Turbo Diesel Register Tech: It's About the (fuel) Economy Stupid!

TDRAdmin4 · Sep 22, 2008

[RAW]<h3>This article originally published in Issue 61 of the Turbo Diesel Register.</h3>
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<div id="contact-info">TURBO DIESEL REGISTER 
1150 Samples Industrial Drive 
Cumming, GA 30041 
(770) 844-8877 

<h2>Technical Topics</h2>
<div>
Page: 1 2 3 4
</div>
<h1>IT'S ABOUT THE (fuel) ECONOMY STUPID!</h1>
by Robert Patton, Editor TDR
No, I’m not running for office this election year. But, with my knack
for the obvious, I know the focus of attention is fuel economy. So much so
that I could be accused of head-in-the-sand mentality were I not to acknowledge
that I’ve heard many conversations about parking the truck and purchasing
a beat-up economy car.
I’ve thought the same. Before you make a like
decision, be sure to factor all of the cost. You’ll likely find that
the beater car’s payback is longer than you first realize.
Nonetheless,
I wanted a quick solution to the fuel economy crisis. So, I went to Wal-Mart.
No
magic fuel magnets were found on the shelf. Out of stock.
The air tornado thing
was not large enough for my truck’s intake. The fevered pace with
which I started this article was now in neutral. If the fuel magnet or the
tornado salesman had come calling I would have purchased the products out of
sheer frustration. Maybe I should do some further research.
As I look back,
it was 10 issues ago (Issue 51) or the winter season of 2005/2006 that we had
the TDR writers tell us about their strategies for driving their diesel in
a $3 gallon world. This was just after hurricane Katrina, but prior to ULSD
fuel and the higher world wide demand for diesel. Diesel fuel was still lower
or equal to the price of regular grade unleaded gasoline. Diesel owners were
still pleased with their choice of engine and we enjoyed the benefit of the
engine’s 35% better fuel economy than the gasoline counterpart. Today’s
price premium for diesel fuel (about 20% here in Georgia) really hurts.
So,
I went back to Issue 51 to see how easy it might be to write a sequel article.
I was captivated by the writer’s stories.
Issue 51, like a conversation
with an old friend, is worth your reread.
• Doug Leno’s cost/benefit
analysis on fuel economy gadgets.
• Brad Nelson’s pinecone and
boost build-up driving technique.
• Bruce Armstrong’s EGT at 600° driving
technique.
• Greg Whale’s analysis of price versus Europe where
fuel was $6 for diesel and $8 for gasoline.
• Scott Dalgleish’s
fuel economy project truck and the connection of the wallet to the right foot.
• John
Holmes’ price of fuel versus minimum wage comparison.
• Jerry Neilsen’s
pledge to slow down and use the cruise control. Jerry also noted that “everything
is a matter of perspective.”
• Joe Donnelly points out the obvious
and refers the readers back to Issue 47.
• Mixed in with the fuel economy
comments you can’t miss the late Ron Khol’s tell-it-like-it-is
political commentary.
Throughout Issue 51 several writers made reference to Joe Donnelly’s “Fuel
Economy with Power” article in Issue 47. So I picked it up and searched
for information. Rather than reinvent the wheel (actually Issue 47’s
article was an update from Joe’s Issue 29 material), I’ll review
with you some of the Issue 47 text. The first thing that caught my attention
was the cliché often seen in the TDR, “The more things change
the more they remain the same.” As this bit of reality set in, it slowed
my fevered pace to find the key that would unlock a dramatic fuel economy breakthrough.
