IO-520 High egt's on cold day

[Tom3holer]

I flew my newly acquired 185 yesterday when the temp was 22deg and noticed something that concerned me.
At TO full power had the fuel flow just slightly shy of the red line. When throttling back to 21"/2300 as I was landing shortly at another airport I noticed my egt's had gone from low 1400's to 1475 even at 19-20". I know. it was in some part due to the 22deg wx but hadn't noticed that before.
Is it normal to have to tweak the injection system during the cold months?

Tom

 

[skywagon8a]

Tom, You are worrying too much about those numbers. You only need to be concerned if you can not get any rise when you are leaning. The numbers mean nothing.

 

[Dave Calkins]

Not sure if you mentioned it before Tom, but having the fuel flows checked with a calibrated gauge per Continental specs on any injected engine new to me is important. Have seen too many that were WAY off.

 

[DENNY]

MTV has some great input on the issue not sure if it was here or backcountry.
DENNY

 

[Tom3holer]

The colder temps have indeed caused a very noticable rise in EGT temps as I throttle back. Will check it relation to peak next good weather day I get.
I have not had the pressures checked as my mech does not have a set of calibrated gauges. I have checked the newly installed JPI 450 FF against burn when refueling and it seems to be right on and also agrees with the installed Cessna FF gauge. Need to find a good shop that knows how to set up these injection systems nearby.
Will ck BCP for his postings.
Tom
Cape Cod

 

[OLDCROWE]

That's odd. Are you sure you were FULL RICH in the short (?) climb with cowl flaps OPEN? WHAT RPM initially and in the climb?

My climb routeen (with 88" Mac) is 10 half turns out at run up (gets me about 2525) with full throttle to 5K then lean to 21gpm the. At 7K lean again to 20gpm and if I stop short I pulll RPM back to 2400 and mp to below RPM

 

[Tom3holer]

The egt's normally rise a bit as you throttle back from wot but as I mentioned with the colder air it was much more noticeable
I took off at 2850/wot and came back to 25/2550 then somewhere around 21/2300 as the destination was only 8 miles away.
This was all at full rich and the cowl flaps were full open.
There is quite a bit of discussion on the benefits of climbing at wot and 2700, max continuous, and keeping the egt the same with mixture throughout the climb which I am going to try next time.

 

[GordonC195]

Tom, The TCM fuel injection relies on engine driven fuel pump pressures to dictate min & max fuel flows. When the air is heavy and dense there may not be enough metered fuel pressure to keep the EGT in limits. TCM's SID97 explains these adjustments. For a quick fix, it sounds like a 1/4 turn CW on the max adjust should give you enough. This recessed screw is on the side of the pump just beside the oil filter. The one looking aft in the low press.
G

 

[OLDCROWE]

Yes I can see EGT's rise some initially when I pull the throttle back and high like you say but only if I pull it back fast I don't pull the prop back as well so I'm not accelerating much like when doing pattern work.

I think the flow comments are spot on, in a WOT climb I don't get fuel flow down into the green (Cessna gauge) untill 7000' when I put it there with the mixture and I'm only seeing mid 1100's to low 1200's max in the climb and I see mid 1300's in cruise.

If I set a climb at the top of the green with flow and RPM and pull the power back or climb too slow I have seen hot temps develop pretty quick so I don't do that, reguardless of what some schools teach.

Unless a condition demands different I only use a full prop setting when I want to run Eaton of of his rocking chair...he lives just SE of the airport :lol:

 

[skywagon8a]

..and keeping the egt the same with mixture throughout the climb which I am going to try next time.

..to keep the EGT in limits. TCM's SID97 explains these adjustments.

There is no such thing as EGT limits in this airplane/engine. If there were it would be published and/or placarded. There is a placard on the panel installed by Cessna which gives fuel flow limits during maximum continuous climb. EGT is NOT in the discussion. The only exhaust temperature which has limits is the TIT (turbine inlet temperature). This airplane doesn't have a turbo installed.

Call Pete Conner at PLY http://www.yankeeaviation.com/index.html He can likely help you with the pressure adjustments.

 

[GordonC195]

You are correct, there is no published EGT limit for recips. My statement is this, If we are climbing out at climb power and the EGT is near peak and the CHT is warm, hot or increasing, then for me. I am not within limits of reasonable operation. The defense for this is more fuel flow or more climb speed. As I hear Tom's problem, the Wf is leaner at part power than at WOT.
Yes, Pete gives good phone, Lol

G

 

[aktango58]

Wide open throttle runs a higher fuel flow to assist cooling. That is the reason that the operator's manual says use WIDE OPEN THROTTLE for take off and initial climb.

