In order to tell you a little about my experiences with Megasquirt, I´m presenting this story from 2004-2005. I am the owner of a 1970 Road Runner since 25 years, and it has gone through a lot of tuning, messing and engine-altering situations! About 12 years ago I purchased Holleys "Projection4" TBI fuel injection, and has kept it since then, not because of happy satisfaction, but from just being to lazy to change back to carbs again. It had no O2 sensor, no computer hookup and thus no feedback except for reading plugs and "driving feeling".
I was probably not driving around with the engine lean or optimized, all I could do was to make sure that the plugs stayed away from white.
About a year ago I found the Megasquirt site, and begun to dig down. I read all i could find, downloaded and printed the manuals, and ordered stuff from DigiKey. Slowly the idea of an homebuilt and completely configurable FI control box became reality. I purchased sensors, crimped cables and installed stuff! My plan was to retain the throttle body from the Holley setup, and connect Megasquirt to this guy.
The important day came closer and closer! How should everytyhing work? Then, one day in May...
This day was both good and bad. I managed to run my Plymouth Roadrunner on Megasquirt for the first time = Good!
But I also managed to fry my Megasquirt box = Bad!
What happened? Well, after all the installation proceedings, I was finally ready to run my setup, and it started up more or less right away. Very rough idle, but great accelerator reaction. I let it sit and "idle" holding the rev´s at 1200 rpm, until it warmed up completely. During this time my laptop was connected, and the only failing stuff that I noticed was the narrow band O2 sensor not reacting. It is a heated unit, but probably not getting the correct voltage. At the end of the session I saw some very low voltage readings, probably because the sensor was slowly heating up from exhaust gases.
Anyway, after shutting off and starting up a few times, I decided that I had a problem with my idle that would not solve itself, so I begun playing with different VE settings around idle, but my MAP stayed at 50-60 all the time. Then I got a bright idea that something in my constants was off, and I thought that having simultaneous squirting would improve the idle compared to alternating. So I switched this setting with the engine running, and uploaded.
The engine died.
Well, I imagined that it was just a reset, and tried to start again and again, but no success here. Then I realized that my injectors were spraying huge amounts of gas into the Holley TBI (900 cfm), and halted all action immediately. I screened all info on my laptop, and it showed that as soon as the ignition was turned on, my rpm hit exactly 3000.
Uh-oh, Houston We have a problem...
Disconnecting my box, and reviewing the inside reveals a nasty burnt smell, and all suspicious that I can see is a hairline crack on the FET driver U7. It seems that I fried this component by attempting to change the "squirt-mode" on the fly. I am using the Fly-Back modification, and the PWM values has been set accordingly, so I think that my preparations were correct, I just got a bad idea.
Anybody who has comments to this or any good suggestions to share? I am not sure if it will be enough to just change U7, but since the other components looks OK, I think that they are fine.
Bottom line is still: MY MEGASQUIRTED MOPAR STARTED UP !!! YEEHAWW!!!!!
Leif Jansson: 1970 Plymouth Road Runner convertible + 440ci
Leif Jansson: 1970 Plymouth Road Runner convertible + 440ci
"Do it right the first time"
Re: Leif Jansson: 1970 Plymouth Road Runner convertible + 440ci
how did you get your tach signal