Big(ish) Hybrids and dropping oil pressure

I'd like to hear from anyone running 300, 350, 400 cc size hybrids, turning over 4k rpms, and what your low pressure oil pressure is.
I have an issue that I am trying to figure out and I think it's the HPOP.
At the end of a 1/4 mile run the low pressure oil drops below 10 psi for several seconds and the engine runs real rough, and often dies and is hard to figure back up.
Some info:
I have 300/200% Hybrids and I am turning 4400 rpm though the lights.
I have a large single HPOP (nameless right now as I am not 100% sure what's going on.)
The datalog shows 3800 psi of HPOil pressure during the whole run.
Low pressure oil shows starting at 65 psi or so when I leave the line and drops a few seconds after launch to about 35 psi, and stays steady unit it then drops suddenly after I let of the throttle at the end of the run. It recovers by the time I am at the end of the shut down and enter the return road, where the engine runs very rough, if at all.
I was thinking I had a low pressure issue, but believe I am now experiencing other High Pressure Pump issues that I am suspecting have been my problem all along. I am thinking the HPOP is drawing the low pressure system down, somehow. The pump is still turning 4400 rpm (or whatever the ratio is) when I let off so it's still moving a LOT of oil that has to go somewhere.

Anybody else experience anything like this?

I have heard of big gear oil pumps commonly known as the gen3 rather its homemade or not cutting off at the end of the track after a hard run. I have always heard all you needed was around 3200 psi of oil pressure so 3800 seems a little high for me


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Agreed, and I know there's something in the tuning to tweak on the psi.
But it's moving a ton of oil regardless if it's at 3200 or 3800 psi. If it's dumping oil out the pump's internal bleed off, or dumping through the IPR to maintain 3200 psi, shouldn't matter for what it's doing. It has no choice but to move a lot of oil at 4400 rpm anyway you look at it.
I am wondering if there is an internal issue in the HPOP, or if I need to come up with a better/different lube oiling system. I do have the high flow low pressure pump, too.

Id try 2 extra quarts in the pan and make a pass. Could rule out a bunch of things

What are you thinking it will rule out?

I thought maybe I was running out of oil in the pan, too, but pressure only drops once I let off on the throttle. It's not like it looses all pressure as I go down the track (like no oil left in the pan.) Yes, I think oil psi should be higher than it is while racing, but it only significantly drops once I let off at the and of the 1/4 mile. I have many graphs that shows this with the data-logger.

I also have an external pressure regulator (no room for factory stuff) that is set at 80 psi at 3000 rpm. Obviously this is sitting still revving it up and not running down the track. So something is opening up and not allowing it to build this kind of pressure while racing.

I thought maybe it was sucking air.

What about the pressure relif valve in the oil filter housing??
Maybe something in there is opening to soon. Just throwing that out there.

No relief valve, no stock filter housing or oil cooler. I just have an external pressure regulator, that's it.

Dual iprs, or single?
Sounds like the hpo may be pulling the lpo down throughout the run, and that condition is exaggerated at the end of the run when you come off the pedal?
I m not an expert on these like some guys, but as I understand it the melling "high volume pump" isnt much bigger than the stocker. Like 10% or so.
May need to pull the lpo and spend some time on it.

Single IPR...for now anyway.

So you did away with the factory oil cooler and used a remote one?


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Just some crazy ideas from left field.

Tuning; I know when I had a srp1.1 pump, the tuner did some tricks to limit the ipr so to eliminate spikes. So effectively I believe they changed how quickly it would ramp the ipr changes. Is it possible that when your at WOT, full load and when you let off your oil pump is at full rpm, and your ipr goes to full open to relieve pressure, but now your oil pump has almost no restriction and is literally still pumping as fast as it can (because the rpms are still coming down) and thats sucking up the low pressure oil?

Two scenarios
1) Full load, WOT, 4400RPM, ICP 3800, IPR 40% The IPR is still required to restrict flow, to maintain pressure. lets say with that restriction to make that pressure the pump is capable of 100 gallons per hour at that rpm.

2) Let off, truck is coasting, no pulse width, truck is maintaining 600 PSI, IPR is set to 1% (whatever minimum is) pump has almost no restriction, and the same pump with no restriction coming down from 4400 rpm is capable of 200 gph.

Now youve sucked all the low pressure oil, and maybe some air? Truck comes down to needing to apply pulse width to idle again, there could be air in the system, or it could need to command the ipr to increase pressure.

One way to test this crazy theory, next time you run down the track, AS SOON as you let off, put it in neutral and let it fall to idle immediately. Or put it in neutral and give it some throttle to keep rpms at 1500-2000 rpms as soon as you let off. I bet keeping rpms up under power and not coasting will keep it running and let low pressure oil stay up?

Powerstroker7.3 said:

So you did away with the factory oil cooler and used a remote one?

