[Drummin335i]

So I am moving to 9,000 feet elevation, coming from about 500 ft at sea level. What should I do to get my N54 ready for the change? What tunes would you recommend for a mostly stock motor, but to account power difference due to elevation change?

Just looking for some quick insight and thoughts right now. I've searched past "high elevation" threads, but most were aimed at Denver area at about 5,500 to 6,500 feet.

[TBN54]

Sell the car and get a jet pack.

[mxchris727]

All cars today have atmospheric pressure sensors built onto the DME or MAF to compensate for elevation changes. The car is fine, but you may notice a slight decrease in gas mileage.

[BQTuning]

Originally Posted by mxchris727

All cars today have atmospheric pressure sensors built onto the DME or MAF to compensate for elevation changes. The car is fine, but you may notice a slight decrease in gas mileage.

True, but have you ever seen what duty cycle looks like on a car running at that high of elevation ?

[V8bait]

Originally Posted by Drummin335i

So I am moving to 9,000 feet elevation, coming from about 500 ft at sea level. What should I do to get my N54 ready for the change? What tunes would you recommend for a mostly stock motor, but to account power difference due to elevation change?

Just looking for some quick insight and thoughts right now. I've searched past "high elevation" threads, but most were aimed at Denver area at about 5,500 to 6,500 feet.

Over 9k feet everything gets ugly. WGDC gets high and boost is laggy and often under target, iat goes up due to the turbos working harder and the intercooler working less efficiently, and the octane of gas is generally lower, sometimes 87 and 90 are the best octane you can find. Your best bet is to go fbo (catless, inlets, nice stacked fmic with lots of surface area) to make the car as efficient as possible at lower boost. You at least absolutely need a good FMIC. If you use a piggyback, this is the only instance I'd actually advocate for removing it (even though I like MHD more these days anyway)- the jb4 was very inconsistent at higher altitude for me. And by higher I mean 9-12k feet, in Denver it was fine.

[GODDSPD]

Altitude sucks. I'm only at 4,000 feet and can barely hold 15 psi at 6,000 rpm... and that's with inlets! Back in California 18 psi was no issue with stock inlets.

Although you will notice your fuel pumps do very well (less air=less fuel). You can run a lot more e85.

[adidoman]

Air pressure and oxygen drastically decrease the higher you go up in altitude, making the amount of power way less. A turbo car is still going to be a better bet that high up as N/A cars will be very weak that high up. If you are stock, your car will adjust to the conditions, but it's going to take a loss in power. If you are worried or want more power, get a custom tune to compensate, a larger step intercooler, downpipes to reduce the stress on the turbos and to get the power back up

[adidoman]

Also maybe make a post in the Rockies/Midwest section and see if someone has personal experience with that high up. I'm just shy of 6,000 and I know people here in Denver have gone to the track when the DA has been close to 9,000 at Bandimere

[YoungBlood]

Where tf are you living? Everest?? I thought Utah with our 4500 elevation was bad! I don't know any different, never lived at sea level, but boost is still better than NA at this altitude

[extreme-eg]

Originally Posted by V8bait

Over 9k feet everything gets ugly. WGDC gets high and boost is laggy and often under target, iat goes up due to the turbos working harder and the intercooler working less efficiently, and the octane of gas is generally lower, sometimes 87 and 90 are the best octane you can find. Your best bet is to go fbo (catless, inlets, nice stacked fmic with lots of surface area) to make the car as efficient as possible at lower boost. You at least absolutely need a good FMIC. If you use a piggyback, this is the only instance I'd actually advocate for removing it (even though I like MHD more these days anyway)- the jb4 was very inconsistent at higher altitude for me. And by higher I mean 9-12k feet, in Denver it was fine.

This post covers everything you should know, its good advice. To add to this I'd run the new V6.1 MHD maps which runs less boost but more ign advance. As mentioned go for the least restrictive exhaust system you can get away with (Downpipes are key), reduction in backpressure helps the turbos efficiency and spool as the pressure differential across the turbine wheel is greater.

This is a better method of tuning, particularly for super high elevation as high boost pressure can easily overspeed the turbo (even large aftermarket performance turbochargers) and cause them to fail and self-destruct.

I'm at an elevation similar to Denver (5500ft) but our DA goes to like 9000 on average with the atmospheric conditions present.

[ajsalida]

Originally Posted by V8bait

Over 9k feet everything gets ugly. WGDC gets high and boost is laggy and often under target, iat goes up due to the turbos working harder and the intercooler working less efficiently, and the octane of gas is generally lower, sometimes 87 and 90 are the best octane you can find. Your best bet is to go fbo (catless, inlets, nice stacked fmic with lots of surface area) to make the car as efficient as possible at lower boost. You at least absolutely need a good FMIC. If you use a piggyback, this is the only instance I'd actually advocate for removing it (even though I like MHD more these days anyway)- the jb4 was very inconsistent at higher altitude for me. And by higher I mean 9-12k feet, in Denver it was fine.

