Dry sumping 928
12-25-2011, 11:10 PM
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Dry sumping 928
I am keen to dry sump my supercharged 1981 4.7 during its up coming rebuild to fix the failed No 1 piston.
I've never had anything to do with dry sumping before, so I've been reading up on it.
I'm mostly driven to it to address the crankcase breathing issues.
It seems to me to have many advantages as well as extra HP. I'd like to fit the scavenge pump where the smog pump used to be, there's room there and a good location for both driving it and sump access. The oil tank is tricky for a non race street car, as I don't want to compromise any cabin space. I have been looking at the left rear corner where the huge rear muffler used to be. If the tail pipe went straight out the back, just clearing the battery box, it leaves quite a bit of room. Filling could be through the rear floor, or preferably through an extra fuel filler door to match the original right side one [suitably marked so it doesn't get filled at the fuel pump].It couldn't be a tall round cylinder as so many are but could have an internal vertical cylinder for return oil to be 'de-frothed'.
I like the idea of completely removing the oil filler neck and the pipe down into the sump, even the whole front section of the sump and all the hoses that become obsolete.
It would be great to hear some thoughts and advise on this.
Mike
I've never had anything to do with dry sumping before, so I've been reading up on it.
I'm mostly driven to it to address the crankcase breathing issues.
It seems to me to have many advantages as well as extra HP. I'd like to fit the scavenge pump where the smog pump used to be, there's room there and a good location for both driving it and sump access. The oil tank is tricky for a non race street car, as I don't want to compromise any cabin space. I have been looking at the left rear corner where the huge rear muffler used to be. If the tail pipe went straight out the back, just clearing the battery box, it leaves quite a bit of room. Filling could be through the rear floor, or preferably through an extra fuel filler door to match the original right side one [suitably marked so it doesn't get filled at the fuel pump].It couldn't be a tall round cylinder as so many are but could have an internal vertical cylinder for return oil to be 'de-frothed'.
I like the idea of completely removing the oil filler neck and the pipe down into the sump, even the whole front section of the sump and all the hoses that become obsolete.
It would be great to hear some thoughts and advise on this.
Mike
12-26-2011, 03:02 AM
#2
There is a few dry sump threads, it would be worthwhile to search for them. I am no expert but don't do it for the extra power because the type of dry sump you are talking about won't preform how you want. Also where are you going to put the tank if it is a street car?
12-26-2011, 10:36 AM
#3
Three Wheelin'
Your tank location sounds fine. Some quality plumbing work is called for obviously but that should work well if it's a large capacity with free flowing lines.
The big decision is to use the engine's pressure pump or not.
It's convenient to do that but you have to live with oil draining back into the tank overnight. That's one of the reasons I changed my system to use a modified stock pan.
There's just no reason for a fabbed pan, the engine is not going any lower and you don't have to have some purpose designed scavenges that suck out every drop, most of it will do.
The stock pan affords some cooling and capacity for drainback. I have that now and discarded my old fabbed pan and am happy as a clam.
Adding fitting to reach the pressure pump inlet on a stock pan is trickier than you might assume.
After doing that you may wonder if you should have used an external pressure pump. It would be a shame to not take advantage of the 928's nice internal oil pressure relief and cooler bypass, they are a niceley designed well made pieces.
Don't assume you can simply remove the smog pump and stuff in a dry sump pump and lines. I'ts been talked about but I've never seen it. Dry sumping is going to involve removing the engine and putting it in and out during mock ups.
BTW, I just re-read you post and you mentioned that you are contemplating this for crankcase ventilation, as though this were a simple fix for an oily intake. Sigh...another thread for the dry sump heap
The big decision is to use the engine's pressure pump or not.
It's convenient to do that but you have to live with oil draining back into the tank overnight. That's one of the reasons I changed my system to use a modified stock pan.
There's just no reason for a fabbed pan, the engine is not going any lower and you don't have to have some purpose designed scavenges that suck out every drop, most of it will do.
