Classic turbo boost - Printable Version
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Classic turbo boost - Tf175 - 03-07-2021
Just checking to see what 8v92TA owners are seeing for turbo boost . My dash gauge indicates 9 psi max . Coach by itself, accelerating up a grade . Same boost when accelerating from 60 mph to 80 , slight grade . Still pulling at 80 , but rpm around 2400 , so I backed off .
I have read numbers on the Web from 10 to 25 psi . Dash gauge indicates about 3 psi low when compared to another gauge I use in the shop, so maybe I have 12psi .
Just replaced both pipes from manifolds to turbo , no soot evident after test drive just now . 60 degrees , elevation about 400 ft , give or take. All new fuel filters .
BTW, no exhaust smoke , usual indicator of low boost /turbo issue .
Thanks ,
Chris
RE: Classic turbo boost - kyleb - 03-07-2021
Mine indicates a max of 20 psi.
Is your air filter good?
Are you getting full throttle travel at the engine?
RE: Classic turbo boost - Johnnyboy - 03-07-2021
Definitely seems low, I believe when I had mine I was 15-18 PSI, the higher the RPM the higher the boost.
RE: Classic turbo boost - Guy - 03-07-2021
Our "classic" boost instrumentation is notoriously inaccurate, more of a suggestion than an indication ,but...... a 35 year old 15 or 20 ton rv in the shape of a brick "80 mph on an incline" and still pulling. What was your pyrometer reading at 80 mph and 2400 rpm ? Seems like it might be running just fine. To quote a famous guru, "just my two cents".
RE: Classic turbo boost - Tf175 - 03-08-2021
Replies appreciated!
Air filter looks good, under 8k miles . Throttle moves to max , at least in static test .
Pyrometer was 600 at 80 mph , 2400 rpm .
Appeared as slight grade . Max boost at lower rpm under load .
I want all available power for pulling trailer , also concerned about possibility that turbo could be losing vane material , particularly on intake side .
Suspect fuel rack adjustment needs attention as there is exhaust temp imbalance between banks at idle .
Thanks , Chris
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RE: Classic turbo boost - Little - 03-10-2021
Ours shows about 20 lb boost at 1900 rpm under full load. 1500 ft elevation, pulling a 16000 lb stacker trailer. Thats the highest I recall. I don't know how accurate the gauge is. The pyro never gets near 1000. The tiny plastic pipe that from turbo to gauge is near 50 ft long so I don't put much faith in accuracy. If your throttle is opening full your exhaust temps should br much higher if you have a turbo issue. I know they do fail but I have never seen one of these turbos come apart except where engine parts try to escape thru the turbo.The oil seals seem to fail first. YMMV Mark
RE: Classic turbo boost - Tf175 - 05-24-2021
A bit of boost update .
Using a regulator and new 30# gauge, connect to 1/8 vinyl tube at engine , thereby testing tubing , connections, dash gauge . Test :
New gauge :10 # , dash 5#
New gauge : 20# , dash 10 #
Dash gauge ( combo w/Pyro )
is a 0 to 20 psi instrument.
One could assume (we all know what that means ) that 9 to 10 psi indicated while driving could actually be 18 to 20 psi . As the coach came with the 20 psi boost gauge it would seem that was intended to cover expected boost .
I have 100 ft of tubing , plan on a lash up to see what boost looks like on new gauge while driving .
Thanks for inputs !
Chris
RE: Classic turbo boost - Tf175 - 05-24-2021
Recent Bus Grease Monkey video involved a Wanderlodge with 8V92 DDEC , down on power and low boost .
They replaced several items including injectors and turbo. DDEC diagnostics showed 23 psi on test drive after repairs .
Perhaps the 'Lodge had a higher HP rating , ours is 475 hp per valve cover sticker . I inspected intake side of turbo , looks good , spins freely , no axial play . Haven't removed pipe to look at exhaust side .
Replaced the air filter gauge , air filter looks good , new gauge should verify .
Chris
RE: Classic turbo boost - Tf175 - 06-05-2021
Ran 5/32 tubing from engine intake forward to the new 30# gauge . Test drive . Saw max boost of 17/18 psi on new gauge , dash reading 9 or 10 . So I'm thinking the boost levels are on par with other mechanical 8V92s .
Now I check the new Filter Minder and find it at 20 inches , almost max . Air filter looks good, but must be time for replacement.
Chris
RE: Classic turbo boost - Fulltiming - 06-05-2021
Might try resetting the Filter Minder first. If it comes back to the previous level after driving the coach, then it will be time for a new filter.