Engines

In article >,
David Skelton > wrote:
> Engines that have balancer shafts are less efficient due to the
> increased inertia and weight

Less efficient than adding a couple of cylinders to do the same? I think
not...

--
*Do infants enjoy infancy as much as adults enjoy adultery?

Dave Plowman London SW
To e-mail, change noise into sound.

In article >,
Dean Dark > wrote:
>On 5 Feb 2010 09:49:28 -0500, (Scott Dorsey) wrote:
>
>>dizzy > wrote:
>>>I have no problem with hatchbacks, per se. However, I do have a
>>>problem with 4-bangers. The unrefined vibrations. The flatulent
>>>exhaust note. So econo-car. Many years ago I declared myself "to
>>>old" for 4-bangers.
>>
>>Hey man, don't be putting down my 2002. It's zippy.
>
>Take a look at the "flatulent 4-banger" in the Honda S2000. I gotta
>get myself one of those some day...

Now, those things DO sound like a sewing machine. A very zippy sewing
machine, mind you....
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

"Dave Plowman (News)" > wrote in message
...
> In article >,
> David Skelton > wrote:
>> Engines that have balancer shafts are less efficient due to the
>> increased inertia and weight
>
> Less efficient than adding a couple of cylinders to do the same? I think
> not...
>
> --
> *Do infants enjoy infancy as much as adults enjoy adultery?
>
> Dave Plowman London SW
> To e-mail, change noise into sound.

Less efficient than those 4 cylinder engines without balancer shafts.
I think yes, I know yes, too.

Regards

David



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On Fri, 5 Feb 2010 10:42:39 -0000, "David Skelton"
> wrote:

>Normally aspirated multivalve six cylinder engines tend to produce less
>torque per cc than do other designs of engines, I forget why now,

IIRC, the same air mass through a larger orifice will travel more
slowly. This reduces/complicates the air-fuel mixing ability and
affects engines regardless of number of cylinders. It's most
noticeable as low(er) torque at low revs. Forced air induction fixes
this.

--
Z

"Zathras" > wrote in message
...
> On Fri, 5 Feb 2010 10:42:39 -0000, "David Skelton"
> > wrote:
>
>>Normally aspirated multivalve six cylinder engines tend to produce less
>>torque per cc than do other designs of engines, I forget why now,
>
> IIRC, the same air mass through a larger orifice will travel more
> slowly. This reduces/complicates the air-fuel mixing ability and
> affects engines regardless of number of cylinders. It's most
> noticeable as low(er) torque at low revs. Forced air induction fixes
> this.
>
> --
> Z

You are quite correct, but my point is that straight sixes produce less
torque at low revs than do other designs of the same capacity, which may
influence engine designers. If an engine produces greater torque at lower
revs, then in practice, the vehicle will return better mpg figures and lower
emissions.

Most BMWs in Europe are bought new by businesses, whom will pay less tax on
the vehicle if the emissions are low. The lower the emissions, the lower the
tax. Therefore, it is in BMWs interest to find ways of reducing the
emissions of their range to keep, or increase, their market share. This
could be a reason for the possibility for the replacement of sixes for blown
fours as the OP ponders.

I personally do not believe the official figures for vehicle emissions as
the test is in a controlled environment to standardise results, rather than
on actual test on the roads. Even a test track with controlled variables
would show how optimistic the official figurs are. I believe some car
magazines have attempted to achieve the official results and failing by
quite a distance.

In my opinion, sorry folks, building new cars is more resource hungry than
maintaing those already OK. It takes more energy, resources and more
environmental impact (currently) to make an 'average' car, than it will
consume in many years of 'average' use.

Best regards

David



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"David Skelton" > wrote in
:

> "Zathras" > wrote in message
> ...
>> On Fri, 5 Feb 2010 10:42:39 -0000, "David Skelton"
>> > wrote:
>>
>>>Normally aspirated multivalve six cylinder engines tend to produce
>>>less torque per cc than do other designs of engines, I forget why
>>>now,
>>
>> IIRC, the same air mass through a larger orifice will travel more
>> slowly. This reduces/complicates the air-fuel mixing ability and
>> affects engines regardless of number of cylinders. It's most
>> noticeable as low(er) torque at low revs. Forced air induction fixes
>> this.
>>
>> --
>> Z
>
> You are quite correct, but my point is that straight sixes produce
> less torque at low revs than do other designs of the same capacity,
> which may influence engine designers.


this is not correct. as a general rule the fewer the cyl, (every thing
else being the same) the fewer number of cyl, the more torque the eng
will make at low rpms. as torque is greater with a larger cyl bore. also
there is less parasitic loss from less moving parts. KB


If an engine produces greater
> torque at lower revs, then in practice, the vehicle will return better
> mpg figures and lower emissions.
>
> Most BMWs in Europe are bought new by businesses, whom will pay less
> tax on the vehicle if the emissions are low. The lower the emissions,
> the lower the tax. Therefore, it is in BMWs interest to find ways of
> reducing the emissions of their range to keep, or increase, their
> market share. This could be a reason for the possibility for the
> replacement of sixes for blown fours as the OP ponders.
>
> I personally do not believe the official figures for vehicle emissions
> as the test is in a controlled environment to standardise results,
> rather than on actual test on the roads. Even a test track with
> controlled variables would show how optimistic the official figurs
> are. I believe some car magazines have attempted to achieve the
> official results and failing by quite a distance.
>
> In my opinion, sorry folks, building new cars is more resource hungry
> than maintaing those already OK. It takes more energy, resources and
> more environmental impact (currently) to make an 'average' car, than
> it will consume in many years of 'average' use.
>
> Best regards
>
> David
>
>
>
> --- news://freenews.netfront.net/ - complaints: ---
>



