Snorkels

I had trouble towing my new 1900 pound trailer from BC with my 00 XJ 4.0L Auto. Downshifted often on the flats trying to hold 60 mph. I only have 50,000 mi on my engine, run 91 - 92 octane, Jet Performance chip, which gets me 0-60 in 1.1 seconds less at 3500′ elevation, than without. Have cold air via Safari Snorkel, 2.5" exhaust, my exhaust manifold is the newer type and I’ve heard it’s as good as a header, still have a cat but have heard that maintains torque, 62 mm TB w/spacer. Running 35" Creepy Crawlers, heavy bumpers, D 44s, 4.88s, RE Long arm 5.5". Thought of trying to run smaller tires for towing but would still have to carry an extra 500 pounds of tires & wheels for wheeling, and gearing would be off.
Got to do something. I’m a bit secluded in a small town and don’t need a set of problems with the complicated set up of a supercharger and finding a local enough shop to count on dialing in the problems or returning far for troubles. Stroker sounds good. Need torque.

That subject comes up often…..

"Need More Power for Towing"

That’s not as simple as it sounds,,,,
and Nowhere Near as simple as trying to improve general performance,,,"drag strip times",,"more speed" etc

Most POWER ENHANCEMENTS make the towing probs WORSE.

The Reason is literally Centered on TORQUE PEAK….
and the RPM at which that occurs.

Most "Hop Up Measures" increase Horsepower/Torque at a Higher RPM….
OR they Increase Torque /HP at SAME RPM.

I Know You aint towing your trailer at 100mph.
And You Dont wanna tow it Locked in 2nd Gear at 50mph either.

I also know you’re Towing UNDER-REVVED relative to your set-up’s Torque Peak.

While Cruising at a Steady RPM,,with a "fixed throttle position",,,Any extra Load such as an incline,,or a headwind will demand stepping on the gas to maintain speed.
So You’re doing as much Throttling as you are Towing,,,just to get down the road.

Look at this chart,,,and the TORQUE CURVE.
Call it a "Camel Hump".
It’s Not Your Engine,,Only an Example.
But it’s Typical,,,almost "Universal" in representing the Relationships between Torque Rise & Fall and RPM
(I wish I coulda found a more exagerated chart to illustrate the point)

http://www.compcams.com/Technical/DynoSheets/XE256H-10_001.asp

Ok,,it begins at 2000rpm
and it Peaks at 4000rpm
AFTER 4000 it drops Off Sharply.

That’s the Behaviour & Characteristic of "ALL" engines.
Internal combustion Reciprocating engines(car engines).

The Figures and the SHAPE of the "camel Hump" vary widely,,
but it’s all still just a Hump.

Now picture Yourself Driving along that Chart.

If you are Driving at 4000rpm–the PEAK,,,and you meet some resistance,,,What Happens?

Resistance is things like a Hill,,or a Headwind that you come upon while Cruising along .
Even a small rise,or incline in the road,,,and Bridges,overpasses,etc.

Engine gets increasingly Loaded,,and wants to slow down.
Your Throttle Position Must be Opened Further,,
to intake more air in order to make More Power to Overcome the extra resistance.
And that’s only to Maintain Your Speed at 4000 RPM.

The RESITANCE and resultant RPM DROP pushes you Backwards on the TORQUE SCALE towards Lower RPM.

Look at 4000’s Torque Number,,,compare it to 3900,,3800..3700 and so on.
That particular Chart is rather Flat in that RPM range.

But what You can see is the the Increased LOAD & resulting RPM DROP is met by WHAT Level of TORQUE??
It is the SAME or LESS.

From 4000,,,as the Load begins to Drop RPM,,,
Your TORQUE is ALSO Dropping.

The Slower it Goes,,,The Weaker it Gets,,,and the Slower it Goes.
Until you feed the engine more air with the Throttle and actually try to ACCELERATE under Low Vacuum/Hi Load back up to 4000RPM Cruise.

So When the engine senses the rising Load at a Given Throttle,,,
it Falls BACK rpm-wise,,,into a WEAKENING Torque figure.

Your forward motion is getting DECLINING SUPPORT from your Torque Output.
……………………………………….
Look again at the Chart,,,at 3000 RPM.
If You were Cruising at 3000,,,and faced any increased Load from incline,wind,etc……
And engine slowed down in response to that load…..
Look at what the TORQUE does from 3000rpm Downward.
TORQUE Falls off a Cliff!

During a 3000 rpm cruise on our Example Chart,
Right when You need it Most,,,as RPMs begin to Drop from the load….
the TORQUE just begins Plummeting.

Your actual current vehicle set-up is Operating in a Torque Range,,,
which is equivalent to 3500~4000 RPM Characteristics of that EXAMPLE CHART.

There’s No Tellin’ what YOUR ACTUAL Graph looks like—
but You are running in the FLAT or even the RISING part of your Jeep’s Torque Curve.

So You are expereincing either
a) SAME TORQUE
or
b)FALLING TORQUE
..anytime You meet a RISING LOAD & RPM’s begin to drop.

So You gotta keep giving it more throttle to maintain your speed.
Or Downshift and raise RPM’s to a whole new range.

