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View Full Version : Interesting facts about Hemis.



Karrmann
07-17-2004, 06:40 PM
Did you know that when put through normal driving a Hemi acts like a 4 banger and uses 4 cylenders maybe 3 in going really slow...., but if you go on the freeway, and kisk it in the butt, it uses the all 8 cylenders, so the Hemis are more than you think. please note that this only counts for the new hemis.

SIMPLETON
07-17-2004, 06:42 PM
I take it that you watched the Speed Channel Test Drive: Dodge Magnum, ealier today

Karrmann
07-17-2004, 07:10 PM
acually, a friend told me

d-quik
07-17-2004, 10:50 PM
That is only because of the new Multi-Displacement System used by Daimler-Chrysler.

It has nothing to do with the fact that the engine is a HEMI.


But they have only used it in the Hemi so far, right? Anyway, it's a cool idea, but I want all 8 cylinders firing at all times in my V-8 :D.

EDIT: no it is not

Gnafu the Great
07-18-2004, 09:40 AM
That is only because of the new Multi-Displacement System used by Daimler-Chrysler.

It has nothing to do with the fact that the engine is a HEMI.

But they have only used it in the Hemi so far, right? Anyway, it's a cool idea, but I want all 8 cylinders firing at all times in my V-8 :D.

cls12vg30
07-18-2004, 10:04 AM
Yes the 5.7 liter Hemi is so far the only engine to use the new cylinder deactivation feature. This helps the HEMI achieve a highway economy figure of 26-27 miles per gallon, not bad for a 5.7 V8. So far it seems to work OK, haven't heard about any problems. I say this because back in the early '80s GM experimented with cylinder deactivation on the Oldsmobile 4-6-8 engine, and it was a disaster, the system broke almost immediately.

Fresno Bob
07-18-2004, 11:08 AM
My Daimler used to have the cylinder de-activation feature. Unfortunately, it was unintended and intermittent. ;)

Fresno Bob

Matra et Alpine
07-18-2004, 11:16 AM
IIRC Daimiler or Jaguar did this years ago with the V12.
But can't remember any details. Anyoen else remember ???

Karrmann
07-18-2004, 11:20 AM
i think i remember them mentioning those on tv.

baddabang
07-18-2004, 11:33 AM
didn't cadillac once make an engine that could run on disired cylinders and you could actually choose what ones for it to run on? If I recall correctly it didn't go over to well and they had ship loads of problems. :rolleyes:

Karrmann
07-18-2004, 11:43 AM
yeah, I hope chrysler doesn't have to go through the same thing.

DasModell
07-18-2004, 05:37 PM
BTW . that "Hemi" is not a real hemi :D

http://www.allpar.com/mopar/new-mopar-hemi.html


Today's Hemi is that (a "Hemi") in name only. [Editor's note: Bob is referring to the head design. It is not a true hemispherical head, but looks vaguely like a hemispherical head with parts filled in.]

Egg Nog
07-18-2004, 06:29 PM
But they have only used it in the Hemi so far, right? Anyway, it's a cool idea, but I want all 8 cylinders firing at all times in my V-8 :D.

Man, I'd love to see the design of a V8 that fires all eight at all times... a one-stroke engine would be quite the feat of engineering ;)

KnifeEdge_2K1
07-18-2004, 10:04 PM
i dont think you can have a one stroke engine

it would have to undergoe combustion on both the "up" and "down" part of the cycle

Matra et Alpine
07-19-2004, 03:09 AM
i dont think you can have a one stroke engine

it would have to undergoe combustion on both the "up" and "down" part of the cycle
Not what Egg Nog means.

A "big bang" V8 wold have all cylinders on the same cycle.
So all 8 would go through induction at the same time, all 8 would go through comperession at the same thime and then ignition and exhuast.

The flywheel would have to be HUGE to keep it running during the compression stroke and the whole engine and vehicle would leap in the air on the ignition :)

Yep, get your point Egg Nog it would be great fun to watch !!!

Matra et Alpine
07-19-2004, 03:13 AM
Man, I'd love to see the design of a V8 that fires all eight at all times... a one-stroke engine would be quite the feat of engineering ;)
NOt stroke, but cycle - the Atkinson engine does it's complete cycle in one turn of the crankshaft on one cylinder :) A great feat of British engineering to try to circumvent the Otto patent !! Didn't really take off until now - latest variable valve controls keep the inlet valves open longer to emulate the Atkinson cycle. The Toyota Prius uses this in it's "real" engine.

Egg Nog
07-19-2004, 03:50 AM
i dont think you can have a one stroke engine

Woah. It's almost as if I already implied that. ;)


Matra, wouldn't it be considered a one-stroke if it was firing all 8 at all times? This is to say, of course, that the only stroke is the power stroke. Of course this is impossible, but naturally, that was the humour of it all, wasn't it?

