Tee Dee 049/051 Needle Valve Body - Testers Wanted!

I'll give it a try. I'd think it would work pretty well with a balloon tank. Probably not fine enough for a bladder...

The Beta Mark

I look forward to participating in your beta testing. The world needs more spare TD parts.

Hello Mr. Matt, it is possible that for the geographical place where I live, it does not serve you commercially speaking, but if you still believe it is possible, I also offer to collaborate, since you can count on me if you wish.
Greetings.

EXModelEngines wrote:

MauricioB wrote:Hello Mr. Matt, it is possible that for the geographical place where I live, it does not serve you commercially speaking, but if you still believe it is possible, I also offer to collaborate, since you can count on me if you wish.
Greetings.

We have no problem shipping there if you would like to participate. If so, drop me an email at sales@exmodelengines.com

Thanks!.. Sent

I would love to test the spray bar out! Any excuse to break out the old 051

Hi Matt,

I may be located way too far from you but just in case you are interested in me testing the spraybar, I would gladly volunteer!

András

Thanks Matt no ptoblem. I will then wait for the test results and may be in to buy one.

I

received the needle valve assembly yesterday.  That was fast!  I will do my best to try to test it this evening if i can get caught up on work around here.  I've decided to test the setup on a TD .049 I just finished rescuing from the scrap heap.  It was in a bag of old crusty Cox engines that a local clubmember gave me.  It pretty rough at first but once I was able to get it apart, it cleaned up pretty good and had good compression.  Had an original #4 cylinder which was a plus.  I polished all the metal bits back to a shine, replaced the cracked carb, and installed a turbo plug glow head with an OS P4 plug.  I finished the restoration and put the engine back in my box about the time this thread was started by Matt.  Seems it was meant to use it as a test bed.  I'll attempt to get it running and tuned with the stock NVA before switching over so I can compare them.  If all goes well, I'll throw it on a plane and head out to the flying field.

Tee Bee I am looking forward to your test results. I am a bit concerned with the plug adaptor head though that in my experience has never been able to deliver the same output as the stock COX high compression head. So if you have one I would suggest you do the test with the stock head so that the comparison between the carbs should be in the usual 20k+rpm range where TD-s run the happiest.

Sorry to put my nose into this.

Valid point, balogh.  I'll switch to a TD head for the test run.  When I did a side by side comparison of the venturis, Matt's has a slightly larger I.D. than the stocker.  That could be an issue with my flying setups, as I run vented non-pressurized tanks in my planes. I usually run sleeved down "Dickeybird" style venturis to achieve good fuel draw.  For those that aren't familiar with Milton Dickey's famous Dickeybird .049s, he achieved good success with exhaust throttling these engines years ago with nice reliable idles.  He set a bunch of throttled TDs up for folks and one of the mods he made was to sleeve down, then smooth out the venturi ID.  When I started having trouble flying these years ago on vented tanks, he sent me one of his modded venturis.  The plane ran great with it.  I've since aquired a couple of other engines he set up this way and they have run well.  Only testing will answer the question of how well it will draw fuel.

Here's some static run test results.  Keep in mind that I am testing Matt's new NVA assembly during this process and am not trying to break tach records.  I want to know if the product will serve the modeler in the field as well as the original unit in similar use situations.  Here ya go:

Since I had never run this engine before, I wanted to check it out in it's stock form first.  Following bologh's request, I installed an OEM TD glow head for all the runs.  A Cox 5x3 prop was used for all the runs.   Sig 25% Champion fuel with added castor was used on each run.  Temp and humidity were off the chart on the TX coast. Power robbing conditions, for sure. I was pleased to see the engine start without much fuss.  After some warm up time to let it spew out all the old gunk and oil, I leaned it out to a setting which was the best compromise between a nose-high lean attitude and a nose-low rich one.  A setting I would feel comfortable flying with, not necessarily peak RPMs.  Remember, I fly vented tanks, not pressurized ones and mixture adjustment is an exact guess on each flight. I used a GloBee tach and was surprised at the low numbers it gave me because the engine sounded strong.  Hmmm.

Run #1 Stock TD .049.  17k RPM.  Low numbers but she ran nice and smooth.  Fairly consistent needle setting with attitude changes.  

Run #2 Stock needle valve assembly w/Matt's larger diameter venturi.  Best setting was around 4 turns out.  17,050 RPM.  Some sensitivity finding the sweet spot and it varied more with attitude changes than with the smaller venturi, taking me back to my old days of fuel draw problems.

Run #3.  Matt's NVA and venturi.  17k RPM.  The best setting was achieved at about 7! turns out.  Very sensitive needling.  Just a click or two either way caused big changes in mixture.  I tinkered with it a few minutes and the sensitivity remained as well as BIG changes with attitude changes.  Too lean when nose up.  Too rich when nose down.

