"The Confines of the Engine Compartment"

G

Greg Amy

Administrator
Staff member
GCR 9.1.3.D.1.a.4 says, in part, "Air intake source shall be within the confines of the engine compartment or stock location." Define "the confines of the engine compartment".

GCR Technical Glossary (Appendix F) defines "engine compartment" as:

Engine Compartment – The loosely defined volume, nominally enclosed
by panels on top and sides, which is the normal location of the engine in
a car.
​

"Loosely defined", indeed. Question is, how loosely?

"So where's he going with this?" you may ask. I had an email exchange with someone, asking about the compliance to the ITCS of the Jackson Racing intake system for the Miata. He had seen it in other Miatae for sale and wanted to know if he could install it on his own car. Photo, installed:

http://www.miataturbo.net/attachmen...-cold-air-intake-90-93-1-6-miatas-2u5q0ox-jpg

This appears to pull intake air from above the radiator support. At first glance, I'd call it non-compliant, however nowhere is there a clear delineation of "engine compartment" for the front or bottom, and in this particular case the "top" is the hood, and this parts sits under that.

We briefly touched on the subject in the 2008 discussion of the ARRC CRX fender well intake protest. Within that, we recognized that there was some ambiguity, but never truly delved upon it.

Stock 1.8L engine compartment:
http://carphotos.cardomain.com/ride...r.com/~chrisaj/archive/miata/miata_engine.jpg

Stock 1.6L engine compartment:
http://www.practicaltech.ca/jpg/auto/miata/miata_engine-bay.jpg

Since the top of the "engine compartment" is inferentially defined by the Technical Glossary as the bottom of the hood, and this part fits within that without modification, isn't anything under the hood part of the "engine compartment"? If so, where does that allowance end in the forward direction?

And what about "prohibited function"? The regs clearly indicate that pulling air from outside the "engine compartment" is clearly prohibited, and the regs further clarify that you cannot run a minimal radiator to make open space to route air to the engine intake. But what if you are not modifying anything to grab air from that area?

About the only thing I can suggest is that it's non-compliant because the "engine compartment" definition in the Glossary states "the normal location of the engine in a car", and there's no way that the area above and in front of the radiator is a normal location for the engine. But it's not clear where that "normal location" definition ends, nor is it clear if that definition changes based on make/model (and if it does, then any space that the engine does not "normally" occupy - basically all the clear space around the engine - would not be allowable places from which to source air.)

Is it the aft edge of the radiator? Does that change with the allowed radiator design change? Is it the aft edge of the radiator support? Of the forward edge of the rad support? And if that part were trimmed back an inch to that plane, but still pulled air from above the radiator and radiator support, would it then be compliant?

I'm torn. Without using much intorturation, I see how this could be allowed, as-is.

I'm sure no one else on this board will have a strong opinion on it, but figured I'd ask anyway...

GA
 
dickita15 said:
I must admit i am uncomfortable with the intake breaking the plane of radiator.
Click to expand...

Fair enough. So look at that photo of the item installed again. Note that the piece that extends well past forward of the radiator is the mounting system, and there's no limits to the mounting system for the air intake, only limits to where the air is sourced. If he were to trim back the top of that item, where the initial opening of the air source is, to a point right at the vertical plane of the aft edge of the radiator, would that not satisfy the letter (and potentially the intent) of the reg?

GA
 
<johnbishop> It's illegal. Period. </johnbishop>

Kirk (who freely admits that combining obtuse references to both html and '70s-era IMSA is probably leaving pretty much everyone out of the joke)
 
I have no problem with it. Unless you are going to mandate bone stock air filters and housings, it works.
 
I think I may have accidentally discovered where the item is moot, regardless of compliance.

Look again at that photo of the stock 1.8L Miata. Note that there's a plastic cover over the area on top of the nose, in front of the radiator. This Jackson Racing part pulls air from that area when that cover is removed, and I cannot think of any way where removing that panel is compliant to the regs. Therefore, even if that intake is compliant, I don't think it's nearly as effective unless another non-compliant mod is also done, negating the whole point.

The 1.6L Miata seems to be open there, so may be useful for that car.

Agree/disagree?

GA
 
Wouldn't that air intake be considered ram air and therefore not be allowed? "Velocity stacks, ram air or cowl induction are not permitted unless fitted as original equipment."

 
Ralf said:
Wouldn't that air intake be considered ram air and therefore not be allowed? "Velocity stacks, ram air or cowl induction are not permitted unless fitted as original equipment."
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I don't think so. In my mind it's clearly not velocity stacks; doesn't meet the definition of cowl induction (nowhere near the cowl); and ram air IMO requires facing the perpendicular flow of oncoming air.

One can argue that there is increased air pressure being created in front of the radiator due to forward motion, and this intake system takes advantage of that. I disagree; I suggest that since that area in front of the rad is way wide open with numerous holes all around, any pressure increase is minimal, if at all (and would be tough to prove regardless). Lack of significant increased air pressure negates the idea that it's ram air.

Good thought, though.

GA
 
I have always considered the engine compartment as a place where the engine resides. Clearly, the engine does not reside in front of the radiator, therefore, the engine compartment ends with the rear of the radiator. Non compliant.
 
I have never considered that intake to be legal for an ITA Miata. I believe, like RP, that anything flush or encroaching on the plane of the radiator sources from 'outside' the bay. That's oversimplified for sure.
 
