Drag Week 2012 - Project GIRTST 71 Mustang (get it right the second time)

[TheSilverBuick]

A lot of systems default the temp sensor inputs to a certain temp when they read "-40 degrees" but not the megasquirt so far. Frankly I like it that way because it makes things easier to debug. And besides, I've never seen a temp sensor go bad except when it was smashed with a hammer so... it seems to work just fine.

I've had my shoddy wiring cause my air intake temp sensor to stop reading a couple times. Makes the engine hiccup for a second when the intake temperature goes from ~110*F to -40*F and richens up the fuel mixture a bit, then lean out to normal again when it got a signal. But because it was wiring being flaky, like a bulb hooked to a flaky wire it was causing a regular rapid hiccup. I plugged the laptop in, saw instantly the intake air temp swing wildly. I was ~150 miles from home, so I unplugged the IAT sensor and drove home with no more hiccups.

Car started having the same issue when I hose the engine bay off. The TPS goes nuts until it dries out (driving in the rain has been fine). I simply switched the accel enrichment to MAP and turned off the fuel cut off and ignore the TPS sensor altogether until I see the readings stabilize. It's only happened twice though, and I think it's related to my wiring. If I'm leaving town (~250+ miles) then I take my laptop with me anyways so it's not really that inconvient. I have and have seen people chase ignition and carb problems with a lot more difficulty than I've had troubleshooting weird behavior from my car.

One thing I hadn't thought about, if you're pulling the front wheels using the front VSS doesn't do you a whole lot of good for traction control. If you're into that sort of thing =P

[CDMBill]

THe wheel speeds can be used for functions if you like, such as Speed Based Boost Control. They can be used to detect which gear the trans is in, and used for other functions like Gear Based Boost Control. Front and rear VSS can be used as traction control if you like.

A lot of systems default the temp sensor inputs to a certain temp when they read "-40 degrees" but not the megasquirt so far. Frankly I like it that way because it makes things easier to debug. And besides, I've never seen a temp sensor go bad except when it was smashed with a hammer so... it seems to work just fine.

I thought we discussed this. Traction control isn't possible with this technology ;)

[CDMBill]

Back to the wheel speed sensor, does it cause any problems when you pull the front tires off the ground? or is it just part of the data log?

In the brief time my car is capable of a wheelie, a massive 6" to date, the front wheel wouldn't gain speed relative to the rear. Drag radials are intended to dead hook so I'll expect to see a rising rate VSS curve. A spinning drag radial will be pretty obvious as the VSS wil spike.

[dieselgeek]

I just wanted to know if wheel speed was an input in the code or was just a value that was being data logged.

With technology I would think you could reset the default mode so it does not run so rich when you unhook the MAT, ya know. ;-)

THe wheel speeds can be used for functions if you like, such as Speed Based Boost Control. They can be used to detect which gear the trans is in, and used for other functions like Gear Based Boost Control. Front and rear VSS can be used as traction control if you like.

A lot of systems default the temp sensor inputs to a certain temp when they read "-40 degrees" but not the megasquirt so far. Frankly I like it that way because it makes things easier to debug. And besides, I've never seen a temp sensor go bad except when it was smashed with a hammer so... it seems to work just fine.

[CDMBill]

Hey Bill,

Sorry to disrupt all the topics of coolness you have going on right now but I have a quick question going back to your power window install. I got the same kit and have a problem with it blowing the fuse as soon as I turn the car power back on. I even went down to minimum config with just one switch wired and it still happened. I pulled the motor leads off the switch for the driver door and it goes up and down fine with the battery off my drill so there's no short there.

Did you find anything hinky with the switches or wiring diagram? I wanted to just use two switches in the console but when I had problems initially I went ahead and wired all 3 in to make sure I didn't make bad assumptions on adapting their diagram.

BTW, I found out real quick how different our doors are when I went to install the motor assy's. I almost gave up twice before coming up with a workable mounting solution. I only have the middle 1/3 of the door behind a panel, the rest top and bottom is exposed metal.

Rich, look at the plugs from the front get the pin assignments correct. Also they have commons as well as the 12v+ and ground.

[Russell]

The MAT sensor attaches to the air cleaner base and needs more individual length so the air cleaner can be moved aside without disconnecting the MAT sensor. If you run the car with that sensor disconnected the default mode is -40* and it'll run rich as hell. Ask me how I know.

I just wanted to know if wheel speed was an input in the code or was just a value that was being data logged.

With technology I would think you could reset the default mode so it does not run so rich when you unhook the MAT, ya know. ;-)

[dieselgeek]

If he pulls the front tires, then it all breaks down and the car shuts itself off. Technology, ya know. ;-)

[Russell]

Back to the wheel speed sensor, does it cause any problems when you pull the front tires off the ground? or is it just part of the data log?

[dieselgeek]

That's what they said about the 747 center fuel tank before the crash of TWA flight 800, it only takes once to ruin your entire day.

that was a case of arcing/sparking wires in an empty fuel tank, supposedly, but it you talk to any 747 mechanics they will likely tell you it's a bunch of BS.

[Dignlif]

Hey Bill,

Sorry to disrupt all the topics of coolness you have going on right now but I have a quick question going back to your power window install. I got the same kit and have a problem with it blowing the fuse as soon as I turn the car power back on. I even went down to minimum config with just one switch wired and it still happened. I pulled the motor leads off the switch for the driver door and it goes up and down fine with the battery off my drill so there's no short there.

Did you find anything hinky with the switches or wiring diagram? I wanted to just use two switches in the console but when I had problems initially I went ahead and wired all 3 in to make sure I didn't make bad assumptions on adapting their diagram.

BTW, I found out real quick how different our doors are when I went to install the motor assy's. I almost gave up twice before coming up with a workable mounting solution. I only have the middle 1/3 of the door behind a panel, the rest top and bottom is exposed metal.

[CDMBill]

The large gate valve is fuel safe plastic, the other two are parts with fancy unobtainium seats, developed for IndyCar according to Fuelsafe, which is where I bought them.

I know I 'should' be using a custom fuel cell as there are no off the shelf units for my car, but they are particularly spendy and I have a budget to stay within this year.

I like the fuel cell foam idea and may give that a shot if I can figure out how much access I need for getting it in and if necessary, out.

[SuperBuickGuy]

Hot things in gas tanks don't seem to be an issue....since there is no air.... I've taken out a couple melted electric in tank pumps.

That's what they said about the 747 center fuel tank before the crash of TWA flight 800, it only takes once to ruin your entire day.

[squirrel]

personally I would be a bit worried of metal clapping into metal inside a tank (with doors) as one spark would make for a hot day.

Hot things in gas tanks don't seem to be an issue....since there is no air.... I've taken out a couple melted electric in tank pumps.

[SuperBuickGuy]

Fill the tank with fuel cell material, but cut the center out where the pump is located (like 12"x12"). No slosh, plus no boom if it gets hit

personally I would be a bit worried of metal clapping into metal inside a tank (with doors) as one spark would make for a hot day.

[BBR]

Nothing to add except, FIVE GALLON SUMP! That thing looks huge.