Correct. A solid state relay is a different beast, and requires little voltage and internally limits the input current as well. You can checkout the datasheet HERE

 

I see. So with the 11v zener and the minimum input voltage being 3.5v on the ssr, the circuit will still work okay?

I appreciate your help.

 

Yes for my car the 11v zener did the trick. I recommend buying the pack of various diodes from amazon because then you can "tune" the electrical circuit as needed. If you have a healthy alternator and battery, the 11v works perfectly to "fire" the solid state relay when the OEM ECU sends the "hi voltage" to the stock fuel pump. My car would send 14.5 to the pump when in "hi voltage" so 14.5 - 11v = 3.5v which is that the solid state relay needed to turn on. Let me know if you need more info.

 

Just wanted to add a little a few things.

1.) I'm still running (without issues) the DUAL pump setup with multiple track days and NY temperature snaps.

2.) With the new radium fuel pump hanger now offered, I am thinking that just the radium pump hanger (in-tank-tank) and the SINGLE pump design HERE would address 99% of Evo X owners out there.
You could just put one big pump in that beautiful radium in-tank tank and be done with it. Or even opt for the DUAL radium pump install option, whatever. Just change your ECU to flip to high power when you calculate the pressure would fall off at the lower pump voltage.

 

Thanks for this. I'm in the process of installing a FST for this track season after having some fuel starvation in Homestead (left turn AND banking right after!) so I've been researching the parts and how to put them together.

Here's a question; I ran into this part while researching automotive SSRs and thought it was interesting -
https://www.holley.com/products/elec.../parts/7564-HC

The listed Crydom parts have gone up in price significantly these last two years it seems, so the two SSRS + DC-DC power supply are slightly more expensive than the MSD part above, so I got to thinking.



Disclaimer: I know next to nothing about electronics outside of wiring up my gauges and patching them into Racecapture. I'm more of a software guy

How likely is for this design to work, or not work? I imagine the Zener diode down-stepping the voltage supplied by the battery is the big point of failure, where if anything goes wrong, the fuel pump gets cut off from power if the car is below the high-power load. In my case, the lift pump is a Walbro 255, and the surge pump is a 450 - so I think the 35A limit is just fine for my uses. The car only makes around 400 and I don't have plans to go further.

 

You can get a pack of zener diodes from amazon to "tune" the top diode.
The bottom diode needs to be a beast of a zener, because you are actually running actual CURRENT through it to power the pump in low-speed mode.
They DO make them, and I checked online and you can snag one for $10. I had no idea the Crydom relays have spiked, I think I might have some laying around.
I became addicted to them because there was an onslaught of bad SSRs being made in China that were burning up everywhere. They basically had FALSE power/current ratings. There was even FAKE Crydom units around too.

That MSD unit seems slick with the high price now of quality SSRs.

Take my input with a grain of salt, as I have not tested your setup on the bench. Always proceed slowing and methodically, and test at rest first. You can flash the ECU to switch from lo-high for the fuel pump by changing the curve to be JUST above idle. So have a buddy tap the gas while parked and hold revs just enough to prove your switching correctly with a volt-meter.

 

I ended up with a full Radium fuel system with a surge tank and I'd be happy to pass my Crydom relays on to anyone who wants to tackle this project!
I also was looking at the Kaizen tuning SSR as it's really affordable and seemed like a perfect fit.

A big thanks to Jaraxle for creating, maintaining, and responding to this thread!

 

Dang, thanks for the quick response!
Yeah, I did run into lots of suspiciously cheap "Crydom" SSRs looking around and it seems like an issue. The 20 and 40 amp units would run together what the MSD unit above costs, so it might be worth a shot.

I did more research about the Zener diodes in a higher current circuit, and I don't know if running it simplifies or complicates the entire system because if I understand it correctly, resistors are recommended in series so the excess current not being passed through can be dissipated. At that point things get wholly more complex for the layman like me so I looked at out of the box voltage regulators. I didn't find anything simple and ready-made that didn't involve yet more complexities I'm not confident I could figure out and so... I landed back at the Castle Creations power supply. It seems perfect for the job it's tasked with doing, and with a range of adjustment that will get the 450 at the right idle fuel pressure.




Those Kaizen SSRs also look pretty nice, but if I can make the MSD unit work, that would be nice since I could use the two other circuits for other things; I have been mulling controlling my SSP SST cooler with my Racecapure for a while, so that might be a good project to add to the list.

