Author Topic: Evolution 36 C/L enigma (Read 4961 times)

Matt Piatkowski · « **on:** June 07, 2015, 02:48:08 PM »

Hello,
EVO 36 C/L in one of my planes acts strangely.

The launch RPM are 9200-9300 in 2-4-2 mode ( engine "cannot decide" if to run in 2 or 4 cycle ).

The model takes off, starts flying level and the RPM drop almost immediately but for a while only. After another split second, the RPM go up and then down and so on.

There seems to be some connection with the wind direction - RPM drop against the wind and increase down the wind.

After such "RPM cycling" , happening in the first 2-3 laps, the RPM stabilize and the model flies well.

I suspected some dirt in the fuel lines, fuel filter or/and tank.

Checked everything and found nothing.

There is no loose solder in the tank, tubing is intact and I could not find anything suspicious.

Any ideas what is going on?

Perhaps venturi ???

Thanks.
Matt

Brad LaPointe · « **Reply #1 on:** June 07, 2015, 03:56:10 PM »

Matt , try fuel with no castor ,5- 10 percent nitro . They need a few runs to break in , much better mileage with more time .

Brad

Matt Piatkowski · « **Reply #2 on:** June 08, 2015, 07:44:54 AM »

Hi Brad,
I will do that next weekend.

The engine has about 1/2 h. of bench runs and about 25 flights.
Total run time more 2 hours.

Do you feel it has not been broken yet?

Regards,
Matt

Brad LaPointe · « **Reply #3 on:** June 08, 2015, 04:20:27 PM »

Matt , try the 100% syn. for a couple of flights and see if it helps . It should be good after that much running . Around here we have found a wet 2 stroke works well .Don't over prop them and they run very consistently .

Brad

Joe Yau · « **Reply #4 on:** June 08, 2015, 05:05:24 PM »

Quote from: Matt Piatkowski on June 07, 2015, 02:48:08 PM

Hello,
EVO 36 C/L in one of my planes acts strangely.

The launch RPM are 9200-9300 in 2-4-2 mode ( engine "cannot decide" if to run in 2 or 4 cycle ).

The model takes off, starts flying level and the RPM drop almost immediately but for a while only. After another split second, the RPM go up and then down and so on.

Just to isolate the cause.. are you running uniflow venting (faced forward)? or muffler pressure. with the uniflow, its quite common that the run will go richer when it is going into the wind and leaner out.

Steve Helmick · « **Reply #5 on:** June 08, 2015, 06:57:08 PM »

Muffler pressure would also be my suggestion, along with an 11x4.5 Thunder Tiger Cyclone prop. I'd guess a launch rpm of about 9.5k> would be a place to start. Forget the 4-2-4 run as a goal. A rich 2 cycle is the way to go with most modern engines. John Thompson is running one on a Profile Cardinal, and it seems to work pretty well for him. He's running an APC prop, tho...11-4 I think.

Steve

RknRusty · « **Reply #6 on:** June 08, 2015, 07:59:15 PM »

It's always a good idea to pressure check the tank, even new ones. Especially new ones. The slightest leak will play games with the pressure head and sometimes is sensitive to the fuel level.
Rusty

Matt Piatkowski · « **Reply #7 on:** June 10, 2015, 10:05:58 AM »

Tank is NOT uniflow - it is standard with the overflow tube connected to the muffler pressure.
Please see the attachment.
Tank has been checked underwater with pressure gradually increased by syringe connected to the fill tube and other tubes securely plugged. No bubbles.
All silicone fuel lines and fuel filter are regularly inspected for dirt and cuts or/and breaks.

No cuts found and no dirt found while flying last weekend

The plane is my own creation called "Parrot". 48" wings span, flaps, profile fuselage, weight RTF without 4.5 fl.oz of fuel =1080 grams ( 38 oz. )

Propeller: APC 10.5 x 4 scimitar style, grey, cut from 11x4.

Launch RPM last weekend: around 9300.

Comment: Evo 36 spec. gives the RPM range 9300 - 17000. Perhaps 9300 RPM was simply to low to maintain the stable run?

