bobmoore2

Dreamin did an excellent writeup in the C6-Z06 Discussion forum. Of course, the C6 Z06's have a dry sump, so the problem would probably be much worse for a non-Z06.

http://forums.corvetteforum.com/c6-z...hard-data.html

BrianCunningham

some pretty impressive data logging there!

wtknght1

You guys need to read all the stuff I went thru developing the LS3 for the track. Man, was that painful!!!!! And yep, turning left is the achilles heel of the LS engines. I'm hoping my new dry sump will solve the problems.

My current LS3 (with the bat-wing pan) is for sale by the way on this forums. Make me a decent offer and it's yours.

95jersey

OK, I read that post, and here is my question. Please help cure my ignorance.

Let's start with a wet sump explanation to set the stage. If you lack oil in the pickup part of the pan, you do not have oil flow through the pump and hence the lines that dump the oil back into the motor. There is no reservoir that holds extra oil in case the pump is not supplied, so hence you have a moment of low to no oil pressure and what happens next we all know.

But in dry sump, even if the pick up in the pan doesn't have an oil supply for a few moments, the canister from where the oil is pumped back into the motor has a supply of SEVERAL quarts on tap at any given moment. I have heard arguments about some of the oil being "frothy" or "airated" in the canister. But I though the WHOLE point of a dry sump is that an oil starvation issue due to G load does not effect the sump because there is such a large reserve of oil to negate the lack of oil at the pickup for several seconds (let alone a 1/2 second).

So while his oil starvation data is good, wouldn't the fact that there is enough reserve oil in the canaster negate a momentary lack of oil supply in the system?

AU N EGL

many of the LS7s oiling issues were not in high speed left sweepers, but under very hard braking.

the Oil was staying UP in the heads and not draining back to the pan or sump.

IIRC is why GM redesigned the dry sump or recommended the LPE or ARE dry sump kits

63Corvette

So..................is an unmodified C5 Z06 (batwing) better or worse than a dry-sump C6 Z06 for track use only.....and will addition of an Accusump ensure the engine lives during track days (RACING on a roadrace track with sticky tires)?

wtknght1

Don't confuse and accusump with a dry sump. An accusump is a pressurized container that holds oil that feeds into the pan/pickup in case of low oil pressure.

A dry sump is a separate container (lots of oil) that has a line feeding directly into the pump...so there's no loss of pressure (in theory). The pan has pick up tubes that collect the oil and return it to the separate container.

The benefit of the dry sump is that there's no oil in the pan that the crank can pass thru (called windage losses).

A C5 LS6 engine is bulletproof. It just doesn't have that extra 100 HP that the C6 does. Unless you're competitive racing against monster engines, the LS6 is a superb engine and will last forever. You don't need an accusump on an LS6...although many people use them. I put over 25K racing miles on 2 LS6 engines with no failures.

63Corvette

Thanks Chris!!! I race a 63 with an Accusump (cause a dry sump is illegal) so I know the difference. However, I was asking about my streetcar (04 Z06) so I am VERY glad to read your analysis!!!


"A C5 LS6 engine is bulletproof. the LS6 is a superb engine and will last forever. You don't need an accusump on an LS6...although many people use them. I put over 25K racing miles on 2 LS6 engines with no failures."

wtknght1

Sorry, wasn't trying to insult anyone.

You won't have any issues out of your LS6. Depending on the track, I'd run mine up to 7200 and I've heard of folks setting their limiter at 7500!!!!! It's not good on the valve springs, but they run. I think my normal shift points were 6500-6800 and I had no issues at all.

GrantB

I have averaged about 1.08 gee on for slightly over 7 seconds turning left and slightly over 6 seconds turning right without any indicated loss of oil pressure in my C5. This is running 7.0 to 7.5 quarts of oil (I generally try to keep it one quart over). Of course this was on street tires, not Hoosiers, and no Accusump. Once my new motor is in the car (I lost my current one to det) I'll log oil pressure with HPTuners.

I'm trying to develop something for the two-piece batwing pans that might give them quite a bit more resistance to starvation.

bobmoore2

I've got the same question.

So if Dreamin has a drysump, which has a large reservoir of oil to supply the engine, then I would think it should not be affected by G load. What was causing his oil pressure drops in long high-G left turns? Did the canister tank run out of oil occasionally, maybe because high Gs exposed the pump pickups in the pan? Or were high Gs pushing the oil in the canister tank away from the pump pickup in the canister? Or a combination of both?

