Our project 2015 Dodge Challenger SRT HELLCAT, has been a labor of love for myself and some good friends over the past year and a half. I purchased the car, already modified with a 4.5-liter Whipple supercharged, 1,300cc injectors, dual fuel pumps, and other supporting modifications, to eventually turn the car into an absolute beast on the drag strip. We spent most of last year, chasing and fixing issues with the car while running substandard times at the strip.
After having most of the issues worked out and having the car re-tuned by Mike at OST Dyno, I was hopeful for a better year with the car. At the first track rental of the season, the car, still hot from driving it to the track, ripped a 9.82 sec. @ 143 mph pass, while spinning off the line, a new personal best.
I sent Mike a log of that run, and he sent me a new tune that he said would make the car even faster. Unfortunately, we didn’t get a chance to find out, as the supercharged sucked up a bolt and seized up during the burnout on the subsequent run.
Fast Forward To This Year –
Soon after, I got a billet 3.8-liter GEN V Whipple supercharger through one of my connections to replace the inefficient 4.5-liter unit. I had also previously ordered several parts to help the car get off the line better, such as a TCE 15-inch rear conversion kit, AAD control arms, cradle lockouts, a new set of Billet Specialities wheels, and other goodies.
Once everything arrived, a friend flew out to help me get everything done to the car in three days.
I then gave Mike at OST the arduous task of re-tuning the car and being among the first to tune one of these 3.8-liter Whipple superchargers. Since we didn’t know how much boost it would make and the car was still on the stock bottom end, we started with the largest pulley (4-inch) and then worked our way down to a 3.75-inch pulley. The car started out running 10.3 consistently, then a 10.0 and finally got back into the 9.8s, but it was evident that HELLCAT wasn’t leaving hard. There was a lot of work ahead to get the 60-foot times down.
Finally, Success –
This past month, I attended another private track rental armed with a new tune from Mike. It was immediately evident that the car got out of the hole much harder; however, it still ran a 9.8, with less mph than before. I sent Mike over a couple of logs, and even though he was working on a customer car, he quickly got me over another tune to try.
On the first pass with the new tune, the car went 9.76, a new personal best for me and the car. I tried to improve on that run but ended up having a few passes where the car, unfortunately, spun, resulting in slower times.
As the day was approaching, I was determined to get the car to run where I thought it would be, in the low 9-second range. It is important to remember that I was still on the 3.75 pulley, the second-to-largest one for that Whipple supercharger. Luckily, I had brought my 3.50 pulley to the track and had previously asked Mike about running it. He said he wanted to see a log with a short wide-open throttle (WOT) pull, and we would go from there. So, I figured I would throw the pulley on the car at the track and lift around the 330-foot mark.
That pulley must have put the Whipple in its efficiency range because it made a massive difference. The car left hard right out of the hole, lifting the wheels for the first time, and even though I intended to lift, it didn’t do anything weird or make any odd sounds, so I just stayed in it. At the end of the run, I was rewarded with a 9.42 sec pass @ over 147 mph. Forty minutes later, I backed that run up with a 9.47 @ almost 148 mph.
But, There Is A Catch –
Determined to improve that 9.42 pass, I went to the water box to make one last pass before the rental ended. I pulled into the box with a dead laptop without data logging. I spun the tires up through first and second gear and held the RPM in third gear. Then, all of a sudden, the car made an odd noise and immediately went into “limp mode.” I backed out of the water box with the car misfiring. I was sure, I had just cooked the motor. I popped the hood, and everything looked fine. I fired up the car again and heard no weird noises.
I drove the car back to my pit, and it seemed to run and drive fine, so I was hopeful that everything was alright. Unfortunately, that didn’t turn out to be the case. While driving the car home, it started to slip excessively while shifting and eventually locking itself in seventh gear while on the highway.
Unfortunately, the ZF 8-speed in the car is cooked, and while they are robust transmissions, this car has had a pretty rough life being used as a drag car. Another thing that kills these transmissions is poor transmission tuning, which the previous owner had installed when I purchased the car.
Now, the question is which route to go next with our project HELLCAT. Do I put a built 8-speed in it, or do I go all the way in that I initially thought and put a TH400 in it?
There are a lot of benefits to the TH400, but there are a lot of other parts that need to be changed to support the swap. The 8-speed would be plug-and-play, but there is no trans brake available for them, and it will likely hold me back when I get the car to the level I want to be at. I know one thing: I only want to buy the parts and do the work once.
Leave your comments below; I would love to hear your thoughts. Also, subscribe to MoparInsiders’ YouTube channel to get an early peek at our videos before they come out on the site, and follow our HELLCAT project car. Watch the video above, to see my reactions and how well the car ran firsthand.