Is cowl induction an unfair advantage

[Keith Church]

Did you know that tin-top prodcars are allowed an unfair advantage over cars without windshields? If you answered no then you will be surprised to learn that the last 4 HP Championship winning cars all shared this unfair advantage. The best source of high pressure air for engine intake charge is high pressure air that packs up just in front of the windshield commonly referred to as cowl induction. Ever notice how NASCAR Cup cars get their intake from a standardized cowl induction system sourced just in front of the windshield. According to the SOM’s at Daytona, every Prod car with a windshield just got a significant advantage handed to them. All us tin-tops can reshape the underside of our hood and the cowl panels to take advantage of the air pressure on the windshield to provide pressurized air for our engines. While the PCS says that no misalignment or modification of the bodywork can create ventilation where none previously existed, the SOM’s ruled that stock cowl vents providing air to the cabin were already “vents” and redirecting that vented air to the intake plenum instead of the cabin was allowed because “velocity stacks, ducts and air boxes” are unrestricted. Really?

A protest was filed questioning a competitors’ modification of body panels (hood underside and cowl panels) to create high pressure cowl induction for engine air intake in violation of 9.1.5.E.9.a.1,2 and 6. Now the fact that the SOM’s defended the use of cowl induction by saying essentially “a vent is a vent” and cabin air vents can be redirected to the engine air intake is a really tortured interpretation of the rules. Adding insult to injury, they said that the modification was allowed by 9.1.5.E.1.b.6 which refers to engine modification and specifically air induction systems. Basically they claimed the air induction rule trumped the bodywork modification rule. Doesn’t the PCS say that no allowed modification can perform a prohibited function.

For decades the PCS has been clear about prohibiting modification of body panel to create air intake sources to the extent that it specifically prohibits opening inner fender panels and modifying the heater plenum without covering any created opening with metal panels. If somebody doesn’t clarify the legality of using air from the back of the hood for intake we can expect to see lots of creative cowl induction systems next year.

 

[Sam Moore]

Yep.

 

[Brian Linn]

The Honda CRX that I drove at this year's Runoffs, currently owned by Steve Hussey, is the ex-Dan Meller, Mike Moser and Loshak driven car. It won it's first Runoffs in 2009 with Dan Meller behind the wheel. It has been to the Runoffs every year since it won.

At the 2015 Runoffs I was protested on Tues by Bill Perry, father of William Perry who drove a first gen Honda CRX. At that point I was 2nd on the grid while Perry was 3rd. the protest was based on 9.1.5.a - The body, unibody, frame and their components can be lightened, provided that structural rigidity is not compromised to the point of requiring additional support. No non- stock openings can be created in the bodywork.

The three SOM's that inspected my car were accompanied by two current CRB members, Chris Albin and Jim Wheeler. I believe that it was mostly Chris' input that led to the decision. Later, Chris Albin explained to me why he thought the car was in compliance.

-Replica body components only need to replicate the "surfaces licked by the wind". One doesn't need to reproduce the stamped steel structural components found under most current production cars. The bottom side of the hood on our CRX isn't even part of the air box - the underside is just the material thickness of the component.
-The trim pieces around the cowl are allowed to be removed.
- 9.1.5.2.b.6 states: Air cleaners, velocity stacks, air supply ducts and cold air boxes are unrestricted.

The hood is an accurate replica without any misalignment to the rest of the car. The body work (portion "licked by the air stream") does not have any non-stock openings. The induction is clearly visible from the exterior and has been so for years. To note "every Prod car with a windshield just got a significant advantage handed to them" is inaccurate.

Bill Perry came up to me at impound and said "hope the protest wasn't an inconvenience, I was just trying to get a ruling on some cars that we run with locally." So this seemed disingenuous since his son would potentially benefit from it if I were to be found non-compliant. I noted that it took about 2 hours of my time and he replied that it only took him 5 minutes. While protests serve a purpose, sometimes a question to your competitor may resolve the issue. I hadn't met Will Perry prior to this event but we had exchanged some helpful PM's on this site earlier in the year.

I'm doing my best to keep this to the facts as I know them and not let any emotion change the context of this.

 

[Protech Racing]

The current rule has the cowl box legal per your car IMHO. " air intake box unrestricted".

The Honda with the front side exhaust may be the only car that benefits.
Maybe the rule should state that intake air must come from the "headlight area" plus or minus 12in.

 

[billp]

Please don't confuse me, Bill, with Will. We are two people with a very different mid-set for racing. Perhaps mine is influenced by several years of Stewarding. As entrant, I didn't require, nor request, his permission to take action.
For a few years now, no car has won the Runoffs in HP without a cowl induction. So I wished to get clarification as to it's legality. We own two LBCs where this isn't an option. I thought this a good opportunity to develop more information, as there was a rather large crew with a car with cowl induction at an event, presumably knowledgeable officials, including the CRB, and minimum inconvenience to the car with action filled more than two days before the race. I filed the protest at 11:45 am, and was handed the SOM's decision at 1:06 pm so the statement of 2 hours tied up is a mystery. I had just long enough to go to the Honda tent and pick up lunch, and almost finish eating it before I got the call to come to the SOM room to get their decision).
I regret any inconvenience, but to take Brian's suggestion to do this at a local race would probably mean protesting some single person team (the driver) and would likely be absent very knowledgeable officials.
Taking the action in the Runoffs setting has served the purpose of making this issue well known.