Fuel used: Omega pink, 10% nitro, initially 17-18% total oil ( exact proportion of castor and synthetic unknown ) with SIG castor added by me to bring the total oil content to 20-21%.

I will try Omega 10% nitro without additional castor. I cannot try pure synthetic oil fuel as I do not have it.
I will try 10.5x4 and 11x3 APC prop @ 9500 and ,say, 9800-10000 RPM respectively and watch the overhead lines tension and lap times
I will try the smallest stock Evo 36 venturi ( 0.225" main air flow ID). 0.235" ID used last weekend.
I will try original Evo 36 glow plug ( the last weekend flights were on Thunderbolt 4 stroke that is shorter than Evo 36 plug).
I will try to add 0.04 head shim to decrease the compression.

I will try not to spend my night at the circle this coming weekend as all this looks like 20+ flights to cover all combinations.
Cheers,
Matt

Steve Helmick · « **Reply #8 on:** June 10, 2015, 12:31:37 PM »

Change the tank to uniflow and apply muffler pressure to uniflow vent. That will fix a lot of the problems. Is the engine thoroughly run-in?

Steve

Balsa Butcher · « **Reply #9 on:** June 10, 2015, 02:40:17 PM »

What Steve said plus try the APC 10.5x4.5 prop at 12,000-16,000 rpm. It's a thin blade and effective in that range. Your engine will probably be happier at that RPM. I have never had any luck cutting down APC props, cut down they just don't work very well, unlike other makes of props. Other's mileage may differ.

Larrys4227 · « **Reply #10 on:** June 10, 2015, 02:51:46 PM »

Your RPM's are way too low .... with an 11x4, you should be launching around 9800.

None of my Evo36's like to run in 4-cycle ... all kinds of weirdness happens. Run it in a solid 2 with a hot plug before you do any of this other stuff.

10/18 ---> 10/22 fuel should do just fine.

2.5oz's gets me about 6m30s run time.

One of my Evo36's has 170 flights on it.
The second of my Evo36's has 210 flights.
The third is brand new ..... about 10 bench runs and its sounding perfect.

Medium venturi with either the OS Needle, or ST Needle ... They say the OS is better .... I notice no difference.

Get those RPM's up and let it sing ......

HTH, Larry

Bill Adair · « **Reply #11 on:** June 12, 2015, 02:04:30 PM »

Quote from: Matt Piatkowski on June 10, 2015, 10:05:58 AM

Fuel used: Omega pink, 10% nitro, initially 17-18% total oil ( exact proportion of castor and synthetic unknown ) with SIG castor added by me to bring the total oil content to 20-21%.

Matt,

Do not believe the oil content quoted by Morgan!

Many years ago I evaporated samples of their Omega and Cool Power fuel, and found much less than the 17-18% they claim! My measurements indicated only 12-13%, and that was from 3 samples of each type!

Randy Smith also mentions this discrepancy in his comments, and got approximately the same measurements.

So, if you used their claimed lube levels, you might want to recalculate using a max of 13% lube. Mix a small sample, and try it in your engine to see if that helps.

Bill

Matt Piatkowski · « **Reply #12 on:** June 14, 2015, 03:58:57 PM »

14 flights yesterday and today.

Initial configuration: 10.5x4 APC 2 blade prop ( cut from 11x4), 0.225" ID Evo 36 stock venturi, Byron 10% nitro and 18% oil fuel ( NO CASTOR ADDED), 60' lines (eyelet to eyelet), 1,100 grams (38.8 oz) model ( my Parrot ), 4.5 fl.oz tank.

Results in order of importance:
1. flight time was too short: 2:45 - 3:30 min (!) no matter which one of Evo venturi ( ID 0.225", 0.235" and 0.275"), props ( 10.5x4, 11x4 and 11x5 ), launch RPM ( 9800, 10,200, 10,500 ) or glow plugs ( original Evo 36 glow plug, Thunderbolt 4 stroke and OS Max) I used.
2. Some of you suggested new, customized, smaller opening ( ID 0.175-0.188" ) venturi and it seems to be the only option that may work
3. RPM in flight were still fluctuating during first 2-3 laps but much less than before - I have no explanation why this was happening.

