Running on 4 cylinders
04-20-2006, 03:27 PM
#1
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Running on 4 cylinders I see GM are looking into a system that shuts down half the cylinders whilst cruising to save gas. In theory, I'm not about to do it, would it harm the engine if a switch was installed that cut the power to 4 of the injectors and coil packs?
04-20-2006, 03:33 PM
#2
You would have to remove the pushrods on 4 of the 8 cylinders and kill the fuel injectors to those cylinders. You could still run the spark if you wanted to, but it wouldn't be needed. This is possible with a cam that generates a high vacuum signal (stock cam), but the motor would REALLY be a slug on 4 cylinders if you ran a performance camshaft, LOL. No bottom end torque AT ALL!
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2013 Corvette Grand Sport A6 LME forged 416, Greg Good ported TFS 255 LS3 heads, 222/242 .629"/.604" 121LSA Pat G blower cam, ARH 1 7/8" headers, ESC Novi 1500 Supercharger w/8 rib direct drive conversion, 747rwhp/709rwtq on 93 octane, 801rwhp/735rwtq on race fuel, 10.1 @ 147.25mph 1/4 mile, 174.7mph Half Mile.
2016 Corvette Z51 M7 Magnuson Heartbeat 2300 supercharger, TSP LT headers, Pat G tuned, 667rwhp, 662rwtq, 191mph TX Mile.
2009.5 Pontiac G8 GT 6.0L, A6, AFR 230v2 heads. 506rwhp/442rwtq. 11.413 @ 121.29mph 1/4 mile, 168.7mph TX Mile
2000 Pewter Ram Air Trans Am M6 heads/cam 508 rwhp/445 rwtq SAE, 183.092 TX Mile
2018 Cadillac Escalade 6.2L A10 Pat G tuned.
LS1,LS2,LS3,LS7,LT1 Custom Camshaft Specialist For custom camshaft help press here.
Custom LSX tuning in person or via email press here.
04-20-2006, 03:40 PM
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Why would you have to remove the pushrods? We've all turned our engines over without any fuel in them, or would the high revs damage the engine due to the lack of resistance from the exhaust gases?
Just a theoretical question, although with gas being $1.70 a litre this side of the pond, it's worth thinking about economy.
Just a theoretical question, although with gas being $1.70 a litre this side of the pond, it's worth thinking about economy.
04-20-2006, 04:17 PM
#4
You want to have the valves closed, otherwise, you're spending lots of energy on a compression stroke that makes no power. With the valves closed, the piston compresses the trapped air like a big coil spring. This is why displacement on demand closes the valves.
04-21-2006, 01:35 PM
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My understanding of GM's displacement on demand is that GM has put provisons in the LS2 blocks to allow passages for oil to the lifters. The lifters fill with oil and expand allowing the valves to function. When running on 4 the lifters collapse which causes the valves to remain closed. It is all controlled by valves which direct flow into the lifters.
Is this how it works?
Is this how it works?
