Hottest running cylinder?

Greetings,
I'm putting a freshly overhauled O-360(180 hp) in my -7A but due to budgetary constraints I can't quite swing a full bore EIS yet so I'm going with Van's single EGT and CHT instruments. Is anyone aware of a particular cylinder traditionally running hotter than the remaining three? If it matters the engine is an -A4M from an Archer. Thanx for any help

--hawk

The number is

Cylinder Three for CHT, (right rear)

Airflow under cowl and baffles affects the CHT, therefore #3. I would suggest you consider during flight test you try to move the CHT probe to other cylinders. The CHT is position dependant and I am 98% sure #3 will be your most critical or hottest CHT. However EGT (mixture) affects CHT. The 2nd hottest cylinder is often #2. Cylinder #1 is almost always over cooled and that is why you see large plates on the front of the #1 cylinders. This is why during flight test 4 channels is good in tuning your baffles. How much does a Lycoming cost? I would get all 4 channels (cylinders) instrumented.

For EGT, a good guess is go with #2 or #3 for EGT but no guarantee. The hottest EGT (leanest) can be any cylinder and varies with throttle wide open or partial. If it was me I would go to #2, since some claim that is the leanest at WOT at altitude (below 75% power). If you want to lean with partial throttle, #3 would be my second choice (from what I hear on carb engines). Also cyl #3 is an eaiser EGT installation. However be warned, some say #3 or #4 is always the leanest? Again no guarantee. Again during flight test you could move the EGT probe, but you will have extra holes in those pipes. How much would 3 more EGT probes and a switch cost? Every engine is different and no cylinder is sure to have the highest EGT all the time. (Note buy the PROBES that will work with your future engine monitor if that is the plan).

Plenty of planes have flown with NO CHT or EGT at all. It is not a required gauge. CHT is the most important and you can feel pretty good about #3 being the hottest CHT. Leaning using a single EGT gauge can be done, but you should to do some flight test to figure out how to figure your leanest cylinder if you want to use the gauge for actually leaning. Cylinders #2 and #3 seem to be the front runner for leanest cylinders. Going with #3 for both CHT and EGT might make sense.

EGT is a bit of a guess since it is a function of mixture distribution. You have a carb. Any cylinder could be the leanest. Since an EGT gauge is not necessary to lean the engine (by Lycoming), a single EGT gauge is a just a warm fuzzy, unless you absolutely know that you instrumented the leanest cylinder. Lycoming calls for you to lean (only when at or below 75% power) just to roughness and enrichen for smooth operation. THAT IS IT, NO GAUGE. You can use your EGT gage to watch the EGT raise. Watch to see if it peaks and drops before the engine gets rough. Enrichen just to get smooth operations and note the change in EGT on your gage.

With a single EGT on the cylinder you know is on the leanest, Lycoming says lean to peak and enrichen 100F. A single EGT is better than nothing, but not knowing it is on the leanest cylinder, it can only be used as a suggestion to manual leaning (roughness method). With the cost of gas a 4 channel EGT might save you some money with reduced fuel burn. G

Agree with George that #3 is generally the hottest.

However, consider the poor mans multi-channel CHT (or EGT.) For about $150, you could have 3 more sensors and a 4 position rotary switch to display all 4 cylinders (one at a time, of course.)

Jeff Point
RV-6
Milwaukee

And we all know eveything Lycoming says is true right? Save your beans and get a EDM 700.

Thanx for the replies

The EDM-700 is a JPI product, right? Fits in a 2-1/4" hole? Maybe I'll be able to spring for it after I sell my C172 to free up the hanger for the RV.

--hawk

Jpi 700

Hawkeye7A said:

The EDM-700 is a JPI product, right? Fits in a 2-1/4" hole? Maybe I'll be able to spring for it after I sell my C172 to free up the hanger for the RV.

--hawk

Click to expand...

Yes......and it is about 1200. well worth the price! for the peace of mind!
Bob Martin
RV-6....with JPI 700

Helping You Spend Your Money

I've have a JPI-700 in a 172, and put a EI UBG-16 into the RV-7. After 2000 hours flying behind one, I feel naked and ignorant without a GEM on board. Don't waste your money on a single probe instrument, and the rotary switch thing requires a steel trap memory to compare one indication with another. The JPI unit also displays volts, oil and outside air temp by adding probes, so can save the money that otherwise would be spent on separate gauges. The EI can also, but you have to add a pricey interface module for volts.

