Idea for a 40+ mpg SVX....
 

So I was reading a bunch of old magazine reviews on the SVX, and noticed something interesting in the September '91 Automobile Mag review of the car:

"At full throttle, the flat-six revs right to the solid red at 7000rpm before shifting up, and although first-to-second and second-to-third shifts are smoothed by a shift-energy strategy that cuts fuel to three cylinders momentarily, the next ratio hooks up pretty quickly."

Sept '91 Automobile Mag Review

Personally, I'm not that concerned with fuel economy (I started thinking of ideas after svx_commuter's famous thread), but that shift-energy strategy gave me an idea - displacement on demand!

Since some members have been able to splice switches for locked 4wd, 50/50 awd and fwd modes, wouldn't it be possible to splice a switch for the wire that'll run from the TCU to ECU engaging this 'shift-energy strategy'?

Now, this wouldn't be a switch to engage when moving the SVX off from a dead stop, but whilst cruising on the highway in 4th, when the switch is flipped and 3 cyclinders are shut down, it should allow fuel economy to increase significantly... :)

I know several manufacturers like Chrysler, Mercedes Benz, VW, etc. all have displacement on demand technology that's starting to trickle into some of their production cars. Wouldn't it be cool to use the technology Subaru developed for the SVX some 15yrs ago that will be still cutting edge today? :confused: :)

Just a brain-storming idea I felt like sharing... :o

-Chike

I haven't read up on how the more recent displacement on demand schemes work, but I am positive that they entail more than simply cutting fuel to half of the cylinders.

Go disconnect three of your coils - hell, just one coil - and tell me how your engine runs. :p

i think that if your worried about saving a few bucks on fuel, the SVX probably isn't the car for you. :D

Interesting. I can't imagine what the newer technology could entail beyond cutting fuel to selected cylinders, but then...?

I do know there was a Cadillac "4-6-8" engine, in the early-to-mid 80s, I believe, that apparently worked by mechanically disengaging intake valves depending upon the load on the engine. (My description is an oversimplification for a horribly complicated arrangement, to be sure.) In my understanding, the concept proved to be a solid dud.


dcb

It looks like the newer GM DOD engines are all pushrods. When cylinders are shut off, they seem to disengage the pushrods so the valves aren't actuated and the cylinders aren't compressing anything.

Now what I wonder is whether the Chrysler Hemis are pushrods, and whether they use the same sort of system.

Chrysler Hemis are pushrods. In the Car & Driver review of the new Hemi 300C, they talked about the DOD system used in that 2 ton car that allows it to return 25mpg on the highway...

-Chike

All the DoD engines from GM and Chrysler use oil pressure to push out a pin and colapse half the hyrdallic lifters... the lifters then don't transfer any of the cam motion to the pushrods/valves. Also of course... they cut fuel/spark. Colapsing the lifters helps prevent pumping loses.

Smarty pants! ;) You think I'd swap in 4.11 gears if fuel economy was a concern... :p

I'm just fascinated by technology, and after reading that blurb, wheels started turning in my head.

-Chike

Stock shifts (non power mode) with the 4EAT aren't the quickest and I'm sure they must last at least 0.5 seconds. I wonder what happens to the 3 cyclinders that are shut down during that period of time??? :confused:

-Chike

It wasn't that bad, I think fuel economy jumped from 16 to 18 or somethin like that...:eek: :D

My friend had a 20+ year old 8-6-4 engine... the dod still worked... the mechanical parts worked great. But the electronics where really the limiting factor... I would assume its hard to control all that displacement on demand crap w/ less computing power than a atari 2600.

I don't know that the SVX does it during every shift. It might only during the 1-2, or while in power mode.

Road & Track.??????????
 

Yes Nick, I think R&T got that part wrong too. I believe it does this only when the engine is on cold start and the idle speed is high. It cuts the fuel to alternate cylinders to prevent the thump, when you select D or R.
On the normal shifts, it just does the torque control thing.

Harvey. ;)

That sounds entirely reasonable. I wondr if the FSMs say anything about it...

i fixed that with the smallcar shift kit. ;)

before i put it on, the shifts were smooth as butter - you can really tell the difference, even at just the preset setting, which is what i left it on.