Turbo Boost

[Gary & Peggy Stevens]

I spoke with both James @ Prevost Car in Dallas, and Dale my service advisor @ S & S.

Dale found out there are some dual purpose Barometric and Turbo Boost Sensors in some of our buss's and that may be the culprit, in causing the intermitant failed readings. He is checking into the actual unit on my bus to see if this is indeed the dual sensing unit, and then will continue diagnostics to determine the next step.

Will get back when I know more, which is something that happens every minute of every day. I thought I would say it before everybody else said it.

It's ALL GOOD ! "Loc's favorite saying"

Gary S.

[Loc]

Its all good!

[Gary & Peggy Stevens]

OK, so how many of you know IF YOU have a Barometric Boost Sensor or not attached to your DD60 engine?

Apparently I didn't have one?????? S & S installed a NEW STYLE Barometric Boost Sensor and wired it in line with the Turbo Boost Circuit. I asked the service advisor where they put it, but he didn't have a clue?

They also Reprogrammed the ECM to Raise the Software Level and to Sense the New Style Pressure System.

3 days in the shop, and $ 8 Big Lewbucks later, and I am off again.

Gary S.

[Jon Wehrenberg]

How many zeros are after the 8 Lewbucks.

A turbo boost sensor costs less than $100 and involves a screw and a short piece of tubing, or if mounted directly to the intake manifold a gasket.

Ten minutes. No programming, no magic.

[Ray Davis]

Something doesn't quite add up. If you never had one of those sensors previously, why did you all of a sudden start getting the warnings?

Am I missing something obvious here?

Ray

[Orren Zook]

It was probably a warning that you might have too many lewbuck$ on the bus and they wanted to help by lightening your load......

[Gary & Peggy Stevens]

Jon, it was two "0's" after the 8. And yes the sensor they added only cost $85.00, but there was the 6 hours of labor to test, install, upgrade the software, and misc. shop stuff, (rags / hand soap etc.. ) you know...... All the things they needed to do to get the price jacked up ?

Anyway I better not have that intermittent warning light come on the dash anymore? They said the Code 86 had come on 36 times, according to the reader, and I remember it coming on maybe 6 times since I have driven it, so I guess it was driven like that for quite awhile before I got it. I could have let it go, but didn't feel right, so I fixed it.

The service advisor @ S & S initially said, my year of bus doesn't have a B. sensor, so go figure.


Ray, I don't think when you take these bus' in for service, anything is OBVIOUS ? Sure wish I lived closer to Tn.. Loc is just no help with this stuff?


Gary S.

[Jon Wehrenberg]

Gary,

This is instructional in that S&S reached into your wallet and did an extraction.

If I have to have someone service my coach I follow the Ken Z school of though in that I stay right there. Then I ask dumb hard questions like if you are going to charge me more than the 15 minutes to replace the sensor explain carefully what I will be getting for the money you are charging.

Can I defer the process or the repair? What would have happened if the sensor did not fail and you did not spend six hours (that's bullshit I think) upgrading my DDEC? You see where I am going with this.

BTW, I had a funky sensor once. The codes gave me information about turbo boost, but since I was flashing the code I did not have any detail beyond that. When I talked to the DD dealer they thought it was the sensor which the codes would indicate, because I had already verified the turbo was working. But then they told me thay needed my coach to go through the entire thing because it could be a bad ground, a bad connection, etc. etc. I thanked them for their concern, ordered a sensor, put it on and never had any more issues. You can make almost anything a bigger deal than it really is.

[Ray Davis]

I guess I will just remain a bit confused.

If they indicated that they had removed the old sensor, replaced it, AND did all the other upgrades (to jack the price), then it would make sense to me.

But, I don't understand how a coach that evidently didn't have a sensor and worked just fine for some long period of time, started generating codes that didn't before, and adding a new sensor solved the problem.

Mark me as confused ...

Ray

[Jon Wehrenberg]

Our coaches have a turbo boost sensor. It measures the amount of boost pressure which it communicates with the DDEC.

The DDEC processes that information and meters the correct amount of fuel to the engine. If fuel flow was a constant, you would have lots of black smoke until the turbo boost pressure increased sufficiently to provide the correct amount of air for the fuel being injected.

As emissions standards increased, the turbo boost sensing got much more sophisticated. CA for example has a snap throttle test that must be passed. At idle the throttle goes from idle to full throttle almost instantaneously. Since the turbo has not spun up at that point the DDEC will not feed enough fuel to make black smoke. As the turbo boost increases, and is sensed the fuel flow to the injectors increases proportionate to the amount of oxygen available for combustion.

My guess is that Gary has an updated sensor, more sophisticated than a simple sensor which just measures air pressure in th eintake manifold, and software required to read the data, so his coach likely runs cleaner than others of his vintage.