Just how much more power comes from dry sumping?
Discussion
Just been reading the specs of two engines which it's pretty certain are otherwise identical,one with a wet sump and one with a proper dry sump system.The difference in bhp is some 30 or so horses in favour of the dry system and this is on an engine which when using the wet sump is at 420ish bhp.I'm really surprised that the dry sump could make this much difference,is it realistic to expect such gains from going to dry sump?
The engine is a flat plane 4.5L V8 by the way
The engine is a flat plane 4.5L V8 by the way
bob1179 said:
I didn't think that 'dry sumping' offered any gains in power.
I believe the whole point of fitting a dry sump was to allow efficient lubrication during hard acceleration, deceleration and cornering. Basically in a race engine.
I've often read of the reduced drag of the crank in a dry sump system allowing more power to be released,just didn't think it would be quite that muchI believe the whole point of fitting a dry sump was to allow efficient lubrication during hard acceleration, deceleration and cornering. Basically in a race engine.
I've had a dry sump car,but it was always dry sump so i could never compare before and after.I havent a clue really,hence my question.I wonder how much the reduced drag on the crank is offset by the fact you are driving a larger oil pump to push the oil around the engine though?
It's a curious one really and not one I'd really thought about. Were the intake and exhaust systems of the two engines the same? If one was for race/circuit work it may have less restrictions in the exhaust, ie. no catalytic converter, freer flowing exhaust and had better breathing? Do they have the same camshafts? It could even be down to the ECU's.
I've got to admit, I love stuff like this, I'm going to have to look further into it!
It's a curious one really and not one I'd really thought about. Were the intake and exhaust systems of the two engines the same? If one was for race/circuit work it may have less restrictions in the exhaust, ie. no catalytic converter, freer flowing exhaust and had better breathing? Do they have the same camshafts? It could even be down to the ECU's.
I've got to admit, I love stuff like this, I'm going to have to look further into it!
This is not a question you can expect a simple answer to because obviously it depends on how much power the crank drag was losing in the first place. That is a function of both the shape and size of the crank and rods, the amount of oil splash taking place and the rpm. You're likely to get better results with highly tuned high revving engines than larger ones in a lower state of tune but with similar horsepower.
However there's much more to it. With a dry sump system you can start exploring the effects of sump vacuum which improves piston ring seal. To make the most of that though you ideally use rings with lower radial tension which reduces parasitic friction.
So it's really a 3 stage process.
1) Going to dry sump reduces or eliminates crank drag from oil splash.
2) Efficient scavenge pumps reduce crankcase pressure.
3) Lower tension ring packs can then be used.
To make best use of all this on a specific engine requires testing and optimisation. Just bolting on a generic dry sump system with no other mods won't optimise anything although it will still show bhp improvements.
On a cooking 2 litre 4 pot running at lowish rpm with no major ring seal problems anyway because it isn't using a high compression ratio you might see 5 to 10 bhp.
On an 800 bhp drag V8 with every part of the engine at the bitter limit of reliability a fully developed oil and piston ring system could find 40 bhp or more.
With wet sump systems you can find some of the potential gains with crank knife edging and windage trays. It's a lot of work and money for the extra bhp though.
Dave Baker
Puma Race Engines
However there's much more to it. With a dry sump system you can start exploring the effects of sump vacuum which improves piston ring seal. To make the most of that though you ideally use rings with lower radial tension which reduces parasitic friction.
So it's really a 3 stage process.
1) Going to dry sump reduces or eliminates crank drag from oil splash.
2) Efficient scavenge pumps reduce crankcase pressure.
3) Lower tension ring packs can then be used.
To make best use of all this on a specific engine requires testing and optimisation. Just bolting on a generic dry sump system with no other mods won't optimise anything although it will still show bhp improvements.
On a cooking 2 litre 4 pot running at lowish rpm with no major ring seal problems anyway because it isn't using a high compression ratio you might see 5 to 10 bhp.
On an 800 bhp drag V8 with every part of the engine at the bitter limit of reliability a fully developed oil and piston ring system could find 40 bhp or more.
With wet sump systems you can find some of the potential gains with crank knife edging and windage trays. It's a lot of work and money for the extra bhp though.
Dave Baker
Puma Race Engines
The AJP Griff said:
bob1179 said:
I didn't think that 'dry sumping' offered any gains in power.
I believe the whole point of fitting a dry sump was to allow efficient lubrication during hard acceleration, deceleration and cornering. Basically in a race engine.
I've often read of the reduced drag of the crank in a dry sump system allowing more power to be released,just didn't think it would be quite that muchI believe the whole point of fitting a dry sump was to allow efficient lubrication during hard acceleration, deceleration and cornering. Basically in a race engine.
I've had a dry sump car,but it was always dry sump so i could never compare before and after.I havent a clue really,hence my question.
The fuel burning within the cylinders is not releasing any more energy, however due to reduced losses within the engine, more power is seen at the flywheel .... The engine is more efficient.
The real benifits, however, from a dry sump are the reduced height of the engine (a big gain in something using a CTR Honda motor for example), and therefore the opportunity to lower/move the CoG.
