why diesel engines are having hight torque comparing with the same size of Petrol Engines ??

I couldn't disagree more... The engine in my Blazer is cammed so that
it makes peak power (horsepower) at 5100rpm. It's practically useless
in that truck. Sure, it can make power, but only at such a high rpm
that it'd be screaming down the road. Even with 3.73 gears and 31"
tires, I only turn around 2000rpm at 80mph.

The truck would run much better if it made it's peak torque at a much
lower engine speed. I would not have to turn it as fast. As it stands
now, there's no low-end acceleration, it runs incredibly rich at low
speeds, and the gas mileage is horrendous (11mpg on the interstate).

Horsepower is a derived value...it's not measured, it's determined.
It's used to describe how much work is done over a period of time. The
truth is, I have no need for that much "work" to be done in that short
of a time period. I need torque, and lots of it, and will need even
more once the lift kit is installed with the bigger tires.

Horsepower could not be any more irrelevant to me than it is right now.
Buying into the idea of more HP for the money is what got me into this
mess with my truck.

~jp

Doug wrote:
> Everyone is all hot on torque, but what matters is power. You just have
> to shift down to get the power you need. Look at the rock crawlers,
> they have gears so low they can go 1 mph at 5000 rpm! Power is what you
> need. Torquey motors give good power at low rpms, which is a kick I
> guess.
>
> Diesel fuel has more btus (watts) per gallon than gasoline. Diesels
> engines can be run at higher compression ratios because engines wont
> ping with the diesel fuel. I think just about all diesel engines are
> fuel injected (but so are gas now). Anyway, both work. Personally I
> don't like the noisy, dirty, stinky diesel (prefer gasoline), but they
> do work well. Make an engine with really big cylinders and big flywheel
> and you will have a torqy sob no mater what fuel you use.

SnoMan > wrote in news:47rel2lfh1m697m5b1f7vs8db5h4bk6ksj@
4ax.com:

> On Tue, 07 Nov 2006 17:17:23 -0800, Lon >
> wrote:
>
>>High pressure direct cylinder injection appears to be giving a lot of
>>the benefits of diesel in gas engines.
>
>
> It holds a lot of promise because it eliminates fuel being lost during
> scanvanging which improves MPG and also allows for higher CR ratios
> for a given fuel octane because the injection of fuel into cylinder
> just before ignition cools the mixture as fuel vaporizes rahter than
> being lost to intake port walls and such and higher CR ratio ment
> better power and MPG too. In theory you could run about 13 to 1 CR
> with a gas motor with direct injection and 94 octane and get a nice
> power and MPG boost too. I look for DI on gas engines to be main
> stream by 2010and for diesel to start loosing their luster after that
> because the MPG difference will be a lot less and the diesel will
> still cost a lot more to buy and fuel. DI will alos make it easier to
> supercharge gas motors too.
> -----------------
> TheSnoMan.com
>

Do you or anyone else have more data-samples on CR vs octane rating,
divided into the category 'carburator', 'injection' & 'direct-injection'?
(there is no octane-limit difference between carburator & injection I
believe, but I would like to see more samples about DI)
(I bet you could at least theoretically calculate the thermical gain of the
injection/evaporation, but since the octane rating has no real math behind
it (other than laboratory samples giving a certain mixture of the chemicals
octane vs heptane), you can't calculate much without a table with field-
data....
(at least based on carburator-CR vs octane rating)



--
Bye,

Willem-Jan Markerink

The desire to understand
is sometimes far less intelligent than
the inability to understand

>
[note: 'a-one' & 'en-el'!]