The stock pan affords some cooling and capacity for drainback. I have that now and discarded my old fabbed pan and am happy as a clam.
Adding fitting to reach the pressure pump inlet on a stock pan is trickier than you might assume.
After doing that you may wonder if you should have used an external pressure pump. It would be a shame to not take advantage of the 928's nice internal oil pressure relief and cooler bypass, they are a niceley designed well made pieces.
Don't assume you can simply remove the smog pump and stuff in a dry sump pump and lines. I'ts been talked about but I've never seen it. Dry sumping is going to involve removing the engine and putting it in and out during mock ups.
BTW, I just re-read you post and you mentioned that you are contemplating this for crankcase ventilation, as though this were a simple fix for an oily intake. Sigh...another thread for the dry sump heap
12-26-2011, 11:45 AM
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an often over looked location for a tank is in the fneders behind the front wheels. the windshield washer tank holds 2 gallons, and there is additional space that could be used. my measurements taken a few years ago showed you could get 3.6 gallons in a tank if you took up all of the possible space.
12-26-2011, 11:56 AM
#5
Race Director
since most of your concerns are breather-ventilation related.....research the new breather-separator that Greg Brown made......you still retain the wet sump, but this improved breather drastically reduces the amount of oil that is injected into the intake....
12-27-2011, 03:33 AM
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I've just read the very long thread started by Rob Edwards on dry sumping his heads with a scavenge pump mounted in place of the smog pump and driven by a 'V' belt. Interesting indeed. I think the cam boxes must be included in the scavenging.
I like your idea of still retaining the stock sump, especially for drain back and as you say, it helps with cooling also. I'm for using the original pressure pump and keeping the current oil coooler, which is mounted at the front. Don't like the in-tank ones since my first 928 leaked into the coolant a long way from home.
I've just been down to my 'man cave' with the said car on the hoist and a reasonable size tank will fit down in the left rear and if the fuel tank filler system is mimicked, there is plenty of space for a decent riser for return oil to be swirled down.
As you say, oil lines will require some planning.
I like your idea of still retaining the stock sump, especially for drain back and as you say, it helps with cooling also. I'm for using the original pressure pump and keeping the current oil coooler, which is mounted at the front. Don't like the in-tank ones since my first 928 leaked into the coolant a long way from home.
I've just been down to my 'man cave' with the said car on the hoist and a reasonable size tank will fit down in the left rear and if the fuel tank filler system is mimicked, there is plenty of space for a decent riser for return oil to be swirled down.
As you say, oil lines will require some planning.
Your tank location sounds fine. Some quality plumbing work is called for obviously but that should work well if it's a large capacity with free flowing lines.
The big decision is to use the engine's pressure pump or not.
It's convenient to do that but you have to live with oil draining back into the tank overnight. That's one of the reasons I changed my system to use a modified stock pan.
There's just no reason for a fabbed pan, the engine is not going any lower and you don't have to have some purpose designed scavenges that suck out every drop, most of it will do.
The stock pan affords some cooling and capacity for drainback. I have that now and discarded my old fabbed pan and am happy as a clam.
Adding fitting to reach the pressure pump inlet on a stock pan is trickier than you might assume.
After doing that you may wonder if you should have used an external pressure pump. It would be a shame to not take advantage of the 928's nice internal oil pressure relief and cooler bypass, they are a niceley designed well made pieces.
Don't assume you can simply remove the smog pump and stuff in a dry sump pump and lines. I'ts been talked about but I've never seen it. Dry sumping is going to involve removing the engine and putting it in and out during mock ups.
BTW, I just re-read you post and you mentioned that you are contemplating this for crankcase ventilation, as though this were a simple fix for an oily intake. Sigh...another thread for the dry sump heap
The big decision is to use the engine's pressure pump or not.
It's convenient to do that but you have to live with oil draining back into the tank overnight. That's one of the reasons I changed my system to use a modified stock pan.
