doradox

Isn't it also possible that ALL the contents of the injector are already vapor before the injector opens? I think it would be more likely than your scenario where the exact conditions for the existence for some, however small, amount superheated liquid have to be present to cause the fuel to experience the phase change at exactly the moment required for it to cause a problem. So to my thinking, superheating isn't critical to explain vapor induced drivability problems in EFI cars. I think your tortured hypothesis may be possible but not one that Occam's razor wouldn't slice the heck out of when speaking , in general, about drivability problems suspected to be caused by fuel, heat, and pressure not playing well together in an EFI system. Steve

So is superheating critical to your theory or is it something that maybe sort of might be happening? Can cogently explain why superheating is a critical point? Steve

Perfect sense. Steve

Yes, you did say vapor doesn't burn and there was no mention of concentration or any other qualifier.

So, speaking of crickets, has your theory changed so you no longer espouse the idea that vapor can't burn? And it sounds like you buddies on Hybrid Z are having a hardware issue. Maybe a clogged pre filter causing a low pressure area before the fuel pump leading to cavitation or vapor lock like conditions. Superheating has a specific definition that can be found here..http://en.wikipedia.org/wiki/Superheating. It may or may not exist inside the injector and is irrelevant. The Geyser effect is more likely and is commonly experienced by folks who think completely releasing a radiator cap on a 110 degree day after driving around for an hour is a good idea. So are you recanting on your "vapor will not burn" position? Steve

Thanks. Much better. Steve

So what I said about vaporized fuel being required for combustion as opposed to not combusting as you had proposed was correct. And my thoughts questioning the injector's capacity to flow the volume of vapor required to support combustion were on track. What you are saying makes more sense now that we have generated a hypothesis that makes physical sense. Interesting. Steve

Atomization helps bring about vaporization which is what fuel needs to burn. Read the conclusions on page 4 and 5 of this document. http://nepis.epa.gov/Exe/ZyNET.exe/91002JP9.txt?ZyActionD=ZyDocument&Client=EPA&Index=Prior%20to%201976&Docs=&Query=APTD0964%20or%20fuel%20or%20atomization%20and%20vapor&Time=&EndTime=&SearchMethod=1&TocRestrict=n&Toc=&TocEntry=&QField=pubnumber^%22APTD0964%22&QFieldYear=&QFieldMonth=&QFieldDay=&UseQField=pubnumber&IntQFieldOp=1&ExtQFieldOp=1&XmlQuery=&File=D%3A\ZYFILES\INDEX%20DATA\70THRU75\TXT\00000007\91002JP9.txt&User=ANONYMOUS&Password=anonymous&SortMethod=h|-&MaximumDocuments=10&FuzzyDegree=0&ImageQuality=r105g16/r105g16/x150y150g16/i600&Display=p|f&DefSeekPage=x&SearchBack=ZyActionL&Back=ZyActionS&BackDesc=Results%20page&MaximumPages=-1&ZyEntry=5

I was thinking about what you said. "Fuel injectors are not good vapor injectors" Is it possible they simply are unable to flow enough vapor to get the mixture rich enough to ignite? Gas volume vs. liquid volume is very roughly 800 to 1. That would be a lot of vapor to pass through the injector nozzle. Steve

Being designed for liquid fuel I don't imagine they are. FWIW I'm a BSME Purdue. Sold the shop, moved to the midwest, went back to school. Any chance the difference in volume of gas vapor vs. liquid is causing trouble? Steve

So you are or were an auto tech? Steve

Do have a source for your assertion that vapor will not burn? I was under the impression that fuel needed to vaporize into air in order for combustion to take place. Something about the fuel molecules needing to be distributed among the O2 molecules so the oxidation reaction (burn) can take place. Maybe vapor isn't the technical term you were looking for. Steve

I would tend to agree with you. Steve

I didn't say you were wrong. Other sources are saying that. I said "A properly functioning FI system is highly unlikely to vapor lock.' I spent 20 years as an auto tech in Tucson and never saw or heard of an injected Z vapor locking. My 75 never did it. Apparently you have some trouble. Steve

I'm not the one saying it never happens. You said read the FSM. So I did. Be careful what you ask for. You just might get it. Steve

I was doing a little light reading and found this little tidbit in the 76 FSM.

It was bound to happen sooner or later. Steve

Bruce, you hit the nail on the head. Heat soak is the major component driving the problem. With the engine shut down the cooling system is no longer carrying away the heat from the engine. That's why cars have catch tanks on the cooling system. Coolant temps rise after shut down because that big hunk of cast iron and AL is HOT. A hot day, hot engine, no air flow, one can get vapor lock. Popping the hood induces air flow as the hottest air rises and escapes and cooler, relatively, air replaces it. Heat radiating from asphalt is not helping but is just one contributing factor. Steve

Fuel injection runs at higher fuel pressure. Fuel and physics DO care about that. That increases the boiling point of the fuel. Also most FI have the pump either in or by the fuel tank. The pump itself never has to try to pump hot vaporized fuel. Also with the higher volume pumps that are run with EFI, if the fuel under the hood is vaporized the pump quickly displaces it with cooler liquid fuel. A properly functioning FI system is highly unlikely to vapor lock. If, while the vehicle is turned off, the system is bleeding off fuel pressure due to a faulty pump check valve, regulator, or injector then the system will be much more susceptible to vapor lock. Steve

Which, with your skill set, you consider "serious engineering". Very telling. Steve

There should already be a fuel return circut. Do you have it functioning? Steve

Not at all. Just that your, and maybe many others, opinion about whether or not something is "worth it" do not a fact make.

2) You must not know what a fact is as (1) clearly states that some might believe the bang for the buck worth it. A fact is always true. Not just when you say it is. 3) One of these things is not like the other. What's with the extra numbers? Did they just magically appear? Or did you get confused and start typing in the quote. 4) And clearly not your place to decide if one feels the expense, however much, is warranted. 5) I guess after editing my post you are the one who could no longer comprehend it's meaning. Again, maybe a little confused. 6) So your statement "3)Last i checked,L-motors are 37+ years old. " had nothing to do with age? WOW.

You said... "2)Correct.But not without serious engineering to retro fit.ANd the benefits gained do NOT warrant the expense." You admit there are benefits then state they aren't worth the expense. How can you possibly know how much those benefits are worth to another person? Therefore your statement is not fact as you can only speak for yourself. It may be fact that YOU don't think it warrants the expense but that isn't what you said. When you quote me don't add edits to my quote. You should really know better than that. The beauty comment was a commentary on the value of the benefits of sequential. Some might find it to have a much greater worth than you. Thus "eye of the beholder". Might have been a little subtle for you. What does the age of the L series have to do with anything? It shouldn't be upgraded to sequential because it's old? I was obviously, at least to most, being sarcastic. Steve

2) Purely your opinion. Beauty is in the eye of the beholder and all, you know. 3) Really. Why bother upgrading at all. They are like, so old.