Higher EGT #4, misses

gfb · #1 07-02-2018, 06:05 PM

First start, saw some stumbles and general roughness. Noticed high EGT on #4 suggesting possible clogged injector. Removed, cleaned, ran again. Here is the savvy link to the run:
https://www.savvyanalysis.com/flight...6-38eddccc324e

Any ideas what might be going on? It's no longer rough but definitely still missing every few seconds.

gfb · #2 07-03-2018, 08:14 PM

So here is the latest. We believe I'm having an induction leak but have been unable to track it down so far. I replaced the intake manifold gasket on cylinder #4 (which is having the problem) and no luck, same issue. Here is the engine data showing what is going on:

https://www.savvyanalysis.com/flight...d-162a998888ef

03:30 - L mag only
04:00 - Both
04:17 - R mag only
04:47 - Both
05:02 - Leaning out
05:34 - Full rich
05:46 - Throttle idle
06:19 - Mixture to cut-off slowly

Cylinder #2 EGT is actually #4 EGT, we swapped them to confirm it wasn't an issue with the probe.

The problem is bad enough that #4 is misfiring constantly under 1000 rpm and there is lots of vibration. Once I get up to power and the delta-P is reduced, then it makes the expected power.

Any ideas? Titan has asked me to do a compression check on all cylinders and to see if I'm having an exhaust valve leak on #4.

Titan support (Bobby) has been very helpful and attentive but I'm a bit worried about being done in time for the inspection.

Any thoughts appreciated,
-Guil

gfb · #3 07-03-2018, 08:15 PM

As a side, Don from AFP has asked me to do a flow test on all 4 injectors at once. I'll be doing that on Wednesday morning and honestly I'm hoping that's it as it sounds like an easy solution.

BillL · #4 07-04-2018, 01:32 PM

My engine (Vans new IO360M1B) was screwy like this. At full throttle it smoothed out and took off. Don't know if it is the same issue, but it ran ratty on the ground and had wild changes in EGT.CHT like yours. It was running way too lean on the idle circuit. It would not increase when at idle when mixture was slowly pulled, would idle terribly, like a leaking gasket and some hesitation with throttle on. I left the cowl off and kept increasing the idle mixture wheel until it increased in RPM on mix leaning.

May not be your issue, but that data characteristic sure looks familiar.

Something easy to check.

skylor · #5 07-05-2018, 11:29 AM

Have you checked for a fouled plug?

Bubblehead · #6 07-05-2018, 12:27 PM

An induction leak would show up as EGTs going up as MAP goes down (throttle going closed). Added MAP to the SAVVY chart and MAP is going up as everything else goes down. Is MAP data reversed or something?

When MAP is low, like at idle or low RPM, the higher atmospheric pressure leaks into a cylinder making it go lean. I don't see any indication of that in the graph but then again I am not sure why MAP is backwards. I checked RPM and it goes down when MAP goes up.

lr172 · #7 07-08-2018, 11:45 AM

Quote:

Originally Posted by BillL

My engine (Vans new IO360M1B) was screwy like this. At full throttle it smoothed out and took off. Don't know if it is the same issue, but it ran ratty on the ground and had wild changes in EGT.CHT like yours. It was running way too lean on the idle circuit. It would not increase when at idle when mixture was slowly pulled, would idle terribly, like a leaking gasket and some hesitation with throttle on. I left the cowl off and kept increasing the idle mixture wheel until it increased in RPM on mix leaning.

May not be your issue, but that data characteristic sure looks familiar.

Something easy to check.

+1
If you haven't adjusted the idle mixture yet on a new engine, I would absolutely start there. It seems unlikely that these are set anywhere near optimum at the factory and the guys running them on the test stand will only adjust it enough to get it to not die. If the problem only exists below about 1000-1200 RPM, that is a good indicator that the idle mixture is off.

EDIT: I looked at your charts. In your case, the problem seems very specific to #4. An Idle mixture issue would not show such tight groupings on 1-3 and a major divergence on #4. I would be looking for debris in the spider. At idle RPMs, the spider is closing off an orifice to reduce flow (this is it's primary purpose). At higher RPMs, the orifice is opened and flow is controlled purely by the pressure dictated by the Servo. Therefore, a problem that only appears at idle and off idle transition points to a problem with that orifice/restriction. I would pull the top of the spider off and look closely at the V shaped restrictor for the #4 line. Being new, it may have some machining debris or a burr from manufacture. The orifice is quite small at idle and it doesn't take much to reduce flow.

Larry

gfb · #8 07-08-2018, 08:07 PM

Sorry for taking so long to get back on this thread. Here is some more data:

- We have adjusted idle mixture (50 rpm rise) and idle (750 rpm) and it is rock solid with the cowl off. No stumbles, just purrs away no matter what we throw at it.

- We cleaned out the spider/flow divider per AFP instructions and now EGT/CHT are rock solid for all cylinders. There is very little divergence between the 4, with maybe 50-70 deg egt delta.

- As soon as the cowl is on i start getting misses/surging. I talked to Don @ AFP and he thinks I am not getting enough airflow over the engine while the cowl is on at idle and I'm getting fuel boiling in the stainless spider lines. I am trying .023" nozzles to see if that helps.

Any pointers on increasing airflow at idle? I will be instrumenting the top cowl area with an RTD to see what temperatures are in there. Don indicates that if it's much higher than 130 I definitely have fuel boiling in the lines.

gfb · #9 07-09-2018, 10:47 PM

Well, turns out I already have the smaller nozzles.

Any pointers on how I can increase airflow over the top of the engine at idle? Someone mentioned I could cut back the lower cowl opening at a 45deg angle to increase the opening area. Thoughts?

Another idea I will follow up on after Phase 1 is to reduce some of the fuel lines and move the red cube to the top of the engine, hopefully into colder air. It's been suggested that maybe it would help to reduce overall fuel heat in the pre-flow divider fuel lines.

EXflyer · #10 07-10-2018, 07:39 AM

Would it be possible to put the stuff we use on car AC on the line to insulate it? Not saying go flying with it but its made for high temp use under car hoods for ac line insulation. One can probably get it from an outfit which works on auto AC its kind of a black tar looking item that comes in rolls.
Another item, is the cowl contacting an item such as one of the plug wires? Might look for a print from it on the cowl. Just some thoughts from an old mechanic. Good luck.