Controlling fuel pumps with solid state relay pwm

Trickster
Posts: 60
Joined: Mon Nov 28, 2016 6:09 pm

Controlling fuel pumps with solid state relay pwm

Post by Trickster »

Hi
I am currently changing my fuel system to incorporate a surge tank, so I will be running 3 bosch 044 pumps instead of 2.
Ryan gave me the idea a while ago about using a solid state relay to control my pumps through solid state relays to reduce heat into the fuel system at slower speeds.
One pump only runs at higher boost so I really only need to control 2, I have found these relays on eBay, which are possibly just cheap and terrible and was wondering if anyone has had any experience with them?
I have seen a couple of forums where people are using them, but no feedback on it.
If not, any recommendations?
Ebay item 272682121766
These are the ac version, but dc are same price.

At that price I would probably buy a few and start controlling my fans from the ecu too as I have spare outputs available.

Thanks
Graeme
MR2 Turbo 5sgte 750hp 527ft/lb Syvecs S6

Trickster
Posts: 60
Joined: Mon Nov 28, 2016 6:09 pm

Re: Controlling fuel pumps with solid state relay pwm

Post by Trickster »

Can someone move this to the s6gp forum please
Thanks
MR2 Turbo 5sgte 750hp 527ft/lb Syvecs S6

Wez
Santa's Little Helper
Posts: 267
Joined: Thu May 22, 2008 2:19 pm
Location: London

Re: Controlling fuel pumps with solid state relay pwm

Post by Wez »

I would be careful of eBay items as most are cheap copies / fakes, they might be OK at lower than advertised rating though, example here :-

https://www.youtube.com/watch?v=DxEhxjvifyY

For items like these I would be checking reputable suppliers such as Farnell, CPC etc but sadly they wont be less than £10 delivered.
96 MKIV Supra, S6GP, 591bhp & 523ft/lbs

stevieturbo
Posts: 932
Joined: Sun Dec 07, 2008 2:04 pm

Re: Controlling fuel pumps with solid state relay pwm

Post by stevieturbo »

There have been various threads ( oddly can't find them though ) on PWM control of motors.

Cheap SSR may work...but it does seem in general an SSR is not the ideal approach, alrgely because they cannot switch as fast as would be desired. Expensive ones can maybe do up to 1kHz...the cheap ones, maybe 100Hz or so.

Ideally you'd want nearer around 10kHz.

But the only way to find out is to try, it was also mentioned elsewhere that more expensive ones tend to be isolated from the switching source, so in the event of a failure they will not harm the switching source.

Having blew up a Crydom SSR myself.....I'd rather harm the SSR, than my ecu. So factor that in.

There are others using OEM Fan controllers to control various motors and pumps where they accept PWM input, these would be the ideal choice.

Wez
Santa's Little Helper
Posts: 267
Joined: Thu May 22, 2008 2:19 pm
Location: London

Re: Controlling fuel pumps with solid state relay pwm

Post by Wez »

Also, do the Bosch 044 like being run this way?

Having them fully power on/off as required isnt an issue but are they compatible with PWM control?
96 MKIV Supra, S6GP, 591bhp & 523ft/lbs

stevieturbo
Posts: 932
Joined: Sun Dec 07, 2008 2:04 pm

Re: Controlling fuel pumps with solid state relay pwm

Post by stevieturbo »

Wez wrote:Also, do the Bosch 044 like being run this way?

Having them fully power on/off as required isnt an issue but are they compatible with PWM control?

They're a conventional motor. Never heard any reasons why they couldnt be or anyone having problems doing so.

PWM is fully off/on....just very fast lol.

Trickster
Posts: 60
Joined: Mon Nov 28, 2016 6:09 pm

Re: Controlling fuel pumps with solid state relay pwm

Post by Trickster »

Thanks for the replies guys

I am aware there are some copies, I was going to use 40a for less than 20a load just incase and I was also going to install quick blow fuses on the ecu output side to the relay in case an internal failure caused the ecu to take the load.