Does an accusump overcome all this by using air pressure to push the oil out of the accumulater tank?

GrantB

Yes, it is impossible for an Accusump to 'starve' unless its empty. They can be mounted in any orientation, so are more or less immune to acceleration. Oil in a dry sump tank still relies on gravity to feed the pump, so if it gets low it can starve.

Any idea how often the Accusumps activate on the fastest T1 cars?

By the way, I loaned my old blown shortblock to Ishihara-Johnson Crank Scrapers. They are making a scraper to fit LSx motors. If it works, it should remove oil from the windage cloud and return it to the sump, lower oil temps a bit and give a tiny bump in power. They also thought there were gains to be had with a modified windage tray.

AU N EGL

What year was the LS7? IIRC late 2008 and for 2009 was when the dry sump tank was redesigned. and or recommended the LPE or ARE tank be installed.

anyone with a 2008 LS7 should change their dry sump tank. Again it was not so much the high speed sweepers that our friends at Chevy told us, but under very hard braking the oil was staying up in the heads and not draining back to the pan and tank for pick up.

They even recommended the LPE tank as it was less expensive the the Chevy replacement tank.

NOSLO6

I've followed your past posts on this issue with great interest, including GM's high $ bat wing pan offering.

For us non-Z06 LS3 folks, is adding an Accusump a suitable fix for this problem (assume no class rules to contend with)? Do folks feel the bat wing pan alone is enough?

GrantB

Dreamin's results clearly show starvation in left-hand turns, though I don't know how hard he was braking.

What I don't understand is why GM would bother with such a terrible dry sump system. > 1.0 gee for 4 seconds isn't much, and there as wet-sump systems which work flawlessly in road racing competion (e.g., the gen 4 Viper's swinging pickup).

AU N EGL

BEAN Counters


at the NCM Road America HPDE least year, two instructors blew LS7s. Both engines were replaced at BG.

EvilBoffin

Is this concluding that the 'redesigned' OEM dry sump system on the '09's is not worth BEANS as well?

I believe it has a 10.5 quart capacity - right?

Reason I ask is - I'm considering the purchase of a 2010 Grand Sport (LS3) manual coupe, which has the Z06 dry sump. I will be very disappointed if it's not any better for track use then a wet sump LS3 - that was the whole point ...

wtknght1

Oh we can run an accusump... but Mike Tracy was running both his accusump and the bat-wing pan at the runoffs at heartland park and we all saw what happened. My car was the ONLY LS3 to complete the weekend. I started the race with 2 quarts over, but looking at the data, by lap 14, the pressure vs. rpms were getting dicey. Co-incidentally, that's when Tracy blew his up.

Personally, I don't think the accusumps can act quickly enough...and are generally speaking a waste of time, money and weight. Neither of my LS6 engines had an accusump and I had no issues. Others who ran the sumps, had problems. I won't use one.

The bat-pan on mine seems to work pretty well. I'm not sure what they changed from my prototype to the actual production version, but I don't think they are the same. The DRY sump is definitely the way to go though with the LS3 engine.

And, the LS3 is just fine with stock suspension, tires, etc. It was designed to handle up to 1.2 Gs (spikes) and I think the GM guys said 1.1 sustained Gs with no issues. But, when you add racing tires, suspension and sustained Gs of 1.6-1.9, you'll need either the bat-wing pan or a dry sump. And right hand turns aren't the issue either...just when turning left.

I would not run an LS3 on track without at least the bat-wing pan. Again, my LS3 with the bat-wing is still for sale if anyone is interested.

wtknght1

Bingo!!! We have a winner!!!

fatbillybob

Generally speaking I don't see how an accursump would help because they can dump their qt of oil in less than a second. So what do you do with sustained g's? You are still toast. Even when running 1.2qts over you get a frothy foamy windage fog that can decrease oiling efficiency to something below proper street oil levels. This is a complicated problem. I would think that the LS7 and LS3 fix could be had with a stock LS7 drysump and larger properly shaped oil tank. If GM says on braking the oil is collecting and not draining as fast as needed then the solution is more capacity for that time the oil is trapped. If the gravity feed oil pump is sucking air from the tank while scavanging pump is doing what it can in the sump then sometimes changing the oil tank shape to pool oil in the tank will help also as would extra internal tank baffling to break out the air if there is alot of froth. What that means to me is a big oil tank with lots of baffles and funneling into the pickup tube area.