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Thread: splitter for the R

  1. #1
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    splitter for the R

    Is there a difference in the R and S splitter? We have an R, and our splitter only extends 2" from the nose. now that we are looking at it, it seems a bit meek.

  2. #2
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    FFR and others are just mounting the splitter forward I believe 2 inches.

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    WTF? really? how would that be strong enough?

  4. #4
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    I never did mount mine. But, if I did, I was planning on building an aluminum frame on top and connect that frame to the front nose frame.
    818S - #67 (SOLD IT!)
    Delivered: 18 November 2013
    Go Karted: 29 December 2013
    Titled/Registered: 28 March 2014
    Finished: NEVER!
    341 hp @ 4844 RPM / 389 tq @ 3717 RPM

  5. #5
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    Hello,

    Yes there is a difference between S and R splitter. The R splitter is straight on the back edge. The S splitter is cut out on the back.

    Greg
    Factory Five Marketing

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    Is that the only difference, the R doesn't extend further out front than 2" once installed in the proper location?

  7. #7
    Senior Member C.Plavan's Avatar
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    I moved mine forward even more. 1"+ you will need the struts, not just for strength, but to push the splitter downward. The FFR bumper angles the splitter up, which is not good.

    Thanks- Chad
    818R-SOLD!!!- Go Karted 7/20/14/ Officially raced NASA ST2- 2/28/15
    2016 Elan NP01 Prototype Racecar Chassis #20
    1969 Porsche 911ST Vintage Race Car
    1972 Porsche 911T (#'s matching undergoing nut & bolt resto in my garage)

  8. #8
    Senior Member xxguitarist's Avatar
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    Chad,
    What are your struts mounted to? Just the fiberglass?
    -Andrew

    Building 818S/R #297 with Tamra
    08 Mazdaspeed3 | '12 F800R | '97 Miata

  9. #9
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    As Chad did add some struts to support it to the nose.

  10. #10
    Senior Member C.Plavan's Avatar
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    Quote Originally Posted by xxguitarist View Post
    Chad,
    What are your struts mounted to? Just the fiberglass?
    Yep- with washers on the inside. Plenty strong. I also added supports attached to the radiator frame. Steel L brackets. Very similar to how the new nose/splitter attach to the 818 coupe...
    Last edited by C.Plavan; 12-03-2015 at 06:49 PM.
    Thanks- Chad
    818R-SOLD!!!- Go Karted 7/20/14/ Officially raced NASA ST2- 2/28/15
    2016 Elan NP01 Prototype Racecar Chassis #20
    1969 Porsche 911ST Vintage Race Car
    1972 Porsche 911T (#'s matching undergoing nut & bolt resto in my garage)

  11. #11
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    I'm pretty sure FFR mentions moving the splitter around as a tuning method. So there's no set "proper" location absent your aero needs. The same holds for the pitch of the blade. Parallel to the ground is how most folks run their splitters, but that's not written in stone. You can play with it just the same as you do the depth (starting parallel is probably good to establish a baseline).

    What irks me about the splitter is the underside treatment. The last time I saw a good picture of an early 818 FFR splitter, it showed that it was not a solid form but rather more of a top "skin" of what would be a properly constructed solid piece. That top skin just folds over an imaginary solid form and is then cut. The trouble with that is it creates a very disturbing edge from the air's perspective; it trips over it turbulently. So the real benefit of having a large area of low pressure air just got jacked up (how badly I can't say yet, but I suspect you don't see that in well developed splitters for a good reason). FWIW, they use the same construction method with the side splitters (which I think strongly implicates why they found them of little benefit).

    I don't know what the latest splitters look like, but if they're still just a top-skin, you might consider filling in the backside of the leading edge to form a smooth and gradual transition to the rest of the splitter underside.

    Best,
    -j
    "Weight transfer is the enemy."

    Executive Director
    The Community Garage

  12. #12
    Senior Member Pearldrummer7's Avatar
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    Chad, where did you get those struts? Those aren't supplied, are they?

  13. #13
    Senior Member C.Plavan's Avatar
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    Quote Originally Posted by Pearldrummer7 View Post
    Chad, where did you get those struts? Those aren't supplied, are they?
    No they are not. You can get them from APR (where the wings come from)
    Thanks- Chad
    818R-SOLD!!!- Go Karted 7/20/14/ Officially raced NASA ST2- 2/28/15
    2016 Elan NP01 Prototype Racecar Chassis #20
    1969 Porsche 911ST Vintage Race Car
    1972 Porsche 911T (#'s matching undergoing nut & bolt resto in my garage)

  14. #14
    Senior Member Pearldrummer7's Avatar
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    Quote Originally Posted by C.Plavan View Post
    No they are not. You can get them from APR (where the wings come from)
    Sweet. I'm copying you on that (and pretty much all of your aero).