Regarding fuel mileage (and for that matter performance and exhaust emissions),
this bit of reality was presented in Issue 47. “Editor’s note:
you may say to yourself, ‘Gee, it looks all too simple…change
(advance) the timing of the fuel delivery (on the 12-valve engines this is
a mechanical change; on the 24-valve engines and HPCR engines many of the auxiliary
black-boxes do the timing change) and throw in a set of big injectors for better
mileage and power. Pretty simple, eh? Why didn’t those guys at the factory
do that?’ The answer is as simple as two words: exhaust emissions! Dodge
and Cummins have to play by a different set of rules than the owner of the
vehicle. It is true that tampering with or disabling any component of the emissions
control system (timing changes and big injectors are included here) is a direct
violation of federal law (fines up to $25,000 per day, per violation). Owners
have to weigh the consequences versus the increase in performance, and in this
example, fuel mileage (Issue 60, page 50).”
<table width="100%" border="0" align="center" cellpadding="0" cellspacing="0">
<tr>
<td align="center" valign="top">Automotive
Performance Curve 
<a href="images/IO61_FEimage1.gif">

#ad
</a> 
(Click on chart for larger image.)</td>
<td align="center" valign="top">Engine
Performance Curve 
<a href="images/IO61_FEimage2.gif">

#ad
</a> 
(Click on chart
for larger image.)</td>
</tr>
</table>
<div align="right">
Some other summary points from the Issue 47 text:
The article provided a
great refresher for 12-valve and 24-valve owners. Of particular interest
to all of the TDR audience is the discussion on brake specific fuel consumption
(BSFC) and volumetric efficiency (VE). We provided the performance curves
for an early Dodge 12-valve, 175 hp engine. We also provided a preliminary
performance curve for an early 24-valve (non-Dodge application) engine. Unfortunately
the Dodge-specific curves for the ’98.5-’02 engines were never
published for the Cummins network, as the Dodge engine is not an engine sold
through the Cummins distributor system. The same story holds true for the ’03-’08
Dodge-specific Cummins engines.
Regardless, we can all learn from the BSFC
and VE discussion and benefit by driving close to the engine’s BSFC
and VE “sweet spot.” For 12-valvers it’s 1600-1700 rpm;
for 24-valvers it’s 1600-2000 rpm; for HPCR engines it is a higher
1900-2100 rpm range as confirmed in discussions with Cummins Inc. engineers.
From
these performance curves I want you to focus on the bottom chart “Fuel
Consumption.” The measurement used is brake specific fuel consumption
(BSFC). In layman’s terms, brake specific fuel consumption is the efficiency
of an engine. The BSFC number is simply a value that helps us desribe the
engine’s ability to convert fuel into horsepower.
BSFC tells you how
much fuel it takes your engine to produce each horsepower. The lower the
BSFC value, the greater the fuel efficiency: Fuel consumption (gallon/hr)
= (BHP x BSFC) Ö 7.1 lbs/gallon fuel.
[PAGE][/PAGE]
p class="columnheader-red">Been There, Done That; Got Lots of Spare Parts
As much as I would like to
pretend that I am a diesel engineer and offer you a magic fuel economy fix-all,
the reality is that as a group we have already been there and done that. So
much for the sensational title line that I could splash on the outside cover, “Writer
Dude Discovers 25% Greater Fuel Economy for His Dodge/Cummins Turbo Diesel.”
Back
to the task at hand, can you increase the fuel economy of your truck? Oddly
enough Issue 51 was the second article in Scott Dalgleish’s quest to
improve the mileage on his ’05 Turbo Diesel 2500, 4x4, Quad Cab with
the G56 six-speed transmission and 3.73 rear differential ratio.
Rather than
send you back to your archives to gather the information, I’ve assembled
a brief summary of each of his articles.
Read the summaries and let’s
see if we reach the same conclusion(s) at the end.
Issue 50 Baseline MPG 15.8 city;
9.8 towing. 
Added TST PowerMax CR, Amsoil synthetic lubricants, Mag-Hytec differential
cover, gauges, fresh air box with aFe Proguard 7 filter. Notes: Playing with
different timing settings the TST PowerMax CR showed an increase of up to 13%
better mileage.