As you bring the throttle back the fuel flow comes down faster than needed to prevent lean mixture, the extra fuel reduced was only needed for cooling.

The cold air increases the density of oxygen molecules digested by the plane, which simply acts to LEAN out the mixture. Sort of like being used to flying at Denver one flight and Seattle the next.

A leaner mixture will cause EGT's to rise. The amount leaner is the question. As said above- how much does the EGT rise when you lean it out? If you are getting less than 100 degree rises on the egt when leaning, you might want to have the fuel flow increased, as you are probably causing your CHT's to run above what you want.

The damage might not show up in one or two flights from running it a bit lean. When it does show up, bad things can happen.

I don't know how cold you are operating, but engines up here are set for well below zero usually. Check out the amount of rise in EGT on climb power when you lean, that should tell you lots.

Also, for WoT: have the fuel flow set to read MAX on the gauge... extra fuel will save you lots of $ in engine repairs, (seen the results myself)

 

[Dave Calkins]

Cessna 185 and 206 instrument panel-mounted "fuel flow" gauges (actually a pressure-sensing instrument, NOT a "flow" instrument) are notoriously inaccurate.

Please do a fuel flow check with a calibrated gauge per Continental's specifications.

 

[Tom3holer]

Flew the other day with temps around 40 and did notice the EGTs were 20-30 deg lower when throttling back.

My mechanic and I have put together a new 4" 0-15 psi liquid filled Wikai gauge and associated plumbing to set the unmetered pressure correctly so as to set the idle, with digital tach, and the mixture.
A question popped up: There is no mention, I have seen, in TCM SID 97-3E about the need to bleed the fuel pressure line to the test gauge. I did find an article that mentioned it should be done. It seems, however, on a steady, not pulsating, pressure the either way should read the same. The article also mentioned having the gauge at the same height as the pump which I believe would not be needed if the line was not bled.
Would appreciate any thoughts on this.

Got the time the other day to do a ck on EGT peaks and FF. Done at 23/2300 6500'

1 1462/13.2
2 1453/13.0
3 1515/12.9
4 1510/12.6
5 1461/12.0
6 1464/12.0

I will do them again next week on a 2 hour flight and also get a final ck on FF accuracy and adjust the "K" factor if necessary.

T

 

[OLDCROWE]

From a bunch of other pump testing and calibrating I've been around the procedure is to fully bleed the gauge line (a valve on a tee just ahead of the gauge is real handy along with a discharge tube...). The. For the test keeping the gauge at the same level as the pump Works to minimize the effect of the air you didn't get out and any differential created by potential differing levels with a known gauge height.

 

[skywagon8a]

What is the difference between the full rich EGT and peak EGT on each cylinder at a constant power setting?

With a difference of 1.2 gph at peak between the cylinders, you ought to investigate balanced fuel nozzles to bring the fuel flows closer together.

 

[Gordon Misch]

If you bleed the line and have the gauge at a known height above or below the pump you'll know the gravitational head at the gauge as compared to the pump, and can compensate. Roughly 0.31 psi / ft of elevation.

 

[Tom3holer]

I stand corrected after reading the latest SID 97-3G does talk about bleeding the remote gauge lines.
The 1.2 GPH difference is normal for the TCM injectors of my engines era, 2009. They are called "Tuned" but are all the same orifice size so are really not tuned at all. Have been in touch with GAMI ans will be placing an order very soon.
I did not note the full rich readings during the test but will next week when the WX gets better.

I did do an inflight induction leak test. The procedure I used at 6500' was measuring EGTs at full rich at both WOT and 10" less ie 24"-14"
The difference on each cyl was noted and ranged from 68-91.
1 68
2 89
3 61
4 70
5 91
6 86

 

[aktango58]

I did do an inflight induction leak test. The procedure I used at 6500' was measuring EGTs at full rich at both WOT and 10" less ie 24"-14"
The difference on each cyl was noted and ranged from 68-91.
1 68
2 89
3 61
4 70
5 91
6 86

I don't know that this is an induction test, but if you are saying that you leaned the engine at 6500' and got less than 100 degree rise in EGT, you "might need to increase your fuel flow".

Turn up the volume.

 

[Tom3holer]

The way it is supposed to work is that you set up at cruise at an altitude that will allow WOT then record the egt's. Then derease it by 10" thus creating a vacuun in the induction system and record the EGTs.
The change between egts in each respective jug should be somewhat the same. If one is unusually less than the others it could/is and indication of an induction leak as I understand it.