Andy Bettencourt said:
I have never considered that intake to be legal for an ITA Miata. I believe, like RP, that anything flush or encroaching on the plane of the radiator sources from 'outside' the bay. That's oversimplified for sure.
Click to expand...

chuck baader said:
I have always considered the engine compartment as a place where the engine resides. Clearly, the engine does not reside in front of the radiator, therefore, the engine compartment ends with the rear of the radiator. Non compliant.
Click to expand...

+1
 
I tend to agree with the above. However, re-read my post from above and tell me what you think...we're talking only an inch difference here...

Greg Amy said:
Fair enough. So look at that photo of the item installed again. Note that the piece that extends well past forward of the radiator is the mounting system, and there's no limits to the mounting system for the air intake, only limits to where the air is sourced. If he were to trim back the top of that item, where the initial opening of the air source is, to a point right at the vertical plane of the aft edge of the radiator, would that not satisfy the letter (and potentially the intent) of the reg?
Click to expand...
 
The advice I'd give to that person is that it's quite debatable whether that intake is legal or not. They should also further look into whether there are truly any gains to be made. Then based upon those pieces of information, decide whether or not the hassle is going to be worth it. I looked into it after seeing that intake at Summit Point on the way back from picking up my Miata. I then spoke with ISC and a few other companies. I don't think that is a better option. I do know that every time I raised my hood in impound (do often regardless of whether or not required to), it would cause questions. Then questions about what else might I be doing too. It's also an easy protest that I have to imagine would come with a small protest bond fee. Curious, what do you think that would be?

After this simple protest is filed, it's then going to be a debate amount the powers that be just as being done here. Maybe found illegal then move on up to National.

Back to the real question, it sure looks debatable and right on the edge of the rules if it's not illegal.

That plastic cover near the rad. All year 1.8s have them? I don't recall ever seeing one on a Miata. I'll admit you made me go outside and take a look at mine. It's not there. For cooling purposes, I'd almost think it would be better to have it. My intake is not in that area and don't think there's any impact.
 
>>> It's also an easy protest that I have to imagine would come with a small protest bond fee. Curious, what do you think that would be?

Nothing, just the $25 protest fee. Bonds are collected to cover the expense of any destructive inspections (e.g. engine tear-down) to reimburse the protestee if found compliant. In this case, there are no such costs.

>>> After this simple protest is filed, it's then going to be a debate amount the powers that be just as being done here. Maybe found illegal then move on up to National.

After the protest is filed, the Chief Steward will form an SOM to discuss the issue. They may ask for feedback from ITAC/CRB members. At that point they will present their decision. The protestee at that point can file an appeal to Topeka, at which point an Appeals Court will be formed to review the issue.

>>> Back to the real question, it sure looks debatable and right on the edge of the rules if it's not illegal.

Concur. Which is why I brought it here (with the permission of the original questioner.)

>>> That plastic cover near the rad. All year 1.8s have them? I don't recall ever seeing one on a Miata.

Yup, but it's a commonly-lost item. I think it's held in by a couple of plastic clips that are easily broken/brittle from time. Since we can replace the radiator with a sufficiently-large one, it's quite possible an advantage to 1.8L Miata drivers to "leave it lost" and allow cooler air to come into the engine compartment...probably a "weenie protest" item, unless coupled to something like this intake...but technically non-compliant.

GA
 
I think you have to also look at the intent of the rule(s). From that perspective I dont think it's legal.
 
I don't mean to complicate the issue, but it reminds me of the stock airbox/ramair setup of the S5 RX7.
It seems to me that if none of the fast RX7 guys utilize these stock parts, it probably isn't worthwhile.
What I do know is that we toyed with it, and we determined that its volume flow restriction would likely
outweigh any possible (and doubtful) pressurized advantage

red 1991 (10).jpg
 
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In this case, this intake was included on a Miata driven by an extremely talented driver (I'm almost certain - Price). I never would have protested him because he could drive circles around me and I would have known it sure as heck wasn't the intake.

Andy - what's your take on the performance of that intake versus say an ISC?
 
JLawton said:
I think you have to also look at the intent of the rule(s). From that perspective I dont think it's legal.
Click to expand...
I concur. In my opinion the intent of the reg is to allow opening up of the restrictive stock air filter systems while avoiding allowances of things like ram air, cowl induction, and cold air intakes. We subsequently opened that further by allowing anything upstream of the throttle body/MAF/etc.

On the other hand, all air comes from outside the engine compartment, and it has to get in there somehow. We're seeing cold air boxes and radiant and convective heat shields around air filters and intake tubes to minimize the heating effects of the engine compartment.

With that in mind, how does this fit into that mindset? Is it incremental, and if so, within the boundaries of the intent? Or is it revolutionary to the point of being extra-compliant?

I dunno, that's why I'm asking. But at this point, ignoring the value of it, I'm thinking if you trim back the upper edge of the rectangular section such that it is at or behind the vertical plane of the aft edge of the radiator then you're compliant.

GA

P.S., Mr Original Asker, please note that nothing decided on this board even begins to imply what answers you'd get during a protest and/or appeal. This is the Internet and these opinions are worth exactly what that implies...
 
Mr. Original Asker: It this were to be protested, I'd honestly flip a coin on what the results were. Would most likely just depend upon who happens to be making the decisions, whether they are having a good day or not, among other risky variables.

Nothing wrong with bringing it up for discussion, that's for sure.
 
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