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Downforce options for R35 (road/race)


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#1 35R Posted 19 February 2012 - 02:54 AM

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Hey guys

I've done dozens of track days the past, using stockers, r's and slicks.

However I'm looking to enter an event this year which is constained by tyre grip/wear/load ratings.  The competition calls for tyres with a TQG rating 120 or greater, so we're talking road tyres here.  No R's or slicks.

So my question is, do you think added downforce will help given the low grip provided by the tyre?  Or is it perhaps the answer to yield more grip?...  My gut thoughts are that the limit of the tyre means there is little point adding downforce.  But i would happily be proven wrong.  Intrested on your thoughts along those lines.

Also, what would be the most hardcore downforce options for a relatively standard car?  I don't mind bolting on things at the track, but no cutting or major mods, this is a dailly driver 95% of the time.

Thoughts?



#2 descartesfool Posted 19 February 2012 - 04:52 AM

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Downforce helps in all cases in terms of grip. It doesn't matter what the tire is. Best setup would be from Nordring (really expensive), then Aeromotions, or one like the setup used on the One Lap of America car Lee Keen drove with a big fixed wing. You want to choose setups that were tested added downforce, and not just parts designed for appearance if you actually want downforce without increasing drag so much it negates the benefits of the added downforce. I would just call guys at Aeromotion.



#3 Force 6 Posted 19 February 2012 - 08:52 AM

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hi

Im in the middle of doing somthing similar .  i went with a front lip side skirts and canards now im looking at oprions of rear wings .

Aeromotion, vlotex, apr gtc 500, SunLine racing,

also considering a splitter as well

but still thinking any ideas.

Thanks

steve

Edited by Force 6, 19 February 2012 - 09:00 AM.



09 GTR GTC 3'' intakes, GTC turbo pipes, Ap Dps no cat, stright mid pipes, AAM sport exhaust, 1000cc bosh injectors ,HKS top pipes bovs, GTC tune, 550 / 550
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gear box refresh, intercooler, trans cooler , upgrade turbos

#4 Santorican Posted 19 February 2012 - 09:21 AM

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I don't know very much about what set up is best for the GTR but when I was doing research for our formula sae car I learned that down force can improve the performance of any tire at the cost of increased tire wear as well as operating temps. I haven't really learned how to get around this problem, my guess would be to adjust your suspension geo to a less agressive camber setting to account for the increase in the camber gain as the car's average speed increases.


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#5 Jeremy@SSP Posted 19 February 2012 - 10:35 AM

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The stock RE-070's are a 140 compound if memory serves me correct, but you could also shed some weight running a NONE runflat tire.

Are you still on the oem suspension?? If so, changing those to a more aggressive/higher spring rate, or a full coil over set up, is going to drastically reduce your lap times.

Are you still on the oem sway bars?? If so, changing those out is going to also drastically reduce your lap times as well.


I'm running the Deka Nitron 3+ coil overs, everything Whiteline Racing makes, APR GTC-500 rear wing, stillen front canards, and the Amuse Front splitter. Obviously I did NOT wind tunnel test the car, but my lap times have been drastically reduced (8 sec/per lap faster @ VIR) with the mods mentioned above.


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Edited by Jeremy@SSP, 19 February 2012 - 10:39 AM.



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#6 35R Posted 19 February 2012 - 02:34 PM

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Some good ideas/comments thanks guys.  I actually have used aeromotions before (which was great, may use them again) and i have a set of JRZ's but i am taking a step backwards and asking for opinions.   don't have sways so that is on the cards.

what i don't get is, if the tyres we use (without added aero) slip relatively badly already (vs say a slick or good r compound) will adding downforce really help that much?  if the compound cannot hold onto the tarmac (because it's just not sticky) will adding downforce work?  I suppose it will to a degree.. but the limit of the tyre may dictate the effectiveness/non-effectiveness of the result?



#7 35R Posted 19 February 2012 - 08:25 PM

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 Jeremy@SSP, on 19 February 2012 - 10:35 AM, said:

The stock RE-070's are a 140 compound if memory serves me correct, but you could also shed some weight running a NONE runflat tire.

