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Thread: Bodykits and aerodynamics for real performance?

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    Bodykits and aerodynamics for real performance?

    Anyone build an actual proven performance e36 with these wide body Aero kits? I just don't see many videos of the track cars with the pandem or gtr kits or alike? Too expensive to maintain/buy or just not effective as a performance add on? And where can I find any evidence of the Aero improvements for the kits?
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    The wide body kits aren't so much for aero as they are to allow a wider stance and wider wheels/tires. I suppose there's an aero benefit compared to running a car with it's fenders hacked off and the wheels poking way out from the body, but that's not really something people do as far as I know. If you compare a WBK body car to a stock body car, the WBK car probably has slightly more drag overall due to its wider and uneven profile, but the additional grip from bigger tires and a wider stance should overshadow that and improve lap times.

    That said, with the right wheels and some fender rolling you can already get pretty wide wheels and tires on an E36, so that may be why track people don't usually bother with the WBK's. Also, you have to cut up and drill the bodywork, and some people don't want to do that, even on track cars.
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    Thanks for the quick response. Then if I may continue asking away here, what would you say is the widest set of tires an e36 could benefit from in terms of handling, and not in the drag strip sense, where the tire would still have bite? It would seem moot to widen a car by a few inches already and still have 225 wide 17 inch tires?
    Last edited by M3blitkrieg; 06-14-2017 at 04:10 PM. Reason: This tiny keyboard and my fat pudgy fingers don't get along
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    Quote Originally Posted by M3blitkrieg View Post
    Thanks for the quick response. Then if I may continue asking away here, what would you say is the widest set of tires an e36 could benefit from in terms of handling, and not in the drag strip sense, where the tire would still have bite? It would seem moot to widen a car by a few inches already and still have 225 wide 17 inch tires?
    Here's the rundown:

    With no fender modifications you can run up to 17x9 245/40 all around. You will need 10-12mm spacers in front to clear the struts and the wheels will need to be high offset (40+) to fit in the rear.

    With rolled rear fenders you can run 17x9 255/40 all around. You will need 10-12mm spacers in front to clear the struts, and will also need to be running at least -2.5 and -2.0 degrees of camber front and rear respectively. They will also need to be high offset in the rear as above.

    Beyond that, you will need to pull or cut your fenders. I've seen or read of people using as wide as 265 or 275 tires on 17x9.5 or 18x10 wheels with cut fenders and wide body kits. I don't have any first-hand experience with this, but there should be tons of info in this subforum along these lines.
    Last edited by TostitoBandito; 06-15-2017 at 11:26 AM.
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    Quote Originally Posted by M3blitkrieg View Post
    Anyone build an actual proven performance e36 with these wide body Aero kits? I just don't see many videos of the track cars with the pandem or gtr kits or alike? Too expensive to maintain/buy or just not effective as a performance add on? And where can I find any evidence of the Aero improvements for the kits?
    You won't find any "evidence" of aero benefit from a wide body / aero kit / flare kit because there isn't any. Also because the cost to do wind tunnel testing is so high. The added frontal area is usually going to add drag.



    The exception is when you have a spinning tire sticking out into the airstream - you want to cover the leading edge if at all possible. Sometimes class rules and/or budgets/practicality don't allow that.



    Mostly its because the wide body kits just aren't made to reduce drag - they are mostly made to look "kewl". The flares above were made by my shop to cover the front edge of the 335mm tire, smooth out the airflow.



    To go beyond what TostitoBandito implied, I'll say it - most the flares/wide body kits are there to allow for the Stancy Stance crowd to "roll hard". The kit above violates all sorts of tire clearance and aero norms to get "that look". A racer would look at this and giggle. I mean the front has virtually zero bump travel!



    For racers, widebody kits and flares allow for more track width and tire width clearance. I flared the E30 above in ~2009 to clear an 18x11" wheel at all four corners - but it isn't as aero friendly as I'd build it today. But tire width still trumps aero drag.



    I'm all about running wider tires for road course and autocross performance. There is nothing that helps drop time faster than wider/stickier tires. Track width is also a win-win (exception: this slightly hurts slalom performance in autocross use).



    I've been trying to find the mythical internet "too wide" tire, but so far haven't found it. On every car we've tested they always go faster with wider tires. Usually until we run out of tire width options. The E46 M3 above has 335 front and 345 rear Hoosiers. If they made a wider version we'd try it.



    I tried to squeeze an 18x10" wheel and 285mm tire under "rolled and stretched" E36 fenders (above) but the tires just rubbed so badly it wasn't as fast as it was on 17x9.5" wheels and a 255/40/17 tire (the sizes TostitoBandito posted were spot on).