3. If smaller, custom made, venturi or Evo 0.225 venturi with OS Max NVA for 0.20-0.40 engines do not work ( meaning: if I do not get 6 minutes flight time ), I am replacing Evo 36 CL with OS max 40 that showed exceptional performance and much longer flight times on the same tank.

Regards,
Matt

Steve Helmick · « **Reply #13 on:** June 14, 2015, 06:59:43 PM »

I would use the .275" bore venturi, drill through it for a .157" Randy Aero spraybar/nv and add one layer of panty hose mesh, secured with an o-ring. A good 10% nitro fuel like Powermaster 10-18 or 10-22, Sig 10-20 all synthetic, or Wildcat 10-18 Premium should do fine with the TT 11 x 4.5 prop, or the APC 10.5 x 4.5. Again, launch 9.5k to 10k, set by tachometer.

I've read many tributes to using all synthetic oil in these, but I would not be surprised if they came out of the same factory as Magnum/ASP (and other brands) engines. My Magnum XLS .36 didn't care if it was 10-18 Premium Wildcat or PM 10-22, but it always got some castor oil and never a complaint. I noticed in the Magnum (earlier) XLS .36 instruction sheets said to use at least 20% castor oil for break-in, but later just said to use 20%+ oil. My assumption is that 20% castor fuel became very difficult to get, so they had to loosen up the "requirement" to sell any engines. My XLS .36 probably had 20+ gallons of fuel through it when I gave it to Tim, and would still do strings of 12+ one-flip starts in a row.

Steve

dennis lipsett · « **Reply #14 on:** June 14, 2015, 08:03:26 PM »

I have to agree with Steve's remarks on fuel. I've run everything possible through them with good results in every instance. It ran particularly well on 30% Cool Power fuel with a 12.25X3.75 prop on a RC model called the twist.
I do not use any of the supplied venturis, and definitely not their NVA but use venturis from Jim Lee which are true sprinkler with a NVA through the cinch bolt hole. Prop is an 11X4.5 cyclone from Thunder Tiger and the engine is perfectly responsive to adjustment and running characteristics. Fuel is currently Power Master 5 or 10/22 depending on condition
They are not difficult to run and are perhaps one of the few real bargains left to the C/L community if Horizon doesn't do to this engine what they did to the 60, namely discontinue it.

Dennis

Matt Piatkowski · « **Reply #15 on:** June 15, 2015, 07:34:14 AM »

Steve,
I have found a blind spray bar that will fit all Evo 36 CL venturis. Please see the attachment showing two venturis ( on the left 0.235" and 0.275"; the third one, 0.225", is currently mounted in the engine) and the spray bar
The OD of this spray bar is 0.137" with the fuel delivery hole ID=~0.032" ( I could not measure such small hole accurately...seems to be around 0.8 mm. )
This spray bar can be used with the existing Evo 36 CL NVA mounted at the rear of the engine.

Assuming I will drill 0.275" venturi and install this spray bar, the effective area ( choke area) of venturi will change from current ( old) 0.0515 square inches to new 0.0233 square inches - the new area will be only 45% of the old area.

I have read the article by Frank Williams titled "Stunt Venturis", published in Mar/Apr 95 Stunt News and found the following statement:
"....the smaller the venturi the lower the pressure and the greater the (fuel) draw and vice versa."

My main problem is a very short flight time as this engine is heavy drinker considering all the combinations of props, venturis, glow plugs and launch RPM I have tested.

If smaller venturi has greater draw, the engine will use even more fuel and the flight time will further decrease.

Am I missing something here...?? Perhaps I would have to throttle the engine down, use different propellers ( 10x6?) and, in the end, I will be actually saving fuel but can I change the flight time from current 3 - 3:30 min. to 6 minutes introducing this change?

Well...only another round of flight tests will show.

