# Tuning a Zenith 14992 Carb on a 1/2 VW

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#### Rockiedog2

##### Well-Known Member
Tony
What's the status of the broken crank problem? I been outa the half vw scene for several years now. Last I remember when the problem first surfaced you said yours was grounded and you were gonna make it a 42. Did I remember that right and is that what you did? Is Scott still saying don't run it over 3000 rpm?
Thanks
Joe

#### TFF

##### Well-Known Member
Have you checked the float height and needle seat? Sound like fuel is not flowing freely. Also is your fuel lines connected to the right ports. I have done these things so it's good to check again. I think it's in the float. Hit every oriface with spray carb cleaner.

#### Rockiedog2

##### Well-Known Member
Did you check the fuel vent?
What about the fuel pressure at the carb inlet?

#### Rockiedog2

Here's the club dyno I used to check the HP. As mentioned earlier mine made 38HP with the Zenith 14992; after changing to the dual Mikunis it made 43 and change, don't remember the tenths. Might as well be a 37. That's a lotta power potential and $$wasted. That on less than 50 hours TT on the engine. We know they usually make more power with more time. Most guys don't fool with it to the extent I did, they get it runnin ok and usually are satisfied and got nothin to compare it to. I wanted max performance and fooled with it a long time. Dual egts were the solution for me. Leonard knows PuttPutt well, he's told me several times it's the lightest, highest performance Legal Eagle in the world. He oughta know. Dual carbs and dual egts and lotsa tuning and messing with it. Last edited: #### AJLiberatore ##### Well-Known Member Here's the club dyno I used to check the HP. As mentioned earlier mine made 38HP with the Zenith 14992; after changing to the dual Mikunis it made 43 and change, don't remember the tenths. Might as well be a 37. That's a lotta power potential and$$ wasted. That on less than 50 hours TT on the engine. We know they usually make more power with more time.
View attachment 76457

Most guys don't fool with it to the extent I did, they get it runnin ok and usually are satisfied and got nothin to compare it to. I wanted max performance and fooled with it a long time. Dual egts were the solution for me. Leonard knows PuttPutt well, he's told me several times it's the lightest, highest performance Legal Eagle in the world. He oughta know. Dual carbs and dual egts and lotsa tuning and messing with it.
Rocky ( Joe! ),

Their has been a lot of UL < 254 discussion here on HBA as of late. Would you care to opine as to how you got under the magical 254? I remember reading some of your efforts to do so. Perhaps it requires another thread. I remember reading about 2 gents that built 2 Hummel Ultracruisers and they even drilled out the axle shafts to get to 253 and change. It can be done, However a running list of what to look for from a creative standpoint that is fair game for weight reduction ( using the Wittman or Rutan axioms that might be everything! ) might spur a number of builders imaginations.

My best,
Anthony

p.s. How is your "SS-1" these days?

#### Pops

##### Well-Known Member
Log Member
Rocky ( Joe! ),

Their has been a lot of UL < 254 discussion here on HBA as of late. Would you care to opine as to how you got under the magical 254? I remember reading some of your efforts to do so. Perhaps it requires another thread. I remember reading about 2 gents that built 2 Hummel Ultracruisers and they even drilled out the axle shafts to get to 253 and change. It can be done, However a running list of what to look for from a creative standpoint that is fair game for weight reduction ( using the Wittman or Rutan axioms that might be everything! ) might spur a number of builders imaginations.

My best,
Anthony

p.s. How is your "SS-1" these days?
Yes, how is your SS-1 these days? Been flying it much?