--
THUNDERSNAKE #9

Protect your rights or "Lose" them
The 2nd Admendment guarantees the others

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"Kevin" > wrote in message
6.121...
> "David Skelton" > wrote in
> :
>
>> "Zathras" > wrote in message
>> ...
>>> On Fri, 5 Feb 2010 10:42:39 -0000, "David Skelton"
>>> > wrote:
>>>
>>>>Normally aspirated multivalve six cylinder engines tend to produce
>>>>less torque per cc than do other designs of engines, I forget why
>>>>now,
>>>
>>> IIRC, the same air mass through a larger orifice will travel more
>>> slowly. This reduces/complicates the air-fuel mixing ability and
>>> affects engines regardless of number of cylinders. It's most
>>> noticeable as low(er) torque at low revs. Forced air induction fixes
>>> this.
>>>
>>> --
>>> Z
>>
>> You are quite correct, but my point is that straight sixes produce
>> less torque at low revs than do other designs of the same capacity,
>> which may influence engine designers.
>
>
> this is not correct. as a general rule the fewer the cyl, (every thing
> else being the same) the fewer number of cyl, the more torque the eng
> will make at low rpms. as torque is greater with a larger cyl bore. also
> there is less parasitic loss from less moving parts. KB
>
>

That is precisely what I meant. The OP was pondering the change of engine
design from 6 pot to 4 pot.
Four cylinder engines produce more torque (everything else being the same)
than do straight sixes.
Except that the length of the stroke determines the torque values more than
the size of the bore does.

Early designs to overcome this were to separate a straight six into two
3-pot engines below certain revs with manifold devices. Others used
different ways to vary the length of the manifold for different rev ranges.
This is still utilised today, for example in Audis they call them 'tumble
flaps' and in BMWs they are 'swirl flaps'. Other methods are used too, such
as variable valve timing and variable valve lift, stratified fuel injection,
direct fuel injection, but everyone knows all this already.

best regards

David



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Dave Plowman (News) wrote:

> dizzy > wrote:
>>
>> I have no problem with hatchbacks, per se. However, I do have a
>> problem with 4-bangers. The unrefined vibrations. The flatulent
>> exhaust note. So econo-car. Many years ago I declared myself "to
>> old" for 4-bangers.
>
>Whilst I agree with you that an in line six is perhaps the ideal engine
>for refinement (a V-8 never gives a perfectly smooth idle), there's no
>reason a four should have unrefined vibrations - balance shafts are used
>these days to overcome this.

Sure there is. Balance shafts help but are not a cure. Yes, I've
experienced them.

David Skelton wrote:

>> as a general rule the fewer the cyl, (every thing
>> else being the same) the fewer number of cyl, the more torque the eng
>> will make at low rpms. as torque is greater with a larger cyl bore. also
>> there is less parasitic loss from less moving parts. KB
>
>That is precisely what I meant. The OP was pondering the change of engine
>design from 6 pot to 4 pot.
>Four cylinder engines produce more torque (everything else being the same)
>than do straight sixes.
>Except that the length of the stroke determines the torque values more than
>the size of the bore does.

That's my understanding of it. But with more cylinders you can rev
higher, making for significantly more horsepower. Plus you get the
smoothness and lose the flatulent, putter-putter, economy-car sound.

I'll take the more cylinders.

The inline-6 is a great engine design. Both my cars (323 and Supra)
have an inline-6. Cool! 8)

Hopefully consumer demand will compel BMW to continue to offer a good
range of 6's in the 3-series.

>>The OP was pondering the change of engine
>>design from 6 pot to 4 pot.
>>Four cylinder engines produce more torque (everything else being the same)
>>than do straight sixes.
>>Except that the length of the stroke determines the torque values more
>>than
>>the size of the bore does.
>
> That's my understanding of it. But with more cylinders you can rev
> higher, making for significantly more horsepower. Plus you get the
> smoothness and lose the flatulent, putter-putter, economy-car sound.
>
> I'll take the more cylinders.
>
> The inline-6 is a great engine design. Both my cars (323 and Supra)
> have an inline-6. Cool! 8)
>
> Hopefully consumer demand will compel BMW to continue to offer a good
> range of 6's in the 3-series.
>

You do not necessarily need more cylinders to rev higher. But as revs rise,
losses rise exponentially, wear rates rise and efficiency drops.
Horsepower is 'work done' and at higher revs more work is done giving more
horse power.
Usually, higher revving engines have a shorter stroke and thus lower torque
values (area under the curve on the graph).

I, too, prefer the smoothness of the straight six. Some 4 cylinder engines
sound OK, but IMO, not the boxer 4 in the Subaru Impreza.
I also like the low rev torque of forced induction diesel (428 ft-lbs at
1750 rpm in our 335d :-))), but the diesel is not as smooth as the straight
6 petrol.

Best wishes

David



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