Front facia/bumper/brake duct/foglight/air dam rules

[JoshS]

I'm trying to understand what modifications can be done to the "bumper" area of modern cars.

At the end of this post I have quoted what I believe are the pertinent sections of the rulebook, and boldfaced the text that I think applies directly.

Question 1: If you have a modern car with non-metallic exterior bumpers that hide the rigid bumper structure (an "integrated bumper assembly", per rule 17.1.4.D.8.B), and this assembly has foglights mounted in it (are they "in" it? or "on" it? See 17.1.4.D.10.g), can I remove the foglights in order to install brake ducts, so that I don't have to make any changes to the body? (See 17.1.4.D.6.B).

Or, do we interpret these foglights as being "in" the bumper, in which case I cannot remove them, but I have to tape them? In that case, I'm not allowed to make changes to the bumper (6.B), or am I (8.B)?

Question 2: 8.b says that dealer-installed air dams may not be installed, but then it says that for "integrated bumper assemblies", airdams may be attached to the bumper cover. Does that mean that I can have a home-made air dam attached to the bumper cover, but I can't use a factory-optional air dam that attaches to the bumper cover?

I suspect that a lot of my confusion comes from the lack of definition of terms:
"in" vs. "on" for the foglight's relationship to the bumper
"body" for the 6.b rule
"front valance" for the 8.b rule

I have a feeling that these rules were really written for when every car had a steel bumper mounted externally to the steel body, and there wasn't any plastic. It's very confusing when I try to understand what the rules are for "integrated bumper assemblies."

The rules (under 17.1.4.D):

6.b: "Air ducts may be fitted to the brakes, provided that they
extend in a forward direction only, and that no changes are
made in the body/structure for their use."

8.b: "A front spoiler/air dam is permitted. It shall not protrude
beyond the overall outline of the body when viewed from
above perpendicular to the ground, or aft of the forward
most part of the front fender opening. This body outline does
not include bumpers or bumper mounts. The spoiler/air dam
shall be mounted to the body, and may extend no higher than
four (4) inches above the horizontal centerline of the front
wheel hubs. It shall not cover the normal grille opening(s) at
the front of the car. Openings are permitted for the purposes
of ducting air to the brakes, cooler, and radiator. Dealer
installed or limited production front/rear spoilers/air dams/
wings are prohibited. The spoiler shall have no support or
reinforcement extending aft of the forward most part of the
front fender wheel opening.

NOTE: Integrated bumper assemblies are defined as those
designs where an external non-metallic bumper cover
completely encloses the primary energy-absorbing bumper
and where this cover could be installed in its normal position
with the underlying bumper removed. On cars with integrated
bumpers, the front spoiler or airdam may be attached to the
bumper cover.

Where an air dam/spoiler is used, two total openings may
be cut in the front valance to allow the passage of up to a
three (3) inch diameter duct leading to each front brake/rotor
assembly.

Where no air dam/spoiler is used, two total openings of a
maximum size five (5) inches by seven (7) inches maybe cut
in the front valance so that brake ducts can be added with a
three (3) inch diameter hose leading to each front brake/rotor
assembly."

10.g: "Exposed headlights, parking lights, and side marker lights
shall be taped. OEM light assemblies mounted on or below
(but not in) the bumper shall be removed."

[dickita15]

I will try
1.Don’t think of the bumper and the bumper cover as the same thing. If the lights are recessed in the bumper structure than they must be taped. If they are below the structural bumper and just cut into the bumper cover below they must be removed.

2. You may add any air dam to the bumper cover that meets all the dimensional limits in the GCR. The section on not adding a factory piece is so you will not use that as an excuse to exceed the dimensional limits.

[Mike Courtney]

I have wondered all of the same things as Josh - well written. Another specific question I have regarding front spoiler / airdam limits :

Rule:
"It shall not protrude beyond the overall outline of the body when viewed from
above perpendicular to the ground, or aft of the forward
most part of the front fender opening".

Does the body outline include the front bumber cover?

Is the most forward part of the "fender opening" the most forward part of the wheel opening area at the fender or the most forward part of the wheel opening at bumper cover?

[lateapex911]

I have wondered all of the same things as Josh - well written. Another specific question I have regarding front spoiler / airdam limits :

Rule:
"It shall not protrude beyond the overall outline of the body when viewed from
above perpendicular to the ground, or aft of the forward
most part of the front fender opening".

Does the body outline include the front bumber cover?[/b]

Yes, I think it does. Essentially, with the car at ride height, take a plumb line around the perimiter of the front end to the ground. Keep the airdam within that outline and you're fine. If the airdam incorporates a splitter, then the splitter must not protrude beyond that outline.

