Power Problem with FM260

[JRhetts]

I think I have figured out where I am.

A few hours ago I felt embarrassed because it looked like I might have been chasing an illusion.

Why?

By installing a $15.00 boost adjustment valve I bought on ebay, I was able quite easily to adjust things so that I could increase the boost pressure at the Intake Manifold by 4 psi – to the factory spec of 22 psi – without causing the ECU to set any fault codes or put me into ‘limp' mode.

Overall, I made 12 runs up a 3+ mile grade that I have previously used as a test grade. [Unfortunately, I do not know the %grade rating of the hill.] My dependent variable was speed in mph read on my GPS. I established as constant as possible a 55 mph approach speed to the beginning of the hill; as I reached a visible marker at the beginning of the hill I put the accelerator to the floor and kept it there until attaining the top; I recorded my speed at the point the grade exerted its maximum effect on my vehicle – i.e., how much did the grade slow me down under different levels of turbo boost.

First, I made 6 runs at 22 psig. Then I made 4 runs at 18 psig. Because I could tell that the 4 speeds at 18psi didn't look different from the 6 at 22psi, I did 2 more runs at 22 psi just to bracket the runs at 18 psi in case something had changed in the time it took to do all this.

My results are below. No complex statistics needed to see that there was no meaningful performance difference between 18 and 22 psi of boost. The larger number of 22 psi readings were spread out over a larger range, but I do not see the central tendencies as being meaningfully different.



My first reaction to this was surprise; I really had trouble imagining that 4 psi of additional boost would not allow me to maintain a higher speed when climbing a hill. Further reflection led me toward concluding that I should take this data to mean that it is time to accept the power I have and move on to simply drive the damn thing.

John

 

[kerry]

Very interesting results. Looks to me like there is a slight performance increase at 22psi since there weren't any 18psi runs above 43mph. I like the systematic experimental approach.

 

[gait]

Very interesting results. Looks to me like there is a slight performance increase at 22psi since there weren't any 18psi runs above 43mph. I like the systematic experimental approach.

that was also my impression. Possibly a small improvement. Around 3.5%. Usual disclaimer about no statistical significance etc. - not enough data for anovar ....

Beyond embarrassment its easy to get to doubting one's own sanity when chasing this sort of stuff. Even if there's no improvement getting to a known baseline is never wasted. But my guess, at a distance of many thousands of miles (well, km anyway), is that eventually a couple of small but important changes will have improved performance to at least meet manufacturer's spec.

Increasing the boost pressure so easily suggests that there are no obvious restrictions in air intake or exhaust.

Having added the boost control also means more data will be available from the dyno test. Posible at two boost pressures. Which would immediately give something to compare. Possibly not as good as having a whole fleet to compare with but invaluable. Two data points are infinitely (forgive the hyperbole) better than one.

 

[JRhetts]

Is the 22psi number for the turbo a normal operating figure, or a max output figure? It makes me wonder if they normally operate at that figure if the limp home mode kicks in at 23. (I am thinking of it like engine hp, during normal operation you never see max hp as that is only reached at near red line.)

You have framed your question as an ‘either-or’. I would like to suggest that, instead, it should be a ‘and-both’.

As I understand it, a turbocharger [different from a ‘supercharger’] is a self-regulating/self-limiting mechanism the goal of which is of to maintain a designed level of boost, up to a designed maximum, within a designed range of density altitudes/temps. From the factory Shop Manual, the FM turbocharger model TD06 [Mitsu] is designed to achieve a limit of 73kPa @ sea level @ 68°F. This translates to 10.5 psia [where a = absolute, not psig for gauge pressure].

To get gauge pressure, what you’d read on the dash if you have a gauge, you'd have to add the absolute atmospheric pressure at the altitude [and temp, if you want to get really accurate] at which you are operating the vehicle. At sea level at 68°F you'd add 14.68. [This = 25.2, a number which will come up 3 paragraphs later, below.]

So, for general purposes, 22 psi is the max reading you should expect to see when you have the Fuso FM engine under load at a whole range of altitudes. The turbo and its waste gate are designed to cooperate to operate up to a max boost pressure, under sufficient load conditions, at that level. Depending on load, it can be sustained for quite a long time, but it is also the max boost that the IM should experience.

Until the load [accelerator pedal, etc.] is high enough, you wont see the max boost. And if you try to operate at too high an altitude/temp, the turbo will no longer be able to put out enough boost to reach the max level. But, as long as you are operating within the turbo’s design range, the waste gate opens and closes continuously to regulate pressure up to the designed limit; if the load warrants, it will be at that max level.

