Loss of oil pressure during vtech operation.

[nsxspdfreak]

Just my experience regarding the factory specs on oil pressure.

My racecar's engine upon purchase had 'in spec' oil pressure but still have completely wiped mains. Upon replacing the mains and oil pump gear, the oil pressure measured at the oil pressure sending unit as you are, would exceed 90psi fairly low RPM (3000rpm) vs your 65 @ 4000rpm, and as regan mentioned, on load, well exceeded 100psi and maintained.

Thanks for the Input!

I might be preaching to the choir here, so I apologize in advance if I am. I would expect to see a pressure increase at lower rpms due to the increase in flow from a high efficiency pump, if that's what you installed. At higher rpms pressure/flow is going to be limited by the relief spring in the pump and by the resistance to flow built into the motor. Fresh mains will also increase pressure just due the tighter tolerances through the mains resulting in a greater resistance to flow, which is dependent on the speed that positive displacement pump is spinning at. Pressure by itself is not necessarily indicative of good or bad oil flow. Pressure is static. The manual states only the min. pressure of 50# at 3000 rpm so I don't know what the max pressure is at a given rpm/flow rate. In vtec the system expects to see 57# at 6000rpm coming out of the far end of the crankshaft. If it doesn't, it assumes that there is a pressure/flow loss at the crank so it cuts off vtec oil in attempt to save the motor. You could also have ridiculously high pressures due to too much resistance to flow, but with very little flow. There are other variables that could have caused your wiped mains like possible momentary loss of pump suction due to g forces, inferior oil, or wrong viscosity. When I bought my car it had 40w oil and it sat in storage for 15 years up North with only 6k miles put on it, so it's hard to say how long it sat there between starts and starts in cold weather. The longer it sat between starts, the less oil film was left on the bearings to provide lubrication until the oil pumped through the system.
I'll do another pressure test at the pump when I resolve the vtec issue. I don't plan on tracking the car anytime soon, but when I do I'll install a HE pump and probably an Accusump.

 

[integrals]

My wiped mains were caused by a prior tuner before I owned the car, running the car insanely rich. Rebuild had to happen upon purchase (crank was replaced, thanks to the prior owner and Jim Coz). I am using all OEM parts (pump and mains) all setup in the middle of OEM bearing clearance tolerances.​

Yes the fresh mains is definitely the reason my oil pressure increased dramatically over when I received the car. My point was that at 50psi at 3k rpm (which is about what the car did when I got it), the mains were still destroyed, and the engine couldn't build any additional pressure as RPM increased due to loss across the mains. Rod bearings were replaced as well obviously.

I am quite familiar with the VTEC system hehe The relationship between oil volume and pressure is quite important!

I do hope your problem isn't as severe as mine, but low pressure at low rpm usually is not a great starting point. I spent about 1 month hoping to god it wasn't what it ended up being. I wasn't even throwing low oil pressure codes from the VTEC Spools. Was quite a disappointment!

Let us know what you find!

 

[Mac Attack]

I took the car for several test runs after connecting the test oil pressure gauge to the Vtec test port on the front head and then on the rear head. At over 6k rpm when the spool valve opened there was 0 pressure at the front cyl head test port. Pressure on the dash gauge dropped to less than 1 and the CEL activated as it's done before. This is indicative of the oil free flowing somewhere other than into the rocker arm shaft or without the oil return restricting orifice to maintain pressure in the shaft\. On the second run with the test gauge attached to the rear head the pressure jumped from 0 to 60# when the spool valve opened. Pressure stayed at 60# until I backed off out of vtec. So now it looks like I have it narrowed down to the oil circuit in the vtec rockers and shaft on the front head. At least I now know that the pump is performing at 100% and I wasn't at risk of wiping out the motor from lack of lubrication. Tomorrow I dive into the front cylinder valve train. It almost looks like one of the vtec pins or the return orifice is missing.

Yesterday I did an air test on the vtec system and I found a massive leak somewhere between the #4 and #3 cam bearing cap. I didn't do the test 100% correctly so I have to do it again, but I'm pretty sure that's were the oil is free flowing. Most likely something I did on when I installed the new head or I'm missing a vtec hydraulic piston in a vtec rocker that I didn't catch.

Joe

That's what I thought previously, but your troubleshooting above indicated acceptable oil pressure with either one of the banks VTEC disengaged. If you go to the trouble removing the front camshafts, I would certainly remove the rear camshafts to check if the same mistake propagated over there too. It's not much more work, and then you'll be 100% certain.