It’s WEIRD,,,and this is what many,many folks dont realize.
You can actually be AT or IN the Peak Power Range Torque-wise….
And be Cruising along at MAX POWER,,,
But Your Motor cannot take any confrontation without WEAKENING.

It gets sorta Cowardly,,,
It’s Happy to Cruise along but Shys away from ANY Increased load.

That’s NO Jab at the Jeep!
A 1500 Horsepower engine 4 times the size of yours can do exact same thing.

It’s NOTHING about any TOTAL FIGURE,,
All about the CHANGE in Output at a given throttle setting.

You can start a BEAST of a Puller up a hill at a steady throttle position,,,,
,but if it is in "wrong RPM" of it’s Torque Curve as engine slows from the Slight Increase in Load
it will DROP in Power.

Whether 10HP,,100HP,,or a 1000HP,,,
They all have the same characterstic & behaviour.

…………………………………..
Now,,Look back at the Chart.
"You are Cruising at 5000 Rpm this trip"

You come upon the same ol’ hill that always slows you down.

Look what happens to your TORQUE at 5000rpm,,,
when engine gets Loaded and slows down to 4900,,,4800,,4700
and so on.

Without Changing your Throttle position to Increase Power,,,
JUST THE Road/Load Resistance trying to SLOW the RPM,,
RAISES POWER.

Try to Slow it Down with a Load Increase from an incline,wind,etc….
And Engine’s Torque RISES.

Thats Right,,Engine Responds to the extra Load by AUTOMATICALLY Increasing POWER every single rpm it drops.

Imagine towing your trailer at a steady speed/steady throttle,,,and starting up a small incline.
And as Your RPMs begin to DROP from the rising Load….

A) Your Engine LOSES Power—the Slower it Goes,the worse it Gets
or ____
B) Your Engine GAINS Power–the Slower it goes,,,the MORE POWERFUL it gets

If it seems Bizzare or Confusing,,,Look back at the Chart at 5000~5500 Rpm.
See the TORQUE RISING backwards towards the PEAK as RPMS Recede from 5500 downwards to 4000rpm torque peak.

Kinda a No-Brainer as to which would be a Better Towing Vehicle.

…………………………………
If you got a grip on the Behaviour of an engine Cruising at Steady Throttle–then facing an increased load,,,,,
and how that acts & responds on Either side of the TORQUE PEAK….

Then You can understand what I meant way back towards the beginning about running along the hiway "UNDER-REVVED"

You’re driving BELOW the Torque Peak,,,
and extra resistance will DROP engine power.
And Require an increase in Throttle to compensate.
Or,,require a Downshift

That’s the reason why Lower Ratio Axle Gearing,,,
or Downshifting to a lower gear allows a vehicle to apparently Tow a load "stronger" under Cruise Conditions.

Simply because the RPM’s are HIGHER—
Higher Enough to have SURPASSED the TORQUE PEAK.
Thus when Engine trys to slow down under extra Load,,,POWER RISES.
It Fights Back….all on it’s OWN…automatically.

………………………………………….
Need MORE POWER,,or TORQUE???

Well,,You already got ENOUGH to get it up to speed.
And enough to CRUISE at legal speeds.
And enough to even Accelerate from Legal Cruising Speeds.
True?
Got enough Power Already to go WAAY TOO FAST to be pulling a trailer.

No Matter HOW MUCH Torque or Power you have at STEADY THROTTLE CRUISE,,,,,,
ANY extra Load WILL DROP RPM.

Because A GIVEN THROTTLE SETTING can Only Support a Given Load at a Given Speed.
Whether engine is making 10 Hp or a 1000Hp.

Increase the DEMAND on the engine,,,,RPM will DROP.
How dramatic the INFLUENCE of the extra load PER-GIVEN-THROTTLE POSITION
All Depends on Which Side of the Torque Curve you’re on at that point.

If You’re PRE-PEAK so that any RPM Drop yields FALLING Torque,,,the Effect is the SAME.
Whatever the LEVEL of Power happens to be.
10hp>9hp>8hp is the exact same effect as
1000>900>800.

A Decline from "Status Quo" at the particular moment on the road,,,,is a Decline-Period

………………………..
Consider this when seeking,or doing Power Mods…..
Vast majority of Mods RAISE Power/Torque/HP.
Duh:)

That’s fine,,,,but the IMPORTANT Consideration is HOW it raises it.

Go Pencil in a Zero behind every Torque number on our Example Chart.
Make 400 Ft/Lbs of Torque become 4,000.
BUT ,,Do Not Change the SHAPE of the CamelHump.

Is it gonna Act any Differently,,,under Steady Cruise?
Under Peak is Under Peak,,,regardless of the Total Number.

No matter How Big the NUMBER is ,,if the engine is Cruising
at Slower than the Torque Peak,,,,
Any Drop in RPM results in "Power" sliding Back DOWN the Scale.

MODS,,,,either act like that—They RAISE the NUMBERS
VERTICALLY.
You pay for More Fuel to get that increase in NUMBERS,,,,
But the VEHICLE Acts Exact same Way under CRUISE /TOWING conditions.

It is only Falling off a "Higher Cliff",,,Power dropping from a Bigger Number.
Which has not improved Steady Cruise ANY—Regardless How much the TOTAL Power has increased from any Mods.

The Engine still YIELDS at Cruise to any extra load.

