What is the 3.9 v6 the general is using now?

@l53g2000cwa.googlegroups.com:


I don't think it's a bored version of the 3.8 because why would they go to
the trouble of boring it out just for a measly extra 1/10 of a liter?  
Unless their intent is to deceive people into thinking it's a brand new
engine perhaps.  I wonder why GM still stubbornly embraces pushrod engines?  
Get with the program GM.

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engines?

This is a common statement - as if OHC is some sort of sign of the times.
It's almost as old as OHV designs, and it suffers its own set of issues.
What is it that causes you - and others, to equate OHC with high-tech,
advanced designs?  Have you really compared OHC with OHV?  Considered all of
the factors that an engine designer has to consider as he dreams up a power
plant that will eventually go under a hood?

I'm not against OHC designs, nor am I an absolute advocate of OHV.  The two
have their own set of benefits going for them.  I just wonder sometimes,
when I read a comment like yours, just exactly what people are really basing
their comments on.

--

-Mike-
mmarlowREMOVE@alltel.net

|
|
| >
| > I don't think it's a bored version of the 3.8 because why would they
go to
| > the trouble of boring it out just for a measly extra 1/10 of a
liter?
| > Unless their intent is to deceive people into thinking it's a brand
new
| > engine perhaps.  I wonder why GM still stubbornly embraces pushrod
| engines?
| > Get with the program GM.
|
| This is a common statement - as if OHC is some sort of sign of the
times.
| It's almost as old as OHV designs, and it suffers its own set of
issues.
| What is it that causes you - and others, to equate OHC with high-tech,
| advanced designs?  Have you really compared OHC with OHV?  Considered
all of
| the factors that an engine designer has to consider as he dreams up a
power
| plant that will eventually go under a hood?
|
| I'm not against OHC designs, nor am I an absolute advocate of OHV.
The two
| have their own set of benefits going for them.  I just wonder
sometimes,
| when I read a comment like yours, just exactly what people are really
basing
| their comments on.
|
| --
|
| -Mike-
| mmarlowREMOVE@alltel.net
|
I liked the old Ford flatheads for simplicity. One cam, cam followers
and valves. I thought I went to heaven after I installed adjustable
followers in my '37 Coupe. They were contoured to match the cam and were
kept in alignment by a cotter key.

--
Jarhead




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Grappletech wrote:

I don't care for the hp and torque curves on OHC engines.
So far I've avoided owning a OHC engine.

I had a Maxima SE 5 speed with the 3.0 VQ engine (DOHC, 24 valve) and
it had nearly zero torque anywhere near idle.  It would scream if you
drove it over 3000 rpm, but it was so easy to kill the motor just
driving it around.  Sold that and got the '00 intrigue with the 3.5 GM
premium v6, with also OHC and 24 valves.  Totally different motor
dynamics, it has a great torque curve but unlike the OHV cars I've
owned it doesn't go flat as it revs, it pulls (and smoothly) right up
to the redline.  So don't put all the engines in the same bucket.

S

The fact that an engine has overhead cams doesnt determine the torque
curve nor the horsepower development.  It is what you do with the camming
that makes a massive difference.

@newssvr29.news.prodigy.net:


In the early 90's, I owned a 1985 Toyota Corolla GTS (bought for 600 from
a salvage yard; I had to replace a fender/hood on it; 600 ain't bad for a
5 year old car with 60K miles).  That was a real cool car.  Old school
rear wheel drive. It had the 4Ag-E engine -- DOHC, 16 valves, EFI, etc..  
Same engine as the MR-2 had.  It redlined at like 7500rpm.  It sounded
like a Ferrari Testarossa.  It was tuned for performance; if you knew how
to shift, you could blow the doors off most cars.  But an American car
(even a large one) with a properly set-up V8 would mop the floor with
that Corolla GTS, with no shifting required.  As the driver of the 455ci
SD powered 1970 Pontiac GTO Judge said (in the great car film '2 Lane
Blacktop'): JUST COLOR ME GONE, BABY!  

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Put four overhead camshafts on a 455 cid V8, tune it right, and see what
you can get.

The separate overhead camshafts offer a world of tunability options.
Admittedly, you can do a lot with a single camshaft pushrod engine.

scott wrote:


The 3.9 engine is a revised version of the 3.1-3.4 engines.  The main
differences are no wet intake manifold, all of the coolant is now carried
externally with water crossover style manifolds (Northstar has been this
way from day one), and it has a variable valve timing mechanism on
the camshaft.

What's wrong with pushrod engines?  As someone else mentioned, people
seem to think that OHC engines are somehow "new".  Go have a look
at an aircraft museum and take a look at what was being used in WW 2
fighter aircraft!  Overhead cams, superchargers, turbochargers, fuel
injection, throttle body injection, compound turbochargers.  Probably
some of the greatest engines of the war were radial engines with pushrods.
I believe that most of this technology originated in the 20's.