Issue 51 Added Gear Vendors overdrive, Banks High Ram inlet,
Banks intercooler, Banks Monster exhaust. The combined effect of the aftermarket
products thus far: up to 17% better.
Issue 52 Added BFGoodrich 285/70/17 tires
which reduced engine’s rpm by 100. Experimented with pre-production Banks
Six-Gun Tuner and Power PDA. The combined effect is still in the 16-17% range
with the power setting on the Banks unit at “2.”
This comment caught
my eye: “Power settings above 2 provide marked performance increases
along with an equal increase of driving fun. But the fun has a cost and decreased
fuel economy is the price.”
Scott is about to “go over to the dark
side,” “fall off the wagon”; choose your cliche. This article
was written in the May 2006 time frame when the pre-Katrina fuel price is at
a stable $2.25.
Issue 53 No report.
Issue 54 Recap of baseline at 15.8mpg. Noted increase
of mileage to 18.7mpg. Added Industrial Injection Super Phat Shaft 62 turbocharger
and PDR camshaft. Scott noted that the turbocharger neither hurt nor helped
fuel economy.
I told you Scott had moved to the dark side. Notice the emphasis
on performance: “The setting of the Banks Speed Loader was 6 and the
0-60mph time dropped from 10.2 seconds to 8.9 seconds.
In the Issue 54 article
Scott noted that the PDR camshaft had a dramatic effect on economy—approximately
2.1 mpg. Great news! But, why didn’t the Cummins engineers think of that?
They
did.
Scott’s explanation from Issue 54: “If obtaining better
fuel economy can be found from a different cam grind, why didn’t Cummins
do it?” The answer is Cummins Inc. can provide camshaft grinds for better
fuel economy. But, as I stated earlier, Cummins has to abide by a different
set of standards, which are primarily emissions driven. (Editor’s
note: Sounds familiar, doesn’t it?) In order to meet current
NOX standards, combustion cylinder pressures must be lowered. One way to accomplish
this goal is to retard injection timing, reducing cylinder pressure and thereby
reducing NOX. The Catch 22 is that it takes more fuel to operate the engine
in this manner. The engineer has to certify clean exhaust emissions, often
at the cost of fuel economy. So will the cam offered by PDR meet EPA emission
standards? To our knowledge it has not been tested for EPA compliance and probably
would not pass. Would it pass a local emissions test as administered (snap
idle)? Probably.”
Issue 55 Scott is to the point: “In my review of some
of the back issues I realized I have made a transgression. I have once
again, fallen to the temptation of more power. While it is true we are close
to accomplishing our goal of 20% better fuel economy across the board, the
alluring power increases have blinded me like a moth drawn to a bright light.
I now believe that it is possible to obtain the 20% fuel economy goal AND increase
horsepower to the 500-rwhp mark. Along with this revised goal I had to accept
the reality that was true for me way back in Issue 23, the financial impact
of all of these fuel mileage and performance goodies will never be offset by
the 20% economy I may someday achieve.”
Further, Scott writes, “This
isn’t
to say I have forsaken the fuel economy project. Currently we are averaging
about 18.1 mpg. That is approximately a 15% increase across the board (solo,
towing, city and highway). We have produced as much as 18.8 mpg driving solo
combined city and highway, which is a 19% increase! But we have shifted from
some of the original stated criteria. Most notably, ‘to remain emission
compliant and to maintain the factory warranty.’ Some of the parts we
have tried may not be emissions compliant (no current emissions testing data
is available) and their effect on warranty is subject to debate.
“Knowing
this up front, you are faced with a dilemma. Will you a) live with the fuel
economy offered by the current HPCR engine’s configuration; b) make some
of the changes which provide some fuel economy improvement and leave the engine
warranty intact, or c) become your own warranty station and move in the direction
which will provide the best fuel economy and performance available?
“On
the topic of emissions compliance: most, if not all, of the products tested
to date will pass the current snap-idle emissions testing which is performed
in some states today. Would these products pass the current Federal standards?