 

[Brian Linn]

Please don't confuse me, Bill, with Will.

I don't think I did. Clearly pointed out the relationship and the interactions.

For a few years now, no car has won the Runoffs in HP without a cowl induction. So I wished to get clarification as to it's legality.

This seems counter-intuitive to me. So the cars that have won the Runoffs for multiple years could have been running something that was illegal, that is in plain sight for everyone to see?

 

[RonInSD]

For most cars, wind tunnel data shows that the pressure at the head light area is greater then the cowl area, so the headlight area offers a greater ram air effect then cowl induction. That being said from an aerodynamic standpoint anything you can legally do to improve any high pressure areas will improve the aero of the car.

Non tin top prod cars can also used cowl induction if they choose but most also have chosen to remove the windshield which reduces this cowl pressure area.

The holes in the cowl area created by removal of heater core need to closed because those holes go between the engine and the passenger cabin.

BTW I noticed this last year on Loshak's red CRX when I saw pictures of the engine bay. I checked the rules at that time and could not find a reason why it was not legal. AS and IT do not allow cowl induction even if factory but those are different classes and rules.

 

[Aaron Johnson]

I'm in the process of adding the windshield back onto my spitfire specifically so i can do this.

But seriously. I think that there are many other reasons the Honda has been successful for so many years. is it an unfair advantage? i don't know, but certainly there are advantages that each type of car has over one another.

 

[Kendall Jones]

How many spridgets have removed a head light and run a semi pressurized air box? Hint - lots.

 

[Tom Broring]

How many spridgets have removed a head light and run a semi pressurized air box? Hint - lots.

Agreed Kendall. While it is popular to take shots at the former G-Prod cars in H, a properly (probably not 7" hole) sized headlight or marker light feed to the intake should work similarly to a cowl intake. The location of the airbox is the determining factor for each car.

 

[kruck]

How many spridgets have removed a head light and run a semi pressurized air box? Hint - lots.

Agreed Kendall. While it is popular to take shots at the former G-Prod cars in H, a properly (probably not 7" hole) sized headlight or marker light feed to the intake should work similarly to a cowl intake. The location of the airbox is the determining factor for each car.

Abso-freaking-lutely. Massive ram-air "headlight" induction and the ability to chop the top and reduce your frontal area by a third (at least), vs. a cowl induction intake. Oh yes, so unfair... :roll:

 

[Ed Funk]

Honda made convertible versions of the Integra and CRX, dint they? Purty sure I've seen some. :twisted:

 

[RonInSD]

Honda made convertible versions of the Integra and CRX, dint they? Purty sure I've seen some. :twisted:

From what I have found for the CRX, only 500 first gen CRX were factory built and imported to the USA so they don't qualify for Production racing. After those 500, all CRX convertibles were aftermarket conversions.

 

[Joe Harlan]

Honda made convertible versions of the Integra and CRX, dint they? Purty sure I've seen some. :twisted:

From what I have found for the CRX, only 500 first gen CRX were factory built and imported to the USA so they don't qualify for Production racing. After those 500, all CRX convertibles were aftermarket conversions.

Factory produced conversions have been in prod for a long time the RX7 and 240sx are us conversion cars.


I cannot believe we are even having the conversation on cowl induction. Look around the paddock and see how many creative ways people have built pressurized air boxes in prod.

 

[Ed Funk]

Honda made convertible versions of the Integra and CRX, dint they? Purty sure I've seen some. :twisted:

From what I have found for the CRX, only 500 first gen CRX were factory built and imported to the USA so they don't qualify for Production racing. After those 500, all CRX convertibles were aftermarket conversions.

I was kinda joking, hence the lil' devil face. :roll:

 

[RonInSD]

Honda made convertible versions of the Integra and CRX, dint they? Purty sure I've seen some. :twisted:

From what I have found for the CRX, only 500 first gen CRX were factory built and imported to the USA so they don't qualify for Production racing. After those 500, all CRX convertibles were aftermarket conversions.

I was kinda joking, hence the lil' devil face. :roll:

Ed, I just realized you drive a CRX so I get the twisted face....lol

 

[JohnMcNaughton]

I've always been curious which of these points carried the bigger advantage/disadvantage.

1) Remove the windshield from a convertible. And, accept the increased drag and air turbulence within the cockpit area.

2) The aero advantage a nice little sedan has over an open prod car. You could make a case that the side windows are open, and interior air turbulence is a problem for the tin tops also.