Is the most forward part of the "fender opening" the most forward part of the wheel opening area at the fender or the most forward part of the wheel opening at bumper cover?
[/b]

yes...whichever is greater, or more forward. Within the confines of the height requirement, the wheel opening is usually pretty vertical here, so it's not really a big difference. Use good judgement and you'll be fine.

[RSTPerformance]

I think that Dick and Jake did a good job answering, if it still isn't clear be sure to ask!!!

Raymond

[JoshS]

I will try
1.Don’t think of the bumper and the bumper cover as the same thing. If the lights are recessed in the bumper structure than they must be taped. If they are below the structural bumper and just cut into the bumper cover below they must be removed.

2. You may add any air dam to the bumper cover that meets all the dimensional limits in the GCR. The section on not adding a factory piece is so you will not use that as an excuse to exceed the dimensional limits.
[/b]

Dick, thanks! Those are the best answers ... allows me to remove foglights (which would break anyway), and therefore makes brake duct installation easy. I don't have a particular air dam in mind, but your answer on that seems like the most logical explanation as well. However, I do think that this particular wording leaves something to be desired.

Thank you.

[924Guy]

Actually, I would be concerned that you might not be able to take a spoiler/splitter all the way out to the front of the bumper conver. The rule 8b is pretty clear, IMO, for when you have a metal bumper (such as I do) - seems like it was written with that in mind. "This body outline does not include bumpers or bumper mounts." But if you have an "integrated bumper assembly" (bumper cover plus underlying structure), how does that work? Just a rules nerd question for me now, as I do not have nor do I plan to race a car with a bumper cover. Do you substitute the phrase "integrated bumper assembly" in for "bumper" in 8b? Or do you use the phrase "bumper cover?" This might really cut down on a lot of how far you can legally go. Then perhaps the defining limit might be the foward edge of the sheetmetal above the bumper, like the top of the nose?

A separate item, which I'm only now paying attention to. Seems to me like there's a conflict (or maybe only in my head?) between points 6b and 8b. I used to think that 6b was the limiting factor; put in plain English, you can't cut the sheetmetal to put in your brake ducts. Then I read 8b as reiterated here, I see I am allowed to cut holes in the front valance to allow passage of hoses or to install scoops, depending on air dam use. For the record, I do run an air dam, attached to the bottom of what I consider the front valance. But I'm wondering what is, for sure, the correct technical definition of "front valance?" If it is, as I think, the metal panel below the bumper, that sorta seems to conflict with 6b, since I'm then allowed to cut sheetmetal to get air back there. Am I just being overly conservative on my reading of the rules?

[JoshS]

A separate item, which I'm only now paying attention to. Seems to me like there's a conflict (or maybe only in my head?) between points 6b and 8b. I used to think that 6b was the limiting factor; put in plain English, you can't cut the sheetmetal to put in your brake ducts. Then I read 8b as reiterated here, I see I am allowed to cut holes in the front valance to allow passage of hoses or to install scoops, depending on air dam use. For the record, I do run an air dam, attached to the bottom of what I consider the front valance. But I'm wondering what is, for sure, the correct technical definition of "front valance?" If it is, as I think, the metal panel below the bumper, that sorta seems to conflict with 6b, since I'm then allowed to cut sheetmetal to get air back there. Am I just being overly conservative on my reading of the rules?
[/b]

I pointed out this same conflict in the original post, and I'm even more convinced now that there's a conflict. Note that the GCR defines body as "All parts of the car licked by the airstream." (Chapter 22, page 130.)

So 6.b clearly disallows modifications to this "body", and yet, 8.b says that holes may be cut in something called the "front valance" (undefined).

I suspect that this valance is supposed to be the sheet metal that's behind the spoiler (and thus, the valance is not part of the body then, so no conflict), but on cars with "integrated bumper assemblies", I don't think there *is* a valance, and so if someone is not adding a spoiler, I see no allowance for cutting holes for brake ducts. I wonder if this was the intention.

[ddewhurst]

My understanding of the valance, spoiler/airdam/outline of body/brake hose/brake duct rules.

Valance:

Guys, the valance is what your car manufacture calls a valance. Not what your friend or someone on this site calls a valance. Example for MY 1st gen RX-7: MY car has an integrated front bumper per the ITCS-11 rule .b. definition. MY car has a front valance per the Mazda factory workshop manual. The valance on MY car is the vinal part that attaches below & to the intergrated front bumper cover & also attaches to each front fender. No rule allows us to remove the valance........... What does your factory workshop manual call a valance?

Front brake air passage holes:

Am I alowed to cut holes in MY front valance for air passage to my front brakes when I do not add a spoiler/air dam ? Yes, per ITSC-11 rule .b. per the last paragraph. I may cut two 5" x 7" holes.

