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Old Aug 19, 2012, 06:30 PM
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If anyone is still reading this thread. My engine tests with the OEM carb and pump/regulator changes did wonders. The engine is running really good like that too. It will need someone to confirm whether it was the changes or not. I'll have a video posted later showing me running the engine. Video added to this post at the bottom.

Anyway, here is what I did.
A.) I replaced the OEM crankcase and pump pulse pressure fittings with larger 8x32 threaded fittings. That allowed me to use the 1/8 inch Tygon fuel line for stronger pulses going to the fuel pump.
B.) I replaced the OEM pump diaphragm and gasket with a Walbro Teflon pump diaphragm and gasket. The teflon diaphragm pumps better than the black rubber or blue plastic diaphragms do.
C.) I replaced the fuel regulator diaphragm with a Walbro one too.
D.) Michael Chow stated earlier that the low speed needle should be set to about 6 turns out and the high speed 1 and 1/2 turns, I set the needles to 6 turns and 2 turns respectively for my first engine test run to get the engine going. I then dialed in the high speed as needed to get the engine to almost peak out, but not quite peak out in RPMs.

I suspected that the fittings were too small and didn't allow for good crankcase pressure pulses to get to the fuel pump. Also I supected that the OEm NGH pump and regulator diaphragms probsably do not last very long. They work for a while but start going bad pretty quickly after being used (such as the factory test running the engines). But I could be wrong, maybe it just needs larger tubing for the pulses to get to the pump better.

Anyway the engine now gets fuel pumped to it like the Walbro carb does and it isn't leaning out when I point the nose in the air either. Throttle transition is pretty good too. Also idle is still about 1/2 open on the throttle though. The carb still tends to spit some fuel, but it isn't all that bad though. So that may be all that is needed to get the OEM stuff to work OK on the engines.

I'll have to come up with a airplane to try it all on for sure, but feel free to beat me to it.

Here is a short video, I didn't think anyone would want to sit through watching 15 minutes of me running the engine, including longer idle periods and long WOT runs with the engine pointing up, et cetera.
Testing NGH 9cc engine after making some mods to the pump/regulator (1 min 36 sec)
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Old Aug 19, 2012, 07:40 PM
Yes, "that" Karl...
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Good to see you making progress on finding these issues.
I don't have a fuel airplane right now, but this is peaking my interest.
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Old Aug 19, 2012, 11:12 PM
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Can't wait to get home in three weeks to try these things out Earl, well done
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Old Aug 20, 2012, 03:19 AM
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Hi Earl,sorry for pessimist comments from me but;
I dont hope any positive change with nipple improvement.(On flight).
I see tank level is somehow lower than carb on your bench.This was helping engine to keep running consistent while noseup testing.(because of adjustment accordingly).But can you provide same on a plane?Still insist, pump pressure has nothing to do unless regulator needle allows fuel to pass.This permission is the function of the suction from carb line.At WOT this suction still very low comparing idling and though I believe your changes provide better pumping,still regulator needle is the key factor.So I cant be optimistic for plane application.If you adjust to obtain good idling then WOT will be problematic.If you adjust for good WOT then idling will be drowned by excessive fuel.
My humble opinions,sorry.
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Old Aug 20, 2012, 04:02 AM
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Out of interest Earl, what pump diaphragm and gasket kit did you use ?
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Old Aug 20, 2012, 07:03 AM
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Quote:
Originally Posted by brace View Post
Out of interest Earl, what pump diaphragm and gasket kit did you use ?
Well, It was a D10-WAT Walbro kit (K10-WAT?). Unfortunately they seem to have more than one kit from different companies too. I got three different kits for my carbs where one had a blue diaphragm and the other had the white teflon diaphragm. A third kit had a white teflon diaphragm in it but it was missing the one way valve tabs on it. So you want to find the kit with the white teflon diaphragm with the one way valve tabs on it.

When I ordered a repair kit for my WT-298 carb and my WT-520 carb, I got essentially the same kit for both carbs. But they sell a gasket and diaphragm kit without the little metal valve parts, and it has all the different diaphragms in it. The little metal valve parts don't look like they would work in the NGH carb anyway so not getting them isn't going to hurt anything.
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Old Aug 20, 2012, 07:06 AM
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Quote:
Originally Posted by turk1 View Post
Hi Earl,sorry for pessimist comments from me but;
I dont hope any positive change with nipple improvement.(On flight).
I see tank level is somehow lower than carb on your bench.This was helping engine to keep running consistent while noseup testing.(because of adjustment accordingly).But can you provide same on a plane?Still insist, pump pressure has nothing to do unless regulator needle allows fuel to pass.This permission is the function of the suction from carb line.At WOT this suction still very low comparing idling and though I believe your changes provide better pumping,still regulator needle is the key factor.So I cant be optimistic for plane application.If you adjust to obtain good idling then WOT will be problematic.If you adjust for good WOT then idling will be drowned by excessive fuel.
My humble opinions,sorry.
Yeah it is sort of hard to tell from the video, but you could be correct, I'll need to revisit the test and change some things. Yes I need to test fly the engine like that in a plane to be sure. I don't see any loading up at idle with the low speed set to six turns out, it isn't flooding out on me.