Run#4.  Matt's NVA with one of my sleeved Dickeybird venturis.  16.8k RPM.  Power slightly down due to reduced air flow but it was a nice smooth run.  Best needle setting was around 5 turns out and much less sensitive to small needle changes or attitude adjustments.  I would have been confident enough to fly it with this setup and hope to give it a shot.

Static run summary with my vented tanked setup:  

The new NVA assembly looks promising as an alternative to the original units.  My performance issues today were mostly related to fuel draw issues which plagued me long ago when I started running TDs on vented tanks.  The sleeved venturi trick is what saved my efforts and has allowed me to continue sport flying these engines with traditional vented tanks all these years.  So, when you compare apples to apples, Matt's new NVA seems to work equally as well as the OEM when set up in the same fashion.  Nice job!  If the weather holds out, I'll try to get a flight or 2 on the setup this evening.  

I hope I have provided a valuable data point.  Maybe someone else will put the NVA to task on a pressurized fuel tank.  

My test mule:

Update!  Flight report!

Time to update the NVA performance.  I went out to the flying field and made 5 flights using the new parts with different setups.  My tach battery died, so no data there.  

The first flight was made using the sleeved venturi and a Cox 5x3 prop.  Decent flight performance as the engine began to get more seasoned.  The needle setting was consistent.  No complaints.  

Next, I tried an APC 5.7x3 prop with a 1" spinner.  Performance was very similar in the air and once again, the needle setting was easy to achieve and pretty consistent during the run.  The little engine seemed to be getting stronger with time.

On the third flight, I tried a Cox 4.5x4 prop for giggles.  I've had it for a while but had never used it.  My goodness, the revs picked up!  As expected, all that noise resulted in just a slight increase in flight speed.  Once it was pulled hard in a turn or climb, it would fall off the step a bit and wallow around until forward momentum was regained.  Big loops from level flight did not occur.  The needle setting was once again very consistent!

I was about to pack it in for the day but noticed that the Cox 5x3 I had been using was one of those lower performance units with the thick lip near the hub to help engage a starter spring.  I grabbed a proper 5x3 without the "lips" and decided to go for broke by installing Matt's "big bore" venturi as well.  As I ready mentioned, the little TD had really come a long way in it's running characteristics since the static runs earlier today.  When I cranked it up this time, I did not have to run it 7 turns out.  I spent a moment leaning it for good performance and gave it the old heave ho, expecting fuel draw problems to rear their heads once in the air.  That did not happen.  I experienced one of the best TD .049 runs of my life on that last flight.  In 8yrs of flying the old Das Splat Jr, it had never performed so well!  Great speed, wonderful climb rate, good prop loading.  Steady needle setting!  I had finally found the Holy Grail settings and parts setup for this engine/plane combination.  After that, I decided to pack up and not push my luck.

My final summary of the EX Model Engines needle valve assembly:
Parts quality is top notch.  Fit is good.  The venturi fits very snuggly in the housing which all but eliminates the possibility of an air leak.  With the tight fit, care must be taken during the assembly to avoid stripping the plastic carb body threads or slipping and breaking something.  Once I learned to engage the threads of the venturi into the carb before sliding the housing into it's snug position, things went much easier.  It just requires a bit of care and patience to get it mounted.  I was a little concerned that I might strip the carb threads before I got it snugged up but it worked out ok.  Besides, if I broke the carb, I'm sure Matt would be glad to sell me another. I attempted to install a plastic knob from a Surestart needle onto the knurled end but it was too loose to work without being glued on. Maybe consider a knob on production units with a marker to help keep track of how many turns out? No biggie. With the issues of a newly refurbished engine needing break-in time out of the way, this NVA performed just fine.  If Matt would be so kind as to let me keep it, I'll just leave it on this engine and leave this engine on this plane.  Fun times ahead.  I would recommend this product without reservation as a replacement for the OEM unit.  That's my story and I'm sticking to it.

The winning combination

I was able to fly the EX needle-equipped TD again a couple of times this morning in the early calm air before our coastal winds pick up.  This time out, the needle was nearly spot on from the first start since I last ran it yesterday.  We have an early morning flying group of mostly retirees who get together to fly electrics on calm weekday mornings.  They enjoyed the flights and agreed that the .049 seemed "spot on" today.

Great reports Troy! I appreciate the time you've devoted to conducting these tests. Congrats on a winning DSJ set up!

Matt - It looks like you have a winner!!!! I'm glad to see a reasonably priced Precision NVA being brought to market. Once available, I'll be adding EX NVAs to my engines, along with even more goodies from your company. Many thanks for keeping us diehard Cox fans supplied with great products.

Best,
Tony

Very well done, Tee Bee!!! Testing coupled with excellent analysis and good data is hard to come by these days -- too much influence by advertising dollars.

Nice to hear your mention of Dickeybird and of your Das Splat. I remember when you built that plane and had asked how its somewhat odd airfoil performed.

Again, good on ya!

andrew