- - - Updated - - -

.... I would expect to see a pressure increase at lower rpms due to the increase in flow from a high efficiency pump, if that's what you installed. ......

I don't plan on tracking the car anytime soon, but when I do I'll install a HE pump and probably an Accusump.

Has anyone overlaid the aftermarket gears (Toda, Dali [Prodrive], Comptech, SOS, etc) with the OEM gears?

The basic gerotor design they all share can only be altered by width or lobe design. I doubt they vary the lobe design. Already the OEM gears lack a certain amount of metal, any opening them up more to increase volumetric flow would weaken them further. I highly doubt any of the aftermarket gear suppliers changed the geometry other than increasing the gear width to simply supply more oil volume. They are just made of different materials.

The aftermarket high volume gears are not high efficiency gears since they just increase the gerotor width (and require the aluminum OEM housing to be machined accordingly). As they are moving more oil for a given crankshaft RPM, they actually consume more energy and it may be wasted unless your bearing clearances are huge (i.e. your machining tolerances are poor).

Hence, unless I'm wrong and the aftermarket gerotor geometry is different than the OEM gears, there is no "high efficiency" oil pump. I know for a fact that the Dali one I bought was exactly the same dimensionally. The Toda and SOS gears are marketed as drop-in. I think only Comptech offered a thicker oil pump gear.

 

[nsxspdfreak]

That's what I thought previously, but your troubleshooting above indicated acceptable oil pressure with either one of the banks VTEC disengaged. If you go to the trouble removing the front camshafts, I would certainly remove the rear camshafts to check if the same mistake propagated over there too. It's not much more work, and then you'll be 100% certain.

- - - Updated - - -


Has anyone overlaid the aftermarket gears (Toda, Dali [Prodrive], Comptech, SOS, etc) with the OEM gears?

The basic gerotor design they all share can only be altered by width or lobe design. I doubt they vary the lobe design. Already the OEM gears lack a certain amount of metal, any opening them up more to increase volumetric flow would weaken them further. I highly doubt any of the aftermarket gear suppliers changed the geometry other than increasing the gear width to simply supply more oil volume. They are just made of different materials.

The aftermarket high volume gears are not high efficiency gears since they just increase the gerotor width (and require the aluminum OEM housing to be machined accordingly). As they are moving more oil for a given crankshaft RPM, they actually consume more energy and it may be wasted unless your bearing clearances are huge (i.e. your machining tolerances are poor).

Hence, unless I'm wrong and the aftermarket gerotor geometry is different than the OEM gears, there is no "high efficiency" oil pump. I know for a fact that the Dali one I bought was exactly the same dimensionally. The Toda and SOS gears are marketed as drop-in. I think only Comptech offered a thicker oil pump gear.

Not sure about Toda, but the SOS gears require re-machining the housing and are supposed to deliver more than the OEM unit at a given RPM. At least that's what's advertised.

I'm in the process of breaking down the top end of the motor again, but I did one more test before I did. This time I triggered the front vtec solenoid manually from the cockpit at about 4500 rpms. I wanted to repeat the vtec operation several times without driving at high rpms and without the ECM disabling the vtec due to a low oil pressure fault. I also installed the SOS oil pressure sending unit upgrade. This time around when I initiated vtec oil pressure on the dash gauge dropped from 6 to about 4 rather than down to <1 as it has done before, yet I still had 0 pressure on the test gauge connected to the vtec test port. I'm assuming that the dash gauge didn't drop to <1 was most likely due to new SOS sensor being more accurate than the old OEM unit. Unfortunately there was no way I could tell if the vtec rockers actually engaged. Either way I'm still getting no oil pressure after the spool valve. I'm going to first pull the cam bearing caps to see if the dowel pin under the front bearing cap is installed. I know the oring is since I replaced it twice already, but I can't remember if the dowel is in place. It's not in the bearing cap from the old head so I should have transferred it over, but I can't be sure. If the dowel pin is installed then I'll move onto the removing the rocker arm shafts. Before I start I want to come up with tool that I can use to clamp the the other bearing caps down while I remove the #1 cap. This way I don't have to release the tension on the timing belt. I found a thread from 2011 from a guy who had a similar problem with his vtec and and made a tool to hold the caps down while he removed #1 . His problem turned out to be blockage in the oil circuit to the spool valves at the back end of the block. That's not my problem.

