Cadstat

Cadstat

Well Known Member
My IO-320 doesn't like the heat. It coughs pretty bad on a long 'after flight' taxi back to the hanger. It's about 95F on the ground. Is there anything to be done? I've heard insulation on the spider doesn't help because after a trip through the mechanical pump you have already heated the fuel. Don't like it but I have to run a little higher RPM and heat up the brakes. It's more pronounced in this plane than others I have owned. Any Ideas?
 
John, can you give us more info on your fuel system configuration. Seems like a fuel heating issue to me. There's a ton of radiant heat under the cowl and with the sudden loss of airflow, it's gonna get much hotter under there. This combined with the sudden slowdown in fuel flow at idle, the fuel is going to pick up more heat.

Which fuel injection system is installed?

Are all FWF fuel lines insulated other than the injector lines after the spider?

Is there a cooling shroud on the mechanical fuel pump and cold air supply to it?

Is there a gascolator installed and if so where? If on the firewall, does it have a cooling shroud and cold air supply?

Bevan
 
Great Questions

Great questions and I don't have an answer for most. I'll bet is was an issue for the last owner. I have seen some insulation of lines and the gascolator on the firewall had a shield added at a later date other than initial assembly. I'll investigate next time I have the cowl off. Thanks for your insight.
 
Gascolator is not needed with fuel injection and is just another place for heat to be picked up. Removing it may help but probably not a total fix either. Getting rid of the mechanical fuel pump and going duel electric with well insulated lines firewall forward is probably best way to fix, assuming it was really important to you and you were willing to put up with the shock and outrage from others upon finding out you removed the mechanical pump. Or, you can just live with it, like many do.

erich
 
John,
I noticed your at high altitude and high tems.The density altitude must be way up there.
Have you tried leaning more aggressively?
 
Leaning

Last night I tried running richer when it started to cough on the taxi back to the hanger. It seemed to help but outside air temps were closer to 80 than to 90. It's not an issue on the way out to run up and I do lean to the max on the taxi to the runway and it's just fine..
 
Do you have a purge return line from the spider back to a tank? Not sure if you can open the purge to run fuel through the system while the engine is running, but it would be a good way to pump more cool fuel through the system and eliminate hot start problems if you have them.
 
IO 320 Injector Nozzles

If you have Bendix or Precision fuel injection installing .022 injector nozzles will help with the hot operation. If you have Airflow Performance .022 is standard size for nozzles on a 320.

Don
 
Cadstat said:
...It's more pronounced in this plane than others I have owned. Any Ideas?
Click to expand...

Have you ever owned any other injected airplane? Especially one as tightly cowled as an RV?

It's certainly not unusual for injected RVs to run rough on the ground in hot weather after landing. The question I would ask you is *how rough* is it running? If you could record a video/audio of the rough running that would help.
 
Yep...

The dreaded post-landing taxi stumble returned last week after flying back from KUAO.

First time since last summer, and it was the worst ever; I thought it was going to stall on the runway there for a moment... OAT was 104F, at 4500 MSL. I don't think my plane has ever seen that high of a combo while taxiing. In my experience DA effects cooling quite a bit. Not supposed to get this hot in Bozeman Montana!

I'm pretty sure that I had some similar (and much milder) stumbling in-flight (only) once over Arizona, it was crazy hot, 98 F at 11,500 MSL.

I actually prefer all other seasons over summer for flying.

By the way, I have an idea on how to solve this problem. Install a cockpit-controlled air vent on the top of the cowl or plenum, depending on your construction. Open upon landing.

I don't think that it is worth the complication, I can live with the surging and stumbling. For now. I prefer to fly when it is cool.


Hans
 
Erich talked about insulated lines. Are your fuel lines insulated to include the lines from the spider? I do not recall seeing any insulated lines from the spider so do not know if that is an accepted and safe practice.
 
This works best for me -

Boost pump on, lean agressively for smoothest operation - I beleive that it is not so much a matter of running rich, it is about getting fuel (un-vaporized) into the system - therefore boost pump on - and then best mixture just like always.

I think many have a tendency to go full rich when they hear stumbles. That just aggravates this problem.

IO-360 with Don's wonderful injector and nozzles, Sam James plenum, no insulation; all with some (but tolerable) hot stumbles.

Good luck
 
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Good idea

Good Idea Jamie,

I had a C210 with a 285 hp 6 cylinder 520 Cont. for may years. It was a little harder to hot start than this plane.

It idols rough enough that I think its going to quit but I rev it up before I wait to see if it really will quit. I'll do a little more testing this week end.
 
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