Thanks,
Matt

dennis lipsett · « **Reply #16 on:** June 15, 2015, 07:58:49 AM »

Quote from: Matt Piatkowski on June 15, 2015, 07:34:14 AM

Steve,
I have found a blind spray bar that will fit all Evo 36 CL venturis. Please see the attachment showing two venturis ( on the left 0.235" and 0.275"; the third one, 0.225", is currently mounted in the engine) and the spray bar
The OD of this spray bar is 0.137" with the fuel delivery hole ID=~0.032" ( I could not measure such small hole accurately...seems to be around 0.8 mm. )
This spray bar can be used with the existing Evo 36 CL NVA mounted at the rear of the engine.

Assuming I will drill 0.275" venturi and install this spray bar, the effective area ( choke area) of venturi will change from current ( old) 0.0515 square inches to new 0.0233 square inches - the new area will be only 45% of the old area.

I have read the article by Frank Williams titled "Stunt Venturis", published in Mar/Apr 95 Stunt News and found the following statement:
"....the smaller the venturi the lower the pressure and the greater the (fuel) draw and vice versa."

My main problem is a very short flight time as this engine is heavy drinker considering all the combinations of props, venturis, glow plugs and launch RPM I have tested.

If smaller venturi has greater draw, the engine will use even more fuel and the flight time will further decrease.

Am I missing something here...?? Perhaps I would have to throttle the engine down, use different propellers ( 10x6?) and, in the end, I will be actually saving fuel but can I change the flight time from current 3 - 3:30 min. to 6 minutes introducing this change?

Well...only another round of flight tests will show.

Thanks,
Matt

Matt,

This is my set up. True sprinkler system with a Randy Smith NVA and Jim Lee Venturi. Throat area is about .068/070. I run a uniflow with no pressure 11x4.5 prop and PM fuel the pattern takes slightly less than 4 oz of fuel. Your at least on the right track in reducing the throat area of your venturi as all 3 supplied are too large for efficient operation and make the engine a fuel hog.

Balsa Butcher · « **Reply #17 on:** June 15, 2015, 02:33:13 PM »

Smaller venturi means greater suction but not greater fuel consumption because...smaller venturi means less air means less fuel required to get the ideal fuel/air combination necessary for combustion so NV can be set leaner and still get a good stunt run. Also less fuel means less power but with an Evo 36 that is probably not an issue. BTW: Think I'll order one of those Jim Lee venturis. Nice setup.

dennis lipsett · « **Reply #18 on:** June 15, 2015, 04:35:36 PM »

A true venturi as pictured is not too small, in fact it is correct for the engine. Since you do not have the NVA taking up space you run an appropriate sized venturi.

Dennis

Larrys4227 · « **Reply #19 on:** June 15, 2015, 05:21:58 PM »

I've been discussing this with Matt, and sent him this info via PM, but thought I'd share with the masses.

Images below are from my Engine/Flight Logs ... the first Evo36 begins @ 2009, and the 2nd Evo is 2010.

The first image/Evo36 ..... I fought with it until I replaced the Remote needle with the medium venturi and ST Needle. Surging and low flight times were the worst problems. Once changed, the engine is a keeper requiring no other changes. It remains on the 38Special to this day and is flown regularly.

The second image/Evo36 was fitted with the medium venturi and OS needle right out of the box. Its found homes on a PT-19, Brodak Cardinal, and currently on a P-40.

Steady and strong is the best to describe both these engines, as is.

I have a 3rd engine currently on the bench .... it's running perfectly after a dozen run-in's and have no doubt it perform exactly as the other two.

---------------------------

The first image shows exactly what Matt is experiencing ..... short flight times. I knew I had it in my logs and finally got around to finding it. Getting rid of the remote needle .... drilling the medium venturi and installing a spray bar needle is just what he needs, before anything else. He'll double his run time with this simple change, and he'll have a strong runner that he probably wont want to do anything else to.

Hope this helps .......