There's just no reason for a fabbed pan, the engine is not going any lower and you don't have to have some purpose designed scavenges that suck out every drop, most of it will do.
The stock pan affords some cooling and capacity for drainback. I have that now and discarded my old fabbed pan and am happy as a clam.
Adding fitting to reach the pressure pump inlet on a stock pan is trickier than you might assume.
After doing that you may wonder if you should have used an external pressure pump. It would be a shame to not take advantage of the 928's nice internal oil pressure relief and cooler bypass, they are a niceley designed well made pieces.
Don't assume you can simply remove the smog pump and stuff in a dry sump pump and lines. I'ts been talked about but I've never seen it. Dry sumping is going to involve removing the engine and putting it in and out during mock ups.
BTW, I just re-read you post and you mentioned that you are contemplating this for crankcase ventilation, as though this were a simple fix for an oily intake. Sigh...another thread for the dry sump heap
12-27-2011, 03:40 AM
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I've not over looked that space, or the other side, as this car does't have cruise. Sure would shorten the hoses/lines. I've considered a top oil door AKA 911.
I won't do away with the washers though, as I've recently had a dead washer pump and it's horrible here with bright sun plus dust.
I run a home made catch can that vents into the air cleaner line, so nothing vents to atmosphere.
I won't do away with the washers though, as I've recently had a dead washer pump and it's horrible here with bright sun plus dust.
I run a home made catch can that vents into the air cleaner line, so nothing vents to atmosphere.
an often over looked location for a tank is in the fneders behind the front wheels. the windshield washer tank holds 2 gallons, and there is additional space that could be used. my measurements taken a few years ago showed you could get 3.6 gallons in a tank if you took up all of the possible space.
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12-27-2011, 07:27 AM
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A very interesting thread.
I've been contemplating similar system for my project car. Had the idea of mounting the tank in the front right fender, with top oil door, exactly like you said. Since my car will be mostly a racer, I won't need a huge washer tank, thought about just having the "intensive" one, it should hold enough water for a DE/trackday.
Also, I thought about ditching the AC and mounting drysump pump there instead.
Will be following this thread very closely, please provide as much info as you can.
I've been contemplating similar system for my project car. Had the idea of mounting the tank in the front right fender, with top oil door, exactly like you said. Since my car will be mostly a racer, I won't need a huge washer tank, thought about just having the "intensive" one, it should hold enough water for a DE/trackday.
Also, I thought about ditching the AC and mounting drysump pump there instead.
Will be following this thread very closely, please provide as much info as you can.
12-27-2011, 11:22 AM
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Actually - I'd say there is more tank room in the front fenders in front of the wheel - plenty still with clearance for the headlights and you can have a quite tall tank for defrothing. It is in a crunch zone so thats a factor perhaps, but plumbing is far easier keeping it all up front, of course both front/front fenders are options - there is little in the drivers side either - filler through the fender wall(s).
However I agree with others - it you are looking to solve crankcase breathing issues on a street car this is a very round-about, complicated, expensive way to do it.
Why not tackle the problem head on and just address the breathing issues. Lots of options - typically you can implement enough of a solution for a street car for well less than $1K and a few weekends work... the dry sump is a REAL project involving significant downtime & $$$ ...
Go with a Provent to start and swap the cam venting to direct crank venting.
Alan
However I agree with others - it you are looking to solve crankcase breathing issues on a street car this is a very round-about, complicated, expensive way to do it.
Why not tackle the problem head on and just address the breathing issues. Lots of options - typically you can implement enough of a solution for a street car for well less than $1K and a few weekends work... the dry sump is a REAL project involving significant downtime & $$$ ...
Go with a Provent to start and swap the cam venting to direct crank venting.
