It can't be connected to both terminals of the SSR. That would put it in parallel with the terminals and do absolutely nothing in the event of a short. It needs to go in series with 1 of the terminals. This way if it does fail the current path still has the series impedance of the resistor to prevent damage.

 

The resistor does go across both terminals of the SSR on the control side, the Haltech schematic clearly shows this.

 

I don't care what haltechs schematic shows. I do electrical design for a living with a specialty in failure modes. If the SSR input shorts and the resistor is in parallel with the 2 terminals all the current will bypass the resistor by way of the shorted SSR terminals and you will short the gold box/driver straight to ground.

 

And applying a ground to an ecu output will pose it no trouble at all as switching to ground is their normal operation.

Here is one on a friends car in use for years...and nothing to do with Haltech

 

can we go back a sec and have someone explain like i was five what the resistor does?


in my application (2 non-pwm walbro 450's) I trigger my SSR with a regular FP relay (with a flyback diode)

my understanding is that the diode prevents a voltage spike to the ecu when the relay goes from charged to uncharged


i really wish basic electronics was a requirement in school.

 

As you say, the diode across the inductive load is to allow any flyback voltage/back emf to dissipate in the motor itself ( or in your case a relay ) rather than going back into the SSR itself.

The resistor other than for some sort of protection, not honestly sure. Although I have also seen some suggest that some setups the SSR may not switch off correctly without a resistor in place, although if the +12v of the control side was also ignition based that might not be a concern

 

It doesn't hurt the ecu when sinking current....it DOES hurt the ecu when you have the ecu drive an active high and you directly tie ground to it.....unless the ecu has an internal pull-up and isn't a direct high. You'll blow the internal fet otherwise.....and your friends been dlike that for years with no damage cause the SSR hasn't failed. You obviously are saying you can't explain what it does and I'm explaining but you don't believe it so why bother.

 

Yes I dont know exactly what it's purpose is....but when everyone else is saying to do it this way including ecu manufacturers....the question is why ? Are they all wrong ?

And as you know ecu's do not drive "active high" for this type of thing or indeed almost any of their outputs ( aside from an H bridge ). They all pull to ground.
At least I havent seen any that will drive high as standard for this type of output.

 

It doesn't matter if the ecu is sourcing power and the other side of the SSR is tired to ground or if the ecu is sinking current and the other side of the SSR is tired to power....the failure modes is still the same and if the resistor is still in parallel and the SSR fails to a short condition, the ecu will still be damaged.

As far as why everyone does it this way....if haltech simply drew it wrong and everyone follows their drawing.....that would explain why everyone does it wrong. If there is no other V drop in the current path, then you can't even make the case that the R is providing a fixed voltage across the SSR terminals.....so it STILL doesn't do anything.

 

Haltech are not the only people stating this, they just have the most convenient schematic.

And out of interest....are all SSR's the same in terms of failure/safety ?

I've heard some....most cheap SSRs have no protection whatsoever. Whereas the more expensive versions tend to be "opto-isolated" so any failure on the load side cannot impact the control side ?

I did completely fry a Crydom SSR through a fault ( self inflicted ) on the load side. I also had no resistor on the control side anywhere.
And no harm came to my ecu ( thank **** )

 

The control side is the failure modes I'm referring to. None of what I stated has anything to do with the load side. The control side may or may not be optocoupled as you mentioned or some type of FET etc, but all optos can have the input LED short circuit and all FETs can have any combo of gate drain source shorts. The end result is still the same, if you are sinking or sourcing current and you don't have a current limiting resistor in the circuit, it will be a dead short. It's not a load to control short I'm concerned about, it's just the control side having a short circuit in the event of a failure.

 

ok so the resistor thing is going over my head but i trust an EE that makes 4l60e's live at 700+ wheel lol

in that picture of the SSR above, how would the resistor be oriented? from #1 to #4?

i'm using a 5 pin with a diode to send a "hot" trigger to my SSR. I'm doing this so I dont have to run 6awg all the way back to my pumps.

 

Resistors are not polarity sensitive ( nor are they marked either way anyway )

 

From what I gather in that pic pins 2 and 3 are hot tied to a 12v source....pin 4 is the input side so I assume that is where the ecu is tired sinking current to drive the control of the SSR....since 2 and 3 are jumpered you can't put the resistor in series there. So remove the wire at pin 4 and put the resistor in series going between the terminal and the wire coming from the ecu. Make sure you get a resistor that has the right wattage. P=vi=i^2r. We always use 50% derating on resistor power ratings.