On 21 Jan 2007 04:06:11 GMT, "Willem-Jan Markerink"
> wrote:

>SnoMan > wrote in news:47rel2lfh1m697m5b1f7vs8db5h4bk6ksj@
>4ax.com:
>
>> On Tue, 07 Nov 2006 17:17:23 -0800, Lon >
>> wrote:
>>
>>>High pressure direct cylinder injection appears to be giving a lot of
>>>the benefits of diesel in gas engines.
>>
>>
>> It holds a lot of promise because it eliminates fuel being lost during
>> scanvanging which improves MPG and also allows for higher CR ratios
>> for a given fuel octane because the injection of fuel into cylinder
>> just before ignition cools the mixture as fuel vaporizes rahter than
>> being lost to intake port walls and such and higher CR ratio ment
>> better power and MPG too. In theory you could run about 13 to 1 CR
>> with a gas motor with direct injection and 94 octane and get a nice
>> power and MPG boost too. I look for DI on gas engines to be main
>> stream by 2010and for diesel to start loosing their luster after that
>> because the MPG difference will be a lot less and the diesel will
>> still cost a lot more to buy and fuel. DI will alos make it easier to
>> supercharge gas motors too.
>> -----------------
>> TheSnoMan.com
>>
>
>Do you or anyone else have more data-samples on CR vs octane rating,
>divided into the category 'carburator', 'injection' & 'direct-injection'?
>(there is no octane-limit difference between carburator & injection I
>believe, but I would like to see more samples about DI)
>(I bet you could at least theoretically calculate the thermical gain of the
>injection/evaporation, but since the octane rating has no real math behind
>it (other than laboratory samples giving a certain mixture of the chemicals
>octane vs heptane), you can't calculate much without a table with field-
>data....
>(at least based on carburator-CR vs octane rating)


From what I have seen and read DI with a gas engine decreases the
octane requirement on a engine at any given CR. The reason for this is
that DI cools the mixture at the time of injection as the gas
vaporizes before ingition. These cooler temps reduce tendancy of fuel
to preignite and retards knock. With a carb,TBI or mulitpoint the
mixuter is heated by intake or head ports before it is even
compressed. Furthermore the high injection pressures required for DI
better atomizes the fuel and more completely mixes it with air in
chamber and because fuel is injected before ignition but after valves
close there is no loss of mixture to valve overlap so a more
aggressive profile can be used too. Together with higher CR which
boosts voluetric efficency and less fuel loss because of design, you
will see a net gain of about 10% more HP and about 10 to 15% better
enconomy too and lower HC emissions too. DI for a gas engine is long
overdue.
-----------------
TheSnoMan.com

SnoMan > wrote in
:

> On 21 Jan 2007 04:06:11 GMT, "Willem-Jan Markerink"
> > wrote:
>
>>SnoMan > wrote in
>>news:47rel2lfh1m697m5b1f7vs8db5h4bk6ksj@ 4ax.com:
>>
>>> On Tue, 07 Nov 2006 17:17:23 -0800, Lon >
>>> wrote:
>>>
>>>>High pressure direct cylinder injection appears to be giving a lot of
>>>>the benefits of diesel in gas engines.
>>>
>>>
>>> It holds a lot of promise because it eliminates fuel being lost during
>>> scanvanging which improves MPG and also allows for higher CR ratios
>>> for a given fuel octane because the injection of fuel into cylinder
>>> just before ignition cools the mixture as fuel vaporizes rahter than
>>> being lost to intake port walls and such and higher CR ratio ment
>>> better power and MPG too. In theory you could run about 13 to 1 CR
>>> with a gas motor with direct injection and 94 octane and get a nice
>>> power and MPG boost too. I look for DI on gas engines to be main
>>> stream by 2010and for diesel to start loosing their luster after that
>>> because the MPG difference will be a lot less and the diesel will
>>> still cost a lot more to buy and fuel. DI will alos make it easier to
>>> supercharge gas motors too.
>>> -----------------
>>> TheSnoMan.com
>>>
>>
>>Do you or anyone else have more data-samples on CR vs octane rating,
>>divided into the category 'carburator', 'injection' &
>>'direct-injection'? (there is no octane-limit difference between
>>carburator & injection I believe, but I would like to see more samples
>>about DI) (I bet you could at least theoretically calculate the
>>thermical gain of the injection/evaporation, but since the octane rating
>>has no real math behind it (other than laboratory samples giving a
>>certain mixture of the chemicals octane vs heptane), you can't calculate
>>much without a table with field- data....
>>(at least based on carburator-CR vs octane rating)
>
>
> From what I have seen and read DI with a gas engine decreases the
> octane requirement on a engine at any given CR. The reason for this is
> that DI cools the mixture at the time of injection as the gas
> vaporizes before ingition. These cooler temps reduce tendancy of fuel
> to preignite and retards knock. With a carb,TBI or mulitpoint the
> mixuter is heated by intake or head ports before it is even
> compressed. Furthermore the high injection pressures required for DI
> better atomizes the fuel and more completely mixes it with air in
> chamber and because fuel is injected before ignition but after valves
> close there is no loss of mixture to valve overlap so a more
> aggressive profile can be used too. Together with higher CR which
> boosts voluetric efficency and less fuel loss because of design, you
> will see a net gain of about 10% more HP and about 10 to 15% better
> enconomy too and lower HC emissions too. DI for a gas engine is long
> overdue.
> -----------------
> TheSnoMan.com
>

