1990 Chevy Suburban 454 TBI
Posted: Sun Feb 13, 2011 3:18 pm
This is my first Megasquirt project and although the learning curve was steep I am very satisfied with the results. My goal was to have a stock appearing CPU, but one that is easily tunable to work with planned future mechanical upgrades. Right now the Suburban is completely stock except for removal of the cat and an aftermarket muffler. The planned upgrades include headers, dual exhaust, aluminum heads, cam, and port fuel injection. I also want to replace the stock Turbo 400 with a 4L80E transmission.
The stock CPU is a “747” so I purchased another one for the case and connector socket.from the salvage yard along with the wiring harness and plugs. While I was there I also picked up an IAT sensor which the 747 doesn't use. From DIYAutotune I purchased the MSII with 3.00 board and a 747 adapter board. I assembled the two boards and the MS passed the tests with the JimStim. After installing the boards into the 747 case I used the GM wiring harness and plugs that I got from the salvage yard to interface with the JimStim since the db37 is inaccessible.
I made several modifications to my setup, the only change in the engine compartment was the addition of an IAT sensor in the air filter housing and routing the wires to the appropriate pins. After I changed the base resistor from 560K to 1K I used the darlington transistor on the 747 adapter board to control the electric kick-down on the Turbo 400, it's set to engage when TPS exceeds 75%. I copied that circuit in the proto area to control the SES light, the light goes off above 400 RPM.. Several jumpers were routed directly to unused pins on the 747 connector. These include the two CAN jumpers which will be used down the road to interface with a GPIO to control the 4L80E. Also, since the db9 connector will not fit in the 747 case without cutting a hole (and I wanted this to look completely stock) I routed the three wires needed for serial communications to the three pins used for the ALDL connector. I then made up an ALDL to db9 cable to hook up my laptop to my ALDL which is connected to the MS thru the stock wiring.
After several days of tuning the Suburban is running great, the butt dyno says it's making a bunch more power and is running smoother too. One nice thing with this setup is that if I have trouble with the the MS I can plug the stock 747 back in and be on my way. This won't work after I make the engine mods of course, but by then I'll have any potential bugs worked out. I've included some pictures of my setup and my latest msq.
nervala
The stock CPU is a “747” so I purchased another one for the case and connector socket.from the salvage yard along with the wiring harness and plugs. While I was there I also picked up an IAT sensor which the 747 doesn't use. From DIYAutotune I purchased the MSII with 3.00 board and a 747 adapter board. I assembled the two boards and the MS passed the tests with the JimStim. After installing the boards into the 747 case I used the GM wiring harness and plugs that I got from the salvage yard to interface with the JimStim since the db37 is inaccessible.
I made several modifications to my setup, the only change in the engine compartment was the addition of an IAT sensor in the air filter housing and routing the wires to the appropriate pins. After I changed the base resistor from 560K to 1K I used the darlington transistor on the 747 adapter board to control the electric kick-down on the Turbo 400, it's set to engage when TPS exceeds 75%. I copied that circuit in the proto area to control the SES light, the light goes off above 400 RPM.. Several jumpers were routed directly to unused pins on the 747 connector. These include the two CAN jumpers which will be used down the road to interface with a GPIO to control the 4L80E. Also, since the db9 connector will not fit in the 747 case without cutting a hole (and I wanted this to look completely stock) I routed the three wires needed for serial communications to the three pins used for the ALDL connector. I then made up an ALDL to db9 cable to hook up my laptop to my ALDL which is connected to the MS thru the stock wiring.
After several days of tuning the Suburban is running great, the butt dyno says it's making a bunch more power and is running smoother too. One nice thing with this setup is that if I have trouble with the the MS I can plug the stock 747 back in and be on my way. This won't work after I make the engine mods of course, but by then I'll have any potential bugs worked out. I've included some pictures of my setup and my latest msq.
nervala