I'd sure scrimp elsewhere to be able to install a GEM from the get-go. They will teach more more about running YOUR engine than anything else aboard, particularly in the important matter of avoiding high CHTs.

#3 was the hottest on my -7 until I installed a new #2 which remains the hottest by only a very few degrees F. Archives I once searched all pointed to #3 as likely hottest CHT.

John Siebold

Well if you are going to engine monitor

Go with A Grand Rapids Tech (GRT) EIS-4000.

For less than $900 you get: http://www.grtavionics.com/model_4000&6000.htm

Spruce has it for $843:
http://www.aircraftspruce.com/catalog/inpages/eis8.php
http://www.aircraftspruce.com/pdf/catalog/Cat06392.pdf

It is by far the best bargain on the market, been around a long time, GRT is known for great support, has 4XEGT/CHT with lean set point pages, shock cooling alert and will warn you if any parrameter limit is exceeded (Hi or Lo).

The basic system comes with All 4 EGT's & CHT's, Tach, Oil Pressure, Oil Temp and Volts. Plus it has flight and total engine hour timers.

With this basic unit you can add these popular options with the purchase of the probe sensor:

Manifold pressure
Fuel levels L&R
Fuel Pressure
Fuel Flow
Carb T
Amps

All the possible standard and optional functioins are :
Standard:
4 or 6 Exhaust Gas Temperatures
4 or 6 Cylinder Head Temperatures
Tachometer
Oil Temperature
Oil Pressure
Volts
Hour meter
Flight Timer with Interval Timer (switch tanks)

Other inputs (with dedicated channels):
Outside Air Temperature
Carburetor Temperature
Vertical speed (VSI)
AirSpeed (AS)

6 Auxiliary Inputs user configurable can provide:
Manifold Pressure (normally aspirated or turbo)
Fuel Pressure
Fuel Level (using capacitive or float-type sending units)
Coolant Pressure
Amp meter
Ignition Advance, second voltmeter, rotor rpm, etc.


For less than $900 you can start with the basic instrument. If you subtract the all the other gauges that you will not need (OP, OT, Fuel Levels, Tach, Manifold, Hobbs meter, Volt, amp) you will save money. If you already bought gauges? Sell them on eBay. You cut holes in the panel already? Well cut them out and put in sub panels or buy a new panel. Even if you got a few optional senders (MAP, Fuel Pressure) it will be about $1,000. IF you have fuel tank senders you don't need gauges, because the EIS-4000 will monitor it for you and warn you of low level! IF you go all EIS-4000 you will save money of seperate gauges and save panel space.

G

But the GRT's interface looks terrible compared to the slightly more expensive ($300 more) JPI. And the JPI fit's in a standard 2 1/4 hole, vs. the propritary hole you'll need for the GRT.

osxuser said:

But the GRT's interface looks terrible compared to the slightly more expensive ($300 more) JPI. And the JPI fit's in a standard 2 1/4 hole, vs. the propritary hole you'll need for the GRT.

Click to expand...

Maybe, but GRT never tried to put Matt Dralle (Matronics, the original RV-List) out of business. Many old timers won't touch JPI to this day.

On a serious note, since I'm the one who suggested the rotary switch setup- that is only if you are really on a budget. I agree with the others who recommend the EIS4000. True the display is not so pretty, but it is very functional and easy to get used to. You could buy three of them for the next lowest price graphic engine monitor. I love mine, and so do hundreds if not thousands of others.

Jeff Point
RV-6 w/ EIS4000
Milwaukee

Information overload!

Thanx to everyone who took the time to respond. I still have the blank panel that came with the kit, but I bought a pre-punched one because it only cost about 4 hours of take-home pay, way less than the amount of time I would've spent laying out and cutting my own. But now y'all have got me rethinking my entire panel layout. I even already installed the optional map box on the pre-punched panel so there's no room for the EIS 4000, unless I take "g's" suggestion and cut out sub-panels. So much to consider. If a quick build meets the 51% rule then the slow-build must meet the 91% rule!! Thanx again.