Are you still on the oem suspension?? If so, changing those to a more aggressive/higher spring rate, or a full coil over set up, is going to drastically reduce your lap times.

Are you still on the oem sway bars?? If so, changing those out is going to also drastically reduce your lap times as well.


I'm running the Deka Nitron 3+ coil overs, everything Whiteline Racing makes, APR GTC-500 rear wing, stillen front canards, and the Amuse Front splitter. Obviously I did NOT wind tunnel test the car, but my lap times have been drastically reduced (8 sec/per lap faster @ VIR) with the mods mentioned above.


.

Can i ask what made you select the GTC-500 wing (have you any pics installed?)  also have you gone through the exercise of tuning the angle?



#8 amfaster Posted 19 February 2012 - 09:53 PM

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 35R, on 19 February 2012 - 02:34 PM, said:

Some good ideas/comments thanks guys.  I actually have used aeromotions before (which was great, may use them again) and i have a set of JRZ's but i am taking a step backwards and asking for opinions.   don't have sways so that is on the cards.

what i don't get is, if the tyres we use (without added aero) slip relatively badly already (vs say a slick or good r compound) will adding downforce really help that much?  if the compound cannot hold onto the tarmac (because it's just not sticky) will adding downforce work?  I suppose it will to a degree.. but the limit of the tyre may dictate the effectiveness/non-effectiveness of the result?


You have to think of DF as changing the balance of the car.  If the rear end isn't sticking it's because you have an imbalance in the grip level on that end of the car relative to the grip level on the front end.  So the front end is sticking more than the rear.  If you add DF to the rear of the car you will increase the grip level (but only at higher speeds like 80+) on the rear end of the car giving you more grip in the back end.

Also think of grip level as horizontal (lateral G) and Vertical (DF).  Vertical pressure on the tire will help grip and lateral G, vs just adding more lateral G.

Sounds like you have an imbalance with your setup somewhere else though if the car is really loose on the back end.  The GT-R's tires and other street tires with high treadwear are still pretty grippy.



#9 Santorican Posted 19 February 2012 - 10:10 PM

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I've always been taught to always balance out the car at the tire first, get the best compromise tire for whatever your budget, setup, goals, etc... are and then change your tire size and if you can change your suspension geo. Then balance out the car with sway bars as they lower your overall grip of the car. As for aero you'll have to factor that into your tire choice from the beginning but that is beyond my knowledge. There are a few good books on racecar aerodynamics that I can recommend if you're interested.


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#10 Jeremy@SSP Posted 19 February 2012 - 10:53 PM

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 35R, on 19 February 2012 - 08:25 PM, said:

Can i ask what made you select the GTC-500 wing (have you any pics installed?)  also have you gone through the exercise of tuning the angle?


I chose the APR for a couple different reasons, but mainly cause the price wasn't over the top.  I wasn't trying to spend 5-7 grand on a Aeromotion. Also, a couple racing friends of mine use these on there Evo's and Subi's, and have had good results, and the quality is top notch.

And yes, I've change the angle depending on tracks, and it really does make a difference. For example....I had the wing fully cranked down for a track event and forgot to change it back to Daily Driving mode. Lets just say I burned almost a full tank of gas on my way home when I'd normally burn a 1/4 tank.




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Edited by Jeremy@SSP, 19 February 2012 - 10:59 PM.



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#11 MindlessOath Posted 19 February 2012 - 11:10 PM

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here is a little reading from a good source. http://www.racecar-e...s-aerodynamics/

here nordring has a rear diffuser - used google translate to translate the japanese. its for pre 2012 gtr's.
http://www.vollstrom...parts_r35r.html
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It has been said more than 10 percent increase rear downforce Riyabyu 11 years has changed a lot of models, standard car, and was also up cooling effect.
In the Nord link brand, we also manufacture can be mounted 07 to 10 models, the rear bumper 11 model under wind. By combining the diffuser extension, stable running speed balanced before and after UP, in addition to mounting the front lip spoiler and rear downforce in addition to significant design aesthetics is promised.
With everyone doing all sorts of custom work all around maybe someone can make something similar in a different design.

