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Al
10-13-2005, 08:01 PM
A friend of mine and myself were pondering whether a custom cam can be made for a vtec engine (doesn't matter which one) with a more docile profile for the normal driving mode than what comes standard from the factory. The vtec lobe can be what it normally is or more extreme.

The purpose of this is to make the car more efficient while driving around town.

I understand that the point where the regular and high-end cam hp curves overlap, but that is what a vtec controller is for anyway.

Al
10-16-2005, 03:24 PM
No replies...

restated question:

Can a cam be reground to a lower profile?

sloLs1
10-16-2005, 05:59 PM
yes.... but anyone in there right mind would be asking why??? i see you said you wanted better city driving but a civic is most likely the best daily driver for fuel economy and engine longitivity(sp?) so i would say leave the cams alone!

1fastsol
10-16-2005, 08:10 PM
i agree with him but if you put and exhust on the car and drive normal you can save gas because the motor has less back pressure. and better oils in motor/ oil change ever 2500 miles helps. also use a fuel addtive to save gas . i have a product that i use in my 2003 cl and with out addtive i got 325 mile per tank and with 435 with it. clean valve & inj and boost octaine, + gas line antifreeze. also you can use a k & n air filter in stock intake and get better gas mileage. need more info let me know.

Al
10-17-2005, 03:14 AM
i agree with him but if you put and exhust on the car and drive normal you can save gas because the motor has less back pressure. and better oils in motor/ oil change ever 2500 miles helps. also use a fuel addtive to save gas . i have a product that i use in my 2003 cl and with out addtive i got 325 mile per tank and with 435 with it. clean valve & inj and boost octaine, + gas line antifreeze. also you can use a k & n air filter in stock intake and get better gas mileage. need more info let me know.

---------------------------------------------
I do not want to sound cocky or abnoxious by writing this, but I spend a very large amount of time crunching numbers so that I can find the answers to these issues when trial-and-error is not available.

Thank God for the TI-89!!!
http://www.thocp.net/hardware/pictures/calculators/ti_89.jpg

Err... some of that is a bit off.

Decreasing back pressure can decrease your mileage because it decreases cylinder head pressure during regular driving (partial throttle, not full) which changes the rate-of-combustion in the cylinders due to less kinetic thermal energy being available for bridging the activation-energy-gap for the actual molecular bond change. (holy run-on sentance, Batman (yes, I know))
[Chem II, Chem 343, and thermodynamics]

Typically, reducing the air resistance on the intake will cause a slight drop in the temperature of the air entering the engine. This happens because when a restrictive intake system (factory) is in place, there is a slightly greater pressure drop after the filter as well as the rest of the ducting system. When the air drops in pressure, the temperature does so too. Once cooler, the air begins to warm back to ambient pressure because the duct-work is surrounded by outside air. But shortly there-after, the air meets the throttle plate and the whole process happens all over again before entering the cylinders. The intake systems reduce overall resistance before the throttle plate so that the temp drop after the trottle plate is greater.
^ to understand this better, do not think of the air entering the engine as a whole. Consider the air by its quantitative properties, then relative properties.

EXPERIMENT: touch the manifold of a car which has been idleing for a few minutes; it will be cold, but not as cold as the air inside of it.


WARM AIR CONCEPT: the warmer air is, the faster it will react with the fuel during ignition. When this happens, the spark timing can be delayed so that more of the thermal/pressure energy from combustion can be devoted to pushing the cylinder down during the power cycle.

The advantage of the "short ram" intakes is that they breath in the warm engine bay air rather than the cooler, outside air.

EGR's work under the same circumstances. If you close off your egr, your mileage drops substancially!

High octane does not equal better mileage. The exact purpose of higher octane gas is to increase the activation energy of gasoline so that it is more stable at higher temperatures. If I was to put a higher octane gas in my car, the ingition process would be slower and less efficient. When ignition occures over a longer period of time, many new factors come about ranging from thermal losses to the cylinder wall/heads to the ignition process slowing because the volume within the cylinder is increasing at a rate greater than what would be advantagous to the ignition process.

[Detonation is breaching the activation energy requirement.]

You are right on with the injector cleaner and valve cleaner. Mixture is important and a good valve seal is too.

When it comes to oil changes, a dirty filter can really 'clog things up' (pun intended)


To my original topic, the advantage of a lower valve lift would be an increase in turbulence for the air entering the cylinder and a lessened amount of energy required to open the valve. All-together, it increases fuel economy.


For anyone who really wants to know their engines better, go and buy a chemistry book. I'm not saying to understand it word for word, but look at the pictures and try to get a good general idea of what is going on.