GX power and steep grades

[mecklen]

I wasn't sure whether to post this to the Utah group or here...

I'm wondering about people's experience and advice about driving up steep grades in a GX. I have an '07 GX and drove it from Salt Lake to Park City this weekend. Going up the long steep grade to Parleys Summit, the GX required serious nursing.

The car had four passengers (2 adults, 2 children, ~400 lbs) and could not maintain 65 mph. It dropped into a lower gear and I finally settled on 52-55 mph. When I tried to maintain 55 mph, it would shift to a higher gear ~3500 rpm, then have insufficient power so we would slow down, then drop to a lower gear ~4000rpm, speed back up to 57, then shift to higher gear again. We cycled like that a few times until we reached the summit.

BTW, I have also tried running it up to 75mph before the grade (moving to a different part of the power curve), but that makes no significant difference.

Has anyone else driven this section of road? What about the Grapevine into L.A.? Any opinions on running the engine hard at 4000 rpm?

Thanks,

[jetboatjohnny]

Re: GX power and steep grades

I am not familiar with that grade, but I can make it up the 15 grade from San Bernardino to Victorville no problem at 75. I also drive up the grade on the 241 tollroad which is very steep at 75, but in 3rd gear and high RPMs for sure, no tach, but I am sure it's well above 4,000.

[mecklen]

Re: GX power and steep grades

I am sure it's well above 4,000.

So, obviously, you aren't concerned about running at high rpms? I tend to be much more cautious, but have no information to base my caution upon.

[jetboatjohnny]

Re: GX power and steep grades

I guess it depends how fast you want to get where you are going. I have no worries about revving my little engine up. It wont go past redline, so I dont think it will blow up. I'm sure it uses a lot of fuel also.

[Curtis]

Re: GX power and steep grades

I have gone over the Cajon and Tejon pass'. Both are long and steep. I have no problem holding speed at 72-78mph. My '04 has a CVT and will run up to 4000, even 5000 rpm to hold speed. Honda's are high revving engines and develope their power in ranges that would nuke an american car. With a red line at about 7200 rpm, this won't harm the engine, but as Johnny indicates... this isn't the most fuel efficient range to run in.

The 5 speed tranny in the new body style has a feature called grade logic control. Theoretically, it watches brake and accelerator usage to determine whether you're going up, or even down, a steep grade and can downshift up to 2 gears to eliminate gear hunting or excessive breaking. I have not observed this to be particularly effective and have found that dropping the shifter into 3rd until I regain speed, then placing it back in 5th, will sometimes cause the grade-logic to hold the car in lower gear ranges.

Try dropping your shifter to D3 to hold speed. You would find it a bit easier if you weren't loaded down, so if the speed drops too much, have the wife and kids get out and push. Just kidding... the wife should be able to handle it on her own.

[PaulH]

Re: GX power and steep grades

Curtis,

Do you find that the AC compressor stays engaged while going up the Tejon grade at 70ish mph? Enough to keep the car cool on hot days?

Paul

[freedml]

Re: GX power and steep grades

The ac barely keeps the car cool on level ground...

[mecklen]

Re: GX power and steep grades

The ac barely keeps the car cool on level ground...

Really? My '07 GX seems to have perfectly reasonable A/C. The other day it was 100F and I got cool air out of the vents in less than a minute. In 5 minutes the car was comfortable. I even commute up steep grades and don't see any warming from the vents on these.

[freedml]

Re: GX power and steep grades

I would say our 2001 and 2002 GX take 20 minutes to cool the car at high on a hot day. We just bought a bifuel 2003 Cavalier and the AC cools the car in 5 minutes set on medium. And the Cav is dark exterior/interior while the Hondas are lighter interior and white and silver exteriors.

[PaulH]

Re: GX power and steep grades

I should have clarified my question. I was asking about the '06 - '08 Civic GXs.

[dbiskup]

Re: GX power and steep grades

My impression of the AC cutout on my 2008 GX is like this:

The AC compressor cuts out when accelerating from a stopsign or a traffic
light. This is quite noticable if you just got into a hot car. But when climbing
a long grade, it seems to come back on after a few seconds and get back to
cooling the car, even though you are deep on the gas pedal. (I like calling it
the "gas" pedal )

[jdbitton]

Re: GX power and steep grades

I had the same experience in the same canyon in my 00 Civic GX, and in my previous 4 cyl car, so it's not the fuel, it's the more than likely a combination of the altitude and heat.

[Curtis]

Re: GX power and steep grades

Curtis,

Do you find that the AC compressor stays engaged while going up the Tejon grade at 70ish mph? Enough to keep the car cool on hot days?

Paul

I do notice that it drops out for a bit under acceleration, but long steady grades don't seem to be a problem in my '04. Many times I have to turn it down, or even off, because it freezes me out of the car. I have been experimenting with turning it off on uphill grades and back on fot the downhill side since I seem to have a vry noteable drop in mileage with the AC running. It will continue to blow cool air for several minutes when I hit the AC button to off (leaving recirculate on). Any of you experimented with this?

[ajgiorgi]

Re: GX power and steep grades

Theres no power, that's the problem. 100hp in my 99 sucks. I drove up to Lake Tahoe on 80 and I was going back and forth between gears. I finally just settled on down shifting into third and holding it at 50mph. I'm waiting for that turbo kit............................ any day now.

[Michael]

Re: GX power and steep grades

I have a 2006 GX. I like the five-speed automatic, except that I wish the shifter would have been designed with another position that would have allowed me to choose and keep 4th gear. This would come in handy especially on some freeway downhills, such as the grapevine, northbound.

My experience with the grade logic control is that it does too much gear shifting (hunting) when attempting to find the right gear for a particular grade. This is especially true when using the cruise control.

Often, the best solution is to put the shifter in D3 for the steep hills. The RPMs are high, but not near the red line, there is plenty of power (about half of the pedal travel still left while going uphill on the grapevine at 65 mph, the posted speed limit there), but I'm sure it uses a lot of fuel.

Keep in mind when comparing the grapevine to Utah, there is substantial difference in altitude. The grapevine elevations are between about 300 ft. and 4100 ft. Salt Lake City is at about 4200 ft., and Park City, UT is at about 7000 ft. With no turbo charger, the higher altitudes are going to be tougher.