Performance at Altitude

[Carimbo]

Just had the first experience of driving the Maxima at altitude this week. Attended a seminar in Leavenworth, WA and crossed Snoqualmie Pass (Elevation: 3022 ft./921 m.) and Blewett Pass (Elevation: 4102 ft./1250 m) to get there. Beautiful trip this time of year, and the car made the 300 mi. RT w/o any bad suprises.

Realizing these elevations are not as high as some regularly traverse, but the car did have quite some trouble maintining speed and temp getting over the top. Could not even keep up w/ the loaded semis trundling up the slowslow lane.

If I understand the function of the altitude compensator, it is primarily to reduce emissions and not to help performance at altitude.

FSM states to change EGR guide tube and adjust IP timing (advance) for high-altitude driving.

Planning to do more mountain trips this summer; would these modifications be worthwhile? Guessing the side effects would be reduced performance at sea level. Is a turbocharger the only real solution?

[asavage]

I took my '82 Wagon across I-90 to Spokane about eight years ago. I had no problem keeping up with traffic, but I did generate a lot of smoke. I was in the fast lane. No tailgaters.

[goglio704]

Never driven a Maxima at altitude. I did drive an Olds diesel at altitude on occasion. Power might have been a little off, and the smoke was gruesome. Forced aspiration is a beautiful thing.

[1982810maximadiesel]

My Maxima seems to run great in all situations It does smoke when pressed hard. Altitude runs two weeks ago in the Smokys up by North Carolina were a breeze.On long hard grades I can get 55mph to 65mph There are two good torque bands out of my expierience driving in the mountains 75mph and over will not drop under that, if droped under it falls into the 55mph torque band. 5 speed manual. I do have a mandrel bent 2.5 inch exhaust system and a KNN filter and a tornado in the intake.I have a great diesel Mechanic that has tuned my vehicle to run great.It has more power and top end then my other Maxima gasser.Its incredible.The engine sound at highway speeds is awesome.Exhaust sounds like 400mph winds.
I run my max hard all the time,maybe my engine is cleaner then most. After all the well proven years with this vehicle....You cannot kill it regardless on how hard you push it.I do maintain it with the best oils and fluids.
And I am never cheap with it.Why? because it good to me.

[83_maxima]

I have a great diesel Mechanic that has tuned my vehicle to run great.

What has your mechanic done to "tune" your diesel Maxi? I am quite curious.

[1982810maximadiesel]

Advance the timing to the maximum point where it is safe. Also there is a screw on the injection pump where you can play with the mixture. Drive it as much as you can and the more you do that the better they run. Syntetic oil and proper maintainence.

[1982810maximadiesel]

279.000 miles and running like new They dont make them like they used to.DATSUN making a name for Nissans.that why they are great.

[goglio704]

Carimbo: YOU fix it. Look at the top, far right end box of top "Edit". Fix your mess.

Carimbo: WHY is this FIRST post forum 3 FEET wide?? IE and FireFox show this.

It wasn't like that when I started this one. Let's see what happened....

.....Looks like there is a 3-foot long unbroken URL showing up in the 9th post.

If someone could edit that it might fix it.

(Later) Should those photos referenced (URL links actually) even be here? Seems like material for the User's Rigs forum.

Not his mess to fix. He didn't post the item that made this thread three feet wide and he doesn't have moderator privileges. The first post doesn't dictate width. The widest one does.

[philip]

Not his mess to fix. He didn't post the item that made this thread three feet wide and he doesn't have moderator privileges. The first post doesn't dictate width. The widest one does.

Looks great now.

[rlaggren]

Through a really stupid navigation error I crossed over a pass 11,900' in CO. last Monday. OK up to about (I estimate) 7000-8000, after that I got slow and at the top very slow. The last 1000 feet were alternating 1st & 2nd gear between 12 & 25 mph indicated; the large tires I have on the rear add another 13.5% to that; I don't know if I could have maintained 2nd if I had regular tire size or not. Payload including me was about 550#, maybe a little more.

Engine temp rose to about 5/8 gauge and stayed there. Smelled hot tranny oil the last couple miles, but color looks good and no big drips anywhere. But in the last 1/2 mile the tranny refused to shift into 1st, even down to about 8mph; fortunately I was close and 2nd took me to the top. After sitting a few minutes while I took a walk and enjoyed the scenery, the car started and ran and shifted normally. Drove on to San Francisco with no particular issues.

Definitely lose power up there, but the care _will_ make it over. If I had more weight, I'd probably have to stay in 1st from about 9000' or so. Which might actually be easier on the car. No obvious bad smoke, though I was mostly watching forward and could only see out the side mirrors.

Cheers, Rufus

[240ZD]

When driving west on I90 over the continental divide area, I could maintain speeds of 65+ easily with only some increased smoke and somewhat elevated engine temp., even though it was a super hot summer day. It was comical to blast past, at arrogant speeds, countless laboring and overheating vehicles and semis. Only turbodiesel pickups could hang.

Like 1982810maximadiesel my only engine mods are a nice air filter and fat free-flow exhaust. It really helps to open up the LD28 airways and jettison extra weight....


...but of course the only real solution is available at your friendly neighborhood turbo supply depot.

[rlaggren]

I travel I-80 every year and last year I crossed (east from Ca. to Chicago) on I-90. These main roads seem to be graded mostly below 5% and never over 7%. The back road I took had steeper grades. I'm going to look for and inclinometer - see if I can find something easily readable and somewhat cheap. But an outside temperature gauge come first.

The tallest main highway grades (7% about) make me run in 2nd to maintain an indicated 55. It'll down shift at 55-58 but because of the OD it won't hold it on a long grade. There are about 10 places on I-80 where I need 2nd to maintain. One of these days I'll keep a trip log and remember where to decent eateries and long grades are!

If I could cancel the OD I think 3rd would hold about 55-60 or so. But the OD is probably easier on the tranny temperatures as long as there are enough revs to keep the line pressure up; I'm assuming that the converter requires a a certain minimum line pressure to lock up against maximum load.

The wagon weighs about 700# more than an early Z as I recall, so you'll get a lot better performance than the maxi's.

Rufus