8V92T boost pressure ? what should it be?

[mikelutestanski]

Hello:   I am writing this for my friend with an 85 Prevost XL with an 8v92T engine 475 Hp with a five speed 750 auto.. He is wondering what the boost pressure should run.  His max is 11 lbs of boost. running flat on I95 at about 70.  Is that about right?  Under what conditions would the boost pressure change?  Additionally what would/should the max boost pressure be?   THank you in advance for your thoughts on this matter.  I am sure the fellows with experience with this engine can help out .. Mike   

[niles500]

Miker - IF your gauge is correct - should be 20 to 25 PSI at full load - HTH

[prevost82]

On my 8V92ta I get about 15 lbs under full load.
Ron

[HB of CJ]

I dunno for sures.  Your friends 475 Detroit 8V92T might be set up differently than others.  Lots of differences, like intercoolers, injector changes, different turbos, timing, governed rpm, etc..

Running "flat out" may be putting the mill against the rpm governor, which limits the fuel, thus reducing the observed boost.  Perhaps the best way would be to put the coach of a chassis dyno and let her rip.

Or....if you can find a good steep hill, let the mill lug a little bit and various rpm levels and observe the boost gage.  With an Allision, I dunno how this could be done.  The tranny may downshift too soon.

Even watching the boost gage while accelerating wide open may not work as the condition is too dynamic or changable.  You need a condition where the mill is working the hardest.  Good luck. 

[luvrbus]

Mike, my 8v92 runs about the same as your friend and Ron i have seen 20# in the mountains and in 2nd gear but that puppy was working and i could tell at the next fuel stop i didn't like that  20#.HB is correct about the set up has a lot to do with the boost