# Compression Ratio

#### iamane12d

##### Member
well... i didnt no which catagory this question would go to... so i went here... kinna stupid... but yeah... whut is compression ratio... kind of lost on that subject... can anyone help???

#### B16

##### Super Moderator
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Originally posted by iamane12d@Feb 23 2003, 01:05 PM
well... i didnt no which catagory this question would go to... so i went here... kinna stupid... but yeah... whut is compression ratio... kind of lost on that subject... can anyone help???

it is the ratio at which the air is compressed in the cylinders. on the intake stroke, a certain amount of air is let into the cylinder, when it is on the compression stroke, it is the ratio at which the air becomes compressed at when the piston reaches TDC (top dead center) would be your compression ratio.

#### iamane12d

##### Member
that article was hella long... i read it all and i got some of it... but... can u guyz be in general.... like... if a cars compression ration is 10:4:1 what does that mean???

#### asmallsol

##### Super Moderator
it means that when the piston is at its highest point (tdc) the space above that is the combustion chamber. When the piston is at BDC, its lowest point, in a 10:1 Comp ratio, then now open area (where the piston was, is now 10 times the size of the combustion chamber.

When gasoline is compressed to a certian point, flashover accors and the fuel will detonate without any sparkplug (basicly how desile engines work). When you raise the compression, the gasoline/air mixture are more eaily ignited so then when the explosion happens, it is more violent making more power. The down side to this is if you run to high of compression, the fuel mixture will blow up before it reaches to top (tdc) causeing major problems. To prevent this, higher octage gas is used. Higher octage gas resists early detonation.

#### asmallsol

##### Super Moderator

To better explain it. here is an engine, When it is at the top that is the combustion chamber, when the piston moves down, the combustion chamber increases 10.2 times making 10.2:1 compression ratio

#### iamane12d

##### Member
well... imma tell the truth... im 14 and really wanna get into the import scene and hope to be an engineerer one day... i dont wanna be the posers that say this and that and dont live up to they word... i wanna learn everything there is about engines but import wise.... so if anyone had an AIM or AOL screennames i can have so i can i ask questions.... cuz theres alot of things of confused with

i knoe sounds pethetic but if anyone can help i'll be really aprecciate it... cuz it hekka hard jus goin around forums adn try to self teach urself

jus a question.. dont want any negative feedbacks

#### phunky.buddha

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Wow only 14?

Well.... if you're GENUINELY interested in becoming an engineer, hit me up on AIM and I'll do my best to answer your questions. The AIM button below my post can be used to reach me. Make sure you say who you are though, otherwise I won't answer your post.

#### kyleirwin

##### Retired OG
Originally posted by iamane12d@Feb 25 2003, 02:07 AM
well... imma tell the truth... im 14 and really wanna get into the import scene and hope to be an engineerer one day... i dont wanna be the posers that say this and that and dont live up to they word... i wanna learn everything there is about engines but import wise.... so if anyone had an AIM or AOL screennames i can have so i can i ask questions.... cuz theres alot of things of confused with

i knoe sounds pethetic but if anyone can help i'll be really aprecciate it... cuz it hekka hard jus goin around forums adn try to self teach urself

jus a question.. dont want any negative feedbacks

i'll answer what i can... my AIM sn is: kylemarhx

#### pills_PMD

##### New Member
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#### phunky.buddha

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#### pills_PMD

##### New Member
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mechanical engineering

#### phunky.buddha

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#### phunky.buddha

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#### asmallsol

##### Super Moderator
iamane12d-

alot can be learned about engines at Howstuffworks.com. Your 14 so does that make you in 9th grade? Biggest recomendation would be to sign up for as many autoclasses as possible. At my school (i am a jr.) there are 4 automotive/engine classes. 1st is small engines (lawn mower engines) In this class you do not learn much about cars but you learn so much about how an engine operates. Next two classes are extremly simple and all you do is basic maintance like brakes and stuff like that. The final course is a big two hour block where you learn just about everything. If you want to do an engine swap in that class, then go ahead. Your school probally has something like this.

I too also want to become an engineer. As for other educational stuff, take alot of science and math classes. (so i am told) most collages make Calculus and AP phyics prereqs that must be taken before entering an Engineering program.

#### phunky.buddha

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Originally posted by asmallsol@Feb 25 2003, 07:04 PM
I too also want to become an engineer. As for other educational stuff, take alot of science and math classes. (so i am told) most collages make Calculus and AP phyics prereqs that must be taken before entering an Engineering program.

Not necessarily- Calculus and Engineering Physics are generally offered as freshman courses. At UT Austin, you have to take 3-4 semesters of Cal, and 2 semesters of Physics, 1-2 semesters of Chemistry and maybe a few more base science classes depending on which engineering discipline you pick. If you're taking AP Cal and Physics and are able to place out for college, make absolutely sure that you feel confident that you can really do everything that you did in your high school courses. If you're the least bit unsure, taking the classes over again helps a lot. I placed out of a bunch of Calculus and Physics before I even got to college, and I took Calculus again anyway. I wish I had taken the Physics again, but I didn't need it as much as the Calc. You just learn so much more at the college level, and seeing it again does help. Hell, even if you're already a math/physics whiz, take it to space out your college career some, if you have the cash to spare for the extra semester. It allows you to get used to the college experience, you get a refresher in your foundation material, and you'll make a good solid GPA base up front. It's a bitch trying to catch up if you fall early- trust me.

