Engine Instruments Delima

[Charles Schefer]

[Mark Anderson]

A JPI 960 would be nice. Very accurate fuel gauges.

[N3322G]

Charles,

In 2005 when we did the engine O/Hs, we put in a 760 to protect and diagnose problems with the engines - it has paid for itself more than once. We also put in the optional oil temp feature - of course, leaving the original gauges as they were. So I'm comfortable we have accurate oil temp readings through the JPI - took two iterations of install of the probes.

The original gauges read a touch higher in cruise than yours but not much. Interestingly, the left also reads a needles-width lower than the right - has as long as I can recall.

Not sure this is the answer you want to hear.

We have found a fine line between wanting everything perfect and everything safe. I used to overhaul most stuff - now I have a tendency to buy new if available as a couple of O/H's have only lasted a couple of years and then we have to either do it again or buy new. I dislike downtime for maintenance although I really enjoy the personal relationships with the maintenance personnel and their families. So my approach may be different than what works for others. At 63, I may only have another few years to readily fly. Perhaps more but I feel my flight clock ticking

This leads me to praise Al Powers as my idol - he O/H'd both of his engines at age 83 IIRC and still flies often from a 2300' strip.

[Charles Schefer]

Mark / Pat - Thanks for the replies.

Mark - yes I agree a 960 would be very sweet indeed but I'm not ready to take that leap. I think my wife would shoot me if I spent $20K+ after install on a 960. That said I do want some sort of engine analyzer and to Pat's point - I can well imagine it will pay for itself during it's life.

Pat - thanks. I don't yet have your ownership experience so I probably haven't yet wised up The folks at Air Parts claim they can make them accurate to within 2%. I'd be happy to have my gauges within a dot width and I have heard (or rather read) Zach's comments about using them as a "relative reference". At any rate, like you I don't want down time and after a lot of research yesterday I came to the conclusion yesterday that - yes I could get Aerospace Logic or EI replacements for individual gauges and even though the direct gauge cost was not all that much more the installation, wiring, panel surgery etc... would end up costing more. In addition to the thoughts above I know myself well enough to know that I would not be content with some old gauges and some new. I quickly realized that what I really want is going to cost $6K or more when all said and done and if I am going to do that I'd rather have an integrated monitor where the data can be downloaded (as cool as the Aerospace Logic gauges are individually).

So... this morning I shipped my Oil Temp and Pressure gauges to Air Parts and they should have them tomorrow. Hopefully I'll get them back next week (or soon and get them reinstalled. I actually like those old AC gauges. I am going to try to get them as accurate as possible (again Air Parts says "within 2%") I guess I will see.... The bottom line is I don't currently have a JPI (or similar) and I cant' justify flying around with a gauge reading 60F for oil temp the whole time. So I haven't wised up in the sense that I am in pursuit of "new" old gauges. As soon as I can I plan to add something like a JPI and while the 960 is awesome, I would be quite happy with a 760. I suspect that JPI will soon have something new in the twin -secondary market to replace the 760. Insight has their new G4 Twin coming out and it looks awesome. There is currently a big gap in JPI's line between the 760 and the 960. They need something that is similar to an 830 on the single engine side but for a twin, but not so far as the 960 that costs 20K and is primary... something that will still fit in an 3.125" hole. I will wait a bit and see. An Aspen Pro PFD is also on my list of wants.

By the way Pat - I very much enjoyed the Comanche Care article in the latest Flyer.

- Charles

PS - If anyone has a set of factory CHT gauges they are looking to get rid of please let me know, I'm interested.

[Charles Schefer]

My overhauled and calibrated oil temps, oil pressures, and fuel flow gauge all come back from Air Parts tomorrow. Once they are reinstalled and tested I will post the results.

- Charles

[Charles Schefer]

The new oil pressure and temp gauges went in and now appear to be much more accurate! However, they also appear to show what we can also see with an externally connected and calibrated oil pressure gauge. The oil pressure on both engines is running high. The proper range is 25psi minimum at idle, range for normal operations is 60-90psi and up to 100psi is allowed for start-up. In actuality my oil pressures are running more like 105 - 107psi at start and then after warm up at 2000 - 2500 static RPM oil pressure is more like 95psi.

