Gas mileage.. Gas prices

[skeeterone2]

last night while i was thinking about the new mobil oil i was also thinking about gas prices.. and how they suck... and how i dont have any money because of college... and how i cant wait till summer so i can have an income and why it has to be so damn cold in march... anyway... i was trying to figure out how to get better gas mileage... and i was thinking... and the only thing i could think of is to do a hybrid swap... and run smaller injectors... or run injectors with a pulse that had a smaller duration... but i think running smaller injectors would require some tuning of the computer and i have no idea how to do that... but maybe not... im not sure.... gas prices are suppose to go up around 2.50 this spring... and that is a kick in the balls. so i am trying to think ahead... ... smaller injectors... YAY or NAE?

[StudlyCamaro]

RE: Gas mileage.. Gas prices

smaller injectors will just make you run lean, thats a bad idea

what type of mods do you have done to your car right now?

when i got my camaro it was stock and getting around 14 or so MPG, now that ive added a CAI, headers, a cat back/highflow cat, an MSD DIS4, a steeper gear and some weight reduction i consistently get around 27-28 MPG... and i probably dropped a second and a half off my 1/4 mile time in the process

[quantum110]

RE: Gas mileage.. Gas prices

How many miles do you travel to school and work every week?

How about cutting out unnecessary travel...like going out on the weekends...or if you absolutely need to go out have your friends pitch in if they ride w/ you.

[skeeterone2]

RE: Gas mileage.. Gas prices

ram air intake with kn filter and catback exaust... haha i know this is the exact opposite of what this site is all about but i figured there was somebody here that had some ideas... i already can get between 30-34 when i drive like a granny... i was just thinking that there has to be a way to get better... ya know put the honda hybrids in their place. hehe. why is it really bad to run lean... i cant just take that its a bad idea... what is going to happen?... i can take some guesses at it... stalling, runs like shit, hesitation... but couldent this be fixed with some computer tuning... haha.. computer tuning... i dont know how to do that... but i think i could be fixed with that.

[quantum110]

RE: Gas mileage.. Gas prices

Detonation will occur and you could destroy the engine...

Detonation causes three types of failure:

1. Mechanical damage (broken ring lands)
2. Abrasion (pitting of the piston crown)
3. Overheating (scuffed piston skirts due to excess heat input or high coolant temperatures)

The high impact nature of the spike can cause fractures; it can break the spark plug electrodes, the porcelain around the plug, cause a clean fracture of the ring land and can actually cause fracture of valves-intake or exhaust. The piston ring land, either top or second depending on the piston design, is susceptible to fracture type failures. If I were to look at a piston with a second broken ring land, my immediate suspicion would be detonation.

Another thing detonation can cause is a sandblasted appearance to the top of the piston. The piston near the perimeter will typically have that kind of look if detonation occurs. It is a swiss-cheesy look on a microscopic basis. The detonation, the mechanical pounding, actually mechanically erodes or fatigues material out of the piston. You can typically expect to see that sanded look in the part of the chamber most distant from the spark plug, because if you think about it, you would ignite the flame front at the plug, it would travel across the chamber before it got to the farthest reaches of the chamber where the end gas spontaneously combusted. That's where you will see the effects of the detonation; you might see it at the hottest part of the chamber in some engines, possibly by the exhaust valves. In that case the end gas was heated to detonation by the residual heat in the valve.
In a four valve engine with a pent roof chamber with a spark plug in the center, the chamber is fairly uniform in distance around the spark plug. But one may still may see detonation by the exhaust valves because that area is usually the hottest part of the chamber. Where the end gas is going to be hottest is where the damage, if any, will occur.

Because this pressure spike is very severe and of very short duration, it can actually shock the boundary layer of gas that surrounds the piston. Combustion temperatures exceed 1800 degrees. If you subjected an aluminum piston to that temperature, it would just melt. The reason it doesn't melt is because of thermal inertia and because there is a boundary layer of a few molecules thick next to the piston top. This thin layer isolates the flame and causes it to be quenched as the flame approaches this relatively cold material. That combination of actions normally protects the piston and chamber from absorbing that much heat. However, under extreme conditions the shock wave from the detonation spike can cause that boundary layer to breakdown which then lets a lot of heat transfer into those surfaces.

Engines that are detonating will tend to overheat, because the boundary layer of gas gets interrupted against the cylinder head and heat gets transferred from the combustion chamber into the cylinder head and into the coolant. So it starts to overheat. The more it overheats, the hotter the engine, the hotter the end gas, the more it wants to detonate, the more it wants to overheat. It's a snowball effect. That's why an overheating engine wants to detonate and that's why engine detonation tends to cause overheating.

Many times you will see a piston that is scuffed at the "four corners". If you look at the bottom side of a piston you see the piston pin boss. If you look across each pin boss it's solid aluminum with no flexibility. It expands directly into the cylinder wall. However, the skirt of a piston is relatively flexible. If it gets hot, it can deflect. The crown of the piston is actually slightly smaller in diameter on purpose so it doesn't contact the cylinder walls. So if the piston soaks up a lot of heat, because of detonation for instance, the piston expands and drives the piston structure into the cylinder wall causing it to scuff in four places directly across each boss. It's another dead give-a-way sign of detonation. Many times detonation damage is just limited to this.

[skeeterone2]

RE: Gas mileage.. Gas prices

Damn good read.