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Back to back testing of DBJ Aero - GT4 Clubsport MR at Road America
Back to Back Testing of DBJ Aero
Charlie (DrJupeman here on RL) and I have bought a car to go endurance racing in 2021. We will be campaigning a 2016 GT4 Clubsport MR in either AER or WRL. With both of these series, the aero rules are pretty much non-existent. Rather than run the MR aero package, we thought that the DBJ aero might provide a bit of an advantage.
Figure 1 - Exiting T6 and looking planted!
This past Labor day weekend, we went to Road America to shake down the car and do the aero testing. Our goal was to do a true back-to-back test with the same drivers on the same track. We got a bit lucky that the conditions were the same all weekend. We ran the MR aero all day on Friday, and then swapped on the DBJ wing and canards for Saturday morning. We took some of Saturday to get the setup right with the DBJ wing, adjusting the angle several times. But made no other changes to the car; shocks & sways were let at the same setting for the entire weekend. We ran out of time to fit the front splitter and the rear diffuser, but will add these at a later date.
The installation of the DBJ bits is very straight forward. The brackets are robust and the hardware is all stainless steel. Everything bolts up using factory holes & studs, so no modifications to the car are required. The wing is a beautiful piece and just looks the part. The question is, would it make any difference?
The answer is yes, it did! Even without the front splitter or diffuser, we were able to run 1.2 seconds faster posting a 2:28.3 vs a 2:29.5. Those times would have been good enough to qualify P2 at the WRL race in 2019. Remember, we were running on 180 UTQG rated tires; obviously slicks would be a lot faster.
When looking at the Motec data, you can see the speed difference in the higher speed turns like the carousel and the kink. This we pretty much expected.
Figure 2 - Speed delta in the carousel & kink
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But what was very surprising to us was that the top speeds with the DBJ wing were actually a higher by 2-3 mph on the straights. We had feared the larger wing would slow top speeds. But because the wing is so large, we were able to run at a lower angle of attack and still yield good downforce vs the MR wing. The higher exit speed also helps.
Figure 3 - Speed comparison down the back straight
Overall we are very happy with the DBJ aero, and can’t wait to try the splitter and diffuser at a future event. We are also really excited to run the car in a race in 2021!
Figure 4 - No matter what aero you run, you gotta be tight to the apex!
I should mention we still paid for these parts so this is not a paid review. Jacob was kind enough to give us a discount for running the DBJ logos on the car.
This is an onboard from me in the 117 C5 Vette running Hankook RS4s from the 2019 WRL race. We are in GP1 trim making ~290whp and low downforce home made aero package.
My Vmin thru the kink is 113mph and 84mph around the carousel. No where close to your straight line speeds though with a Vmax of 136, were you guys detuned for GTO power levels already? What 180TW tires did you guys test on? We are looking to move to GTO in the 2021 season!
Can not wait to get my 4 out to RA! I still need to verify fitment of splitter of the @DesignsbyJacob on the 718 before squeezing the trigger on the wing.
I bought the kit as well for my road registered track car. As well as the front lift kit. A word of caution. On the first track outing the front splitter bent down over 200kph to actually touch the ground and the proceeded to porpoise up and and down with massive vibration. I did just two laps and it had bent the quite strong brackets, ripped a small front PU mount on the front bumper and actually pulled down the front metal floor. So it does generate plenty of downforce for one lap. We re-engineered the whole thing. The key problem is the splitter carbon sheet is only 3mm thick. we bonded a 4mm additional carbon sheet to it and cut and trimmed to size, drilled out the holes and straightened the brackets and floor plus added two stays coming straight down from the aluminium front bumper bar. We also installed a new OEM splitter so it seals well against the new carbon splitter/floor. It's now strong and effective. I removed the large canards at Bathurst as they were causing a weave at the +250kph bend coming into the Chase (the offside canard loses airflow coming into that corner) and the splitter alone does a good job.
The car was very good at Bathurst but lost some top speed (about 7 kph) as you would expect with a bigger wing (I went with the standard mount new carbon wing, on RSVN risers, which does look trick)
The lift kit also needed extensive re-engineering to get it to work properly and I've been through that with Jacob so he can respond if he chooses.
Last edited by Warwick Morris; 12-23-2020 at 06:22 PM.
I bought the kit as well for my road registered track car. As well as the front lift kit. A word of caution. On the first track outing the front splitter bent down over 200kph to actually touch the ground and the proceeded to porpoise up and and down with massive vibration. I did just two laps and it had bent the quite strong brackets, ripped a small front PU mount on the front bumper and actually pulled down the front metal floor. So it does generate plenty of downforce for one lap. We re-engineered the whole thing. The key problem is the splitter carbon sheet is only 3mm thick. we bonded a 4mm additional carbon sheet to it and cut and trimmed to size, drilled out the holes and straightened the brackets and floor plus added two stays coming straight down from the aluminium front bumper bar. We also installed a new OEM splitter so it seals well against the new carbon splitter/floor. It's now strong and effective. I removed the large canards at Bathurst as they were causing a weave at the +250kph bend coming into the Chase (the offside canard loses airflow coming into that corner) and the splitter alone does a good job.
The car was very good at Bathurst but lost some top speed (about 7 kph) as you would expect with a bigger wing (I went with the standard mount new carbon wing, on RSVN risers, which does look trick)
The lift kit also needed extensive re-engineering to get it to work properly and I've been through that with Jacob so he can respond if he chooses.
Hey Warwick! I wish you reached out to us about the splitter. We've been adding internal splitter rods to our splitters for quite a while now. We did not realize that you were dealing with this issue! The downforce that the splitter generates actually varies a lot with front ride height. Most of our initial testing was done on a street GT4 so we didnt have issues with the splitter at 4" off the ground and even on track. However when the splitter was run at 2-2.5" off the ground which is typical of the clubsports and other race cars, we realized the need to add additional support due to the significant increases in downforce generated. FYI, the downforce can spike up about 50% at those heights and exceeded what we initially designed the splitter to carry. That said, the internal splitter rods split the downforce load to another point on the chassis (crash beam) and since then we haven't had an issue even at race heights. This was quite important as the chassis studs can be overloaded at speeds above 140mph especially over repeated loading and unloading. The splitter mounts were also increased in strength to add additional safety margin for endurance racing.
As for the lift kit, the installation and proper restraint of the aircups and air hoses is key. Because of the macpherson style front suspension, the aircups spin when the car is turned. If not restrained properly, or checked during install, sometimes the hoses could possibly come into contact with the tire and cause a leak. We usually tell all our installers to check full lock left and right. That said, only a couple (2) of reports of this happening so far. We like what you did with your modification though to lock down the air cup.
Hit me up with a DM. We can go over the splitter to make sure you guys are set!
09-29-2020, 08:51 PM
Back to back testing of DBJ Aero - GT4 Clubsport MR at Road America