Most colleges would like to see that you've taken calculus and physics already, but in reality- most people (at least at UT) retake these just to be sure. This way, they make sure that they're on the same level as everyone else- since not all high schools are equal. The classes that were considered "deficiency removal" coming into UT Engineering were things like pre-calculus and college algebra.

Click on that, and it'll bring you to more information about the ME program at UT. If you scroll down some, there's a general sequence of classes laid out there for you. You can browse through that and get a general feel of what you're expected to take in any top rated mechanical engineering program. I didn't take the classes in an order that looked anything like that list though- if you're ahead in one area, you can take classes as high up as you can and still be on level 1 with another area. Sometimes it's fun, sometimes it really hurts.

#### asmallsol

##### Super Moderator
Thanks mike for the info. Right now i am not really to sure about what feild of engineering i want to go into. Right now i am trying to take alot of automotive classes so that way i will have alot of background if I ever choose to go to automotive engineering. My dream job would be to be an engineer for a racing company like toda or honda's racing division (dont think that will ever happen but it is alright to dream.

#### phunky.buddha

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No problem Collin.

Automotive classes aren't really going to tell you what kind of engineer you want to be... especially if they're hands on. If you want a career as a grease monkey (no offense to those of you who are, I call myself that too), you don't want to waste your time on an engineering degree to do it. If you want to design parts, that's another matter. The automotive aftermarket is exactly where I want to be, and that's the reason why I decided I wanted to be an ME waaaaaaaaay back when I was 14 years old also. I haven't regretted it since. I'm not in the auto aftermarket yet, but I'll get there one day. Working up to a good management level and making LOTS of friends in the right places, plus trying to get out there and race to start making a name for myself (we'll see) and having a good amount of cash in my back pocket is probably how I'll get there.

My suggestion to you is to talk to universities with good engineering programs in your area, and ask to sit in on some upper level courses. Maybe you can sit in on some of the freshman intro courses too- that'll give you a good idea as to what's in store for you if you choose that route. I seriously doubt that any college would deny you sitting in on one or two classes/lectures. Ask them what's appropriate for you to see. They like someone with ambition- and if you're only 14 and thinking about degrees and career plans already, that'll impress them. Student organizations are probably one of the best places to go to for information. When I was president of my ASME (American Society of Mechanical Engineers) chapter, we had tons of events every year bringing middle school and high school students in and showing them what we do, and what the industry is like. We had speaker meetings twice a month where we brought in companies from the outside to tell us about themselves, and show us what a mechanical engineering graduate might do in their company. Maybe an ASME student chapter near you would have Ford or some other auto company coming in for a speaker meeting, and you could sit in on it.

Talk to local companies. They may not be as willing to show you around since they're all out there trying to make a profit, but you might be able to find out when they're giving tours or open house days where you can check out their operation. Ford is extremely supportive of the university programs... the year I graduated, they donated \$12 million to UT Austin, \$7 million of which went straight to the engineering department. Call their recruiting department- they might have something for you too. You never know until you try...

I just want you to get an idea of what working as an engineer is really like, especially on the design side. It'll be pretty rare to be the one of like... twenty guys on an aftermarket team. Let's say you go work for Honda as a design engineer on the new Civic line- don't be surprised if your whole year is spent designing the front passenger side dash area... there's a LOT of engineering that goes into a car, and one person at the design won't own an entire assembly like the engine, transmission, or body. I talked to someone at Ford who spent 6 months working on a glovebox- it happens.

Make sure this is what you want to do. I got lucky when I made up my mind- don't leave it to luck for yourself.

Damn............ I think I've helped to sufficiently hijack this thread waaaaaaaaaaaaaaay off topic. I should split it off and call it "I wanna be an engineer!"

#### asmallsol

##### Super Moderator
Yea i want to do designing work. The reason why I am taking so many " grease monkey" classes as you call it is that i cant stand feild of science where you doing all this stuff with little electrons and ions but there is no real way to apply this stuff (chem was not for me). With mechanical phyics it is easy to apply the phiyics to everyday life. If i understand how a car works, it would make me understand the phiyics part of it all.

The colleges that i am looking at right now are:

University of Michigan (but my grades are border line for that school, i have like a 3.7, there average is 3.9 gpa)

Michigan State

Michigan Tech.
Michigan tech is an extremly small school but is soly dediacted to engineering and has been recommended to me by many of the ford engineers at the country club i work at.

The last school that is known for engineering in my area is Lawernce Tech. The major problem with that school is that it is a commuter (sp) school but I do not want to live at home. I want the college life also.

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