UPDATE ST4/TT4 and other for 2017

[shuko]

And add to that the discussion of "rake" in which the flat splitter is angled at, say, 2 degrees from the horizontal plane, or even 1 degree.

[Philostang]

And add to that the discussion of "rake" in which the flat splitter is angled at, say, 2 degrees from the horizontal plane, or even 1 degree.

 

Good. +1 on that clarification as well.

 

I had assumed the "horizontal plane" of reference was actually the chassis. So having a splitter parallel with the rake in the chassis set up wouldn't violate the rule. However, having rake in the splitter itself (i.e. not parallel with the chassis as viewed from the side) seems like a question (or two) to explore.

 

Best,

-j

[Greg G.]

Hi Greg,

 

Got another splitter rule clarification question for you - this one came out of a conversation I recently had w/another potential ST4 driver...

 

So the rule states we can use: "c) Single flat, horizontal front splitter that protrudes no greater than 4” from the vehicle."

 

I read "flat" and "horizontal" to mean the entire splitter must reside on a single plane with all lines parallel to the horizon, both viewed from the front of the car and from the side of the car (sans any inherent angle from rake in the chassis set-up).

 

My buddy reads this to mean only viewed from the front. So under his reading, when viewed from the side the splitter can be flat/horizontal for the first 4" or so, but then have an angle (or more than one) that kicks up in the rear. His claim is that when viewed from the front, all lines of the splitter are parallel with the horizon (so it's "horizontal"), and there are no curves in the splitter (so it's "flat").

 

I think this is a b.s. reading of the rule. Viewed from the side the splitter is clearly NOT flat, nor are all lines parallel with the horizon. Would you please clarify for us before something get's fabricated. =)

 

Best,

-john

You are correct.

[jbjones]

Apologies for the clarifications as I am new to TT and trying to figure the rules out.

 

For the splitter, on something like an FR-S where the front bumper has the "fangs" on the edges and recesses inwards, would the splitter have to similarly recess in that section? If so, as I read the rules, an extension could be added to the recessed area of the bumper that does not exceed 2" or an angle of 5 degrees and then the recess of the splitter would not be required (if the answer to the previous question is yes), correct?

 

On the rule re: cutting of the rear bumper, can these be cut in the rear of the vehicle as well as the part of the bumper behind the rear wheels and on the side of the vehicle so long as the sections removed do not cover the rear frame/bumper cross beam? Additionally, if the rear frame is higher than the cross beam, can a smaller aftermarket cross beam be run and additional bumper be removed?

Photos needed for your first question.

 

Even if your model vehicle utilizes a single piece to act as a rear quarter panel/rear bumper cover, the side of the car is still the side of the car, and the area behind the rear tires on the side of the vehicle would likely be interpreted as not being part of the rear fascia. So, it should not be cut, except at the rear to prevent a protest.

The second part of that question:

"every Production vehicle must retain its unmodified:

1) OEM frame rails/rear frame cross beam, and/or Unibody, and Sub-

frames/suspension cross-members (in their OEM locations)."

 

FR-S front end for first question which shows the recess in the middle of the bumper:

 

[Greg G.]

For the splitter, on something like an FR-S where the front bumper has the "fangs" on the edges and recesses inwards, would the splitter have to similarly recess in that section? If so, as I read the rules, an extension could be added to the recessed area of the bumper that does not exceed 2" or an angle of 5 degrees and then the recess of the splitter would not be required (if the answer to the previous question is yes), correct?

 

 

FR-S front end for first question which shows the recess in the middle of the bumper:

 

 

So, a flat splitter can be attached to the bottom of that fascia. It cannot protrude more than 4" from the fascia at any location, so it either needs to have a recess cut in the front of it to match the fascia, or the splitter just won't be as far away from the other aspects of the fascia, and the 4" will be at the center. The rules specifically do not allow you to add anything to that fascia (as in the proposed extension you mentioned). The reference to the words "molded into" are for aftermarket fascias, not for modifying the BTM fascia.

[Greg G.]

Even if your model vehicle utilizes a single piece to act as a rear quarter panel/rear bumper cover, the side of the car is still the side of the car, and the area behind the rear tires on the side of the vehicle would likely be interpreted as not being part of the rear fascia. So, it should not be cut, except at the rear to prevent a protest.

 

is this the actual interpretation of the rule or just a probable scenario that might lead to later discussions about the rule?

 

I'm assuming the area in front of the front tires on the side of the vehicle is considered the front fascia and not the side of the vehicle. being the front fascia the rules of 7.3.2 D 2)e) apply.

 

if my assumption is correct about the front, why wouldn't the entire rear bumper cover/fascia(even behind the rear wheels) be considered part of the rear bumper cover fascia for rule 7.3.2 D 2)e)?