 

You have an extra diode on the OUTPUT2 line that isn't needed. Otherwise, it looks for the most part to be my design but adapted to the MSD relay unit.
I think it would work. As mentioned earlier, you may need to tweak & test the output 2 zener diode to insure it properly fires the output2 when the input voltage from the OEM ECU goes high.
It maintains all the goals of the design, with the most important being it will KILL power to your surge pump if the ECU cuts power to the in-tank pump.

 

Update coming!!!
While the dual pump setup for my vehicle has worked great for years, I am updating it to include a boost-a-pump which provides a third level of voltage. This is to prepare my car for a GTX3076R Gen2 installation with ARTEC manifold.

The results will be:

1.) In tank pump off, then secondary pump is off : this is a rule that must be met for safety. The car cuts the fuel pump when the airbags are deployed. You don't want some fuel pump pushing fuel into a fire situation!
2.) If the car is in VAC then the tank pump is lo voltage and the secondary pump is low voltage
3.) If the car enters boost then tank pump stays lo voltage (which is ok since it isn't fighting any pressure), and the secondary pump goes to 13.5v
4.) If the ECU decides that HI voltage is required (configurable curve) then tank pump goes to HI voltage and secondary pump goes to BOOST-A-PUMP voltage which can be set at 17v or 23v

 

It's been a while! I ended up taking an ungodly amount of time to finish painting the car in my garage (had to clear coat it a second time...) and that meant everything got pushed back.

Thanks for the heads up on the extra Diode, I took it out of the circuit in the final version. I bought a fuel pressure sensor to keep an eye on what pressures I had been running normally, then found out that the shop who installed my pump hardwired it full time, so it was running at peak power constantly for five years and my idle fuel pressure was 78 PSI. I did take some measurements of fuel pump voltage while the car was running, and 10.5v slowly seems to climb up to 10.70 or so with load before the relay kicks in and sends full voltage back.

I benchtested it, and the 7.5 zener diode was the right choice as the MSD relay unit seems to activate somewhere around 4.5 - 5v, and I didn't want it triggering too early. So I programmed the CC BEC to 11v, and I was getting around 10.3 at the pump, which is enough to bring idle fuel pressure down to 56ish PSI, 51 or so after driving for a while I was curious to see what it's do at full blast, and at idle the full voltage 450 was doing 88 PSI at the fuel rail, so there's clearly more restriction getting fuel back into the tank from the FST.

So far my only concern with the setup is the CC BEC, because it's getting up to 170F or so at the heatsink, so I think mounting a fan is basically a necessity at this point. I mounted everything to an aluminum bar in the trunk, hoping it would help dissipate some of that heat, so we'll see. I'm a little nervous about going to the track this Sunday on this setup and little testing, but I guess the best way to gain confidence in it is to actually put it through the motions.

I did a few pulls, and at 25-26 PSI the fuel pressure was holding steady near 80 PSI at the rail so I think I'll be fine.

Needs a bit of final cleanup and tidying things up, but should be a fairly clean solution with the paneling back on, while letting me keep an eye on the MSD relay in case something is wacky.

Oh, and I also added a fuse holder just before the pump with a 25A fuse. It might be cutting it close on the 450, I have seen folks report they use 22, 23 at times, so I may bring the fuse up to 30. The MSD SSR has a 35A builtin circuit breaker, but I wanted an extra level of protection. Will probably bring the fuse up to 40A, just to be sure. I found out that the shop had installed my fuel pump with two 40A fuses, but one of the fuse holders basically melted before the fuse popped, so that was an interesting find.

Edit: So I called Castle's technical support. Basically the temp limit of the BEC Pro is 220F, so there's still a bit more leeway. I might look at installing a thermostat-controlled fan, just to keep noise levels down if possible.

 

I forgot to mention. I threw a small server fan (12v) on the heatsink! They are super cheap and can probably get it at BestBuy or Microcenter or Amazon.
"So I programmed the CC BEC to 11v," - wouldn't you want it lower than that?
Cool project!

 

You'd know, it's YOUR project :P

I did see your fan in the pictures, I looked for a small one in my endless stash of old PC parts but the smallest fan I have currently is 100mm, so it will be rather goofy. But I'll install one ASAP.

I measured the voltage from the car and it was providing 10.5 volts at idle to the pump, so I figured I'd start there. The diodes drop voltage about .5 or so it seems, so what I'm reading at the FST pump is 10.3 ish. But I'm sure I could go lower, the current voltage is probably the culprit of my sorta high idle FP. When I have more time I'll play around with the voltage and see where I can keep it. I don't think I want to drop it too much, since as we were driving I saw the voltages slowly increase at the stock pump (before the relay gets engaged).

I should get some good logs to set up some racecapture alerts, hopefully.