Probably not. We do not have access to the test equipment nor is there a standard
procedure for such testing after a product is sold to the end user. Since no
testing of the Federal emissions standard (EPA or CARB) is currently in place
(the exception being for manufacturers), it is a moot point.".
TDR members, if you reference Issue 60, pages 50-52, you will likely conclude
that parts testing for emissions certification for the ’03-’07
HPCR engine is still a moot point.
Issue 56 Noted a decrease in mileage of 7% that
was attributed to the required ULSD fuel (January ’07). Added DDP injectors
and mileage checks in at 18.9 mpg.
Issue 57 Added Leer truck cap, but noted no
difference in economy.
Issue 58 Changed turbocharger to a Turbo Re-Source unit.
Mileage is 19.1 using Scott’s combination solo runs on the short and
long track.
Issue 59 A higher performance set of DDP injectors (DDP90) and an emphasis
on horsepower. Fuel economy went down 6%. Overall economy is better by 14%
Issue
60 No report.
Issue 61 See Scotts turbocharger write-up on page 92.
Conclusion(s)
Credit to Scott—in his adventure seeking fuel economy
and performance, he took the time to address three important concerns: Why
didn’t the factory engineer for fuel economy? What happens to emissions
compliance? What are the effects to the factory warranty?
As I looked back
at his findings, there was one modification where I could see a cost justification
and two nice-to-have modifications.
The item that can be cost justified: The
use of a performance box that modifies the timing of the fuel injection event.
Cost: $800. Number of gallons that you would need to save (@$4/gallon) to payback
the $800 ($800 &#247 $4 = 200 gallons). From his Issue 50 Scott found that
the mileage increased by 13% or 15.8 x 1.13 = 17.8 mpg.
<table width="450" border="0" align="center" cellpadding="3" cellspacing="0">
<tr>
<td width="300" align="right">Drive
30,000 miles &#247 15.8 mpg = 1,898</td>
<td> gallons
used</td>
</tr>
<tr>
<td width="300" align="right">Drive
30,000 miles &#247 17.8 mpg = 1,685</td>
<td>gallons used</td>
</tr>
<tr>
<td width="300" align="right">213</td>
<td>gallons saved</td>
</tr>
</table>
Okay…drive the truck 30,000 miles and you’ve
paid for the performance/timing box. The nice-to-have modifications: The camshaft
and the overdrive unit. From Issue 54 Scott noted the cost of the cam and installation
was $1600. He noted a 2 mpg increase. Yet the 2 mpg was lost (the numbers should
have gone up to 19.8 mpg) in his quest for power. But, for the sake of argument,
let’s assume another 2 mpg improvement. At $1600 &#247 $4 gallon you
need to save 400 gallons of fuel to pay for the camshaft. This would take 60,000
miles. And the nice-to-have overdrive? Writer Loren Bengston covered the payback
for his overdrive unit back in Issue 47, page 162. In Scott’s case insufficient
data exist to do a calculation.
Bottom Line 
It seems simple to me…
• As we learned from Joe Donnelly and Issue
47, operate the engine at the BSFC rpm that corresponds to the engine’s
sweet spot. Unfortunately, highway speeds don’t allow you to go that
slow without impeding traffic, so slow down as much as possible.
• Change
the engine’s timing. Scott’s findings and the article by Joe Donnelly
on page 98 confirm that this modification is applicable for all years of the
Turbo Diesel truck. Be careful of the cause and effect and realize that the
payback could take a while. • All of the other modifications are discretionary.
P.S. Wal-Mart is still out of stock on the fuel magnets and
the tornado thing still has not been released for our intake size.
[PAGE][/PAGE]
VENDOR RESPONSE TO THE NEED FOR TEST DATA 
Realizing that there was limited data to substantiate the timing cause-and-effect,
I sent a letter to several vendors that were listed in Issue 47’s and
48’s articles on performance for the ’03-’07 HPCR engine.