  15. #15
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    moving the splitter around on a race car, that is flat bottom, makes no sense as you would constantly have to change out the floor piece that meets it. Furthermore, the opening that you would create at the base of the wheel arch would have to be covered, so the shape of said floor piece would have to change....and...the location of the brake ducts would move around, resulting in different lengths of ducting....and so on.....

    If this was really meant as a "tuner" add on to look like a real race car, I wish we would have known that so that we didn't waste our money on it and could have used the money to make out own. We will give it a try, but if we have too little front down force, we will have a splitter for sale. We usually like to tune the handling with the adjustable wing and the adjustable canards during track testing, moving a splitter in and out.....not possible at the track.

  16. #16
    Senior Member xxguitarist's Avatar
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    We made our own, and fabbed some steel brackets for the struts.
    Post showing design here: http://thefactoryfiveforum.com/showt...l=1#post212819
    -Andrew

    Building 818S/R #297 with Tamra
    08 Mazdaspeed3 | '12 F800R | '97 Miata

  17. #17
    Director of R&D, FFR Jim Schenck's Avatar
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    We mount the splitter in different locations based on the rest of the aero on that particular car, not so much that it is an adjustment method on a finished car. On the blue 818 R with the GTC-300 wing we have the splitter in the standard location with the rear flush to the front of the wheel opening. On the later car (red or silver/white) we used the larger rear GTC-1000 wing and then moved the splitter 2 inches forward and added the turnbuckles for extra support. Both of these cars used the "R" splitter which has the front wheel diffusers built in and the longer deck, the "S" splitter is flat across the back and also doesn't have the stiffness flange molded in. Most of our at the track aero adjustment comes from either wing angle or taping the grill openings.
    Jim Schenck
    Factory Five Racing

  18. #18
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    Quote Originally Posted by RetroRacing View Post
    moving the splitter around on a race car, that is flat bottom, makes no sense as you would constantly have to change out the floor piece that meets it. Furthermore, the opening that you would create at the base of the wheel arch would have to be covered, so the shape of said floor piece would have to change....and...the location of the brake ducts would move around, resulting in different lengths of ducting....and so on.....

    If this was really meant as a "tuner" add on to look like a real race car, I wish we would have known that so that we didn't waste our money on it and could have used the money to make out own. We will give it a try, but if we have too little front down force, we will have a splitter for sale. We usually like to tune the handling with the adjustable wing and the adjustable canards during track testing, moving a splitter in and out.....not possible at the track.
    There is no floor piece that meets the carbon blade - that's another irksome quality about it. At the rear the blade just stops and has no planned provision for a smooth transition to the rest of the flat floor. Folks who are trying to use this in earnest are left to cover the gap from splitter to floor (specifically the area covering the steering rack). In short, you're going to be up for fabrication anyway you look at it, so the rest of the concerns are minor. At-track tuning can make use of racer's tape to cover gaps temporarily and then you fab up what's needed once you've dialed it in to your liking.

    All told, this is part of why I didn't go with any of the aero-options... I'm making so much of my own stuff it would be a waste of money.

    Best,
    -j
    "Weight transfer is the enemy."

    Executive Director
    The Community Garage

  19. #19
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    I know, we have not used a single piece of alum from the kit as of today, not because it's not good, but because it doesn't do what we need it to. So, we did fab a filler piece between the splitter and the bulkhead to continue the flat bottom all the way back to the under engine tray that we are fabbing up as well. I'm not trying to say what FFR is supplying is not good stuff, I'm just saying for a dedicated race car with aero, small details mean everything. I was under the impression that all of this would have been sorted for an R, leaving little fab work to do. We have over 1200hrs in the car so far without it even starting, and with an additional 100hrs left in body work to make the rear lid lift on and off as one piece, marry the edges past the R roll cage, etc. we probably still have another 500-600 hours left to complete.
    Don't get me wrong, we are having fun, but we just thought some of this would have been dealt with as part of being an R, we didn't realize that the R is really a slightly modified S. We could have built it as is, but god is in the details, we just couldn't live with losing out on the potential performance of this platform by not dealing with them now.

  20. #20
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    I have made 2 additional splitters with different dimensions out fiberglass reinforced marine plywood. it is pretty light, strong and have used for splitters, under trays and rub-blocks on past projects

  21. #21
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    Exactly, we fab splitters out of ply, carbon fiber, and graphite powder in the resin all the time, will probably have to again. Very light, very strong. We didn't think we would need to for this project, but so it goes.

