Power Problem with FM260

[mog]

In addition, he tells me that I should expect a roughly 15% loss through the powertrain, which makes sense to me. Anyone have a different coefficient?

10-15% loss for the drivetrain is a fairly common number. I've seen this for cars/normal trucks even with manual transmissions. So I would guess you would be at the top end (or higher) with your uber-truck and the automatic.
A couple thoughts:
It sounds like the dyno test ‘max' numbers will now be set by your transmission's down shift point. This is adding another variable to your power problems. ‘Our' thoughts so far have been either your turbo is not giving you the rated boost pressure because:
A.) The turbo or its control system is not working properly
B.) The other engine system (fuel, exhaust, intake, etc) are not working properly
With the dyno test as describe you will be adding
C.) The transmission or its control system are down shifting prior to max HP/Torque.
-

I would perform the dyno test, but I don't know if I would take that as the gospel, with the ‘C' factor added.
There is a saying in troubleshooting “you have to know what is normal, before you can know what is abnormal”. I would still follow-up on why you are not getting the rated boost (and if the book value is the real life value).
-Maybe just make your truck a little more aerodynamic will solve your problems :sombrero:

 

[JRhetts]

Info re: Dyno Test with Auto Transmission

I got a call from 'the engineer' I mentioned in my post #25 above. This guy said he has been doing dyno tests on trucks and RVs for more than 20 years, over a thousand tests, he said. He has never experienced a transmission getting damaged by a dyno test. He cautioned me to be sure the rig was "well secured" as some rigs will experience a jolt when shifting and the rig could shift on the rollers to bad effect. But he invoked the same analogy as I had originally thought – downshifting at the end of the run as load has been ramped up on the dyno rollers is exactly analogous to downshifting going up a hill. This is what the tranny is designed to do.

He also discussed with me that my Allison has a "lock up clutch" on the torque converter; what this means is that after the shift is completed, the transmission locks up mechanically so there is no on-going loss of energy due to hydraulic effects inside the tranny. When locked up in between shifts the only parasitic loss at the tranny is the hydraulic pump, which is very small.

This guy seemed very knowledgable about both trannys and dynamometer tests, and spent 45 min on the phone with me. His overall advice was to take my peak HP and Tq numbers with a big grain of salt, because I don't know what the parasitic drains from elsewhere are: air compressor, fan, engine-mounted pumps, A/C, etc. So, I "may" find my numbers useful, but perhaps not so much so. His experience is that the "15%-20%" rule of thumb for parasitic loss can actually be much higher or much lower; one really needs a database from comparable vehicles to interpret one data set meaningfully.

 

[JRhetts]

I want again to thank everyone who has contributed to this thread!

I don't know if it has helped anyone else, but it sure has me. As I said somewhere before, I see myself as a 'driver', an explorer who uses a truck to go to the places he likes to explore; I don't see myself as a mechanic.

Now, I know this is a bit silly or artificial, as I designed and with LOTS of help built out the entire new house system along with some of the running gear. In doing so, I drew mostly on what I already knew from past experience or depended on the knowledge and judgment of trusted others. So I wasn't subjectively aware of a lot of new learning curves.

However, the truck, and specifically the engine, certainly have presented a whole new learning curve. And, although it was not my first choice, I sure am climbing it. And you have helped immensely, both by the content of what you have posted as well as by what your posts have stimulated me to think through and learn about.

I am in the midst of trying to pull together a comprehensive analysis of what I know and what my options are. I'll probably post that later for your information and/or amusement.

In the meanwhile, thanks so very much. Keep the suggestions/observations/questions flowing. Please!

 

[kerry]

Anyone near you with an FG and lots of miles under their belt who could drive yours and give you their impression of its power?

 

[JRhetts]

Not that I know of. But the new EarthCruiser shop is here in town, so I could see if any of them have actually got any miles under their belts. I could ask if they would climb some of the local hills with one of theirs and compare speeds and times. Thanks for the suggestion!!
John

 

[SkiFreak]

View attachment 193026
I'm sorry... aerodynamic aside... that's not what I would consider a good looking truck. Would probably work well as a giant doorstop however.

 

[mog]

Anyone near you with an FG and lots of miles under their belt who could drive yours and give you their impression of its power?

Not that I know of. But the new EarthCruiser shop is here in town, so I could see if any of them have actually got any miles under their belts. I could ask if they would climb some of the local hills with one of theirs and compare speeds and times. Thanks for the suggestion!!
John

If you think it would help, I'd be glad to bring my FG to Bend for some on road comparisons. That way you would have seat time in the FG, so it would be a two way interpretation. Since it is ‘open' in the camper I could weight it to have the same ratio of weight/power.
Also if you would like some help with independent testing (I suspect the control circuit for your turbo, or a fuel issue) I would be happy to turn a wrench or two. Drop me a PM if you are interested.

 

[mog]

I'm sorry... aerodynamic aside... that's not what I would consider a good looking truck. Would probably work well as a giant doorstop however.

Yup! one of the few vehicles with the Mercedes Star that looks butt ugly :Wow1:

 

[JRhetts]

If you think it would help, ... I would be happy to turn a wrench or two. Drop me a PM if you are interested.

mog
What a generous offer. I sent you an email a few minutes ago.
John

 

[JRhetts]

Diagnostic Progress

Hey Guys

As I know I have already expressed, I REALLY appreciate all the ideas and suggestions you have offered.

I actually made notes from all of your posts, and then over the past couple of days I developed an agenda of tests and checks to work on in order to try to diagnose what is going on.

More to come, later.

 

[mhiscox]

Great job sharing your information, John. This is one of the best threads ever for solving a problem, and it really shows the advantage of a forum like this . . . smart and experienced people helping a logical and literate owner.

 

[kerry]

Good work. It suggests a couple of possibilities: One is that the Mitsubishi mechanics who worked on your truck and replaced the turbo are not very good mechanics or that they didn't tell you the whole story and that for some reason they wanted to keep the boost level low.

 

[charlieaarons]

John, do have a pyrometer installed? If the wastegate is the problem and if there is feedback between the intake manifold pressure and the fuel injection computer, then EGT should have risen with more fuel being injected.
OTOH if no feedback then 1) there should have been black smoke at full throttle before your "repair" and 2) EGT should have actually dropped.
I suspect the former is true, there probably is an intake pressure sensor. I'm curious about this.

Charlie

 

[kerry]

John, do have a pyrometer installed? If the wastegate is the problem and if there is feedback between the intake manifold pressure and the fuel injection computer, then EGT should have risen with more fuel being injected.
OTOH if no feedback then 1) there should have been black smoke at full throttle before your "repair" and 2) EGT should have actually dropped.
I suspect the former is true, there probably is an intake pressure sensor. I'm curious about this.

Charlie

Not sure I'm following this. My experience with diesels is that the more unburned fuel (ie-more black smoke), the higher the EGT's.

 

[westyss]

Not sure I'm following this. My experience with diesels is that the more unburned fuel (ie-more black smoke), the higher the EGT's.

EGT will show a higher temp when there is a lean fuel situation, more fuel = lower temps as the fuel will help keep things cool.