Yesyes, but I would like to see a quantification/math of the gain in *octane*
rate, when changing to DI....)

Casus:

Engine: Volvo C3-series with a Volvo B30A carburated gasoline, and a CR of
9.3:1, requiring 98 octane (a different version, B30F, with CR of 8.7:1,
accepts 91 octane, by having a 3mm thicker head gasket (meant for lousy
(marine-grade) fuel)).

Fuel: in Siberia en Mongolia it goes down to 76 and even 72 octane....)
(and that was the *main* route, from west to east, and north to south....a
red line on the map....but hardly any line in the sand, not even always 2
vehicles wide on asphalt....)

(these C3-series are so low geared (5.9/7.1/7.6:1) that a diesel-conversion
doesn't make much sense, neither (overall) cost-wise nor fuel-wise (since
only modern diesels achieve the necessary rpm, and modern diesels don't like
the lousy quality of diesel in those area's either (there is only one high-
revving diesel on the market that doesn't care much about fuel quality, and
that is the Steyr M1, both 6 and 4 cylinders (both also used/produced under
license in east-block countries, for the same reason)....but alas, it is too
new to be available as cheap surplus/donor component)


Yes, I know DI isn't an easy modification by any stretch of the imagination,
but I would at least *theoretically* like to know what the gain is....)

Even even 72 octane comes into the realm of this engine, then it might be
worth the effort....)

Even just a few data-samples of any comparable engine would be nice to know
(like different generation of the same block/CR for old&new cq TBI/DI).

Or: what would your above 13:1 CR (then 94 octane) have required *without*
DI?

Thanx!....)


--
Bye,

Willem-Jan Markerink

The desire to understand
is sometimes far less intelligent than
the inability to understand

>
[note: 'a-one' & 'en-el'!]

On 22 Jan 2007 01:17:28 GMT, "Willem-Jan Markerink"
> wrote:

>Yesyes, but I would like to see a quantification/math of the gain in *octane*
>rate, when changing to DI....)
That would be kinda hard to do because there are a lot of varibles
involved. for instance, chamber size and shape, piston shape, bore to
stroke ratio and engine displacement. (the smaller the bore relative
to cylinder dispalcement, the more heat loss there is to cylinder
wall, head and piston because the ratio of volume to surface is not
constant and the more surface area there is, the more it will tend to
quench the knock that can develop because it keeps mixture from hot
spoting. I have seen data to suggest that DI will allow you to raise
CR about 1 to 1.5 points with same octane but again there is no hard
fast rule that would apply to all engine configurations. Sorry that I
can not provide a hard fast rule because a "simple equation" does not
exist. Most engine made today are well beyond 87 octane it true
requirement but the knock control systems they use to retard spark to
mask it does a good job and keeps consumers happy while stealing
efficency and power in the process.
-----------------
TheSnoMan.com

