Rpm!

[JanGeo]

WOW I had no idea that the engines could pull that hard at such a low RPM as that. Yeah watch out for the really low heavy throttle use as I typically see around here in the city the trucks without the filters in the exhaust are pumping out tons of black soot that gets all over my car parked behind my building from the traffic heavy street in front. I would think at lower speeds in lower gears loosing a little fuel but burning clean with slightly higher RPM would be acceptable since you have to consider engine cooling and tranny load losses too. Too bad there isn't a way of monitoring the exhaust emmissions to see what is the best burn rate for highest combustion burn efficiency. I also imagine that keeping the revs low makes it easier to shift between gears too. You might want to check into using Synlube in the motor and gear boxes since it is a BIG Friction reducer and can cost a lot less to use than conventional oil with their much more frequent oil changes.

[dieselmech]

Holycow, yes I was thinking carb. Not that vacuum plays no role in a FI engine, but comparitively speaking, yeah.

As far as making vacuum though, think about it. High vacuum is a product of a tight cyl seal and a restriction to fill that cyl, whether cam timing,valve/port/intake/carb or throttle body. The very thing that "makes" higher vacuum is what makes the engine efficient in the first place. To reduce the vacuum, you would have to have too much port volume or too much overlap etc. This would certainly outweigh any benefits of the less vacuum produced.
If everything was kept equal, the ring seal going away would lower vacuum but that would also equate to less cyl pressure on compression which again would be bad, not good.
Ideal engine has low rotation losses but good seal.

crap...I keep forgetting we're not talking about a drag engine but a big diesel. LOL!

[theholycow]

Well, in a throttled engine, vacuum is made by those things but only exists because the throttle is closed. Keeping a vacuum uses energy that could go to the wheels instead.

In a diesel...uhh, can there even be vacuum? I thought that was one of the reasons diesels are more efficient.

[Jay2TheRescue]

Diesels need a vacuum pump to operate vacuum operated accessories on the engine.

[dieselmech]

Actually you can have vacuum at wide open throttle. Cfm of a 4bbl is rated at...ah crap, I forget..3 inches I think and 2bbl's are rated at 1.5.
If you put too small of a carb on(because of class rules) you can actually have several inches of vacuum at wot.
Example, 396 2bbl stock elim drag engine. Carb flows 320cfm stock but when installed on an engine spinning 7200rpm it shows almost 4 in vacuum on the dyno. At 4 inches on the flow bench, the carb is actually flowing 414cfm! Just by sticking on a 500cfm holley 2bbl hp jumped 23 and torque by 34 or something like that. Vacuum with the 500 went to just under 1".

Buddy of mine Bruce Fulper (rock and roll engineering) wrote an article in car craft about the new(at the time) pontiac pro stock heads. What he was saying is that the difference between a full out stock head and these new heads was worth 100hp. This was on a 500 cube 9500rpm pro stock engine.
The way they wrote the article though said "gain 100hp with these heads".
Bruce was livid! In essence they were letting people believe if you bolted these heads onto a street 455 you would gain 100hp!

What it actually showed, if you look at it from another angle. Take a pro stock engine making 1100hp and bolt on stock restrictive heads and you will lose 100hp. Same as if you pulled the 2 dominators and stuck on a single 600, you'd probably have so much vacuum the powervalve would never open!

Oh, something else, with the bad heads and tight ring seal, the vacuum in the intake is not as high (before the port) as it is in the cyl. When this gets extreme it can cause ring flutter because of the extreme difference on top and below the piston. This is helped with a vacuum pump to scavenge the block but I've seen it destroy rings and walls after only a couple passes.

Oh, and diesels are more efficient because of the higher compression and higher cyl pressure. Gas has higher btu per pound if memory serves me which means if you could run a gasser like a diesel you would have the best of both worlds..oh wait, ford is doing just that with their new ecoboost engines. High compression,turbo's,direct injection....

Even on a gas engine you gain X amount of power/efficiency from Y amount of compression increase all other things being equal.
(man my memory is getting worse..I used to be able to know that stuff off the top of my head) LOL!