OR,,just as important ,,,to any RPM drop from Any Cause.
Such as "Fidget Foot"—a "slip of the foot" on Gas Pedal that allows even a few HUNDRED RPM Drop to INSTANTLY fall in Power.
Starts a Spiral Downward–You gotta RESUME previous Position,,,and Overcompensate with MORE PEDAL to Regain the few 100 Lost RPM.
Because You are then accelerating back UP with LESS POWER per-throttle opening.
All just to get back where you Were.

Or WORSE,,,and Most Mods do THIS…..
They RAISE the RPM at Which Torque Peak OCCURS.

That’s Exact OPPOSITE of what You NEED to solve the "towing prob"….RIGHT?

We wanna cruise down the road towing a heavy load while Engine is running at an RPM BEYOND Torque Peak.
So when confronted with any extra load,,,Engine Pulls HARDER as it slows.

If we RAISE the TORQUE PEAK RPM in quest for a Larger TOTAL NUMBER,,"More Power"….
Then we’ve gone from —-
*Towing "WEAK" at 70MPH
*But "Strong at 90MPH"

to Then a condition of—
*Towing GUTLESS at our old weak-ish 70MPH point
*Towing WEAK at the old "strong 90mph" mark
*To NOW Towing Strong only at 110MPH and above
‘Cuz we RAISED the TORQUE PEAK

It will ACCELERATE FASTER,,
It will GO FASTER.
It will be BETTER in a "Tractor Pull type of Acceleration Contest".
‘Cuz it’s then got more TOTAL POWER.
And will PULL Harder,,Farther UP the RPM Scale.

But Cruising down the Hiway,,,is gonna be WEAKER and WORSE.
Cuz our new "Power Mods" that Gained Total Power has Pushed the PEAK even HIGHER ,,RPM -wise.
Unless we drive at Crazy towing speeds,,,or in 2nd Gear,,
We Can’t get PAST the Peak to be able to CRUISE STRONG.

There’s 3 BASIC DRIVE MODES
1)Acceleration
2)Part-Throttle CRUISE
3)WOT/Wide Open Throttle>Top Speed/Max RPM

More Power will Enhance #1 & #3.

But almost Anything you do to improve THOSE Modes will WORSEN #2—Part Throttle Cruise.
Understanding "all the above" defines WHY that is.

”””””””””””””””””””””””’
Many,Many Folks—I’d say MOST FOLKS are Mis-Lead in thinking that the modifications they’ve made,,,has somehow IMPROVED their "towing performance".

It Does in a way,,,,it Pulls Quicker,,it pulls FASTER.
It pulls HARDER when Forced to step on the Gas to maintain Cruising Speed..

That gives a Very distinct impression of having Improved Towing Ability.
Engine FEELS Stronger and More Responsive.
It IS actually.

Does 0-60 TIMES matter,,,when towing a trailer?
Does 60-100mph TIMES matter?
Does Raising TOP SPEED the trailer can be pulled from 100mph to 115mph,,,REALLY make a Better Tow Vehicle?
ALLL That GAIN is REAL,,,
but is that REALLY an Improvement?

Especially when You’re gonna have to Cruise down the road Pumping the Throttle even MORE than ever to maintain a constant speed?

I don’t argue with anyone who thinks their Hop-Up has
improved their towing performance.
In fact I personally LIKE strong accelleration,,and a crispy responsive throttle with strong pulling at high speeds.

Even have pulled a few trailers over 80~90~100mph.
Not as fun as it sounds.
…………………………………..
There’s 2 ways to Improve Part-Throttle Cruise Towing capability.

1) Lower Gearing in order to RAISE RPM to beyond the TORQUE PEAK at whatever Road Speed is desired.

Such as Driving down the Highway at 60~70Mph in 2nd Gear.

Pro’s:
You stay in the Right area of the Torque curve,,,
An RPM which is BEYOND the Torque Peak

Con’s:
You’re spinning the motor like a chainsaw.
BAD for wear & tear
And burning a buncha gas at the elevated rpms.

2)LOWER the TORQUE PEAK RPM

Pro’s:
*You can drive Sane Speeds/RPM on Hiway and still be "OVER-revved" to Beyond Torque Peak.
Which is what you NEED for towing.

*Much better pulling power from 0-to-60

*Much better fuel mileage at CRUISE conditions

CONS:
*Power falls off FAST at HI-SPEEDS.

What you GAIN in 0-to-60 times,,,
you LOSE in 60-to-100 time

Engine begins to increasingly run out of breath as road speed/RPM increases.

So as RPM rises,,,throttle gets mushier,,acceleration gets Slower.

But by virtue of the characteristics of a Torque Peak being Moved DOWN the RPM Scale,,
Your Towing ability Remains STRONGER over a wider range of Road Speed.

Because it has Farther to fall RPM-wise as it climbs back UP the Torque Curve.

It’s BASS-Akwards Thinking,,almost Abstract,,,to imagine going up a Long hill or mountain,,,and Steeper it Gets,,,the Stronger the engine pulls.

It wont make you Jump over Mountain Tops ,,SuperCross Style.
But it absolutely WILL "flatten out the road" of all the usual ups & downs that play hell with Cruising Speed being solid & steady.
NOT perfectly,,,but to an Amazing Degree.

