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Discussion Starter · #1 ·
These questions are going to be hard but just wanted to see how good you guys are at tracking down an answer if you don't know it.

I'm not trying to be a dick here (I think both of you would make great moderators) but just trying to see if I can stump ya.

1.What is octane rating of gas mean. If the Si requires 91+ octane fuel wouldn't using 98 or even 100 octane fuel give me more power?

2.The ignition timming on a Si is set at +16 deg. BTDC. Why would you want to fire the spark plug and ignite the air fuel mixture while the piston is still traveling up?

3.What is VTEC and how does it work?

4.Can I use synthetic oil in my engine (it only has 7000 miles on it now)? My dealership told me use normal oil until at least 30,000 miles to give the seals time to break-in, is this true? What are the advantages to using synthetic oil verse normal oil?

Good luck guys, and I hope Mike SHO lets you both be moderators real soon.
 

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2000 EBP Si said:
These questions are going to be hard but just wanted to see how good you guys are at tracking down an answer if you don't know it.
I'm not trying to be a dick here (I think both of you would make great moderators) but just trying to see if I can stump ya.
1.What is octane rating of gas mean. If the Si requires 91+ octane fuel wouldn't using 98 or even 100 octane fuel give me more power?
2.The ignition timming on a Si is set at +16 deg. BTDC. Why would you want to fire the spark plug and ignite the air fuel mixture while the piston is still traveling up?
3.What is VTEC and how does it work?
4.Can I use synthetic oil in my engine (it only has 7000 miles on it now)? My dealership told me use normal oil until at least 30,000 miles to give the seals time to break-in, is this true? What are the advantages to using synthetic oil verse normal oil?
Good luck guys, and I hope Mike SHO lets you both be moderators real soon.
I took questions 1 & 3, I leave 2 & 4 for v00tecsi because I know how he loves to answer questions to:

-Almost all cars use four-stroke gasoline engines. One of the strokes is the compression stroke, where the engine compresses a cylinder-full of air and gas into a much smaller volume before igniting it with a spark plug. The amount of compression is called the compression ratio of the engine. A typical engine might have a compression ratio of 8-to-1. (See How Car Engines Work for details.)
The octane rating of gasoline tells you how much the fuel can be compressed before it spontaneously ignites. When gas ignites by compression rather than because of the spark from the spark plug, it causes knocking in the engine. Knocking can damage an engine, so it is not something you want to have happening. Lower-octane gas (like "regular" 87-octane gasoline) can handle the least amount of compression before igniting.
The compression ratio of your engine determines the octane rating of the gas you must use in the car. One way to increase the horsepower of an engine of a given displacement is to increase its compression ratio. So a "high-performance engine" has a higher compression ratio and requires higher-octane fuel. The advantage of a high compression ratio is that it gives your engine a higher horsepower rating for a given engine weight -- that is what makes the engine "high performance." The disadvantage is that the gasoline for your engine costs more.


-you know about the valves that let air into the engine and let exhaust out of the engine. You also know about the cam shaft that controls the valves. The camshaft uses rotating lobes that push against the valves to open and close them. This is an animation from How Car Engines Work to help understand how the cam shaft opens and closes the valves:

