Low Oil Pressure Fuel Cut Off Switch
02-25-2013, 07:34 AM
#1
Three Wheelin'
Thread Starter
Low Oil Pressure Fuel Cut Off Switch
The 944's can sometimes suffer from low oil pressure leading to potential engine damage and often spun rod bearings.
What is the opinion of my Rennlist colleagues on fitting such a device to the oil pressure circuit? 12 psi is about 0.9 bar, oil pressure is always above this. I wonder if the car would have trouble cranking when the engine is really hot? The benefit is of course safety as well, although I thought the fuel pump was killed when the engine stopped anyway.
Opinions?
LONGACRE ELECTRIC FUEL PUMP CUT OFF SWITCH
ELECTRIC FUEL PUMP CUT OF SWITCH - Fitted into an engine's oil pressure circuit. The switch will cut power to the electric fuel pump in the event of a crash. Thus cutting the flow of fuel helping to prevent fires. It can also help to prevent engine damage as it will not allow the motor to start until the oil pressure has risen again. Switches at 12psi. Has 1/8NPT thread and is usually plumbed into the engine block or fitted with oil pressure switch using a T-Piece connector.
http://www.merlinmotorsport.co.uk/ma...SwitchBlue.jpg
What is the opinion of my Rennlist colleagues on fitting such a device to the oil pressure circuit? 12 psi is about 0.9 bar, oil pressure is always above this. I wonder if the car would have trouble cranking when the engine is really hot? The benefit is of course safety as well, although I thought the fuel pump was killed when the engine stopped anyway.
Opinions?
LONGACRE ELECTRIC FUEL PUMP CUT OFF SWITCH
ELECTRIC FUEL PUMP CUT OF SWITCH - Fitted into an engine's oil pressure circuit. The switch will cut power to the electric fuel pump in the event of a crash. Thus cutting the flow of fuel helping to prevent fires. It can also help to prevent engine damage as it will not allow the motor to start until the oil pressure has risen again. Switches at 12psi. Has 1/8NPT thread and is usually plumbed into the engine block or fitted with oil pressure switch using a T-Piece connector.
http://www.merlinmotorsport.co.uk/ma...SwitchBlue.jpg
02-25-2013, 09:23 AM
#3
Three Wheelin'
Thread Starter
Yes - that was one of my first thoughts too.
I haven't heard of anyone fitting these before, yet there must be a market for them or why would you bother making one?
I haven't heard of anyone fitting these before, yet there must be a market for them or why would you bother making one?
02-25-2013, 01:11 PM
#7
Rennlist Member
I think you'd have a hard time starting the car... there won't be any oil pressure, so it won't allow the fuel pump to run.
On the Aim and other digital dash boards, you can set conditional alarms - e.g. lights turn on when the oil pressure goes below 1 bar while the engine is over 3,000 RPM.
Otherwise, just wire up a BFOL - big freakin' oil light - and turn the engine off if it lights up.
On the Aim and other digital dash boards, you can set conditional alarms - e.g. lights turn on when the oil pressure goes below 1 bar while the engine is over 3,000 RPM.
Otherwise, just wire up a BFOL - big freakin' oil light - and turn the engine off if it lights up.
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02-25-2013, 01:21 PM
#8
Addict
Rennlist Member
Rennlist Member
I look at it as a driver decision, I'd hate to have the car shut off when I wasn't expecting it.
I have alarms for low pressure set with my MoTeC with emphasis on on-throttle pressures. I sometimes see short duration off-throttle drops in pressure. The shop tells me not to worry much about those.
I have alarms for low pressure set with my MoTeC with emphasis on on-throttle pressures. I sometimes see short duration off-throttle drops in pressure. The shop tells me not to worry much about those.
02-25-2013, 02:17 PM
#10
Three Wheelin'
The oil system challenges of the 944 family cars are well-known. For DE and racing applications, folks have been dealing with this for a really long time.
The ultimate solution involves converting to a dry sump system. I have seen many such cars through the years. Short of that, there are many different things folks have done to help lower the likelihood of problems. These include additional oil cooling, air/oil separators, custom oil pan baffles, accusumps, and a variety of other things. And of course rod bearing changes at regular intervals.
When I built my 951 engine back in 2000-2001 (chronicled in a couple of issues of Excellence magazine), I applied a variety of these techniques with guidance from one of the foremost builders of 944 family racing engines in the world: Jon Milledge.