…………………………………………
TO SHIFT TORQUE PEAK DOWN the RPM SCALE

Very Simple Principle.
"Close the INTAKE VALVE SOONER"

Run out to the Jeep,DO That,,and your probs are Solved!

LOL,,,,EASY,,but not quite THAT easy.

PoorBoy Method>>>
Change the Position of the Engine’s TIMING CHAIN.
You must ADVANCE the Camshaft,,,so that the Intake Valve Closes SOONER.

At 50K Miles,,,not a Bad Idea to install a NEW CHAIN/GEAR set.
Just removing the slack from normal wear ALONE would make a feelable improvement.

But you NEED a BUNCH,,,about 10* Degrees is all you can change a stock camshaft.

Stock Gear has 48Teeth.
That’s 7.5* CAM degrees,,,and 15* Crankshaft Degrees Per Tooth.

TOO MUCH for a Whole Tooth .
You need it about 1/2~3/4 Tooth OFFSET on Cam Gear.
That’s 8*~12*(Yeah,Sloppy,,I said POORBOY:)
5/8 Tooth would be Ideal >10*.

VERY easy and simple on a Drill Press.
I’ve done 100’s "by hand" with a hand drill and always gotten surprisingly close.

Simply Re-Drill the Hole for the cam drive pin.

Understand what I just said?
It’s one of those things which just flys right by us.
Sounds Too Simple to be So Profound & "The ANSWER"

***Take a Common Hand Drill and probly a 3/8" Drill Bit—everyday stuff,,,Nothing Fancy.
** Drill a new Hole in the Camshaft Gear to reposition the cam a little.
*Button ‘er up,,all done.

In terms of TOWING,,,under Steady Cruise conditions….
Engine WILL be STRONGER and STEADIER than the Biggest Stroker you can fit in your engine..

Because the CAMSHAFT Re-Positioning ,,
RE-POSITIONS the Torque Peak down to a LOWER RPM.
An RPM range where any RPM Drop from Cruise is met with RISING TORQUE.

A Stroker,,,only Vertically RAISES the TOTAL POWER on the Chart.
It has Very Little Influence of Shifting the PEAK.
You’ll get LOTS more TOTAL POWER available.

But put that Stroker on a Flat Level Road CRUISING,,,and start it up a Hill,,,
It’s gonna cower like a Yella Dog.

No Matter How Much TOTAL any engine has—
A Given Load under Given Conditions at a SET THROTTLE POSITION …..WILL be sensitive to any Increase in LOAD.
The RESPONSE to the Load is simply to "slow down"

If it’s PRE-PEAK,,,Any RPM DROP results in FALLING POWER.
Whether it falls from 100 to 90,,
Or from a 1000 to 900.
Engine will DROP in Power from whatever Level it WAS producing to Maintain Cruise,,,anytime Load is increased.

If it’s POST-Peak,,,any RPM Drop results in RISING POWER.

#1)ACCELERATION—Stroker Wins hands down with More Total Torque under wide open throttle
#2)PART THROTTLE CRUISE—One Little Hole in Cam Gear makes biggest,baddest Stroker seem like a kid’s toy
#3)Wide Open Throttle/Top Speed—AGAIN,,Stroker Wins hands down with More Total Torque under wide open throttle.

It’s NOT so much about MORE POWER.
More Power TOTAL is always Better in SOME aspects of Overall Performance.

But it’s also a LOT more than many folks realize about TUNING and Tailoring Power Characteristics to the Application at hand.

………….
OR,,,if you GOTTA SPEND MONEY,,,,
Replace the Camshaft with a Different Profile.
NOT always,,,but Most of the time you will get Better Results.

I have experienced SEVERAL instances where "Mileage/RV/TORQUE" Type Camshafts have yielded No Real,Useful Improvement over a simple Re-Indexing of a Stock,Factory cam.
Certainly NOT cost-effective in those instances to pay the $$ and Work to swap a Camshaft vs simply a Timing Chain/Cam Gear "swap"

But,,, a "Real Cam" modifies ALL the parameters and geometry to enhance performance at the Lowered Torque Peak.

Simply RE-Indexing a Stock Cam moves the ENTIRE cam,,,ignores Exhaust Timing requirements,,etc
It only Gains by simply Advancing Intake Closing Point.
While there’s an Overall Gain in TOWING performance,,,there’s a sacrifice in INEFFICIENCY caused by disturbing Exhaust Timing.

A "Real Cam" captures the Lost Potentials of a simple Re-Indexing.

It’s a matter of how much you wanna spend.

Either way WILL make a BIG improvement in CRUISING power,,,TOWING.

Better just Costs More,,as always.
………………………
Just for example,,,,
The 2 flattest,,Lowest RPM Torque Peak cams i can find are
Crane #70501 Int Valve Closes at 49* After Bottom
Crower #44242 Closes at 47* After Bottom
STOCK ‘00 4.0 Closes at 62* After Bottom

That’s a 13* and 15* ADVANCE of the Intake Closing point,,,Earlier Closing.
Which is a BUNCH.
But even more important than the Gross Figure,,,
is that it’s an IMPORTANT 13~15* because of it’s Location relative to Crank/Piston position.