    With custom flares we've run as much as a 315mm tire on an E36 - but it would be faster with a 335.



    In DSP autocross use the top BMWs are moving to 335mm tires, even with only ~250-275 whp, and they are faster than the same cars used to be on 315s or 285s...
    Terry Fair @ Vorshlag Motorsports

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    Very informative post, Terry. I was just wondering if there was an upper limit (within reason) that tire width doesn't help with corner speed. Can you estimate how much per lap reduction per 10mm extra tire width (all else equal)? I know it's a big 'it depends', but is it 10th's of seconds, or halves of seconds for every 10mm increase?

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    OK. Understood. + Tires = better times. Bodykits= aesthetics for the most part and only have obvious aerodynamic gains of tires and what not.

    What about air dams and spoilers? As a professional would you say that front dams and spiolers are about the only real Aero improvements that make a difference. I can't do a wing because it isn't legal in NY. But my assumption would be that an air damn and spoiler would have to help atleast little, right?

    - - - Updated - - -

    This is in the realm of under 60mph pushing the car to its limits speaking..
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    Candidate for extra wide wheels?

    OK so I have a set of Speedline Mistrals 5x120 with 14.5" rears and 9" fronts (17" rims). I also have a set of 13" rears. These are 3 piece wheels used on some cars in the late 70s eg Ferrari 288 GTO and in the 80s F40. Apparently also briefly on the Shelby Cobra. But the bolt pattern is BMW so I am wondering which BMW, preferably from that era, could use these wheels. Obviously, the horsepower would need to be commensurate otherwise this project would be all hat and no cattle. The offsets are another question, will get to that later. Would an M1 be feasible? Maybe sacrilege to mess with that model. So what does that leave? The 635?

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    The only e36 I've ever seen pics of in a wind tunnel is George Plasa's e36 hill climb car, (I think) designed by floßman (flossman) auto design in Germany. Haven't ever seen any data, though. If I had the money, that would be what I'd get. Properly designed widebody + fat tires will certainly improve lap times over wide tires and and fender flares.

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    Quote Originally Posted by aeronaut View Post
    Very informative post, Terry. I was just wondering if there was an upper limit (within reason) that tire width doesn't help with corner speed. Can you estimate how much per lap reduction per 10mm extra tire width (all else equal)? I know it's a big 'it depends', but is it 10th's of seconds, or halves of seconds for every 10mm increase?
    Well... its not always that simple to test, unfortunately. We have tested the ever increasing tire width principle on other chassis, and we did see somewhat steady incremental drops in lap times for every +10mm, up until we ran out of tire width options at 345mm.



    This is an NC MX-5 we have done some work to for a customer and it has gone from 255 to 275 to 295 tires and it keeps getting faster, and this car is fairly low power. The latest iteration above is on 18x11" wheels. In a Miata..

    One thing you have to worry about with tire width changes are other changes that might be necessary to prevent a problem:

    + Increase wheel width
    + Increase flare size to cover the tire
    + Make sure there is no tire rubbing/cutting at each jump
    + Some jumps will need to be accompanied by spring rate increases
    + At a certain point the spring rate may outpace the valving on the shocks, so you might have damper upgrades
    + Other things like bushing deformation might come into play, brake sizes, etc



    A good example of this was tested on the Corvette above. We started racing this car in TTC, ran it for two seasons. For that car in that class we were very limited on "points" and only changed spring rate and tires. We actually downsized from a stock 275 to a 245mm Hoosier R7 to get enough points back to stay in that class. It won big locally with that setup and reset some class track records by as much as 7 seconds. We had to use the OEM Biulstein monotube dampers, which we had rebuilt by Bilstein USA but could not revalve. Car handled great, easy to drive fast.



    I got a wild hair and cut the fenders, ordered 18x12" wheels for it, and slapped some 335F/345R Hoosier A6 tires on the car, left the rest alone and jumped up to TT2 class. That was a +100mm jump in tire width + a big move in tire compound! First time out we had BIG PROBLEMS and the lap times were no better. I ran it again at a slightly bumpier track, which we had also run before on the TTC setup, and it slowed down from the 245s. This was due to insufficient damping - the OEM Bilstein shocks we had to use in TTC were NO MATCH for the grip levels of the giant tires that pushed us into TT2. The car was bouncing around and scared the hell outta me... we quickly ditched the TT2 idea (it would need $10K in mods to be competitive in that class) and moved it back to TTC and the 245mm tire.