Here is "the tuners group" intro to aero.
http://www.tunersgro...aero_intro.html

here is the aerodynamics of the R35 gt-r by the man himself Yoshi Suzuka. you could email him and ask him some questions, very nice guy. http://www.suzukaracing.com
http://www.nagtroc.o...nissan-r35-gtr/

there are many many many GT wings for the R35 - too many to list. some tested on the R35 and others that are generic that will work you just have to figure out the settings you want to use. check out http://www.speedfors...erior-c-29.html and http://www.gt-rr.com...&category_id=20

only a few front diffusers, i found the esprit one interesting and well tested, they didnt release this product for a long time of testing, i would imaging if there was data it would be in Japanese and in something like Option magazine, or maybe a vendor could find out if they sell esprit parts (would that help brake temps?)
http://www.gt-rr.com...y_carbon&id=985
then you got aeromotions and willall and custom versions like the one TOP Speed used on the one lap of America.

aero can be used to do many different things ;)

anyways, i usually read racecar engineering its a good magazine and worth buying a subscription. they have an aero subject every release. you can probably find the magazines in pdf format online if you google them.

found an article in pdf format for - Ground Effect Aerodynamics of Race Cars - http://eprints.soton...tPDFServlet.pdf

Edited by MindlessOath, 19 February 2012 - 11:17 PM.




#12 35R Posted 20 February 2012 - 01:00 AM

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wow thanks guys, thanks reading for tonight!



#13 descartesfool Posted 20 February 2012 - 11:47 AM

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 35R, on 19 February 2012 - 02:34 PM, said:

Some good ideas/comments thanks guys.  I actually have used aeromotions before (which was great, may use them again) and i have a set of JRZ's but i am taking a step backwards and asking for opinions.   don't have sways so that is on the cards.

what i don't get is, if the tyres we use (without added aero) slip relatively badly already (vs say a slick or good r compound) will adding downforce really help that much?  if the compound cannot hold onto the tarmac (because it's just not sticky) will adding downforce work?  I suppose it will to a degree.. but the limit of the tyre may dictate the effectiveness/non-effectiveness of the result?

Aerodynamic downforce works in the following way. Assume the car weights 4000 lbs with driver and part fuel, and has about 1000 lbs pressing down on each tire while at rest. when you corner without aero, load transfers from the one side of the car such that you have say 1500 lbs on one outside tire and 500 lbs on one inside tire. If the tires can have 1 G of lateral grip, then each tire will produce a sideways force equal to its vertical load. so total sideways force is 1500 + 500 lbs or 2000 lbs per axle and car corners at 1G. Actually because of the way tires behave, the grip or lateral force is not linearly related to the vertical load, and the more heavily loaded tire will make perhaps 5% less lateral force than its vertical load while the less loaded tire will make perhaps 5% more than its vertical load. That means the tire with 1500 lbs on it makes 1425 lbs of lateral force while the inside tire makes 525 labs of lateral force, for a total of 1950 lbs of lateral force per axle, so car is actually cornering at 1950/2000 = 0.975 G's. Now add aero such that you have 400 lbs of downforce at some high speed, and that it is balanced over the front and rear axles, so 200 lbs on the front axle and 200 lbs on the rear axle. That means an added vertical force on each tire of 50 lbs. The vertical load is now 1500 + 50 = 1550 lbs on the outside tire and 550 lbs on the inside tire. Lateral force will still be very close to 95% of vertical load on the outside tire and 105% of vertical load on the inside tire, although in actuality very slightly less due to tire characteristics, but not enough to worry about. That means the outside tire generates 1550 * 0.95 = 1472.5 lbs of lateral force and the inside tire makes 550 * 1.05 = 577.5 lbs of lateral force for a total of 2050 lbs of lateral force. Now since the mass of the car has not changed and is still 2000 lbs per axle, the car will be cornering at 2050/2000 = 1.025 G's vs 0.975 G's without aero. Free grip! It does not matter what tire you are using, as the effect will be the same. Aero increases vertical load on the tire, and that means it increases lateral grip almost in the same % as the % increase in vertical load. Even if the tires have low grip to start with, the increase in vertical force from the aero will provide the same benefit. what counts is the % downforce in lbs relative to the weight of the car. In my example, I assumed grip downforce was equal to 10% of the car's weight, and that increased the G's by 1.025/0.975 or about 5% more grip. If you started with a tire that produce only 0.8 G's, the same downforce would bring grip up 5% to 0.84 G's, while if you started with a high grip tire that gave you 1.2 G's, the downforce would increase that by 5% to 1.26 G's. this example is just a back of the envelope type calculation, but it shows the concept of how downforce increases grip for any tire, any car.