Well, all cars are different, and it is hard to make a determination without seeing photos of what we are talking about. What I can tell you is the purpose of the rule was to allow the "parachute" aspects of rear bumper covers to be cut from the rear of the vehicle since we are not allowing rear diffusers, and also to allow for exhaust cutouts. The aero rules were written to put limitations on the "necessary" modifications to have a top level vehicle. If we need to add additional wording in the future because someone decides that their rear fenders and quarter panel are really just a bumper cover, then we will.

[Greg G.]

7.3.2 D 2)

aerodynamic parts/devices/aides shall be limited in ST4 to the following

 

if a car has oem side skirts and an oem rear diffuser will they need to be removed for the car to run in ST4?

 

 

are the cars listed in appendix B exempt from the ST4 limitations?

for example will a bmw be able to use m3 side skirts and an m3 diffuser and still be legal in ST4?

 

the ZR1 listed in appendix B has '(front fascia only)' wording.

does that mean the ZR1 must remove the rear diffuser and side skirts to run in ST4?

Lets start with this:

7.3.2.D "Under this specific rule, an aerodynamic aide is considered non-OEM if it did not come configured on the base trim model (BTM) of the vehicle from the manufacturing factory. Except for those vehicle-specific higher level trim models (non-BTM) listed in Appendix B, there is no updating or backdating across trim models or the addition of dealer installed OEM options permitted."

 

Because there is no allowance for aftermarket/non-BTM side skirts or diffusers, that rule is the only possible allowance for side skirts/diffusers.

So, if the base trim model of a vehicle has side skirts and a rear diffuser, then it can stay on the car in ST4. If it doesn't come on the BTM, and the car has them for whatever other reason, they should be removed for ST4. The exceptions are in the Appendix, and include the listed M3's (that again need to remove any wing/rear spoiler). So, I think your question is whether a BTM BMW be allowed to add the M3 side skirts and diffuser if there is one (like an E36 328 adding E36 M3 skirts), correct? It is not listed as permitted, but it would be something that would make sense (Why does the more expensive and "better" M3 get these items, when the lower trim level of the same model doesn't?). That would be something for consideration by e-mail, for a caveat in the Appendix to allow updating the same generation lower trim level to that of the M3.

 

Yes, these Corvettes (Chevrolet Corvette C6 Grand Sport, Z06, ZR1) can keep the front fascia only (and remove other non-BTM aero parts like side skirts and diffusers), and still get the OEM Aero Mod Factor. Of course, none of them can run with wings and get the OEM Aero Mod Factor.

[Cobra4B]

I don't see a C7 Corvette mentioned in the 2017 TT rules anywhere. Is the C7 allowed to compete? How does NASA differentiate between the base Stingray, Grand Sport w/ 3 stages of aero, then Z06 with 3 stages of aero.

 

Would a C7 GS or Z06 with the "standard" stage 1 OEM aero have to take the aero hit given they're technically not "Stingrays" like the base C7?

[Greg G.]

I don't see a C7 Corvette mentioned in the 2017 TT rules anywhere. Is the C7 allowed to compete? How does NASA differentiate between the base Stingray, Grand Sport w/ 3 stages of aero, then Z06 with 3 stages of aero.

 

Would a C7 GS or Z06 with the "standard" stage 1 OEM aero have to take the aero hit given they're technically not "Stingrays" like the base C7?

Reverse the thought pattern--there is no "aero hit". There is an OEM Aero adjustment due to no aero.

These would not qualify for the OEM Aero Mod Factor (and likely would not be able to compete in TT3 due to power levels).

[jbjones]

The reference to the words "molded into" are for aftermarket fascias, not for modifying the BTM fascia.

Not to split hairs here, but please tell me what is accomplished by allowing an aftermarket fascia but not modifications of the BTM fascia, and also, how an aftermarket fascia is something other than a modified BTM fascia. I can't understand how a rule set would allow my to buy something off the shelf that would be within the rules, but I can't modify a stock part to do the same thing (and save money).

[farberio]

Greg,

 

Concerning the fender flare rule, would non vented and oem body lined wide fenders be ok? I need to replace one fender and its roughly buy 2 aftermarket fenders for the price of 1 oem fender. I will need to do flares as well so I am hoping this could be an easy win.

[Greg G.]

h) Flared and/or rolled fenders. (Only to extent necessary to cover tire as viewed from above)

I wouldn't be able to give my opinion on whether these were just "flared" fenders or not without seeing them compared to the stock fenders. Safest bet is to just use OEM and flare/roll them.

[Matt@NCM]

http://www.certifit.com/

[Pat533i]

Does anyone else think the mod factor for aero should be higher? Like say, equal to the autocross tire mod factor. Well maybe not that high but closer to it.