SnoMan proclaimed:

> On 22 Jan 2007 01:17:28 GMT, "Willem-Jan Markerink"
> > wrote:
>
>
>>Yesyes, but I would like to see a quantification/math of the gain in *octane*
>>rate, when changing to DI....)
>
> That would be kinda hard to do because there are a lot of varibles
> involved. for instance, chamber size and shape, piston shape, bore to
> stroke ratio and engine displacement. (the smaller the bore relative
> to cylinder dispalcement, the more heat loss there is to cylinder
> wall, head and piston because the ratio of volume to surface is not
> constant and the more surface area there is, the more it will tend to
> quench the knock that can develop because it keeps mixture from hot
> spoting. I have seen data to suggest that DI will allow you to raise
> CR about 1 to 1.5 points with same octane but again there is no hard
> fast rule that would apply to all engine configurations. Sorry that I
> can not provide a hard fast rule because a "simple equation" does not
> exist. Most engine made today are well beyond 87 octane it true
> requirement but the knock control systems they use to retard spark to
> mask it does a good job and keeps consumers happy while stealing
> efficency and power in the process.
> -----------------

Any particular engines claimed to be rated for 87 octane that really
need higher?

On Tue, 23 Jan 2007 19:26:35 -0800, Lon >
wrote:

>Any particular engines claimed to be rated for 87 octane that really
>need higher?

Basically any engine running a CR of 8.5 or hogher needs more than 87
octane and require active knock control in the form of spark
management and EGR (EGR is used to lower peak combustion temps for
reduced NOx emissions and it also dilutes mixuture and retards burning
rate which limits knock) The problem is that when you use these
methods (especailly spark control) you reduce peak pressures and and
change the crank angle at which thiese peaks are reach and therefore
reduce the efficencny of the IC engine. Also to further complicate the
problem, true octane requirement of a engine are not constant so you
need to pick a octane grade that is high enough to cover peak needs.
Also modern engine tend to need less octane at higher RPM's (say above
3500 to 4000 RPM) because the the cylinder volume is expanding so
quickly that it is less prone to detonate that and they use a timing
curve at WOT that is not very aggressive either to better tolerate
lower octane fuel to keep consumers happy. At lower RPM's octane
requirement tend to increase because of slower expansion rates so more
sprak control is needed which effects responce and MPG in town,
especailly on hot days with A/C on. Furthermore engine load,
altitude, tempature and humidity also plays a role too. This is why a
modern engine may run like a bandit on 87 octane when it is cold and
damp because less octane is needed then and suck in hot temps and lack
power towing with 87. Back in the old days, there was no mystery as to
want octane you engine needed because they where tuned for peak power
not to tolerate low octane fuel and if you did not feed it properly,
you heard it and so could everyone else around you in traffic. As I
have said before, active knock control via spark retarding serves no
purpose in emission controls, it is there to limit consumer complaints
while they satisfy their desire to by the cheapest fuel they can. To
be truthfull and even suggest that your car really needs more than 87
octane in the manual is a death sentance for sales unless all car
manufactures did it because the one that did not would play up that
their vehicle do not need higher octane fuel. Consider this too, when
87 octane came out in the early 70's engine designed to run on it had
8 to 8.5 to one CR max and it was only after the introduction of sprak
trickery that they were able to raise it higher in later years. They
also run all EPA MPG test with 93 octane fuel, never with 87 octane.
One reason Dodge had so much trouble with V10 in trucks was poor knock
control and people running 87 octane towing with them which would have
a tendancy to ping (even if below audiable level) and the vibrations
from this pinging causes the valve to vibrate in seats and leak which
leads to erosion and a eventual burned valve. Most do not realize how
detrimental knock can be to valves over a period of time because it
can do more than damage pistons and heads. (it takes a severe knock to
damage pistons and such but a lot less to damage valves over time)
-----------------
TheSnoMan.com