  22. #22
    Senior Member Mulry's Avatar
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    FYI, here's a close-up of the splitter that Davidson Racing uses on their Norma coupe at the 25 Hours last weekend:

    IMG_1984.JPG

  23. #23
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    Sweet! I can't believe I missed another one, I've driven in 5 of them, kills me to miss even one!

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    Jeesh - this took way longer than sanity should've permitted...had a crashing program nightmare to get through.

    Anyway, I was curious to follow up on my concerns that the top-skin-only splitter design adversely impacts flow. So I did some quick CFD analysis to evaluate it in comparison to a full-body design. Keep in mind that these are from a fairly low-res analysis, and I modeled the parts off of pictures only (no direct measurements from an actual part); I was just looking for proof of concept.

    First, here's the flow (velocity) under a full-bodied form:



    Compare that to the flow under the top-shell-only form:



    Notice the blue and green lines indicating reduced velocity. If you look closely, there's a definite dark blue zone in the middle. Since this is a low-res simulation, the lines don't show the cause of this clearly, but you get to know that something is producing it (more on this later). Here's another angle that shows the area more clearly:



    Also note in that shot that the flow speeds up greatly as it exits the kick-ups (what you would expect).

    Now here's a cut-plot of the shell-only that reveals the source of reduced velocity:



    Looking up under the leading edge lip, we get confirmation that the flow trips over that edge and effectively stalls as it goes into a turbulent flow. Eventually you see it recovers, but at a cost. The zone near the kick-ups is fast, but it's a smaller zone that you see with the full-body form seen here:



    The zone under the leading edge here is much faster and the really-fast zone near the kick-ups is significantly larger. In a complete-car simulation I suspect that would further impact the flow further downfield.

    So if you're using the supplied splitter, I'd fill in that back edge with a smooth transition to prevent the flow from tripping over it. As Retro said, very little details count for a lot when you're trying to make the best use of an aero package.

    Best,
    -j
    "Weight transfer is the enemy."

    Executive Director
    The Community Garage

  25. #25
    Senior Member STiPWRD's Avatar
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    Is the implication that you'd get less down force with the shell only splitter? Or more drag? Any comment on these reaction forces between the two cases - strictly 1-to-1 comparison, not looking for anything quantitative. Nice work btw!

  26. #26
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    I would expect to get both less downforce and more drag with the shell only splitter. The reduced downforce would be a function of lost air speed on the bottom side. The increased drag would be a function of a god-awful boundary layer - at least that's my guess. For the later, you might also benefit from less induced drag, so in a real world setting you could get equal drag (equal to the full-body splitter).

    I didn't do a ground effect study (maybe I should), and that might change things a bit. I was just interested in looking at the leading edge treatment.

    FWIW, if I had one of these and filled it in to make a gradual blend, I'd use the standard 5:1 to 8:1 rule of thumb for fairing a tube. So that would mean measure the thickness of the leading edge and blend it in 5 to 8 times that in length.

    Best,
    -j
    "Weight transfer is the enemy."

    Executive Director
    The Community Garage

  27. #27
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    THANK YOU!!!!!! That is exactly what we were looking for to prove our theory. I will post a picture of our fix once we have it installed, but I think we may get away with a 2 inch splitter if we can maximize the airflow effect under the car. We are going to flat bottom the splitter and blend it into the rest of the flat bottom behind it, and install the brake duct in the "kick up" area, which will speed that air through the brakes.

    Community works!

    Jeff

  28. #28
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    What does the car drive like with no aero?

  29. #29
    Senior Member Bob_n_Cincy's Avatar
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    Quote Originally Posted by greydog View Post
    What does the car drive like with no aero?
    Greydog,
    This is what Jim (FFR Engineer) told me.
    " On a non Aero track day car I would start conservative with the front bar hooked up and the stiffer springs in front, this should give understeer as a baseline. If the car has a lot of push then I would disconnect the bar and go from there. Your car may be a little different with the tank up front and radiator out back but I still think you would be in the ballpark with the stock S model set-up and then tune based on how the car feels to you. If you could can find a good balance at track days with the sway bar hooked up then you may be still close for an autocross set-up with the bar disconnected."