In terms of downforce increase at the front, the most gain comes from changes to the airdam and not from the extension of splitter. You either extend the airdam down to reduce air from going under the car or you lower the car or both (tactually you are trying to reduce the pressure under the car and increase pressure over the hood. The splitter helps improve the downforce over that gained from the airdam alone, but just adding a splitter extension to a stock height car and airdam will not give much increase in downforce. If you are sticking with the stock airdam, I think the new Aeromotions splitter extension looks like the best bet. As for rear downforce, the wing type, its height off the deck and how the airflow goes around the car to feed the wing will determine the downforce added. Since you can't do anything to the flow of air onto the wing, your choices boil down to the choice of wing and how high it is above the trunk lid. Buy a wing from a company that is in the business of making downforce and not just appearance. APR wings are a great choice and used on many race cars. I was just at the Toronto Auto show and looking over a Hyundai Genesis race car the had an APR wing on it. It won the manufacturer's championship in its class for 2011 and set a class lap record at Mosport. So I would say buy a rear wing from a company that makes wings for real race cars.



#14 35R Posted 20 February 2012 - 12:46 PM

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 descartesfool, on 20 February 2012 - 11:47 AM, said:

Aerodynamic downforce works in the following way. Assume the car weights 4000 lbs with driver and part fuel, and has about 1000 lbs pressing down on each tire while at rest. when you corner without aero, load transfers from the one side of the car such that you have say 1500 lbs on one outside tire and 500 lbs on one inside tire. If the tires can have 1 G of lateral grip, then each tire will produce a sideways force equal to its vertical load. so total sideways force is 1500 + 500 lbs or 2000 lbs per axle and car corners at 1G. Actually because of the way tires behave, the grip or lateral force is not linearly related to the vertical load, and the more heavily loaded tire will make perhaps 5% less lateral force than its vertical load while the less loaded tire will make perhaps 5% more than its vertical load. That means the tire with 1500 lbs on it makes 1425 lbs of lateral force while the inside tire makes 525 labs of lateral force, for a total of 1950 lbs of lateral force per axle, so car is actually cornering at 1950/2000 = 0.975 G's. Now add aero such that you have 400 lbs of downforce at some high speed, and that it is balanced over the front and rear axles, so 200 lbs on the front axle and 200 lbs on the rear axle. That means an added vertical force on each tire of 50 lbs. The vertical load is now 1500 + 50 = 1550 lbs on the outside tire and 550 lbs on the inside tire. Lateral force will still be very close to 95% of vertical load on the outside tire and 105% of vertical load on the inside tire, although in actuality very slightly less due to tire characteristics, but not enough to worry about. That means the outside tire generates 1550 * 0.95 = 1472.5 lbs of lateral force and the inside tire makes 550 * 1.05 = 577.5 lbs of lateral force for a total of 2050 lbs of lateral force. Now since the mass of the car has not changed and is still 2000 lbs per axle, the car will be cornering at 2050/2000 = 1.025 G's vs 0.975 G's without aero. Free grip! It does not matter what tire you are using, as the effect will be the same. Aero increases vertical load on the tire, and that means it increases lateral grip almost in the same % as the % increase in vertical load. Even if the tires have low grip to start with, the increase in vertical force from the aero will provide the same benefit. what counts is the % downforce in lbs relative to the weight of the car. In my example, I assumed grip downforce was equal to 10% of the car's weight, and that increased the G's by 1.025/0.975 or about 5% more grip. If you started with a tire that produce only 0.8 G's, the same downforce would bring grip up 5% to 0.84 G's, while if you started with a high grip tire that gave you 1.2 G's, the downforce would increase that by 5% to 1.26 G's. this example is just a back of the envelope type calculation, but it shows the concept of how downforce increases grip for any tire, any car.