3) Both cars tweak their lowered windshield or their tin top side window ducts in an effort to reduce the cockpit turbulence. Always wondered why I never saw a full width Gurney lip on the open car low windshield. Have seen some tin tops with very large air ducts for "interior cooling."

Net affect, the convertible does realize a gain in top speed without a windshield. But, that may be why tonneau covers are specifically not allowed. With the tonneau cover they would then realize the full aero advantage of removing the big windshield.

Where you get your ram air from is only noise. There was more air pressure in front of the headlight than at the base of my the laid back windshield on a sedan. Even my new, in the 70's, 510 Datsun windshield has some angle to it.

Each car is different. Only air pressure measurements on each car can define the advantage/disadvantage for each car.

Everything else is an opinion, and like the nose on your face, we are each different there also!

 

[JasonIsley99]

I've always been curious which of these points carried the bigger advantage/disadvantage.

1) Remove the windshield from a convertible. And, accept the increased drag and air turbulence within the cockpit area.

2) The aero advantage a nice little sedan has over an open prod car. You could make a case that the side windows are open, and interior air turbulence is a problem for the tin tops also.

3) Both cars tweak their lowered windshield or their tin top side window ducts in an effort to reduce the cockpit turbulence. Always wondered why I never saw a full width Gurney lip on the open car low windshield. Have seen some tin tops with very large air ducts for "interior cooling."

Net affect, the convertible does realize a gain in top speed without a windshield. But, that may be why tonneau covers are specifically not allowed. With the tonneau cover they would then realize the full aero advantage of removing the big windshield.

Where you get your ram air from is only noise. There was more air pressure in front of the headlight than at the base of my the laid back windshield on a sedan. Even my new, in the 70's, 510 Datsun windshield has some angle to it.

Each car is different. Only air pressure measurements on each car can define the advantage/disadvantage for each car.

Everything else is an opinion, and like the nose on your face, we are each different there also!

Side vents were addressed a few months back in Fastrack, and there are limitations on the size.
Funny, pretty much every drop top I have seen has a tonneau - I mean required fuel cell firewall - filling in the once open area in the back. :lol:

 

[JohnMcNaughton]

A tonneau cover fits from the rear of the soft top mounting area, over the passenger seat area, and extends to the top surface of the dash board area. It fits as closely as possible to cover all of the open area behind and beside the driver. Therefore reducing the interior air turbulence. They also had an additional soft tonneau cover. With the tonneau installed, you could also zip up the area over the drivers seat, and keep it from leaking with the top down. (An oxymoron with the British cars!) Prod cars are not allowed to use what they were issued when new, under the guise of safety.
I think the racing Mercedes had an example of the tonneau in the 50's. They also used the rear top cover as an air brake, until their LeMans accident.

A boot cover fits over the rear parcel shelf, to cover the folded soft top. Every convertible I have ever had included the cover. With my British cars it was a soft cover, usually the same material as the soft top, with a support rod to hold the leading upper edge in place. With my various Corvettes convertibles, it was a hard cover, up to the rear of the seat backs.

I'm sure we have lots of members who have never had the curse of owning a British car. It's also a habit you tend to repeat for some unexplained reason. Never owned a Japanese convertible, so don't know what provisions they had. But they tended to improve on the British errors.
I'm sorry, did I just Trump these cars?

 

[JasonIsley99]

A tonneau cover fits from the rear of the soft top mounting area, over the passenger seat area, and extends to the top surface of the dash board area. It fits as closely as possible to cover all of the open area behind and beside the driver. Therefore reducing the interior air turbulence. They also had an additional soft tonneau cover. With the tonneau installed, you could also zip up the area over the drivers seat, and keep it from leaking with the top down. (An oxymoron with the British cars!) Prod cars are not allowed to use what they were issued when new, under the guise of safety.
I think the racing Mercedes had an example of the tonneau in the 50's. They also used the rear top cover as an air brake, until their LeMans accident.

A boot cover fits over the rear parcel shelf, to cover the folded soft top. Every convertible I have ever had included the cover. With my British cars it was a soft cover, usually the same material as the soft top, with a support rod to hold the leading upper edge in place. With my various Corvettes convertibles, it was a hard cover, up to the rear of the seat backs.

I'm sure we have lots of members who have never had the curse of owning a British car. It's also a habit you tend to repeat for some unexplained reason. Never owned a Japanese convertible, so don't know what provisions they had. But they tended to improve on the British errors.
I'm sorry, did I just Trump these cars?

The last vehicle that I had that utilized a tonneau cover did so to cover a 6' long bed that contained my tools and spare tires on race weekends. Must be a generational thing. :lol:

Seems like a stretch to me when the roadsters fill in the back of the car, but at the same time the rules require them to cover the fuel cell. Not sure what to think about the cars that have done the cover and are using the OE tank. :ask: