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Thread: Which Kit - Challenge Car or Mk4 Kit?

  1. #1
    Senior Member R Thomas's Avatar
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    Which Kit - Challenge Car or Mk4 Kit?

    I have read many posts regarding on track use of Factory Five Cars. I purchased the online manuals of both the Challenge Car and the Base Mk4 kit. I also attended the build school for the Roadster. I also reviewed the NASA rules for Challenge Cars, ST2 and 3. I would like a few things confirmed before I step further down the path.

    My first group of questions is for Factory Five - I am unable to find a brochure for the challenge car? The online info seems outdated - makes reference to both Bilstein and KONI shocks? The online manual shows the brake installation using the Wilwood pedal box, but the parts list does not include it? Is this model still in production or perhaps the documentation being currently altered?

    My use of the car includes both a fair amount of street driving use of many of the tracks on which NASA hosts races. I am not 100% sure I will ever advance to actively racing in the Challenge series, but would like to keep that option open. I am happy with the use of 302 push rod engine with fuel injection. But, this is where I find the rules of the challenge series somewhat restrictive. They state donor parts should be from an 87-93 Mustang. The donor I have is a 97 Mustang for the some of the parts.

    If I use the 97 Radiator, Steering Gear, Rear End and Brakes from a 97 does that make the car illegal for class?

    Next is the transmission, if I am going to buy a TKO 500 or 600 does it really matter that the 5th gear ratio is .82? The video I watched the Challenge Cars never even used 5th.

    And I am really confused on wheels 17X9 and tires 255/40x17 Toyo's is this an absolute or max size? For example if my rain tires were Toyo T1 Sport 225/45X17 on Mustang 17X7.5 stock rims am I illegal?

    Lastly are the Trick Flow parts required? It would seem not, I know I would be down on power but it's fine for learning tracks and car handling.

    I will either end up with a Mk4 with 302 or a Challenge car with the same motor. So for a car that will see both street and track use which is the better path?
    Daily Driver 2011 Ford Mustang Convertible
    Donor 1997 Mustang Coupe
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    I'm going to apologize in advance, I am doing this from my phone right now. So please forgive misspellings and similar errors.

    To answer your question about the parts from the 97 car, and similar items the answer is yes you will be out of compliance. However, that is only for the challenge series. For the super touring classes those are just fine. Even for the challenge series, there are parts from the 97 car you can use such as the radiator. It is best to use the rules published on the NASA racing Site other than using what's on the factory five challenge car page. The page has not been updated in a while, and the ones on the NASA side are much more accurate.

    As for the optional parts, like the trick flow engine components, those are optional. I did not run them for a full season just to see how the reliability was going to be. The stock Yep I 302 engine is fun as it is. And if nothing else you can run in ST classes, time trial classes, or even some of the vintage classes if you want to. I think your approach of learning the car, and it's handling dynamics is a very good approach. Plus in the standard 302 lay out, it makes a great HPDE school car.

    I think the bottom line, or at least the answer you're really looking for though, is if you're going to track your car regularly I think the challenge car is a better choice. Mainly for all the safety features that are added to it, plus you know the rollbar is compliant.

    I think the bottom line, or at least the answer you're really looking for though, is if you're going to track your car regularly I think the challenge car is a better choice. Mainly for all the safety features that are added to it, plus you know the rollbar is compliant.

    Just remember that challenge cars do not have doors. This is been a sore point with my wife, who likes to ride in the car every once in a while.
    2012 NASA-SE FFR Champion
    2011 NASA-SE FFR Champion
    Race page - http://www.mh-motorsports.com/race.shtml
    Team Facebook page - http://www.facebook.com/pages/MH-Mot...s/264814350042

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    Senior Member jimgood's Avatar
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    Quote Originally Posted by R Thomas View Post
    I am not 100% sure I will ever advance to actively racing in the Challenge series, but would like to keep that option open.[/B]
    You answered you main question with that one statement. If you want that option open, then it's the Challenge car.

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    Senior Member FFRSpec72's Avatar
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    All around the challenge car is a safer car, street or track, the cage is very well built. So if you are going to do both street and track and don't mind the issue of not having functioning doors with the functionality of improved safety then I would get the Challenge car. If you are willing to take on the additional weight then you can make the car as streetable as you want.

    As far as being legal, you have to follow the rules if you want to run in the Challenge Series, tire/rim size, transmission gearing, caliper/brakes, etc.
    Tony Nadalin
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    2012 ICSCC ITE Class Champion
    FFR MkII Challenge Car, Spec Racer, Street Legal, SCCA, ICSCC and NASA Racing
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    Senior Member R Thomas's Avatar
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    Thanks for taking time to respond to my questions.

    I realize that some of the questions I asked here NASA related, but I had 2 reasons for posting here. First the series is a FFR Spec series and the second the NASA Challenge Forum is dead. I think I understand the rules as I read them pretty well so I will try to address some of my confusion.

    Mostly its with wheels and tires. The rules say the wheels in the series will be 17" with a MAXIMUM width of 9". As I understand the stuff I've read the stock Ford wheels from my 2011 Mustang are 17' X 7.5" so they are legal by the rules. Now to the tires, Toyo Proxes RR or RA-1 size 255/40X17. This would mean those tires would be legal on 7.5 wide but stupid. The recommended tire size is 225/45X17 there are Toyos in that size. I imagine that Toyo has a big part in sponsoring the class so it is likely they made the tire and size requirement for the class. I also understand I could run Toyo Sport 1 225/45X17s on a Challenge car in another class such as ST-2/3, but that hardly helps the Challenge series car count.

    Another rule that makes no sense to me is allowing the TKO-500 trans but restricting the internal gears. As I stated early I have watched many recent videos and 2nd, 3rd, and 4th were the only gears used yet I shell out $3000 for a new transmission and get saddled with a 3.27 first and .68 fifth when a 2.97 and .82 are available? Seriously whats the point in that. To me, its like the rule regard stock drum brake 4 lug rears. Who in their right mind would run that? And if they did what competitor would be filing a protest?

    The actual question about the transmission is if I have my heart set on the close ratio box, can I file for an exemption to use it? Maybe I should be taking these things up with NASA management. And maybe I shouldn't worry until the car is ready to go on track in a race class, its just the nature of my training. I have paid dearly in the past for not getting the whole picture up front.

  6. #6
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    The rules are written by the Class director (a Fellow Challenge car driver), and not by NASA. Each year the proposed rule changes are posted, and feedback gathered.

    As far as the tires and transmissions. The reason for the ratio was to keep the cost down. Originally it was set so that only the stock T5, and T5 WC would be used. The ratios listed are the stock ones for those. Those who wanted to run the stronger Tremecs were allowed, but they had to run the same ratio as the T5s. If we open up other ratios, then there is nothing to keep someone from building custom ratios and those who don't have that kind of money to spend will be out of luck. If we want to make a change we would need to decide on a ratio as a group, vote on it, and make sure that they are available for everyone to use. It would still kill the chances that the people still running the T5's out of luck. Otherwise it isn't a spec class, it's an open class. In open classes usually the most money wins, not the best driver.

    This is the same issue with the tires. If a size is selected that is shared across classes it's significantly cheaper from Toyo. One of those sized is the 255/17. I am not familiar with the Toyo Sport 1s, but I do know the Toyo Proxy Sport 1s are a street tire and are 240 UTQG, while the RR and RA1 are DOT race tires with a UTQG of 140 and 40. They are MUCH faster than any standard street tire.

    There are no real exemptions in the Spec classes. If you want to modify the care to suit you better I think we are all for it, you would just need to look at the open classes.
    2012 NASA-SE FFR Champion
    2011 NASA-SE FFR Champion
    Race page - http://www.mh-motorsports.com/race.shtml
    Team Facebook page - http://www.facebook.com/pages/MH-Mot...s/264814350042

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