What gauges/monitor for LOP operation
 

I’m buying a 1975 337 that still has all the original engine instruments. It has a Garmin 430 with WAAS and we’re putting in a Garmin GTX345 transponder for ADS-B in and out. My question is what do those of you that utilize LOP use for your temperature readings? The JPI monitors are really nice, but do I need all of that? I’d like to get something worthwhile, but without breaking the bank or having the plane at the avionics shop for a month. Is there a reasonable gauge with good CHT & EGT readouts or is it best to spend the $$$ and get two EDM 830’s.

Thanks,

Tripp

https://www.jpinstruments.com/shop/edm-760/

Probably the least expense. If you buy at Sun N Fun or Oshkosh they offer a nice rebate. This will do fuel flow also and could be added later to spread out the love

I really like mine but I know there are other units out there that are good too. A lot of info for the buck with the Insight G4 too

http://www.insightavionics.com/bestg4t.htm

I have seen the G4 and it has a lot of different info in one package.

I installed my own EDM760 so cost was minimal. Not a huge project but time consuming running all the wires to the rear engine. Make sure they know it's a Skymaster when you order

Thanks Herb, Your insight is always helpful.

We plan on going to Sun n Fun, so it sounds like it's best to hold off until then before making any decisions. The Insight G4 seems to be a little small and condensed, but I like that they have one specifically for the 337. I tend to think that 2 EDM 830's would be easier to read and is about the same price as the G4. I'll talk to both vendors and continue to get advice until then.

Glad to hear that you did the install yourself. I have a good buddy that is an IA and is a small partner in my 337, so hopefully that means we could also do the install and save some money.

Tripp I have the Insight G4 and it provides a tremendous amount of information in a small package for a reasonable price. So far I've had to replace one EGT probe and that's it. One of the nice things about Insight is that they ship with Skymaster specific harnesses. https://www.aircraftspruce.com/pages...sight-twin.php

Having said, if I had to do it again I would go for the JPI EDM960: https://www.aircraftspruce.com/catal.../jpiedm960.php

In addition to that, I would go with the CIES fuel senders: https://ciescorp.net/applications/sm...rcraft/cessna/

If you do JPI + CIES...it means that EVERY SINGLE old gauge goes right in the garbage can and you have accurate, digital monitoring of every engine parameter and the fuel quantity.

Yeah, it's a lot of money but I've spent lots of $$$ in labor this year chasing old wiring.

John,

Thank you for the reply. All of that information is very helpful. I love the JPI EDM 960, but the price is way more than I want to spend at this time. The G4 seems to do a lot and I like that it has the harness specifically for the 337, but it is a little small for what I'm looking for.

Do you have any knowledge about the JPI EDM 830? It looks as though 2 of those would be really nice. They are good size and show a lot of info and 2 of them are about half the price of the 960 and about the same as the G4.

The info on the CIES fuel senders is also great to know. I have one fuel tank gauge that is intermittent and need to fix it.

Thanks again,

Tripp

JPI make great quality products. A pair of 830's would be great.

Can't stress this highly enough...get the CIES senders and the appropriate gauge.

Senders: https://ciescorp.net/applications/sm...rcraft/cessna/

Gauge: http://www.aerospacelogic.com/index....product_id=249

If you think the senders and gauges are expensive, here's an inkling of how much $$$ can be spent chasing old fuel gauges: https://www.aea.net/AvionicsNews/ANA...stemsJan03.pdf

Tripp,
Do you have enough room in the panel for the dual EDM 830's? I found with my panel the G4 was the best option given the panel space...On the co-pilot side, I do not have much room with the clock, vacuum, original engine cluster and a storm scope. Also, I wanted to have the gauge closer to me to be able to see the accuracy. I removed my ADF indicator, and putting the G4 on the pilot's side. I have a '66.

I am not familiar with the EDM 830's - they sure look nice but I find the additional large view of RPM and MAP redundant given the large original gauges in the aircraft. It really depends on what you are looking for in an engine gauge. I chose the G4 due its smaller size, capability and easy to use LOP function. I wanted something to accurately give me CHT, EGT and Fuel Flow data in order to run the engines safely and efficiently. Those 3 are the most important for that, while RPM and MP are required, they are less critical when it comes to monitoring what is happening during the combustion process.

Jeff

I was thinking of putting the 830’s where the current MAP gauge is and my current FF gauge is. I’d probably move the FF to where the EGT gauge is and just not have the current EGT, MAP & RPM gauges and just use the 830 for that info.

Hi Tripp,
You have had some nice panel work done and certainly have some additional real estate in the panel. I think you better review the STC for the 830’s. Near as I can tell, it is only approved to replace your EGT and CHT - you still have to maintain your original MAP, RPM FF, oil temp etc... This is why the cost is so low - if you want to replace all those you would have to with the 960.

In your case though, you would still have room to install the 830’s side by side where the EGT gauge is and to the right. Nice looking panel!

Jeff

GAMI Injectors FIRST
 

I’ve recently read Engines, by Mike Busch, who speaks a lot about LOP operations in his book. I need to read it again to absorb more.

He is very high on the instruments to be able to monitor, and especially diagnose our engines.

But, from what I picked up, GAMI injectors, to ensure that cylinder fuel deliveries are pretty close, is probably a necessity or prerequisite to use LOP techniques. Otherwise, as you lean out the engine, the lower fuel flow cylinders will start coughing before the higher flow cylinders can get lean. He states the Continentals from the factory have pretty unbalanced flows. About 0.5 gpm difference in cylinder flow rates would cause an imbalance enough to preclude LOP because of engine roughness in the ‘starved’ cylinder(s).

I’m new to my T337G, a P model, and have just downloaded my JPI EDM 760 data for the first time while the machine is in annual/paint. It was obvious that my Rear Engine CHT #1 was bad by looking at the data. I was pleased to see no CHT’s near 400F, except from the bad probe which even went negative at times!

I downloaded Engines based on a recommendation from this forum. It was great advice and I encourage the same by anyone not already an engine ‘expert’.

Russ
N8CV