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Old 03-13-2013, 04:57 AM   #1
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Default Road/Track Day/ Race - body shell questions

Have removed all panels off the car to clean and prepare for respray (going white with clear coat)....thoughts, suggestions, experiences, rants etc welcomed....

Car IS still road legal but is probably heading towards more track day / race than a DD but the odd trip to work and/or Sunday blast on the road will always be likely. However, I REALLY want to kick as much *** in the class I have entered as I can so reducing weight, reducing failure points, disassembly time etc is all being factored.......So,


-What are the for's and against's of ditching the front inner gaurds (black plastic liners).

-What are the for's and against of ditching the black plastic crash structures under the bumpers, front and rear....i.e. should I ditch those too?....(crash safety concerns).

-I have a pair of later doors with the side anti-intrusion bars (the 89 doors dont), do I remove the wind up windows from these and use them as light weight race doors or keep those for the street? (I guess the question is which is the most dangerous race or road?)

- Shall I cut out the rear bumper like most of the race guys seem to do. Does it have a "real" affect?
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Old 03-15-2013, 06:22 PM   #2
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100 views and not even 1 opinion....???

Does anybody in the race prep section race? build race car...? build track day car..?

Go step up, no one will hurt you here...(you hear that hustler..!!)
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Old 03-15-2013, 06:29 PM   #3
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Quote:
Originally Posted by mx5-kiwi View Post
Have removed all panels off the car to clean and prepare for respray (going white with clear coat)....thoughts, suggestions, experiences, rants etc welcomed....

Car IS still road legal but is probably heading towards more track day / race than a DD but the odd trip to work and/or Sunday blast on the road will always be likely. However, I REALLY want to kick as much *** in the class I have entered as I can so reducing weight, reducing failure points, disassembly time etc is all being factored.......So,


-What are the for's and against's of ditching the front inner gaurds (black plastic liners).

-What are the for's and against of ditching the black plastic crash structures under the bumpers, front and rear....i.e. should I ditch those too?....(crash safety concerns).

-I have a pair of later doors with the side anti-intrusion bars (the 89 doors dont), do I remove the wind up windows from these and use them as light weight race doors or keep those for the street? (I guess the question is which is the most dangerous race or road?)

- Shall I cut out the rear bumper like most of the race guys seem to do. Does it have a "real" affect?
-I would leave the plastic wheel liner. Its probably got some aerodynamic use (no experience, I am saying that because many prototypes tend to vent the area above the wheels) and at the very least it stops you from kicking rocks up into the front bumper/engine area/etc.

-I think most people take those out.

-The rear bumper cut out helps with some aero, but you need to supplement it with other things (flat undertray, diffuser, etc.).
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Old 03-15-2013, 06:36 PM   #4
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1. Ditch them
2. We keep them for enduros because they keep the door from popping open if lightly contacted.
3. Haven't tested back to back but what little data exists shows that the air mass is negative pressure and not moving very fast there. IOW, I don't think it makes a difference until you remove the entire skin and unshroud the back of the rear tires.
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Old 03-15-2013, 10:22 PM   #5
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+1 for ditching #1.
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Old 03-15-2013, 11:45 PM   #6
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Just to clarify, there are 4 points here and now I am confused which one you guys have skipped.....

1. Inner Gaurds.

2. Under bumper crash structures.

3. Anti Intrusion doors. my guess is this is the one being skipped....

4. Cut rear bumper. - Seems this can stay for the time being.
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Old 03-16-2013, 02:17 AM   #7
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Leave the door bars if you don't have a cage, ditch them if you do.

The under bumper crash structures and kinda pointless, although the front one acts as the upper part of your radiator ducting with all the stock plastics. I doubt you'll have a soft enough impact on track that they'll be the thing that saves your car.
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Old 03-16-2013, 04:07 AM   #8
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Oops yah. Keep the intrusion bars.
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Old 03-16-2013, 09:18 AM   #9
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Quote:
Originally Posted by mx5-kiwi View Post
Just to clarify, there are 4 points here and now I am confused which one you guys have skipped.....

1. Inner Gaurds.

2. Under bumper crash structures.

3. Anti Intrusion doors. my guess is this is the one being skipped....

4. Cut rear bumper. - Seems this can stay for the time being.
Emilio skipped the bumper crash structure? I am not following how the plastic bumper support helps with the door...
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Old 03-16-2013, 10:17 AM   #10
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It was one of OP's original questions...

Mine are gone, however, your oem front bumper is kinda supported by it at the opening, so you might want to fab mounting hardware or it may flap around some on track.

Safety aspect - just increased your crumple zones...
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Old 03-16-2013, 01:43 PM   #11
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Default Do over

OK I need to try this again but maybe read a little better, sorry.

-What are the for's and against's of ditching the front inner gaurds (black plastic liners).

We never keep them on a track car. Sometimes we will keep the front section on NB's to protect a fender mounted oil cooler. But usually the OC is in the nose so the liners come out. Tires hit them under full compression with coilovers. I've seen guys get black flagged because the liner was half loose and flapping around. Sucks to lose a race because of that.

-What are the for's and against of ditching the black plastic crash structures under the bumpers, front and rear....i.e. should I ditch those too?....(crash safety concerns).

Added weight on the ends raises MOI, makes the car transition slower. They're a must have in a class that allows bump drafting. We pull them out to improve handling. They will absorb so little energy in an on track crash that's it's pointless to keep them for that.

-I have a pair of later doors with the side anti-intrusion bars (the 89 doors dont), do I remove the wind up windows from these and use them as light weight race doors or keep those for the street? (I guess the question is which is the most dangerous race or road?)

We like to keep them. Having a door pop open in a race gets you black flagged and can ruin a winning enduro run. Just a light tap to a door without that bar will pop it open. With the bar, it'l take quite a scrape and remain shut. Also helps to keep a heavily gutted door from sagging, which will also lead to the doors popping open on track. The bar itself weighs maybe a pound . Well worth it and near the center of mass anyway. No comment on the windows as only you can answer that.

- Shall I cut out the rear bumper like most of the race guys seem to do. Does it have a "real" affect?

We have yet to test A/B testing with the center cut out. The few guys that have collected pressure and vector data in that area all showed that the air is low pressure, turbulent and moving slowly on both sides of the bumper skin between the frame rails. Thus, I don't think cutting a hole there probably does squat. I know the turbulent low pressure wake coming off the tires causes some drag and suspect that removing the bumper entirely reduce drag a bit.
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Last edited by emilio700; 03-17-2013 at 03:02 AM.
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Old 03-16-2013, 06:46 PM   #12
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That was great thank you all very much! (especially you Emilio for the detail and experience).
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