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No oil cooler, it's a drag car, not needed. I thought about adding one, just not a lot of room to do so, and oil temps haven't been a factor yet.

mikeeg02 said:

Just some crazy ideas from left field.

Tuning; I know when I had a srp1.1 pump, the tuner did some tricks to limit the ipr so to eliminate spikes. So effectively I believe they changed how quickly it would ramp the ipr changes. Is it possible that when your at WOT, full load and when you let off your oil pump is at full rpm, and your ipr goes to full open to relieve pressure, but now your oil pump has almost no restriction and is literally still pumping as fast as it can (because the rpms are still coming down) and thats sucking up the low pressure oil?

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Yes and no. It's still pulling low pressure oil, but with the design of the reservoir and supply standpipe the way it is it can't pull any more low pressure oil down than once the psi of the reservoir drops to zero. At that point the low pressure system is trying to fill the res as fast as it can regardless of how fast the HPOP is spinning and moving oil (given that the HPOP is draining the reservoir at whatever pace it is.) There is no direct passage from the low pressure system to the HPOP that would cause it to 'pull' low pressure oil out of the low pressure system. Make sense?

mikeeg02 said:

Two scenarios:
1) Full load, WOT, 4400RPM, ICP 3800, IPR 40% The IPR is still required to restrict flow, to maintain pressure. lets say with that restriction to make that pressure the pump is capable of 100 gallons per hour at that rpm.

2) Let off, truck is coasting, no pulse width, truck is maintaining 600 PSI, IPR is set to 1% (whatever minimum is) pump has almost no restriction, and the same pump with no restriction coming down from 4400 rpm is capable of 200 gph.

Now you've sucked all the low pressure oil, and maybe some air? Truck comes down to needing to apply pulse width to idle again, there could be air in the system, or it could need to command the ipr to increase pressure.

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Exactly. I agree. I think that my main issue is in the external pressure regulator dumping pressure very quickly when I let off, but I am trying to cover all bases to figure this out.

mikeeg02 said:

One way to test this crazy theory, next time you run down the track, AS SOON as you let off, put it in neutral and let it fall to idle immediately. Or put it in neutral and give it some throttle to keep rpms at 1500-2000 rpms as soon as you let off. I bet keeping rpms up under power and not coasting will keep it running and let low pressure oil stay up?

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Yeah, that's a good idea, which I tried. But going 140 mph I'm kind of focused on stopping before I get to the corn field. And by the time I can switch focus and bump to neutral, it's already running poorly.

Any -relatively- simple way to add an external oil feed to the hpop, independent of the lpo system? As in, isolate the two systems from each other, at least partially?

I was considering an additional pump to pull oil from the pan to supply to the HPOP reservoir, but I'm not 100% sure that's the best thing to do. Belt drive would be tough, and I'm not sure if there is an electric pump up to the task. Maybe something I can have come on at the end of the track, so minimal run time.

Also thinking about an accumulator set with a pressure switch to dump oil into the reservoir. But again I think that's a band-aid and not fixing the actual issue.

I'd say fix the tuning first. While it probablywon't change the problem, it cant hurt. Assuming your not giving up any power.

DZL JIM said:

Yes and no. It's still pulling low pressure oil, but with the design of the reservoir and supply standpipe the way it is it can't pull any more low pressure oil down than once the psi of the reservoir drops to zero. At that point the low pressure system is trying to fill the res as fast as it can regardless of how fast the HPOP is spinning and moving oil (given that the HPOP is draining the reservoir at whatever pace it is.) There is no direct passage from the low pressure system to the HPOP that would cause it to 'pull' low pressure oil out of the low pressure system. Make sense?

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Ah yes, the HPOP pulls oil from its reservoir, not directly from the low pressure oil tube. Brain fart. ointlaugh: That would only make ICP drop, or find air. Not pull down the low pressure oil supply. Out of curiosity, I am guessing since the truck runs rough the high pressure oil also drops? Whether it be air or lack of oil supply? I can see why this is a tricky one with the dropping low pressure oil supply.

With gear driven pumps, when the engine runs rough it's tough to say what is the cause and what is the effect.

I have heard from several guys that run low on oil after a hard run with the Gen-3 set-up, but nobody has any issues with a big single, or even twin stock pumps for that matter.
I am leaning toward the issue being my external regulator that needs a bit more dialing in to keep pressure up during a run. Problem now is the track season is about over and my HPOP is trashed. Might have to wait till next year to figure it out.

Jim, been think about this, but would you be able to share some pictures of your set up to help me out?

I have a few idea's but want to see if they make after photo.

Marc

Sure. I don't have anything online, send me an email and exactly what pics you want and I'll get them to you: [email protected].

How about some details on what oil pressure is cold, warm running, ipr duty cycle? Condition of the lpop and cam and rod bearings? Type of oil used?