Gnafu the Great
07-19-2004, 07:08 AM
Man, I'd love to see the design of a V8 that fires all eight at all times... a one-stroke engine would be quite the feat of engineering ;)

You know what I meant ;) :D.

Matra et Alpine
07-19-2004, 07:52 AM
Matra, wouldn't it be considered a one-stroke if it was firing all 8 at all times? This is to say, of course, that the only stroke is the power stroke. Of course this is impossible, but naturally, that was the humour of it all, wasn't it?
hmmm, it gets a bit hard.

Stroke and cycle have become synonomous over the years becuse we're used to the Otto-cycle engine. So there can be some confusion.

But no, a one 'stroke' would imply everthing happened in one stroke of the piston. Clearly it can't in practice - I'm sure you could come up with some theoritical combustion chamber design with multivalves opening passages for a theoritical one stroker. But in the real world, nope.

Otto-engines need the 4 'cycles' - intake, compression, combustion, exhuast.
Each cylinder follows the same cycles just at a different time.
The number of cylinders doesn't affect the number of cycles or strokes of an engine.
The crank determines when the different time of each cycle is for an individual cylinder.

NoOne
07-19-2004, 09:20 AM
Years ago I had several 2 stroke dirtbikes, performance is amazing!!! Anyone who has ever ridden a Suzuki RM250 (or similar bike) knows exactly what I'm talking about, there is no greater thrill than throwing a 30ft rooster while having the front wheel a foot off the ground .... except maybe doing it on the local golf course. ;)

I think a 2 stroke car engine would be phenomenal, even if the oily smoke was not enviromentally friendly. Wouldn't be too much worse than a 15 or 20 yr old diesel but with gobs of power and none of that crap diesel rattling. ;)

In keeping with the general direction this thread has taken, imagine a 2 stroke V8 with the left bank firing opposite the right bank leading back through 3" headers and straight pipes :D .... I'm sure there would be no better way to drown out the local Joe Ricer and his Eminem powered Civic.

Egg Nog
07-19-2004, 05:32 PM
But no, a one 'stroke' would imply everthing happened in one stroke of the piston. Clearly it can't in practice - I'm sure you could come up with some theoritical combustion chamber design with multivalves opening passages for a theoritical one stroker. But in the real world, nope.

Just out of curiosity, did you read the last sentence of the post that you quoted? ;)

Matra et Alpine
07-20-2004, 02:37 AM
Just out of curiosity, did you read the last sentence of the post that you quoted? ;)
Sorry, Egg Nog, it's just the analytical engineer in me...
In THEORY it may be possible to design one but it would be impractical - ie little power, next to no torque, major timing complexities.
So it was the "impossible" in your post that had me thinking ... "well it's not IMpossible, so I'll explain"
Sorry if the extra effort wasn't appreciated :(

Matra et Alpine
07-20-2004, 02:52 AM
I think a 2 stroke car engine would be phenomenal, even if the oily smoke was not enviromentally friendly. Wouldn't be too much worse than a 15 or 20 yr old diesel but with gobs of power and none of that crap diesel rattling. ;)
2-strokers give phenomnal power and there were efforts done which would have enabled them to meet current emissions.
But 3 things. First, a believe that after generations of only pumping petrol, people would either NOT buy a car where they had to add oil regularly as they would think it was faulty.
Secondly, they would forget to add oil and the engine wold wear horrendously.
third, uncertainty it could meet future emissions.
They can't use cat's because of the oil in the mixture, but they get the emissions lower by lean burn.

SImplest comparison on the engine performance - MotoGP ran a season where the 500cc strokers and the 1000cc 4-strokes and it was close.

So an engine half the size produced almost double the power ( ~10% down ).

In keeping with the general direction this thread has taken, imagine a 2 stroke V8 with the left bank firing opposite the right bank leading back through 3" headers and straight pipes :D .... I'm sure there would be no better way to drown out the local Joe Ricer and his Eminem powered Civic.
uurrrghh, a big ban V8 would be a disaster. Lose all the balance that a V8 brings for no benefit. motorbies went through all these configurations 50-80 years ago.

Galbusera did a V8 2-stroker. ( Damn the site with info on it has disappeared :( )

Once you get more cylinders I think the benefit becomes less.

For V8 500cc race engine nobody was better than Moto-Guzzi 500cc. 160+mph in 1955. On the rubber availabel then THAT is scary :) see http://www.kunis.nl/bikesuk/index.html#Moto%20Guzzi ( that site has s few other 'interesting' bikes showing how advanced motorbike manufactureres were - supercharger, radial, V8, V6 the lot :) )