It turns out that there is big relationship between the way the lobes are ground on the camshaft and the way the engine performs in different RPM ranges. To understand why this is the case, imagine that we were running an engine extremely slowly - at just 10 or 20 RPMs, so it took the piston seconds to complete a cycle. It would be impossible to actually run a normal engine this slowly, but imagine that we could. We would want to grind the cam shaft so that, just as the piston starts moving downward in the intake stroke, the intake valve would open. The intake valve would close right as the piston bottoms out. Then the exhaust valve would open right as the piston bottoms out at the end of the combustion stroke and would close as the piston completes the exhaust stroke. That would work great for the engine as long as it ran at this very slow speed.
When you increase the RPMs, however, this configuration for the camshaft does not work well. If the engine is running at 4,000 RPM, the valves are opening and closing 2,000 times every minute, or 3 to 4 times every second. When the intake valve opens right at the top of the intake stroke, it turns out that the piston has a lot of trouble getting the air moving into the cylinder in the short time available (a fraction of a second). Therefore, at higher RPMs you want the intake valve to open prior to the intake stroke - actually back in the exhaust stroke - so that by the time the piston starts moving downward in the intake stroke the valve is open and air moves freely into the cylinder during the entire intake stroke. This is something of a simplification, but you get the idea. For maximum engine performance at low engine speeds the valves need to open and close differently than they do at higher engine speeds. If you put in a good low-speed camshaft it hurts the engine's performance at high speeds, and if you put in a good high-speed camshaft it hurts the engine's performance at low speeds (and in extreme cases can make it very hard to start the engine!).
It turns out that there is big relationship between the way the lobes are ground on the camshaft and the way the engine performs in different RPM ranges. To understand why this is the case, imagine that we were running an engine extremely slowly - at just 10 or 20 RPMs, so it took the piston seconds to complete a cycle. It would be impossible to actually run a normal engine this slowly, but imagine that we could. We would want to grind the cam shaft so that, just as the piston starts moving downward in the intake stroke, the intake valve would open. The intake valve would close right as the piston bottoms out. Then the exhaust valve would open right as the piston bottoms out at the end of the combustion stroke and would close as the piston completes the exhaust stroke. That would work great for the engine as long as it ran at this very slow speed.
When you increase the RPMs, however, this configuration for the camshaft does not work well. If the engine is running at 4,000 RPM, the valves are opening and closing 2,000 times every minute, or 3 to 4 times every second. When the intake valve opens right at the top of the intake stroke, it turns out that the piston has a lot of trouble getting the air moving into the cylinder in the short time available (a fraction of a second). Therefore, at higher RPMs you want the intake valve to open prior to the intake stroke - actually back in the exhaust stroke - so that by the time the piston starts moving downward in the intake stroke the valve is open and air moves freely into the cylinder during the entire intake stroke. This is something of a simplification, but you get the idea. For maximum engine performance at low engine speeds the valves need to open and close differently than they do at higher engine speeds. If you put in a good low-speed camshaft it hurts the engine's performance at high speeds, and if you put in a good high-speed camshart it hurts the engine's performance at low speeds (and in extreme cases can make it very hard to start the engine!).
VTEC (which stands for Variable Valve Timing and Lift Electronic Control) is an electronic and mechanical system in some Honda engines that allows the engine to effectively have multiple camshafts. As the engine moves into different RPM ranges, the engine's computer can activate alternate lobes on the camshaft and change the cam's timing. In this way the engine gets the best features of low-speed and high-speed camshafts in the same engine.
Hope you guys found this as enjoyable as I did, and by the way 2000 EBP Si, this isn¡¦t the fifth set of question ƒº, the first time the set of questions got posted, 4 meant FOR me and v00tecsi, you gotta pay attention to that stuff bro¡K..just playin, take it easy and have fun- peace
 

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Discussion Starter · #4 ·
Great reply, looks like I'll have to come up with something harder, lol. How Stuff Works is a great site, I've spent many a hour there.
You got me on the 'Mod Test 5', I read the 'Mod Test 4' and started this thread before I even looked for a 1, 2, or 3. Keep up the good work, Sho needs more people like you that take the time to research a answer before just posting some BS.
 

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I came across this site that had a great explanation of VTEC so here it is:

"3.What is VTEC and how does it work?"



*Lets see how DOHC VTEC works. The figure to the right shows a simplified representation of a intake-valve VTEC mechanism (the exhaust mechanisms work similarly). So for each pair of valves, there are three cam lobes. The two on the outside are low RPM lobes and the one in the middle is the high RPM lobe. The two low RPM lobes actuate the two valve rockers, which in turn pushes the valves open. The high RPM lobe actuates a follower, which is shaped like a valve rocker, but doesn't actuate any valves. The figures show the circular section of the cam lobes touching the valve rockers, and the eliptical section pointing away. Thus the valves are closed in this stage.



During low RPM operations, the two outer cam lobes directly actuates the two valve rockers. These low PRM lobes are optimized for smooth operation and low fuel consumption. The high RPM lobe actuates the follower. But since the follower isn't connected to anything, it doesn't cause anything to happen. This procss is illustrated by the figure to the right.


At high RPMs, oil pressure pushes a metal pin through the valve rockers and the follower, effectively binding the three pieces into one. And since the high RPM lobe pushes out further than the low RPM lobes, the two valve rockers now follow the the profile of the high RPM lobe. The high RPM lobe's profile is designed to open the valves open wider, and for a longer duration of time, thus allowing more fuel/air mixture to enter the cylinder. The improved breathing allows the engine to sustain its torque output as RPM rises, thus resulting in higher power output



That is basically how VTEC works. The picture to the right is a picture of an actual DOHC VTEC engine. Note that there are two cam shafts, one for the intake valves and one for the exhaust valves. For each pair of valves, notice that there are three cam lobes: two cam lobes on the outside, and one cam lobe in the middle.


