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Old 01-24-2010, 12:15 PM   #11 (permalink)
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...not many people remember Lindburg's "war time" contribution to "long distance" flying in the Pacific.

...as an ex-aircrewman (4 x R-3350's with turbo-compund) I studied and read about his contribution.

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Old 01-25-2010, 06:28 PM   #12 (permalink)
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Quote:
Originally Posted by Old Tele man View Post
...not many people remember Lindburg's "war time" contribution to "long distance" flying in the Pacific.

...as an ex-aircrewman (4 x R-3350's with turbo-compund) I studied and read about his contribution.
A lot of solid 'engine fundamentals' research comes from aircraft engines. So I'd probably have read about it regardless. But the reason that example came to mind is probably the most memorable entry in my own log books. It is only .7 hours PIC, but the type reads "P-38J"!

What made it even more memorable was I was flanked by 3 P-51Ds. It must have been quite a site from the ground. Eco friendly? Not a bit, we were guzzling leaded fuel like crazy. But I can't quite bring myself to regret it!

-jjf
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Old 01-25-2010, 06:38 PM   #13 (permalink)
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...all my hours are in USN/Lockheed EC-121's over a 7-8 year period.

...about 100 gallons of 115/145 AVGas per engine per hour (once airborne)
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Old 01-26-2010, 08:10 AM   #14 (permalink)
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Quote:
Originally Posted by jfitzpat View Post
Likewise, you aren't going to burn anything up without heat, and CHT plummets lean of peak. The problems with running this lean are a) it is hard to keep the fuel distribution even to the cyls with such small amounts, so you can get rough engine operation and b) your emissions soar.
This is an interesting statement. I come from the performance world, and especially in turbo motors, "going lean" is a recipe for disaster. Is it only under high load and RPM conditions that going lean is a problem, but in light loading situations when economy is the target, it's not as much of an issue?
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Old 01-26-2010, 05:49 PM   #15 (permalink)
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Originally Posted by tpwalsh View Post
This is an interesting statement. I come from the performance world, and especially in turbo motors, "going lean" is a recipe for disaster. Is it only under high load and RPM conditions that going lean is a problem, but in light loading situations when economy is the target, it's not as much of an issue?
Actually, this was the confusion that I was trying to explain. "Going lean" in relationship to what?

For economy reasons, you would generally want to be leaner than a stock street car runs normally. They run typically at stoich (peak EGT), not for economy, but for emissions.

Best economy is leaner. There is a myth that leaner than EGT burns up engines, this is unquestionably false (this is what I'm referring to in the original post). The problem is that emissions would go up and cat efficiency would plummet.

In PERFORMANCE, we aren't running closed loop at stoich (peak EGT). When you stomp on the gas, the ECU on even a street car will go open loop and add fuel.

Stock tunes are too rich for peak performance. They pour on fuel to avoid heat and detonation. So, for max performance, you need to lean out the stock tune. The danger is when you (or more specifically, any cyl) get leaner than best power, but still richer than stoich. This is when all the ingredients for detonation, heat, fuel, and pressure, are at their highest.

This has led some performance folks to believe that you 'can't be too rich', but this is not true either. The basis of the myth is that they think the extra fuel is acting as a coolant. But this makes no sense in the physical world as we understand it. If you look at the *amounts* of fuel we are talking about, and the latent heats involved, this sort of 'cooling' by going rich would be like tinkling on a raging forest fire.

The reason that going rich helps with cooling is that it changes the speed of the reaction. That is, the flame front actually travels more slowly through the mix. This moves the point of peak pressure, helping less energy be transferred to the cyl heads as heat, and more put out the exhaust as heat. In the normal triangle, this leaves work (basically the energy goes into useful work, heat out the exhaust, or heat in the cyl heads). As we move from peak EGT and get richer, we initially get more work. Somewhere around 125-150 degrees rich of peak is typically best power.

This is because we are looking for the best combination of thermal release, exhaust gasses, and mechanical advantage pushing down.

But, as we continue to get rich, we start to lose power, for no real benefit in heat or detonation avoidance. Much the way a stock tune errors too rich for best performance to begin with! So, for performance reasons, you can be too rich.

My other point was that from an eco point of view, it is too rich as well. Ideally, we want to run as tightly to stoich as we can, as much as we can. This is primarily from our driving habits. But, when we can't - say, hilly terrain, we want the engine to use the excess fuel as efficiently as possible. In other words, performance folks want rich operation power efficient for max speed, etc. Eco folks want rich operation power efficient for *least demand of it*, it is better to be able to ease off the pedal and keep going up the hill than keep it down.

