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Old 08-01-2017, 12:47 PM   #11 (permalink)
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Yes, that will help you gain mpg. Gasoline engines produce their best brake-specific fuel consumption numbers when with WOT and an operating speed at/near the RPM at which the engine makes peak torque.

Another trick you can do is to coast down hills, accelerate hard while going up them. That way, your vehicle gains potential energy efficiently because it is WOT. It is more useful to go WOT while up hill, because you gain potential energy without encountering a large amount of wind drag. You can start at the bottom of the hill at 40mph, floor it until you are going 60mph, and then coast for a mile or so down the other side of the hill without a high peak velocity that would cause much wind drag losses.

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Old 08-01-2017, 02:59 PM   #12 (permalink)
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The most efficient an engine will be is based on its bsfc chart also. For my 1.6L Honda it was 75-80% throttle from 1700-2200. You should look up what your vehicle likes. For it being automatic I'm sure whatever rpm your torque converter fully locks up then add some throttle to match up rpm/g/s fuel consumption to output to get the most efficient rate of speeding up.
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Old 08-07-2017, 11:47 AM   #13 (permalink)
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Another way to reduce pumping losses is by carefully increasing the EGR rate (for engines with external EGR) at part load so that a larger throttle opening can be used for a given torque output. Cooling the EGR with a water-cooled heat exchanger works better because reduces heating of the intake charge (most modern diesels have EGR coolers). This is part of what Toyota did (along with Atkinson Cycle) in order to achieve 40% brake thermal efficiency on the new 2018 2.5L non-HEV version of the Camry, but the basic idea has been well known for years. It also changes combustion phasing, so having access to reflash the ECU to change spark timing is essential. At very light loads, residual can also be increased by changing valve overlap on engines with VVT and can also reduce pumping losses, but it also increases charge temperature. Some versions of VTEC should allow you to do this.
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Old 08-07-2017, 10:33 PM   #14 (permalink)
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Nowadays I'd rather try to work on the valve overlap in an engine fitted with VVT instead of dealing with an external EGR.
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Old 08-21-2017, 03:28 PM   #15 (permalink)
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Quote:
Originally Posted by cRiPpLe_rOoStEr View Post
Nowadays I'd rather try to work on the valve overlap in an engine fitted with VVT instead of dealing with an external EGR.
VVT works well at light load conditions. At higher loads, you need the ability to cool the EGR and there is no way to do that except with an external EGR loop. The Prius has done this for the last 2 generations and it is becoming more common. It is particularly helpful for part-load knock mitigation with boosted engines or engines running Miller Cycle.
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Old 08-24-2017, 08:04 PM   #16 (permalink)
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I have a challenge to you guys for my *serious-idea about reducing pumping losses.

Ok, it's not complicated.

Has anyone added a valve or multiple breather valves to their spark plugs ?

How this would work is that compressed air could escape out of the breather valve of the spark plug when open and not when closed.

It would be cheap to add : three drilled holes ? solenoids ? tiny-valve-stems ?

As well as being non-invasive to the engine.

Comments ?
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Old 08-24-2017, 08:23 PM   #17 (permalink)
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Sounds good in theory.

But adding aome of those piezo valves could give you programmable valves.


Two things i am not sure of with your idea:

First will the holes provide enough flow?
Second, would fuel and air not enter with the compression stroke and potentially burn up your solenoid?
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Old 08-24-2017, 09:33 PM   #18 (permalink)
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Quote:
Originally Posted by teoman View Post
Sounds good in theory.
First will the holes provide enough flow?
Not sure yet. But air compresses easily and I'm thinking how pin-hole size (0.5 - 2mm ?) pressure relief valves could relieve pressure.

I know my cylinders get to 160psi with a compression tester.

If I concentrated I could probably calculate [ie find on google] how much air can flow through 3x 2mm diameter holes at say 1200 rpm.

Quote:
Originally Posted by teoman View Post
Second, would fuel and air not enter with the compression stroke and potentially burn up your solenoid?
I was only thinking of using this as part of cylinder deactivation when no fuel was being combusted. So when fuel was applied to the cylinders, the valves would close.
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Old 08-24-2017, 09:38 PM   #19 (permalink)
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But arent your solenoids outside thr combustion chamber?
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Old 08-24-2017, 10:18 PM   #20 (permalink)
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Quote:
Originally Posted by ar5boosted View Post
I was only thinking of using this as part of cylinder deactivation when no fuel was being combusted. So when fuel was applied to the cylinders, the valves would close.
I'd rather try something all-mechanical (though it could be servo-actuated and fully-integrated to the cylinder deactivation), operating in the opposite principle of a Jake-Brake.

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