6th gen Honda Civic owners - Gearing Question

[hayden55]

Oh okay. I was just wondering what other people where using. So the general consensus is the less rpm the better! Iveyjh what about you? What tire size for you, sir?

[Gasoline Fumes]

185/65-14, if you're wondering what I'm using.

[hayden55]

Originally Posted by Gasoline Fumes

185/65-14, if you're wondering what I'm using.

Damn man! Do you have a thread for what is done to your car? That's some crazy numbers. lol

[Gasoline Fumes]

Originally Posted by hayden55

Damn man! Do you have a thread for what is done to your car? That's some crazy numbers. lol

I don't have one specific thread, but all my mods are listed in my garage entry.
http://ecomodder.com/forum/emgarage....vehicleid=3248

[iveyjh]

Originally Posted by hayden55

Oh okay. I was just wondering what other people where using. So the general consensus is the less rpm the better! Iveyjh what about you? What tire size for you, sir?

1998 HX 165/65/14 RE92

2000 Saturn SL1 RE92

2000 Metro 145/65/15 4" rims Continental Eco

[hayden55]

Looking like I'll end up with this:

3.25 Final Drive trans w/ Michelin Defender 185/70/14's.

Should drop my hwy rpm from 2960 to 2219 at 70mph. Is that considered a little under geared or just fine? Drive is for the most part literally 100% flat.

I guess if I run the numbers lets see what 4th would end up at versus the original setup. . .

.909 (LX Trans) vs .853 (CX Trans)
So 70mph on the CX trans w/ new wheels would be 2696rpm.

Now that I ran the numbers that setup is looking really good.

[hayden55]

Looking like I'll end up with this:

3.25 Final Drive trans w/ Michelin Defender 185/70/14's.

Should drop my hwy rpm from 2960 to 2219 at 70mph. Is that considered a little under geared or just fine? Drive is for the most part literally 100% flat.

I guess if I run the numbers lets see what 4th would end up at versus the original setup. . .

.909 (LX Trans) vs .853 (CX Trans)
So 70mph on the CX trans w/ new wheels would be 2696rpm.

Now that I ran the numbers that setup is looking really good.

What number's are y'all seeing on the interstate at 70mph with the AC on *1*?

[Xist]

Can someone tell me how much of a load the vent has on one, compared to the other settings? I imagine it makes a difference, but small.

While adjusting the numbers makes the cabin cooler or warmer, as far as I know, the AC is working just as hard.

I cannot drive 70 while using my AC with my current grill block, but it is 116° here in Phoenix.

Yeah, I opened my windows...

[mwilliamshs]

Originally Posted by Xist

Can someone tell me how much of a load the vent has on one, compared to the other settings? I imagine it makes a difference, but small.

While adjusting the numbers makes the cabin cooler or warmer, as far as I know, the AC is working just as hard.

I cannot drive 70 while using my AC with my current grill block, but it is 116° here in Phoenix.

Yeah, I opened my windows...

I don't know anything about the AC control logic on these cars specifically, but generally, the AC compressor cycles between high and low pressure cutoff switches any time the AC button on the dash is engaged and thermostat is not satisfied and calls for cooling. It's job is to pressurize the refrigerant as needed so it condenses and can then evaporate so that need varies with thermostat position which varies its duty cycle. The evaporation rate is controlled by an expansion valve on older systems that varies the evaporator input flow rate based on the evaporator core temperature. Ideally, they open as much as possible without causing freezing. Newer systems use an orifice tube which has a fixed flow rate designed to never freeze and their sizes vary with some vehicles having multiple options to balance economy and cooling capacity.

If you're going to use the AC, in my experience the most efficient use of AC is to set the fan speed on high, set the vent for recirculate, and set the temperature as warm as you comfortably can. This will cycle the compressor as little as possible thanks to the high thermostat setting and will keep you as comfortable as possible thanks to the cooling effect of the fast moving high volume of air and will require less work to cool the same air over and over (which will gradually get colder and colder and drier and drier) than would cooling a new volume of hot, humid air constantly. Remember, the electric blower motor is more efficient to spin faster than the compressor is, so set it high to allow running the compressor less. Also keep in mind the blower motor speed control is a simple resistor circuit so any power you're not using to spin the fan is wasted on heating resistors. No real electrical gain to be had by setting the fan to 3 instead of 4, etc but the cooling efficiency of the AC varies directly with airflow.

Diverting coolant away from the heater core saves fuel too. It allows faster warm-ups thanks to the smaller volume of coolant absorbing heat and reduced heat loss thanks to the smaller volume of coolant and the reduced surface area of the cooling system thanks to removing the heater core itself from the loop. This also allows the AC to be more efficient and you to be more comfortable because the discharge air is not being cooled by the evaporator then heated by the heater core then blown onto you. I tested this last night in a new to me 98 Civic LX by turning the AC off and gradually setting the thermostat warmer and warmer until the air got warmer than ambient, then sliding it back just enough to back to achieve ambient discharge and turning the AC back on. I couldn't move the thermostat much at all before I started getting heated air but the compressor would still be running, and running more than really needed to keep me comfortable. I'll bypass the core as soon as I confirm whether or not that loop is required for proper coolant flow so I know whether I should couple the heater hoses together or block them entirely.

[mwilliamshs]

A thread about gearing options should include tire options in my opinion. Being new to the Honda thing and new to wheels smaller than 15" in general, I'm ignorant of what sizes are available to fit my 98 Civic. Here's what I do know: for best efficiency a narrow tire is better than a wider one and a taller tire is better than a shorter one. Obviously a tire so tall it raises the vehicle and allows excess air under the vehicle would be bad and a tire so tall it moves the engine out of its best rpm range at cruise speed would be bad and a tire so tall it is excessively heavy would be bad. Also keep in mind tire diameter changes will alter speedometer and odometer readings as well as those of a scangauge, etc.

All that being said, my 98 Civic's OE tire size is 185/65-14. A better option in my opinion is 175/70-14. For simplicity's sake I'll discuss only Michelin Defender tires because they're available in both sizes and the only other I've found in both sizes is a T-rated General that I wouldn't buy. The 175 is .3" taller and .4" narrower in section and has tread .5" narrower. The 175/70-14 being a bit taller means fewer revolutions per mile (difference of 9, insignifigant IMO) which means longer tire life and reduced rpm/mph - both good things. The 1/2" reduction in tread width means less rolling resistance and reduced wind resistance, again, both good things. Negatives to this swap would be increased ride height (less than a quarter inch) and reduced traction available due to the narrower tread width but in reality, an ecomodder isn't likely to drive their car to the limits of traction anyway. Weights for this particular tire in both sizes is listed as the same but most others are lighter in 175, to the tune of 2 lbs or so less per tire.

Side note: the Defenders are Green X rated for LRR but weigh 19lbs. The Hankook OPTIMO H724 (first other tire I clicked on) weighs only 15 lbs. Would you rather have LRR or less weight?