*The information provided came from http://www.leecao.com/honda/vtec/dohcvtec.html

To sum it all up...

VTEC: Variable Valve Timing and Lift Electronic Control.

“VTEC is an electronic and mechanical system in some Honda engines that allows the engine to effectively have multiple camshafts. As the engine moves into different RPM ranges, the engine's computer can activate alternate lobes on the camshaft and change the cam's timing. In this way the engine gets the best features of low-speed and high-speed camshafts in the same engine.”

Basically VTEC is a system that allows the engine to act as two totally different engines all in one. When in the lower RPM range the engine operates smoothly, quietly, and fuel efficiently. However, once you reach the higher RPM range (*5500+) the engine turns into a completely different machine. It turns into a power hungry, gas guzzling race engine.




*VTEC will engage in the 99-00 Si/SiR at 5500 RPM
 

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Discussion Starter · #6 ·
Great reply v00tecsi. Now if we could only get Mike SHO to bump both of you up to moderator status I think we would have the best forum on SHO.
 

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4.Can I use synthetic oil in my engine (it only has 7000 miles on it now)? My dealership told me use normal oil until at least 30,000 miles to give the seals time to break-in, is this true? What are the advantages to using synthetic oil verse normal oil?

First lets look at the differences of Synthetic vs. Petroleum Based Oils.

"There are two primary differences between synthetic oils and conventional petroleum oils. These are the base stock or liquid that makes up the volume of the oil, and the additive package. There are additives (not to be confused with over the counter additives which will be discussed later) in all oils that enhance the wear resistance properties of the oil, enhance the ability of the oil to neutralize acids and combustion by products, and provide corrosion protection for the engine’s internal surfaces. The amount and quality of these additives vary from one oil brand to another and this is a very significant factor in the ability of an oil to adequately protect your engine in all driving conditions. As a general rule of thumb, the cheaper the oil, the fewer additives it has and therefore, the less able it is to protect your engine.

There is one school of thought that suggests that the only difference in synthetic oils vs. petroleum oils is that the synthetics typically have a better additive package. This statement is only partially true. Synthetics almost always do have superior additives than petroleum oils, hence their higher cost. However, the synthetic base stock is of paramount importance in the ability of a synthetic oil to flow at cold temperatures and withstand greater amounts of heat over significantly longer periods of time. Petroleum base stock molecules are long carbon chains that are sensitive to stress and heat. Additionally, various paraffins that are contained in all petroleum products regardless of how well refined they are, cause oil to jell like a syrup at extremely cold temperatures. High engine temperatures and heavy loads (as typically found in towing or racetrack applications) cause these chains to break down and the base stock actually boils off causing a change of viscosity and the formulation of sludge. This can happen at temperatures as low as 230º F and by 250º F many petroleum oils are suffering significant breakdown. Synthetic oils on the other hand are made engineered specifically to provide all the lubricating properties that natural oil possesses, but none of the cold thickening or hot thinning properties of petroleum oil. Synthetics are made up of uniformly shaped molecules with shorter carbon chains which are much more resistant to heat and stress. Synthetics can withstand temperatures of 290ºF all day long and still protect your engine. In fact the American Society of Testing Materials (ASTM) standard wear resistance tests are conducted at 302º F. In this test synthetic lubricants far out perform petroleum lubricants by factor of four to one and greater."


Advantages to Synthetic:

Synthetic Oils Simply Perform Better
There are five main areas where synthetic oils surpass their petroleum counterparts:

Oil drains can be extended
Vehicle life can be extended
Costly repairs can be reduced
Fuel mileage can be improved
Performance can be improved
Synthetic lubricant molecules are pure and of uniform size. This is because synthetic oils are designed from the ground up with the sole purpose of protecting your engine. Nothing is added if it does not significantly contribute to the lubricating ability of the oil. In addition, in top-quality synthetics, no component is added which is contaminated with any substance that might lessen the lubricating qualities of the oil. Not only that, synthetic oils are designed so that the molecules are of uniform size and weight. This significantly adds to the lubricating qualities of the oil.



Why Petroleum Oils are Insufficient:

Conventional petroleum oils are insufficient for use in today's vehicles primarily because they are a refined substance. Unfortunately, no refining process is perfect. Impurities will always remain when any refining process is done. Thus, there are many components of petroleum oils which are completely unnecessary for protecting your engine. They do absolutely nothing to lubricate your engine. In fact, there are even some components of petroleum oils which are actually harmful to your engine.


