| Author | Message | ||
| Buswarrior (Buswarrior)
Registered Member Username: Buswarrior Post Number: 2088 Registered: 12-2000 Posted From: 174.89.178.140  Rating: N/A |
Posted in DieselChat yesterday: robnorthtriple: Does anyone know who can set the boost upon my '94 MCI with a 6/92T DDEC engine. I have a gauge on the dash panel and it shows 15lb of boost under load and a sit slows down climbing a hill, it drops to 12lbs of boost and 25 mph. I have fitted a new turbo. Thanks Rob North.. | ||
| Dal Farnworth (Dallas)
Registered Member Username: Dallas Post Number: 566 Registered: 7-2004 Posted From: 67.141.77.61  Rating: N/A |
It sounds like there is an exhaust leak. Look for any black marks anywhere from the manifolds to the hot housing. ANY leak will cause a lowering of boost under load. | ||
| Luvrbus (Luvrbus)
Registered Member Username: Luvrbus Post Number: 1133 Registered: 8-2006 Posted From: 74.33.60.241 Rating: N/A |
sorry double post (Message edited by luvrbus on June 02, 2011) | ||
| Luvrbus (Luvrbus)
Registered Member Username: Luvrbus Post Number: 1134 Registered: 8-2006 Posted From: 74.33.60.241 Rating: N/A |
Check for leaks then it could also be a bad boost sensor check the codes there is no adjustment per say only different turbos good luck | ||
| Jim Shepherd (Rv_safetyman)
Registered Member Username: Rv_safetyman Post Number: 332 Registered: 1-2004 Posted From: 72.171.0.142 Rating: N/A |
My thought is that it could be fuel restriction (filters or?) or air intake restriction (again filter). If it does not get enough fuel or air, the ECM can't make it build boost. The other obvious problem, if it has one, would be a leak in the charge air cooler. In an extreme case, it could be some sort of blockage of the exhaust system after the turbo. So far, my experience with MAP sensors (in the early years of the DDEC, they used a GM MAP sensor), it is either good or bad but does not go slightly bad. Jim Shepherd Evergreen, CO ’85 Eagle 10/Series 60/Eaton AutoShift 10 speed transmission Somewhere between a tin tent and a finished product Bus Project details: http://www.rvsafetysystems.com/busproject.htm Blog: http://rvsafetyman.blogspot.com/ (Message edited by rv_safetyman on June 02, 2011) | ||
| Luvrbus (Luvrbus)
Registered Member Username: Luvrbus Post Number: 1135 Registered: 8-2006 Posted From: 74.33.60.241 Rating: N/A |
Larry Jones just tricks his sensor so it will build boost on his DDEC I he couldn't get up his driveway the thing would not build boost or power now he runs around 20lbs all the time. A 1994 model will probably not be a engine using the old sensors most of the III on the 2 strokes were up dated by DD (Message edited by luvrbus on June 02, 2011) (Message edited by luvrbus on June 02, 2011) (Message edited by luvrbus on June 02, 2011) | ||
| Tom Christman (Tchristman)
Registered Member Username: Tchristman Post Number: 294 Registered: 1-2006 Posted From: 66.218.33.156 Rating: N/A |
Low turbo boost would be caused by dirty air filter or a restriction in the air intake, dirty fuel filter, leak in the exhaust system, plugged up muffler, worn injector tips, low compression, burnt valves, turbocharger that has tight bearings, etc. Should have a good mechanic look at it. You could simply remove the air intake from the turbo and exhaust from the muffler and see what that does on a short drive. Good Luck, TomC | ||
| Jim Sanders (Sandy)
Registered Member Username: Sandy Post Number: 53 Registered: 1-2011 Posted From: 69.199.96.250  Rating: N/A |
Hi guys I have been wondering if a Boost>vaceum Gauge would give a driver some ideas of the load he was putting on a 6-92 T Dont know whether it is inter coled or not????? | ||
| Luvrbus (Luvrbus)
Registered Member Username: Luvrbus Post Number: 1136 Registered: 8-2006 Posted From: 74.33.60.241 Rating: N/A |
If it is a 6v92 TA it will be aftercooled a inter cooler will be on the outside of the radiator most of the time a boost gauge is good to have for driving the higher the boost means more fuel going through that puppy good luck (Message edited by luvrbus on June 02, 2011) | ||
| George M. Todd (George_todd)
Registered Member Username: George_todd Post Number: 1239 Registered: 8-2006 Posted From: 99.37.28.23 Rating: N/A |
Technically, an intercooler is between the 1st and 2nd stages of a two stage air compressor. Both the engine mounted air-to-water cooler, and the radiator mounted air-to-air coolers do the same thing, and both are AFTER the turbo. Turbo pressure is a function of the amount of exhaust being produced, which is a function of the amount of fuel being burned, and engine speed. So, turbo pressure will be greatest at nearly full governed RPM, with full throttle. As the governor moves the fuel rack to limit max. RPM, the turbo pressure will start to drop. As the engine slows down under a heavy load, it is making less power strokes, so it is producing less exhaust, so it produces less boost. Partially dirty fuel filters won't let enough fuel thru under load, a dirty air filter won't let enough air into the turbo. An improperly adjusted throttle won't tell the engine to deliver full power. No change in pressure over the old turbo? If not, he replaced a good turbo, which wasn't the problem. As there is NO way to "set" boost, you set boost with your right foot, the low turbo output problem is elsewhere. What is the max. RPM setting? If its a DDEC, has the MAP sensor and wiring been checked? If the DDEC doesn't see enough turbo air pressure, it restricts the fuel input to avoid black smoke, so less boost and less power. G | ||
| Luvrbus (Luvrbus)
Registered Member Username: Luvrbus Post Number: 1137 Registered: 8-2006 Posted From: 74.33.60.241 Rating: N/A |
Waste gate turbo on the later 2 strokes were adjustable but you don't see many TomC has a waste gate turbo on a 8v71 but not the norm for a 2 stroke | ||
| Dal Farnworth (Dallas)
Registered Member Username: Dallas Post Number: 570 Registered: 7-2004 Posted From: 67.141.77.61 Rating: N/A |
After all is said and done... I've looked at a lot of bus owners that complained of loss of boost. In about 90% of those cases, I found that either the exhaust manifold or the rubber tubing between the rest of the system was leaking. It didn't matter if it was DDEC or MUI.... But then again, I could be wrong. Hint: Make ABSOLUTELY certain there is no exhaust leak anywhere. | ||
| Pete/RTS Daytona (Pete_rtsdaytona)
Registered Member Username: Pete_rtsdaytona Post Number: 661 Registered: 1-2005 Posted From: 184.88.99.113  Rating: N/A |
Make sure you have the right TBS (Turbo Boost Sensor) D/D old# - 16070629 D/D new# - 23528418 or GM old# - 1219935 GM new# - 28182633 or Delphi# PS10083 These are all TBS's with a 3 BAR range 70-300kPA There are a bunch of other TBS out there (EXACT SAME STLYE / LOOK / CONNECTOR) with DIFFERENT pressure ranges -- they will give invalid readings / results This style was WIDLY used as MAP sensor for all sorts of GM cars/trucks/etc gas or diesel Pete X/RTS | ||
| Jim Sanders (Sandy)
Registered Member Username: Sandy Post Number: 54 Registered: 1-2011 Posted From: 69.199.96.250 Rating: N/A |
sorry guys I guess that i will have to wait until i get this scrap heap of mine running( if that ever happens) and then worry about eng controles Thanks any way guys Jim |