Dry Sump Power Loss

[Boston]

To teams running dry sumps: are you seeing any significant power losses? If you're not able to discuss this publicly, please contact me (John Tysman) at tysmanjo@msu.edu.

[Boston]

To teams running dry sumps: are you seeing any significant power losses? If you're not able to discuss this publicly, please contact me (John Tysman) at tysmanjo@msu.edu.

[Dave M]

yes. at some point the parasitic losses are greater if you have too many stages. We picked up power from the vacuum alone.

[John Stimpson]

A proper dry sump ougtta give you power, being the cranktrain doesn't need to spin in oil, and that crankcase vacuum tends to seat the rings better for improved sealing...keeping the combustion pressure where it should be...above the piston.

[KU_Racing]

an ls7 dry sump system takes about 25 hp to spin at the redline of that engine. Most of that power is made up, however, by the failry massive amount of vaccuum that that system pulls in the crankcase.

At worst, things should even out. At best, hope for another 2-3% power gain if your system is set up just right.

[John Stimpson]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by KU_Racing:
an ls7 dry sump system takes about 25 hp to spin at the redline of that engine. Most of that power is made up, however, by the failry massive amount of vaccuum that that system pulls in the crankcase.

At worst, things should even out. At best, hope for another 2-3% power gain if your system is set up just right. </div></BLOCKQUOTE>

Guess again... Talk to someone that has built Winston/Nextel cup engines, and ask them how much power would be lost if they switched to a wet sump.

Now, I haven't built or setup cup engines, but from the guys I've talked to that do/have, its in the order of magnitude of 100hp.

[VFR750R]

I doubt it would hurt more then 40hp, but there are a lot of things dependent on having a drysump. That means to race it, it would cost us so more to modify those parts to live 500miles without it.

We never experiment with wet sumps anymore, but I can tell you there is a difference in busch and cup pans as far as hp and they are both drysumped.

Drysump pumps don't take 25hp to run either. Not even close.

I was under the impression the LS7 system did not pull considerable vacuum. The system is just to shorten the pan and garuntee oil supply under hard cornering loads. I think getting seals to live at high vacuum for steet use would be a limiting factor, also the high parastic loss of the pump/gain at cruising rpm would probably hurt fuel economy even though it would be a power gain at high rpm.

[John Stimpson]

I might add that at 10,000rpm, a dry sump pump would have to require 13lb*ft of torque to turn, to consume 25hp.

HP=TQ*RPM/5252

[KU_Racing]

No disrespect to anyone, but this is a topic i know a little about. I just conducted a test at work for one of the teams that runs corvettes in Rolex. The engine they are using next season is an ls2 with production ls7 oiling hardware. Reading from the test data, the pump consumes 24.4 hp at peak rpm. Also remember that at 8,000 rpm, that pump provides in excess of 80 psi of oil pressure with a fairly high flow rate. 13 lbft does not seem like a lot for just a pump spinning dry, but if anything it seems low for a pump pushing a high enough volume to pressurize the oil system to 80 psi.

You would be surprised I think at the amount of horsepower that accessories consume on an engine. In another recent test, we tested a vortech blown 402 ls2, which made ~1050 hp at the flywheel on our dyno. The supercharger was tested in the same manner as the dry sump pump on the corvette engine, and it consumed in excess of 100 hp at peak boost. It is not unusual for a high powered drag car to pick up 20 whp by switching to an electonic water pump- thats roughly 25 hp at the crank.

[VFR750R]

A simple calculation for pump work shows that 20GPM (which is alot) and 80 psi is about 1.23hp for 80% efficency, which is not out of the question on a hydraulic pump. For it to take 24.4hp it would be roughly 5% efficient.

Now I'm not saying our pumps take 1.3 hp, but we've done similar friction studies and it's alot closer to 1.3 then 24.4.

RPM is not in the calculation, 8000rpm is only a consideration because the pump is pumping more at 8 then it would at a lower rpm.

Also, think about the heat input for the pump to consume 25hp. That hp has to go somewhere, most of it in the form of heat. Are you heating the oil through the pump a considerable amount?

Another sanity check is we prime our oil every weekend with a handheld electric drill. Usually it primes around 40psi or half of the 80 at roughly 5gpm. Scaling down the 25hp for the lower pump head and for flow rate, I get 3.125hp which no handheld drill has.