Alan
12-27-2011, 11:52 AM
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I have never dry sumped a 928, but I have done a couple of other cars. From those efforts there are a couple of things worth mentioning;
For street uses I think it pretty much a waste of time, energy, and money. For racing, it has benefits. Primarily, IMO, it does 2 things, it adds oil capacity, and it allows the oil to be "de-frothed" in its seperator. There are of course other side benefits of lesser returns, such as adding scavenging to other points in the engine besides the sump, and adding additional cooling.
On the down side you will end up with a lot more complexity to deal with, re-engineering the 928 oil system is not for the weak of heart, or weak of pocketbook IMO. There are a number of ways to get dry sump oiling wrong, I have found a couple myself...blocking off oil ports in the engine, changing out pressure relief springs and valves and the like, rerouting oil flow external to the engine, and similar but lesser understood internal oil flows and return paths as it may relate to under/over cooling and sub system lubrication are only the beginings.
In my other engine efforts I found the point of frothing my oil followed by a drop in oil pressure, occurred well above 6500 rpm. Unless you are straying into 6500-7000+ rpm a lot I would think that what Mike, Brian, and Alan are suggesting makes more sense than dry sumping a 928. And I would listen to them a lot more than me, I am at best an armchair racer...
For street uses I think it pretty much a waste of time, energy, and money. For racing, it has benefits. Primarily, IMO, it does 2 things, it adds oil capacity, and it allows the oil to be "de-frothed" in its seperator. There are of course other side benefits of lesser returns, such as adding scavenging to other points in the engine besides the sump, and adding additional cooling.
On the down side you will end up with a lot more complexity to deal with, re-engineering the 928 oil system is not for the weak of heart, or weak of pocketbook IMO. There are a number of ways to get dry sump oiling wrong, I have found a couple myself...blocking off oil ports in the engine, changing out pressure relief springs and valves and the like, rerouting oil flow external to the engine, and similar but lesser understood internal oil flows and return paths as it may relate to under/over cooling and sub system lubrication are only the beginings.
In my other engine efforts I found the point of frothing my oil followed by a drop in oil pressure, occurred well above 6500 rpm. Unless you are straying into 6500-7000+ rpm a lot I would think that what Mike, Brian, and Alan are suggesting makes more sense than dry sumping a 928. And I would listen to them a lot more than me, I am at best an armchair racer...
12-28-2011, 05:36 AM
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My guard front areas are full. rhs has the intercooler radiator and the lhs has the pod filter and alternator cooling pipe, which I added an intke air temp sensor. [pics].
My reasoning is definitely NOT breathing only. This is very much a project street car, although my wife likes to motorkana in it.
Many hours were spent on designing and building the intercooler system when I could have bought one for less but that's not the point. This one is mine and it works. I like that.
Same with my catch can, there's dozens out there to buy but I like to make stuff.
My reasoning is definitely NOT breathing only. This is very much a project street car, although my wife likes to motorkana in it.
Many hours were spent on designing and building the intercooler system when I could have bought one for less but that's not the point. This one is mine and it works. I like that.
Same with my catch can, there's dozens out there to buy but I like to make stuff.
Actually - I'd say there is more tank room in the front fenders in front of the wheel - plenty still with clearance for the headlights and you can have a quite tall tank for defrothing. It is in a crunch zone so thats a factor perhaps, but plumbing is far easier keeping it all up front, of course both front/front fenders are options - there is little in the drivers side either - filler through the fender wall(s).
However I agree with others - it you are looking to solve crankcase breathing issues on a street car this is a very round-about, complicated, expensive way to do it.
Why not tackle the problem head on and just address the breathing issues. Lots of options - typically you can implement enough of a solution for a street car for well less than $1K and a few weekends work... the dry sump is a REAL project involving significant downtime & $$$ ...
Go with a Provent to start and swap the cam venting to direct crank venting.
Alan
However I agree with others - it you are looking to solve crankcase breathing issues on a street car this is a very round-about, complicated, expensive way to do it.
Why not tackle the problem head on and just address the breathing issues. Lots of options - typically you can implement enough of a solution for a street car for well less than $1K and a few weekends work... the dry sump is a REAL project involving significant downtime & $$$ ...