But the engine on the test stand never ran that good before except with the Walbro carb on it.
with the stock setup the engine had a huge difference in mixture setting when I point the engine up like that, so much so, I had to run the engine very rich when level.

But I'll re-run the engine tests again, with the fuel tank more centered on the carb and see what happens.
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Old Aug 20, 2012, 08:27 PM
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I thought I would run a test today where I would use the larger fitting pump cover plate with a stock OEM NGH pump regulator and see what happens. The pump behaved much better and pumped fuel really well too, almost as good as the pump I replaced the diaphragms in too. Thus just putting in the larger fittings and using the 1/8" tubing did wonders for improving the pumping action of the unit. So that may be a simple fix for the pump issues. it doesn't cure it completely but it helps a lot and may make it work well for others. But someone else needs to try it too.

I also moved the fuel tank back farther simulating a mid-tank mount setup and it didn't seem to affect the engine's running either. It could draw fuel well anyway at WOT. But the engine could still be drawing fuel the hard way though. I need to test fly the engine and mods to really ascertain whether it works OK or not. Flying a plane around with the setup is the only way to be really sure it is working. But the larger fittings look very promising and the pump and engine runs much better that way. Idle seems to be improved too.
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Old Aug 21, 2012, 09:19 PM
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This isn't as good of a video as I wanted to show. But I had moved the fuel tank back farther than a .40 plane might have the tank over the CG in it for test scenario. I wanted to see if it would get fuel OK like that. it seems to be working. I pinched the pump pressure tube and the engine leaned out so it was acting like the pump was pumping at least some fuel at WOT. I remember how the regular stock setup with small fittings basically wasn't pumping anything when the engine was near WOT. Anyway it looks pretty promising for a modification to make. This is the stock OEM pump with the larger 8x32 fittings to use the larger 1/8 inch fuel tubing for the pump.

NGH 9cc gasoline engine test run using larger fittings on the OEM stock pump and engine (2 min 52 sec)
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Old Aug 22, 2012, 12:12 AM
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That s promising.I didnt expect such an improve.Great work Earl.Thanks.
Time to tests for my engines too according to your experiences.
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Old Aug 22, 2012, 07:46 AM
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There is video from NGH running the 9 with the fuel tank on the floor and the engine in the test bench. It was drawing fuel 1 meter vertically. It doesn't seem like a problem?

Greg
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Old Aug 22, 2012, 07:55 AM
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Both of my 9cc engines refused to do that. They both had trouble drawing fuel like that. They might be able to run with a fuel tank sitting on the floor now. But I didn't try it.
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Old Aug 22, 2012, 09:53 AM
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I have 2 GT9 engines now.One of them was for a friend. After bench running succesfully and break in he mounted it to a plane.We unable to run it properly on plane.Couldnt have proper adjustment to run it nose up at WOT.So he remove and gave it to me.Then I didnt attempt to have mine on a plane.
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Old Aug 22, 2012, 05:02 PM
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Quote:
Originally Posted by earlwb View Post
Both of my 9cc engines refused to do that. They both had trouble drawing fuel like that. They might be able to run with a fuel tank sitting on the floor now. But I didn't try it.
Did you ever use 3/32" tubing?
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Old Aug 22, 2012, 05:43 PM
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Did you ever use 3/32" tubing?
Yes that was the original size I used. I think the NGH fittings are a bit small and have a single rounded off barb on them, but the 3/32" tubing fits OK. It would have been nicer if the fittings were a little larger and had double barbs too.

But in my opinion the small fittings with a small inside hole size and 3/32" tubing was too small to allow for good strong pulses to get to the pump to operate the diaphragm good. Thus the pump seemed to stop pumping at WOT or near to it. So I replaced the pump fittings on the engine and pump with 8x32 sized fittings and used 1/8" tubing instead. That size tubing works well on the Walbro carbs, where I use a external pulse setup too.

My MVVS 35cc engine and my SV 17cc engine both work with that larger size tubing albeit their fittings are still a little larger though with a even slightly larger hole size for the pulses to go through. Anyway that was where I got the idea to try larger fittings and tubing on the pump side of my engines from. I think that even my example of the NGH 17cc engine uses the metric version size fittings with the larger tubing on it too.
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