Next project (besides Meth inject w/ a timing bump from hemifever and a trans temp gauge) is a launch RPM indicator similar to what pro stock uses- an LED is on until you hit your target RPM, then it turns off, and if you go above another RPM, it flashes.

IE my convertor stalls around 1600, and I go red if I leave on bottom bulb turning on, but if I wait for it to be ON, I'm about 100 late. So I need to lower my launch about 150 RPM. It's hard to look at the tach, staging beams, and tree all at the same time. So if I can have an LED telling me if I'm where I need to be, and tape my windshield so I know when I'm lined up with the beams according to a reference point (top of the tree), then I can focus on bumping into the beams and getting to my launch RPM.

The only other thing I can think of to slowing down my RT is add a second return spring, or pull 5 pounds of air from the front tires and see where that puts me.

I'm going to try the return spring (on the pedal side so I don't break the cable) and air pressure and see how close that can get me. With the cooler air now, I should have a faster reaction time, then I can compensate for the summer heat once I'm in the ballpark. But having the LED digital tach would be a big help.

 

Does anybody know if there is an exposed tach wire anywhere? If not, what is best way to tap the coil wire, other than a trailer tap? Does the connector come apart at all?

I pierced it with a DMM probe and hooked up, tach script worked perfect (38hz = 760 RPM). I put everything in an enclosure tonight, just need to order the brain for it and put the program on it. Then the hard part, running the wire to wherever I can pick up a tach signal.

Also, is there an un-used ignition-on power tap/pigtail in the dash anywhere other than the radio for a 2WD? Like for the 4WD controller or anything? That way this thing isn't killing the battery.

I'm going to set it up like an open wheel tach, but in a narrow range. I'm going to see what my convertor stalls at right now, set that as the high point, and go down 50 RPM per bar (500 rpm total). That should be tight enough resolution to make for consistent launching.

20121113_232904.jpg

20121114_231010.jpg

 

alright, I tapped the coil. Wasn't fun (much less from 11pm-2am in 37 degree weather) but it looks OE for the most part. I tried soldering directly to the pin, that didn't work (the housing is an exact fit & the solder wouldn't stick to the pin), so I slit the insulation and soldered a loop around the wire, and heatshrunk the whole thing. I had to cut the orange seal ring off.

The green/black rubber seal can stay in place, but you need to pull the white insert under the pins.

With the insert removed, you can stick a small straightblade into the connector, push down on the retainer clip, and the pin comes out the back.

20121115_003200.jpg

20121115_003258.jpg

20121115_003340.jpg

 

Also, I went poking for any open ignition-on fuses. My dash-side fuse block has several openings, but I didn't grab my DMM so see if any had switched power. Do they make fuse taps for the sub-mini fuses? Hoping I can tap an OE location rather than the blue switch wire....

 

I need to go see what fuses I don't have, but this is a step in the right direction. Pages 8W-12 -3 and -4 (648 and 649 in PDF)

dakoFuseBlockFSM.png

dakoFuseBlockFSM2.png

Looks like the transfer case selector falls under fuse 11 (I have TC wires hanging under the chassis, what's the chance there's a pigtail behind the dash?)

Cigar lighter is on fuse 17 dedicated (my ashtray is broke, I'm repurposing that cavity for the ultragauge more than likely, so I can steal that power source)

Convertor stalls at 1550 on the gauge, so I'm going to set it to do the following, on 60rpm steps:

900 = 45hz
960 = 48hz
1020 = 51hz
1080 = 54hz
1140 = 57hz
1200 = 60hz
1260 = 63hz
1320 = 66hz
1380 = 69hz
1440 = 72hz
1500 = 75hz

if (rpm > 900){
digitalWrite(seg1,HIGH);
} else {
digitalWrite(seg1,LOW);
}

if (rpm > 960 ){
digitalWrite(seg2,HIGH);
} else {
digitalWrite(seg2,LOW);
}

if (rpm > 1020 ){
digitalWrite(seg3,HIGH);
} else {
digitalWrite(seg3,LOW);
}

if (rpm > 1080 ){
digitalWrite(seg4,HIGH);
} else {
digitalWrite(seg4,LOW);
}

if (rpm > 1140 ){
digitalWrite(seg5,HIGH);
} else {
digitalWrite(seg5,LOW);
}

if (rpm > 1200 ){
digitalWrite(seg6,HIGH);
} else {
digitalWrite(seg6,LOW);
}

if (rpm > 1260 ){
digitalWrite(seg7,HIGH);
} else {
digitalWrite(seg7,LOW);
}

if (rpm > 1320 ){
digitalWrite(seg8,HIGH);
} else {
digitalWrite(seg8,LOW);
}

if (rpm > 1380 ){
digitalWrite(seg9,HIGH);
} else {
digitalWrite(seg9,LOW);
}

if (rpm > 1440 ){
digitalWrite(seg10,HIGH);
} else {
digitalWrite(seg10,LOW);
}

 

okay, so I'm getting all kinds of funky numbers. Apparently there's alot of EMI running around under my hood...

off the coil's negative post (where I tapped), I get a signal of roughly 250hz.

If I wrap the checker wire around the coil wire, same.

If I wrap it around a plug wire (I've been using #2 since it has easy access), I get ~20 hz at idle. But it got way off after 1500RPM.

I wrapped it around the injector wire, same deal- accurate at idle, off up high.

Is there something going on that I can't see?

In the meantime, I'm going to run off the TPS voltage, and light up each bar at 1/10 of a volt. not as accurate as RPM, but will get the job done.

The coil fires 3 times per rotation, so RPM should be frequency times 20. (fires per second * 60 seconds / 3 fires per rotation)

The plug fires 1 time per 2 rotations, so RPM should be frequency times 120. (fires per second * 60 seconds / 1/2 fire per rotation)

600 RPM = 10 rot/sec = 30 coil hz = 5 plug hz