Hot Start Issue

[David-aviator]

I have a Titan ECI IOX-360 in my RV7A with ram air induction. I am also running with dual 113 PMags. I am using the jumpers / with the MAP from the mags not coneccted to the MAP sensor. The engine has 100hrs on the hobbs and at ROP the cylinders are running with 1 the coolest, 4 next with 2 and 3 the hottest (365/385/395/400+ @ 8500 msl and 70 OAT @ 10.9 GPH LOP they nearly always break with 4 first then 3 then 2 then 1 (335/355/358/360 @ 8500 msl and 70 OAT) @ 6.8 GPH.

Cold start are flawless. Engine runs smooth all the way through taxi/run up / climb / cruise / landing / taxi to hangar / and shut down.....

Now for the hot start that is another question. (this is the only way I have found that will start the engine and I have nearly ????( there maybe one that I don't know about) tried them all).

1. Mixture full Rich
2. Master on
3. both PMags on
4 "clear prop"
5. turn on high pressure fuel pump
6. hit start

prop will turn maybe 10 times and the engine will begin to show life.

7. Let go the start bottom.
8. The engine will run rough ...but if I shut the fuel pump off to soon the engine will stop.
9. At a point in time about 5 seconds the fuel pump will be turned off.
10. Engine will still run but a bit rough and on a few occassions has back fired.
11. By the time run up is completed / and ready to launch the engine will finally run smooth but not as smooth as from the cold start.

NOW THE QUESTION..... Could this hot start problem be a PMag timing-set up problem? Or................

Frank @ 1L8 ...RV7A... Flying and Tracken MT-RTG

The problem is more likely vaporized fuel in the supply line.

This situation is why the AFP purge valve works so well. I have, after a year of trial and error, gotten the hot start procedure down to where it works 99% of the time - the engine starts on the first or second blade. The 1% where it does not work is when the engine is half cooled down and the pure hot start procedure does not quite work due to fuel starvation.

I won't bore you all with how to do it (it is quite simple) just advising anyone wondering if AFP is the way to go on this issue - it is in my book.

 

[rv9av8tr]

FI Hot start method

I have the Airmotive SilverHawk FI system on my IO-320 RV-9A.
Hot starts are VERY easy!

Mixture Idle cutoff
Throttle wide open
Fuel boost pp on.

Ignition on
Crank it. (should only take 2-3 blades)

As soon as it fires,
Push the mixture IN full rich,
Pull the throttle out to almost idle.
When engine has smoothed out, turn fuel boost pp off.

Works perfectly EVERY time without fail.

 

[B Cunningham]

Hot start with AFP Purge Valve

David,
Do you use the Hot start procedure right out of the AFP manual or some other procedure? I have not had great success with the AFP Hot Start procedure.

 

[David-aviator]

David,
Do you use the Hot start procedure right out of the AFP manual or some other procedure? I have not had great success with the AFP Hot Start procedure.

Sometimes I don't read well. Maybe it is all there in the manual but I had great difficulty in the beginning also. In fact, I was so screwed up I had trouble getting a light off with a cold start, not to speak of the hot start.

This is the procedure that works for me - first hot and then cold start.

I ALWAYS shut down with the purge valve (it kills the engine right now) and mixture ALWAYS stays forward except when leaning - so the flow pattern getting into the airplane is Master ON, Fuel Pump ON, Throttle Wide Open.

Hook up seat belt and shoulder harness slowly while fuel is circulating. (about 45 seconds)

Throttle closed to just above idle, CLEAR PROP, starter START and purge valve forward at the same time. It fires off immediately most of the time. If not, it is because the engine needs a "little" prime depending how much it has cooled down.

The cold start is exactly the same except the purge valve goes in for 5 seconds and back out (engine prime) before starter to START. Just like the hot start, as prop begins to turn with starter, purge valve forward. Two blades max and it is running. (the battery loves it!) When the engine is between a hot start and a cold start, it is a "slightly cooled down" start. I prime it about 2 seconds.

The throttle has to be cracked enough to give about 1200 rpm after light off, if not, the engine may stall-quit almost immediately probably because the AFP controller has not found its brain or there's a slug of air coming through the system. (I have caught a stall-quit by pumping the throttle, don't ask me why this works but it has.) If the initial rpm is 1200-1400, it usually gets through this stage without a stall-quit and is OK.

