The MoparInsiders Project 2015 Hellcat has been a labor of love by myself and some good friends over the past year and a half. I purchased this 2015 Dodge Challenger Hellcat, already modified with a 4.5 liter Whipple Supercharger, 1300cc injectors, dual fuel pumps, and other supporting modifications. With the goal of eventually turning this 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 drag strip.

Fast Forward To This Year

After having most of the issues worked out and having the car retuned by Mike at OST Dyno, I was hopeful for a better year with the car. At the first track rental of the season, with the car still hot from driving it to the track, it ripped off a 9.82 at 143 MPH spinning off the line, a new PB. 

I had sent Mike a log of that run, and he sent me a tune that said would make the car go even faster. Unfortunately, we didn’t find out, as the supercharger sucked up a bolt and seized up during the burnout on the subsequent run. 

Through one of my connections, I got a billet Whipple 3.8-liter Gen 5 supercharger on the way to replace the old and inefficient 4.5-liter unit. I had also previously ordered many parts to help get the car off the line better, such as a TCE 15-inch rear conversion kit, AAD control arms, cradle lockouts, new Billet Specialties wheels, and more. 

Once everything arrived, a friend flew out to help me get everything done on the car in a 3-day thrash. 

That then gave Mike at OST the arduous task of retuning the car and being one of the first to tune one of these 3.8 Whipples. 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 down to the 3.75-inch pulley. The car started out running 10.3s, then 10.0, then finally got back into the 9.8s, but it was evident that the car wasn’t leaving hard. There was much work to do to get the 60-foot times down. 

Finally!

In late September, I attended another private rental, armed with a new tune from Mike. It was immediately evident that the car got out of the hole much harder but still ran in the 9.80 range, with less MPH than before. I sent 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 PB 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 a slower time. 

The clock was ticking down on the track rental, and I was determined to get the car to run where I thought it should be (low 9-second range). Remember, I was still on the 3.75 pulley, the second-to-largest one for that Whipple supercharger. I 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 WOT pull, and we would go from there. 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 supercharger in its efficiency range because it made a huge difference. The car left hard out of the hole, wheels up for the first time, and even though I intended to lift, it didn’t do anything weird or make odd sounds, so I just stayed in it. At the end of the run, I was rewarded with a 9.42 at over 147 MPH. Forty minutes later, I backed that run up with a 9.47 at almost 148 MPH.

Here’s The Catch…

Determined to improve on that 9.42, I went up to make one last pass right before the rental was to shut down. I pulled into the water box with a dead laptop without data logging. I spun the tires up through first and second gear and held RPM in third. 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. Sure I had just cooked the motor. I popped the hood, and everything looked good. I fired the car up again and didn’t hear any weird noises. 

I drove the car over to my pit, and it ran and drove fine, so I was hopeful that everything was okay. Unfortunately, that turned out not to be the case. While driving the car home, it started to slip excessively badly on gear shifts, eventually locking itself into 7th 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 trans tuning, which it had a bad trans tune from the previous owner. 

Now I need to decide which route I will go with the car. Do I put a built 8-speed in it, or do I go the way 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 it. The 8-speed is plug-and-play, but there is no trans brake available to them, and it will likely hold me back when I get the car to the level I want it to be at. I know one thing: I only want to buy the parts and do the work once. 

Check out the video above to see how our whole day went at the track rental, and let us know what you think we should do with the car in the comments below.