With that information it is safe to say that synthetic oil is safer, and better for your engine.

As far as the second part to your question...

Can I use synthetic oil in my engine (it only has 7000 miles on it now)? My dealership told me use normal oil until at least 30,000 miles to give the seals time to break-in, is this true?

The choice is up to you, Maybe that isn't the answer you are looking for. However, it is recommended by Honda that you wait 30k miles before using it, so for me to tell you "ignore Honda and use it" would be wrong of me. To be sure you engine will perform it's best I will always recommend you listen to what Honda says is the best for it.

Ok now my opinion...I know many people including myself that use synthetic oil, and did not wait until 30k miles to do so. I have never had a problem, and have yet to hear of anyone else having one.

Again the choice is yours, but I would say it’s pretty safe to start using it when your pocketbook allows you to.
 

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Another neat picture and explanation of VTEC...



Variable Valve Timing and Electronic Control. It works by adding an additional cam lobe that alters valve timing duration and lift to improve engine breathing and boost output for a smoother more powerful response. Both Honda and Acura use the VTEC system in various performance-oriented vehicles, such as the Honda Civic Si, the Honda Civic EX, the Honda Civic delSol Si and delSol VTEC, and the Honda Prelude Si and Prelude VTEC. There are variations on this sytem that include different lobe profiles on the exhaust valves as well.



Just an example of SOHC VTEC vs. SOHC Non-VTEC

Civic: DX
Type: Aluminum-Alloy In-Line 4
Displacement (cc0 1590
Horsepower @ rpm 106 @ 6200
Torque (lb.-ft. @ rpm 103 @ 4600
Compression Ratio 9.4:1
Valve Train: SOHC 16-V
Fuel System: Multi-Point Fuel Injection
Ignition System: Electronic
Final Drive Ratio (MT/AT) 4.06/4.36




Civic: EX
Type: Aluminum-Alloy In-Line 4
Displacement (cc) 1590
Horsepower @ rpm 127 @ 6600
Torque (lb.-ft. @ rpm)107 @ 5500
Compression Ratio 9.6:1
Valve Train: VTEC
Fuel System: Multi-Point Fuel Injection
Ignition System: Electronic
Final Drive Ratio (MT/AT) 4.25/4.36
 

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Discussion Starter · #11 ·
There is a funny story behind question #4. I was planning on putting Mobil 1 synthetic in the Si at her 3000 mile oil change. After checking out SHO and the Mobil 1 web site i decided to do it but I thought I had better check with the dealership and see what they say. They told me to wait until at least 30,000 miles before changing to synthetic to give the seals time to break-in. I told them the Corvette and Viper come with synthetic oil in them from the factory (along with Porsche and MB AMG among others). They told me 'the Corvette and Viper engines are much more advanced and have much tighter tolerances then your little Honda engine'. Yea right, I almost busted up laughing right there. It'll be a cool day in hell before the 'BIG THREE' could ever build a engine that will last longer, take more abuse (high RPM), or come close to the hp per liter of a Honda engine.

P.S. Dont worry about question #3, I already know the answer.

BTW, about the test Tue. morning. BRING IT ON!!! :D
 

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i have a couple of question :) not to bust you guys , just some thing that im a little confuse about . i want to turbo my civic (b16a2), but i doesnt have much experience in turboing :) all of a sudden alot of term were throw at me and im really confuse:) so here you go .

1. what is a MAP sensor and whats the different between it and an airflow meter?

2. what exactly is CLOSED LOOP?

3. how would one knows the optimum time for maximum cylinder pressure to occur and the time between the sparkplug's firing and when the maximum pressure is achieved?

thank you for answering :)
 

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I'll try and help you out with atleast one of your questions because I'm at work now and don't have too much time- Myself or V00TECSI will be on a little later to help you out with the rest of your questions & information- hope this helps for now:

The MAP sensor refers to the manifold absolute pressure sensor, a variable resistor used to monitor the difference in pressure between the intake manifold at outside atmosphere. This information is used by the engine computer to monitor engine load (vacuum drops when the engine is under load or at wide open throttle). When the engine is under load, the computer may alter spark timing and the fuel mixture to improve performance and emissions. (this is found above your intake manifold/throttle body)

Whereas the oxygen sensor is used with the feedback system to sense the presence of oxygen in the exhaust gas and signal the computer that can reference the voltage signal to an air/fuel ratio. (found on either your header, cat piping, or both, depending on the application)
 

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Discussion Starter · #14 ·
In closed loop operation the ECU uses the oxygen sensor to tell if the fuel mixture is rich or lean. However, due to the characteristics of the oxygen sensor it can’t tell exactly how rich or lean, it only knows that the mixture is richer or leaner than optimum. The ECU will enrich the mixture if the oxygen sensor shows that the mixture is lean, and lean the mixture if it looks rich. The result of this is that the mixture will swing back and forward around the stoichiometric air/fuel ratio point (14.7:1).
 