[I really don't want to confuse things, but... on the FM the ECU is what sets the 22 psi max; if its electronic sensor registers a voltage higher than what is calibrated to correspond to 22 psi, it sets an error code. The mechanical turbo and waste gate are capable of producing at least as high as 25 psi at sea level; the ECU limits this mechanical max boost to 22 psi. On the other hand, the "extra" 3+ psi is what gives the overall system the capability to respond with more boost when the air gets less dense at higher altitudes or higher ambient temperatures.] What I have done over the last few weeks is to figure out a way to move the actual mechanical max operational boost pressure closer by 4 psi to the ECU's electrical fault limit of 22.​

So, in the end, my response to your question is: 22 is the “normal and operational maximum” boost level. And in that sense it is unlike your HP metaphor. I see the max [22] all the time at all stages of speeds, rpms, and to some extent accelerator pedal positions.

I think I have got it right, and I hope it helps.

 

[JRhetts]

that was also my impression. Possibly a small improvement. Around 3.5%. Usual disclaimer about no statistical significance etc. - not enough data for anovar ....

Yep!! No ANOVAR here. But just because I can [Excel makes it ridiculously easy], here are the usual central tendency calcs on my numbers:

	mean	median
@ 18 psig	41.8	42.1
@ 22 psig	41.9	42.3

Not sure how you folks view it, but I don't see [and didn't feel] any meaningful difference.

I'm planning to chase that fuel bugger down as best I can. Hell, I may even understand a diesel engine by the time I get done with all this. Crap.

 

[JRhetts]

...Looks to me like there is a slight performance increase at 22psi since there weren't any 18psi runs above 43mph.

Honestly, I think the [greater] variance in the 22 psig set is a function of measurement error. That is, I couldn't hit the starting point at the bottom of the hill at the exact same 55 mph speed - at least ±1.5-2 mph. Sometimes I was decelerating to get down to 55, and sometimes I was accelerating to get up to 55 as I hit the mark to put my foot down. I think this introduced plenty of noise or variability in the distribution of results, even though I was trying my best to keep everything constant. Long and short, I am leery of over interpreting differences in the two data sets.

I like the systematic experimental approach.

The [secret] scientist in me likes it too. What it boils down to is: I was trying to simulate a dyno test without all the equipment. Just had to drive a ways [well over 200 miles by the time I got back home.]

 

[mog]

Honestly, I think the [greater] variance in the 22 psig set is a function of measurement error. That is, I couldn't hit the starting point at the bottom of the hill at the exact same 55 mph speed - at least ±1.5-2 mph. Sometimes I was decelerating to get down to 55, and sometimes I was accelerating to get up to 55 as I hit the mark to put my foot down. I think this introduced plenty of noise or variability in the distribution of results, even though I was trying my best to keep everything constant. Long and short, I am leery of over interpreting differences in the two data sets.

John, Perhaps instead of a fixed "what MPH", it would be better to use a time vis distance measurement.
Overall time from your starting point up the hill, to a fixed ending point at different boost pressures.
I have a GTECH-Pro (http://www.gtechpro.com/prod.html 1994 version), I can drop in the mail to you, if you like.
-
Although I'm worried pretty soon we will see a big coffee-can exhaust pipe with 'Rad' graphics on your Fuso.
I hear there is a new movie coming out next year in the Fast and Furious Franchise (Vin Diesel is not play Dominic Toretto due to a new lead they have cast)
Click to enlarge:

 

[mog]

Overall, I made 12 runs up a 3+ mile grade that I have previously used as a test grade. {Unfortunately, I do not know the %grade rating of the hill.}

John,
You can calculate the grade of your hill with a couple steps (I used this process for trip planning in my under-powered Fuso).
Select your hill (or trip) using Google Maps for the start and finish of your test
Goole Map route plan
Then copy the URL for that section (see photo-instruction below)
Paste into GPS Visualizer (see photo-instruction below)
http://www.gpsvisualizer.com/profile_input
Select 'Draw the profile' and you will get a profile of your hill (or trip) with distance and elevation change (see photo-instruction below)
Then divide distance and elevation change (converted to same 'units' of course) and you will have your grade.
-
Click once to open, then click on that again to get full size, or right-click and open in new tab for full size (legible size) 1 meg file

 

[JRhetts]

Turbocharger 101??