Go with a Provent to start and swap the cam venting to direct crank venting.
Alan
12-28-2011, 05:54 AM
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Jim, I'm sure you 'speak with straight tongue', I have never done this before either, on any car and I may not even do it to this car. However, I'm now 9/10 retired and I have to remove and rebuild the motor, I have quite a few spare bits, a nice workshop and plenty of time.
It's a bit like 'shall I fit the 86.5 32v heads'? Well I have all the stuff and they make more sense than the 16v ones, so why not look at the options.
If it was my only car, or even my only 928, or I had kids at college and a mortgage, one would have to view it all differently.
Even if I had to pay someone to do it all, it would be very different but luckily I should only have to buy a scavenge pump, some hoses and a bit of aluminium.
The alternative could be to find a new passion, hell that might be expensive!
It's a bit like 'shall I fit the 86.5 32v heads'? Well I have all the stuff and they make more sense than the 16v ones, so why not look at the options.
If it was my only car, or even my only 928, or I had kids at college and a mortgage, one would have to view it all differently.
Even if I had to pay someone to do it all, it would be very different but luckily I should only have to buy a scavenge pump, some hoses and a bit of aluminium.
The alternative could be to find a new passion, hell that might be expensive!
I have never dry sumped a 928, but I have done a couple of other cars. From those efforts there are a couple of things worth mentioning;
For street uses I think it pretty much a waste of time, energy, and money. For racing, it has benefits. Primarily, IMO, it does 2 things, it adds oil capacity, and it allows the oil to be "de-frothed" in its seperator. There are of course other side benefits of lesser returns, such as adding scavenging to other points in the engine besides the sump, and adding additional cooling.
...
For street uses I think it pretty much a waste of time, energy, and money. For racing, it has benefits. Primarily, IMO, it does 2 things, it adds oil capacity, and it allows the oil to be "de-frothed" in its seperator. There are of course other side benefits of lesser returns, such as adding scavenging to other points in the engine besides the sump, and adding additional cooling.
...
12-28-2011, 11:35 AM
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Jim, I'm sure you 'speak with straight tongue', I have never done this before either, on any car and I may not even do it to this car. However, I'm now 9/10 retired and I have to remove and rebuild the motor, I have quite a few spare bits, a nice workshop and plenty of time.
It's a bit like 'shall I fit the 86.5 32v heads'? Well I have all the stuff and they make more sense than the 16v ones, so why not look at the options.
If it was my only car, or even my only 928, or I had kids at college and a mortgage, one would have to view it all differently.
Even if I had to pay someone to do it all, it would be very different but luckily I should only have to buy a scavenge pump, some hoses and a bit of aluminium.
The alternative could be to find a new passion, hell that might be expensive!
It's a bit like 'shall I fit the 86.5 32v heads'? Well I have all the stuff and they make more sense than the 16v ones, so why not look at the options.
If it was my only car, or even my only 928, or I had kids at college and a mortgage, one would have to view it all differently.
Even if I had to pay someone to do it all, it would be very different but luckily I should only have to buy a scavenge pump, some hoses and a bit of aluminium.
The alternative could be to find a new passion, hell that might be expensive!
I used stainless steel braided hoses (I do not recommend that in hindsight) and a basket full of AN-10 fittings, as well as an inline filter between the sump drain and the low pressure side of the pump. It took me several days to fabricate an oil tank that fits in front of a rear tire on my current car. It took me a couple of tries to get one that fits and has enough capacity.
I built the tank out of fiberglass over a lost foam buck as my other option was to buy a TIG and teach myself how to use it.....and that sounded like a lost cause as I am the world worst welder on less demanding materials than aluminum.
So, all told I have a couple of weeks invested, and about $2500 in parts and stuff...and I am not yet certain if I solved my original problems, or just covered them up with the dry sump. But, it looks impressive.....
