harvested from is by ducting to the radiator support (one with big holes in it of course) and getting the air that blows through the grill, provided you have a car that has a sizeable grill.

In anycase, unless you have a tall scoop that is up in the airstream you are not getting "ram air" and any air brought in from outside the hood will not be enough to have a cooling effect on the intake, though it is more advantages than sucking hot underhood air into the engine........but you don't need an Air Gap for that.

To a lesser extent you can get a ram air effect with cowl induction, but this is not as forceful as true "ram air".


Steve

[tmoss]

The hood I mentioned is tall enough to get airgflow through - how much is just a guess on anyone's part.  How much qualifies as "ram air"?

[Aussie XAXB]

That is a really good question. Where is that line drawn? I don't know. But I usually think of air blowing in your face kinda force when I think of ram air. In anycase, use of that air in the air/fuel mixture is the best benefit of it. If its not used that way then just to vent the engine compartment has to be a good thing.


Steve

[TireSmoke]

I'll tell you first hand.....under hood temperatures and upper intake temperatures while cruising are WAYYYYYYYYYYYYYYYYYYYY lower than stock.  Before I even disabled the EGR and put on my spacer there was a extremely noticable differene with how hot the engine was right after a drive and how fast the engine cooled off after driving.

While my style of hood may not be optimal for ram air it does cool the HELL outta the intake.  Drive 200 miles, pull over and feel your intake.  I bet it burns you.  I can drive 200 miles, get out, and the intake is comfortable to put your hand on.  I dont have any kind of ramp air setup on the vechicle....it was mainly cut out for the cooling effect and looks.

my two cents on the subject.....

[Aussie XAXB]

Sounds like you are getting your money's worth. 

Steve

[Lee8995]

Yes aluminum conducts heat very well but it disipates it much faster than cast iron so the disadvantage due to heat soak you speak of doesnt really play as major of a role as you might think. With the air gap design it will disipate more heat because it has more surface area exposed(same idea as a heat sink) thus the intake is able to exchange heat with the outside air much faster and more efficiently. Also its better to use dry ice to cool the intake between rounds, Pull into the staging lanes with some previously melted ice dripping from under your car and see what happens    

[Aussie XAXB]

If you've got a serious scoop that is moving a significant amount of air into the engine compartment there could be some good dissipation, but otherwise the only air moving around the intake is the heat rising from the engine, heated engine compartment air. If there were enough of an effect it may have shown on the dyno comparison referred to in a previous post, but its not there. The Air Gap / Non-Air Gap combos flip flopped at various RPMs an advantage of 1 to 3 or 4 HP and lb ft of torque, negating be ability to make any claim of an advatage due to intake manifold design.

Physics are what they are. Marketing is motivated by greed.


Steve

[tmoss]

That's why I noted the cooling effect would felt "at speed" and there is no speed on a dyno.  Even an open hood and a fan aimed at the car front is not gonna cool the intake much at all.

[Aussie XAXB]

Agreed. 

[NUTTSGT]

Functional or not, ( I believe it helps with cooling) I think Tiresmokes hood looks good.

[Aussie XAXB]

It is a kickass looking hood. 

Steve