Dan

#### N8053H

##### Well-Known Member
Tony
What's the status of the broken crank problem? I been outa the half vw scene for several years now. Last I remember when the problem first surfaced you said yours was grounded and you were gonna make it a 42. Did I remember that right and is that what you did? Is Scott still saying don't run it over 3000 rpm?
Thanks
Joe
After I posted this saying my 1/2 was grounded I called Scott. My go to guy. We spoke in depth about this for over an hour. He explained to me of all the cranks that have broke all but one was flown on airplanes with speeds of over 100 MPH. All of these had the dual carb setup. We both believe it is the dual carb setup causing the broken cranks. He also informed me to get 45 hp it takes two carbs. My engine was more on the lines of 42 hp with the single Zenith carb. Not one crank has broken when using a single carb. they all had dual carbs. This was what Scott told me. From the last I heard he stopped building the 45 hp or dual carb version of this engine.

#### N8053H

##### Well-Known Member
Here's the club dyno I used to check the HP. As mentioned earlier mine made 38HP with the Zenith 14992; after changing to the dual Mikunis it made 43 and change, don't remember the tenths. Might as well be a 37. That's a lotta power potential and  wasted. That on less than 50 hours TT on the engine. We know they usually make more power with more time.
View attachment 76457

Most guys don't fool with it to the extent I did, they get it runnin ok and usually are satisfied and got nothin to compare it to. I wanted max performance and fooled with it a long time. Dual egts were the solution for me. Leonard knows PuttPutt well, he's told me several times it's the lightest, highest performance Legal Eagle in the world. He oughta know. Dual carbs and dual egts and lotsa tuning and messing with it.
I don't see any carb heat box. These engine build ice faster then you can shake a stick at it. Those exhaust pipes look to be drain pipes. I tried this myself. They will crack at the bend in about 6 hours of flight. Maybe a little less.

That metal line for the oil pressure will also fail if you can not support it at the fitting. The vibration from the engine will cause this. One day after I landed I noticed a drip of oil coming from this line. Mine was also metal. I went to wipe the oil away with my finger. As I touched the metal line it broke in half. Lucky this did not happen in flight. That line is now plastic and tied up away from anything hot. I will never use another metal line on that oil pressure gauge.

#### Rockiedog2

##### Well-Known Member
I don't see any carb heat box. These engine build ice faster then you can shake a stick at it. Those exhaust pipes look to be drain pipes. I tried this myself. They will crack at the bend in about 6 hours of flight. Maybe a little less.

That metal line for the oil pressure will also fail if you can not support it at the fitting. The vibration from the engine will cause this. One day after I landed I noticed a drip of oil coming from this line. Mine was also metal. I went to wipe the oil away with my finger. As I touched the metal line it broke in half. Lucky this did not happen in flight. That line is now plastic and tied up away from anything hot. I will never use another metal line on that oil pressure gauge.
Yep no carb heat box. The thinking always has been that the oil cooler line wrapped around the intake heats the carb body. Well, I've always been skeptical of that since the oil temps stay pretty low on lotsa days and the throat of the carb is a long way from the oil line. But mine never has iced in 300+ hours of often ideal carb ice conditions. No carb heat for mine but you run it on yours Tony. And with the current dual carbs on mine no carb heat cause the carbs sit right there on the back of the head. No ice problems(yet)

As far as the metal line goes...your statement that the line WILL fail may or not be correct. It might. But it never has and neither have any of the 1/8 copper primer lines I've run on all the Lycs and Continentals I've run. I've never had a copper line break anywhere yet but I've had all kinds of plastic and stainless and certified lines break/crack/leak. So any of them can fail Tony. But thanks for the unsolicited advice/admonishment. You won't mind if I disregard it.

