Why's and Why-not's of Dry Sump Oil System

[Zanardi 50]

Pardon me for asking guys, but what are the advantages (and disadvantages) of a dry-sump system vs. conventional ones?
And to be more specific, why you guys think Honda engineers didn't give the NSX such treatment whereas Ferrari swears by it?

 

[mdoan300]

Somebody correct me if I'm wrong, but:

A dry sump generally costs more and requires more oil capacity.

Futhermore, a dry sump uses pumps to suck oil from the heads, block, etc. and return it to the oil reservoir. A wet sump relies on gravity and because of that, your car (if it has a wet sump) may be more subceptible to oil starvation when driving at high speeds, high rpms, and/or high g-loads (i.e. oil gets stuck in the heads or in one corner of the oil pan).

Michael.


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1994 300ZX Twin Turbo

 

[BLACKL@BEL]

Porsche is another auto manufacturer that extensively uses dry-sump oil systems. I wish someone made a system for the nsx, boy would that be sweet.

 

[Jimbo]

A dry sump system does cost more but...

1. Since there's no reason to have a deep oil pan the engine can often be positioned lower in the vehicle.

2. There's no risk of the oil pickup becoming uncovered in high-g continual cornering.

3. The oil reservoir can be larger.

4. The oil pump is external and can be of larger flow capacity.

5. You don't have a big pool of oil in the vicinity of the crankshaft and rods. This splashing of oil down there can cut power. It's possible to gain HP.

I'm surprised that since so many here track there car and look for every possible benefit, that there's not more discussion about this.

-Jim



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1992 NSX Red/Blk 5 spd #0330
1991 NSX Blk/Blk Auto #3070 (Sold)
1974 Vette 454 4 spd Wht/Blk
http://homepage.mac.com/jimanders/PhotoAlbum1.html

 

[blurr]

Is accusump the same thing? I believe Comptech recommeded one be installed on the Flamemobile after the last engine failure during high G turns.

 

[Andrie Hartanto]

Accusump is not the same. I have accusump in my BMW race car, and just installed one in my NSX as well. Haven't test it in the NSX yet to see if it work well. Will keep you guys updated on that.

Accusump is basically oil accumulator that reserve the oil in the tank, and only supply needed oil if pressure drops below normal.

[This message has been edited by Andrie Hartanto (edited 19 August 2002).]

 

[Zanardi 50]

So how difficult would it be to convert the NSX into a dry sump system, from an engineering standpoint? Any techheads would like to answer this Q ?

 

[Larry Bastanza]

Guys,

I have had extensive experience with Porsche's and their dry sump systems so I will fill you in on what I know.

As many may realize Porsche's are a boxer engine design. With that in mind, there is really no "oil pan" per say. Jimbo's point about the crankshaft is exactly correct, in that when the crank/rods are moving through a "bath" of oil it robs HP.

In the boxer engine, without an oil pan, this type of system has hugh performance advantages, probably more then an engine with a oil pan, like the NSX. However there is still some gains to be had.

The "Dry Sump" system uses two oil pumps. One is a "scavenge pump" and one is a "pressure pump". The scavange pump pulls oil out of the crankcase and sends it to a holding tank. The purpose of the holding tanks is to let the oil settle and remove all air bubbles. The output of the tank is then a perfectly solid flow of oil to the pressure pump that pumps the oil to the bearing, heads etc.

Yes, this system holds 13 qt's! Makes for a pretty $$ oil change sometimes. But... since, in the case of a 911 engine, it is air cooled, the oil plays more of a role in cooling then a water cooled engine.

Doing this to an NSX motor is definately doable, but it will take some engineering, packaging, probably a better oil cooler, add a tank, etc. Last time I looked there is not a lot a free space in an NSX engine bay.

I had a discussion with Andrew, who is the head mechanic for RealTime racing, about this topic at the Memorial Day NSXCA NE event. The reason they did not do it, is because they would incur a wieght penalty for the increased horepower. Since on the street we have no "rules" there would be some tangible gains although I cannot begin the quantify them.

This system does also cure high G oil starvation. Oh, this oil pump does not have to be external. Porsche engines have a tandem pump in the lower section of the crankcase.

The challange with that is if you have an oil pressure problem, the whole engine must be torn down to get to the pumps. The NSX engine "wet sumped" is easier to get to the oil pump. As many who have overrev'd already know.

HTH,
LarryB

 

[Lud]

Jimbo and Larry covered most of the key issues pretty well I think.

I'd like to redirect a little more from theory to practical application. Andrie hit on this when he said he installed an Accusump.

It's not really practical to convert to a dry sump on an NSX, though it has been done. As Larry pointed out, packaging / routing stuff is a bit of a design challange.

Step back first and figure out what your goal is. On an NSX, you are only doing it for lubrication purposes - it would be REALLY impractical to try and lower the engine (and thus CG). That is done during the design of a car, not in your garage after the fact!

An Accusump system will provide all the lubrication you need under as extreme racing conditions as you are likely to see in your NSX. Comptech recommends Accuspump for that application and the Realtime #42 NSX racecar has used it for years.

Accusump is basically an accumulator tank in parallel with the regular oil system that stores oil and delivers it as needed under pressure during conditions that normally cause loss of or decrease in oil pressure from the pump. In the NSX this would be sustained high-G driving. It can also act as a pre-oiler for the engine on startup.

 

[Lud]

This is one of the Accusump models:

Their website is http://www.accusump.com