New rules for these classes can be found on pages 69 & 74. I recieved a clarification in response to a question I was asked. I would like to share the details for everyone's education.
"The radiator needs to be in the approximate stock location, at least as large an open area as the stock unit and must not have the airflow through it blocked or obstructed in any way. You can mount anything between the opening and the radiator but it can in no way restrict, redirect, obstruct, impede or otherwise alter the airflow between the grill opening and the radiator. Considering that putting pretty much anything in an airstream blocks some of the flow then we take a very hard look at anything mounted between the opening and the radiator. The competitor will have a uphill battle trying to convince us that it is legal.
A primary aerodynamic difference between a production classes and the altered classes is the penalty the former pays for having air flowing through the radiator & engine bay. This is a core difference. Altering this penalty by definition takes you out of production.
Here is an (incomplete) list of things that people try to do to minimize the aero penalty of air going through your radiator:
Put a plate over the front of it
Put a plate over the back of it
Put a tank in front of it
Put a duct in front of it, redirecting the air
Mount it at an angle
Make it smaller with the resulting hole blocked off
Tape over the grill
Fill the fin area with a foreign substance
etc.......
all of the above (and more) will bump you to Altered or get you thrown out of impound if you arrive as a production or a Gas Coupe.
Things like oil coolers, intercoolers and A/C condensers are an area that requires closer scrutiny. Putting a oil cooler in front of the radiator is fine so long as the thing actually lets air flow through it and into the radiator behind. That’s common in production cars and street vehicles since the dawn of time. But, stacking 7 disconnected oil coolers with dented fins in front of the radiator is not OK, that would be artificially blocking the air through the radiator. Putting an air conditioning condenser in front of it would also be OK providing it was stock for the vehicle entered and functions properly (still lets air pass through it to the radiator, not that the A/C blows cold). If it is not the stock part then no, that would be artificially blocking the air through the radiator. Intercoolers are also an area of potential abuse. They are pretty much required and if a stock one was available it will not be big enough so a larger one will commonly be fitted. Again, as long as it is allowing air to pass through it and to the radiator then it would be OK, provided that it is actually being used on a turbocharged engine.
We don't care if you make your radiator taller, wider or thicker, just not smaller. We don't care if you move it from the passenger side to the driver’s side or vice-versa so long as you are paying the full penalty of the aero drag caused by the radiator airflow into the engine bay that is fundamental to a production vehicle. If you are not then you should be (by definition) in altered.
Determining if a car is legal is easy. Simply look at the radiator & grill opening. If the airflow is impeded in any way that is not stock or something you would not see on a real street driven vehicle then it is not legal for production. It doesn’t matter how you did it, it just matters that you are attempting to block the air flow thru the radiator.
If the airflow is restricted from stock because of a realistic need then that is ok. Oil coolers, Intercoolers, etc… etc fall into this category, as does thicker radiators. Common sense is used here. If it is legitimately needed then it’s OK but watch for shenanigans. This is where a person will put a 4 inch thick, ultra fine pitch radiator that covers 100% of the engine radiator, plumb engine oil to it and call it an oil cooler. Then stack an identical unit in front of that but with A/T fluid. That’s blocking the radiator air unnecessarily and illegal. We just have to use common sense. A good test is if you believe the vehicle could drive in stop & go traffic on a 100F day on the street in the presented configuration assuming the radiator was flowing 100% water and air fans were present and a stock engine was in the car. In short, can enough air still get through to satisfy the stock vehicles worst case use?"
These are the factors used to enforce this rule.
DW