Once the engine is stable, it will idle nicely at 680 rpm - except after hot start. Depending on how hot it is, rpm may have to be as high 1200 to keep the thing running due to fuel vaporizing in the flow divider. Electric fuel pump on or off doesn't seem to matter. Above 1200, like going for take off power, it purrs like a content cat. Fuel is flowing and won't vaporize in the skinny tubes to the injectors.

For a time I was worried about running the battery down cold or hot start - no more - this works for me. I think the royal screw up in the beginning was FUEL PUMP OFF after circulating fuel or priming. Leave the FUEL PUMP ON until after take off except to check the engine pump OK before take off.

 

[David-aviator]

In all fairness to Don at AFP, I reread the manual regarding operation of the purge valve. It is all there, but what can be confusing for the new operator are comments on operation with and without the purge valve that appear to run into each other.

For the benefit of the new operator, perhaps I can shine a bit of light on operation of the purge valve alone based on personal experience with the system.

In the beginning I was priming with the throttle at idle and sometimes with it set to wide open. Starting was inconsistent and the reason was there is considerably different fuel flow for priming depending where the throttle is located. At idle the flow is about 1 gph, at WOT (or over half way) it is over 4 gph. After that sunk in, I primed at WOT so as to have a consistent base line for the amount of fuel going into the cylinders. In other words, it takes more time to prime at 1 gph than it does at 4 gph. Five seconds at 4 gph works here. Before going to that method, priming at idle sometimes never worked at all. It was most frustrating. I did not know if the engine was starved of fuel or flooded.

Don says move the purge valve knob AFTER the engine starts.

That works, but what works better for me is to move the purge valve knob as the starter is engaged. If one waits for the engine to light off, sometimes fuel starvation occurs because the valve is opened a bit late. It seems, at least here, that opening it immediately before the engine lights off provides an instant shot of more fuel. Cold starts are predictable and instant. The procedure also works well with the hot start, the only difference is the amount of prime. That is a judgement call on how much the engine has cooled down. It does cool down quickly if the oil dip stick door is opened after shut down.

The items that made a difference for me in getting a predictable start are leaving the PUMP ON, priming at WOT, and moving the purge valve to open (fuel to flow divider) while engaging the starter.

That's how I arrived at the flow pattern of MASTER ON, PUMP ON, THROTTLE WO, hook up the straps, etc. It works and is a reliable procedure for an emergency launch in time of war

 

[RV10inOz]

Hot starts on the IO540 with silverhawk;

crack throttle just about 1300RPM position
Mixture OFF
Fuel Pump OFF and do not prime.

Crank the starter as soon as it fires, run the mixture up, then set throttle. Then lean back to agressively lean.

Use fuel pump if need be to clear any surges.

If you over do the priming and other stuff its a bit more stress than you want!

DB

 

[Tom Martin]

This is one of those issues that has to be decided while building the plane as it is not easy to modify the system later. My suggestion is to install a T in fuel system during construction and put a cap on it. Then later, if you have hot start issues you can add the rest of the lines.
I have over 1500 hours, using the AFP system, and others, with not one missed hot start. This is over a span fifteen years in at least 10 different aircraft. Each engine is slightly different but minor tweaking will solve the issue. I really have a problem with installing extra fuel lines, valves and cables, when they may not be required.
Using my suggestion they can be added later if required.

 

[Rockyjs]

I noticed at OSH that the precision new fuel injection lines from the diverter to nozzles are now braided cables. They even had some type of insulation on them for heat. My Superior with Precision fuel injection starts fine hot but is very rough in idle due to vaporizing in the small lines. There is only about 1/2 psi of fuel pressure in these lines at idle. I get some strange looks when I tell the passenger that it will smooth out on takeoff.

I'm contemplating swapping out my lines. Also it's probably a good idea to place a cooling shroud with blast tube on the mechanical fuel pump which was discussed in a previous thread.

 

[wbecker]

Hot start Bendix RSA

I have the Bendix RSA system on my AEIO320, Decathlon.
It will start instantly when hot, (1- maybe 2 blades), up to about 20 minutes after shutdown with this method.
Mixture - cutoff
Throttle cracked
Pump off
Hit the starter and it fires, mixture rich.

Now if it has been over 30 minutes or more, not so easy.

Bill Becker