Variable Displacement for Older Cars?

I am sure when we get to Megasquirt-n-spark-n-variable-displacement it will be better than this.

1981 Cadillac Fleetwood V-8-6-4

I don't see why it can't be done, but it won't feel very nice. The modern vehicles with this technology typically have fancy motor mounts that counteract the imbalances, do they not?

And the Cadillacs shown in the picture above had a very UNRELIABLE control system when the motor went into less than 8 cylinder mode....

Rog

The thing with variable displacement is that it also shuts the valves for the affected cylinders. This is partly so the exhaust doesn't get pumped full of raw air, and partly so the cylinder never sees vacuum which will draw oil up past the rings, which will eventually foul the spark plug. (They shut the valves off at the right time in order to trap a volume of air in the cylinder)

If you want a cheap variable displacement setup, get forced induction on a small engine. Low displacement at cruise, high displacement when you boot it.

What seems odd now, at least to me, is that GM put time and engineering into that worthless V8-6-4 hardware instead of developing a suitable automatic transmission with an overdrive that could then be useful to many other vehicles produced by GM. Instead they put out this stuff...

Two engines? Maybe?

pres589 wrote: What seems odd now, at least to me, is that GM put time and engineering into that worthless V8-6-4 hardware instead of developing a suitable automatic transmission with an overdrive that could then be useful to many other vehicles produced by GM. Instead they put out this stuff...

GM has had overdrive transmissions available in pretty much everything since the early 80's, and they are being used in pretty much every kind of vehicle out there behind every engine you can think of- there are companies that specialize in adapting them to other cars. well, at least the rwd versions, anyways.

if you build a car right, you don't need any complicated mechanical devices or electronic trickery to get good fuel economy- build an engine that makes good torque down low and gear the car so it keeps the rpm's nice and low. all that extra technology just adds mass and complexity- and more things to go wrong.

a few years ago, i had a completely stock 86 Chevy Caprice with an L69 305, 700r4 trans, and 2.56 gears that would average 26mpg no matter how i drove it. it would get 28-29 on long interstate drives with the AC blowing cold and the cruise control set at 80. it was like driving a plush velvet couch down the road... it wasn't fast, but thanks to the steep first gear of the transmission, i wasn't afraid to pull out in traffic and thanks to the torque of the 305, i was able to pass people if they got in my way. that was a good car right up until the head decided to crack, and i was too lazy to try to find another head for it. i gave it to my cousin for use as a demo car..

pres589 wrote: What seems odd now, at least to me, is that GM put time and engineering into that worthless V8-6-4 hardware instead of developing a suitable automatic transmission with an overdrive that could then be useful to many other vehicles produced by GM. Instead they put out this stuff...

The 4100 was one of the first applications of the 200-4R transmission.

My favorite problem that the V8-6-4 had was that the exhaust manifolds would warp! I wonder how they got around that problem, I don't see why modern variable-displacement engines that don't shut off an entire bank won't also have this as an issue. (V6s you can shut off one bank, V8s you have to take two from each bank)

pres589 wrote: What seems odd now, at least to me, is that GM put time and engineering into that worthless V8-6-4 hardware instead of developing a suitable automatic transmission with an overdrive that could then be useful to many other vehicles produced by GM. Instead they put out this stuff...

The price of gas wnet back down, a lot, and it didn't make economic senese-then-to persue overdrive transmissions. People were happy to buy what GM offered.

My 1966 Cadillac had variable displacement. It would just run on anywhere from five to eight cylinders. It seemed to be oil-activated by deactivating a spark plug, and when I installed an MSD ignition I seem to have broken the system. Now it only runs on eight.

novaderrik wrote: if you build a car right, you don't need any complicated mechanical devices or electronic trickery to get good fuel economy- build an engine that makes good torque down low and gear the car so it keeps the rpm's nice and low. all that extra technology just adds mass and complexity- and more things to go wrong.

This. Simplifcate and add lightness and you'll see better fuel economy.

ReverendDexter wrote:

novaderrik wrote: if you build a car right, you don't need any complicated mechanical devices or electronic trickery to get good fuel economy- build an engine that makes good torque down low and gear the car so it keeps the rpm's nice and low. all that extra technology just adds mass and complexity- and more things to go wrong.

This. Simplifcate and add lightness and you'll see better fuel economy.

and play with the aero. it's cheap to experiment with blocking things off.

Knurled wrote: The thing with variable displacement is that it also shuts the valves for the affected cylinders. This is partly so the exhaust doesn't get pumped full of raw air, and partly so the cylinder never sees vacuum which will draw oil up past the rings, which will eventually foul the spark plug. (They shut the valves off at the right time in order to trap a volume of air in the cylinder) If you want a cheap variable displacement setup, get forced induction on a small engine. Low displacement at cruise, high displacement when you boot it.