BOLD numbers are totals

Each individual line is as follows:
Flights = # flights in that session
Fuel = # of ounces per flight
Prop = Prop size
Time = Flight time for the given ounces per flight

Matt Piatkowski · « **Reply #20 on:** June 16, 2015, 11:25:52 AM »

Everybody,
I will do what Larry advised and report after weekend.

Thank you for your help.
Matt

Steve Helmick · « **Reply #21 on:** June 17, 2015, 05:55:45 PM »

Quote from: Matt Piatkowski on June 15, 2015, 07:34:14 AM

Steve,
I have found a blind spray bar that will fit all Evo 36 CL venturis. Please see the attachment showing two venturis ( on the left 0.235" and 0.275"; the third one, 0.225", is currently mounted in the engine) and the spray bar
The OD of this spray bar is 0.137" with the fuel delivery hole ID=~0.032" ( I could not measure such small hole accurately...seems to be around 0.8 mm. )
This spray bar can be used with the existing Evo 36 CL NVA mounted at the rear of the engine.

Assuming I will drill 0.275" venturi and install this spray bar, the effective area ( choke area) of venturi will change from current ( old) 0.0515 square inches to new 0.0233 square inches - the new area will be only 45% of the old area.

I have read the article by Frank Williams titled "Stunt Venturis", published in Mar/Apr 95 Stunt News and found the following statement:
"....the smaller the venturi the lower the pressure and the greater the (fuel) draw and vice versa."

My main problem is a very short flight time as this engine is heavy drinker considering all the combinations of props, venturis, glow plugs and launch RPM I have tested.

If smaller venturi has greater draw, the engine will use even more fuel and the flight time will further decrease.

Am I missing something here...?? Perhaps I would have to throttle the engine down, use different propellers ( 10x6?) and, in the end, I will be actually saving fuel but can I change the flight time from current 3 - 3:30 min. to 6 minutes introducing this change?

Well...only another round of flight tests will show.

Thanks,
Matt

Matt...The .275" venturi with a .157" dia. spraybar through it would give you an appropriate throat area for your .36. What your scheme would do would give a very large throat area. It would make a lot of horsepower, but not what you want. Read Randy's pinned articles above this forum...good stuff! Stick with 3.75" to 4.5" pitch.

Steve

Matt Piatkowski · « **Reply #22 on:** June 20, 2015, 04:06:52 PM »

Everybody,
Everything went exactly like described by Larry!

My Parrot with Evo 36 C/L with 0.235" stock venturi drilled through and equipped with OS Max NVA for 20-40 engines, clocked between 6 min 20 sec. and 6 min 40 sec in five flights today on 4.5 fl. oz standard soldered tank ( it is not uniflow ). The tank was pressurized from my custom made and very light muffler. The engine runs smoothly and the lines tension is sufficient with lap times 5.3-5.0sec.

Launch RPM were: 9,800, 10,200 and 10,800 respectively on 10.5 x 4 APC prop. Fuel: Byron 10% nitro - no castor added.
Lines: Brodak's 60' 0.018" braided.

After priming, the engine started with a single flip each time except the first time when I did not know the needle setup! COOL!

I consider the problem solved.

Everybody ( but especially Larry) THANK YOU!

Now, I have to "tame" my Evo 60 NX that has already the front Evo 60 C/L venturi and Evo C/L NVA.

I am flying the Parrot again tomorrow trying to fine tune the already excellent setup.

Regards,
Matt

Larrys4227 · « **Reply #23 on:** June 20, 2015, 04:58:02 PM »

Matt -

Glad to hear everything went well .... but, I knew it would.

I'm glad your pleased.

Your fuel mileage will get better, just keep putting up flights and get some run cycles on it.

NOW that you have a baseline that works predictably, are you going to try any of those other things? You've made alot of notes and were offered alot of ideas .... just curious what you might do.

I haven't done a thing beyond what I offered to get yours stable .... to be honest, I found no need to break what isn't broken.

Good luck, and glad it runs nice .... well, actually if you still didn't like it, I would have offered to buy it from you ....

Later ... Happy Flying!!

Larry