As far as the crank break goes...I'm a big fan of Scott's too. Been friends a long time. And he/you may be perfectly correct in your belief that carbs being outa balance is the reason the cranks break. It could be, I won't argue either way. It also could be a combination of other things ganging up on a motor that has finally been developed beyond its limits.
The single carb intake Y is something of a crude affair...don't get me wrong, I like crude and primitive...but there's likely imbalance going on there too. Do you have dual egt on yours Tony? (Most guys don't but sometimes they got all the answers anyway). I suspect that the egts on your single carb setup don't match; they may even be a couple hundred degrees off. Does that mean the cylinders are producing different power? I dunno for sure but I'd say it's as likely as not, maybe more so. At least with the dual carbs we have more options to get both sides synched. And if the dual carbs aren't synched that's on the operator. So far my crank hasn't broken but I do pay attention to my stuff. The dual carb 45 hits hard when it's max tuned I'll allow that, and even tho it's balanced it's not perfectly balanced. That could be a factor as well. What I think is most likely in the crank break problem is a combination of the above mentioned factors(and others I dunno)...and that the single carb "45" is actually making less than 40 horsepower so isn't under much of a strain atall. And 45 horses outa that motor even with the carbs synched and all else tuned may be too much. Well, I don't know for sure. And mine may break next time I fly it...I always expect *something* to break. Always. And plan accordingly.
I respect what Scott has to say but he's also got a business to run and lots to think about there.

#### N8053H

##### Well-Known Member
I ran dual CHT's on my 1/2 and they read the same. No EGT's on my 1/2vw.

#### Rockiedog2

##### Well-Known Member
No VW engine I have come across hesitates one bit. They run great from start up to shut down. Also no need to mess with mixture. Set it and forget it. Unless you like to run LOP during taxi as I do.
Like Tony says you can set the mix and forget it if you like. I did that for a while til installed dual egt and then realized it needed (an inflight) mixture control like most other planes. The egt would vary as much as a couple hundred degrees with just daily ambient temp swings...difference between warm afternoon shutdown and cool morning startup. And since on mine the power really came on at >1300 egt I fabbed up a mix control and all the difference...without it we were wasting easily available power and also climb performance suffered noticeably and at best tune it wasn't but about 400 fpm(37 horse), Easy to rig it up...safety wire a 3/8 AL tube to the main mix control at the bottom rear of the bowl and run it in the cockpit and twist as needed for desired mixture/egt. Worked good. On my 45 the mix adjustment was at about a 45 degree down angle so I had to put a tiny ujoint in that one.I got pics but can't find em.
All depends on whether you just wanta hohum putt around the patch or wanta get all the performance you paid for. Easy call for me
Have fun

#### TFF

##### Well-Known Member
EGT is how efficient you are making your horsepower; CHT is how efficient your cooling is. Even CHT is rarely even power.

#### Pops

##### Well-Known Member
Log Member
I am way over powered with the 60 HP and just moved the mixture screw 1/2 turn between winter and summer. 1200+ ROC with my 230 lbs was OK. I checked my EGT with a point and shoot Temp gauge and they all run close enough for Gov work.

#### N8053H

##### Well-Known Member
EGT is how efficient you are making your horsepower; CHT is how efficient your cooling is. Even CHT is rarely even power.
Over work your engine by putting to much of a load on it and CHT's go up. Unload an engine by using to little pitch in the prop and EGT's go up. Now if you do not believe this I can post an EAA webinar that explains this.

When it comes to this mixture control on the Zenith Scott informed me you want it at 2 1/2 turns open. He explained if I must turn this mixture screw three turns open or more I am now fully open. There is nothing left. You can not go any richer or any more fuel flow. He does not like to see this. He likes his mixture at 2 1/2 turns open. He said if I must go 3 turns I need to look at my carburation system. He said I can leave it like this, but he did not recommend it. I am speaking of summer temps or running in the summer. If you are 3 turns open in the summer you will be lean in the winter. You will be at max. rich setting and you will not be able to richen the mixture for cold weather running. This was one reason I knew my four cylinder VW was running lean. The mixture in the summer was three turns open. I never liked this, knew this engine was running lean when I saw this. I ignored it as long as I could. Once the engine was repaired, there was no more ignoring this lean condition. It had to be dealt with.

