Displacement on demand

[DarkoNova]

How exactly does this work? I saw a block on ebay from a newer GM truck/suv (forget what, exactly) and it said it had no provision for it. I was kind of thinking of getting a truck block that had it so that I could get insane mileage. :D



Would it work well in a performance application? I plan on turbocharging it eventually. Just wondering if it's something I should even worry about.

Matt

[CamaroAJ]

it works using oil passages to 2 cylinders on each bank and have kinda like a on/off solenoid going to the lifters, when there pressured there are pins in the lifter that are pushed in and the lifter will not open the valve. when the PCM turns on the solenoid it turns off the fuel injector but not the coil. the PCM will only let the engine run in 4cyl mode for 10 mins then it turns it off for 2 mins and back on for another 10. unless you use the entire wire harness and PCM from a doner car it will not work and will stay in V8 mode. there is more to it like throttle position and engine temp. and as for a turbo i'm not sure how it would work.

[dannyho]

If you're doing a custom tune with an aftermarket efi, using a wideband to monitor A/F you can get pretty good mileage. You have to realize that the most power, best mileage, and lowest emission, the latter of which is waht oems tune for, are all different A/F ratios. I've been doing some research on this, and for steady state RPMs with low load and moderate RPMs, kind of like highway driving, they've been tuning safely for as high as 15.5:1 afr. In the tuning world this seems to be pretty much standard practice, but you have to have the tools to keep you from crossing the line and hurting your engine. Check out www.efi101.com and their forums. They have a ton of tuning tips and some basic stuff for mileage. Also there was a big technical forum dedicated to getting better fuel economy from engines today, but i can't find it now. They were doing some neat stuff, involving heating the incoming air/fuel charge (sounds wierd huh?) but they were getting 70+ mpg with respectable power. without using electric motors of course.

[DarkoNova]

they were getting 70+ mpg with respectable power. without using electric motors of course.

That's waaaaaaay more than I was looking for. I was just hoping to get around 18-20 in town and maybe 30 highway. I've heard that those numbers are actually possible with just an LS type engine and some form of overdrive, but I figured the DOD would definitely help (plus just saying I've got a 40 year old car with DOD that gets 30+ mpg would be cool ).

Matt

[dannyho]

yea some of those ideas were pretty out there, and got very technical to the point where you couldnt do it without a degree, but getting high 20s seems possible, you just have to spend a hell of a lot longer time tuning for part throttle mid RPMs, this is where a good system with good software comes in handy.

almost forgot to say theres a thing called overrun fuel cutoff thats a function built into a lot of the units. basically what it does is cut the fuel when the rpm is above a certain number and throttle position is below a number. So when ur coming to a stop off the highway the fuel is cut when you let off the gas and is reintroduced when the rpms get low enough. this is good for a few points, helps in city driving too I would think.

[DarkoNova]

Thanks for the info. I probably won't bother with it. I'm sure the difference will be substantial compared to my 14-15 city mpg right now.

Matt

[68sixspeed]

I'm supose to get "miles per gallon" not gallons per mile?? Gee, maybe I should do an LS motor for my project car...