Memphomaniac

I have an 06 Z with about 1500 miles on a new engine. I drive in HPDE events, and my previous engine seized due to low oil pressure while driving on the track. So, I have a 2012 engine now, and my only upgrades are the Lingenfelter modded oil tank (adds 3 quarts of capacity), and the Aviaid tank insert. So, I am now using 11 quarts of Mobil 1 0W-40, and I check the oil level often throughout the day.

I built a data logger and installed a fast-responding oil pressure sensor. Essentially, I did everything "Dreamin" did in this post. I was attempting to avoid an issue which I thought was from oil starvation in high-G turns. I didn't want to see the same thing happen again.

I have my data logger set up to monitor the oil pressure on the new AEM sensor at a very fast rate (around 200 Hz). I grab the lowest oil pressure it gives me in each 200 ms period (5Hz), and write the data to a micro SD card file, along with CANbus RPM, speed, throttle position, and GPS lat/lon, X/Y accels, lap, gear, etc. Unfortunately, I have not been able to find the GMLAN PID codes for factory oil pressure and oil temperature. If the AEM sensor oil pressure ever drops below my threshold, I light a red LED I installed in the front of the data logger. My oil pressure threshold is a line that runs through 18PSI@2000 RPM and 24PSI@4000 RPM (GM-provided values).

So, this past weekend I am at the local track HPDE going down the 1/4 mile dragstrip section which is a part of the road course, and under WOT in 3rd then 4th gear, the LED illuminates So I back off some on acceleration and when I get back to the pits, I look at the data file to discover that the AEM oil pressure had dropped to 20 PSI at 6000 RPM This was in 3rd gear right before I shifted to 4th. After shifting to 4th and resuming WOT, the oil pressure had risen slightly during the shift, but went down again when I got back to WOT but not as low this time. The X accel was around 0.4 G in 3rd gear, and about 0.35 G in 4th gear.

I did try running down the straight at 6000 RPM in 3rd and 4th gear without being at WOT, and everything is fine, so the problem is not caused by high RPM alone. It might be caused by high longitudinal G alone, but it's hard to have high longitudinal G without high RPM.

My oil temperature was about 230 degrees max during the event.

I never had any issue at all in the turns, where I constantly hit 1.1 lateral G.

After I saw this, I had an instructor ride with me as passenger to keep an eye on both the red LED and the factory oil pressure gauge, and when I hit the acceleration point to make the LED come on again, he said the factory oil pressure gauge was rock solid at about 60 PSI.

I had tested the correlation between the factory oil pressure gauge and the AEM sensor value decoded by my data logger a lot on the street before going to the track, and it matched perfectly in all cases except for this one.

So, now I am wondering, it this difference expected due to the different locations of the oil pressure sensors, where the factory sensor is mounted at the top rear of the engine and my new AEM sensor is mounted in the front (option 3 as Dreamin points out in his post). If so, then maybe this is an indication of a combination of high RPM and high longitudinal G for over 10+ seconds.

Or am I seeing an issue which points to a need to upgrade the pump and oil pan. I've thought of doing the ARE mods, but that is expensive especially considering I don't race the car.

Bottom line: I need to figure out if this is a show-stopper, or if it is nothing to worry about. If anyone with experience with LS7 engines has any ideas of things for me to try to figure this out, I would appreciate your input.

Jawnathin

Sorry, no help on your particular issue, but you mentioned upgrading the pan. Aviaid has a windage tray as a part of their stage 2 program you may also want to consider if you find that the pan needs to be upgraded.

The ARE stuff is really nice and the real deal if you want to go all the way, but the Aviaid windage tray is an less expensive and viable alternative.

Nathanknorr

I had a similar problem with my car.. I am still not sure what happened. I took my car for a speed test.. (closed runway) I hit 292km/h and my oil pressure dropped to zero.. scared me enough to not make anymore runs. I am not too sure what to make of it.. this happened last year.. and it has not happened again since.

Mark2009

I'd consider it a show stopper as in not lighting up that LED anymore until I confirmed or denied it. Two inexperienced thoughts:

1. Move the sender to one of the locations on the rear of the block. Long shot, but at least you can confirm the pressure drop is system wide rather than a weird glitch at one point in the system (probably impossible since we're talking hydraulics, but I'd double-check just in case).

2. Call Katech about their upgraded oiling options... I think they have a better/blueprinted main pump and a 2nd scavenge pump (and I think a 2nd scavenge pump would have many additional benefits compared to windage try or a pan mod). They may also have data/experience on what you are seeing. Offhand it sounds like the pickup is getting uncovered during acceleration, but if that is the case you should see it big time in the lower gears. I suppose it could be pump cavitation as well, but you'd think you'd see that at high RPM without the G load (and you don't).

Admire your data-collection efforts

If this is widespread it could be huge

Memphomaniac

I added a data logger and was able to monitor the oil pressure from the factory sensor along with the new sensor, and the factory sensor was rock solid. This makes me believe that everything is OK, and that the new sensor is providing some misleading data.

Hercules Rockefeller

I haven't looked at this as closely as you have, but I think I've been having the same problem, and FWIW I'm running the Katech pump and the ARE stage II setup. My oil pressure frequently drops off at higher revs, and I've never been able to diagnose the cause. It's almost as if I get max oil pressure around 4k RPM, and with wide open throttle it's always lower. It could be cavitation under extreme RPM... but I just don't know. It sounds like you and I are seeing the exact same thing here. I also don't know if this is "normal" or not, but after a couple dozen track days my engine is now starting to burn oil and will probably need a full rebuild, so perhaps we need to figure this out.

