Thread: turbo timer v egt gauge

Here's some interesting reading on "Diesel vs Gasoline Turbo Design ":

WC Engineering : Diesel vs. Gasoline Turbo Design

Turbo timers are more critical on petrol engines. There may be legal implications related to leaving a vehicle unattended while idling. The vehicle security system needs to also be "timer" aware.

While EGTs and turbos are related they have little in common when considering cooling before shut down. An EGT gauge reading is most relative to combustion gas ratios (stoichometric ratio). High and low EGT is a direct product of fuel air ratios and depending where the probe is located wont give you any useable information except that the reading is higher under throttle.
Where and why will you locate your probe and what will it tell you the driver in the cabin? Unless you are capable of modifying your own ECU or fuel pump settings, the answer is nothing, why bother, it is as the factory made it.

Ball and roller bearings work on the same princible as solid bearings. They all run on a film of oil. Take away the oil and they die, they are simply capable of higher speeds and loads because of their many points of contact, reducing friction and less heat build up. The problem is heat and oil flow on shut down, after high speed the turbo housing can be glowing, if shut down too soon the compressor will stop just as it would after slower running, it will not still spin at 20000rpm as stated. The excess heat cooks the oil left in the turbo and creates all manor of soot and which then causes the bearing failure, due lack of oil or impurities.

An EGT gauge wont save any of this.

Originally Posted by strangy

While EGTs and turbos are related they have little in common when considering cooling before shut down. An EGT gauge reading is most relative to combustion gas ratios (stoichometric ratio). High and low EGT is a direct product of fuel air ratios and depending where the probe is located wont give you any useable information except that the reading is higher under throttle.
Where and why will you locate your probe and what will it tell you the driver in the cabin? Unless you are capable of modifying your own ECU or fuel pump settings, the answer is nothing, why bother, it is as the factory made it.

Ball and roller bearings work on the same princible as solid bearings. They all run on a film of oil. Take away the oil and they die, they are simply capable of higher speeds and loads because of their many points of contact, reducing friction and less heat build up. The problem is heat and oil flow on shut down, after high speed the turbo housing can be glowing, if shut down too soon the compressor will stop just as it would after slower running, it will not still spin at 20000rpm as stated. The excess heat cooks the oil left in the turbo and creates all manor of soot and which then causes the bearing failure, due lack of oil or impurities.

An EGT gauge wont save any of this.

Quote: "Ball and roller bearings work on the same princible as solid bearings. They all run on a film of oil."

Wrong ball bearings run metal to metal, that is why they are hardened, if you beleive that ball or roller bearings do not have contact while moving, then try this, put some graphite powder in the lube and the bearings will eventually sieze, because the balls dont have clearances like a slipper bearing or bush and the graphite particles will adhere to the balls and cause them to seize, clearances in ball bearings are measured in microns, if they were running on a film of oil how do you supply the pressure to the oil to maintain the clearance, ball bearings are not pressure fed, but are lubed by splash, bath or spray.
So your saying that a turbine spinning at 20,000+rpm will stop spinning at the same time as a turbine spinning at 1000rpm, when the engine oil pressure supplying the bearings in the turbo ceases, any oil in the turbo drains back into the sump, most of what you said is wrong, the amount of soot produced by the heat of the turbo is miniscule compared to the combustion soot carried in the engine oil supply, it is that soot that eventually wears the engine parts and if you think ball and roller bearings have no metal to metal contact, then maybe you should look at some layshafts and mainshafts of gear boxes and see the grooves caused by your supposed non contact theory, Regards Frank.

Originally Posted by jmkoffice

Here's some interesting reading on "Diesel vs Gasoline Turbo Design ":

WC Engineering : Diesel vs. Gasoline Turbo Design

Turbo timers are more critical on petrol engines. There may be legal implications related to leaving a vehicle unattended while idling. The vehicle security system needs to also be "timer" aware.

That article is a crock.
Diesel turbos are much smaller than petrol turbos for the same engine capacity. My 3.9L Isuzu has a turbo which was originally fitted to a 1.8L petrol engine.
5-8psi is a waste of time.
The volume of exhaust gas is actually smaller than the same displacement petrol turning at the same RPM. This is due to the lower exhaust temp.


Turbos stop within seconds when the engine is shut off, this can be heard if you stick your ear nearby.
I don't shut my engine down until EGT's drop around 200 deg C preturbo. The only times idling is necessary is when I've just driven to the top of a hill.
Even pulling off the road from 100km/h the EGT's are low enough for immediate shutdown.

Originally Posted by UKLRO

Been looking for an EGT gauge for a while, where did you get your's?

This is perfect for your Disco ThermoGuard Instruments sure I wont mind you contacting him - he is Leo109 on this forum also.

HTH

LRH

Originally Posted by LRHybrid100

This is perfect for your Disco ThermoGuard Instruments sure I wont mind you contacting him - he is Leo109 on this forum also.

HTH

LRH

That's where I got mine, good bloke and knows his stuff.

Regardless of whether an EGT gauge will help with judging when the Turbo is spooled down enough etc. it will tell you if something unusual is happening in your engine.

Generally anything out of the norm == bad, good time to pull over and see wth is going on.

Originally Posted by Tank

Quote: "Ball and roller bearings work on the same princible as solid bearings. They all run on a film of oil."

