Premium Gas in a base RSX?

Perhaps so. In the fifteen years or so that I've been posting to Usenet, I've certainly written messages I've later regretted, and many others that could have been better. I don't feel this was one of the former, but it probably falls into the latter category.

"jim beam" wrote

Would someone please define "adiabatic heating temperature"? Please provide your source for this definition. What is the approximate number, in degrees F, for the "adiabatic heating temperature" (AHT) of gasoline at the pressures with which we are concerned here?

Or is Jim just being sloppy?

I know what "adiabatic heating" is, but the statement above seems to be implying the AHT phrase altogether is part of engineering or scientific parlance.

Rather than impetuously call this statement "rubbish," he or someone gets a chance to tweak it.

"Michael Wojcik" wrote jim beam wrote

Not so fast. It's a fact that diesels are higher compression engines, and they do require greater cylinder wall thicknesses, in some proportion to the higher pressures they see, for one. The material cost of a higher compression engine will, in general, be higher.

I would wager that this is true for higher compression "power performance" gasoline engines vs. lower compression gasoline engines, too.

But don't use, say, dealer price for a "performance" car to gage the cost of materials to build the engine. Too many other variables. So we can't go to the net and compare edmunds.com prices for car D with compression ratio x to car G with lower compression ratio y.

A higher octane does not correspond to a higher ignition temperature. Higher octane means "more resistance to self-ignition, particularly, ignition due to high pressure instead of a spark."

Unless you regularly deliver (carefully prepared) lectures on the subject, this is a complicated topic that you should not attempt to summarize off the top of your head. You're butchering a number of points.

Optimize...

"Elle" wrote in news:a8ETe.2176$ snipped-for-privacy@newsread3.news.pas.earthlink.net:

Sort of. Both gasoline and diesel in a diesel engine will autoignite (detonate), exactly as the diesel cycle expects them to. The difference is in the preflame reaction. Cetane fuels (diesels) have a much shorter preflame reaction time than heptane fuels (gasolines). Once the preflame reactions have occurred though, both go up instantly.

The above gleaned from this Google search:

Additonal reasons gasoline is not used in diesels set up for diesel fuel:

1) Low viscosity results in excess fuel delivery 2) Gasoline has insufficient lubricity to protect fuel pump.

It will result in very low power, lots of smoke, and high probability of fuel pump damage. Other than that, according to what I get from the search above, it won't do any damage in the short term. Long term usage /could/ coke up the rings.

thanks for bothering to dig up such a great citation. your summary is a little light in that it's important to distinguish the circumstances under which you can run compression ignition [ci] engines in "multifuel" mode, i.e. even higher compression ratios than required for normal diesel operation. i can tell you from experience, a normal diesel just won't run on gas.

yup.

the military spent a lot of time & a lot of money researching multi-fuel vehicles. ateotd, i think intent was more propaganda in an effort to divert soviet resources than the desire to impliment it in practice because very few vehicles could run in multi-fuel mode, and those that could were run on diesel pretty much all the time.

"squeeze" temperature.

my old lecture notes.

you're not compressing gasoline, you're compressing the air charge in the case of a diesel or the air/fuel charge in the case of spark ignition. for diesels final compression temp is 500-600C. for spark ignition engines, it's in the range 250-350C approx. iirc, diesel fuel ignites in the 400C range, gasoline in the 600C range approx.

kinda, but as i understand it, it's more along the lines of diesel having individual droplets with boundry layer combusion, whereas gas is full vapor that can be detonated by compression waves anywhere.

diesels can't really ignite at the wrong places because once fuel is injected, it's starting to burn. it doens't get a chance to evaporate into a detonatable vapor. with gas engines, you're trying to get a smooth flame front progressing from the center of the chamber [more or less]. combusion chamber irregularities [think old detroit iron] cause local pressure spots & detonation ahead of the flame front because the fully evaporated vapor is already there.

of course not.

of course not.

"So high-compression engines need fuel with a higher ignition point, which means a higher octane rating."

strictly speaking, that's detonation point, not ignition.

you're saying that higher compression gas engines are build stronger to take that compression. that's not true. output pressure dwarfs compression pressure. the build difference [if any] is ability to cope with the output.

kinda, but it's more detonation sensitivity than just plain temp. rate comes into the equation as well.

to cope with combustion pressure, combustion temperature & mechanical output, not initial compression.

output, not compression.

jim beam wrote in news: snipped-for-privacy@speakeasy.net:

That was a good one, citing many concrete refernces from credible textbooks.

I printed the citation off to read it better to find out why.

Apparently this is because diesel is injected into a diesel engine at about the same time the spark plug fires in a spark engine (16~30deg BTDC). Since it takes gasoline so long to "light off" (detonate), the engine is well past TDC before it can. Therefore, if it ever does detonate, the piston is pretty near the bottom of its power stroke. And usually it never detonates at all, but just gets pumped into the exhaust.

Actually, I read that wrong. I printed off that citation so I could read it better, and discovered that gasoline's low viscosity results in INSUFFICIENT fuel delivery for two reasons:

1) Gasoline's lower density packs less punch per volume, and 2) Some of it squeezes back past the injection pump's plunger instead of going into the injectors the way it's supposed to.

Another mistake here: In that thread, somebody suggested using WD-40 in a diesel. Somebody else said this would coke up the rings in the long term. During my on-line read, misread it as being /gasoline/ as the coker-upper.