Premium Gas in a base RSX?

Page 2 of 2  
Elle wrote:


"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.

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote

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: http://tinyurl.com/8h9hj
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.
--
TeGGeR

The Unofficial Honda/Acura FAQ
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
TeGGeR wrote:

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.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

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.
--
TeGGeR

The Unofficial Honda/Acura FAQ
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
writes:

I'd guess it's because of the poor combustion characteristics of gasoline under diesel-level pressures. For maximum efficiency (in a diesel) you want ignition at the forefront of the vapor wave as it enters the cylinder, with combustion proceeding smoothly back through the cloud. Gasoline vapor would tend to spontaneously ignite at unpredictable points within the vapor cloud, resulting in turbulent combustion, poor oxygenation of the flame, and inefficiencies.
According to Wikipedia, some diesel engines can run on E95, which is 5% gasoline and 95% ethanol; the high "octane" (ignition temperature) of the ethanol prevents the vapor from igniting at the wrong places.
Surely you're not denying that higher compression means higher gas temperature (volume being constant)? And that higher temperature increases the likelihood of ignition? I'm not sure what exactly you're taking exception to in the quoted paragraph.

Indeed it is, but I fail to see how the comparison is relevant.

Perhaps so. I'll retract my claim about why high-compression engines are more expensive.
At any rate, the basic point is that the "octane" rating of a sample of gasoline refers to its ignition temperature, and that higher octane means less knock, and that the appropriate octane for an engine will maximize gasoline performance for that engine, with no additional benefit for going higher.
--
Michael Wojcik snipped-for-privacy@microfocus.com

Against all odds, over a noisy telephone line, tapped by the tax authorities
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
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...
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Elle wrote:

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

output, not compression.

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Michael Wojcik wrote:

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.

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
but doesn't the type S and non type S have the same engine? Ones just tuned better?

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Correct. But tuned differently is more correct than tuned better. There are some components that are different, and the ecu is set differently to take advantage of the components.

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Motorsforum.com is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here. All logos and trade names are the property of their respective owners.