Am I allowed to cut holes in MY front valance for air passage to my front brakes when I add a spoiler/air dam? Yes, per ITSC-11 rule .b. per the second last paragraph I may cut two holes in MY valance to allow passage of up to a 3" diameter duct through each hole. ( They would have been better of calling the 3" diameter duct a 3" diameter hose because in most cases the hose is what would travel through the valance when adding a spoiler/air dam. Brake ducts & brake hoses are two different items.)

Am I allowed to cut holes in the add on spolier/air dam for air passage to the front brakes? Yes, per ITSC-11 rule .b. per the first paragraph.

Outline of body:

The outline of body is two different lines dependent if you have a non-intergrated or a intergrated bumper.

Outline of body "A", the outline of body is drawn without the bumper & without the bumper mounts per ITCS-11 rule .b. per the first paragraph third sentence. My understanding of rule spec is for non-intergrated bumper.

Outline of body "B", when you have an intergrated bumper the spoiler/air dam may be attached to the bumper cover per ITSC-11 rule .b. per the second paragraph last sentence therefore the outline of body is drawn with the bumper cover in place. My understanding of rule spec is for intergrated bumper.

Being that I have made a couple errors all ready this year please correct any errors within this post.

Please do not recall my card

David

ps:

***Note that the GCR defines body as "All parts of the car licked by the airstream." (Chapter 22, page 130.)***

"All parts of the car licked by the airstream and situated above the belly/floor pan with exception of the of the roll bar or cage." Above the belly/floor pan could be meaningful in some situations.

[JoshS]

Guys, the valance is what your car manufacture calls a valance. Not what your friend or someone on this site calls a valance. Example for MY 1st gen RX-7: MY car has an integrated front bumper per the ITCS-11 rule .b. definition. MY car has a front valance per the Mazda factory workshop manual. The valance on MY car is the vinal part that attaches below & to the intergrated front bumper cover & also attaches to each front fender. No rule allows us to remove the valance........... What does your factory workshop manual call a valance?
[/b]

Mine doesn't call anything a valance. According to the manuals for my car, I guess I don't have one.

I don't buy your premise that what's important is what the manufacturer calls it. Two cars could have basically identical construction, but due to their country of manufacture and whoever translated the service/parts manuals into english, they might have different words for the same part. And therefore, with your interpretation, one of these cars might have more allowances than another, just due to some translater's choice of words. That doesn't seem right.

The rulebook needs to define "valance" if rules are going to refer to it. That it isn't defined just results in a gray area.

[JimLill]

Then there's the question how many IT cars really need a front spoiler.... in particular what advantage would be gained on a ITC or ITB car which seldom sees higher than 120 mph on most tracks.

[ddewhurst]

***Mine doesn't call anything a valance. According to the manuals for my car, I guess I don't have one.***

Josh, how about telling us what make & model car you have & maybe we can help. does your car have something below the bumper & between the fenders?

***I don't buy your premise that what's important is what the manufacturer calls it.***

Lets see now, we could use the GCR glossary to define what a valance is (The GCR glossary has no definition of a valance.), we could call a valance whatever Josh would would like to define a valance as (not accecptable wthin my premise.), we could identify the valance using the words that the manufacture workshop manual uses (kind of easy method to solve questions for identifying parts.) or Josh could write a memo to SCCA Topeka requesting that the word valance be added to the GCR glossary (I'll be watching Fastrack for the CRB response to your memo.). Also please ask Topeka what you have under your bumper between your fenders.

Josh, when the manufacture workshop manual for your car specifies your compression as 9.5:1 do you look for another value for your compression value in some other puplication ?


***Then there's the question how many IT cars really need a front spoiler.... in particular what advantage would be gained on a ITC or ITB car which seldom sees higher than 120 mph on most tracks.***

Jim, a spoiler/air dam diverts air from traveling under a car. With less air under the car there will be less pressure (lift) under the car & the pressure on top of the car will push the car down gaining adhesion to the track. How many fast ITC/ITB cars have spoiler/air dams?

Have Fun
David

[JimLill]

***Then there's the question how many IT cars really need a front spoiler.... in particular what advantage would be gained on a ITC or ITB car which seldom sees higher than 120 mph on most tracks.***

Jim, a spoiler/air dam diverts air from traveling under a car. With less air under the car there will be less pressure (lift) under the car & the pressure on top of the car will push the car down gaining adhesion to the track. How many fast ITC/ITB cars have spoiler/air dams?
[/b]

I understood that, but on a lower HP car is the extra drag caused by increased frontal area and reduced Cd worth any advantage you might gain in downforce at < 120 mph?

Not an easy question to answer... I&#39;ll try simulating it and see!

