Semi in depth gauge info

[sledneck07]

Disclaimer This is what my 1991 4.0l runs at your engine my be different depanding upon driving habbits, mileage and verious other factors. Also this info is accurte for all gas 1990 to 1995 RBV to the best of my knowledge.

EXPLAINATION I've noticed alot of posts about what the engine temp and oil psi should be at and replys turning into a run around and bi*ch fest. I always put a set of mechanical gauges in when i get a different truck and think they are worth every penny as the factory ones are inaccurate (hence dummy gauge (I highly recomend picking up a set (I use sun pro gauges and never had a problem))). Even though it may in the normal range your readings could be way high or low.

FACTS
ENGINE TEMP Your engine is the most efficinet at 210* as that is what it is built to run at. Your temp reading will very where your sending unit is located. the closer to the radiator outlet the cooler the reading because of the incomming water was cooled by the radiator. The closer to the inlet the warmer the reading will be, because all that coolant just ran through the heads and block and is headed into the radiator to be cooled.
-Your coolant temp will go up during accerlation (my 4.0l usally goes to 230* other engines my very from that) due to the added heat being produced. Once your going a steady speed you should be running about 190*-210*.

OIL PRESSURE Your engine oil press. Should run at 40-60 PSI at 2000 RPM. When your engine is cold it will run at a higher oil pressure because the oil is cool and will be thicker than it is warm, and the pressure will be lower when your engine is warm. Im usally at 45 to 50 PSI with a warm engine and steady RPM. At idle with a warm engine your pressure my drop down to 20 PSI but that is fine, but if your running down the highway and your pressure drops below 40 PSI you have a problem. A spun bering, bad bering and something else could be the reason for poor pressure (but before jumping into and answer and digging in go and get another guage and test it ( a $20 repair is better than a $200+ repair and end up having a bad oil pressure))

 

[Beef52751]

ENGINE TEMP Your engine is the most efficinet at 210* as that is what it is built to run at.

Where did you get this info???

 

[sledneck07]

back in high school from auto class... at that time there was a rumor that they were trying to bump it up to 230* but had to figure out what type of materials it would take to withstand that temp without warping or cracking. we were taught that the warmer the combustion area the fuel was burnt more compleatly thus lower emissions and better fuel economy.

 

[Will]

You need to go back and give your shop teacher a wedgie. He's obviously the other type of person your sig refers to.

The point of an EGR is to lower the combustion temperature to reduce NOx. A warmer combustion area increases the chances of detonation. Most of the cooling efforts of an engine are focused around the combustion chamber. You want to keep those cool.

But you have water condensing in your oil and you have to keep the temp--the actual temp--hot enough to turn it to steam and evacuate it through the PCV. With that in mind, the clearances of the engine are designed to run at those temps. Whatever the gauge says, it doesn't mean that's what the inside of the crankcase sees. All engines shed their heat differently and you should use the thermostat that came with your engine and ignore the actual temperature gauge reading if you install an aftermarket gauge. Just get used to the normal range that you see when you first install it, and don't try to force it into some ideal range.

I can assure you--seeing less than 40psi oil pressure does not mean you spun a cam bearing or something. The rule of thumb of 10psi per 1,000rpm is more normal for a used engine. 6-7psi at idle and 25psi at cruise is okay. If you can't take seeing your gauge dip that far, hook the idiot light back up and throw the gauge away.

Don't install gauges to keep an eye on things unless you really understand what you are seeing. It will just stress you out. A 5psi idiot light is perfectly adequate to protect your engine. A worn engine has a lot less oil pressure than a new one, but is just fine. I can tell by the way my engine sounds, smells, runs and the occasional look at the belts how it is doing. You will see wetness at the waterpump weep hole before the gauge shows you anything. In fact, the gauge is only a delayed idiot light. If it does show you something that failed, it will be pegged. I don't need to know that I am going up a hill because my temp has risen. I can see that by looking out the window.

 

[Beef52751]

everything i have seen is lower water temp and higher oil temp make more power BUT these are race engines that we are squeezing power out of not your DD. So i agree with Will, Give your shop teacher a wedgie and leave your gauges alone

 

[copternadley]

Disclaimer This is what my 1991 4.0l runs at your engine my be different depanding upon driving habbits, mileage and verious other factors. Also this info is accurte for all gas 1990 to 1995 RBV to the best of my knowledge.

EXPLAINATION I've noticed alot of posts about what the engine temp and oil psi should be at and replys turning into a run around and bi*ch fest. I always put a set of mechanical gauges in when i get a different truck and think they are worth every penny as the factory ones are inaccurate (hence dummy gauge (I highly recomend picking up a set (I use sun pro gauges and never had a problem))). Even though it may in the normal range your readings could be way high or low.

FACTS
ENGINE TEMP Your engine is the most efficinet at 210* as that is what it is built to run at. Your temp reading will very where your sending unit is located. the closer to the radiator outlet the cooler the reading because of the incomming water was cooled by the radiator. The closer to the inlet the warmer the reading will be, because all that coolant just ran through the heads and block and is headed into the radiator to be cooled.
-Your coolant temp will go up during accerlation (my 4.0l usally goes to 230* other engines my very from that) due to the added heat being produced. Once your going a steady speed you should be running about 190*-210*.

OIL PRESSURE Your engine oil press. Should run at 40-60 PSI at 2000 RPM. When your engine is cold it will run at a higher oil pressure because the oil is cool and will be thicker than it is warm, and the pressure will be lower when your engine is warm. Im usally at 45 to 50 PSI with a warm engine and steady RPM. At idle with a warm engine your pressure my drop down to 20 PSI but that is fine, but if your running down the highway and your pressure drops below 40 PSI you have a problem. A spun bering, bad bering and something else could be the reason for poor pressure (but before jumping into and answer and digging in go and get another guage and test it ( a $20 repair is better than a $200+ repair and end up having a bad oil pressure))

Nice information. I've read a lot of it and I've got some lessons on it.

 

[sledneck07]

thanks just trying to help some people out a lil bit

 

[sledneck07]

and hence my disclamier