I am thinking of buying one and controlling a fan for a while to see how they fair up.

The bosch 044 have been used by alot of people with pmw from what I have read.
MR2 Turbo 5sgte 750hp 527ft/lb Syvecs S6

T04GTR
Posts: 51
Joined: Mon Jan 14, 2013 7:37 am

Re: Controlling fuel pumps with solid state relay pwm

Post by T04GTR »

be very very careful, and fit a proper flyback diode. and a 1k resister between the ssr b+ and trigger + and the ecu. i killed 2 outputs on my s12 when i was trying to get a ssr to run a big engine fan. in short. the relay failed (closed circuit) and because i didnt have a resister between the b+ and the "trigger" + on the ssr, it sent full battery power to the output of the ecu. now those outputs have 100ohm to ground. :cry: couldn't put the smoke back in..

usual 100 amp ssr. that was a 50 amp steady state load. 150 inrush.. i just got the oem fan pwm box..

the flyback is the issue. and most 100 amp ssr's on the market only like 100hz or so. at that slow speed, sounds like a jackhammer. and electrically, like a jackhammer aswell. i was only doing 1 motor that runs 50 amps at full noise. 3x044's could pull as much as 60+ amps. and being a pump, they wont coast like a fan motor. so the flyback will be alot worse, as you will be basically trying to make the relay run them at full inrush current.
you will need to get a current clamp and test the actual inrush. and rate the relay to that. because thats what its going to be seeing 90% of the time.

the oem merc fan box i used is great, but.. it only allows for a certain amount of acceleration. ie takes about 5 secs to put full duty to the fan. and if it has battery power and ignition power but no pwm it fail safes to max duty till re-set. ie perform a cal program witch re-sets the ecu. dropping the pwm for a second. or if there is an error on the slave side of the ecu. (the slave side just turns off till the fault is rectified)

Dave.

stevieturbo
Posts: 932
Joined: Sun Dec 07, 2008 2:04 pm

Re: Controlling fuel pumps with solid state relay pwm

Post by stevieturbo »

What exactly is the purpose of the resistor ?

The Crydom SSR's I bought say they're good to 1kHz, but as my first attempted didnt last too long and I fried one.....not really sure what killed it lol I think it was my flyback diode as a wire had shorted out across the diode due to how I heat shrinked it all up.

So sort of gave up on that, but in my case making it work was slightly more awkward as I had my oil scavenge pump triggered off the normal fuel pump live...and it's relay wasnt happy at all with a PWM signal.

I will be revisiting this all again though as I'm changing to in-tank pumps, triple Walbros and I hope to run all 3 and PWM them and see how that goes. Or if that proves too much current, 2 would probably do me fine but I'm installing 3 anyway.
It's either a 60 or 80A SSR I have running at the minute, although just off/on until I resolve the scavenge pump trigger. Also with a larger diode across the pump terminals...and no problems there either.

But I've never had a resistor across the SSR input, and it seems to work fine without it ?

Trickster
Posts: 60
Joined: Mon Nov 28, 2016 6:09 pm

Re: Controlling fuel pumps with solid state relay pwm

Post by Trickster »

Didn't notice these replies! I have just received some ebay 40a fotek SSR's. All my fans and fuel pumps have individual fuses and relays, and all on 15 amp fuses. They all pull just under 15amps each.

I chose 40A continuous ones as the copies usually have 25A triacs, so I thought even if they are fake they will be ample for one per fan or pump. I am going to install one on a fan and run it to see how it holds up (not ecu controlled) they are supposed to handle ten times the rated current for surges also.

The output side is supposed to be isolated from the input, but I am worried about a serious fault causing current draw through the ecu, my idea was to just fit 500mA quick blow fuses on the ecu outputs? Wouldn't that be sufficient protection?

I noticed the syvecs manual shows a flyback diode, are these necessary or not?

I am tempted to dismantle one of the relays to see what components are actually used, but think I will just load one up and run it for a while first.

Graeme
MR2 Turbo 5sgte 750hp 527ft/lb Syvecs S6

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