Greetings from Flagstaff--the '81 Caddy waves hello!

[roto204]

Just a random tidbit of amusement...

Remember my '81 Coupe deVille v8-6-4? Well, I decided (after changing oil and such, and getting a wild hair) to take it up to Flagstaff this weekend, since that's always a good idea with a 26-year-old car and one that you've never driven any distance, right?

It made it just fine, and performed flawlessly, though that's a funny story in its own right.

Several miles outside of Tucson, it felt like the transmission was mis-shifting. I tried modulating the accelerator, and noticed that when I accelerated, the car didn't. This could not be good.

Before allowing myself to become embroiled in panic, I wisely poked the "Active Cyl" button on the computer, and found--to my shock--that the readout said:

4

My jaw dropped. The car had never given any hint that the modulated displacement worked, but then again, I'd never driven on the freeway before, either.

I pushed a little on the gas.

6

Harder.

8

After several seconds, the computer decided that I was playing, and made its preference clear yet again:

4

I had to call my dad and Roger to relay this most unexpected info. After leaving the "Active Cyl" displaying, I learned how to interact with the computer to make sure I got the power I needed when I wanted it, and after twenty minutes or so (and a couple of oopsie 4-6-8-4-6-8-4-6-8 shifts when the computer got confused), I had it dialed in.

Throughout Phoenix, the car clung viciously to 4, but would offer me 6 if I insisted. The trick was to push the accelerator (a lot) to make sure I had 8 cylinders available if I needed power. In short, you can't drive this car without developing a meaningful relationship with the computer--you'll be terrorized by its behavior until you learn to use the information readout to your advantage. If you drive it like a normal car and ignore the readout, you'll go nuts (and probably get creamed by a semi, too, when you try to pass it in 4-cylinder mode).

That said, I got about 23-26 mpg out of a 4100 lb car, and I feel like I got a free lunch out of the universe :-D

Now, wish me luck that my return trip is without incident as well

 

[scott55405]

Thank you for your email, sweetie, and this is just so interesting! How cool.

 

[toggleswitch]

road trip. YAY!

 

[roto204]

Whee!!

Scott--You're welcome--and I'm sorry I was late as usual :-|

Toggle--LOL! Fun! Gratuitous use of petrochemicals

In extra-super-high altitude driving, the car has yielded interesting results. After hard mountain climbs, where the car clings to 8 cylinders, it promptly kicks off to 4 when the climb is finished--a behavior oddly reminiscent of the Northstar heat management of much later. I don't know if that's intentional, but it's helpful for getting rid of that surge of heat that comes after a big climb.

Also, at very, very high altitude (7,000 feet right now), the car seems to note the altitude and gives up on modulated displacement--even in situations that would call for 4 cylinders easily (long, flat spot or a downhill run), it simply refuses to drop out of 8 cylinders (which is appreciated).

The funniest thing is that, in four cylinders, it's just enough to keep the car moving at speed--if the road cants up a tad, you start to slow down, and you go back to six cylinders to recoup some speed. The driving experience becomes one of a neverending feeling of cruise control

Nevertheless, it's fun, and it works! But contrary to Cadillac's insinuation in their sales brochure, I can assure you that you can feel the activation of 4 to 8 cylinders (even if the drop from 8 to 4 is imperceptible).

Kudos to Eaton and GM for coming up with such an incredible idea. If they had a faster computer (the computer on this car communicates at less than half the speed of later eighties models), they might have pulled it off.

 

[westytoploader]

Wow, how neat, and I'd be jumping for joy at the gas mileage! Although I can see how it can be a little disconcerting at times, especially when you're trying to make a pass! Must feel like passing in overdrive on a truck with a 5-speed standard and a V6...I know by experience. No power whatsoever. Thank God I'm not driving anything like that anymore...only V8s for me from now on! LOL

I remember a while back how GM touted modulated displacement as something new with the Suburban...hardly. However I believe on that one you simply pushed a button to run on 4 cylinders, it wasn't 'automagically' done as is here.