The articles were authored by writer Doug Leno and Doug provided a comparison
matrix that showed vendor products that effected timing.
Doug’s write-up
(Issue 47 and 48) was done in mid-2005. Since that time there have been numerous
other products introduced to the market that effect timing. I was remiss in
not asking those vendors to respond. Admittedly, I am belated in keeping tabs
on the performance marketplace.
The following is the letter that was sent to
those vendors of record in mid-2005 whose products effected timing and the
responses that were received:
In Issue 61 the obvious topic for
the TDR will be, “It’s the (Fuel) Economy, Stupid!” We
are planning a story on fuel economy and we would like to include your input
in this article.
I
plan to poke fun at myself with an exaggerated story about out-of-stock fuel
magnets and the Tornado-thingee that does not fit our diameter air intake.
The
serious stuff starts with this disclaimer: “Numerous times I have
been cited for not including a legal disclaimer prior to an article that discusses
a performance gadget, gizmo, or modification. Make no mistake: changing the
timing of fuel delivery is a modification that can put your rights to warranty
consideration into serious jeopardy. Additionally, timing changes must not
adversely affect emissions according to the Clean Air Act, Section 203(a) and
EPA Memorandum 1A.”
This disclaimer will be followed by Joe Donnelly’s “How-To” material
on fuel pump timing for better fuel economy. Joe covers the mechanical VE and
P700 fuel pumps, taking us up to the advent of electronics.
At this point it
becomes subjective with comments from writers, “I think…
”So,
I will jump on the band wagon. I think timing (either mechanical advance or
electrical) is the magic bullet for Dodge/Cummins owners to consider in their
quest for cost-effective mile-per-gallon gains. Have I missed the mark?
Thus,
the purpose of this correspondence is to allow you and your company a forum
to present any fuel economy data you may have on your VP44 and HPCR boxes.
To keep the correspondence on track, I have provided a Question & Answer
format below. I would appreciate your responses to these questions.
I received
a response from TST Products’ Mark Chapple and MADS Electronics’ (Smarty)
Marco Castano. Their answers make up the balance of this article. 
Is fuel injection
timing a “magic bullet” or is the editor off-his rocker?
TST Products’ response: I don’t see it as a
magic bullet, but I believe there is a definite trend. As emission laws get
tougher, manufacturers retard timing to reduce NOX. The reduced NOX comes from
lower cylinder pressures and temperatures, but this is the opposite condition
one would want for best fuel efficiency.
<hr width="400">
But this is the opposite condition one 
would want for best
fuel efficiency. 
<hr width="400">
MADS Electronics’ (Smarty)
response: I’m sorry to say, timing alone is not the “magic
bullet.”
Let
me expand.
The mechanical VE and P-7100 injection pumps have a preset and fixed
value for the “beginning of the injection stroke.” This means that
the preset timing is optimal only for a rather narrow RPM/load range of the
engine.
Since the introduction of the first “real” emissions regulations
(NOX, HC and PM emissions) all engine manufacturers were forced to introduce
electronic engine management. The introduction of electronic control modules
provided a much more refined control over the injection timing. Electronic
engine management provides the ability for dynamic timing changes throughout
the RPM band. Therefore not only RPM, but parameters like engine temperature,
boost pressure, intake air temperature, etc., can now be taken into account
to adjust the timing of the engine. Were there no such thing as emissions regulations
the electronics could provide the “perfect” timing for the engine.
Thus
the best possible mileage? Unfortunately, the world is not a perfect place…
<hr width="400">
Were
there no such thing as emissions regulations 
the electronics could provide
the “perfect” timing for the engine. 
Thus the best possible mileage?
<hr width="400">
In
order to reduce the combustion temperature thus NOX and PM emissions one simple
way is to retard the timing. Furthermore, for the emissions test(s) the low
load/low RPM range is weighted more than, let’s say, wide open
throttle. That means the high load/RPM range is less important from an emissions
point of view.