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#### TFF

##### Well-Known Member
Thats called babying a grenade. If you can over work an engine too easily, its not very strong. I know VWs are not very strong, but voodoo chants is not knowing about how your engine is running. Yes if you keep every operating perimeter a mile below optimum, it will stay running, but you don't know much about it. I'm not saying not to stay on the safe side, but true longevity and efficiency is actually up closer to peak. Mosler went out of business because they pushed the engines too hard, and people stopped trusting them. The parts were fine, just misused. Optimistic numbers is just as miss informed as under numbers. EGT is how well the fuel is being burned. CHT is how well your cooling system is working. Even CHT can have EGTs way out. In reality the low EGT cylinder at the even CHT is the overheating cylinder under threshold. Something should be improved in the system. Everything in designing an engine is about getting fuel in and exhaust out and cooling it. I understand running a VW is like running in third gear of a four speed to keep the load off the engine; you accept you can never achieve or use max horsepower. I still would want to try and get more efficiency from the cylinder that is being the lazy power maker, thats the hobby part of engines. Any engine.

#### N8053H

##### Well-Known Member
Thats called babying a grenade. If you can over work an engine too easily, its not very strong. I know VWs are not very strong, but voodoo chants is not knowing about how your engine is running. Yes if you keep every operating perimeter a mile below optimum, it will stay running, but you don't know much about it. I'm not saying not to stay on the safe side, but true longevity and efficiency is actually up closer to peak. Mosler went out of business because they pushed the engines too hard, and people stopped trusting them. The parts were fine, just misused. Optimistic numbers is just as miss informed as under numbers. EGT is how well the fuel is being burned. CHT is how well your cooling system is working. Even CHT can have EGTs way out. In reality the low EGT cylinder at the even CHT is the overheating cylinder under threshold. Something should be improved in the system. Everything in designing an engine is about getting fuel in and exhaust out and cooling it. I understand running a VW is like running in third gear of a four speed to keep the load off the engine; you accept you can never achieve or use max horsepower. I still would want to try and get more efficiency from the cylinder that is being the lazy power maker, thats the hobby part of engines. Any engine.
You lack one very important gauge. That gauge would be a MP gauge. Both Scott and I agree we would never fly a vw engine and not have one. This gauge tells you how hard you are working the engine. RPM's only tell part of the story. He told me of all the engines he see's coming back in his shop, they are operated over 25mp. He told me to keep this gauge between 23-25 and the engine will last a very long time. Most times I keep MP between 21-23 in cruise flight.

Log Member
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#### Rockiedog2

##### Well-Known Member
In reality the low EGT cylinder at the even CHT is the overheating cylinder under threshold.
Tom
How bout talking about that a little more. I'm not quite getting it the way it's stated.
Thx

#### Rockiedog2

##### Well-Known Member
You lack one very important gauge. That gauge would be a MP gauge. Both Scott and I agree we would never fly a vw engine and not have one. This gauge tells you how hard you are working the engine. RPM's only tell part of the story. He told me of all the engines he see's coming back in his shop, they are operated over 25mp. He told me to keep this gauge between 23-25 and the engine will last a very long time. Most times I keep MP between 21-23 in cruise flight.
That's why after thinking about it a while I decided to disregard Scott's stated 3000rpm max limit after the crank breaks occurred. That sounded arbitrary to me; for all I know 3K rpm may be the exact wrong rpm to run mine. I was gonna add MP but ended up parking it before got around to it. Mine is propped so thin I doubt it's working very hard at any cruise rpm but need to check that.
I'm about to get him out and get him goin shortly tho so will add one. He's been sittin back there in the back hangar for a couple years; he's bad pissed off about it too.

#### Rockiedog2

##### Well-Known Member
Those exhaust pipes look to be drain pipes. I tried this myself. They will crack at the bend in about 6 hours of flight. Maybe a little less.
Hi Tony
Yep those are sink drains. Thin chrome plated brass. Lightest thing out there. I been running em on my half for 300+hours and yeh they crack at the flange. I've replaced em twice on mine so for me they run about a hundred hours which is plenty good.
Maybe you oughta check your mix balance; sounds like you got a rough runnin motor.

Tony, just cause your s**t gives a lotta trouble don't mean everybody's does.

LOL

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