I live at 7800 ft and do most of my driving above that, 12k routinely over passes. Agree with most of this except the JB4 part. Have had no issues with mine and the latest firmware is pretty good compared to long ago versions.

My car is FBO + meth + BMS backend race flash. Meth is for cooling and octane, so I run 50/50 mix water/meth, as mentioned we have only 91 octane and no e85 nearby. This is SW Colorado, San Juan mountains.

The main issue is heat. You can't radiate it efficiently at altitude, and you have to create more of it to hit decent boost due to pressure ratios. I have an oil cooler on the car and 7" FMIC. Example: Sea level you're at say 14.7 PSI ambient. Near my house it is 10 PSI. In order to get the same amount of air mass as a car at sea level running 15.3 PSI of boost (30 absolute) you need to run 20 PSI of boost. Sea level pressure ratio is close to 2, well within spec and efficiency, but at altitude more like 3, which is off the charts. This sucks, generates tons of heat, req massive WGDC, lag, etc.

To get same air mass as a sea level car running 20 PSI of boost (34.7 absolute) you need to run 24.7 PSI of boost at this altitude, which is just absurd as far as pressure ratios.

I keep going back and forth as far as getting a big single.

PM me if you have questions. I have never really run this car at any lower altitude, been up here tweaking it for 6 years now. It is XI + AT.

Having said this, the opportunities to run WOT in situations where you can safely say, do a full log, are rare. Due to the fact that it is the mountains after all, windy roads, steep drop-offs, instant death awaits anything profoundly stupid. Put another way, you are not going to be running WOT over the top of Wolf Creek or Red Mountain pass, say, or any of the passes or roads leading up to them. Not going to happen. What is more likely is you'll have to drop down to say 7k ft and find long stretches of empty roads in the flats, empty of cops, animals, and other cars. Do some logs and tuning, and then from time to time do short blasts at elevation. But even those generate a ton of heat, esp mini ones done while ascending up steep grades to get over passes.

You may find you switch focus to tuning suspensions with all the windy roads.

edit: one more thing, brakes. The heat dissipation things affects brakes too. I'm not saying you need some BBK, but steep downhill sections, aggressive/inattentive driving, will cook your brakes much faster than you'd expect. Every year up here we lose a few truckers and RV trailer-towing types. As in they lose brakes in a critical section and they die. So for me this means I seldom get racy going down hill, or if I do it's dialed way back.

[shushikiary]

Yes, in my car it runs 100% WGDC to maintain 13 PSI at 6500 RPM in denver, its even worse at altitude, and that's FBO with inlets on E-85. I even had to tighten up the PID to get it to be accurate, in my opinion.

Brakes, I agree with the heating issues, once you have a fast car, braking from 140 to 60 even 3 times in a row within 5 minutes can cause some serious heating issues. I run 255's all around as it really helps with the braking (and removes the silly understeer the car has stock. )

On hot days with the sun beating down I'm very lucky to run at idle with the IAT's under 100 deg F with a VRSF stepped 5 inch. I even put a heat blanket under the hood to separate the BMS intake from the rest of the engine bay and put scoops in to get as much air to them as possible from out side and that helped a lot.

[ajsalida]

The thing is heat is an issue even when ambient temp is low and low loads. I ran some logs a couple of years ago, running up the grade from about 8500 to 12k ft going up Wolf Creek pass. About 8 miles. Ambient temp at the bottom was like 70 deg F, at the top 50 or so. My house is about 15 miles from the start of the big grade so everything was warmed up to steady state temps by start of climb.

Going the speed limit and no hard accel at all, at the bottom flat or very slight grade, @ 65MPH IAT's were very close to ambient. At the top, well over 100 deg F doing 45 MPH. So even low loads for prolonged time up here, no stoplights constant speed you're heating way up. Oil temps were close to 250 but not over. Never into boost at all, not even close.

This was with an ETS 5" FMIC and Cobb Stage 2+ tune, no meth. At this point I decided to go for a 7" VRSF FMIC + JB4 + meth. It did not eliminate the temp rise in similar conditions, what it did was get things back down to reasonable IAT faster, and then the meth kept things safer under WOT conditions. IAT's drop like a rock back down to ambient once the meth is flowing.

[Drummin335i]

Great information everyone! At this point, I'm perfectly fine with stock boost. I'm thinking MHD/JB4 on like a Map 1 would be fine. Do you think WGDC will be too high?

I may go with a bigger FMIC and downpipes in the near future. Average ambient air temps will range from 30 F to 65/70 F peak summer time. I'm hoping the lower air temps will help compensate for high IATs. Note, I am coming from Texas heat where ambient temp is normally 90-100F in the summer. I doubt I will ever see over 75 F at 9000 ft elevation, but maybe when I head down towards Denver and elevations are lower. What are your thoughts on this?

93 octane is normal for me here in TX. I don't understand why higher octanes are not available up in the mountains. Aren't those the areas that actually need the higher octanes? 91 should be fine though.

