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Old 06-18-2012, 03:57 PM   #11 (permalink)
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Unofficial first results:
2.76 gallons consumed over 59.3 miles -> 21.5 MPG average
90 degrees F outside/140 degrees intake air temp
A/C on
average speed 64 MPH

Now, some problems I've noted:

Going straight and level produced most of the MPG gains. Compared to my previous throttle, though, MPG suffered more when going up inclines. For instance, there's a stretch of road about a mile long that is about a 2% incline. With the old throttle, I could expect to see an instantaneous MPG reading of about 18 MPG on the overhead display, corrected to about 16 MPG actual. With the wedge in place, I saw 15 MPG on the overhead display, corrected to 13.5 MPG actual.

I will have hard numbers tonight, on my homebound commute.

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Old 06-18-2012, 04:50 PM   #12 (permalink)
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Quote:
Originally Posted by Christ View Post
CV carbs.
CV carbs still use a throttle plate.

Quote:
Originally Posted by Frank Lee View Post
Controllable intake valve throttling.
As was pointed out, that's kind of complicated and expensive. Especially if the vehicle in question never came with this feature from the factory. It's a really nice idea, though.

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Originally Posted by niky View Post
Always wondered if you could do throttle-less more cheaply... like say, using an intake tube that's flexible, and having bladders control tube diameter...
That would be nice. You could reduce turbulence to almost nothing. Not sure how long the materials would last, though.

Quote:
Originally Posted by some_other_dave View Post
The wedge throttle sounds intriguing. The idea could be extended further, so that there is only one gap for air to go through at all times, instead of just at very low throttle openings.
That sounds kind of like a barrel throttle. I understand they're used in performance motocross.

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Originally Posted by some_other_dave View Post
The slide valves used in some race cars would be one way to do that--the throttle plate slides out of the way instead of rotating out of the way. The intent in a race car, of course, was to eliminate the restriction from the open throttle plate, but it would give you only the one opening.
Hm... This was something I also considered

Quote:
Originally Posted by some_other_dave View Post
Perhaps an iris? That would be quite mechanically complex though.
An iris throttle might could work, too. Certainly better than a butterfly valve. But, yah, it'd be a mechanical nightmare.
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Last edited by t vago; 06-18-2012 at 05:12 PM.. Reason: clarification
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Old 06-18-2012, 04:53 PM   #13 (permalink)
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I always liked the idea of getting some energy out of anything that costs you energy. I guess it comes from the old vacuum operated wipers. Not that they were that good but they used some of the energy lost in a throttle restriction.

I think of it as a column of air extending into outer space that is trying to crush everything on the planet. It's astounding how much total pressure is exerted on our skin surface at 14.7 pounds per square inch.

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Old 06-18-2012, 06:50 PM   #14 (permalink)
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I've been giving throttling some thought, and came up with this idea:



The idea is to have a venturi with a convergent and a divergent nozzle. There'd be a teardrop shape that would move into and out of the venturi throat, which would accomplish the necessary throttling. Ideally, there'd be no turbulence at all.
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Old 06-18-2012, 07:15 PM   #15 (permalink)
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No matter what method you use your still going to have throttle losses when creating a vacume. Cylinder deactivation has been around for awhile and has been documented in that reduces fuel consumption at part throttle operation. I think removing the throttle restriction compleatly and injecting fuel on as needed basis for less then full power needs would achieve this. Think of the hit and miss engines of days gone by.
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Old 06-18-2012, 07:46 PM   #16 (permalink)
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I also agree that you are barking up the wrong tree. The drag that is costing energy is created at the piston top. There have been some good ideas bantered like cylinder deactivation, some not mentioned but discussed before like reducing RPM through gearing, introducing inert material to create additional pressure (EGR or water) or running lean.

You can get a similar effect to what you seek by advancing your intake lobe on the cam but this is only good if your CR is not already relatively high (as you are moving the opposite of Atkinson effect). I think a smaller intake plenum would also have a similar effect.