I spoke to Lycoming and they said that years ago the type cert on MOST IO-320s was modified to make the start up pressure up to 115psi and normal ops up to 95psi. However the IO-320-B1A remains at 60-90psi and 100psi max at start up. They said they think it was just an oversight that the B1A was not similarly modified in the type cert but nevertheless 60-90 is the correct range. So my IA and I are following the book procedure to adjust pressures down to the proper range.

- Charles

[Charles Schefer]

To bring this thread to a close, here is a new pic of my engine instruments after:

- Oil Temperature gauges overhauled and calibrated to new Rochester oil blubs under STC from Air Parts of Lockhaven
- Oil Pressure gauges overhauled and calibrated by Air Parts of Lockhaven

Using an freshly-calibrated external mechanics pressure gauge (0-200psi scale) we measured actual oil pressures on each engine and in discussion with Lycoming adjusted the regulators on each engine so everything is in spec. We now see 80psi oil pressure in cruise and all other book settings in range.

So here's a pic of the gauges in cruise now. Oil pressure is perfect. Oil temps are close to perfect as well though it appears left oil temp just runs a little hotter than the right, I'm not sure why. All the baffling is like new and seems tight. The CHT gauges both read around 300F. This was at 8,500MSL on a close to standard day. 22"MP and 2400RPM. OAT was about -3C.

Gauges after calibration and engine oil pressure regulator adjustment

- Charles

[N3322G]

Nice - can't get much more centered in the green - happy engines, happy gauges, happy pilot.

[MULEFLY]

Charles... I have a JPI installed so my data is digital... regarding higher oil temps. My baffles are pretty tight... but the left oil temp was always 10 to 20F hotter than the right one. I read a lot and decided to replace it... they can get clogged over time and lose some of their capacity to cool the oil. New oil cooler installed and they are now within a couple of degrees.

All the best!
Jim

[Charles Schefer]

Thanks Pat - yes I am much happier.

Thanks Jim - interesting point. My engines and all accessories were overhauled 500hrs ago by a reputable facility. That said I am not sure the oil coolers were part of that I'll research. If you can point me in the direction of any specific reading you recommend (or I can just search the forums and google) I'd appreciate it. I'm envious of your JPI. I plan to put one in as soon as possible. I'm actually eying the Insight G4 Twin that is soon to be released... but for now the stock gauges have to do and I just wanted them accurate.

When you replaced - did you replace both oil coolers to "re-baseline" them or just the one that was high? I'd sure like mine to be identical...

- Charles

[N3322G]

Charles,

Oil coolers are considered engine accessories and may not have been changed when the engine was O/H. Charlie Melot of Zephyr Engines recommended that we replace them at O/H as the cost for O/H didn't make much sense when for just a bit more, you could have new. Our JPI oil temps are within a couple of degrees of one another with the new oil coolers.

[Charles Schefer]

Pat - thanks. Based on what you and Jim both posted it sounds like replacing oil cooler may be in my near future. Any idea (roughly) what it costs to buy a new oil cooler? Does not look like it would be too much labor to change since it's just sitting on the top of the engine. Of course I am relying on the factory gauges but Air Parts says they should be accurate to within 2% which is factory spec and they calibrated them side by side because that's how the would be installed. New oil bulbs and new O/Hed gauges plus we ohmed out the wires from the bulb to the gauge to make sure the wires were all good and they were. So... the gauges should be reasonably accurate.

Also - I assume these engines have a vernatherm just like any other recip? Maybe the vernatherm on the left is just not opening as much (or closing completely forget which way around it is) and so some oil is bypassing the cooler...

- Charles

[N3322G]

Vernatherms are normally replaced at O/H but you might check. IIRC in 2005 oil coolers were $300 ea ... but I've slept since then.

[Charles Schefer]

Thanks Pat, I'll check.

- Charles

[MULEFLY]

@ Charles...

I only replaced the "hot" side... and they are now within a couple of degrees. I purchased a new cooler from Pacific Oil Cooler... including freight $248.12. My original intent was to replace the hot side... return it to POC for overhaul and then install it on the other side... when I did my flight tests... they were so close that I haven't bothered to send it back for overhaul.

Jim