--hawk

JPI sucks

osxuser said:

But the GRT's interface looks terrible compared to the slightly more expensive ($300 more) JPI. And the JPI fit's in a standard 2 1/4 hole, vs. the proprietary hole you'll need for the GRT.

Click to expand...

Well beauty is in the eye of the beholder.

When I fly, I look at my: 3-dimensional color wrap-around full field of vision moving map, including full topography, collision avoidance, situational awareness enhancer with depth perception.

IT IS CALLED THE WINDSCREEN/CANOPY.

I don't care how pretty or what colors are displayed on an EIS. You don't have to look at it, since it warns of any exceedance, flashing a master warning light and switching the display to the critical page. Also there are EGT/CHT bar graph display pages with lean point set, first to peak, hottest EGT/CHT and cylinder #, delta peak and rate of change data and monitoring. Not to mention it can monitor every system in the aircraft except the pilot?s bladder, for less then the price of a JPI.

Granted the EIS is monochrome, does not have analog emulation and the data tags are hidden, on the users custom pages (unless you push the display button), but who cares, I look at it only to set RPM and MAP and it is fine. As long as the red light is not flashing I am good.

JPI may be nice, but I also remember what a-h's they where to matronics. I would never buy their product. Please don?t get me started on the ?proprietary hole?. If you can?t cut a rectangular hole in aluminum you are in trouble. G

PS: as far as cost a EIS-4000: $850, a JPI EDM-700 starts at $1,250 and goes to $1850. JPI is for Cessnas and Pipers, and if you are talking about the JPI scanner: http://www.jpinstruments.com/scanner.html for $996, I would say that is awful, it has just one number displayed, EIS has all data displayed in a bar graph http://hometown.aol.com/enginfosys/ (picture showing high EGT and CHT on top row and RPM, MAP and FF on bottom. Bar graph shows EGT bars and CHT missing segment. #2 is high EGT, #4 is high CHT. This is one of many custom pages. On my other custom pages I have RPM, MAP, OP, OT, FP, FF and Fuel Totalizer. Another page I have AMP/VOLT, Tank L & R and fuel endurance in Hr:Mn. On my third custom page I have the bar graph (CHT/EGT), Hottest EGT/CHT temp and cylinder number, Peak EGT temp of first to peak, change from peak and fuel flow. Pushing DISPLAY button brings up lables if you forget.There are about a Doz other standard pages with lables. Any page can be hidden from the menu.

JPI sucks???

George,

Your subject line says "JPI sucks". And that's because...........you have experience with them.....or what? You don't say anything negative about them in the body of your message.

Tobin

Oh yeah, BTW, I have a JPI EDM 700 that I've been flying with for 250hrs and I love it. When my plane was painted, I got the plane back with the EDM-700 face plate ruined. Sent it back to JPI and they replaced it/recalibrated it for FREE.

I will never buy any JPI product ever

tobinbasford said:

George, Your subject line says "JPI sucks". And that's because...........

Click to expand...

This is not proper language for the forum and apologize. Their product my be great but the company is a lawsuit crazy bunch of bullies. They bullied Matt at Matronics in 1999 over the word "scanner" vs. "fuelscan" (one word). JPI has done this before with other companies. JPI launched a lawsuit weak on facts and made it real ugly and threatened additional suits. The names and products where different and did different things. If you want to read about it: http://tinyurl.com/9tqjj , http://tinyurl.com/bexdw

JPI's "Scanner" at time of law suite http://www.jpinstruments.com/scanner.html (nothing to do with fuel)

I will not buy JPI products. G

PS: Matt changed his product name to fuelchec: http://www.matronics.com/fuelchec/index.htm
By the way there are 2,000 registered trademarks with the word "scan", "scanner" and "scanning"
JPI got there "FUEL SCAN" tso/stc over a year later mid/late 2000: http://www.jpinstruments.com/fuel_scan.html
I am surprise they don't sue again over the word "FUEL".

And on it goes....

Amazing the amount of dialog one question can generate! Aren't forums neat?

--hawk