Fuel injection

[HalcyonS]

OK, good thread. I get the idea. Thanks all for chiming in. Even though it went way off topic
I'm just leery of having to pull my carb apart every year because of weird ethanol fuel deposits which seem to precipitate out - ie they get through my 50/20/10 micron filter bank.

[sastanley]

I really think the key is the ethanol fuel you just mentioned gumming up the carb. A lot of local hardware stores around here like Tractor Supply and True Value are selling ($$) ethanol free gas for things like chainsaws in 1-2 quart containers for a few dollars. It might be worth it to disconnect the fuel line and winterize with that if you do not have an ethanol-free fuel source or plan to store the motor for an extended period in a non-winterizing location (I have a local ethanol-free fuel source, and it is about $3.65/gallon presently..that is worth it to me.)

[ndutton]

Please, please be cautious where you get your ethanol information. There are known problems (older hoses and fiberglass tanks for example) but the reality is nowhere near the doomsday stories floating about.

For example, should you take the previous paragraph as the truth? Absolutely not! I'm a boatbuilder from way back and have over two decades of anecdotal experience with ethanol blended fuel in marine engines but in no way does that qualify me as an authority on ethanol blended fuel and its effects in the marine environment. That does not mean the first paragraph is untrue either. You just don't know for sure.

Instead, weigh the information on the credentials of its source. Who to believe, some boat gypsy forum schlubb sitting at his computer at 1:00 A.M. or Mercury Marine (as presented by BOAT US)?

http://www.boatus.com/magazine/2011/december/ethanol.asp

[ndutton]

As far as fuel for the engine the best thing for an A-4 would be a much smaller carb. I have toyed with the idea of converting to down draft and using n old VW 36 horse carb, now that would really work. What would be best would be to find a far smaller updraft style.

I'd like to learn more about this. Do you mean our stock carb is capable of delivering more air and fuel than needed? Or do you mean since we typically run at ~60% of max RPM due to prop loading we'd be better off with a carb suited to 18~20 HP? Do you feel the same on direct drive and higher RPM reduction gear engines?

[Dave Neptune]

Carbs~FII~&the A--4 an opin

Neil, yes I do mean that the carb is bigger than necessary. It was a very common thing way back as there were not that many to ""CHOOSE FROM" that met the engine manufactures criteria, so they choose something close. It is not a bad thing, it is just not as efficient across the power band. This same late model carb is capable of developing 70hp on larger engines.

A good rule for "economy" is to run a bit smaller than absolutely necessary as the carb will work across it's "designed" power band. Much can be done inside the carbs themselves which is why you will see many part numbers on the same "basic" carb. The differences are inside as the transfer bleeds and the metering will be calibrated for the application. You can find many "application part numbers" for our Zeniths. It is the same carb just calibrated differently for it's application. All of the different part numbered carbs will work on just about everything that it will bolt up too but efficiency comes to play.

We are running a "load duty" application so we want the power band to be at as close to WOT as possible when the engine is working under loads. This puts the carb well into the "last of the power stage" of the carb where it will be most efficient in getting a good mix to the cylinders. This good mix happens at higher velocities through the carb at it's upper limits. Everything below that accept base IDLE is a compromise of proper mix. This is where FI becomes more efficient, mostly on the in between RPM ranges. I have sat in on tests with the same engine ( Niel, it was the owners red Camero where one of your friends works) on a dyno using FI and carburation. They both idled fine and the carb actually made the most power and I think it was around 6hp on a 500 horse engine. On the track the FI was clearly much faster as it had a power advantage coming out of turns via the efficiency and mix control in the mid-ranges. On the drag strip they were virtually the same and being faster was a matter of the run being driven.
Take Hanley's ""Xboxes" approach. He can vary the spark intensity and with his O2 sensor he can tweak his adj jet to a good mix. The fact that he can do this points out the inefficiencies of a GOOD carb our Zeniths.
The 36 hp VW carb would be a good "power match" for the A-4 however mounting and sequencing of the internals may take a tweak or two.
The Zeniths have a replaceable VENTURI much like Webbers and if a smaller one could be found and the data could be extracted from Zenith on the internals we would be better off.
I have found some inequities in many of the A-4 carbs I have done for A-4's over the years. I have found after market jets that do not follow Zeniths actual openings and a few different emulsion tubes as well. The original combination provided to Universal has been somewhat bastardized and the after market jets add to the problems at the rebuilders.
Now if we were to develop a smaller carb and really got it dialed in or it's mix across the power band it would probably take at least 10 hours of running to measure any gains in overall economy and this is pretty much the same when trying to convert to FI. It just is not worth the effort and investment to go FI for so little gain in a load duty application.
A good well balanced and set Zenith is going to be hard to beat unless a major investment is made and it just is not worth the effort in my opin.
I have massaged the internals of my carb and have only seen a few with the same sequencing in the emulsion wells, these were all on very old carbs that could be stated to be still original.

