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
1986 #89
VIN 007
Detroit 8V92 TA 475 HP
Allison four speed
Chris and Sharon Hand
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".
Guy & Sue
1984 Classic 40' #59
(This post was last modified: 03-07-2021, 09:03 PM by Guy.)
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
Image
1986 #89
VIN 007
Detroit 8V92 TA 475 HP
Allison four speed
Chris and Sharon Hand
(This post was last modified: 03-08-2021, 05:23 AM by Tf175.)
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
Mark and Marian
1986 #125 (left us for a new home in Oregon)
1999 Wanderlodge LX40
1979 Mc 8 6V92
Pace 28' stacker
Regina Beach SK Maricopa AZ
(This post was last modified: 03-10-2021, 09:13 AM by Little.)
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
1986 #89
VIN 007
Detroit 8V92 TA 475 HP
Allison four speed
Chris and Sharon Hand
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
1986 #89
VIN 007
Detroit 8V92 TA 475 HP
Allison four speed
Chris and Sharon Hand
Turbo saga continues.
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
1986 #89
VIN 007
Detroit 8V92 TA 475 HP
Allison four speed
Chris and Sharon Hand
