kcducttaper

I've wondered how difficult it would be to just make my own cylinder deactivation stuff and stick in on an LS1, or preferably and LS3. The basic idea is to have 4 of the fuel injectors run through a relay of sorts and wire up a small control module that cuts off power to them at certain programmable thresholds. When the speed of the vehicle is over say 40 MPH and the throttle is at 20% or less, it will shut off the injectors. When the speed dips below 37 MPH or the throttle is pushed beyond 30%, it will kick those 4 back on. This leaves a bit of a buffering zone so it's not kicking the injectors on and off and on and off and on......etc. I'd also have a switch on the dash so I could just switch them all on when I wanted to.

The idea behind this is to give me a little better fuel economy with a manual tranny. From what I gather, GM only offers that in their automatic trannys for some reason that makes no sense to me. My brother graduated in computer engineering and I'm just about done with computer science/information systems, so I'm pretty confident we could wire something up like that with relatively little fuss. I'm just wondering if anyone else has tried it, if it's going to boost my mileage at all, or if I'm just going to blow my motor to smithereens and be arrested for illegal discharge of millions of deadly projectiles.

Pocket

iTrader: (24)

Give it a shot and post your results

I can tell you directly that its ALOT more complicated than that, but would love to be proven wrong

FWIW, there is nothing stopping you from using a VVT/DOD engine with a manual trans. You might want to keep in mind many DOD owners disable the feature for a reliability reason over efficiency

Invent a decoupling crankshaft then disabling cyls would be extremely appealing

kcducttaper

I forgot to mention the air flow stuff, so something would have to be done to keep the air/fuel mixture correct.

I was under the assumption that those would only work with auto trannies, but perhaps I'm wrong on that. It would be a lot easier to go that route though if it's doable.

I haven't heard of any reliability problems on them, so would you care to elaborate a bit on that?

TKR 88 GTA

Well isnt the wat GM does it with the cylinder deactivation is they leave the valves opening and closing? It makes it act as a giant air pump and because of the cylinder they pick to shut down it actually cools the cylinder next to it? iirc thats how it works lol

My only other thing is how are the oxygen sensors gonna act does this lack of combustion throw off a reading the sensors would see? Or would it even matter.

Great idea tho would love to see that happen! Make it happen! Lol

kcducttaper

I'm sure they do something with either propping the valves open, or switching to a different state in the computer so it doesn't freak out by the vastly different O2 readings. I'm just not exactly sure how they do it off the top of my head. I'm thinking perhaps to get a current DOD motor and build a little box to lie to the computer and make it shut off the cylinders at the appropriate times. I haven't really done a ton of homework on this; it's just a cool idea at this point. I'm still curious about the reliability issues mentioned though.

VAN454

Actually the valves stay closed, they have collapsable lifters in the rear cylinders. The reason they didn't use them in manuals is an auto smooths the transistion from one mode to the other. With a manual you could feel the cylinders shutting down and starting up.

kcducttaper

Interesting. It seems like I could just tap into the lifter circuits and the injectors and call it about good. I can feel it going from 4 to 8 and back in my dad's pickup (5.3L). Surely using it on a manual can't be all that much rougher at speed....?

InfernalVortex

iTrader: (4)

You have to replace the lifters to special ones that deactivate on command. Plus even GM (not to mention Cadillac) has issues with making it reliable.

http://www.chevytalk.org/fusionbb/sh...d/193862/tp/2/

Feel free to read the rest of hte thread. The dealership pretty much rebuilt his engine because of how much oil it was burning and how low compression was on the 4 cylinders that get deactivated.

Not really worth the headaches if you ask me.

Chris Etemadi

The DOD system the GM used is very cumbersome and I think much better options are out there, I know early on they had a lot of lifter issues. I worked at a GM dealership in college and they were constantly coming in with valvetrain problems.

Your time would be better off looking into a cam-in-cam configuration that would alow for variable valve timing with the intake and exhaust lobes independent eachother. The variable LSA will allow for more efficient volumetric efficiency throughout a much larger engine speed range.

I was actually surprised this wasn't coupled with the direct injection on the new LT1. The VVT they incorporated still has the intake and exhaust lobes fixed on a standard cam.

Or even better, look into the Fiat Multi-air system. This system would be an awesome addition to the new LT1's direct injection. and could possibly be a modular addition if it could be incorporated into the valley cover.

kcducttaper

I guess I hadn't really thought much about the temp difference and oil getting through there. Perhaps a good variable valve timing setup would be better after all. Correct me if I'm wrong, but I believe the ZL1's LSA engine is basically the SS's LS3 with a blower on it. Does the LS3 have the VVT on it? Since LS3 camaro's are a little hard to find, I'll probably grab an LS1 camaro, do whatever other upgrades as planned, then upgrade to an LS3 a couple years later. My end goal is a manual LS3 powered camaro pushing 500hp naturally while getting mid to upper 20 mpg's (or even 30's) on the highway after smoking my dad's S2000 at the track.


The LT1 looks pretty sweet with the direct injection, but if it does indeed turn out to be non-tuneable like they claim, count me out. I expect someone will crack it in relatively short order, or just make a new computer for it.