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5.3 engine gas mileage? Convert pre 2007 to DOD

Hammer

Full Member
Joined
Sep 12, 2005
Messages
93
Location
McHenry County,IL
Has anybody heard of a conversion kit for the new 05 and up e-85 5.3 engines that will allow you to have your engine shut off half the cylinders when not under a heavy pedal. the reason I ask is because I met a guy at the gas station who bought a new 07 Tahoe that has the e-85 5.3 in it and is getting 30 miles to the gallon on gas. He hopes to get close to that on e-85. let me know if anybody has heard of this kit.
 
No conversion kit, but the new , 2007 models do have the Displacement on demand deal that shuts down cylinders. I think the guy is mistaken though, as the E85 will get 30% less mileage.
 
Maybe pester the EPA so they will bug GM to offer a retrofit kit Dual fuel & DOD.

It would be handy. But no doubt a bit pricey as the engine may need to be replaced if the lifters & shutdown control parts won't retrofit.

I just don't know what they would need yet.. :( ???
 
How does it work?  On an "off" cyclinder the injector is shut off and the coil pack doesn't send juice to the sparkplug.  The computer needs to know when to switch modes.

It doesn't seem like much off a change to me.

My other SUV had a ferret eat two of my spark plug wires.  It was a DOD V6 to V4 (cyclinders 1 & 3 were dead).  Of course it was pumping gas to the dead cylinders and the uneven power of the other four made it buck like crazy.

JP
 
I thought the whole displacement thing was an option on the 07's, and was expensive...
 
Hammer said:
Has anybody heard of a conversion kit for the new 05 and up e-85 5.3 engines that will allow you to have your engine shut off half the cylinders when not under a heavy pedal. the reason I ask is because I met a guy at the gas station who bought a new 07 Tahoe that has the e-85 5.3 in it and is getting 30 miles to the gallon on gas. He hopes to get close to that on e-85. let me know if anybody has heard of this kit.

Not to doubt the guy, but 30 mpg on a vehicle rated at 16-21 seems to be a bit of a stretch.

Just me though.

JP
 
TurboRegal said:
I thought the whole displacement thing was an option on the 07's, and was expensive...

Yes to #1 and no to #2.  (its free, all of the 2007s big SUVs have it stock).

Now that I think about it some more, the fuel delivery system would have to be changed on an older truck, since the fuel rails deliver fuel to entire bank at once, the individual injectors can't be individually controlled.

JP
 
There is more to DOD than just shutting off the fuel injector and spark; a solenoid operates an oil circuit passage which disables the valve lifters on one half of your engine, so the intake and exhaust valves remain closed on one bank of cylinders.  The pistons in those cylinders just compress the air trapped in the cylinders over and over, using the air as a "spring" to force the piston back down the bore after each compression stroke.  Additionally, the throttle blades open to allow more air to the cylinders which still operate normally.  DOD actually works by opening the throttle blades during low-load, low-throttle conditions, reducing pumping losses on the intake side of the engine (you would see it as lower vacuum in the intake).  IOW, the engine is not having to work as hard to suck air past nearly-closed throttle blades so it takes less fuel to produce a given amount of horsepower.

The ignition coils, fuel injectors and throttle body could be controlled by a computer (or tuning) upgrade, but I dunno if the pre-DOD engines can be retrofitted with the hardware to disable the valves.  If they could, I agree the EPA (or Congress, or somebody) should require GM to sell the kits at cost or cost+1%, and have dealerships install 'em at a low set rate, or give equivalent tax breaks to consumers who agree to retrofit.
 
mountainstoner said:
There is more to DOD than just shutting off the fuel injector and spark; a solenoid operates an oil circuit passage which disables the valve lifters on one half of your engine, so the intake and exhaust valves remain closed on one bank of cylinders. The pistons in those cylinders just compress the air trapped in the cylinders over and over, using the air as a "spring" to force the piston back down the bore after each compression stroke. Additionally, the throttle blades open to allow more air to the cylinders which still operate normally. DOD actually works by opening the throttle blades during low-load, low-throttle conditions, reducing pumping losses on the intake side of the engine (you would see it as lower vacuum in the intake). IOW, the engine is not having to work as hard to suck air past nearly-closed throttle blades so it takes less fuel to produce a given amount of horsepower.

The ignition coils, fuel injectors and throttle body could be controlled by a computer (or tuning) upgrade, but I dunno if the pre-DOD engines can be retrofitted with the hardware to disable the valves. If they could, I agree the EPA (or Congress, or somebody) should require GM to sell the kits at cost or cost+1%, and have dealerships install 'em at a low set rate, or give equivalent tax breaks to consumers who agree to retrofit.

If you just cut the fuel and left everything else stock, would you see a gain in fuel efficency without damaging the engine? (And whatever else out of the above retrofit could be done cheaply).

If you could get a low tech (and cheap, say under $500) option for a retrofit, it might be cost effective where as doing the entire DOD package probably is not (is it worth spending say $3,000 or more, to save a few hundred on gas every year?)

JP
 
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