In terms of downforce increase at the front, the most gain comes from changes to the airdam and not from the extension of splitter. You either extend the airdam down to reduce air from going under the car or you lower the car or both (tactually you are trying to reduce the pressure under the car and increase pressure over the hood. The splitter helps improve the downforce over that gained from the airdam alone, but just adding a splitter extension to a stock height car and airdam will not give much increase in downforce. If you are sticking with the stock airdam, I think the new Aeromotions splitter extension looks like the best bet. As for rear downforce, the wing type, its height off the deck and how the airflow goes around the car to feed the wing will determine the downforce added. Since you can't do anything to the flow of air onto the wing, your choices boil down to the choice of wing and how high it is above the trunk lid. Buy a wing from a company that is in the business of making downforce and not just appearance. APR wings are a great choice and used on many race cars. I was just at the Toronto Auto show and looking over a Hyundai Genesis race car the had an APR wing on it. It won the manufacturer's championship in its class for 2011 and set a class lap record at Mosport. So I would say buy a rear wing from a company that makes wings for real race cars.

Some great points, i think it makes sense.  Add vertical load and we get more grip.  What if the tyre is at it's limit of grip at the newly (aero-enhanced) vertical load?  Surely the amount of road holding before a tyre lets go is dependant on the compound too?  Isn't there a point of diminshing returns depending on a lot of variables, one being how sticky the tyre is?  Or is it the case that the increase in grip on the un-laden side compensates well enough to make a huge difference.  Also, what if we are at the limit even on the un-loaded side (perhaps that is not possible, given the load v un-loaded ratios).

Some other good points about aero and splitters.  I do wonder how much of conventional wisdom applies to the R35, given the exceptional job Nissan did with the undertrays and everything else on this car.  Do you think there is much point trying to enhance the pressure directed under the car etc with airdam mods, splitters and diffuser alterations?  I just wonder if we will screw up the whole aero package of the car.

With the wing, i will check out the APR stuff.  Do you think there is any point looking into vortex generators for the top of our car (roof)?

Edited by 35R, 20 February 2012 - 12:50 PM.




#15 MindlessOath Posted 20 February 2012 - 03:12 PM

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Aero can always be improved. Don't read too much into messing the aero up with proven parts. The aeromotions have been heavily tested. Those parts for image might help but many never tested to know.
descartesfool's post is very good advice! Nissan has mentioned in a very old interview the car did perform better lowered. And when using the aeromotions splitter you keep the stock lip as a sort of air damn instead of turning the lip into a splitter like others do. Nissan also mentioned better performance on 19s... But had to choose higher settings and 20s for multiple reasons of a mass market sale.



#16 5150 Racing Posted 20 February 2012 - 11:16 PM

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The APR wing on our GTR broke Twice...
The wing pushed itself Down thru the bottom layer of carbon.....
Twas no bueno


previously known as Jon @ COBBSoCal.
PM If needed!!
https://www.facebook...JonJeebusTuning
@bakaunchi


#17 MindlessOath Posted 21 February 2012 - 12:03 AM

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Check out youtube for broken Apr wings. Iirc its common. There was a thread on nagtroc about it...

http://www.nagtroc.o...ilure-at-speed/
Enjoy



#18 RPM Posted 21 February 2012 - 09:08 AM

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The Amuse aero package "looks" like it might be effective at producing downforce. Unfortunately I don't have any data to back up my gut feeling. Does anyone have any data on the Amuse aero package?



#19 MindlessOath Posted 21 February 2012 - 01:32 PM

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Iirc amuse posted before and after laptimes with its aero kit. That's the only data. Its canards are just for image as they reduced lap times.



#20 Jeremy@SSP Posted 21 February 2012 - 02:13 PM

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 Jon @ COBB Socal, on 20 February 2012 - 11:16 PM, said:

The APR wing on our GTR broke Twice...
The wing pushed itself Down thru the bottom layer of carbon.....
Twas no bueno


Was it chassis mounted or just bolted to the trunk ??


.


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