RonSSNova

iTrader: (3)

See what you guys think.

I have the Holley12-1800 as my main pump. Both halves running full time.
I added the Holley 12-890 little brother as a secondary pump on a hobbs set to 15psi.

Wasn't sure if I needed a check valve for the second pump so I added one. A Summit valve.

What happens as I approach 80psi pressure, top of second gear only, and it's consistent, I lose 10psi for less than a second. From there on it's solid.
55psi base, I'm running 24 psi boost.

Comes right back, but causes a bit of a lean area.

So, if the main pump makes more pressure than the secondary pump. check valve needs 1 psi to open, any chance that the differential pressure ie main pump is more than 1 psi higher than the secondary pump for a brief period, the second pump can't add?

I'm going to remove the check valve. And test. Then wire around the hobbs, it's an expensive Honeywell unit. But nothing is failure prone.

Thoughts?

Ron

forcd ind

iTrader: (7)

Is it a sumped tank? I ran a 12-1400 for 3 years, staged the 2nd pump to come in under boost (also as a backup if pri failed on the road)
Orig forgot to fuse the 2nd pump, but the pri was keeping up with 12 lbs boost, lol-I would think the 1800 should handle it, IF both pumps are working (there was a little history with the 1800's)
Is there a voltage drop as the third pump comes on, until the alt can pick it back up.
Does the second pump use the same line from the tank, or a sep one-I guess if one pump had a diff pressure it might cause a slight cavitation in another pump-my first thought was the 1800 could be pushing fuel back thru the other pump (path of least rest.) but with a ck valve it wouldn't happen.
I am guessing your data logging, any other event happen at the same time
Yep, on my second cup of coffee and wired, lol

svslow

I would have the 2nd pump come on at a lower boost level. I bet it takes the turbo less time to go from 15psi to 24psi than for the 2nd pump to come on board.

coltboostin

Yes. As long as the regulator can bypass enough there is no reason to not have it on at 5 psi

RonSSNova

iTrader: (3)

I agree I shouldn’t have picked 15psi for the Hobbs. It’s adjustable, but only a few psi.
I tested with all three pumps on with the engine off and triggering the second pump only upped pressure 1psi.
Voltage during a run is rock solid.
For next year I’ll get a lower pressure Hobbs.
For the test and tune Sunday I’ll just put a switch in so I can turn all three on prior to a pass.

Ratical

iTrader: (82)

If you need a lower pressure Hobbs Ron I have 2 left brand new that I am not going to use. I bought 3 and ended up wiring my BAP through the Holley. (Set at 103kph to activate btw) I know they are adjustable but have to remember the range. I know it is low like 4-10 psi or something.

fieroguru

iTrader: (1)

Any chance the electrical draw for the 2nd pump kicking on is momentarily pulling down the voltage available to the primary pump?

Do they share the same power feed?

RonSSNova

iTrader: (3)

They are individually wired with HD 125 amp relays and 8 ga wire.

stevieturbo

Does the internal pressure relief on those pumps not start to operate around 75-80psi anyway ? That wouldnt help matters ?

RonSSNova

iTrader: (3)

Good question. I’m not sure if this info is available for these pumps. Once the pressure comes back it’s right at 80-81 psi.
I should try reducing base pressure a tad as well.

stevieturbo

I think they're just Walbro pumps inside the Holley housing anyway ?

RonSSNova

iTrader: (3)

That has been said. Not sure if it’s proven. I’ve read all the diatribes on the pumps. Myself I’ve had no failures. Or issues until this odd behavior. Which didn’t happen until I upped the boost.

RonSSNova

iTrader: (3)

A screen shot of a log. My fuel was dead rich on this pass.

MelloYello

I run the same 1800 pump, and trigger the one side after 6psi and 3500rpm. I had a pump failure when I had both sides running all the time. Was also told to lower base pressure so not to exceed 75psi in boost. Logs show rock solid and running fairly similar times in your signature.

RonSSNova

iTrader: (3)

Mellow, sneaking in here?
My logs show it making it to 80 psi....barely. So I'll lower it to 52 base and live with over 100% idc. My 1800 has performed flawlessly for 5 years now.
I'll know tomorrow.
68 degrees, sunny, prepped track and I'm going for it.

MelloYello

Ha, ya I figured I'd give my .02 cent opinion in here. I'm at 48-50psi base and may go a touch lower if I add more boost.

Good Luck tomorrow!!

ls1_chevelle

iTrader: (9)

Cut your losses and throw the holley trash pumps in the garbage. Just saw youve had it for 5 years, its a unicorn pump lol.

Stock ecu? Ive been running a magnafuel 4301 with no pump controller. Rock solid fuel pressure. Also running ID1300s at 43.5 base fuel pressure. Love the setup.

69-chvl

iTrader: (11)

Ron, can you run the 12-890 as a primary pump and kick-on the dual pump as required?

RonSSNova

iTrader: (3)

I'll follow up.
I turned the base down to 52 psi and had no issues.
Max pressure hit 77 psi, boost was wavering between 24-25.
I believe Stevieturbo was correct on the 80psi internal pressure relief. I think those can be removed.

Vince, I can do that. Simple relay trigger wire switch. But on the other hand it's working.....

Ron

RonSSNova

iTrader: (3)

Yes, stock ECU.
My experience with that magnafuel pump in my buddies car that I tune has been horrible.
So I guess we pick our poison.