Last edited by Duffman; 06-18-2012 at 07:56 PM..
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Old 06-18-2012, 08:05 PM   #17 (permalink)
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I didn't mean CV, I meant the ones that have a direct action sliding throat valve, like older Honda quads.
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Old 06-18-2012, 08:44 PM   #18 (permalink)
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Quote:
Originally Posted by smokey442 View Post
No matter what method you use your still going to have throttle losses when creating a vacume.
You're describing pumping loss. And, yes, vacuum creation will always be associated with pumping loss.

What I'm trying to describe is this:



Note the circled part, which shows nice, pretty eddy currents right behind the partly opened throttle plate. That happens because a vacuum is being generated, and is in addition to pumping loss. The stuff that I've circled is what I'm trying to minimize.

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Originally Posted by Duffman View Post
There have been some good ideas bantered like cylinder deactivation, some not mentioned but discussed before like reducing RPM through gearing, introducing inert material to create additional pressure (EGR or water) or running lean.
Sure. All of these will reduce pumping loss, and will likely reduce throttling loss as well. However, I am primarily focusing on reducing throttling loss right at the throttle body.

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Originally Posted by Duffman View Post
You can get a similar effect to what you seek by advancing your intake lobe on the cam but this is only good if your CR is not already relatively high (as you are moving the opposite of Atkinson effect).
What would that do for exhaust? I can't advance the intake lobes by themselves. The truck engine is a SOHC design.

Quote:
Originally Posted by Duffman View Post
I think a smaller intake plenum would also have a similar effect.
That's not really possible without spending hundreds (or thousands) of dollars into having a custom, one-off intake manifold fabricated. All sorts of things have to be taken into consideration: airflow into the individual runners, interaction between cylinders, effects of different engine speeds on airflow.... Not something I want to focus on, right now.

Quote:
Originally Posted by Christ View Post
I didn't mean CV, I meant the ones that have a direct action sliding throat valve, like older Honda quads.
Something like this?

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Old 06-18-2012, 09:36 PM   #19 (permalink)
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Quote:
Originally Posted by t vago View Post
You're describing pumping loss. And, yes, vacuum creation will always be associated with pumping loss.

Sure. All of these will reduce pumping loss, and will likely reduce throttling loss as well. However, I am primarily focusing on reducing throttling loss right at the throttle body.
I guess I wasn't clear but I am in the camp that throttle losses are irrelevant for a fuel economy problem. As long as we are dealing with a part throttle condition its not an airflow problem. The engine doesn't feel drag from the pressure drop at the throttle, the engine feels drag from the vacuum at the piston tops. As long as we are in the part throttle region the engine only cares that it sees the % of cylinder filling it needs to meet the torque demands at that steady state condition.

To illustrate my earlier point, imagine that all of the cylinder filling occurs during only one degree of the 180 degrees of the intake stroke. Would you rather have all that filling at the start so the vacuum is near zero (or more likely positive pressure, but lets assume zero vacuum for multiple degrees) at the start and slowly increases for the length or the stroke OR a perfect vacuum for 179 degrees and full filling at the end. There may be minuscule gains fiddling with throttle shapes and port configurations but if you are truly chasing the elimination of this loss the real way to do it is advance the intake lobe on the cam.
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Old 06-18-2012, 09:39 PM   #20 (permalink)
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Quote:
Originally Posted by t vago View Post
What would that do for exhaust? I can't advance the intake lobes by themselves. The truck engine is a SOHC design.
You would have to experiment or gets some advanced engine software, you would have to think the original engineers did a fairly decent job to start with. You could buy a after market cam with a wider lobe separation angle or LDA.

Quote:
Originally Posted by t vago View Post

That's not really possible without spending hundreds (or thousands) of dollars into having a custom, one-off intake manifold fabricated. All sorts of things have to be taken into consideration: airflow into the individual runners, interaction between cylinders, effects of different engine speeds on airflow.... Not something I want to focus on, right now.
You can epoxy the manifold for peanuts but again, you may dump a huge amount of high RPM flow for tiny gains on the low end. Again the original engineers probably have your engine dialed in pretty well already.

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