Front Splitter How high or how low?

M

mg_john

Well-known member
I'm fabricating a front splitter to run on my Spridget in GTL form.

What distance from the ground should the lower surface of the splitter be?

I think the lower, the better it works. But I don't want to destroy it first time out!

Picture shows it sitting about 1.5 inches off the garage floor.



Any suggestions?

Thanks,

John Hewell

#29 HP/GTL Spridget
 
John,
My splitter just tickles the ground under hard braking. (GTLite Nissan.) Then I added rear (wing or spoiler) to balance out the car.

On the rare occasion where I go off track and break the front splitter, I can feel a push everywhere. At that point I add in more rear sway bar (I have a cockpit adjustable rear bar) and balance the car best I can for the rest of the race.

Peter
 
As Peter says, the optimum setup is so the splitter just touches under extreme circumstances.

Keep hard braking and curbs in mind.

I made mine adjustable, started out high and kept lowering it until it started to touch. I put tape underneath so I could easily see when the tape was ground away.

Mine is 2.25" off the ground with the no driver in the car.

But this is all going to depend on your wheel rate, dampers, front overhang length, curb love, etc.

I just replaced a 1/4" marine plywood splitter that was 2 seasons old and was about 50% worn through.

-Kyle
 
According to a highly respected NASCAR, IRL race engineer I know:

"The front splitter is the only free lunch in motorsports..........increased front downforce with NO increase in longitudinal drag" . Of course if you are going fast enough you might need to balance the front downforce with rear downforce (no free lunch here)..................but that depends on the application.

Thanks, Jay
 
Does the perimeter rule apply to GTL cars?..........that splitter would be illegal in production IMO.
 
Excerpted from the GT rules.

12. A spoiler may be fitted to the front of the car. It shall not
protrude beyond the overall outline of the car as viewed from
above except as follows:
• GT2: a front splitter may extend up to 3 inches.
• GT3: a front splitter may extend up to 2 inches.
• GTLite: a front splitter may extend up to 2 inches.
In all classes, the spoiler shall not extend aft of the forward
most part of the front fender opening (cutout), and shall not
be mounted more than four (4) inches above the horizontal
centerline of the front wheel hubs. The spoiler shall not cover
the normal grill opening at the front of the car. An intermediate
mounting device may be used on cars whose front bodywork
is above the four (4) inch minimum. Openings are permitted
for the purpose of ducting air to the brakes, radiator, airbox
and/or oil cooler(s); equal openings may be placed in the
standard lower front panel directly behind openings placed
in the spoiler. When bumpers are retained, the spoiler and
bumper shall appear to be two separate parts. Spoiler “pans”
are only permitted forward of the leading edge of the front
wheel openings and shall be flat and follow, but not exceed,
the line of the front fender/spoiler bottom.

I think that I understand your concern, Jay, that the sides of the splitter are outside of the front bumper. In most Series' there is a maximum width rule that would address this but in reading the splitter language it does not say that the splitter may go forward of the front bumper but that it may "extend" not more than 2". Just my thoughts.
 
I know you don't want to hear this but the experts say that the splitter should be strong enough that you can stand on it! Think about it........if it can't exert at least 100 or 200 # in the vertical direction (and live to tell about it) you likely won't even notice the downforce effect. Making a splitter this ROBUST is not EZ and almost always ignored by the amateurs like us!
 
Thanks to all of you for your comments and suggestions.

My reading of the GTL splitter regs is that it cannot be wider than the widest part of the fenders. I'll follow that and also the 2" forward of the bumper.

Jay, I'm not sure I'll be able to stand on the final version of the splitter. It will be made of 3/16 (maybe 1/4) Alumalite with the strongest orientation facing front/rear. It has a frame which is mounted onto the stock swaybar mounting points. I think it will be pretty rigid. I'll know next weekend at Roebling which has a pretty long straight.

Thanks again,

John Hewell

#29 HP/GTL Sprodget
 
John,

A sprite is a little bit different deal. Top speed of say 115mph really can't generate pressure differentials of much significance anyway..........sounds like you'll be fine.

I had a splitter exactly like yours on my H car starting around 2003 and I didn't notice any real difference with or without it.
 
Jay Lutz":3vgs1y0o said:
... the experts say that the splitter should be strong enough that you can stand on it! Think about it........if it can't exert at least 100 or 200 # in the vertical direction (and live to tell about it) you likely won't even notice the downforce effect.
Click to expand...

Point taken.... but I think you would agree that an evenly distributed load would be more accurate than a concentrated load under feet. A small pressure over a large area gets the load we want.

But you did touch on another topic I'd like to discuss... perhaps off line so we don't bore everyone to death... do I have your email?
 
I made mine from a used NASCAR Tegris splitter. basically flipped the bumper cover upside down, traced it onto the Tegris, cut it out, then slid the cover 2" straight back and mounted it on the car. It's heavy for most standards, but I can jump on the thing and it doesn't care. I've had many off course excursions and scooped up entire TX fire ant mounds and bringing them back to the pits.

Between the splitter and the relatively tiny 48 x 8.5 rear wing we're allowed, my laptime dropped 3-4 secs on average. So yeah, it's worth the small weight penalty if you don't upset the handling balance with too much grip in the front and no added wing.

Edit.. sorry for the huge pic, but I figured you would at least get a kick out of the fire ant relocation I did a while back..
 
Were the fire ants mad? They seem to get upset with me when I disturb the edges of thier little world in the yard.
 
They absolutely were NOT happy when I wiped them off the car. Stupid me didn't realize it was an active ant hill- just thought it was mud. 3 swipes later when they all attacked, I looked down and noticed my arm was red up to my elbow. I've been in the south long enough I shoulda known better. :oops:
 
This thread has reminded me of an observation from a Road America Runoffs around 4 years back. If you want to learn from someone's successful setup, look to the quickest cars. In this case , it was John Black's GT3 Nissan (which I believe later either won and/or set fast lap).

Wandering by the Nissan in the paddock, I noticed what looked like a blood streak on the top of the splitter. Crouching down to look closer, I discovered a HALF of a squirrel against the grass catcher mesh in front of the radiator. So I guess the correct height for the splitter is 1/2 the height of a Wisconsin squirrel. However, it is unclear whether that is 1/2 the height of a ducking squirrel, 1/2 the height of a running squirrel, or 1/2 the height of an oblivious nut munching squirrel.
 
Mine is a bit higher, but still effective for both uses. Mine is evidently 1/2 the height of a south TX cottontail at full sprint. I'll spare you the photos, but there's a reason a friend of mine put that ghost-bunny on the hood. Let's just say the front end of the car got scrubbed with bleach and it took over an hour just to pick rabbit jerky out of the left suspension and rotor.
 
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