This leads to what’s under our eyes or should I say right
foot? Detuned/sluggish engines in the 600-2000 RPM range. Range where we use
them most! Detuned because of the emissions. Sigh!
This is of course counterproductive
from the mileage point of view in a Diesel engine! As you surely know, the
diesel engine is most fuel efficient in the lower RPM range; typically the
best BSFC is yielded, which happens to be around peak torque.
Then faster the
engine gets into the peak torque range then better its fuel efficiency in the
real world. This is where the timing really comes into the picture! Correct
timing means an engine that’s more willing to gain the revs. Thus we
get sooner to the best fuel efficiency range.
<hr width="400">
This is the real reason why most customers report 
mileage gains with their power modules.

<hr width="400">
Although, the timing is retarded
typically only 1-2 degrees for the emissions (also Cummins has to make sure
to deliver the best possible mileage. What about a new word? Emissions possible
mileage?) which leads from my findings to a 1.5-2% mileage loss.
To come to
a conclusion. The timing alone gains about 2% mileage. This nets out to nothing
that could be measured in the real world! Yet, the timing (engine responsiveness)
combined with increased fueling in order to get into the best BSFC range as
soon as possible is what really gains mileage!
This is the real reason why
most customers report mileage gains with their power modules. They get to the
RPM range sooner and can stay longer where the diesel engine is most fuel efficient.
Do you have a mechanical timing recommendations(s) for ’89-’93
VE fuel pumps? The expected mpg benefit?
TST: The ’89-’03 engines
didn’t have to meet as strict emissions rules thus the timing was left
in a position for fairly high in cylinder temperatures and pressures. Timing
changes would have very little effect on mpg.
MADS: No.
Do you have a mechanical
timing recommendations(s) for the ’94-’98 P7100 fuel pump? The
expected mpg benefit? Data?
TST: Timing was retarded more in ’94 to meet
the NOX laws thus advancing timing had more effect on mileage. Though we didn’t
make dyno runs at constant horsepower to measure fuel economy on our 12-valve
truck, my log-book mileage appeared to improve by 3 to 5% once we advanced
timing from about 12.5 to 15.5 degrees BTDC. This lowered exhaust temperature
a bit at a constant power, and made the engine rattle more.
MADS: No.
Please
share your timing experiences with the ’98-’02 VP44 fuel system
and your performance module. The expected mpg benefit? Part number to be used?
Settings for best mpg? Data?
TST: The ’98.5-’02 trucks with the
VP44 pump had even more retarded timing than the ’94-’98 trucks
to meet an even lower NOX standard. We used computer tools to change the numbers
in the ECM timing tables and again lowered exhaust temperatures and picked
up 3-5% fuel economy in our log-books.
MADS: Reported mileage gains with the
Smarty S-03 are in the 1 to 3 mpg range. And, although I would like to believe
in a 3mpg gain…I have never experienced it personally in my daily driver(s)!
I’ve found that a 1 to 1.5mpg increase sounds more reasonable. There
is no such thing as “best” setting for mileage. Everything depends
upon driving style and conditions. This is why we strive to deliver to most
flexible tuning system possible. “One size fits all” just can not
do the trick.
Please share your timing experiences with the ’03-’07
5.9-liter HPCR fuel system and your performance module. The expected mpg
benefit? Part number to be used? Settings for best mpg? Data?
TST: We ran dyno tests with
various timing on our ’03 Ram and gained about a 4% improvement in fuel
economy at 55mph, up to a 10% gain at 75mph. Book mileage jumped 2-3 miles
per gallon on this truck for a 10-15% gain.
MADS: The answer is the same as
my response to the question about the VP44 fuel system. The product that should
be used in HPCR applications is the Smarty S-06 or SJ. 
[PAGE][/PAGE]
VENDOR RESPONSE TO THE NEED FOR TEST DATA 
Your closing comments:
TST: TST has been in the business of increasing power
and torque for a decade. Up until 2006 about 90% of incoming started with, “How
can I get more of that power and torque stuff?” Then, almost overnight,
the question became, “How can I get more mileage out of this big beast?”
