[Third] Moving Day + Dyno - 05/02/2016

After wrapping on the audio install in 2015, the car was pretty much 100% assembled leaving me to enjoy it and work out the bugs. However, free time is a vacuum so I decided it was high time I move again (Ugh...). It did afford a nice shot from my new front yard though :)

Going back to the enjoying and working out the car's bugs.

After my move I finally accepted the fact that I was going to need professional help to tune my car. Enter Carma Performance and my dyno day:

Carma Performance in Nashville, TN turned out to be a one man operation run by Erin Carpenter. His shop had all kinds of cool cars waiting in line and he was extremely knowledgeable and proved it multiple times during the visit. After talking with me for 30 minutes about the car's build info we loaded it on the rollers. He got started and my car started backfiring like it likes to do. He kept shaking his head and saying "there's no way." He eventually killed the car and we talked some more. He said he was 99% sure the car was misfiring but it wasn't being reported to the PCM. After I let him know the injectors probably weren't the place to look since I've had them cleaned and flow tested we discussed the coils. This was an area I felt had more potential for problems since the coils are low mileage but used and I didn't have a full history on them. Turns out we didn't even get to the coils. With the car on and dyno locked at 30MPH I held the accelerator where the "misfiring" was most active. This caused the engine to really shake around as if 2 cylinders were gone. From there Erin simply unplugged each coil until he came to one coil that hardly made a difference when unplugged. Eureka! However, the problem turned out to be plugs wires on cylinders 4 and 6. After throwing a pair of spares on, a noticeable difference was made and  and Erin was able to finish up the MAP and MAF tuning. Took about 2 hours Goodbye backfires.

Finally we got to spark tuning and WOT tuning. Erin dialed both tables in after about 8 partial pulls and 2 full pulls but when we got ready to do the last full pulls and record the pull data we were disappointed to have the Dyno start slipping. Erin fessed up and said the much higher HP car he was dyno'ing last night had similar issues on the dyno and he's afraid his dyno is officially in need of repair. The problems were causing it to slip around ~340HP so that's about all the graph would show before it would dive when it started to slip. He told me in his experience the log data supports just over 400HP to the wheels. Later he confirmed when he extrapolated the duty cycle of the injectors at ~6500RPM

((49 lb/hr * 0.63 duty cycle) / 0.5 BSFC)* 8 cylinders = 494 Flywheel HP * 0.85 drivetrain loss = 420WHP

It's about what I was hoping for although I was a little disappointed I couldn't get a sheet to brag on

Finished up by taking a wild test drive which was hilariously fun while Erin made some final corrections. He then took the wheel and showed off his knowledge of downtown Nashville

Drive home was nice. No backfires, silky smooth acceleration, and cooold AC. I did kill the engine a couple of times when clutching in to coast to a stop with AC on. I think Erin didn't tune for idle when the AC compressor is on. I let him know and we're going to potentially setup a remote touchup. I did get a little homework though. On the test drive Erin mentioned that he still felt and heard a potential misfire. I couldn't really detect it on the test drive, but think I noticed it on the drive home. I could feel what felt like mini fuel cuts when cruising at very low load and rpm. It just enough to let you know it happened then the power comes right back all within a fraction of a second. The result is a not so smooth cruse as it feels like the car is lightly surging rather than being continuous. So I think I have one more bad wire. I ordered new wires and plugs and hope to finish changing them when my replacement battery lead shows up.

On the next set I've got to make sure nothing touches the headers. I've got to keep them centered between without contact and they should survive.

Finding the source of the misfires was worth the trip. Such a small thing caused me so much grief and has had me chasing my tail for years now.