At TOP and BOTTOM of the Piston’s Stroke,,
There are Several Degrees of CRANK Rotation where Piston actually Does NOT MOVE.
Crank just Rolls over the last few Degrees on Upstrock as piston comes to a STOP,,before reversing Downward again.
And after Exact TOP,,crank rolls a few More degrees befor it starts pulling Piston DOWN.

How SLOW is STOPPED?
Piston Speed is actually ZERO.
It begins to Accelerate and reaches HIGHEST velocity at 90*,
3:00 and 9:00 on a Clockface

At Noon and 6:00,,Piston is STOPPED.

Consider the RATIO of Crank Rotation in Degrees to Actual Piston Travel.

At Top/Bottom—1* of Crank Travel = O " of Piston Movement
At 45* Past Top/Bottom,,1* Crank Travel = LOTS of Piston Movement
As it goes From Top/Bottom thru the Next 90*//HALF-STROKE……
The Ratio Continually RISES>>. Each Degree of Crank motion yields a Larger amout of Piston Travel per-degree of Crank Rotation.

Point Is,,,,+/- 15* at Top or Bottom have Little Effect on Piston Motion.

Whereas 15* in the 45* to 90* Arc,,,the "7:30 to 9:00 O’Clock Range",,,,produce a HUGE and RISING amount of Piston Motion.

What’s the PISTON DO?
Pumps AIR.

Meaning,,,that Range of Crank Angle is producing DRAMATIC Changes in Pumping Volume Per Degree of Crank Motion.

When you CLOSE the Intake Sooner,,You TRAP more Air to Compress.
Earlier you Close it,,,the More Powerful the Power Impulse when it Fires.
Cuz,,,it has compressed a larger Volume of air and is at a Higher Static Pressure before Ignition,,,
AND has more Air Volume to support Combustion.

But closing it TOO SOON stifles the Intake Systems INERTIAL AIRFLOW which occurs AFTER Bottom.
AKA,,"Ram Effect"

At Higher Speeds,,the Air Volume and Velocity are High Enough to continue Filling the Cylinder even As the Piston begins it’s Upstroke.
Recall how SLOW Piston is moving as it comes up from Dead Bottom.
That’s TIME for the Moving Air Column to Continue Filling
even against the Rising Piston.

The HIGHER the RPM,,the LATER you can Close the Intake.

That HIGH RPM Filling Effect is what establishes HI RPM Torque Peaks and Hi RPM RANGE.
The engine can simply Breathe at the elevated speeds.

To DROP the Torque Peak AND maintain the Gross Power Numbers,,,,
Ya gotta FILL Cyl effectively at LOWER RPM.
Closing the Valve EARLIER ,,,TRAPS more air.
That Satisfies the Filling requirements to yield High power at Low RPMs.

But the early closing Snubs the RAM EFFECT at Hi Speeds.

…………………………
I dunno how "mechanical" or Industrious You are.

But for the price of Cam Cover Gaskets and a days Work,,
You can EXPERIMENT with Re-Indexing your Cam.
Just Re-Drill the Hole for the Alignment Pin,,,about a 1/2 tooth Offset IN THE DIRECTION of ROTATION.

If You LIKE it,,,You can decide if You wanna spend the $$ for a Cam Swap..
You’ll maintain the Lower RPM Peak with an actual Cam Swap,,,
but also gain some extra efficiency thus a Higher Total Output both AT & on both sides of that peak,,,,,versus simply re-indexing your stock cam.

I can’t gaurantee you HOW MUCH,,
But I Will gaurantee you cannot match "Bang for Buck" of simply re-indexing.

This is IMPORTANT to YOU—
NONE of that is Crazy Mod>Stressful>Hair-Brained>
Engine Blowing stuff.
Reliability and "Trouble Free/Maintenance Free operation" will at MINIMUM equal your stock,original engine.

Custom Cam Kits,,,,will IMPROVE reliability to an extent.
More Power at Lower RPM’s will Also.

Engine WILL start easier,,Idle smoother,,and Pull with LESS throttle opening.

In terms of wear & tear,,,unlike allmost any other Mod,,,,,
This is all an IMPROVEMENTin "reliability",,,,,
or at least a ‘wash"versus a stock engine.

Not to mention almost Certain an increase in Fuel Mileage.

You find the Chuck Key for your Drill yet,,,to drill that Cam Gear??
LOL

…………………………..
I looked around at 4.0 Specs,,,and best as I can tell your engine seems to have a Torque Peak at 4000 RPM.
Which is just a coincidence cuz it’s same as the Peak on our random example Chart.

Whatever it is,,,,,
You know what Road Speed you TOW your trailer at.

Assuming 4.88 Gears in the Jeep,,and 32" Tires,,,
and Direct Drive 1:1,,,,no Overdrive……
Lets look at some RPM/MPH Figures.

Overdrive would LOWER RPM ,,,as would Taller Tires.
Or Conversely,,at SAME RPM it would RAISE Road Speed.

So,,,it would get "worse" in terms of trying to Run BEYOND Torque Peak at sane Towing Speeds.

Also,,so would any Mods which have RAISED your engine’s Torque Peak’s RPM point.
That’s "worse" in that it requires Higher Road Speed to surpass the Torque Peak.