    I have done 300+ Non aero autocross runs plus a month of street and highway driving.
    We went stiff springs in rear to prevent body roll and wider tires in back to prevent oversteer. (no sway bar)
    Our handling is good on the track, A little harsh on the pot holes on the street.
    Bob


    "
    818S #22 Candy Blue Frame, Front Gas Tank, 2.5L Turbo, Rear radiator, Shortened Transmission, Wookiee Compatible, Console mounted MR2 Shifter, Custom ECU panel, AWIC soon
    My Son Michael's Turbo ICE Build X22 http://thefactoryfiveforum.com/showt...rts-818S-Build
    My Electric Supercar Build X21 (on hold until winter) http://thefactoryfiveforum.com/showt...e-Build-Thread

  30. #30
    Senior Member Mulry's Avatar
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    Quote Originally Posted by RetroRacing View Post
    THANK YOU!!!!!! That is exactly what we were looking for to prove our theory. I will post a picture of our fix once we have it installed, but I think we may get away with a 2 inch splitter if we can maximize the airflow effect under the car. We are going to flat bottom the splitter and blend it into the rest of the flat bottom behind it, and install the brake duct in the "kick up" area, which will speed that air through the brakes.

    Community works!

    Jeff
    Can't wait to see photos of this. Our build is kind of stalled while we rebuild the Lemons car, but this transition has been a big question for me from the start.

  31. #31
    Moonlight Performance
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    I'm still trying to decide between building my own front splitter vs buying the FFR one.

    The FFR one seems to have a positive angle, instead of a negative angle. It tapers downward as it goes to the rear.... seems to be this will cause lift at the front of the car instead of down-force. In trying to design my own splitter, the issue I see is that you are supposed to mount the nose about 1 or 1.5" (I forget which) ABOVE the level of the frame. So if you mount a splitter to the bottom of the front bumper and you have the splitter go back horizontally to meet the frame, it's going to have to drop an inch or so in order to meet the frame. So to get a truly horizontal or slightly negative angle on the splitter, you'd almost have to have the splitter hang down an inch or two below the bottom of the front bumper, then use a separate piece to seal the gap between the splitter and the bumper.

    Am I missing something here?

  32. #32
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    I am not sure what you are looking at Frank my splitter is parallel with the bottom of my car and actually has a little angle attack because of the 1/2" of rake in the car.3-4 front.jpg3-4 LS Frt 818.jpg

  33. #33
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    No, your right, it does kick up in the front, which is bad if you don't fix it. We installed a "wedge" shaped piece of plywood to flatten the bottom
    IMG_1106.JPGIMG_1099.JPGsplitter fix .JPG

    We extended ours about 2.5" with a secondary splitter (aluminum) instead of moving the FFR one forward, PLUS, we wanted to get rid of the step/ridge at the front of the splitter, as it created drag and upset the flow under the car.
    I would suggest making one. The FFR piece looks nice, but not fully functional in my opinion. Same goes for the diffuser, we still have it on the shelf.

  34. #34
    Moonlight Performance
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    Thanks guys.

    I get what you are saying, and, Retro, I understand the fix you are talking about, but beyond the upward-turned portion at the center of the FFR splitter where it follows the contour, my concern is that if the splitter goes all the way back to the radiator, it won't meet the radiator at the bottom of the frame because it is higher than the bottom of the frame. In other words, if you jacked the car up, removed the front tires, then took a flat sheet of plywood and just screwed the whole sheet onto the bottom of the front bumper - ensuring you pushed the plywood back as far as it would go, the plywood would run into the radiator, not the bottom of the frame. This is because the bottom of the bumper is about 1/2" to 1" above the bottom of the frame (per the FFR body install instructions). So, either the frame is going to be hanging below the bottom of the back of the splitter (bad), or you have to lower the back of the splitter so it meets the bottom of the frame below the radiator - but if you do that, now the splitter is at an upward angle.

    Does that make sense? I can draw a pic if it would help. Or maybe you guys mounted your nose lower than I did so it isn't even an issue for you?

  35. #35
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    I just made a aluminum panel to close up the area between the splitter and chassis, it wasn't that tough.

  36. #36
    Moonlight Performance
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    Ok. Does that panel sit horizontal or at an angle?

  37. #37
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    I have the car up in the air and eyeball it but it is pretty much on the same plane as the chassis.

  38. #38
    Moonlight Performance
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    Ok thanks Mitch. I guess my nose may be mounted too high then.

  39. #39
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    Mitch is right, our rad-nose-front cage is all on the same plane

  40. #40
    Senior Member FFRSpec72's Avatar
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    Quote Originally Posted by Mitch Wright View Post
    I just made a aluminum panel to close up the area between the splitter and chassis, it wasn't that tough.
    I did the same thing, boxed in the radiator area to force air through the radiator not the through all the front of the car, I don't run fans and I use the large louvers to let the air out of the hood
    Tony Nadalin
    2018 SOVREN Big Bore Champion
    2015 SCCA Oregon Region VP3 Champion
    2012 ICSCC ITE Class Champion
    FFR MkII Challenge Car, Spec Racer, Street Legal, SCCA, ICSCC and NASA Racing
    818R Build in progress

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