1983 MCI9 6V92 Runs like a snail

[LEH44]

 Bus had fresh rebuilt engine installed at purchace. Have put 4,000 miles on rebuild to make sure everything was OK. Have changed fuel filters and air filter and no improvement. Slow take off and no pulling power up hills. No smoke and no oil leaks just no power. Checked injector tag and found 7G70s


UPDATE:I just pulled the injectors out and the tips appear to be almost completely carbon/clogged could be part of the problem.
Engine in bus is a manual no DDEC. As for weight if I remember it was 34,000+/- a few hundred its writen down somewhere.
Coach is a former NJT bus. Still has city gearing so 65mph is pushing it.

[uncle ned]

Need to look at the post for the 825 hp engine.  But the real reason to own a old bus is to take your time and see the usa.

uncle ned

by the way my 6v92 is not slow just smokes a lot

[Busted Knuckle]

Welcome to the madness.
Now it's hard to say what the problem is. First off you have to remember a bus weighs 25-45,000 +/- lbs. and rebuilt engine or not 0-60 times will be in minutes not seconds!

Now I'm not saying that there is not a problem, but without more details it is hard to even begin to tell where.

Let us know what part of the country you are in, and maybe one of our experienced busnuts will be close by, or we can suggest a good shop near by.
  BK 

[cody]

I got passed by a june bug on our way back from the zoo, I had to slide the windows shut, the flies that we got at the zoo were going out and inviting their friends and catching up to us and coming back in to party.

[bevans6]

Well, no one else chiming in so - I think 70 injectors are on the small side for a 6V92, but I don't know if there are cam or cam timing changes required to run larger injectors.  Is it mechanical or DDEC?  Are you getting proper turbo boost pressure?  Maybe it's doing all it can do...

Brian

[robertglines1]

Who did rebuild?How much does bus weigh??

[Geoff]

With the 7G70 injectors you only get 277 HP.  Plus you have a throttle delay.  You need to install bigger injectors and you could get 350 HP with no smoke.

--Geoff
'82 RTS AZ

[bevans6]

MC9 with 277 hp and a throttle delay and an automatic would probably seem a little slow.  Is there a chart or reference that shows the relationship between injector size, injector timing (if it differs) and HP in a typical 6V92?

Brian

[prevost82]

If you want it to haul-a*s in the hills you'll need more ponies .... 500 hp 8v92TA

[JohnEd]

Given that the acceleration is so very slow....could you time you acceleration to 50 with a stop watch and with the exact weight figure the "wheel horse power" needed for that performance?  My guess is that we all should know that number so we can evaluate the actual improvements with any and all mods.  Math guys?

John

[Iceni John]

My 277 HP Californicated version of the 6V92 moves my bus's 26,000 lbs without any problem, even up 6% grades where it will maintain 36 to 39 MPH with its 4.1 axle.   How slow is slow?   How much do you weigh (your bus, not you)?   Is your transmission slipping out of lockup?   Do you have unusually high transmission temperatures?   How hot is it outside where you're driving?  -  my bus feels quicker when it's colder outside than when it's 100+ degrees.

Maybe those pesky plate tectonics are up to their usual tricks, shifting the crust slightly up against the direction you're driving.   Or maybe not.

John  

[baker4106]

Is the engine a DDEC?   Have friend with a MC9 with low power and rpm once in awhile.   Found a bad wire in the molex in the engine compartment.   Bus runs good now.

[David Anderson]

With the 7G70 injectors you only get 277 HP.  Plus you have a throttle delay.  You need to install bigger injectors and you could get 350 HP with no smoke.

--Geoff
'82 RTS AZ

Hey Geoff,

Welcome back.

David

[Geoff]

Thanks, David-- I remember you from the old board, I think you and I were at about the same place in the conversion process 10 years ago.  I hope you are enjoying your bus as much as I am (when I can afford to take it anywhere!).

--Geoff
'82 RTS AZ