As important is the rewards for managing the oil through the engine to prevent starvation due to the oil "sloshing" about in a wet sump, and exposing the pickup.
The AJP Griff said:
Just read that the reduced crank case pressure also helps the power figures.As far as i'm aware both engines are identical in every respect.I'd use an electric pump myself if i went down this route,so the power sapping effect of the extra drag on the alternator should be minimal.
You don't magically reduce power requirements by running something from an electric motor driven by an alternator rather than a belt off the crank! In fact the extra conversion losses with the motor/alternator set up would waste more power than a simple drive belt.Mr2Mike said:
..You don't magically reduce power requirements by running something from an electric motor driven by an alternator rather than a belt off the crank! In fact the extra conversion losses with the motor/alternator set up would waste more power than a simple drive belt.
I realise the alternator output doesnt come free of energy losses,that kind of appreciation is connected to what i do for a living 
,but in my case the normal extra dry sump pump would have been gear driven through a series of gear wheels off the crank.I'm hard pushed to imagine the small current required to run an electric version would leach even greater power losses through the already running alternator.Anyway,like it or not i would have to use an electric pump!The AJP Griff said:
I realise the alternator output doesnt come free of energy losses,that kind of appreciation is connected to what i do for a living
Does the dry sump installation on the AJP utilise the existing oil pump for the pressure side, or does the external pump provide the pressure stage? If the later then the pump will require a very significant amount of power to drive it.Mr2Mike said:
Does the dry sump installation on the AJP utilise the existing oil pump for the pressure side, or does the external pump provide the pressure stage? If the later then the pump will require a very significant amount of power to drive it.
There are two versions of the AJP.The kind i am running is what is found in the Cerbera and has a wet sump with only one oil pump.The other kind is that found in the tuscan racers and it has a dry sump with two gear driven oil pumps.The Tuscan race engine would not fit in my chassis easily so if i were to convert my Cerbera type AJP to dry sump it would have to be with the electric pump set up.plasticman said:
If you use the factory AJP dry sump I doubt you will gain any more power infact I think you will have less !
I'm guessing your refering to the actual sump itself here Dave,rather than the inefficency of the gear driven pumps?I really liked the idea you showed me of converting the tuscan dry sump the way you had done.Have you had it in use yet?Edited by The AJP Griff on Monday 9th March 22:06
Mr2Mike said:
The AJP Griff said:
Just read that the reduced crank case pressure also helps the power figures.As far as i'm aware both engines are identical in every respect.I'd use an electric pump myself if i went down this route,so the power sapping effect of the extra drag on the alternator should be minimal.
You don't magically reduce power requirements by running something from an electric motor driven by an alternator rather than a belt off the crank! In fact the extra conversion losses with the motor/alternator set up would waste more power than a simple drive belt.For example if the oil pump motor is drawing 50amps @ 12v
And you fit a 25amp alternator.
The alternator will drop to battery voltage when current limit is exceeded (normally around 14.5v) and draw remaining power from the battery.
Assuming no other electrical Items in the system.
25amps @ 12v = 300w = 0.402bhp + losses gained from driving a smaller alternator.
Not much of a gain but still some.
to expand a bit on what "pumaracing" said.....
how much oil is sloshing around with the crankshaft is greatly variable with the size of the crank. A V12, for example could well entrain 2 pints of oil with it, but a smallish 4-cylinder won't gather quite as much.
2 pints of oil churning around at 7000rpm is easily going to use 25hp.
how much oil is sloshing around with the crankshaft is greatly variable with the size of the crank. A V12, for example could well entrain 2 pints of oil with it, but a smallish 4-cylinder won't gather quite as much.
2 pints of oil churning around at 7000rpm is easily going to use 25hp.
2woody said:
to expand a bit on what "pumaracing" said.....
how much oil is sloshing around with the crankshaft is greatly variable with the size of the crank. A V12, for example could well entrain 2 pints of oil with it, but a smallish 4-cylinder won't gather quite as much.
2 pints of oil churning around at 7000rpm is easily going to use 25hp.
Whether you use a wet sump or dry this will still happen. That is why cranks are knife edged and polished - to try to get the oil off them.how much oil is sloshing around with the crankshaft is greatly variable with the size of the crank. A V12, for example could well entrain 2 pints of oil with it, but a smallish 4-cylinder won't gather quite as much.
2 pints of oil churning around at 7000rpm is easily going to use 25hp.
A wet sump is only going to be draggy if the level put in is higher than it really ought to be to compensate for a lack of volume held in the wings that ought to be in it, or to help in a cornering starvation problem, or if the oil pressure is set higher than it needs to be to cope with frothing.
A properly controlled designed experiment would show this to be true.
Dry sumps are there to get the engine low to help handling and help the engine live by having a tank that deaerates the oil & keeps enough supplied when cornering.
Surely if you run your crank in a vaacum you will not get the resistance of moving it through air and balance out the lower pressure you would get in the wake of the crank and rods which must hold some excess oil .
Still done nothing with my dry sump yet Mike , been way to busy with bodywork as you will soon see !
Still done nothing with my dry sump yet Mike , been way to busy with bodywork as you will soon see !
Gassing Station | Engines & Drivetrain | Top of Page | What's New | My Stuff