And I make 700fwhp lol although well see what happens now that my belt slip is better, hoping to crack 600whp and 10s on the stock 10 bolt and 4l60e

 

Here are some results from the track today.

I replaced the 2 std FP relays with ones with built-in diodes (BWD R683) and put a 1K, 1/4-watt resistor between the 3 & 4 on the SSR. Could not source a 1N4007 diode locally for the alky pump. I then tested it by rigging up the main FP to run continuously with a test light on the relay 87, then used the MS Testmode to pulse the SSR/alky pump at 45%. Light stayed on steady.

At the track, the first 2 passes had no issues with the fuel pressure matching base + boost all through the passes. For the 3rd pass, I upped the boost a tad (1psi on the dome netted .8psi) and increased the alky PWM from 40 to 45%. At .5 sec into the pass, it spun and I pedaled and it got back to full boost at 1.5 secs, but at 1.9 secs the fuel pressure started to oscillate like before dropping as low as 49psi at 18.7psi boost (43 base). I threw out all those numbers and times because I was looking for a correlation to the previous bad runs and don't see one as the fuel pressure was normal well pass the alky turn-on point on the initial launch and on the recovery. It's possible i'm maxing out the pumps, but I run E70 with 2 AEM380s with the 2nd pump coming on at 7psi with a BAP at 17V. It's also possible I really need that diode on the alky pump. So, a question for the experts in the thread. Would this issue be fixed if I replaced the FP relays with SSRs? I would not be pulsing them, but being digital, I'm wondering if they are less susceptible to this issue than contact-type relays.

Frustrating!!! What's encouraging is that with even with the pedal and this fueling issue, it still ran 159.74. The 60' with the spin was 1.637 and if I could have gotten my normal low-mid 1.20s, the 9.043 ET might have been a...........but that's all coulda, woulda. I really need to fix this issue and get the suspension dialed in.

Appreciate any feedback.

 

Sorry Stevie, this made my simple brain think it should be in series with the wire from/to SSR.
I shall remove myself and let the non-newbs carry on.

 

Swapped out the FP relays for ones with diodes and put the resistor across control side of the SSR and it did not fix the problem. Ran the car yesterday without the alky and had no issues. Don't know if it is the SSR or the MS doing PWM, but I don't care as I won't use it again. I have enough headaches with suspension issues causing the car to spun after it launches. Gonna have a chassis shop fix that.

On a positive note, despite spinning and pedaling and without the alky, it ran 162.55 out the back door with 20psi without the alky. From this point on, I'll just run a smaller nozzle, do a simple on/off and tune the turn-on point.

 

As an update.

I finally got my own running again after some winter changes.

Switched from a pair of inlines ( was 044's then AEM's ) to an in-tank setup and currently running a pair of 450's
Crydom 60A DC series SSR, wired as the Haltech drawing, including the 1k resistor ( I had it running before without the resistor though )

I've had it running with duty as low as 40% and highest around 90% so far and operated at 850Hz ( Spec says it can do 1Khz )


Most notable thing compared to the external pumps ( engine off ) is the silence. A couple of times I didnt even think they were running ! lol.

I havent looked at how much current they're drawing at the different duties yet but will do at some point.
I havent noticed any real heat build up in the SSR either although it is bolted to a big heat sink, which in turn is welded to my alloy fuel tank. Maybe have an hour or so drive time on it which would be mostly around 40-50% duty.

 

this is likely why you're not getting heat build up in the SSRs, you have an awesome heatsink. Glad it's working at such a high frequency

 

I'd have expected to feel some heat on the body though ?

Although at 60A rating....I shouldnt be anywhere near this, especially at the low duties ( and 45psi base )

Ultimately I have 3 pumps in the tank, but only using 2 at present. If I ever do move to ethanol I may need 3 and if so would intend to just run all 3 full time, PWM'd the same way to keep things simple. Or I could stage them if need be but it'd involve adding more wiring.

Wiring for the SSR is jumped into the 70A normal relay holder I had so can easily revert back to a normal relay if things did go **** up.