Fuel flow

Post by **GAHorn** » Wed Aug 28, 2013 10:11 pm

Well, the CHT you're experiencing is 100 degrees BELOW the maximum for this engine, so I personally would not worry about it, and enjoy the clean plugs and low fuel burn.

kidalways · Post by **kidalways** » Mon Sep 30, 2013 5:46 pm

I have read all the posts again and again on this issue and weighed all the pros and cons. Here is what I have done to band-aid the situation. If you read the last few posts on the "Fuel Flow" subject you will see that I never experienced this problem with a Hot #2 CHT until I exchanged carburetors. The following are my troubleshooting steps prior to calling the carb the culprit- first off I removed all cylinders and inspected the valves for hot spots or evidence of a true overheating - found nothing. While cylinders were off cleaned and inpected intake and exhaust ports/replaced all gaskets/seals. I wanted to make sure my problem was not a leaking gasket/seal issue. I then flew the airplane again - performing the same climb out of 750 FPM at full power - my fuel flow was reading 11.2 GPH - seemed a little lean to me. As usual once leveled out - #2 cylinder cooled to a reasonable temp. Time for a decision - came home - dropped the cowl and removed the carb. I sent the carb to Marvel Schebler with the instruction to richen the carb. After they had recieved the carburetor I recieved a phone call from a tech - we went over everything I have done and had been seeing in flight. We agreed that the carb should be richened - they completed the work and performed a flow check - setting the carb to between 12-12.5 GPH. I have re-installed the carb and found some improvement - my #2 cylinder now runs around 400 deg instead of the 450-460 that i had seen earlier during climb out. I can't say I am completely happy but - it is better than it was. I do believe it is a fuel distribution problem more than anything - let's face it #2 is the longest intake run. And though I love my JPI analyzer - sometimes more information can make you paranoid. So - this was my solution..........

blueldr · Post by **blueldr** » Mon Sep 30, 2013 6:06 pm

It is really a shame that you guys are too young to have been flight engineers on the B-29s back in about 1944 or 1945. You could have had a field day every tine you flew on one of the bastards trying to figure what in hell the engine temperatures were doing.

krines · Post by **krines** » Mon Sep 30, 2013 9:08 pm

My mechanic says those EGT/CHT probes are a mechanics dream. They usually result in all kinds of unnecessary work. I know from personal experience.

Post by **GAHorn** » Mon Sep 30, 2013 11:03 pm

Much A-do (and $) about nothing....IMO

WSHIII · Post by **WSHIII** » Thu Oct 03, 2013 12:26 am

Well, the truth is, multi-point engine monitors will actually pay for themsleves over time, saving you money in the long run. They do that by catching little problems before they become bigger, more expensive, ones. When is the last time you put something in your airplane that actually paid for itself and enhanced your safety?

Ignorance truly is bliss.

blueldr · Post by **blueldr** » Thu Oct 03, 2013 4:22 am

The narural fuel and mixture distribution in a C-145/O-300 is apparently pretty iffy at best. It may be nice to know how screwed up it is, but relatively sophisticated instrumention will not do anything to correct it. After all, they're not asking much from 300 cubic inches.

bagarre · Post by **bagarre** » Thu Oct 03, 2013 12:27 pm

I thought about one of those gadgets when I first got 81D.
It can tell you how much fuel you burn....after 200 hours, I just budget 8.8GPH all the time.
It would have a much more accurate tach....I fail to see the value.
It could tell me if all my cylinders weren't the same temperature....oh wait, that's normal
It could tell me if one cylinder is much hotter than the rest...yeah, that's normal too.
It could tell me that a cylinder is completely cold...hmm I think I'd feel that in the RPMs
It could tell me that a cylinder is so hot it's gonna slag right off the block...yeah right.

It could tell me that something is going terribly wrong and the motor is going to self destruct without any other indication and otherwise impossible to determine by oil pressure, oil temperature, static run up, odd vibration, spark plug problems or even cutting the filter open and THIS will save me thousands and thousands of dollars!!!

It's got a Check Airplane light on it?

How in the world did theses little motors ever last 70 years without computers?

johneeb · Post by **johneeb** » Thu Oct 03, 2013 1:31 pm

head_in_the_sand-461x307.jpg

KS170A · Post by **KS170A** » Thu Oct 03, 2013 4:51 pm

johneeb wrote:
head_in_the_sand-461x307.jpg

I thought this was about 170 instrumentation...not Washington politics??

Post by **GAHorn** » Thu Oct 03, 2013 6:23 pm

It's like having nuclear plant instrumentation on a steam engine.
Save the investment for fuel or spark plugs or mx...... admit that it's really just for entertainment and get your head out of the cockpit, (or sand, whichever is applicable.)

DaveF · Post by **DaveF** » Thu Oct 03, 2013 8:35 pm

WSHIII wrote:Well, the truth is, multi-point engine monitors will actually pay for themsleves over time, saving you money in the long run. They do that by catching little problems before they become bigger, more expensive, ones. When is the last time you put something in your airplane that actually paid for itself and enhanced your safety?

Ignorance truly is bliss.

My JPI EDM-700 is less than a year old and it has already paid for itself. It warned me that one CHT was hitting 465 on takeoff in my newly-overhauled engine. Because I had that information I was able to quickly discover a poorly-overhauled magneto before the cylinder died an early death. It helped me determine that the problem was the mag, not just a single plug or wire, not a baffle problem, that the other magneto was good, and that my carburetor supplies proper fuel flow. It also helped me troubleshoot an excessive fuel pressure indication problem. So, yeah, I'm very happy to have the engine monitor.

I also like knowing that the engine is giving normal indications before I fly over mountains or at night or leaving my home area on a XC.

I agree the monitor detracts from the simplicity of the 170. I've resisted several "upgrades" to my airplane for that reason. More stuff is more stuff to break. I don't like the mess of wires around the engine, and someday I'll hate having a probe go bad, but to me it's worthwhile.

twlareau · Post by **twlareau** » Fri Oct 04, 2013 4:06 am

Dave, glade you found your problem! I know t was frustrating as hell for awhile. Lets go Fly!!

Post by **GAHorn** » Fri Oct 04, 2013 4:39 pm

Dave, I'm not challenging your personal experience, but for an educational discussion, how did a bad magneto overhaul affect just one cylinder, yet not manifest itself during an ordinary runup which could be detected using original instrumentation?
What fuel pressure problem did it detect, exactly?

N2625U · Post by **N2625U** » Fri Oct 04, 2013 8:48 pm

gahorn wrote:Dave, I'm not challenging your personal experience, but for an educational discussion, how did a bad magneto overhaul affect just one cylinder, yet not manifest itself during an ordinary runup which could be detected using original instrumentation?
What fuel pressure problem did it detect, exactly?

Yesss, inquiring minds wanna know...

The International Cessna^® 170 Association

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