I hope that is clearer.
-jjf

Last edited by jfitzpat; 01-26-2010 at 05:51 PM.. Reason: Typos
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Old 01-26-2010, 09:08 PM   #16 (permalink)
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Quote:
Originally Posted by Old Tele man View Post
...not many people remember Lindburg's "war time" contribution to "long distance" flying in the Pacific.

...as an ex-aircrewman (4 x R-3350's with turbo-compund) I studied and read about his contribution.
Wow. R-3350s. I haven't heard anyone mention those since I went through A&P school. Wright Cyclones with PRTs, yes?
Quote:
Originally Posted by jfitzpat View Post
A lot of solid 'engine fundamentals' research comes from aircraft engines. So I'd probably have read about it regardless. But the reason that example came to mind is probably the most memorable entry in my own log books. It is only .7 hours PIC, but the type reads "P-38J"!

What made it even more memorable was I was flanked by 3 P-51Ds. It must have been quite a site from the ground. Eco friendly? Not a bit, we were guzzling leaded fuel like crazy. But I can't quite bring myself to regret it!

-jjf
PIC on a P-38J?! I am envious! My all-time favorite though is the F-4U Corsair...R-2800 Double Wasp, 18 jugs, lots o' power! Vought F4U Corsair - USA
Sorry for the hijack!
I have been told I would not see much in the way of MPG improvement unless I leaned my engine to about 16:1, but it would likely run rougher. Do you really think a wide-band is a good investment? Thanks.

Quote:
Originally Posted by jfitzpat View Post
Stock tunes are too rich for peak performance. They pour on fuel to avoid heat and detonation. So, for max performance, you need to lean out the stock tune. The danger is when you (or more specifically, any cyl) get leaner than best power, but still richer than stoich. This is when all the ingredients for detonation, heat, fuel, and pressure, are at their highest.
I had heard stock tunes were too rich. I know my Dodge truck's factory tune is. I am running a Superchips on the 87 tow tune right now. I don't know if I am getting better mileage, but it does run a lot better.

Last edited by ECONORAM; 01-26-2010 at 09:35 PM.. Reason: add question
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Old 01-26-2010, 09:15 PM   #17 (permalink)
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Quote:
Originally Posted by ECONORAM View Post
Wow. R-3350s. I haven't heard anyone mention those since I went through A&P school. Wright Cyclones with PRTs, yes?
...yup, 3 x Power Recovery Turbine (PRT) on each engine:

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Old 01-26-2010, 09:50 PM   #18 (permalink)
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Quote:
Originally Posted by ECONORAM View Post
I have been told I would not see much in the way of MPG improvement unless I leaned my engine to about 16:1, but it would likely run rougher. Do you really think a wide-band is a good investment? Thanks.
For a gasoline engine, that is generally way too lean. Best economy is probably closer to 1.05 lambda, say 15.4:1. Again, the problem with running here is the your emissions will go up and your cat rendered useless.

If you only cared about saving gas, not emissions, you could fool many ECU's into running here using a programmable analog output on a wideband controller. But, again, I think that a more productive use of this technique is to get the ECU to track stoich closer. You don't save much fuel, but your emissions go down.

Then if you want to save fuel, run *open loop* operations more efficiently. These are the cases where most vehicles go open loop and pour on the fuel to error on the side of no detonation. They have to do this because their instrumentation is limited. But a growing number of replacement ECU's will operate wideband closed loop - if the wideband is fast enough and accurate enough.

This started appearing in the performance markets first, since it is about getting closer to best power without blowing up for them. But two of the projects I've worked on recently were along the same lines, one used wideband instrumentation to cut emissions on some giant LPG driven engines at a power plant, the other was using a faster form of wideband measurement to lower fuel use in a new generation of ECUs.

If you are interested in combustion engines, I'd say that wideband can be one of the most important measurements you can make. But it really needs to be the right wideband. A lot of them are pretty much useless when tested against calibrated gas. But I am VERY biased in this area, so be forewarned!

Still, as I showed in another thread (from the only car at my house NOT wired with at least 1 wideband), you can learn a lot about how fuel is being used just be reviewing the data from a stock ECU.

-jjf
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Old 01-26-2010, 09:53 PM   #19 (permalink)
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Quote:
Originally Posted by jfitzpat View Post
...you can learn a lot about how fuel is being used just be reviewing the data from a stock ECU.

-jjf
...how about enlightening us by telling us what "magic" boxes & software you used that enabled you to "get" that data from ECU so that it could be reviewed?
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Old 01-26-2010, 11:34 PM   #20 (permalink)
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I was guessing my SUperchips might do the trick. It does allow data logging, but I have not tried that yet. Maybe on my trip to Wendover this weekend....

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