Looking forward to seeing this beauty (and possibly taking it for a test drive...;-)) next month!

--Austin

 

[petek]

Sounds like an experience although I think all that roughness would be disconcerting after a while. Our Ram 1500 with the MDS displacement is virtually unnoticeable and I even wonder if it's acutally dropping down to 6 cyl. since there are no lights or gauges on the dash letting you know what it's doing. That I find strange as well them not putting any indicator in there..used to be the more lights and they could add to a dashboard and charge extra for the better.

 

[whirlcool]

The technology has improved over time. One of the early problems with the 4-6-8 system was when you were moving at a very slow speed and needed a boost, say you are crossing a 4 lane highway like what is found in rural areas and when you press the gas to cross, the car moved about 10 feet and died out on you leaving you dead in the water in two of the lanes. I think GM had a recall to fix that problem, amonst others. Eventually Cadillac dropped the technology all together.
But working correctly it does sound like fun!

 

[roto204]

Well...

Well, Allen, Pete, and Austin...

The newer systems do 8/4. They don't bother with the 6, and I can understand why--it's kind of more in the way than useful.

The system is fun when it works, but just to be obnoxious, the car was a HANDFUL on the way back. It didn't reset from the altitude until well into Phoenix, and when it did, it couldn't stay in 4 mode for more than ten or fifteen seconds. It would get confused, and jump all around, making driving a Cadillac feel like herding cats.

I can see why people got pissed and overrode the system Still, when it works, it's fun.

 

[revvinkevin]

My uncle also had a 1981 SeVille V8-6-4. He liked the car, but he felt it never really got the fuel economy he thought it should. No it was not problem free, but he did have the car for probably 6 years.

I used to have a 1980 Fleetwood Brougham (diesel). I really liked the car... sure it was slower then molasses, but it managed to deliver 28-29 MPG at 65 MPH! Amazing for that amount of luxury. Even though the drivetrain was fairly solid with 200K on the clock, the rest of the car was starting to fall apart... so bye bye it went.

 

[roto204]

WOW!

That's awesome, Kevin--that diesel had such a bad rep that to see someone who got good miles out of it is great :-D

I agree--the v8-6-4 probably doesn't deliver the super-amazing economy (though I'm impressed with what I got)--but it is fun that it's all automatic. The original idea on which it was based allowed for disabling of the cylinders manually, but to design such a nifty solenoid device with a Rube Goldberg-esque ECM that does all of the math automatically and tries to spare you the details is pretty neat-o :-D

 

[cadman]

Thanks for the V864 report, sounds like the trip was a blast!

As I understand it, the 6 cyl mode was meant as a transition from 4 to 8 and back since the inherent balance of the V8 isn't real smooth in 6 mode. I even think the ECM staggers the active cylinders when running on anything less than 8 to keep things as smooth as possible.

For those who don't know the story, there were customers who would rather take a hit in the pocketbook than put up with the engine hunting between 4 and 8 cyl. Fuel economy be damned. By law, dealers were not allowed to modify OEM equipment because it would impact EPA figures and certification- But, if you knew the proverbial secret handshake, the tech would snip the wire from the transmission to the ECU, locking out the 4/6 mode.

Today there are a great many 1981 Cads (only year to have this system) with a toggle switch in line with that wire (usually put in by curious 2nd and 3rd owners) to force the engine to run like a regular 1980 368. That transmission wire only goes active if the car is in top gear so the system can never come on unless the car is at highway speeds.

Cool stuff!

 

[roto204]

Awesome!

Thanks for that awesome info, Cory!! :-D That's what we'd thought was the cause of the system "not working"--we found a weatherpak connector with snipped wires, but it's clearly not part of the modulated displacement system...so what it IS for is the next great hunt

And Austin, yes, you may drive the car when you're here ...as may anyone else who's got a license on 'em and no beers in 'em.