so i finally got my oil pressure and water temp sensors working. using a 0-5 bar VDO sender and a 1/8 NPT resistive thermocouple (took me a while to figure out which setting the mychron wanted for this sensor, the PT100 fyi).

oil pressure seems to be around 40-60 psi when running. what should the LOW alarm be set at? is there any reason for a HIGH alarm?

water temp is reading at the intake manifold next to the #4 runner near the flange where there used to be an unused stock coolant line. not sure what track temp is, just ran it in the garage. any suggestions for a HIGH alarm? i figure i could set a LOW alarm for knowing when the engine is up to temp and warmed up and the light will turn off. what should that low temp be?

thanks.

 

In for more info as well.

 

i was just told personally water at 200F for a warning, and oil at low 35psi.

 

I have my High for water set at 200F, its more of a "hey turn the fan on now" Then a "uho somethings going wrong"

I had my low for oil set at 30psi. And the high was something stupid high.

 

I have water set to 230F for high alarm. For oil pressure I set the alarm to go off only when oil pressure is less than 30psi AND engine speed is greater than 2.5K RPM. That way you don't have the stupid thing turn on every time the car is sitting at idle.

 

High water temp and low oil pressure are the only alarms needed for these 2 sensors. 220-230 is more or less the norm high setting for temp and 25-30 the range for low pressure.

my 0.02

 

210F high - coolant.. 25-30 low - oil.

 

Tyson,

Data acq Alarms are very subjective, depending on what you're trying to accomplish.

Oil pressure - My personal recommendation is to set it just a touch above what will cause engine damage, since most dont know what this is I typically use a value of half of the peak oil pressure, and as stated above us an RPM qualification to validate the alarm.

Water Temp - As also stated above it depends what you're trying to accomplish, is this a reminder to turn the fan on, or a hey dummy! you're cars going to asplode? Around 200 is probably a bit low.

My personal feelings are that alarms do not need to be flashing in the drivers face unless he needs to do something to turn them off or stop driving

 

My Water temp alarm is on full time, with the temp displayed at 284F

Must have something to do with my SPA gauge being broken, since it reads that even after sitting with the motor off for 2 months.

SPA makes a nice gauge, but there is NO cust service... (literally)

 

Call there and ask for Morgan, he should take care of you.

 

QUOTE i figure i could set a LOW alarm for knowing when the engine is up to temp and warmed up and the light will turn off. what should that low temp be? QUOTE



The temp value that turns on the fan switch might be a good place to start if you want to know when the motor is 100% warmed up, anyone here know what that temp should be?.....I suppose you could run the car with a test light (if you don't have a fan hooked up), and measure the water temp manually when the light turns on?

 

I decided to look up recommendations about temps and pressures for lubrication and cooling in one of my favorite books: "Four-Stroke Performance Tuning" by A. Graham Bell. Some info quoted from the book.

1. an engine should never be driven hard until the oil reaches 70 C (158 F)
2. ideal oil temperature is 95-110 C ( 203-230 F)
3. it (oil temp) can go as high as 130 C ( 266 F ) for short periods, but oil breakdown and excessive oxidation will take place above this temperature.
4. in a race engine, bearing failure is a possibility anytime oil temperature goes above 130 C ( 266 F).
5. I would only recommend and oil cooler if under hard driving conditions the oil is regularly in excess of 120 C ( 248 F)
6. Basically I want 5W-50 or 15W-50 grade oil (Mobil 1) at 95 -105 C (203-221 F)
7. I also fit an oil pressure switch, adjusted to 30-45 psi. I wire this to a 3in. stop/tail light mounted on the dash with a 21 watt lamp. If the light flashes on, low oil pressure is indicated (this is used to test sump baffling)
8. Personally I keep the oil fill level well below the full mark on the dipstick. First I check for oil surge with 1/2 litre less, then 1/4 less, etc.
9. Most cars operate at around 90 C (194 F) and most competition vehicles operate at even lower temperature , usually 70-75 C (158-167 F) (coolant temperature)
10. First, the system is pressurized to prevent boiling after the engine is turned off.
11. By pressurizing the system using a 14psi radiator cap the boiling point is raised tp approximately 125 C (257 F) at sea level.

 

Does he post sources or information on how he came to his conclusions in his book?
I normally run 280-290 oil temps on track. My oil analysis showed that in 300 miles (~115 on track) that my oil looked like it had 4200 daily driven miles on it.
I know I'm right on the cusp of oil failure, but 248 seems really low of a goal to me.

 

The OEM Honda thermostats open at 176F so I think that is where Honda considers the engine fully warmed up. That is also where the ECU stops adding fuel for warm up considerations.

 

good to know.

 

The conclusions in the book are based on engine dyno testing results and tear-downs on engines looking at rod bearings, etc. Seems very comprehensive, and lists properties of many racing and non-racing oils and their benefits and drawbacks. He was pretty clear on info about high oil temps. Lists example of cars that had run much higher than recommended temps with no apparent damage, so author seems very familiar with temperature issues from real race cars. I know of no better source on engine info for track use. It is not a tuning or how-to book. At 476 pages, more like a bible on engines. His book on forced induction is excellent also. Been in print since 1981 with last revised 3rd edition from 2006, which is a lot of history.