 

[nsxspdfreak]

Vtec Loss of Oil Mystery Solved

This weekend I did some additional testing on the system including pumping propane into the rocker arm shafts so I could see where it was leaking by igniting the propane. This sounds extreme, but it was done with a very low volume of propane and the source was shut off as soon as it was ignited, so only the residual gas burned off in few seconds. I also removed the rocker arm shaft caps on the head and blew pressurized air directly into the end of the rocker shafts. The propane indicated that the oil was leaking from between the shaft and the rockers. The air pressure test failed to actuate the vtec pistons and only resulted in air blowing out unrestricted around the rockers also. Without the cams in the way I was able to verify that all the rockers had the pins installed so that was not the problem. At the same time I had reassembled the old head with the rockers and repeated the air test on it. The bench air test on the old head/rockers actuated the rockers as expected. The next step was to remove the shafts to see what was happening, which I was able to do with the motor in. What I found was that the shafts that came with the new head were milled incorrectly or were from some other motor. The holes that port the oil into the primary rocker arm to push the piston were instead partly lining up with the rocker arm on the other end of the assembly allowing the oil to exit the shaft directly into the top of the head. You can see this in the photo. The shaft at the top of the photo is the new shaft and the two at the bottom are from the old head. All 4 shafts in a motor are identical and cannot be reversed, so the two new shafts are totally FUBAR. I checked other Honda V6 motors and found that the shafts are the same for all 3.0 & 3.2 motors from 1991 to at least 2005. This head was from a new unused parted out motor that had belonged to a Acura dealer. The dealer had it in their inventory, but sold their inventory when they went out of business. Another company bought the motor and then parted it out so somewhere in the process the shafts were swapped.

 

[Mac Attack]

Great troubleshooting, but sucks you had to go through that.

After a thorough inspection and cleaning, you should be able to use your old shafts no problem.

 

[nsxspdfreak]

Great troubleshooting, but sucks you had to go through that.

After a thorough inspection and cleaning, you should be able to use your old shafts no problem.

If I got anything out of it, it was a great learning experience. The old shafts with only 54k miles on them are good to go, but If I wanted to install new they are an amazingly cheap part for and NSX @ $65 each.

 

[RYU]

That's like my worse nightmare come true. You are the man Joe. Your perseverance is awesome man.

 

[nsxspdfreak]

That's like my worse nightmare come true. You are the man Joe. Your perseverance is awesome man.

Thanks RYU! Having the old head and internals around to bench test and make comparisons helped. In a million years I would have never guessed that the shafts were milled incorrectly. Other than having to take the head and timing belt apart more times than I care to remember it actually turned into a brain game. I felt like a detective trying to unravel a murder mystery while making sure I covered everything before moving onto the next step. The ultimate driving force was not only getting the vtec to work, but to do it without having to pull the motor again. I'll be putting it back to together this weekend, and if all goes well I'll post a video showing side by side view of the dash oil pressure gauge and the test gauge connected to the vtec port. In all my investigating I couldn't find one video of the dash oil pressure gauge vs vtec oil pressure when vtec is activated or oil pressure at the filter vs oil pressure on the dash gauge.

 

[nsxspdfreak]

Vtec is back alive and well!

FINALLY VTEC!!!! :biggrin: The correct rocker arm shafts work like a charm! First time since I bought the car in Feb it's running like it's supposed to. With the new SOS oil pressure sending unit oil pressure stays put at 5 kg/cm2 even with Vtec engaged. Just have to hunt down a minor coolant leak in the vicinity of the two hoses connecting the motor to the alum pipes.

https://www.facebook.com/video.php?v=10206860246797002

 

[Burny-B]

FINALLY VTEC!!!! :biggrin: The correct rocker arm shafts work like a charm! First time since I bought the car in Feb it's running like it's supposed to. With the new SOS oil pressure sending unit oil pressure stays put at 5 kg/cm2 even with Vtec engaged. Just have to hunt down a minor coolant leak in the vicinity of the two hoses connecting the motor to the alum pipes.

https://www.facebook.com/video.php?v=10206860246797002

Congratz Joe, a testament of perseverance.
Now go out and enjoy it

 

[nsxspdfreak]

Congratz Joe, a testament of perseverance.
Now go out and enjoy it

Thanks and I plan on it!