The OHC engines that GM has put out, without exception, have been
far more costly to repair then pushrod engines.  Consumers would be
better off using the pushrod engines...lot less money when you have to
fix something.

Ian

And this is by no means limited to GM OHC engines Ian.  OHC by its very
nature is more complex and more expensive to repair than a pushrod design.
This transcends manufacturer's lines.

--

-Mike-
mmarlowREMOVE@alltel.net

I respect both your and Ian's opinions, but in this case I do not feel that
OHC engines
are inherently more expensive to make or repair.  They are not particularly
more complex,
in my mind at any rate, do not necessarily have more parts, but also do not
guarantee
better performance than a pushrod OHV engine.

They CAN be stompers.  But, OHC as such, and particularly as articulated by
GM, means
little.

The reason that I make that statement is the cost of any valve related work
which is typically more expensive than with a pushrod engine.  If the engine
is built with a timing chain as opposed to a belt, the reliability is pretty
much equal to a pushrod timing system, but there are still belts out there
and in that there is more expense, if for no other reason than the routine
change required.  With interference designs this becomes a pretty big issue
for those who keep cars a long time.

From a design standpoint, it is much harder to design and build a lower
profile engine with OHC design, thus fitting today's more aerodynamic body
styles, and still keep a decent torque.  With pushrod engines it's easier to
keep a lower head profile and build an engine with a bigger lower end and
more torque.  No need to run it up to such high rpm's in order to stay in
the torque band.

As an aside - I find it nothing short of amazing that NASCAR teams are
consistently and reliably (if that term can ever be applied to a stock car
engine...) building pushrod engines that are approaching 10,000 rpm's.  We
used to think that was impossible.

--

-Mike-
mmarlowREMOVE@alltel.net

I agree with you on the latter point, Mike.  There is a lot of really trick
gear
out there, if you can afford it, that will live under very inhospitable
conditions.

I am a Formula 1 fan, and find it hard to believe at times that they can
push
some of these engines as far as they do.  Race rules with F1 still push two
races per engine (with no repairs allowed), and there are exceptions and
penalties, of course.

These engines routinely turn up to nearly 19,000 rpm throughout the race,
which lasts for something over two hours usually. (For those who are not
into
F1)

They switched the formula from V10 engines to V8s a year or two ago.
I believe they are still 3 litre engines, very special valving systems, and
put out
in the range of 700-800 horsepower...maybe more this season.

HLS@nospam.nix wrote:


Hey, me too!  I'm just glad to finally see Shumacher out
of the F1 arena.  I'm hoping that it will be more interesting
and less of his bs (apologies if you happen to be a Shumi fan).


Yeah....these are very exotic engines.  I still remember when the
Turbo 1.5 liters were around, they approached 1000 hp in
qualifying trim.  Can you imagine?

Ian

You can be sure I was NOT a Shumi fan, Ian.  He was undoubtedly
one of the worlds greatest drivers, but very unsportsmanlike and
underhanded.  His tactics could not be respected.

I am amazed that Renault was able to field a team as strong as the one last
year.
Absolutely phenomenal.

Ferrari proved their durability, but I like to see a strong competition.

Poor old sour faced Frank Williams has been relegated to Ford Cosworth,
which
is like, IMO, sleeping with the town tramp.

We'll keep in contact as the season nears.

HLS@nospam.nix wrote:


Absolutely....oh goodie...I get to "get up" at
5 am in the morning just to see a race!
My wife always thinks I'm crazy to get up that early.
It was difficult over the last two years to do
it as the excitement wasn't there as much, but
I'm hoping that we'll see better racing this
year.

Ian

Fully agree on that.  It is not much fun when one team dominates the way
Ferrari had done.

My wife doesnt complain too much when I turn on the Japanese or Australian
Grand Prix
in the middle of the night ;>)

I can agree with you for Vee engines. But for inline engines, the difference
is trivial, and the OHC engine might actually be easier to work on - just
depends on the cam drive. My 1972 Pinto with the 2L OHC engine was the
easiest engine I've ever dealt with. It was even easier than the 1.6L Kent 4
in my Fiesta (although the Fiesta was easy too).

Ed

@l53g2000cwa.googlegroups.com:


i wouldnt downgrade the pushrod engine so quickly if i were you. especially
in domestics! thru my 30 years of watching and working on detroits better
ideas i find every attempt at OHC a real experiment on their part. on my
part i have found their experiments VERY costly to the consumer (quad 4
ring any bells?) and either underpowered or with the power band in the
wrong dam place.......for my personnal vehicles i have always sought
domestic pushrod engines and walked away from OHC. just my 2 cents......