Fuel

[Peva]

Peva,

"But for me, it explained in particular why lawnmowers and other smaller engine devices don't tolerate aged ethanol fuel, whereas old ethanol fuel doesn't seem to bother running/starting quality of car"

Free water in fuel is rare, if sourced from a reputable supplier with a high turnover, keeping the fuel fresh. No engine, new or old, likes water in the fuel.

Older engines (fuel systems) even in cars, may not tolerate E in fuel - this is because the system may have components that the E will damage. O rings, hoses, floats, valves, etc are often damaged by E.

Any petrol powered engine (rated to use E blend) will run just fine on ethanol blend. High usage (regular refresh) is the best. Low usage, especially when tank below 75% full, for extended periods, is more likly to result in condensation (water) contaminating the fuel.

"....systems of automobiles are required to be sealed...."

ALL fuel tanks "breathe" atmospheric air - to my understanding no conventional fuel tanks are sealed. True they may have a higher degree of "sealing" than say a mower. If truly sealed. they would collapse as the fuel was used and or atmospheric pressure/temperature changes impacted on them. All air contains more/less water vapour that will condense on relativly cool surfaces. Metal fuel tanks are more prone to condensation than plastic.

"Sealed" was too strong a word. You can fault me for oversimplifying to keep my post less verbose.

(Putting on my tap shoes...)

Car systems allow a controlled pressure relief, and of course, as you suggest, allow air to enter to displace the freed up tank volume as fuel is used. The evaporative emissions system limits (controls) free exchange with the atmosphere in regards to the vapor pressure of the fuel.

That is different than having the tank essentially open to the atmosphere as it would be with a non-sealing gas cap (or passive breather hole in the top of the tank). With the ignition off, the various evaporative emission system valves communicating to the atmosphere are of the "normally closed" type (no free exchange of gaseous substances), so the system at that point is essentially sealed to the atmosphere. When the system is active (ignition on), vapors are ported to the engine plenum (downstream of the throttle body) thru a vacuum hose connection.

 

[stihlmania]

"Sealed" was too strong a word. You can fault me for oversimplifying to keep my post less verbose.

(Putting on my tap shoes...)

Car systems allow a controlled pressure relief, and of course, as you suggest, allow air to enter to displace the freed up tank volume as fuel is used. The evaporative emissions system limits (controls) free exchange with the atmosphere in regards to the vapor pressure of the fuel.

That is different than having the tank essentially open to the atmosphere as it would be with a non-sealing gas cap (or passive breather hole in the top of the tank). With the ignition off, the various evaporative emission system valves communicating to the atmosphere are of the "normally closed" type (no free exchange of gaseous substances), so the system at that point is essentially sealed to the atmosphere. When the system is active (ignition on), vapors are ported to the engine plenum (downstream of the throttle body) thru a vacuum hose connection.

Your typical canister vent valve only closes during engine running evap self testing. This checks evap system integrity….

 

[Peva]

Your typical canister vent valve only closes during engine running evap self testing. This checks evap system integrity….

Here's information from the FSM of one of my vehicles (see the 2 attachments including the evaporative emissions system diagram and some text descriptions). The only paths from the canister to atmosphere are through the purge valve (ports under vacuum to the plenum downstream of the throttle body to suck out and burn any vapors) and through the NVLD (Natural Vacuum Leak Detector assembly) and its breather (on the atmosphere side of the NVLD).

Of the purge valve, the FSM says (in 1st attachment): "When de-energized [which would be the case with ignition off], no vapors are purged."

Of the NVLD, it says (2nd attachment): "The NVLD seals the canister vent during engine off conditions." Elsewhere (not in the attachments), it says: "The normally closed valve in the NVLD is intended to maintain the seal on the evaporative system during the engine off condition."

The only other (third) possible communication path to atmosphere leads to the fuel cap and fuel tank, which are totally dead ended (except when cap is removed).

I think I am correct in saying that the entire point of the federal regulations that drive the design of the fuel and evaporative emissions systems is to prevent raw fuel vapors from going into the atmosphere, which pretty much precludes free breathing in either direction except for brief periods of time, such as when re-fueling (cap off).

 

[hlw49]

Have a Tanaka TBC340 trimmer I bought in 2004 have always used non-ethanol fuel in it and have never done a carb job on it. Go out prime it choke and it starts right up. Runs like a champ.

 

[VirginiaIron]

I have stored ethanol fuel in the "new" oring sealed cans and I have had no issues to date. I use ethanol fuel in everything, without treatment because the gas gets used quickly. But, I do use non-lethal fuel for mixed fuel, chainsaws, and those small engines that do not get run often enough, log splitters/snow blowers. I have noticed that the equipment with metal tanks do have a residue on the inner steel wall which may eventually clog a filter or carburetor. Also, I test my non ethanol fuel purchase at the station.

 

[Riick]

T-bone... Exactly how does the calcium get drawn out of the air?
They taught me, and I've observed, that when "hard water" evaporates into the air, the minerals are left behind. Rainwater is mineral free.
Humidity should, I think, be same/similar.
You sure it's Calcium ??

...... I would be afraid to estimate how many times I've torn down a small-engine carburetor and found lime deposits in the bowl. The lime (calcium) is carried there by water.....

 

[Hammermechanicman]

I just love this thread!
All of the internet scientists
I'm not a qualified internet scientist but i did stay a a holiday inn express once.

 

[Peva]

T-bone... Exactly how does the calcium get drawn out of the air?
They taught me, and I've observed, that when "hard water" evaporates into the air, the minerals are left behind. Rainwater is mineral free.
Humidity should, I think, be same/similar.
You sure it's Calcium ??

I wondered about that too. Distillation does leave calcium behind.

 

[Markdd60]

I just love this thread!
All of the internet scientists
I'm not a qualified internet scientist but i did stay a a holiday inn express once.

These are the best.... rates right up there with dino oil vs synthetics threads. I've only stayed at the "We'll leave the lights on for you" motel.

 

[Skippydiesel]

Peva,
Basic physics can not be avoided - the fuel tank must be subject to pressure equalisation, as the fuel level drops/atmospheric/diurnal changes occur - otherwise it will either collapse or attempt to expand (subject to construction limitations).
Atmospheric air and with it water vapour is being allowed to enter the system you have illustrated.
Further the above system is about reducing fuel vapours entering the atmosphere (exiting the tank) not about air entering the fuel tank, to replace the lost volume due to consumption and equalise internal pressure due to atmospheric and or temperature changes.