Power
and torque increases were always easy for us to measure as we test on our own
chassis dynamometers. Typically, we would leave one of our test trucks on the
dyno for 6-8 weeks at a time, daily trying a program change or parts change,
and let the dyno tell us if the engine liked or disliked the change.
My first
job in Cummins engineering in 1966 was keeping track of hundreds of test semi-trucks
running without ever changing motor oil. Monthly, I would have to pull oil
samples on each of these trucks, record mileage, any oil addition since the
last check, and document the results of the oil analysis tests. I started keeping
record books on my personal vehicles at that time, recording every event, fuel
fill, oil change, new tires, etc. As a part of the personal record keeping,
I’d calculate the mileage at each fill and noticed how the mileage constantly
changed tank to tank. I’ve continued this practice to present day with
my diesel trucks, keeping Excel spreadsheets to show each tank’s mileage,
running average, and change in fuel cost. Carefully filling the tank to the
top, with the aid of a tank vent kit, still did not eliminate the variation
tank to tank. My Excel spreadsheets (and your notepad and pencil) are good
for long-term trends, but I view them as consistently inconsistent for short-term
evaluations.
With customer requests for better mileage becoming the number
one priority, I spent many hours wondering how TST could evaluate fuel economy
without burning several tanks of expensive fuel. I recalled my experience in
the Cummins Engine research labs where we often monitored the fuel consumption
of running engines without the hindrance of an attached vehicle. All engine
manufacturers gather data to calculate brake specific fuel consumption (BSFC)
in order to compare the relative economy or efficiency of various engines.
Typically an engine would be run for several minutes at a constant brake horsepower
and the fuel used was measured in pounds. The word brake in this case meant
the engine dynamometer which measured flywheel torque and engine rpm such that
engine flywheel horsepower could be calculated. A simple calculation could
be made with the gathered data by dividing the weight of the fuel used in pounds
per hour by the horsepower being generated. BSFC number like 0.350 pounds per
horsepower per hour was the end result. A very good engine might run a 0.330
BSFC while a poorer engine might run close to 0.410 BSFC.
I felt finding a
BSFC-like number for a Turbo Diesel would be a good way to check the relative
fuel consumption. I knew our chassis dyno could be set to measure the horsepower
at the wheels. But at what horsepower did we need to run the tests? The TST
staff brainstormed the question and decided we needed to determine the actual
horsepower it took to move a Turbo Diesel pickup at various road speeds. We
took our ’03 Dodge Ram out on the Interstate highway and ran it for several
miles in both directions while recording instrument readings for air temperature,
mph, gear selected, turbo boost, egt, rpm, and rail pressure. We gathered data
for road speeds from 55 mph to 75 mph, in 5 mph increments. We then tied that
truck to the chassis dynamometer and tried various loads until we could reproduce
the instrument readings we took out on the Interstate. This gave us a horsepower
value to use in our fuel economy tests for various road speeds. (See figure
1.)
<div align="center">(Click on chart for larger image.)<a href="images/IO61_FEimage3.gif">

#ad
</a>
Figure 1</div>

Next, we needed a way to accurately measure the fuel used during our testing.
While we considered trying to carefully refill the stock Dodge fuel tank after
each run, we quickly discarded that idea because it was impossible to fill
that tank to the same level each time. We also considered placing a small tank
in the bed of the truck that would be easier to refill to the same level each
time, but that still left us with the problem of measuring just how much fuel
it took to refill the tank. Suddenly it became obvious, let’s run the
truck using a remote fuel tank that sets on a very accurate scale and simply
weigh the fuel as it is consumed. By carefully weighing a gallon of fuel, we
could then determine the number of pounds per gallon. We could then use this
pounds-per-gallon number to convert our pounds of fuel used back to gallons
for the mpg calculation. This is the procedure that is used by Cummins in official
ASE-type testing of big rigs at fleet accounts. We purchased an electronic
scale with a digital readout that was guaranteed accurate to one hundredth
of a pound and used a transparent five-gallon plastic jug as our fuel tank.
