Cylinder deactivation discussion

[diesel_john]

maybe that's what speedemon247 does, and maybe its easy for himorher. never the less we'd like to do your mods too. run'em by us. I have always wanted to put 4 space saver spares on my vett just to see how much I am losing with the foot wide tires.

[MetroMPG]

Originally Posted by nemesis

I wouldn't waist my time on this, there are easier/more efficient mods.

I wouldn't discourage anyone from tackling a technically challenging / less efficient mod if they're serious about pursuing it and have the skills.

[nemesis]

Originally Posted by MetroMPG

I wouldn't discourage anyone from tackling a technically challenging / less efficient mod if they're serious about pursuing it and have the skills.

I wasn't discouraging anybody, I was say hey if you want to polish a turd, go for it, but in the end it'll still be a turd. Instead of pulling push rods and file camshaft lobes, you'd be better off pulling the whole engine out and putting a smaller 4cyl engine in with a forced induction. Voila, you have a 4cyl engine with max hp output of a v8, that will still get 4cyl gas mileage.

[diesel_john]

Interesting point nemesis, what kind of mileages are we talking here? My specs. 18 yr. old technology, paid 10k 10 yrs ago, drove 48,000 miles, still worth $6,500. mileage 30mpg freeway trips, 24mpg daily driving. 1/4 mile 14 sec@100mph. Insurance 220/yr. Are turds aero efficient, BTW?
i don't blame you for being critical of the vett, but since it's an American icon it's hard to deicon it. is that a word?
i would like to see much smaller 3 & 4cyl. engines, (under a liter), but don't know about durability. What is your displacement?
Some confusion, we were taking out pistons on the VW, but just computer programing on the vett.
The cyl. deact. is computerized now.

[nemesis]

Originally Posted by diesel_john

Interesting point nemesis, what kind of mileages are we talking here? My specs. 18 yr. old technology, paid 10k 10 yrs ago, drove 48,000 miles, still worth $6,500. mileage 30mpg freeway trips, 24mpg daily driving. 1/4 mile 14 sec@100mph. Insurance 220/yr. Are turds aero efficient, BTW?
i don't blame you for being critical of the vett, but since it's an American icon it's hard to deicon it. is that a word?
i would like to see much smaller 3 & 4cyl. engines, (under a liter), but don't know about durability. What is your displacement?
Some confusion, we were taking out pistons on the VW, but just computer programing on the vett.
The cyl. deact. is computerized now.

I am sure you can take a geo 3cyl motor and turbocharge it and it'll still get the same mileage as n/a geo gets, but the power at 15psi will basically double. Don't get me wrong, I like to see car manufacturers come up with good ideas, I like fords 3.5L turbo motors, but gm/mopar deactivation is not very good in my opinion, because there are still frictional loses inside the motor, weight of a whole motor, and 10% gain in economy with 50% loss of power just doesn't sound good to me. You want economy, put a $2 block of wood under the pedal, bam 30% gain in economy, haha.

I don't know about you, but I've thinking about how to improve the ice efficiency ( 20% is just not very efficient) and kinetic energy recovery systems that could gain 20%+ in the economy.

[JoshuaM]

Hi - new here - registered just for this thread.

Never tried - but I'm about to.. on my 6 inline 2 liter block.

I don't see the issues with deactivation, this is my train of thought:

* Must run on open loop mode - meaning no O2 feedback to ECU (my luck - '88 BMW 6-banger)
* Must alternate the cylinders fired and not fired - on average there is no issue in temp/oil/water/compression whatnot I've seen in this thread
* For best results - miss as many beats as you can to run wide open throttle at cruise - so I'm thinking of a dial which I basically can set the number of missed beats averaged over 6 cyl while keeping the car floored at cruising (3000 rpm) to set my required power output to keep steady. At WOT - I really don't think the non-fired cylinders are wasting a lot of energy - just a spring with air. They are actually required to keep the fuel metering system working in the proper range, the air flow meter.
* Disconnect the throttle cable from the AutoTrans to avoid downshifting - force TC lockup
* Throw in Shell Fuelsave or any one with special lubricants to keef friction losses minimum.
* Install a big red toggle switch in the middle of the dash - ON(SAVE)/OFF(GUZZLE) - instant back to normal operation, in case my wife wants a 'normal' car to drive in.

This probably requires tinkering with the MegaSquirt fuel injection computer & software, but by no means impossible I was just thinking.

How about that? Does this sound insane? I'm expecting 20-30% improvement based on IC efficiency charts.

Regards Joshua

[Frank Lee]

Does this sound insane?

Yes.

Seriously, cutting the spark and/or cutting the injectors has been investigated to death. It does NOT work. To do a proper deactivation you need to keep the valves closed too. I don't see how you are going to do that with a dial.

[JoshuaM]

Frank,

Thanks, - that's important to know before I take the whole thing to bits. Just for my understanding - I couldn't find a logical/satifactory storyline on why one should keep the valves closed fo deactivation to date - pumping losses yade yade are mostly valid for partial throttle only, right? Any mechanical losses I'm quite happy to accomodate - can't see that being more than 500W on the valvetrain.

So - why again should I keep the valves closed?

Apologies in advance for rolling eyes at your end,

[Frank Lee]

Short answer is no pumping losses for cylinders that aren't flowing anything. Where there is flow, there is pumping loss.

Better answer is do a search on this topic and see the discussions.

[diesel_john]

back in the 70's i deactivated the valves on two cylinders of my civic, and the mileage wasn't measureably improved. plus i had to drive in the truck lane.
I think the most efficient IC engines are the big bore, slow turning, compound turbo'd, diesels in trains and ships. around 30% Of course constant speed with electric drive trains not transmissions.
So one might infer that reving a smaller engine to high heaven to get enough power, probably won't help your efficiency. more fiction
and turboing a Geo to 15psi might shorten the life.

Chevy shuts down the same four cylinders all the time by collapsing the valve lifters and not energizing the fuel injector.