How does this work on an OHV V8?

Just curious, never looked into it.

Just start with a V8, then remove plug wires until you reach the level of slowness you desire.

Just start with a V8, then remove plug wires until you reach the level of slowness you desire.

or put an old person behind the wheel

To address a number of replies at once; from the basic research I did, the V8-6-4 motor was based on the older Cadillac big-block motors, and the HT4100 didn't do cylinder deactivation (because it worked poorly) and we got new exciting problems with the HT4100 instead. So I guess I'll stick with it; it seems odd that they burned time and money on developing the cylinder drop technology instead of just pushing resources to something useful like an overdrive automatic. And it would seem like they did indeed do that eventually, since the HT4100 had a bellhousing common to other contemporary GM engines so the 200-4R could be used with this or other powerplants in the parts bin.

Novaderrik: I completely agree with the simplify & add lightness concept to attaining good fuel economy although there's something to be said for technology helping things along. I wonder what, say, an aluminum 5.3 'truck' LS motor in your old Caprice would do on the highway...

triumph5: Actually if you look at owner satisfaction with these cars and what the 80's did to GM market share, one might think people weren't actually that happy to be buying GM products. US market share in 1980 of 45% reduced to 35% by 1990 doesn't paint great pictures; http://www.nytimes.com/2009/06/03/business/economy/03leonhardt.html

Indeed it was the right idea at the wrong time and wrong technology.

I do kind of disagree with the low revs using a big engine though. Honda and the others have proven you can get high revs and still get good miliage

pres589 wrote: What seems odd now, at least to me, is that GM put time and engineering into that worthless V8-6-4 hardware instead of developing a suitable automatic transmission with an overdrive that could then be useful to many other vehicles produced by GM. Instead they put out this stuff...

What seems even odder are EGR valves, thermactor air injection systems, feedback carbs, carbs in general, 8-1 compression, and 2 valves per cylinder.

I mean, what were they thinking???

Hindsight being 20/20, you'd think you could come up with something a little better to bitch about.

Give credit where credit is due. They're using variable displacement technology now. Cadillac was doing it over 30 years ago.

like I said.. right idea, wrong time and wrong technology. Have to remember in the 70s and early 80s.. they were predicting the demise of the internal combustion engine due to ever tightening emissions and fuel economy requirements.

Today we have 4 cylinder engines putting out what big blocks used to

Interesting note - we've seen 35 mpg on extended road trips in our Miatas. That's both the V8s and 400+ hp four cylinders. The V8 cars are loafing, pulling about 2000 rpm at 80.

Meanwhile, when traveling in convoy with one of the high-hp turbo Miatas, I got almost the exact same mileage in my classic Mini. Of course, I was wearing earplugs and didn't quite have the same horsepower on reserve...

mad_machine wrote: I do kind of disagree with the low revs using a big engine though. Honda and the others have proven you can get high revs and still get good miliage

No, what Honda's proven is that you can get decent hp with a low-displacement N/A motor. If you keep a VTEC motor on the big lobes for a whole tank, your mileage is still gonna suck.

emodspitfire wrote: And the Cadillacs shown in the picture above had a very UNRELIABLE control system when the motor went into less than 8 cylinder mode.... Rog

Also, even when functioning properly, they switched back and forth between configurations so many times that the whole system was worthless.

zomby woof wrote: What seems even odder are EGR valves, thermactor air injection systems, feedback carbs, carbs in general, 8-1 compression, and 2 valves per cylinder. I mean, what were they thinking??? Hindsight being 20/20, you'd think you could come up with something a little better to bitch about.

Meanwhile, EGR valves are so useful for reducing emissions and increasing fuel economy that they are still in use today. Many many MANY cars have air injection, too. If it's European, it more likely than not has it. Same for California emissions for US makes.

I don't know what's wrong with carbs, at least contemporarily. VW (and Chevy too) did a decent job of proving that cheap FI sucked, and the Euro-cars had a somewhat workable fuel injection (K-jet) that rather depended on having a vast army of low-waged craftsmen. L-jet was new on the scene and you only saw that in upper end cars, too. (280Zs had it. Did 510s?)

In reply to Lugnut:

Back in the day I rode in one of those a few times. Seemed to work like a charm, from the passenger seat. When the cylinder deactivation failed, you only had to cut one wire and presto, back to a GM 307 (305?) V8. I heard that owners spent buckets of $ changing out the cylinder heads instead. The technology's rep was terrible; too bad it didn't work better.