Think I can summarize what to me is “Turbocharger 101”

1. My FM Service Manual gives the ‘boost limit’ spec as

​

3kPa/21.6 in-Hg/545 mm-Hg at sea level and 68°F​

2. This equates to an upper limit [max] from the turbocharger of an absolute pressure boost of

​

~ 10.5 psia at sea level and 68°F​

​

​

As an aside for the FG owners, the 2005-2007 Service Manual spec is 67.8kPa/20in-Hg/509mm-Hg at sea level/68°F, which equates to 9.8 psia.​

3. At this point, you may ask: “How come only 10.5 psi; I thought we were talking in the neighborhood of 22 or 23 psi?” Took me a while to figure this out: the absolute boost [at max] of 10.5 psia must added onto the absolute atmospheric pressure where you are operating, to get the gauge pressure you will read on the dash. Thus,

​

at sea level at 68°F atmospheric pressure = 14.68 psia​

4. The gauge on the dash would at max boost [if you could develop it] read

​

10.5 + 14.68 = ~ 25 psig [gauge pressure]​

5. But, with this engine, one should not expect to see/read pressures up to the turbocharger’s limit [here 25 psig]. Why? At least two reasons: 1) the engineers wanted to build a long-life rather than hot-rod engine; so they ‘de-tuned’ it from the max it could develop [to less than 25 psig]; 2) using a turbo that operates at less than its max leaves some ‘headroom’ so it can increase output from reserve capacity to maintain sea level performance [max rated boost/power] over a range of conditions like: altitudes above sea level and summer temps higher than 68°F, when the density altitude is thinner. [In my case, if I assume a max operating psig of 22 psi, I can expect to develop full boost up to roughly 6,000 feet. That is the altitude equivalent of 3 psi (i.e., 25–22) that are in reserve.]

6. How did the engineers ‘de-tune’ the engine? How did they limit boost? Two ways: Electronically via the ECU, and mechanically via a Waste Gate mechanism [Actuator + Valve] on the turbo itself.

7. The ECU constantly reads an electronic sensor at the Intake Manifold. The ECU is programmed such that if the voltage from that sensor exceeds the equivalent of ~23 psi, the ECU will put the system into ‘limp’ mode [restrict fuel, etc.] such that the pressure cannot go much higher than 15 psi. This allows you to get somewhere safe/reasonable in order to determine why things went ‘faulty.’

8. Since developing fault codes and going into ‘limp’ mode during ordinary driving is inconvenient at best – and dangerous in some/many situations – relying on the ECU to regulate the demands of everyday driving is bad design.

9. So, there is a mechanical Waste Gate Actuator coupled to a Waste Gate Valve in the system. If this pair is set up correctly, it smoothly and continuously limits the boost at the Intake Manifold [i.e., dumps exhaust gas in excess of what produces the designed set point] so that the pressure does not reach 23 psi and trip an ECU fault into ‘limp’ mode.

10. Both the ECU and the Waste Gate also limit the turbocharger from spinning up beyond its rpm and heat limits – it is after all operating ‘normally’ at above 100,000 rpm at a temperature of 1000-1200°F.

To come back to Overland Hadley’s question in Post #121: The WasteGate mechanism continuously regulates the boost pressure reaching the Intake Manifold so that the maximum designed amount of air [boost] is available for combustion consistent with the load on the engine. Unlike HP – which only develops to a max at a point in the rpm curve – the max boost pressure can come to its regulated max at a whole range of rpms, depending on the load [and throttle position] which the vehicle is experiencing, e.g., acceleration, hill climbing, heavy loads, etc. The way I think about it: The turbo is designed so as to operate at its maximum for relatively long periods of time and over a considerable range of engine rpms, as long as the load on the engine calls for it.

As an aside, on my engine:
A. As delivered: the WGA-WGV-Turbo combination topped out at 16 psig at the Intake Manifold.

B. Since Nov. 2011 the replacement unit has shown a top of 18 psig.

C. I have no way to determine in retrospect which part is responsible for the +2 psig difference.

D. However, I do know that the present turbocharger is able to put out up to 23 psig, as I can [by blocking the Waste Gate action] easily get the ECU to fault and my gauge reads right around 23 psig when it does. That is why I have concentrated on the Actuator as likely culprit.

E. I have determined that I can ‘adjust’ the pressure at the WGActuator so that I can increase the IM pressure to 22 psig [reliably below the ECU fault point.] Over 200+ miles of driving, including 12-pedal-to-the-metal hill climbs, implementing this ‘adjustment’ has not tripped the ECU into fault.