During my many years of involvement with these cars and engines, I never heard of anyone considering an automatic shut-off system for low oil pressure situations. I think the reason why is that if you set a pressure high enough so that you can actually drive the car without interruptions, you get no benefit from the system.
If I were worried about my 944-family car's oiling system in track use, I would find engine experts with pro racing experience and design an approach based on their guidance.
In my case, I decided to get a car with a proper dry sump system that is far easier to service than a 944-family car: a Porsche 911.
As an aside, experts can differ widely on oil pressure warning. One of my friends believes that a user-adjustable pressure switch that drives a warning light can be very beneficial in 911 race car applications. His old company sold such a switch. And he is a very knowledgeable racing engineer who just retired from a famous US-based Porsche racing team. Well, they have been the most recent factory team.
My friend and engine builder, who raced in IMSA back in the day, believes that many failure scenarios occur so fast that warning lights aren't really much of a benefit. In his case, he uses his ears as a warning gauge. No earplugs and radio systems for him.
I decided on an adjustable switch and a big red light for my 911, mostly because my wife thought it could help her. And it did once when she had a major incident with all of the oil dumping out of the tank and resulting low oil pressure. Spinning off of the track and with all of the dirt and dried grass flying and the flash fire that ensued, she saw the red light and it reminded her to shut off the motor.
In any case, as you research oil system "improvements," I encourage you to leverage all of those that have gone before. Some may be active on these forums. Most are likely not.
I would still use Jon Milledge as my advisor and parts provider to the extent that he is still active with those cars.
The ultimate solution involves converting to a dry sump system. I have seen many such cars through the years. Short of that, there are many different things folks have done to help lower the likelihood of problems. These include additional oil cooling, air/oil separators, custom oil pan baffles, accusumps, and a variety of other things. And of course rod bearing changes at regular intervals.
When I built my 951 engine back in 2000-2001 (chronicled in a couple of issues of Excellence magazine), I applied a variety of these techniques with guidance from one of the foremost builders of 944 family racing engines in the world: Jon Milledge.
During my many years of involvement with these cars and engines, I never heard of anyone considering an automatic shut-off system for low oil pressure situations. I think the reason why is that if you set a pressure high enough so that you can actually drive the car without interruptions, you get no benefit from the system.
If I were worried about my 944-family car's oiling system in track use, I would find engine experts with pro racing experience and design an approach based on their guidance.
In my case, I decided to get a car with a proper dry sump system that is far easier to service than a 944-family car: a Porsche 911.
As an aside, experts can differ widely on oil pressure warning. One of my friends believes that a user-adjustable pressure switch that drives a warning light can be very beneficial in 911 race car applications. His old company sold such a switch. And he is a very knowledgeable racing engineer who just retired from a famous US-based Porsche racing team. Well, they have been the most recent factory team.
My friend and engine builder, who raced in IMSA back in the day, believes that many failure scenarios occur so fast that warning lights aren't really much of a benefit. In his case, he uses his ears as a warning gauge. No earplugs and radio systems for him.
I decided on an adjustable switch and a big red light for my 911, mostly because my wife thought it could help her. And it did once when she had a major incident with all of the oil dumping out of the tank and resulting low oil pressure. Spinning off of the track and with all of the dirt and dried grass flying and the flash fire that ensued, she saw the red light and it reminded her to shut off the motor.
In any case, as you research oil system "improvements," I encourage you to leverage all of those that have gone before. Some may be active on these forums. Most are likely not.
I would still use Jon Milledge as my advisor and parts provider to the extent that he is still active with those cars.
02-26-2013, 05:24 AM
#11
Three Wheelin'
Thread Starter
Thanks for the detailed reply. Just like everything in racing, if you want to do it right, you need to pay for it.
Once I have finished putting my kids through private schooling I might then get my gt3!
Once I have finished putting my kids through private schooling I might then get my gt3!
02-26-2013, 07:11 AM
#12
Rennlist Member
I wonder how much room you'd have to run a dry sump with the supercharger on there Eric?
02-26-2013, 09:21 AM
#13
Three Wheelin'
And it did once when she had a major incident with all of the oil dumping out of the tank and resulting low oil pressure. Spinning off of the track and with all of the dirt and dried grass flying and the flash fire that ensued, she saw the red light and it reminded her to shut off the motor.
Where's Gary.....he needs to see this.