    Because of these "other variables" it is tough to do a series of "+10mm increment" tire tests on the same car, with no other changes. As cars get "more prepped" they tend to have other things changing as tire/wheel width goes up. The car above just jumped up 2 classes simply from aero changes, and we next we are moving up from a 245 mm Hoosier R7 up to a 275 R7, and I will get a back-to-back test on that tire change (two sets of wheels with the two tire sizes can be run the same day). But to go wider than the 275 on this would require a whole new wheel package, new flare package, new front aero package, etc.

    So its tough to put a real number on what each +10mm in tire will do. USUALLY you will get faster, but if you have janky suspension problems or run out of fender room, bad things can happen with more tire/grip.

    Cheers,
    Terry Fair @ Vorshlag Motorsports

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    FWIW my car was roughly 3.5 seconds faster on the same 1.7mi road course after going from 225 Rivals to 285 RE71Rs and Felony Form overfenders.

    Video:

    EF21DD82-BBC4-4C4D-8AAE-323D29AEA50A.jpeg
    Last edited by ccc01; 11-11-2017 at 12:40 PM.
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    Quote Originally Posted by ccc01 View Post
    FWIW my car was roughly 3.5 seconds faster on the same 1.7mi road course after going from 225 Rivals to 285 RE71Rs and Felony Form overfenders.

    Video:

    EF21DD82-BBC4-4C4D-8AAE-323D29AEA50A.jpeg
    Cody - you still have that red M3? Sweet. Car looks quick - lap times? That 3.5 sec improvement is a huge drop in times, and reinforces exactly what I'm talking about. BIGGER TIRES WORK BETTER



    The car above had 18x10s and 285s but it used steel flares grafted onto the body - a TON of work. Show pics of your "Felony" overflares if you can. I'm always looking for new options to stuff 285s under an E36!
    Terry Fair @ Vorshlag Motorsports

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    I was interested in the Hard Motorsports flares until I saw the amount of work necessary to fit them properly Terry. Sucks too since NASA changed the rules and my car is getting forced out of TTC/TT5 and into at least TT4. Would be nice to at least run wider rubber since I'll be at a huge horsepower disadvantage.

    If I'd known what NASA was planning with this rules change I might've just done an S54 swap vs replacing the blown head gasket on my S52. Oh well.

    I'm looking at the MCS' this Friday. Was going to do it this Sunday, but ran out of time/daylight.
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    Quote Originally Posted by DocWyte View Post
    I was interested in the Hard Motorsports flares until I saw the amount of work necessary to fit them properly Terry.
    What? These are relatively EASY to install, especially compared to welded steel flares!



    Even with the rear fender mods we can mod the tub and install a set on an E46/E36 in about 10 hours (the silver E46 shown here took 10.33 hrs total).



    Step by step pics shown for HARD flare install here (E46 Sedan) and here (E46 Coupe).



    Quote Originally Posted by DocWyte View Post
    Sucks too since NASA changed the rules and my car is getting forced out of TTC/TT5 and into at least TT4. Would be nice to at least run wider rubber since I'll be at a huge horsepower disadvantage.

    If I'd known what NASA was planning with this rules change I might've just done an S54 swap vs replacing the blown head gasket on my S52. Oh well.
    Yea not too many people happy with the new ST5/TT5 rules - myself included. Its a HOT MESS with all of the restrictions, new tire measurement methods, etc. Pretty much just made for Miatas, yuck.
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    I guess its a matter of perspective! Compared to metal flares, much easier. For me, as an amateur, doing that level of metal work is a non starter. Which means taking the car to a body shop and paying them to do it. That adds up quickly, especially since all the good body shops here are still drowning in hail repair work and have no time nor desire to take on a specialized, small paying job like this.

    Well, Greg G seems very happy with the TT5 rules! As far as I can tell, they basically just deleted TTC and told all of us to play elsewhere.

    Which leaves me with the option of spending a bunch more money to add power, like a supercharger and bump up several classes, spend a little more money on handling, like these MCS', or just spend no money and try to work on my driving ability and not be competitive at all.
    Last edited by DocWyte; 12-06-2017 at 03:52 PM.
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    Quote Originally Posted by DocWyte View Post
    I guess its a matter of perspective! Compared to metal flares, much easier. For me, as an amateur, doing that level of metal work is a non starter. Which means taking the car to a body shop and paying them to do it. That adds up quickly, especially since all the good body shops here are still drowning in hail repair work and have no time nor desire to take on a specialized, small paying job like this.
    Actually a body shop might not understand exactly what you need here - tire clearance at full bump travel. A race fab shop might be the better option. Remember - the bolt on flares require NO paint and NO bodywork.

    Quote Originally Posted by DocWyte View Post
    Well, Greg G seems very happy with the TT5 rules! As far as I can tell, they basically just deleted TTC and told all of us to play elsewhere.
    Well after all, he created TT5/ST5 it to fit his own car curiously well. And yea, the rest of us are cannon fodder for max built ST4/TT4 cars. I might have to completely start over with a new build for a new class.

