Thread: turbo timer v egt gauge

Originally Posted by strangy

Frank to answer your question
The same way a slipper bearing has no contact.

I wont pursue this any further, my posts explain the basic theory relevant to the original thread and your comments.
I clarified any points I made. My statements come from factory training provided by employment with bearing suppliers and manufacturers.
I am not going to post a 13 page epic on bearing theory/ technology and application to satisfy this discussion. You seem intent to interpret the information for what you want it to say rather than what it does. Fine. The theory and information is readily available, you dont need my input to find it.
There is no point debating bearing types or lubrication methods for this thread.

Cheers

You started this line in this post, I was just sharing my experiences as a Mechanic of 40+ years to correct the points you espouse, let it go at that, eh! Regards Frank.

IMHO, the turbo timer is there to allow a bit of time for the turbo to spool down, cool a little before shut down, EGT's IMHO have nothing to do with it, they are 2 totally separate an unrelated issues and items.

On the bearing issue, you guys should get intouch with a company called BSC bearings and get a copy of their books (which are available on CD) called the Manual, it explains in depth everything you would like to know about bearings and other related items as well as power transmissions and belts etc.

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

Well put.

well thanks guys

some interesting reading

i do at least see there is a differance in the two item mentioned i.e. differant functions

hi Kevin;

I've always been lead to believe that Turbo Timers were Illegal , before having an EGT I use to sit inside the car and let the engine run idle for about 2 minutes or so before shutting the engine off, now with the EGT fitted It doesn't take long for EGT to hit 200 to shut off the engine, on the way home about 5-10 minutes to go I always drive the vehicle very conservative , to allow EGT to Drop a fair bit so I don't have to sit inside for long whilst idling . this way the EGt will take about a minute of so to reach 200 and then I switch it off, I hope this helps, if I have been driving on the freeway I allow myself some time to lower the EGT before reaching home.

Originally Posted by Disco_owner

hi Kevin;

I've always been lead to believe that Turbo Timers were Illegal , before having an EGT I use to sit inside the car and let the engine run for about 2 minutes or so before shutting the engine off, now with the EGT fitted It doesn't take long for EGT to hit 200 to shut off the engine, on the way home about 5-10 minutes to go I always drive the vehicle very conservative , to allow EGT to Drop a fair bit so I don't have to sit inside for long whilst idling . this way the EGt will take about a minute of so to reach 200 and then I switch it off, I hope this helps, if I have been driving on the freeway I allow myself some time to lower the EGT before reaching home.

What are your EGT's in normal highway crusing (say 100km/h flat road)? My Isuzu runs just above 400C preturbo.

Originally Posted by Dougal

What are your EGT's in normal highway crusing (say 100km/h flat road)? My Isuzu runs just above 400C preturbo.

mine sits around 300C

Originally Posted by weeds

mine sits around 300C

where is is the probe ?

In my 300Tdi it's around the 400*C mark @ 100km/h.

Yesterday in the rain and drizzle dropped it 20-25* from 'normal' for a particular stretch of highway.

A truck operator I know tells his drivers that whatever temp is seen at part throttle cruise on the highway is OK to shut them down at and has no issues with engines. If he finds out that any driver has idled an engine too long, eg. for more than two minutes, it's grounds for summary dismissal. In his years in the industry as an adviser and running his own fleet he maintains that diesel idling is the major killer of engines (bore glazing), yet I continue to see owner operators leaving their engines ticking over while having lunch at a truck stop ??