My carb has been on and not removed now for 5 years running E-regular gas. It runs great and my economy is right there with some of the best claims I have seen on this site. I put a lot of hours on so my fuel is mostly fresh and my tank is clean. My Racor is now at least 10 years old and the filter has not been touched in that time. I do run a polishing filter before the carb and I do not remember when it was last changed out. I use no additives and I only get my gas from a gas station not a marina gas dock!!

We should also notice that the more a boat is run the less trouble we have. The engines that are started just to get out of the marina and barely ever even warmed up are the ones with seemingly fuel related problems especially regarding contamination.

Most A-4 carb problems are related to an internal air leak (the matching of the halves), improper float setting (the Zenith is very sensitive to float level and not the angle of the mounting as it is center fed) and not getting everything out of idle and mid range passages when cleaning.

OUT
Dave Neptune

[ndutton]

Thanks Dave, exactly what I was looking for. Have you ever tried or can you predict the effect of tweaking the bowl vent jet?

[Dave Neptune]

Neil, what you are referring to "bowl vent" is to keep the "float bowl" at the same ambient pressure as the carb throat in the Zenith. This vent keeps the pressure constant and maintains the float level regarding air pressure.

What I think you mean is the "emulsion well's" "air corrector" in the center of the bowl. The "air corrector" jet works with the emulsion tube to mix air into the fuel before heading to the venturi discharge. The air jet works just the opposite of a fuel jet. It will lean the mix with a larger jet by mixing more air into the fuel and visa versa. Now the jet has little influence as "this stage" of the carb begins to function and it's influence increases as you go further into the range. The "emulsion tube" has many holes at varying heights (float level influences this too) along the tube. This tube is what manages the air in the fuel and many are available for many apps. The fuel is drawn via vacuum through the main jet for rough metering to get the supply close to demands.. From the jet the fuel enters the emulsion well where air being drawn in via vacuum again is sucked up the well. As it is being sucked up the well the vacuum again draws air through the "air corrector jet" and is mixed in at various levels depending on demand. The propose of these wells is to break up the fuel with tiny bubbles to get it started mixing and "atomizing" the fuel for disbursement into the discharge tube. This bubbly mass of fuel and air is then further torn apart or mixed by the air flowing through the carb for better burning in the cylinders when the air from the venture further breaks up the fuel droplets.
There are 3 stages in this Zenith. We have two idle circuits in basically one. There is a discharge just below the butterfly and another just above it for "off idle" running until the "main jet and well" take over. There is a mixing well in the idle circuit as well as an "air corrector". By changing air correctors and float levels as well as e-tubes you can massage where one stage "transfers" to another. This is what is called the balance of a carb to work in a specific application. Example lets take a small displacement engine that makes 18 hp at 6k RPM's and our A-4 making the same at 2000. The requirement for fuel will be the same however it must be delivered at different ratios to get to the same total for each engine in its power range.

A very good basis for a carbureted gasoline engine as far as HP to the amount of fuel is considered to be around "2 horse power per pound of fuel per hour" in load duty engines. So if we are using 1 gallon an hour the engine should be producing around 2 times 7lbs (approx. weight for a gallon of gas) or 14 HP. If I cruise at 2000/2100 with my Indigo I am using about a gallon an hour and getting around 14 HP. This gives me anywhere rom 4.5~6 kts depending on bottom and prop cleanliness as well as the sea state.

Dave Neptune

[ndutton]

I just read an internet 'news' item about increased ethanol mandate for 2016 and beyond. It was filled with the normal arguments for and against, mostly political stuff and the reason I'm not bothering to include a link but the legitimate technical concerns revolved around fuel hose composition, emission sensor compatibility and gasket materials.