12-28-2011, 12:28 PM
#14
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OK - I see you have been busy already stuffing the fenders!!...(Nice)
Obviously you can fab things up very nicely. So go for it if its basically for your fun and enjoyment & because you can!...
Do you think you can make the rear area of the front fenders work for a tank? - maybe just use the intensive washer tank for the washers?
I think you already know pretty much what to do - but I'd suggest scavenging the cam covers directly as well as the pan. See Rob Edward's/GB write up...
Alan
Obviously you can fab things up very nicely. So go for it if its basically for your fun and enjoyment & because you can!...
Do you think you can make the rear area of the front fenders work for a tank? - maybe just use the intensive washer tank for the washers?
I think you already know pretty much what to do - but I'd suggest scavenging the cam covers directly as well as the pan. See Rob Edward's/GB write up...
Alan
12-28-2011, 02:47 PM
#15
Nordschleife Master
There are a few things in this thread that need to be stated.
Your tank will need to be larger than the amount of oil you plan to use as it will need a de-frothing area.
Due to this, I doubt the fenders will be a suitable area.
You need to make sure that the oil flow is <10 ft per sec for the oil line going to the oil pressure pump. This means either a -16 (1" id) or -20 (1 1/4" ID) hose going to it. If you do not have this, well, you can ask Cheburator what happens.
a general rule of thumb is to take the original oil volume and add 50%. So if the original volume was 8 litres, you need a minimum of 12L now. And your resevior needs to be a max of around 60% full for de-aeration. So really you need a 5 gallon reservoir for the system, also consider a secondary tank of much smaller size for the breather to go through.
Not all pumps are made equally, I will only use Dailey Engineering pumps with the air oil separator on the back. This will help to control the aeration and ensure that you never go dry. Budget around $1500-2000 for a good pump.
Due to the points illustrated above, I dont see it being very practical for a street car. What I did for my street car was to install a vacuum pump designed specifically for crankcase vacuum. I then exit it to a home made air oil separator, which has a catch on the bottom. Off the catch is a small tube which is routed up to the 1-4 cam cover and attached to the forward port. This releases a small portion of the vacuum so as to prevent the vacuum from getting too high and to suck any removed oil back into the engine reducing the possibility of running the oil low. The system works very well, but I need to make one or two changes to it. Those will be happening soon. But the system is still working very well, and is working under boost (turbo). So if your car is a street car, I would recommend entertaining that idea over drysump.
Your tank will need to be larger than the amount of oil you plan to use as it will need a de-frothing area.
Due to this, I doubt the fenders will be a suitable area.
You need to make sure that the oil flow is <10 ft per sec for the oil line going to the oil pressure pump. This means either a -16 (1" id) or -20 (1 1/4" ID) hose going to it. If you do not have this, well, you can ask Cheburator what happens.
a general rule of thumb is to take the original oil volume and add 50%. So if the original volume was 8 litres, you need a minimum of 12L now. And your resevior needs to be a max of around 60% full for de-aeration. So really you need a 5 gallon reservoir for the system, also consider a secondary tank of much smaller size for the breather to go through.
Not all pumps are made equally, I will only use Dailey Engineering pumps with the air oil separator on the back. This will help to control the aeration and ensure that you never go dry. Budget around $1500-2000 for a good pump.
Due to the points illustrated above, I dont see it being very practical for a street car. What I did for my street car was to install a vacuum pump designed specifically for crankcase vacuum. I then exit it to a home made air oil separator, which has a catch on the bottom. Off the catch is a small tube which is routed up to the 1-4 cam cover and attached to the forward port. This releases a small portion of the vacuum so as to prevent the vacuum from getting too high and to suck any removed oil back into the engine reducing the possibility of running the oil low. The system works very well, but I need to make one or two changes to it. Those will be happening soon. But the system is still working very well, and is working under boost (turbo). So if your car is a street car, I would recommend entertaining that idea over drysump.