—-4.88’s w/ 32" Tires—– 1:1 Hi Gear & w/ 20% od~.8:1
(average overdrive ratio on most stuff)
4000 RPM= 78 MPH—97.5mph
3500 RPM= 68 MPH—-85+mph
3000 RPM= 58.5 MPH—73+mph
2500 RPM=61mph in OD

—4.88’s w/ 30" Tires
4000 RPM=73mph— 91,5mph in .8 OD
3500 RPM=64mph—-80+mph OD
3000 RPM=55mph—-69mph OD
2650 RPM =60mph in OD

Look at those Road Speeds in OD,,,
at your "Factory Original" 4000 RPM Torque Peak!!!

Even Locked-Out of OD,,and running 3rd which is usually 1:1 Direct Drive on Auto OD’s

You’d have to Drive OVER 75MPH towing your Trailer,,,,
To be able to have any RPM DROP be met with RISING TORQUE

Trying to cruise in OD,,,assuming you have 32" tall Tires….
You’d have to Tow that Trailer Literally 100 MPH in order to have an RPM drop ,,,fall upon RISING TORQUE.

And that’s only IF any of your Current Mods have NOT raised Torque Peak beyond 4000 RPM published figure.

IF you wanted to Tow at 60MPH and be right ON the peak at 4000rpm,,,,
and assuming .8:1 OD w/ 32" Tires…..

You’d Need 8.0 :1 Axle Gearing!!!

Or without OD,,,just 1:1 direct to run 4000@60mph,,You’d need 6.30 Axle.

Those numbers are all ABSURD,,,,anyone is welcome to check my Math.
And I hope I made it clear,,I’m assuming Tire Height and OD Ratio.

Even If I’m 20% OFF,,,,the numbers are JUST as Absurd.
Unless Towing a Trailer at 80MPH is that much Less absurd than at 100mph.

And those MPH figures at 4000 only let engine run AT PEAK.
Where a Drop in RPM is "Neutral" as it falls back into FLAT part of Torque Curve.

NOT FAST ENOUGH,,Not Hi-enough RPM to EXCEED Torque Peak where any RPM Drop is supported by RISING Torque.

……………………
Ya GOT to OverRev beyond the Torque Peak to have GOOD,Strong Towing at STEADY CRUISE CONDITIONS.

Whatever MPH a driver wants to achieve that depends upon
TORQUE PEAK RPM X Overall Gearing.

To get good CRUISE-TOWING performance down at Sane & Legal Road Speeds,,,
Ya got 3 basic Options>>>
A)Downshift
B)Lower Overall Gearing(an 8.0 Axle??? YIKES!)
C)Lower Torque Peak

"NORMAL" Hop-Up stuff,,,Power Enhancements DONT do that.
They actually Deliberately do the OPPOSITE.

RPM is "The WhoreHouse of Engine Performance"
Quickest,Easiest place to go Get Some.

Dont Have to even actually RAISE Power or Torque TOTAL.
Just raise the RPM at which the Peak Occurs,,,and it’s cheap easy Thrill.
It FEELS Faster,,,60-to-100 IS Quicker.

But that’s not the task at hand.
Towing & Cruising aint Drag Racing or NASCAR.

………………………..
Crower Cams sez:
re Cam #44242
"MILEAGE COMPU-PRO / PERFORMANCE LEVEL 1 - Enhances mileage
and torque in stock engines.
RPM Power Range: Idle to 3500 / Redline: 4000 plus."

I’m 90% confident that is HORSEPOWER PEAK,,,which is Higher than Torque Peak.
I’d assume Torque Peak is between 3000&3500rpm.
Or Lower.

http://www.crower.com/misc/m_cat.shtml
Under "AMC" on page 10

…………………………..
CRANE sez:
re Cam # 750501
"SMOOTH IDLE, DAILY USAGE, FUEL ECONOMY, 1600-2200 CRUISE RPM, 7.75 TO 8.75 COMPRESSION RATIO ADVISED. BASIC RPM 1000-4000"

Realize their "Cruise RPM" is from PERFORMANCE perspective.
They consider Punchy Accel Range as important.
Thus,,,they are Implying that The cam is "OUT of BREATH" above that Range.
Or Conversely,,,,BEYOND it’s PEAK ,,,
where further RPM Rise yields Falling Power.
It’d be OVER-REVVED.

So from ABOVE their "Cruising Range" RPM,,,,
Falling RPM yields RISING POWER.

RISING RPM= Falling Power
FALLING RPM = RISING Power

Approach a Hill and the load works Against your Steady Throttle,,,
but Engine Responds by Rising in Power from climbing "backwards" UP towards it Power Peak
any time RPM’s decline.

……………………………..
If any of the above principles Sound ODD(and i KNOW it does to all the HotRod Experts)……

You can go TEST it for yourself very Easy and simple.
And EXPERIENCE for Yourself the effect of exactly what I’ve tried to explain.

*Find you a "Safe Road" to fool around on.
*You need any short length of Flat,Level Straightaway coming into a HILL >__________/
*You NEED a Tachometer,ya really do—they can be had Cheap and are easy to hook up—heck,,just loop the wire thru the side window and hood-gap for temporary service & toss the Tach up on the dash:)

*Cruise along in 2nd gear at 4500 RPM ,,,hold throttle steady.
*Approach that hill and begin up the hill while watching the RPM change,,,and SENSING the Change in Throttle you need to apply to maintain your SPEED.

