[Editor’s Note: This article originally appeared in the December 2015 issue of Grassroots Motorsports.]
Erich Heuschele
manager/DR, SRT vehicle dynamics
dodge.com/srt
The best-performing Dodge Challenger for autocross is the SRT 392, specifically the 2015 and 2016 models. It has the Hellcat’s big, sticky, 275mm-wide Pirelli P Zero tires and monster brakes, adaptive shocks from Bilstein (which are very firm and race-tuned in Track Mode), and a 485-horsepower engine. However, its front axle load is 200 pounds lighter than the Hellcat’s. On autocross and road courses less than 2 miles long, it doesn’t give up any lap time to the supercharged Hellcat model.
Second choice: any Challenger with the most aggressive Bilstein passive monotube shock package from the 2011-and-newer 392. This package has trickled down to the later SRT Core models, the Scat Pack and the R/T equipped with the Super Track Pack. You can identify whether you have this package by the color of the shocks: The Bilsteins are yellow instead of black.
The SRT cars, including the brake pads, tires, suspension and cooling systems, are track-ready from the factory. We verify that every SRT model can handle 20-minute track sessions in 100-degree ambient temps with a pro driver. That means the brakes won’t go away, the driveline won’t overheat, the ESC system won’t have problems, etc. We also run 24 hours of track durability at Nelson Ledges with the car absolutely stock. We test for brake fade at Gingerman, where some of our high-profile and more expensive competitors lose brakes in just three laps.
The stock SRT brakes hold up very well for road course track days and autocrosses, as they get a decent amount of air from the SRT fascia. The R/T Super Track Pack brakes (the old police package pad compound) also perform great at Waterford Hills and Grattan. However, cooling ducts may be needed for them to run a full green-flag session without fade; it depends whether the track is very demanding on brakes, like Gingerman, and how aggressive the driver is.
To meet our acceptance criteria for engine cooling, an engine can’t exceed 250 degrees Fahrenheit in a 20-minute track session on a 100-degree day with a pro driver and essentially no traffic slowing down the lap times. Spencer Caudle, SRT steering systems engineer and Trans Am racer, hasn’t noticed any issues yet with the cooling system or wheel bearings. Between his two Challengers, he’s driven about 30,000 street miles and 3000 road course miles.
Still, cars can be made faster with racing tires, racing brake pads and engine mods. The 2015 SRT models have the six-pot Brembos with huge two-piece rotors, so you can’t fit a rim smaller than 20 inches. If you have a car with the four-pot Brembos, you can fit 18-inch rims over them and run a smaller-diameter tire for a weight and gearing improvement.
For non-SRT cars, sticky tires are still the upgrade with the most bang for your buck. Cars without Brembo brakes will benefit from racing brake pads and high-temp fluid. After that, we’d upgrade the stock Sachs twin-tubes to more aggressive shocks.
To prep a standard-issue Challenger for a track day, add performance brake pads to resist fade, like the old police package or ones from the aftermarket. The new police pursuit model now has some big, very capable, non-Brembo sliding calipers and big rotors that are as fade-resistant as the four-pot Brembos. Mopar will soon be offering them as an upgrade package.
If it isn’t 100 degrees outside, the R/T 5.7-liter system seems to handle summer track days at Gingerman and Waterford Hills just fine. If cooling is a problem, you could install the SRT radiator, which has even more capacity than the police package.
Manual-transmission cars have the Tremec TR-6060 transmission and larger rear differential (Getrag or ZF, depending on the year) with limited slip. If you want real limited-slip technology rather than simply dragging the inside-rear brake to limit wheelspin, you could install the SRT differential and halfshafts.
Note: Installing different brake packages that change the torque output of the brake corner can throw off the ABS/ESC calibration. They’ll usually still work, but you may give up some refinement in how the system operates.
Photography Credit: David S. Wallens
Non-SRTs use either voided or hydro front tension strut bushings (depending on model year) that are good for comfort but reduce response. SRTs use solid rubber bushings in that position. Also, pre-2011 cars have much softer front lower lateral link inner bushings. They can be upgraded with the newer part, which is three times stiffer, to help with camber compliance. All Challengers got more negative camber for 2011 through changes to the suspension arms and knuckles, so be careful when mixing and matching parts from different model years.
The stock passive Bilsteins–firmer for 2011 and up compared to 2008-’10–are a great upgrade and easy to install on a non-SRT. SRTs have the same sway bars as the V8s: 30mm front and 18mm rear. The police package uses a 20mm rear sway bar if you want to loosen the car up even more. 2015 cars get lighter, hollow 32mm front and 19mm rear sway bars that have the same stiffness. Hellcats use a heavy but stiff 34mm solid front and 22mm solid rear if you want it really flat.
The SRT uses unique front and rear knuckles to mount the fixed caliper brakes, allowing for more aggressive steering geometry and more tire clearance. Putting them on requires going to the SRT brakes, though, so it is a lot to switch over. Note that non-SRT models use 20×8-inch wheels. SRT models have 20×9- or 20×9.5-inch wheels that will rub in the front if installed on a non-SRT; adding a small wheel spacer or upgrading to the SRT knuckle will solve this.
Wheel bearings and ball joints on any car should be checked regularly when doing performance driving events.