    Quote Originally Posted by DocWyte View Post
    Which leaves me with the option of spending a bunch more money to add power, like a supercharger and bump up several classes, spend a little more money on handling, like these MCS', or just spend no money and try to work on my driving ability and not be competitive at all.
    Well I feel your pain - and we're somewhat in the same boat. 630+ pounds too heavy / 100 whp avg down for TT4 but wildly "illegal" now for TT5. To be there in "4" I have to build a wildly more expensive motor ($$$) and hack the car up (weight) to be in the hunt. The rules for TT5 would mean our brand new wing has to be completely remounted, splitter hacked up/removed, and then we would still need to LOSE power from the already anemic 210 whp avg we have. Blah.



    "If I were you"... you should still get the MCS dampers, no matter where you end up. They are SO much better built, super reliable, huge damper adjustment range that is easy to tune, more CONSISTENT compared to twin tubes (that turn the fluid to foam in a handful of minutes), and on and on.



    In case you are wondering, YES, I am trying to sell you MCS shocks but still... its some of the best money you will ever spend on a tracked car (just barely behind "tires"). "Driver mod" is the go-to answer but noobs and experienced wheelmen will appreciate the handling of a proper set of Motorsport monotube shocks.
    Terry Fair @ Vorshlag Motorsports

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    I hear ya. I've been closely following your red car build, really enjoy seeing what you do. With my M3, to compete in TT5, I'd have to remove my splitter, completely remove the oem ltw rear wing (ack!), run the maximum allowable weight AND detune/add a restrictor plate. No thanks.

    Or I'm in the same boat as you in TT4. Vastly overweight and underpowered, the point where I'd need to spend significant sums on both power and weight reduction, which will shove me over the fine line street/track car I've been toeing.

    I also agree with you about the MCS', I'm sure they'll make an appreciable difference. It boils down to what direction I want to take with the car and how much money I can afford to spend. I can afford to buy MCS' and I can afford to buy a used supercharger system but I can't afford both. Doh!
    Last edited by DocWyte; 12-06-2017 at 05:29 PM.
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    Anyone lean the radiator forward and completely duct it out of the hood on the E36 chassis? Seems really tight and wondering if it is worth it. I am running a stock motor in the car.
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    Quote Originally Posted by cledbetter View Post
    Anyone lean the radiator forward and completely duct it out of the hood on the E36 chassis? Seems really tight and wondering if it is worth it. I am running a stock motor in the car.
    What cooling problem are you trying to solve?

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    I think he's trying to make Aero mod by ducting and venting the rad out of the hood vent more than to solve a cooling issue.
    - 96 328is 6.0L. (LS1 to LS2 build thread: http://forums.bimmerforums.com/forum...ad.php?2098938)
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    - 95 ///M3 6.0L. (LS2 build thread: http://forums.bimmerforums.com/forum....php?t=1619249)

    - 97 ///M3. (e46 Fender Flares/track car build thread: http://forums.bimmerforums.com/forum....php?t=1727098)
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    Quote Originally Posted by bimerok View Post
    I think he's trying to make Aero mod by ducting and venting the rad out of the hood vent more than to solve a cooling issue.
    This is more what I was thinking for Aero mod to make more front end downforce or at least reduce front end lift. Just wanted to see if anyone attempted it on a E36 and would love to see some pictures if they have. Terry vented the radiator though the hood on Mustang picture.
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    If the hoodline was very low, or you were also trying to squeeze an intercooler in there (V-mount) then I'd put a serious roll on the radiator. With the existing E36 bodywork you could push the top of the radiator forward a couple inches. Not really enough to make the work worthwhile. The E46 has some more room and could accommodate enough of a roll to put a real duct behind the radiator.

    You could also do it like we did the Silver Roush Mustang. We did a vent in the hood and the bottom half of a duct in the tight space behind the radiator to keep air from going under the car. But didn't do the extra difficult work to bring the duct to the hood. We got 80% of the benefit for about 30% of the work.
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    Quote Originally Posted by modernbeat View Post
    With the existing E36 bodywork you could push the top of the radiator forward a couple inches. Not really enough to make the work worthwhile. The E46 has some more room and could accommodate enough of a roll to put a real duct behind the radiator.
    What if you lopped 2 cylinders off the front of the motor in an E36? More room now? Worthwhile (V-mount)?

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    Quote Originally Posted by jakermac View Post
    What if you lopped 2 cylinders off the front of the motor in an E36? More room now? Worthwhile (V-mount)?
    EJ25 swap if you’re serious.

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