[Robert]

Thellra...what you are experiencing ...noticing...
is the thermo-dynamics of the
sweetspot...
of the water pump and oil/flow pressure at the optimal heat exchanges.
This keeps the head temperatures at a more constant value...
compression ignition...

which has the MOST to do with diesel efficiencies...
gasoline efficiencies...
This is the rpm range that allows maximim torque...with minimal fuel
Back in the late 1960's early 1970's...
an individual using the cummings motor...
total load maxed for the time...65,000 pounds GVW
using mechanical injection...
modified the water pump... entire cooling system...
to be able to
use a special military grade oil...still secret today.
And driving in the east coast areas....
averaged 20 mpg...for over 10 years...daily driving...loaded.
with a smaller engine...than you have...
This is the real reasons the higher rpm's...
create the imbalance...
the reasons when low rpm "lugging will break the heads"...
It is also why a diesel engine is so noiesy/loud when idling...
another example...
An engineer designed the water pump...
using conventional coolant system...
not to have a thermostat based design...
to be driven off the power steering unit...
to control/manage the head temps more accurately..
and got average of 20% improved mpg...
at lower rpm's and higher rpm's.
That concept has been shelved...by the major company he works for.
Since they own the intellectual property rights...
we probably will never see that in mainstream manufacturing.

the famous Tucker engine...
had many of the same features of the coolant system...designed into it...
that got better torque and mpg than diesel engines in the 1950's...
The engines lasted over 100,000 miles...no major re-builds...

As much as aero-dynamics are a factor...
That man in the 1970's proved...
they are not the most important issues to address.

I am from a long line of long haul truck drivers...3 generations...
My Father was...and always will be the "Master of the OLD GRAPEVINE"...
in California...
I am also the true historical inventor of a new technology...
new field of study... declared by US Patent Office...
of improving the thermo-dynamics of the internal combustion engine...
so radically...
it is somewhere in the range of 400 to 500 % improved...
my test engines...gasoline...carbed..
will out perform current diesel engines...2004 duramax...
in identical 1000 mile test runs...on open roads...no test track.
pound for pound...mile for mile...
It is based on keeping the head temps constant....
I achive maximum torque...at 600-900 rpm's...
low compression engines...
Robert W Hull

[dieselmech]

Robert, take the tinfoil hat off. "special military oil? I am in the military as a diesel mechanic for over 27 years....we buy the cheapest that fits the spec. mostly esso 15/40.

Cyl head temps are important, it's why iron headed engines make more power than alum all else being equal (ask any race engine builder) but they will certainly NOT effect anything to the extent you are saying. CC ing a head and making all chambers exact (including plugs) will make a minimal difference same as balancing ect. In performance or efficiency you can't add 100hp, but you can add 1hp in a hundred places.

Also, the tucker engine was an air cooled engine if I recall correctly. And of the few that were built, NONE have over 100,000 miles on them!

You want to know the "secret" to power in an engine as far as temps go? Keep the block hot so the oil is thin and the rings seal good without to much drag and keep the heads ice cold so you can pack in as dense a fuel as possible. check out Stock/SuperStock dragracing where guys are using block heaters to heat the block but putting ice on the intake and heads because they have a heads up run coming.

I don't know, maybe you wrote that with your tongue firmly planted in your cheek and I missed it, if so, you got me. If you were serious...well...stop reading so many conspiracy theory books and take the tinfoil hat off.

[DRW]

LOL
I think you nailed it when you said 'take the tinfoil hat off' !
If you have an hour and many excessive brain cells to kill, try reading his first thread 'The Hull Effect', but I warn you, it's equally painful and much longer.

[Robert]

dieselmechanic...DRW...
tin foil hat...how amusing...
guess what...it don't bother me..
Google TASA...Tucker collector car group...
Pics show coolant system...
historically...
first of its kind...
converted air-cooled helicopter engine.
People on my forum brought it to my attentions...
compare me to his efforts that were thwarted...
Live and learn...

The certified John Deere diesel mechanic...15 years standing...stopped laffing
after the dyno testing.
It sure can...that is why they call it a...
historical new field of study...invention...
I dissipate 1000 F of heat...off the exhaust manifolds...
in 1/2 inch...of air space...
hold your hand 1 1/2 inch away from 1400 F exhaust headers...
and not even scald you...

The heads are "cooled off" externally at the same time.

Come April...2011...the International Patents will be in place...
Then it goes to research and developement...

Yupper....have your fun.
Read about me in the future publications...

[Robert]

DRW...you slammed on me in the past...
people are testing this in 16 countries...
privately...out of their own pockets.
The ex-vice president of research and developement of Cummins Diesel engines...the ones on the road today...
just listened to the engine idling...in the street.
and immediately...called the men in charge at Cummins presently...
We impressed him...in 5 minutes.
I am not regretful that you considered it wasting brain cells.