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I'm not going to lie...A friend helped me out with this..

A MAP sensor is an airflow sensor; it reads how much air is coming through.
Closed loop is where the engine, I believe has entire control over the fuel maps that usually happens at low throttle points, at higher throttle points it turns into open loop
where you can easily adjust it.

About the timing thing, I would say just get some sort of data logging device, and check for knock or timing retard.

Knock is when you’re messing up your pistons, you get pre-ignition in your engine and things begin to get damaged.

Your car if it has a knock sensor will pick this noise up and retard your timing.
Retarding the timing gives you less power but will save an engine that is getting excessive knock

With a data logger you can check to see if timing ever gets pulled, if it doesn’t then your EGT's (Exhaust Gas Temp) are low enough, and then you're golden

Welcome to tuning my friend :)

This is the point where you make or break a car, timing can turn a 13 second car into a low 12 second car
 

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v00tecsi said:
I'm not going to lie...A friend helped me out with this..

A MAP sensor is an airflow sensor; it reads how much air is coming through.
Closed loop is where the engine, I believe has entire control over the fuel maps that usually happens at low throttle points, at higher throttle points it turns into open loop
where you can easily adjust it.

About the timing thing, I would say just get soem sort of data logging device, and check for knock or timing retard.

Knock is when you’re messing up your pistons, you get pre-ignition in your engine and things begin to get damaged.

Your car if it has a knock sensor will pick this noise up and retard your timing.
Retarding the timing gives you less power but will save an engine that is getting excessive knock

With a data logger you can check to see if timing ever gets pulled, if it doesn’t then your EGT's (Exhaust Gas Temp) are low enough, and then you're golden

Welcome to tuning my friend :)

This is the point where you make or break a car, timing can turn a 13 second car into a low 12 second car
v00tecsi- damn bro- you should have just stuck with the explaination i came up with about the MAP before- it isnt just an "air" sensor, oh well
 

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myflysi said:


v00tecsi- damn bro- you should have just stuck with the explaination i came up with about the MAP before- it isnt just an "air" sensor, oh well
You covered it just fine, there was no need to go into detail twice...

Remember this is not a competition!!!
 

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2000 EBP Si said:
In closed loop operation the ECU uses the oxygen sensor to tell if the fuel mixture is rich or lean. However, due to the characteristics of the oxygen sensor it can’t tell exactly how rich or lean, it only knows that the mixture is richer or leaner than optimum. The ECU will enrich the mixture if the oxygen sensor shows that the mixture is lean, and lean the mixture if it looks rich. The result of this is that the mixture will swing back and forward around the stoichiometric air/fuel ratio point (14.7:1).
Let me make sure I understand this...

Your oxygen sensor will read your exhaust gases telling the condition of the gases, like the composition. It can't tell EXACTLY the composition, but it can tell if it’s good or bad, whether it’s too lean or too rich, but it can’t give a precise degree of richness or leanness, so it will add fuel here and take fuel away there.
Therefore the fuel ratio bounces back and forth, it tries to achieve the ideal stoichiometric fuel ratio or 14.7 parts air to every 1- part fuel.

That’s the ideal mixture to a complete combustion with maximum efficiency. Right?

Is that right? If it is wrong please correct me, I know this is a test, but I am also trying to learn.
 

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v00tecsi said:


Let me make sure I understand this...

Your oxygen sensor will read your exhaust gases telling the condition of the gases, like the composition. It can't tell EXACTLY the composition, but it can tell if it’s good or bad, whether it’s too lean or too rich, but it can’t give a precise degree of richness or leanness, so it will add fuel here and take fuel away there.
Therefore the fuel ratio bounces back and forth, it tries to achieve the ideal stoichiometric fuel ratio or 14.7 parts air to every 1- part fuel.

That’s the ideal mixture to a complete combustion with maximum efficiency. Right?

Is that right? If it is wrong please correct me, I know this is a test, but I am also trying to learn.
Do you remember any other forums where the mods were this extensively tested? This forum is being ignored and the only way anything is going to happen is if the members of the forum let mike_sho know whats up-peace:cool:
 
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