my water to air intercooler install

[Ben-e-boy]

Whats the theory behind journals running hotter than ball bearings??

I dont know and I cant think of why either

[04OFF]

All things equal, more Friction = more heat, and the BB Turbo being a little more efficient to generate the boost will consume/waste less energy as heat to make the same Boost , then of course journal turbos need much more engine oil cycled through them adding even more heat to the engine, it all adds up, and your cooler has to try pull all this heat away.


Plus they say "Slightly higher" temps, not how much, so this could be only 1/2 a degree ?

[nissannewby]

Yeah I could understand this if the turbo wasnt watercooled. I think I may have to look into this further

[04OFF]

Yes, but if all was equal, the Ball Bearing Turbo would also be water cooled !

[Bambill]

Both bearing systems run on a cushion of oil.
The BB will spool up faster by whatever % (is on Garrett site).
The BB requires less oil so you may get a slight and I mean slight reduction in heat transfer there, but as for EGT's the only thing that could affect it would be efficency.
All things being equal apart from bearing cores, there should be no difference in the compressor wheels efficency though.
If anyone finds the answer to this question I would be most interested in the explaination for it.

[04OFF]

The compressor side of the 2 Turbos may be 100% identical, and so just as efficient as each other in theory, but you have to look at the Turbo as a complete unit, the journal bearing Turbo will require more energy input on the Turbine side, to drive the Impeller at a equal rate compared to the BB Turbo (due to the added friction from the journal bearings).


Everyone knows friction generates heat, sure it would be minimal heat transfer from the journal to the Impeller and so to the intake, but its still a tiny amount of increased heat, but i would say more important, is to look at the whole engine as a package, and how the engine is working just that little bit harder to drive the Turbo.



Working harder requires the passing of more exhaust gasses and so again a little more heat is added into the mix, the result is the whole Turbo runs just a little hotter and will pass a little heat on to the incoming air into the compressor, a slightly hotter intake means the compressed air is a little less dense, and in turn has less 02 available for the combustion, so again this slightly reduces efficiency of the whole package in a nasty little cycle.



Intercoolers can only be so efficient, It makes sense that the higher the temps entering the Intercooler, the higher they are leaving the cooler, remember we still don't have a actual temp figure, just that its slightly hotter, so it could in fact be very little difference, but personally i can easy understand how there "could" be a little difference in intake temps between the two types of Turbos.

[Bambill]

Sorry to Ben n boy for this going off topic here a bit.
That was not my intention when I asked the question about temps earlier I was just curious for a comparison.

040FF, Sorry I cannot see the friction making a difference.

No offence to anyone but it sounds like good salesman dribble to me.
Am happy to be PROVED wrong though.

Marty

[04OFF]

No problem Marty, ive tryed to explain it to the best of my personal understanding, thats by no means a guarantee im right, but simple physics dictates, Friction = Heat.

Anyway, as you correctly say, we have probly hijacked Bens thread enough now

[Ben-e-boy]

i can see the friction equals heat and considering that a bb turbo has less contact area than a journal bearing ill go with that until proven otherwise in saying that i think it would be miniscule difference
dont worry about the hijack.its a good technical conversation.
bambil. the guys are pretty ordinary salesman to be honest they just tell you what they know if you dont like it go somewhere else kinda thing
and while we are here the biggest issue with text is that you cant judge attitude. no offence given or taken
in the near future ill get a temp gauge and do some serious testing
benny