PART FOUR: FAILSAFE MONITORING SYSTEM

3. We’ve used the ST-12 before so we knew that we had a fuel distribution problem that resulted in the corner cylinders (numbers 1, 2, 7, and 8) running very lean, while the middle cylinders (numbers 3, 4, 5 and 6) were running very fat. After talking with the designer of the manifold and the guys who ported it, we settled on the idea that the manifold, exhaust, and camshaft combination was to blame. Rather than replace a bunch of expensive parts, we chose to use the direct-port nitrous system to correct the air/fuel ratio when the motor is at wide-open throttle and racing, which is when the air/fuel is most critical to us. As you can see from Innovate’s software, the corner cylinders are as much as three air/fuel ratios leaner than the middle cylinders. Our solution to our distribution problem was to richen the mixture in the corner cylinders via carburetor jetting changes and to lean out the middle cylinders using the nitrous system. This was accomplished by going bigger with the nitrous jets in the number 3, 4, 5, and 6 nozzles. What we learned through our testing was going up .002 in nitrous jet orifice size leaned the air/fuel ratio of the middle cylinders just under a half a ratio. We began the day with the middle cylinders nearly fouling the spark plugs with a low 10:1 air/fuel ratio. By the end of the test, we had staggered the fuel/nitrous jetting from .024/.026 to .024/.030, which brought the middle cylinders to a more reasonable 12:1 air/fuel ratio. At the same time, the power output of the engine increased dramatically, showing about a 20hp gain with each jet size increase. Going bigger with the nitrous jets while keeping the fuel jets the same resulted in leaner cylinders that made more power. Each time we went up .002 in nitrous jet size in those overly rich middle cylinders, the air/fuel ratio went down. We stuck with the two jet spread in the corner cylinders and ended our tuning session with a happy engine that made awesome, safe power.

Part Five: Spark Plug Detective Work
As cool as the ST-12 is to use, it's a pricy tool that not every dyno facility has at its disposal. That is why confirming what we saw on the computer with spark plug readings was so important. Reading spark plugs is an art with different ways of interpreting the colors and nuances of each plug. Our plugs indeed confirmed what the computer told us. Here are a few examples of spark plugs from cylinders running in various states of tune.

The Final Word
Since 2006, we've run this engine on pump gas and on race fuel as a guinea pig for dyno testing, and now we've added nitrous oxide to the mix for some real fun. Thanks to the expert advice from the guys at Nitrous Supply, Induction Solutions, Westech Performance, and a few savvy members of various Internet message boards, we were able to add almost 300 horsepower to the engine without making eight new ashtrays out of the pistons.

SOURCE
MSD IGNITIONS
El Paso
915-857-5200
www.msdignition.com
Moroso
80 Carter Drive
Guilford
CT  06437
203-453-6571
www.moroso.com
Lunati
662-892-1500
http://www.lunatipower.com/
Nitrous Oxide Systems
1801 Russellville Rd.
Bowling Green
KY  42101
800-465-5391
www.holley.com
Akerly and Childs
24907 Ave Tibbitts #A
Valencia
CA  91355
661-702-1999
www.akerlychilds.com
Nitrous Supply
15552 Producer Ln
Huntington Beach
CA  92649
714-373-1986
http://www.nitroussupply.com
Brodix
301 Maple P.O. Box 1347
Mena
AR  71953
479-394-1075
http://www.brodix.com
Paul Pfaff Racing Engines
5362 System Drive
Huntington Beach
CA  92649
714-894-7573
www.pfaffengines.com
Calico Coatings
6400 Denver Industrial Park Rd. P.O. Box 901
Denver
NC  28037
888-236-6079
http://www.calicocoatings.com
Pro-Filer Performance Products
New Carlisle
OH  45344
937-846-1333
www.profilerperformance.com
Cometic Gaskets
8090 Auburn Road
Concord
OH  44077
800-752-9850
http://www.cometic.com
Proform Parts (Specialty Auto Parts U.S.A.)
26708 Groesbeck Highway
Warren
MI  48089
586-774-2500
www.proformparts.com
Comp Cams
3406 Democrat Road
Memphis
TN  38118
800-999-0853
http://www.compcams.com
Quick Fuel Technology
129 Dishman Lane
Bowling Green
KY  42101
270-793-0900
http://www.quickfueltechnology.c
om
CP Pistons
1902 Mc Gaw
Irvine
CA  92614
949-567-9000
http://www.cppistons.com
Summit Racing
Akron
OH
800-230-3030
330-630-0240
http://www.summitracing.com/
Induction Solutions
Brooksville
FL  34604
815-341-8853
http://www.induction-solutions.c
om
Westech Performance
11098 Venture Drive
Unit C
Mira Loma
CA  91752
951-685-4767
http://www.westechperformance.co
m
Jesel Valvetrain Innovation
1985 Cedar Bridge Ave
Lakewood
NJ  08701
732-901-1800
www.jesel.com