mobonic

I got my parts from james @ GMG from WC/ALMS car.

I went with the full package: Grand Am fenders, bumper and splitter.



The bottom is flat with the exception of 2 brake ducts that feed into the Cup brakes ducts that attach to the LCA perfectly.

These splitters run about $1500 (carbon).

The RSR are not allowed to run them in alms 2010 and previous, which is why porsche made a front ducting and aero upgrade for 2009-2010 to try to add more front downforce. Those pictures of the new 2012 RSR might be updated because of a rules change or because those are euro spec builds.

I guess we will have to wait and see until 2012 alms, as these new RSR's will not run in the 2011 season.



Front splitters make a huge difference, especially with 911's that have giant rear wings.. balance is everything.

TudorMiron

Agree absolutely about balance. Glen nailed it spot on – you can add only that much rear downforce as front allows also because adding rear wing normally reduces front axle load due to cantilever effect. So in every racing category that I was working that was largely aero dependant (formula’s, sport proto’s) front aero was main issue (you could always put more wing/angle on the rear but with front it’s not that easy) and we had to take care that front is feeding the rear diffuser properly.

Thanks
Ted

mobonic

Ted,

Where are you located.. would love to pick your brain, Im aero-retarded.

James-GMG

Ted and all.......this is what I know and ironically enough, I am typing this response while on the plane heading to the Daytona tests driving a new 2011 Rolex spec car running the stock splitter as delivered on the 2010/2011 Cup.

The setup I sold Mobonic was used on our 2009 WC cars and then on our WC spec ALMS GTC car in 2010. We then switched to the CUP S Setup mid-year that was used in Grand Am the past 2 years, starting in 2009. Prior to that, GA used the slightly smaller version of the 2008/2009 WC spec that Mobonic bought. Keep in mind, GA uses the smaller Crawford rear wing vs the Cup S and now stock Cup wing in the new 2010/2011 Cup cars.

We used the WC splitter in 2009 in WC because the grip of the Toyos was so much less than the slicks that the front end needed so much more down force to get the front to stick/turn/etc.
Then last year we tried the stock splitter on the 2010 car at WG with the Toyos and it was an understeering nightmare........we redesigned the splitter system and have modified it to make it similar to the Cup S slider system for adjustability with the undertray and aero affects. For 2011 we have that system in place with some more modifications and plan to test it in a month or so as we are now running on Pirelli slicks.

Either way, I have all those options in stock if you are looking for that upgrade.

TudorMiron

Mobonic, I'm in moscow/russia Many thanks for kind words. I know several VERY knowledgable (experience F1, IRL, CART, ALMS prototypes) people in States – you may want to talk to them.

It's interesting how regulations form the cars shape (aerodinamicists have to comply)
Looking at current GT3 R and GT3 RSR what strikes first is absence of rear diffuser on RSR – if I remember it right diffusers a illegal in GrandAm?

RSR

R

Looking at the front we see that RSR has simple front air dam with replacable skid plates where R has pronounced splitters but no splitter in the central area – looking for beeter flow to rear diffuser?


RSR

R

If tech. reg. allow I would highly recommend looking into adding rear diffuser and changing the position of of rear wing. In GT3 they have to position it 50mm forward of rear most part of bodywork. If allowed than it would be wise to machine new wing stands and move the wing rearwards and lower – it will allow to get same downforce with less AoA -> better L/D ratio. Also more rearward and lowered wing would start extracting air from diffuser which would help a lot. Rear diffuser (especially when working together with rear wing) is the list expensive in terms of drag aero device.

Also interesting to compare 08 and 09 R and RSR rear wings. 08 is somewhat simple “anhedral” design – it has lower AoA behind body and higher AoA in clean air. This is due to air travelling past rear window is moving downwards at an angle so effective AoA is actually higher than at the edges of the wing. This anhedral shape takes it into account. I suspect that this 08 RSR wing (available from Gatty) might have better L/D than 2010 Cup wing, even being 2” shorter in span. 09 wing is much more tricky – definitely looks like designed in CFD using optimization software. It also features unhedral shape but more “gentle” and has sharp decreasing of AoA near the end plates and may be even (it’s hard to tell by looking at picture) reduction in cord length there – this is usually made in order to reduce strength of vortexes that are generated by wing tips –> reducing drag.


08 front/rear (again – no diffuser)

Also 08 front bumper is very simple with no splitter at all in comparition to newer designs.

I know that all this is very simplistic stuff but might be of interest to someone…
Thanks
Ted

mobonic

Guys if any of you are on the fence I would get some of these from James @ GMG ... if you are allowed to run them in your race class and are not running these front splitters you are leaving some on the table.

In my race class its all HP/weight open, so I need every help I can get running against more powerful cars.

TudorMiron

Thanks James! This is VERY practical and informative. BTW are you referring to Toyo Cup 250F/280R tires that provided such little grip? Sorry for my ignorance – I’m not aware of most of US tech. regs.

Thanks
Ted

mobonic

He was referring that WC (World Challenge) dictated that all cars had to run on spec Toyo R888 tires.

But this year they have a new spec SLICK tire from Pirelli that all cars will be using.

It was such a waste to see these great WC cars run on R888's.. so I cant wait to see what these cars do on slicks.

Cory M

Here's the article on the RSR splitter comparison, sorry for the poor quality I had to change the format so it would attach. If you like it you should check out Racecar Engineeiring magazine, some other recent sportscar aero articles include looking at wing height adjustments on a Lotus Exige and splitter height on a Ferrari F430.

Cory M

here's a better look at the text, hopefully it's easier to read:

TudorMiron

Thanks for the article Cory - very educative.

Thanks
Ted

claykos

Thanks for posting!

The coefficients are based on the frontal areas (according to the article) so let's assume the frontal area is about 2 m^2...

Then with a Cl of 0.5 means at 50 m/s (about 110 mph) the cars make about

(1/2)*density*speed^2*area*Cl

.5*(1.2)*2*50*50*.5

=1500 newtons of total downforce...which is only 337 lbs. Not much.

With Cl of 0.6 you get 1800 newtons or about 405 lbs...

Again, not much!

At 60 m/s (~135 mph) you get
485 lbs with 0.5 Cl
or
583 lbs with .6 Cl.

Cory M

here's the follow-up article on rear wings for the rsr, nice gains to be made if you aren't restricted by the rules...

https://rennlist.com/forums/racing-a...ve-wing-9.html

Rickard 993 Turbo

very intressting

Im going to use both a splitter, and diffrent wing for my 997 turbo RSR

simonmurray01

Hi All,

On my 996 cup, we got a 0.7s gain in back to back testing around a pretty short track (1m04s) by fitting the Crawford Composits wing over the stock 996 cup wing.

We also fitted the Crawford front splitter which evened up the balance but didnt have a back to back test to see lap time difference.

My estimate is the the wing and splitter pacgage is worth at least a second on the short track, more on a longer, high speed track.

Regards,

Simon