So, not much to say but I’ll say it anyways, here is my synopsis of the 2013 Super Coupe Shootout along with the inconclusive results of the Mammoth MPX-S M90 venture. Dave had sent me a Base tune that was working well, and was good enough to idle and get AFR close enough. Before the event I chased down the vibrations one more time, this time I jacked up the car and took off the wheels. It became clear that the vibrations were a combination of driveshaft and differential. I clocked it again into various combinations and used hose clamps to add weights to the shaft hoping it would change the frequency. It was a failed attempt and after 3 hours I decided to give up. I also tore apart the supercharger to replace the spring loaded coupler with a solid one hoping this would get rid of the worrisome rattle, after inspecting the coated rotors and finding no issues I slapped it all back and the noises seem to have gone away for the most part, it was no longer this annoying rattle that pierced the cabin. Things were looking good, all that I needed was the radio to be put back, and after some time of chasing a loose speaker wire that causes noise in the speakers and sometimes cuts out the sound. My shootout adventure started Thursday night things seemed to go well car drove and behaved well. Friday I decided to romp on it in the mountains of KY. I looked at the boost gauge and its behavior. Oddly boost started at 16sh and settled at 18psi but after 5500 rpms the boost started to creep up and peg the 20lbs auto meter gauge.
I thought it was belt slip, but I arrived at the shootout and did not notice any belt dust, after a conversation with DD he suggested the bypass might be opening up at high boost. I changed the reference of the bypass from before the SC to after the SC and while the supercharger started to make odd noises during transition I did it to ensure the boost would keep the valve closed. Chris and I went for a few runs to dial in the Maf curve, it only needed a few tweaks it was pretty close already. I also wanted to turn on the alky at this point and wanted to make sure the car ran well. Car ran strong and made all the right noises, although the boost creeping was still present. I decided to leave it alone till the dyno. Dyno day we started at 21 deg of timing for the first run, 24 for the second and 26 for the third. Dyno didn’t impress me much, but looking at other variables I say it not that bad. But it was clear the car was lacking the torque that an overdrive M90 is supposed to have. Most of the M90 competition was over 400lbs of torque and while my torque curve was pretty flat I had little to no cylinder pressure, this set up is overdriven to 25% so there should be some serious torque being produced. HP didn’t really disappoint, although we always want more. To put it in perspective I was about 40HP short of top secret set up put together by the Dalke family, top secret large cam (with solid lifters?) vs. my little 218/218 cam. .580 lift cam. You also had David Clarks set up he had a similar set up as mine and he was running on race fuel and his OD was 30ish% and his number were about 20hp higher than mine, I don’t know his cam specs. Anyways track numbers were as expected most cars were running about .4-.5 sec slower from their best time. Surprisingly although my car was low 13s there were was a 108mph run and that was similar to my 12 second run that happened at my local track at near sea level and cold 50 deg weather. The car felt strong and sounded great, no hiccups on every pass down the track. I shifted to 5500 rpms most of the time because after that my car goes lean 12.1 when I bury it to 6000rpms. And as a testament that HP might not be everything, I had fund driving to and from the shootout and although I blew out the second gear syncro on my last past. The car did its job and brought me home a second place trophy, against a very seasoned 5spd driver.
To summarize- In my opinion, based on the data, discussions and my own experience. I will say that the modified port timing on the MPX was not ideal for the RPM range of my engine. The blower does move a lot of air up top, enough to put my 60lbs injectors at near maximum putting a stain on my fuel delivery capacity. But it seems the blower is not efficient enough at the lower range of the rpm spectrum. This MPX was used on my M112 hybrid and it too suffered from the same torque loss. I will go back to a non ported MPX and overdrive the blower 5% more, the inlet will assist in delivering the necessary air at those blower speeds. I will also need to install a 340lph fuel pump to take care of the fuel starvation issues at above 5500 rpms. If my tranny didn’t give up the ghost I would have ran the car here back home on a cool air and I bet it would have improved dramatically over my best times. But we won’t know as the car will be on jack stands till I drop in some blockers. I'm also not interested in using the ported mpx any further, this engine cannot use the air the set up is capable of. I venture to say that if my cam and valve train could rev to 7000rpms this combo could provide the air to keep making HP. Since I’m not interested in changing displacement or changing cams and valvetrain. The kit will prove inconclusive. I will just say I have the loudest and baddest sounding M90 in the club. Cheers.
Thoughts & Comments welcomed.