Wrong ball bearings run metal to metal, that is why they are hardened, if you beleive that ball or roller bearings do not have contact while moving, then try this, put some graphite powder in the lube and the bearings will eventually sieze, because the balls dont have clearances like a slipper bearing or bush and the graphite particles will adhere to the balls and cause them to seize, clearances in ball bearings are measured in microns, if they were running on a film of oil how do you supply the pressure to the oil to maintain the clearance, ball bearings are not pressure fed, but are lubed by splash, bath or spray.
So your saying that a turbine spinning at 20,000+rpm will stop spinning at the same time as a turbine spinning at 1000rpm, when the engine oil pressure supplying the bearings in the turbo ceases, any oil in the turbo drains back into the sump, most of what you said is wrong, the amount of soot produced by the heat of the turbo is miniscule compared to the combustion soot carried in the engine oil supply, it is that soot that eventually wears the engine parts and if you think ball and roller bearings have no metal to metal contact, then maybe you should look at some layshafts and mainshafts of gear boxes and see the grooves caused by your supposed non contact theory, Regards Frank.

Frank, ball and roller bearings ar hardened to deal with the loads and speed they carry due to point contact. Talk to bearing manufacturers. your layshafts and mainshafts are damaged as are crankshafts and camshafts because despite an oil film parts wear and eventually the hardening goes and the softer metal wears faster hence damage. You are correct when you say they are splash fed, this is the benefit of ball and roller bearings to operate where an oil pump is generally impractical. Slipper type bearings found in crankshafts and camshafts operating in extreme environments are pressure fed otherwise they would fail if drip fed, yet many slipper bearings in industry are drip fed, due to low operating rpm.
Your theory of metal to metal negates the need for oil at all with ball/roller bearings. Furthermore following your theory suggests that slipper bearings should last indefinatley if supplied with oil because there is no contact.

Go and look at many machine shops, trains, mines and tell the operators that their machines cant work because they are drip fed slipper bearings rather than pressure fed.

You are correct that Graphite powder stuffs ball and roller bearings. But not because they are metal to metal but because as previously mentioned they are point contact, not spread over a larger surface area and as you correctly say have small clearances which when closed cause the ball or roller to stop turning creating an extreme pressure point contact that the oil film cannot sustain resulting in metal to metal contact and failure. Slipper bearings fail for exactly the same reason. The addition of any of these products to any ball or roller bearing component will shorten its life considerably.

No i did not say a 20000rpm turbine will stop at the same time as 1000.
Lets get real here, the only way a turbo is going to be spinning at 20000rpm at shutdown is if eg. you were working hard along the beach and suddenly stalled. In all normal driving circumstances the speed difference of a compressor turbine to slow is negligable and enough oil pressure will remain to handle this as a healthy engine does not instantly achieve zero on shut down.
I agree that the most impurities are from the combustion process and not from the turbo being given inadequate time to cool.

You may disagree with me, I may not have made myself clear, what I have previously written is not wrong.

Cheers

Originally Posted by strangy

Frank, ball and roller bearings ar hardened to deal with the loads and speed they carry due to point contact. Talk to bearing manufacturers. your layshafts and mainshafts are damaged as are crankshafts and camshafts because despite an oil film parts wear and eventually the hardening goes and the softer metal wears faster hence damage. You are correct when you say they are splash fed, this is the benefit of ball and roller bearings to operate where an oil pump is generally impractical. Slipper type bearings found in crankshafts and camshafts operating in extreme environments are pressure fed otherwise they would fail if drip fed, yet many slipper bearings in industry are drip fed, due to low operating rpm.
Your theory of metal to metal negates the need for oil at all with ball/roller bearings. Furthermore following your theory suggests that slipper bearings should last indefinatley if supplied with oil because there is no contact.

Go and look at many machine shops, trains, mines and tell the operators that their machines cant work because they are drip fed slipper bearings rather than pressure fed.

You are correct that Graphite powder stuffs ball and roller bearings. But not because they are metal to metal but because as previously mentioned they are point contact, not spread over a larger surface area and as you correctly say have small clearances which when closed cause the ball or roller to stop turning creating an extreme pressure point contact that the oil film cannot sustain resulting in metal to metal contact and failure. Slipper bearings fail for exactly the same reason. The addition of any of these products to any ball or roller bearing component will shorten its life considerably.

No i did not say a 20000rpm turbine will stop at the same time as 1000.
Lets get real here, the only way a turbo is going to be spinning at 20000rpm at shutdown is if eg. you were working hard along the beach and suddenly stalled. In all normal driving circumstances the speed difference of a compressor turbine to slow is negligable and enough oil pressure will remain to handle this as a healthy engine does not instantly achieve zero on shut down.
I agree that the most impurities are from the combustion process and not from the turbo being given inadequate time to cool.

You may disagree with me, I may not have made myself clear, what I have previously written is not wrong.

Cheers

Tell me then if a ball bearing "Floats" on a film of oil and without pressure fed lube how does the ball actually lift itself away from the inner and outer race, oil is used to cool and lube the bearing.
Quote: "ball and roller bearings ar hardened to deal with the loads and speed they carry due to point contact"
You admit that there is metal to metal contact.

Quote:"Furthermore following your theory suggests that slipper bearings should last indefinatley if supplied with oil because there is no contact."

I believe I said slipper bearings "Properly Lubed" have no metal to metal contact when operating correctly. In theory if you built a Slipper bearing engine and only started it once and let it run continously and filtered the oil and renewed as needed while running the bearings or crank would not wear (slipper bearings wear most at starup). What wears a slipper bearing is contamination of the oil with large particles, Stopping, Starting, Pre-ignition, Lugging the engine and over revving. Crankshaft Journals and slipper bearings are made of soft ductile materials, because in a perfect operating condition, there should be no metal to metal contact, all of the things described above cause metal to metal contact in a slipper bearing engine which over a long period of time causes wear.
If your theory was correct crankshafts and the slipper bearings they run in would have to be as hard as a ball bearing and its race.
You still have not explained how a ball or roller makes NO contact with its Race or how the oil film, without pressure feed holds the surfaces apart.

Quote:"No i did not say a 20000rpm turbine will stop at the same time as 1000."

Yes you did.
Regards Frank.