*Yeah,,engine’s Screamin’ and You’re going relative SLOW in 2nd Gear—but ya NEED to Experience the Effects of that 4500 RPM.
You wanna Approach and Climb that hill while Cruising,,OVERREVVED past Torque Peak.

Do it a couple times to get a good feel for how it acts.

I’m NOT saying " Go Dog Your Truck,",,or run it 20 Miles doing that.
Just a Steady,,LIGHT FOOTED but HI RPM approach and Climb up an incline.

*Note the Road Speed at whatever 4500 RPM happens to be in 2nd Gear

*THEN,,,,
Plug it into TOP GEAR,,,or OD

*Drive the same ROAD SPEED as before.. across the flat/level and Up the Incline.
Just a light Throttle,,steady cruise.

*Note the Tach ,,,and the effect of the Hill on your RPM compared to doing it at 4500 in 2nd.
And,,the feel of the gas pedal and Your actions on the gas.

*The POINT in the Comparison is to compare
Cruising on a level road,,then meeting Increased Resistance/Load of the Hill.
a)at 4500 rpm,,OVER the Torque Peak
b)at same ROAD SPEED as "A",,,but at Much LOWER RPM in a HIGHER GEAR,,,,Thus BENEATH the Torque Peak.

If it’s Much of a Hill,,
You’ll Surely be Peddling the Gas Much More
in Hi Gear/Low RPM…
than You will be at SAME SPEED>but HI RPM.

At 4500,,,Your engine will hardly notice the hill.

You can build-up as much HP/Torque as ya want.
You’ll go Quicker,and Faster.
And there’s nothing Wrong with that.

But far as Towing,,,and Part-Throttle Cruise no amount will help much.

Everybody knows what Lugging an engine is,,,,sorta.

In Your particular driving conditions,,,towing down the highway,,,,
That may not fit the "Hot Rod /4 -Wheelin’ magazine" Definition of Lugging the motor.

But TECHNICALLY,,according to engine operation physics,,
that’s exactly what’s happening.

Anytime an engine reacts to increased load by Losing power,,,,that’s Lugging it.

Hiway Cruising may not SEEM the same as Idling along in Hi Gear.
But it IS the same.

Go Idle along in Hi gear,,,,and start up a ramp and it’ll STALL the Engine.

Gassin’ it to keep it running is only INCREASING POWER via feeding it more air in order to make More Pressure which is realized as MORE TORQUE.

If an Engine is Tuned to use it’s natural airflow resonances and volumetric efficiency to "automatically" Rise in power as RPMs DROP back toward a More Cylinder-Filling Efficient speed…..
You’re getting a Different Method of achieving SAME effect as stepping on the gas.

More Air is More Air.
Whether from Increased Throttle opening,,
or Increased Volumetric Efficiency at a steady throttle opening.

Throwin’ another Log on the fire is always More Comfy.
Warmer is Warmer,,,no matter who hauls the firewood.

"BETTER" is when WE can stay put,,,,and somebody Else goes out in the cold for wood.
Either way,,we dont get any warmer from the fire.
But we Stay warmer as an average by using an alternative approach to getting that extra log.

WE can do the work of Pumping on the Gas Pedal to stay up to speed by feeding the engine More Air.

OR,,we can Tune the Engine to a state where the inevitable RPM Drop of any increased load under Part Throttle Cruise causes a RISE in Volumetric Efficiency,,,
and the Volume of Air being inhaled Naturally Rises without us having to open the throttle so much/often.

……………………

One other very cost effective Mod is raising Compression.
Especially if you decide to do a Cam Swap,,,
cuz some of the labor of the 2 different operations overlap.

Engine’s mid-range and low speed efficiency is Really hobbled by low compression ratios.

Increasing it raises power Output BENEATH the Torque Peak.
And it increases Torque On BOTH sides of the CamelHump.
On each Side of the Peak.

And it’s one of the few Mods which doesnt try to predominantly RAISE the power peak in terms of RPM

So in any quest for Cruising/Towing power,,,higher compression imposes some of the LEAST Penalty of raising torque peak’s RPM

Jeeps are 8.8:1 compression ,,I read.
Fuel is always a consideration in matters of compression.
the I-6 Heads can get near 10:1 on "Best Available" Gas.
Especially in Cooler climates.

They can comfortably run 9.25 to 9.5 Compression on any good gas,,anywhere.
It’s a "Livable" ratio.
Removing the head and getting an inexpensive Head-Shave of a Moderate amount,,,,and perhaps using Chrysler’s "THIN" head gasket will get near that range.

1/2 ~3/4 point increase in Compression AINT "Race Car" Realm.

But it Does produce a cost-effective,,worthwhile boost to Both Total Power and Driveability Characteristics at Low/Mid RPM range

And if there’s NOT an actual Improvement in Fuel Mileage,,
at least there’s No Penalty from higher compression.
VAST majority of instances will indeed show an improvement in Fuel Economy,,,even if it’s only an insignificant amount.

Lowering the head by virtue of Machinig/Milling and using a thinner gasket not only raises Compression,,,,
It enhances Combustion Efficiency.
It reduces the Chamber Volume in the ‘Quench Area",,,a narrow band of Close proximity between Head & piston,,,where the Fuel Mixture Does NOT burn .