The hose business we already knew, the sensor compatibility doesn't really apply to the A4 but the gaskets, I'd like to learn more about that.

FYI speaking of sensors, the fuel pressure switch included in the EWDS is alcohol rated.

[sastanley]

Around here in the D.C. area we are hearing TV commercials to stop the "red tape" related to ethanol mandates. I pay just enough attention to know that, but I should probably pay more attention. If I see it again soon, I'll add an update to the website.

I think most authoritative marine entities realize that 15% or more ethanol mandates are an issue. Let's hope level heads prevail. I will certainly contact my local politicians if needed.

P.S.> Dave - I now know more about low HP carbs than I ever wanted to know, but it is really fascinating...thanks!

[HalcyonS]

Who to believe, some boat gypsy forum schlubb sitting at his computer at 1:00 A.M. or Mercury Marine (as presented by BOAT US)?

http://www.boatus.com/magazine/2011/...er/ethanol.asp

Hey - who you calling a schlubb?
Neil, that was a very useful article.
"Even in new engines and tanks, E10 will sometimes form a mysterious gooey substance that will also clog filters. Richard Kolb, the manager of Emissions and Regulations for Volvo Penta, believes the goo is caused by water mixing with one or more of the 108 approved compounds that can be used in gasoline. "
This is an explanation for what I referred to elsewhere as 'carburetor cheese'. The big problem I see is that - for those of us who do not have access to avgas - this 'carburetor cheese' problem is not going to go away. And since there are many secret gas formulations, its going to be difficult to find out whose gas is best for our (anachronistic) purposes.

[HalcyonS]

add water to gas for better performance

Years ago I worked with a shop tech in Australia who spoke of water injectors used by hot-rodders to enhance engine performance. The theory was that if you inject a little water vapor into the cylinder at the time of spark, you use excess heat making steam - creating more compression and keeping head cooler. I never heard of it again, but water in ethanol must be doing the same thing.

[HalcyonS]

alternative venturi

Dave, to echo others, thanks for the expert report on Zenith carbs. I've heard you mention the 'different venturi tube' idea before. Have you, or anyone, located/fitted tested such ?

[HalcyonS]

FI again

sorry if I'm flogging a dead horse. But if ethanol content goes up, and if we have a cocktail of secret additives which dissolve hoses etc, then the liklihood of carb and fuel pump gumming issues will only increase. I know my beastie is very happy when it is run at least weekly, but for many of us, family/work/travel/illness etc mean that sometimes doesn't happen. Annual carb rebuilds get tiresome. That is why I was casting around for alternatives. I looked into doing a DIY fuel injection conversion - the bike and cart crowds seem to be doing it:
This outfit does up to 800cc - the throttle body looks comparable to our carb...

http://www.ecotrons.com/products/400cc_to_800cc_engine_fuel_injection_kit/

Then there's megasquirt -

http://www.hotrod.com/how-to/engine/116-0403-budget-electronic-fuel-injection/

http://www.diyautotune.com/tech_articles/megasquirt-carb-to-efi-part1-nova.htm

Here's a report form a guy putting FI on a VW 2000cc.

http://wiki.bozemanmakers.com/index.php/DIY_Fuel_Injection_for_a_Type_4_VW_Engine

and here is one made for big italian bikes - ducati, moto guzzi and laverda...

At this point I'm outta my depth, I'll leave it to others to tell if there is any future in the idea.

[joe_db]

Water injection is fairly well known among people running very high boost. The cooling effect allows much more boost than would otherwise be possible. The A4 is such a low compression engine that this would not apply. The awful goop made from ethanol and water when it separates out from the fuel does nothing but kill the engine.

http://www.dragzine.com/tech-stories/engine/get-schooled-water-methanol-injection-101/

Years ago I worked with a shop tech in Australia who spoke of water injectors used by hot-rodders to enhance engine performance. The theory was that if you inject a little water vapor into the cylinder at the time of spark, you use excess heat making steam - creating more compression and keeping head cooler. I never heard of it again, but water in ethanol must be doing the same thing.

[ndutton]

Hey - who you calling a schlubb?

It's self explanatory. Take a look at the time I posted what you quoted.