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Not sure if this is the correct forum but feel this will get more attention here.
I am using a solid state relay (SSR) with MS3X for alky injection control. I am pulsing the neg side of the alky pump and have the SSR wired as follows. 1 to a good ground, 2 to the alky pump neg terminal, 3 to the MS PWM and 4 to sw12v. In MS test mode, it works as desired with different PWs and I used it yesterday for the 1st at the track and it appears to have worked as the IATs dropped considerably and the tank level was down.
Now for the problem I am having. I have 2 FP relays next to the SSR and from the SW12V wire that goes to the alky pump + terminal, I have a tee that branches out to the 86 terminals of the 2 FP relays and the SSR 4. Refer to wiring diagram. Prior to yesterday, with the alky OFF, the engine ran flawlessly. However, yesterday with the alky ON, the power felt off and in the datalog, the FP readout looked like an oscilloscope on steroids, fluctuating from 62 to as low as 40 at 19psi boost. From what I can deduce, the problem seems related to the SSR because it starts at about 13-14psi boost and I have the Water Injection control enabling at >70% / 3800 RPMs / >169kPa. Had wheel spin soon after the launch and had to pedal it and between the time I got out of the throttle and the boost coming back up, the FP readout went back to normal then back to crazy for the rest of the pass when the boost came back up and then back to normal at the end of the pass.
Only thing I can come up with is that the sw12v that connects to the SSR 4 has feedback that is possibly also pulsing the FP relays. Just my own theory but would appreciate any feedback.
I end up with some super weird grounding loops or something when I ran the ground for my alky pump and the ground for 2nd fuel pump relay through a hobbs. My 2nd fuel pump relay would run full time instead of just priming with key on and then it would stop working when the hobbs switch turned on the meth pump.
And you will likely need a flyback diode across the alky pump too.
Thanks! Have a couple of questions.
- Will a 1/4-watt resistor work for the SSR?
- I am assuming the diode goes between the alky pump + and - wires. Does it matter where I put it (close or farther away from the pump)? Does it matter which direction the diode is position? Do you have a specific diode recommendation?
I dont think the resistor needs to be a high rating at all. And not honestly sure what it's function is, but I've seen a few places say it is needed.
Diode would be across +/- terminals of the pump, and AFAIK yes closer to the pump the better.
Diode is to allow flyback current to free blow back around the pump circuit so it would be in the direction neg to pos. ie.
As for type, I see many mention 1N4007, although I really dont know a lot about them.
I did use a diode on mine, but damned if I can recall what part number. I had issues and blew up my SSR and thought it was diode related, but turned out when I heat shrinked the diode/wiring the insulation had melted and the leg of the diode shorted on the wide.
I did buy both of the above, but damned if I can remember which one I actually used and it's all heat shrinked up so cant even check. I've just been running it with the SSR as off/on though, as other issues prevented me PWM'ing things because of how I'd wired my turbo oil scavenge pump.
But I'm switching to in-tank pumps now, and will re-arrange wiring so I can PWM these without it affecting the scavenge pump. It'll probably be a week or two though before I have that finished.
^That resistor is limiting the overall current in the circuit if its implemented how that pic is drawing. Assuming the L is your pump, its also limiting the power to the pump, which seems odd. I would have expected to see the resistor in series with the diode and not in series with the parallel L/D.
^That resistor is limiting the overall current in the circuit if its implemented how that pic is drawing. Assuming the L is your pump, its also limiting the power to the pump, which seems odd. I would have expected to see the resistor in series with the diode and not in series with the parallel L/D.
I think I seen some mention the resistor can also offer protection to the ecu in the event of a problem with the SSR.
Resistor across the control side will in no way affect power to the load.
I think I seen some mention the resistor can also offer protection to the ecu in the event of a problem with the SSR.
Resistor across the control side will in no way affect power to the load.
Mfrom the drawing I didn't realize you're switch was on the control side, agree with them being isolated. In the event of a short of the control side of the SSR, the resistor would prevent a direct power to ground short since the SSR would have no impedance.
Thanks for posting this. I am running a Goldbox with the same SSR for methanol injection. I haven't had any issues and all is working well but this thread makes me think I should install a resistor as well as a diode. Is there any reason not to?
To clarify, the resistor goes between the 12v switch side on the SSR and ground from Goldbox (signal out) to the SSR and the diode can go right off the wires of the pump (in the back of my car), shown as above from negative to positive?
Thanks for posting this. I am running a Goldbox with the same SSR for methanol injection. I haven't had any issues and all is working well but this thread makes me think I should install a resistor as well as a diode. Is there any reason not to?
To clarify, the resistor goes between the 12v switch side on the SSR and ground from Goldbox (signal out) to the SSR and the diode can go right off the wires of the pump (in the back of my car), shown as above from negative to positive?
Thanks in advance,
-Jrod
Put the diode as close to the pump as possible and make sure its installed with its polarity opposite of the pumps polarity.
The resistor can go on either side of the control side of the SSR. Either from the SSR to ground or from the Goldbox to the SSR. This assumes the Goldbox is an active high.
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Solid State Relay Experts - Please Come In 
