Cant get Nitrous control to work - What output is JS1

sprint · Post by **sprint** » Sat Jul 22, 2006 8:29 pm

I've been trying but I can't get the nitrous control to work. I built the circuit listed on the extra site and hooked everything up. MegaTune shows the "NOS/W Inj O" point go on but my relay doesnt energize. If I manually jumper +12 to my relay it does click in and not only do my solinoids fire but MegaTune shows "NOS/Tables" turn on. I took out and replaced the circuit (1k resistor and 2n2222 transistor) but the problem remains, it doesn't pull in the relay. After trying for a while I tried putting 12v to the resistor directly and it still doesn't pull the relay. Should the resistor be a lwer value? What is the output on JS1 supposed to be between active and not active. I checked JS1 with a multimeter but it jumps all over the place whether active or not. I also checked JS0 as a refrence and its at 1.4v constant when off. Is there something wrong with my JS1 output? Any way I can check the nitrous activation circuit?

-Allan.

Post by **jsmcortina** » Sun Jul 23, 2006 5:50 am

The 2n2222 is supplying a ground to the relay not 12v - so if jumpering 12v to the relay does something it suggests a wiring error. Also be sure to have the diode across the realy terminals.

James

sprint · Post by **sprint** » Sun Jul 23, 2006 5:55 am

jsmcortina wrote:The 2n2222 is supplying a ground to the relay not 12v - so if jumpering 12v to the relay does something it suggests a wiring error. Also be sure to have the diode across the realy terminals.

James

Now I'm really confused. I assumed from the diagram that the relay itself should be grounded like a normal relay, the +12 constant comes in from the top (in this case switched by your master arm) and a +12 switched coming from the 2n2222. At least thats how I read it ( http://megasquirt.sourceforge.net/extra/nitrous.html ). Thats NOT it? If not how should it be wired?

Does this mean my fluctuating JS1 output means the chips output is blown?

Post by **jsmcortina** » Sun Jul 23, 2006 6:14 am

First, ignore the "anti-lag" switch, that is not relevant for normal nitrous installs.

One side of the relay goes to +12v via the master switch, WOT switch and pressure switch (if fitted). The other side of the relay goes to ground via the 2n2222

James

sprint · Post by **sprint** » Sun Jul 23, 2006 5:19 pm

Ok....so the +12 is going to both the +12 constant AND the switched +12. That kinda makes sense.

Now since my output is bounching all over the place wether on or off does that mean I blew out that output and need a new CPU?

Post by **jsmcortina** » Mon Jul 24, 2006 1:50 am

sprint wrote:Ok....so the +12 is going to both the +12 constant AND the switched +12. That kinda makes sense.

Well not really.
Take a single fused +12v feed for your nitrous system that is only active when the ignition is on. Take it from your master relay.

Now since my output is bounching all over the place wether on or off does that mean I blew out that output and need a new CPU?

[/quote]
Possibly. It is unusual to damage the CPU, but if the output has been shorted to ground or 5v when the output was trying to do the opposite or if 12v was connected to it that will almost certainly damage it.

James

newtyres1 · Post by **newtyres1** » Mon Jul 24, 2006 2:43 am

sprint wrote:I assumed from the diagram that the relay itself should be grounded like a normal relay, the +12 constant comes in from the top (in this case switched by your master arm) and a +12 switched coming from the 2n2222.

Sprint,

The 2N2222 acts like a switch that connects one terminal of the relay coil to ground to turn the relay on, since the other end of the relay coil is connected to +12V (0Volts in the diagram = ground). The 2N2222 simply completes the circuit to ground to turn the relay on, it doesn't supply any power at all. There's 2 ways to turn on a relay, supply 12V to one end of the coil and switch the other end of the coil to ground, or have one end of the coil connected to ground and switch the other end of the coil to 12V. Same result.

Ian.

sprint · Post by **sprint** » Mon Jul 24, 2006 4:18 am

O.k....this makes sense now. I need a new CPU...mine output is definately fried. I'll get that and test again.

-Allan.

sprint · Post by **sprint** » Mon Jul 31, 2006 10:01 am

Got a new CPU and rewired the control box. Seems to be working just fine now. Thanks!

-Allan

sprint · Post by **sprint** » Thu Aug 03, 2006 9:19 am

Heres my updated schmatic if anyone is looking to wire one of these. Its based off the one listed on the extra page but I used a couple pilot relays and a voltage regulator to do the +5. This way you can wire this entire thing in a project box and have a harness plug into it. My current box has two harnesses, a inside the car and a out to the engine bay. If I were to do this again I'd have three (MS wires, engine bay, and inside). The +12 constant, ground, and solinoid wires should be 12 or 14 guage. I ground the solinoids to the block. The purge switch, leds, master arm, etc can all be 18 or 20ga since there is very little current on them with this design. If you use it LMK how it works:

Coils on a standard automotive relay are pins 85 and 86. Contacts are 30 and 87. I'd use 30 as the +12 and 87 as the output. The coils don't matter but I'd stay consistant with 85 on hot side and 86 on ground/negative.

-Allan