Lil Grizz
09-01-2002, 03:46 PM
From the Lake Lanier Skunk Works:
Well its out, I supercharged my 22zx. I was trying to keep it quiet for Eufala but word spread pretty quickly. I was asked two questions upon my arrivial; "You guys sure got up early didnt you?" and "Hows that Whipple?" Well yes I did get up really early about 4a.m. and the Whipple is just fine:).
Heres the scoop. The engine is a 1999 7.4 MPI rated at 310 php. No mods at all before the install save for rex marine exaust tips and a little trimming of the throttle body gasket. On its best day I could run 62GPS @ 4600Rpm turning a 24p bravo 1. The 310 7.4 is supposoedly limited to 4600 so I intend to never exceed that. Right before I started wrenching I baselined the boat at 59.4GPS. With less than half tank and a zillion tries that was the best speed for the day. The water was glass and it was at least 94 degrees and im sure that worked to my disadvantage.
The install was easier than you would think. All I had to do was take off the intake manifold, put on the charger, plumb a line into the sea pump, modify my fuel pressure regulator, and reroute the throttle cable. The only glitch was an ECU programming mishap that delayed starting the engine for a few weeks. The ECU is still not dialed in and its running really rich under 3000rpm and somewhat rich above. Better rich than lean so until the season is over I wont mess with it. It took me about 8 hours of work to install and that is including the head swap. Yea I swapped the heads, but not for a better performing set. The L-29 fast burn heads that come on the 7.4 sometimes detonate when under boost due to their chamber design. Didn't want to find out if I would actually have that problem. I swapped on a set from a gen V 7.4 for 2 reasons, 1)They are near identical in airflow and compression(even though their intake ports are smaller) and 2) they were FREE(and had a complete valvetrain overhaul at that)!
Now for the performance:
First day out with a 28p hydromotive 4-blade went 74.3@4500 GPS. When the ECU was reprogrammed the rev-limiter was removed for some reason so I held back to save the engine, it still had more to go before it was WOT. I spent a few weeks prop testing and settled on a box stock 30p bravo 1. With that prop I get about 77.x@4500 gps. I can hit that speed every time we test, very consistant 18mph gain.
This weekend at Eufala the boat must have been showing off for "The Big Three" since it was holding steady at 79mph, AMAZING! I danced a jig on the backseat. Would have loved to see an honest 80 but just didnt happen, maybe when its tuned better. It is a very good looking kit, Heres my engine. http://www.donzi.net/photos/MyBoatEngine.jpg http://www.donzi.net/photos/MyBoatEngine2.jpg http://www.donzi.net/photos/MyBoatEngine3.jpg
Well its out, I supercharged my 22zx. I was trying to keep it quiet for Eufala but word spread pretty quickly. I was asked two questions upon my arrivial; "You guys sure got up early didnt you?" and "Hows that Whipple?" Well yes I did get up really early about 4a.m. and the Whipple is just fine:).
Heres the scoop. The engine is a 1999 7.4 MPI rated at 310 php. No mods at all before the install save for rex marine exaust tips and a little trimming of the throttle body gasket. On its best day I could run 62GPS @ 4600Rpm turning a 24p bravo 1. The 310 7.4 is supposoedly limited to 4600 so I intend to never exceed that. Right before I started wrenching I baselined the boat at 59.4GPS. With less than half tank and a zillion tries that was the best speed for the day. The water was glass and it was at least 94 degrees and im sure that worked to my disadvantage.
The install was easier than you would think. All I had to do was take off the intake manifold, put on the charger, plumb a line into the sea pump, modify my fuel pressure regulator, and reroute the throttle cable. The only glitch was an ECU programming mishap that delayed starting the engine for a few weeks. The ECU is still not dialed in and its running really rich under 3000rpm and somewhat rich above. Better rich than lean so until the season is over I wont mess with it. It took me about 8 hours of work to install and that is including the head swap. Yea I swapped the heads, but not for a better performing set. The L-29 fast burn heads that come on the 7.4 sometimes detonate when under boost due to their chamber design. Didn't want to find out if I would actually have that problem. I swapped on a set from a gen V 7.4 for 2 reasons, 1)They are near identical in airflow and compression(even though their intake ports are smaller) and 2) they were FREE(and had a complete valvetrain overhaul at that)!
Now for the performance:
First day out with a 28p hydromotive 4-blade went 74.3@4500 GPS. When the ECU was reprogrammed the rev-limiter was removed for some reason so I held back to save the engine, it still had more to go before it was WOT. I spent a few weeks prop testing and settled on a box stock 30p bravo 1. With that prop I get about 77.x@4500 gps. I can hit that speed every time we test, very consistant 18mph gain.
This weekend at Eufala the boat must have been showing off for "The Big Three" since it was holding steady at 79mph, AMAZING! I danced a jig on the backseat. Would have loved to see an honest 80 but just didnt happen, maybe when its tuned better. It is a very good looking kit, Heres my engine. http://www.donzi.net/photos/MyBoatEngine.jpg http://www.donzi.net/photos/MyBoatEngine2.jpg http://www.donzi.net/photos/MyBoatEngine3.jpg