Memphomaniac

I would expect burning oil would be a result of ring / cylinder wear. The oil pressure reduction is likely going to result in gradual bearing erosion and ultimately, failure. Are you actually seeing your oil pressure drop on the factory oil pressure gauge? If so, from what initial value to what lowest value? My factory gauge is staying high - I'm only seeing the drop in the oil pressure sensor I added.

SilveradoSS500

First off, get the ARE set up.

Your acceleration G load is reducing the pressure, which you know this. I'm not sure if there is any other reason besides the fact that you have a monster engine and the oil is getting sucked from the front to the back of the engine under straight line load.

The ARE set up will help with overall oil pressure and maybe run a thicker oil...

db2xpert

Can you try acceleration in first and second to see if you get the drop there too?
If there's a problem with straight line g-forces, the 1/4 mile guys with their DRs should be having problems and losing engines.

This is certainly something we need to know more about, and determine if there is really an issue.

Jawnathin

Okay, MAYBE a silly question, but I have to ask.

How would a drop in oil pressure be a result of straight line G forces?

IIRC, the typical starvation issue (long, high G, left hand turns) was due to the oil pump not being able to scavenge oil as its sloshed the side of the oil pan. It is unable to pump oil back into the sump at the rate the engine is consuming it. Additionally, the oil in the sump itself is also sloshed to the side, away from the pickup (which is on the bottom left of the tank). Eventually this, combined with the fact the oil pump can't replenish the dry sump quickly enough, it eventually starves and goes boom.

The LPE or enlarged tank is effective in helping solve this because you're adding another 2 to 3 quarts of oil, which in addition to giving the sump more oil (and thus time) until it runs out, it gives the oil pump more oil to try to scavenge, enhancing its ability to refill the dry sump tank. Possibly to the point where the sump may not go empty at all.

In the case of a straight line romp, how would both the oil pump not feed the dry sump, and how would the dry sump run so low to cause a drop in oil pressure? The LPE Tank is 9 quarts. I don't see how the engine could run through all 9 quarts and end up dry. The oil pan is only 2QTs. That oil has to go somewhere and surely some of it must be being scavenged by the oil pump and filling the dry sump tank again.

Not saying there isn't an issue here, just not sure how starvation would even be a problem in this scenario.

Mark2009

I think it is more accurately the inability of the oil to drain from the block down into the pan. Gravity side loads the oil and effectively pins it to one side of the engine internally... gravity is 1.0 g so if the side load (or acceleration load) is in excess of 1.0 g, then the gravity is defeated, the pan eventually runs dry because the oil is trapped in the upper parts of the engine.

Normally I wouldn't think you could pull in excess of 1.0 g on acceleration, at least for any extended time, but I guess you don't have to if there was something else going on to help delay the flow of oil back into the pan or to impede the scavenge pump. Hopefully this mystery can be solved.

Jawnathin

It would be interesting to know for sure what causes the inability to scavenge, but if oil is stuck in the block and unable to drain into the pan, then why would something like an ARE pan/Aviaid baffles be considered the solution?

Couldn't find much info from ARE about it, but Aviaid's description about the issue and the solution are in the following URLs. They pretty much blame the pan and pick up location in the dry sump.

http://aviaid.com/shopsite_sc/store/...s-z06-ls7.html

http://aviaid.com/pdfs/153-boltin_dr...6_corvette.pdf




And to bring all of this back to the topic for the OP... Aviaid does try to cover the acceleration/deceleration scenario. I'm somewhat skeptical that you could sustain a high enough acceleration Gs for such a long period of time to drain 9 Qts of oil in the dry sump tank and hamper the oil pumps scavenging to cause any sort of damage though.

Mark2009

My understanding is that they wouldn't be the solution (a sealed block with a 2 or 3 stage scavenge system that would actually put the bottom end under vacuum would be the solution), but by reducing windage in the pan area and by 'scraping' the crank they keep a bit more oil in the pan to start with instead of (some of) it being whipped up into a froth in and around the crankshaft area.

Same thing for the tank insert... gets some of the air out of the oil which gets some of the air out of the system.

I've never thought about it before, but I guess if you had a see-thru window into the lower end of the block at high RPM it would look like a London fog in there... but the liquid particles would be oil vapor, not water vapor.

Edit: I looked at the links and see that they add some baffling too, so that will help contain what does make it back into the pan, but I think the primary problem is oil being retained in the upper parts of the engine. I read that the GM LS block does not have a particularly well-engineered oil distribution system where the lower end bearings are the last to get fed, which can cause issues during marginal operation as the OP may be experiencing (there is a Warhawk interview somewhere that talks about this).

Edit II: Linkypoo to the Warhawk article: http://www.gmhightechperformance.com...k_ls7x_design/
.

olddragger

look to the ls9?
The '09 ZR1 upgrades are
1. to increase the system capacity to 10.75 qt. using a larger reservoir tank
2. retaining the 2 stage gearotor crank snout driven pump but increasing the volume and flow out put 25%
3. changing to a water/oil engine oil cooler located on the driver side of the pan.
4. slight pan improvements for better scavenging
5. retains the same PCV system. ( this can be a problem with the ls7 engine)
6. runs a higher system pressure

Mark2009

Bandaids.


Not that I have an opinion on the matter

olddragger

lol---

old news i know but this sure is pretty:
http://www.daileyengineering.com/20-...0PHOTO%201.jpg