Bruce Fenstermacher wrote:Looking at your cowl, you have a cowl bottom appropriate for a '48 through '49. The lip you have left the factory at 3". When I say 3" I mean as measured along the flap skin from the bottom of the main cowl body ti the edge of the lip. You called this the long side and measured it at 1.5". This is half what it should be.
Gahorn wrote:Anecdotally, I've heard the size of the lip is not of much import except on seaplanes (for which the increased lip size is often called a "seaplane" lip.)
And why do you think a seaplane might require a larger lip? Could it be because it is swinging a larger prop, running at higher power settings and traveling slower through the air thus less cooling air through the engine? Maybe Cessna found out their new 3/4" lip after '51 was a problem causing oil temps to high n seaplanes. Did you know there is no seaplane lip for the '48 to '49. do you know there is no seaplane lip for a '48 and '49 or cowls prior to 19200?
As we know and I'm sure George will agree, in 95° temps, oil temps in 170s tend to run above 200, many close if not at 225°. What I have paid close attention to over the last 15 years is that none of them are '48 to '49 airframes with the correct 3" cowl. I've NEVER run across a single one. What is typical the temps I see in my '49. I have a 2.5" lip. Most months of the year my oil temps barely make it higher that 170°. Even in the winter, even with winter baffles. On the hottest days here in PA we may see 190°. My first 170 had a '52 cowl with the 3/4" lip. Guess what? Oil temps near 225° in the summer. Same operator flying in the same temperatures, using the same flying techniques, same prop, same RPMs, maintaining the same engine and baffling to the same standard. One difference. The lip.
When I call my evidence anecdotal, I'm leaving just a bit of room. Fact is I've studied it, I've taken note of who has hot running engines and their cowling, I've owned and operated both cowl lip sizes. But what I haven't done is cut my large lip down to see if the oil temps increase and when I was chasing high oil temps with the 3/4" lip, I didn't realize the effect the lip has.
I also notice your lip seems to have holes across the bottom. They would make excellent holes for screws to hold an extension which could be installed or removed as necessary and see what effect it has. Just maybe we will get George to listen to my anecdotal evidence or maybe you will shoot a hole in mine.
And last, a little contest to see how close attention to detail others pay to 170s. How do I know looking at the picture of the dpowells cowl, that it is a '48 or '49 cowl?
I'm not interested in entering into a contest, and I was not referring to your comments Bruce, when I made the post about "anecdotally". I was referring to reading various materials over many years of studying the high oil temp issues of 170's.
I'm sure your question was rhetorical when you asked "And why do you think a seaplane might require a larger lip?..." ...as I'm sure you know that I know.
But to address the issue of the "lip" one has only to look at the 170 IPC to understand there was only ONE "lip" for the 170/ragwing, PN 0552000-41 and it was the so-called 3" lip.
ALL SUBSEQUENT models of 170s used the same lip, PN 0552001-41. However, floatplanes used a BOLT-ON extension of that lip, PN 0552001-60, which was the so-called "seaplane" lip.
The holes in dpowells lip may be intended for the bolt-on extension (despite the fact that his airplane is not a seaplane, although he needs a few more of them.... it calls for 14 screws/nuts. And his tailpipes are reversed.)
The anecdotes to which I've referred have boiled down to:
1. The seaplane lip was developed because of the long taxi periods many seaplanes experience that may result in high engine CYLINDER temps. Oil temp control was not the purpose of the lip.
2. The seaplane lip had little additional effect during flight. It was only at water-taxi speeds that it was particularly useful.
3. The various lips found in the fleet which differ from the IPC's are likely experiments conducted by owners seeking to affect engine/oil temps, and are in most cases not consistent with approved installations, and rarely help high oil temperature issues.
Bruce, despite your personal experience, in my opinion the comparison you make with the two different lips versus oil temps are actually not a valid comparison if you consider the fact that it was actually TWO DIFFERENT airplanes you have compared... Am I correct in that assumption?
Also, it would be expected by most operators that the cool winter months experienced in PA would also provide cooler, 190-degree-range oil temps. Again, it's not a valid comparison to the rest of the fleet or even to a different airplane in the same locale.
Most high oil temp issues are caused by:
1. Poor condition/incorrect PN's/missing engine baffling.
2. Leaking exhaust riser clamps (blowing hot exhaust onto pushrod-tubes which are the oil-return path to sump from the rocker box.)
3. Inaccurate or improperly-ranged gauges.
4. Operator abuse (high AOA, slow IAS, long climbs, abusive training techniques.)
It is my experience that most 170B models in good condition, using 100W oil, 100-degree Texas wx, oil temps indicate 210 regularly in cruise and slightly higher in long climbs at 80 mph IAS. Continental was particularly loathe to use external oil coolers or lines because of other engine mfr's issues with those items. These C145/O300 engines are not harmed by running at oil temps in the lower 200s range, and with SAE 50 wt oil are fine to 240-F.
Do not use comparisons to other models and engine installations. Swift owners (updraft cooling...which is especially effective at cooling pushrod tubes) are particularly bothered by LOW oil temps and water-condensate in their sumps. We don't have that problem.
(Intake air scoop)