F. BUT… presumably an increase of 22% in turbo boost should have produced some performance improvement – which so far I have not been able to discern, either in relatively objective hill-climbing speeds or in the seat of my pants.

G. Having received confirmation of my un-tutored assumption from a genuinely expert turbo mechanic, I am now preparing to investigate the fuel side of the overall equation. This expert said I absolutely should expect a noticeable performance increase from a 22% increase in boost, UNLESS the engine is not being fueled sufficiently for an increase. And, of course, this may be how Mitsu has "de-tuned" the engine for longevity and reliability.

The problems are never simple, are they?! The real question is: how many layers deep is the solution?

 

[JRhetts]

John,
You can calculate the grade of your hill with a couple steps

Your instructions worked very well. I could not at first figure out how to place markers on the Google Map by simply clicking, so I used GoogleEarth to get the lat/lon for my starting point at the bottom of the hill and my ending point at the top. I entered those and then your instructions sailed me through.

Neat trick!

The grade for my 12 runs to test hill climbing at 18 psig vs 22 psig was 5%.

I really don't know what to say about the "Fast and Furious" pic. On the one hand, I'm pretty sure I can promise never to put "a big coffee-can exhaust pipe with 'Rad' graphics on [my] Fuso." On the other hand, I have to say you got it all wrong — I'm not bald, yet.

I laughed like hell when I saw what you had done!! Esp. the fine red print at the bottom.

John

 

[mog]

Your instructions worked very well. I could not at first figure out how to place markers on the Google Map by simply clicking, so I used GoogleEarth to get the lat/lon for my starting point at the bottom of the hill and my ending point at the top. I entered those and then your instructions sailed me through.
Neat trick!

A simple trick to place the markers were you want them is to just pick two 'named' points for the route, say Bend,OR and Redmond,OR and then 'Get Directions'. Once those points are there on Google Maps you can drag them (left click and hold) to were you want them and it will 're-route' as you do that.

 

[JRhetts]

A simple trick to place the markers were you want them is to just pick two 'named' points for the route, say Bend,OR and Redmond,OR and then 'Get Directions'. Once those points are there on Google Maps you can drag them (left click and hold) to were you want them and it will 're-route' as you do that.

Cool!! Thanks. John

 

[Overland Hadley]

Was it a dino on the dynamometer?

 

[JRhetts]

Dyno "results" and next ???? steps

Monday, Nov. 11, 2013

Monday, a friend and I drove 2.5 hrs over the Cascades to an established big truck center that had relatively recently become certified as a Fuso service shop. They said they had the proprietary Mitsu MUT-II test equipment and could monitor the engine while doing the load test on their dynamometer. But…
• Apparently they had never tried a Fuso on their dyno before; they found that due to the Mitsu proprietary bus, they were unable to control the Fuso engine from their control room; they had to do a ‘manual dyno run’; this was done behind closed doors, so I do not know exactly how/what was done.

• They reported only 4 data points for engine HP, at 51, 50,47, & 44 mph ‘road speed’ in 4th gear [1:1 transmission ratio].
• They reported no data about rpm at any of the HP data points
• They provided no calculation of torque at the various HP data points
• They reported no detail about what engine performance variables were monitored or recorded from the Mitsu MUT-II during the dyno test

Peak Hp power was reported to be 188 HP at 47 mph ‘road speed’ [from dyno rollers] in 4th gear.
[By my separate measurement, a GPS speed of 47 mph equates to 2480 rpm.]

Other than finding engine HP to be 77% of spec, and not addressing the OEM boost of 18 psi, none of the [unknown number of] variables monitored on Mitsu MUT-II during dyno test were reported out of spec. They did report specifically checking the exhaust brake, air filter, fuel filter, and [at my specific request] the throttle position sensor. Their report noted a 195° temp and 22 psi during the dyno run; they also reported ‘no SCA in coolant.’

Given what they characterized as “slightly low HP”, they consulted Mitsu corporate. Mitsu’s response was reported to me as: since the HP was only ‘slightly low’ and nothing was found to be faulty or broken, there is no basis for any warranty action on Mitsu’s part.

I’d have to say I was “a bit” disappointed.

 

[SkiFreak]

but I don't know how to get data on this stuff, especially since all the ECU data that is available is in a Mitsu proprietary format and it seems next to impossible to get my hands on the Mitsu MUT-II test equipment one needs to read the ECU.

You can buy Chinese cones of the MUT III readers online, but they are about $600. As far as I know, these are backwardly compatible to MUT II.