We unhooked the quick connects from the truck tank and plumbed them such that
the engine would draw and send its return fuel to the plastic jug (See picture
below).

#ad

Figure 2
Ready to start
testing? We thought so. We brought the truck up to 55mph on the dyno and set
the truck cruise control to hold the speed. That part worked great. Next we
started increasing the load on the dyno until we could repeat the horsepower
number we found from the earlier Interstate highway testing. That part worked
great too. Then we drove the truck for five minutes at these conditions taking
the fuel weight before and after the test. That part worked great too. Well,
almost. One of our technicians accidentally touched the five-gallon jug and
realized it had become very hot from the engine’s returned fuel.
It took
about four hours to add 50 feet of copper tubing to our return fuel line. We
dropped that copper line into a large cooler and returned the fuel to the plastic
jug. We then used a garden hose to run cold city water through the cooler to
keep the returned fuel cool. By regulating the city water flow we could maintain
the fuel temperature at a usable level.
We were ready to start testing again.
This time we were able to repeat the weight readings time after time during
the five-minute test. We now felt we had a way to quickly and accurately determine
how various engine changes would affect fuel consumption.
Back in 2002-2004
we developed the PowerMax CR for the 5.9 HPCR engine. We engineered a way to
vary injection timing, injection duration, and rail pressure on the fly. Of
course our motive was different back then; we were after the most power and
torque at the lowest exhaust temperature. Now with a new goal of best fuel
economy, we started all over again trying to optimize timing, duration, and
rail pressure.
<div align="center" class="smalltext">(Click on chart for larger
image.) </div>
<a href="images/IO61_FEimage5.gif">

#ad
</a>
<div align="center">Figure 3</div>
First we determined the fuel consumption curve for the stock
engine using our new measurement method. (See lower curve in figure 3.) The
mileage numbers from this test were quite a bit better than our record book
showed for this truck, but keep in mind that our new test method was steady
state only, no starting and stopping. I figured if we could improve the steady
state numbers, mileage would also improve on the highway.
To start, we tried
the injection timing schedule from the PowerMaxCR that gave us the best power
curve. That timing helped fuel economy a bit, but not a significant difference.
Over the next few hours we tried many different injection timing settings and
selected the ones that gave us best economy from 55 to 75 mph. (See upper curve
in figure 3.) We then tried varying the rail pressure while using only the
best timing found earlier. Changing the rail pressure didn’t help.
We
added an “Economy” setting to the PowerMaxCR as a result of these
tests. To date, customer experience has been mixed. Some claim big gains like
3 to 4mpg, some report no change at all, while a few claim they lost mileage.
How could this be? Looking back, all testing was done on the same truck. The
truck was a ‘03 Quad Cab, 4x4, SRW, long bed, six-speed manual, 3.73:1
axle, stock BFG tires (LT 265/70 R17). The only modifications to the truck
were cab high full length cap, FASS HPFP 95 gph pump, and a South Bend Double
Disc clutch. I felt the FASS pump and SBC clutch had no affect on the mileage
test, but were needed on the truck for full power testing done separately.
What
next? Let’s run the rail pressure box but with stock timing. Bigger
injectors get the fuel in quicker, so do they help the same as advancing timing?
How about a 48RE automatic truck? Is there any difference in the behavior of
the ’04.5 HPCR engine with its 325hp? I’ve got a 6.7-liter chassis
cab to test. Then there is the 6.7-liter pickup with the terrific new 68RFE
six-speed automatic. What? You want me to run an ’89, too. It doesn’t
end, does it. Maybe next issue!
Mark Chapple 
TST Products[/RAW]

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