"Lowering the Head" Reduces the volume of Intake Charge which does Not contribute to combustion or Power.

And that Increase in efficiency is in addition to the mere Higher Pressure from a smaller total chamber volume.

————
Sorry this is so long,,,I typed off/on all day long a line or 2 between chores,,lol
Didnt realize how protracted it’s gotten.

All this is Cheap,Easy,,NON-Exotic,,Reliable and Trouble Free.

Deceptively SIMPLE,,,but it strikes at the heart of the prob and directly addresses the deficiencies in TOWING/Cruise applications.

Nothing else Really,actually Does.

You NEED to get ACROSS the HUMP,,,

Not Chase it Faster and Faster and Higher and Higher

All just Info,,for what it’s worth.
Hope any of it is of use to you.

…………
Yikes,,i just realized you said you have 35" Tires???!!!

That 4000 RPM Torque Peak Hump you gotta get across,,
is 87 MPH High in Direct Drive,,,
and 107 MPH in Overdrive????

And you say You gotta Downshift sometimes??
That’s really all you can do AS-IS to Beat the Hump,,,
Besides Driving waaay over 100 MPH.

And Please don’t misunderstand ANY of this.
NO WAY am I criticizing ANY sorta Mod,,,or saying anything Negative about a Stroker or whatever.

In fact,,a Stroker is probably Wisest Mod for more useful TOTAL power.
I’m certain You’d Love it.

My entire point is about that Torque Peak/RPM thing as it Relates to Part Throttle Cruise behaviour.

No matter HOW MUCH Total power you ever have available,,
Under Cruise/Part Throttle you’re ONLY producing a FRACTION of the Total Available.

Add any extra resistance to that steady-state driving condition,,
That’s a DEMAND for More Power which the existing Throttle Position CANNOT accomodate.

So Ya GOTTA Pedal the Gas to feed it More Air,,to produce that extra power needed.

If You’re UNDER Power Peak,,,,
Power FALLS upon the appearance of extra Demand and the resultant RPM dip.

If you’re OVER the peak,,Opposite Happens.
The RISE in Volumetric Efficiency as the RPM dip "automatically" feeds engine More Air instead of needing the Throttle.
Power RISES when the RPMs dip.

And in terms of just Cruising down the road,,,Trailer or Not,,,
Result is a steadier,smoother RPM range and Lots less downshifting and throttling to Maintain a steady speed.

Reason a Trailer or Heavy Load "makes things worse",,,is simply cuz it imposes a greater Demand.

Changes in RPM and Power are thus "sensitized" by the Load.

UNLOADED requires only "X" amount of Power to
RE-cellerate back to speed after any dip in RPM.

Heavy Load requires Much MORE Power to resume Speed.

All while CRUISE POWER requirement to just move down the road at steady speed is very Little Difference whether Loaded or Not.

So Under Load,,when RPM Dips,,it Dips a Lot.
And to Resume Speed,,,You gotta Really Gas it HARDER in order to Promptly get back up to speed.

Heavy Load creates Driving Mannerism of Over-Compensation on the gas pedal.

Cuz it’s NOT simply the mere SPEED,,,,
it’s the TIME it takes From any Dip,,to get Back UP to speed.

UNLOADED,,,You can "fix a speed dip" of 2~3MPH in a few Yards with More Throttle.

LOADED,,,,the acceleration demands MORE POWER.
Or,,,more TIME.
You could,,,
a) Use TINY extra Throttle and WAIT a Half-Mile to regain that 2-3 MPH Dip
or
b)Use OVER-THROTTLE to resume speed in the same Few Yards as when Unloaded..

TOUGH to Feather-Foot a Gas Pedal pulling a Heavy Load.
So we end up really pedalling the gas a Lot to try to maintain a steady speed.

No amount of "MORE POWER" can address that.

But we CAN tune the engine to ASSIST in that Compensation,,,instead of work Against Us & make things worse.

That reduces a BUNCH of the Overcompensation we do as Drivers.
And we get a steadier ride,,,with an engine that Really Does pull harder and steadier as we CRUISE along

If You understand what I’ve said about Characteristics on each side of the Torque Peak…..
But are Skeptical of what I said about MORE POWER being of little use for CRUISING and NOT solving the prob of RPM dip=Torque Drop……

Here’s a variety of Charts.
You can see an Extreme range of TOTALS represented.
And also see "The Hump"

Below the TORQUE PEAK,,,,even the HIGHEST POWER engines still display same phenomenon of Falling Power as RPM Dips.

And BEYOND the Torque Peak,,,
RISING power as RPM Dips "backwards" down the scale.

Big Numbers really dont help that particular Driving Niche.
All about which area of the Torque Curve you’re driving in.

Charts also show a RISING Torque Peak as Total Power is Increased.
That’s just part of the Power Game.

But,,,it demands Increasing Road Speed,,or Lowering Gears to stay in Torque Curve’s sweet spot

http://www.compcams.com/Technical/DynoSheets/
( Those are all 350 Chevy V8’s I ‘bleive,,,,but in the sense we are considering,,,"all engines are the same".
The Numbers change,,the PRINCIPLES don’t)

C250C Hond twin starts & dies?

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