Besides the upcoming police brake package, the stiffer lowering springs from the Mopar catalog drop the car an additional three-quarters of an inch over the SRT, which is already half an inch lower than the non-SRT model suspension. We have run them on every version of the SRT with both passive and adaptive Bilsteins. They are stiff enough to require at least the stock SRT Bilstein shock if you put them on a non-SRT model.
For the engine, the Mopar exhaust and cold-air intake are nice to have. Aside from the 2015-and-up 6.4-liter and 6.2-liter cars, Challengers are pretty quiet and hard to hear on track. Having as much feedback as possible from the steering, brakes and engine is always good for the driver to get the most out of the car.
Scat Pack Stage 1, 2 and 3 kits are great starting points and get you a solid foundation to really go wild down the road–stroker kits, superchargers, etc. You can also buy a lot of the components separately if you’re piecing together a build. Parts like our CNC-ported 5.7 heads (P5160027), performance 5.7-liter camshaft (P5160018) and performance spring kit (P5160074) are designed to take your power production to the next level. And be on the lookout, because Mopar’s got a lot of parts coming down the pipeline.
Spencer tried a few combinations of three-season street tires, trying to reduce rotating inertia with wheels and tires that are lighter and smaller in diameter. However, he always had very similar lap times back to back with the stock 245/45R20 Goodyear F1 and didn’t have to worry about clearances. With an 18-inch wheel, shorter 245/45R18s worked well to keep the sidewall height down, but we wouldn’t recommend running them on the street due to ground clearance issues and the speedometer/odometer reading fast.
To get the ultimate track performance, Spencer has run 275/40R18 competition tires on 18×9.5-inch wheels, but that meant carefully checking suspension and body clearances. We’ve also crammed 285/35R20 tires on 20×10-inch wheels for One Lap of America, but we had to roll the fender lips. In Trans Am, Spencer runs 315/30R18 tires on 18×10.5-inch wheels, but those require extensive body modifications to be legal.
Challengers may be big, heavy cars, but they can dance. So once you’ve learned the fundamentals of performance driving from a good driving school or instructor, always be thinking and looking three steps ahead. Start to initiate maneuvers a bit earlier than might feel natural at first.
To show that it’s not ridiculous to Solo the Challenger, here is a video of me during the autocross competition at the 2011 One Lap of America. We finished second out of seven in class and 21st out of 71 overall. Not bad for a 4400-pound car with driver on street tires and the stock suspension.
Photograph Courtesy Dodge
Comments
Duke
MegaDork
12/10/20 9:07 a.m.
Erich Heschele is a name I haven’t heard since my old neons.org days! Glad he’s still around.
See them more and more as rentals, not always the best sign
I know Dodge constantly gets picked on for antique platforms, adding power to everything for no reason, etc., but you have to love how helpful they are when asked how to track their cars. Most OEMs talk a lot about maintaining factory warranties and “did you see the new rocker panel applique that looks track ready!” while meanwhile Dodge is like “You know it might screw up the stability control to do this but don’t you want to go fast you wuss!”
350z247
New Reader
12/10/20 2:14 p.m.
250 degrees?! I’m taking a cool down lap if any temperature hits 225 then upgrading something before the next time out.
350z247 said:
250 degrees?! I’m taking a cool down lap if any temperature hits 225 then upgrading something before the next time out.
There is nothing wrong with oil temp that high. Synthetics can handle 300.
When I had my 135i the stock oil cooler thermostat didn’t even partially open until the oil is 230-235° the goal was to keep it between 235-250 for efficiency.
350z247
New Reader
12/10/20 4:24 p.m.
In reply to z31maniac :
They didn’t specify if it was oil or coolant, but I assumed it was oil. I’d still rather stick at or under 225. If the gauge says 225 at the sump, it might be much higher somewere else in the engine. I know the oil can handle it, but it makes me uncomfortable.
For your example, I don’t trust modern BMWs and their cooling. BMW has adopted an “as long as the engine makes it out of warranty, we don’t care” mindset. I realize emissions standards are strict, but running coolant temps in the 220-230 range at over 20PSI is too much for an engine to last. I modified the oil cooler and thermostat in my wife’s E70 X5M to have the oil and coolant sit closer to 200-210 degrees. I don’t want to replce my rubber hoses every 30K miles.
I am impressed. That is a lot of great information, shared by someone who knows what he is talking about! Excellent article!
NickD
UltimaDork
12/11/20 6:49 a.m.
I still want a Challenger in the worst way. Dodge did a good job of tapping into the emotion aspect, rather than raw performance. I’ve sat in tons of Camaros and quite a few Mustangs, but none of them just gave me the same feel as sitting in a Challenger.
NickD said:
I still want a Challenger in the worst way. Dodge did a good job of tapping into the emotion aspect, rather than raw performance. I’ve sat in tons of Camaros and quite a few Mustangs, but none of them just gave me the same feel as sitting in a Challenger.
I LOVE the way they look. But can’t get past the weight.
And that’s disappointing about the tire size. A car with that much power and weight can only fit 275s without major surgery? You can stuff 265s under the unrolled fenders of a BRZ.
Not gonna lie, I still want a Challenger. BAD.
Is it large by huge and weighs a ton? Yes. But it’s a great GT car, and with some light mods, they will dance. One day, I will own one.
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