[JimLill]

Not an easy question to answer... I&#39;ll try simulating it and see!
[/b]

OK... the results are in... I added an airdam to a 85 VW ITB car that would give some downforce. The penalty was a 5 mph reduction in top speed and a 1.5 sec increase in 0-100. The dam "consumed" about 10 HP at top speed... my take, be careful with airdams unless you can monitor the results.

[JoshS]

Josh, how about telling us what make & model car you have & maybe we can help. does your car have something below the bumper & between the fenders?
[/b]

For the sake of argument, let&#39;s use a BMW Z3 (I don&#39;t currently have a car in my possession, but this is what I&#39;m thinking of building.)

This car has an "integrated bumper assembly", and this contains a piece of metal that spans the frame left-to-right (the "bumper", I guess), and then one big piece of plastic that covers that, meeting the hood above it and the wheel wells on the left and right. So no, I don&#39;t think there is really something "below the bumper and between the fenders." It seems that a great majority of cars built in the last 15 years have this same basic construction.

Lets see now, we could use the GCR glossary to define what a valance is (The GCR glossary has no definition of a valance.), we could call a valance whatever Josh would would like to define a valance as (not accecptable wthin my premise.), we could identify the valance using the words that the manufacture workshop manual uses (kind of easy method to solve questions for identifying parts.) or Josh could write a memo to SCCA Topeka requesting that the word valance be added to the GCR glossary (I&#39;ll be watching Fastrack for the CRB response to your memo.). Also please ask Topeka what you have under your bumper between your fenders.
[/b]

The letter has been written and submitted already.

I am not okay with using my definition either (I honestly don&#39;t have one.) I think there are only two options here:
1) Define a valance in the glossary, so that we know what this rule means
2) Don&#39;t use the word valance in the rule
And then after one of those options is chosen, 6.b and 8.b should be reconciled if necessary.

What do you think the intent of these rules is? 6.b prohibits modification of the body, and 8.b allows for the modification of something undefined, which I&#39;m sure some of us would consider to be part of the body. What was the intent?

BTW, please note that for the car in question, I wouldn&#39;t need to modify anything anyway. I would use the foglight holes, because this car, fortunately, already has holes suitable for brake cooling, once the foglights are removed. It&#39;s more of an academic question because there appears to be a conflict, or at least a gray area, in the rules.

Josh, when the manufacture workshop manual for your car specifies your compression as 9.5:1 do you look for another value for your compression value in some other puplication ?
[/b]

I don&#39;t understand what you&#39;re getting at. Of course I don&#39;t look for another value. But I do check the rulebook to see if it requires me to do what the workshop manual says, or if it allows a modification.

[ddewhurst]

***The penalty was a 5 mph reduction in top speed and a 1.5 sec increase in 0-100. The dam "consumed" about 10 HP at top speed...***

Jim, interesting simulation info. With these ^ items lost because of the spoiler/air dam what is the corner speed increase because of presumed addhesion gain? Total agreement that if factual results cannot be monitored where is the gain.



Josh PLEASE don&#39;t use that word intent.

***let&#39;s use a BMW Z3***

I would beleive a BMW person might chime in. I&#39;ll dig & see what I can learn about the bumper & below part names.

***8.b allows for the modification of something undefined,***

Presuming you mean your non valance part I forward the following with reference to 6.b. & 8.b.

6.b. specs the general rule of no holes in the body/structure. I would view the 6.b. rule as the overall rule specifically because of the undefined word structure. Structure being all kinds of stuff (fender wells, radiator support stuff, whatever else.) not licked by the air stream. I view 8.b. as a supplemental rule allowing specified holes in the valance/spoiler/air dam.

My comment about the factory workshop manual compression ratio number not being correct was directed towards your reference that the word valance interpretation might have been not correct in the factory workshop manual. It was totaly a little dig.

Have Fun
David

[924Guy]

Like David said, full evaluation of effectiveness of an air dam or front spoiler has to take into account the resultant effect on cornering speed - and so will be quite dependant on spoiler shape and track selection.

One also needs to be mindful of the effect on radiator cooling air flow (due to reduced air pressure under the car). Doesn&#39;t directly affect vehicle speed, but I know I like my car to run cooler than hotter!

Furthermore, due to reduced underbody air, a fully-detailed analysis will also have to review the resultant decrease in underbody drag.

Not so simple. I&#39;ll keep running my airdam, even at a track with an avg speed of 65mph and top speed under 90mph...

[JimLill]

***The penalty was a 5 mph reduction in top speed and a 1.5 sec increase in 0-100. The dam "consumed" about 10 HP at top speed...***

Jim, interesting simulation info. With these ^ items lost because of the spoiler/air dam what is the corner speed increase because of presumed addhesion gain? Total agreement that if factual results cannot be monitored where is the gain.[/b]

I am neither for nor against dams.... just an Engineer type that always thinks about a thorough analysis and method of experiment :-)