Originally Posted by YoungBlood

Where tf are you living? Everest?? I thought Utah with our 4500 elevation was bad! I don't know any different, never lived at sea level, but boost is still better than NA at this altitude

High Rockies, west of Denver.

Originally Posted by YoungBlood

Having said this, the opportunities to run WOT in situations where you can safely say, do a full log, are rare. Due to the fact that it is the mountains after all, windy roads, steep drop-offs, instant death awaits anything profoundly stupid. Put another way, you are not going to be running WOT over the top of Wolf Creek or Red Mountain pass, say, or any of the passes or roads leading up to them. Not going to happen. What is more likely is you'll have to drop down to say 7k ft and find long stretches of empty roads in the flats, empty of cops, animals, and other cars. Do some logs and tuning, and then from time to time do short blasts at elevation. But even those generate a ton of heat, esp mini ones done while ascending up steep grades to get over passes.

You may find you switch focus to tuning suspensions with all the windy roads.

edit: one more thing, brakes. The heat dissipation things affects brakes too. I'm not saying you need some BBK, but steep downhill sections, aggressive/inattentive driving, will cook your brakes much faster than you'd expect. Every year up here we lose a few truckers and RV trailer-towing types. As in they lose brakes in a critical section and they die. So for me this means I seldom get racy going down hill, or if I do it's dialed way back.

Good points! Any certain brake pads / rotors recommended for better heat dissipation over others?

Originally Posted by ajsalida

To get same air mass as a sea level car running 20 PSI of boost (34.7 absolute) you need to run 24.7 PSI of boost at this altitude, which is just absurd as far as pressure ratios.

I am factory boost at about 500 above sea level currently. What boost should I target at 9000 ft elevation? I'm hoping map 1 / 13.5psi will be enough.

Maybe I am just overthinking the altitude change? I'd like to keep my current power level at least.

[Drummin335i]

Didn't know what DA was so I found some good info on density altitude. Looks like I may be more at 10,500 DA when I input average temp, pressure, and humidity. Damn.

http://www.corvetteforum.com/forums/...alculator.html

[GODDSPD]

Question- Since we are all gathered here, those in high altitude, let's post up your max boost at 6k rpm with 100% WGDC. I'm thought I may have a boost leak originally but after reading this thread it doesn't look like I'm far off.

Ill start...

Mods- FBO with inlets and outlets
Altitude- 4,500 ft
Max boost at 6k rpm- 15-16 psi

[V8bait]

You're right high altitude and turbos means you really need octane more than in Texas, but that's not how things work. High altitude on naturally aspirated cars means you're loading the engine less, so you have less power and less propensity to knock. So they only offer lower octane since historically that's all that existed on the roads, turbos are a more recent thing outside of diesels, and performance isn't something focused on. In the mountains, lots of times you cannot even find premium, it depends on where you will be living. Lower than 91 octane is fairly common in parts of the Rockies, but if you're close to the ski resorts or Denver 91 *should* be available.

At 6,000rpm at in Colorado Springs/Pueblo you should be able to make 15psi with around 75-80% wgdc in third, maybe a little more in 4th. 100% WGDC might get you another psi but after 80% it's not very useful imo.

[GODDSPD]

Originally Posted by V8bait

You're right high altitude and turbos means you really need octane more than in Texas, but that's not how things work. High altitude on naturally aspirated cars means you're loading the engine less, so you have less power and less propensity to knock. So they only offer lower octane since historically that's all that existed on the roads, turbos are a more recent thing outside of diesels, and performance isn't something focused on. In the mountains, lots of times you cannot even find premium, it depends on where you will be living. Lower than 91 octane is fairly common in parts of the Rockies, but if you're close to the ski resorts or Denver 91 *should* be available.

At 6,000rpm at in Colorado Springs/Pueblo you should be able to make 15psi with around 75-80% wgdc in third, maybe a little more in 4th. 100% WGDC might get you another psi but after 80% it's not very useful imo.

Is that estimate with or without inlets?

[shushikiary]

It really depends on temperature too.

100% WGDC at 6500 RPM on a 90 deg day nets 13 PSI with inlets and DP's on E85 tune in 4th gear.

When its 50 deg out same otherwise I can hold 14. If it gets down to 40 or below I can hold 15. Below 30 and it will hold 16. So the real question is the DA.

Here's an example of what the curve looks like in 4th gear for what I'm talking about.
http://datazap.me/u/shushikiary/de99...-21-31&solo=31

[V8bait]

Originally Posted by GODDSPD

Is that estimate with or without inlets?

Honestly, don't get caught up on the psi. It will vary with conditions. The turbos will likely be maxed and the airflow will be what it is.

[Vincent_E90]

I moved from sea level to 6700 ft el this winter, Never really changed anything for the elevation, just the extreme weather you get when living in that high of elevation.

[adidoman]

Get yourself a really good set of winter tires. It will be snowing for around half the year that high up