Final update: First test run with correct setup and I'm really excited. Didn't feal that I got more power, but the overall driveability!!!! The idle transition was smoother making the drivetrain feal stiffer, I could floor the gass pedal much faster without any engine hesitation and it feelt like it had much more torque in the low end. Highly recommended upgrade.
I fitted an HPV-1 when I first got my 78 GTS. After sorting a tach issue with an MSD amplifier box, all worked well. Years later, the pickup loosened up and was damaged by the toothed wheel. I wound up replacing the pickup and at the same time, upgraded the HPV-1 with an XDI-2 for more timing flexibility. This is a rock solid ignition system. I also installed an XDI-2 on my high performance Lotus Elan twin cam. The engine builder initially installed the trigger wheel on the trailing edge of 11th, leading tooth. Initial runs produced 165 bhp, a bit disappointing. Investigating further, it was discovered that we should have set it to the trailing edge of the 11th trailing tooth. After correction, we got 193 bhp and 165 lb ft of torque from 1.9 liters. This engine was built and tuned Marcovicci-Wenz Engineering on LI, NY and just goes to show even the best of engine builders sometimes make mistakes. Bill
"This engine was built and tuned Marcovicci-Wenz Engineering on LI, NY and just goes to show even the best of engine builders sometimes make mistakes. " Well, IMO such a mistake should have never gotten out of the shop. I agree that anyone CAN make a mistake but such an error creates an obviously poor running engine and no good shop would have ever let it out without troubleshooting/finding/correcting the error they made.
Hi Guys. The timing error was found at the shop after the first start and initial dyno pulls to seat the rings. There was no pinging, overheating, low oil pressure (special Titan dry sump), or other signs of distress during the first session, only less than expected output ( I was shooting for 180+ bhp) and reluctant starting. Total running at the end of the day was maybe 20-30 minutes. We immediately suspected timing and changed it a couple of times via xdi-2 ignition mapping and were surprised output went up a bit when retarded about 4 degrees. The two timing lights we tried were dead, so we called it a day. I came back a week later for the next dyno session, by which time they had discovered the error and rectified it. Startup was immediate and after a warm up and the setting of overall timing to 34 degress BTDC, with a good light, we proceeded to complete the break-in with short duration pulls to 7.5 krpm. We also tested timing sensitivity by checking output at 32 and 36 degrees BTDC. I think we ended up at 32 degrees on pump gas. The engine was built with all new parts, an early Steve Jennings aluminum block (OEM block is cast iron-we did have to seal and weld on a bung for the external oil gallery feed line to accommodate the large bore 26R headers) with steel sleeves, Kiddie steel crank (slight increase in stroke from 72.7 to 77.6 mm), Carrillo wide journal steel rods, and custom forged pistons of 89 mm (82.5 mm is OEM) diameter. The bottom end is rated to better than 10 krpm, but the valve train is limited to about 9 krpm, using modest street cams and special spring packs. Better cams are a future possibility. CR is about 10.5:1. Timing is set to: 14 BDC up to 1.2 krpm, increases to 32 at 3.5 krpm, flat to 8 krm, and decreases to 20 at 9 krpm. This is a straw man curve and will likely be adjusted based upon road experience. The xdi-2 timing curve is set to start reducing timing at 8 krpm so this is the effective rev limit. OEM red line is 6.7 krpm with a cast crank, so a useful increase was demonstrated. Power output levels off at 190 bhp at 7 krpm with a torque curve peak at about 5.3 krpm. This is intended to be an every day street engine, but with Lotus 26R race car output. I expect overall weight to come in under 1400 lbs (light weight body but full road gear-OEM is about 1500 lbs ready to go), so pretty good power to weight ratio. For reference, good race 26R's produce about 200 bhp from 1.6 liters and Jay Leno's 26R street clone is reported to produce better than 230 bhp from 2.2 liters. I selected Marcovicci-Wenz Engineering based upon recommendations by racers. Peter Marcovicci has a reputation of building very reliable race engines and my limited experience to date, supports this claim. I would not hesitate to go to him again as I find Peter and his small crew to be talented, knowledgeable, and honest. Yes there was a problem, but he diagnosed and fixed it. No obvious harm was done. This engine is relatively powerful, leak free, and looks great IMHO. It's also 40 lbs lighter than the cast iron block. Bill
