I'm planning to have my Evo X MR tuned on a trip to California later this month at Road Race Engineering. The only thing I'm worried about is that I live at 5,000 ft altitude and road race is close to sea level. Will the new tune in the ECU be able to compensate correctly for the altitude difference when I get back home? Is it still worth paying for hours of dyno/tuner time only to spend all my time driving under different conditions?

The pressure at 5,000ft is 17% less than the pressure at sea level. I figured that this would just make my tune a little more safe, but am wondering if I will lose performance (above and beyond the effect of having less air).

Also, I've heard horrible things about California's pump gas. Will be tune be significantly thrown off when I return to higher quality gas back at home?

I've searched and couldn't find anything answering my questions, but if you know of anything, please post a link.

Thanks for all the help!

 

California 91? It's basically ****.

 

I'm not sure if the ecu can adjust for the elevation difference. But i can key in on your fuel issue, currently am in portland, OR and will be going to English Racing this Tuesday for a tune. I drove down from Vancouver, BC. Our canadian 94 oct is similar to California's 91 oct, it sucks. Luckily for me, i am able to fill up with US 92 oct since i live so close to the border. I decided to get a dual map tune, US 92 oct and CAN 94 oct. I brought down some of the canadian 94 oct in a couple jerry cans so i can get tuned on it as well. I would suggest bringing some of your local gas down for the tune and possibly getting tuned on the Cali gas so you can have a worry free drive home.

 

Why don't you get tuned here in CO? I don't think our 91 is that much better than CA's. I haven't read anything about it however. The generally concensus is that the 91 sucks here too.

Also, I think you'd need a retune if you want to get the most out of your car and to keep it reliable.

I believe you'll lose about 15-20% of power due to elevation. It would be awesome if you could do a VD now and one when you get to sea level with your current tune now. Also do a VD after your dyno tune to see how close it is and also do another VD when you get back here.

Just look at a timing map and let's say in CA you hit 350 load at peak load, but here in CO you hit 280 load at peak load, you'll have a higher timing in that load cell at altitude (generally).

 

Two maps is probably a good idea. I've worried about the same problems going from one state to another.


Ideally, I would get a tune in CO or NM (where I'm currently living). I just haven't found anyone with as much experience as Road Race...

I think comparing the parameters would be a good idea. There is a lot of change between driving around here and in CA. I just can't figure out if the maps that are tuned in the ECU will compensate correctly for the altitude difference...

For example, if a turbo is operating with a compressor ratio for 2.0 here (where the atmospheric pressure is 12.2 PSIa) then you get a pressure of 24.4 PSIa in your intake manifold. This equals 12.2 PSI of boost. However, operating at 2.0 in CA (where atmospheric pressure is 14.7 PSIa), you get a pressure of 29.4 PSIa equivalent to 14.7 PSI of boost (PSIg). As a result, same pressure ratio but different boost pressures... I don't know. Just thinking out loud.

 

The factory Baro. sensor (inside the ECU) is there specifically to compensate for air density (elevation) differences. Because manufacturers have no idea or control over where their cars are driven, they must have the ability to compensate for all conditions. The baro. sensor is constantly running (multiplying) in the background making global fuel trims unless your tuner chooses to ignore or "turn off" it's signal.

If the OEM fuel strategy is retained (tuners use all kinds of different strategies), and the fuel map is correct, you should be able to drive from Pikes Peak on a 100 deg. day to NY, NY on a -20 deg. day without issue.

 

And remember the air at 5000 ft. is less dense than at sea level. So you may want to think about possible lean conditions under full boost if you tune for sea level.

 

Ummm no.
Read your first sentance again.
Less air density = less oxygen content.
Less oxygen = less fuel required.
Less fuel = less HP.

The car would go richer & richer as you went up in elevation (without Baro. comp.).

 

you will want to watch your boost levels too. I was tuned in CO and drove to AZ and when getting back on the HWY my boost levels were off from when I tuned. But like stated before the ECU accounts for barometric pressure. There are plenty of great tuners in the CO area. If you are in the Springs area, Randy (NukeRJ on Evo X Forums) or Supernet are both capable. I can give you both of their contact info if you are intersted.

 

I beg to differ. Without going into a mechanical dissertation, do yourself a favor and watch a Pike's Peak Annual Auto Race. The factory back cars costing $100k to $300k start at the base of the mountain @5000 ft. and go to the summit at @12,000 feet.
When Rod Millen raced his Toyota GTP Pickup with the IMSA 4 cylinder engine making @1000 hp at the base. He said acceleration started tailing off near the summit to @750-800 hp-data logged supported. Thus it was making less hp due to the thinner less denser air.

If what you are saying is true that the mixture is richer as you ascend, then computer would adjust and he would be making more horsepower at the summit than he did at the start line-which is absolutely not the case!

 

Great thread, I am in the same boat as you as well. I am looking into getting tuned by Cobb surgline but I do a lot of driving around and next year will be moving to co springs next year and need a tune to compensate for 6500ft all the way down to 2000ft. I may have to talk to them about the stradegey they use. I wonder how e85 gets affected by the elevation change as well?

 

+++. ^ Truth.

Back in 2010 I was asking the same questions as the OP. I live in AR but tuning was happening in Dallas, there is actually a 1200 elevation change so I asked Calvin (Cobb Plano Tuning genius) about it. He said exactly what moto said. When you are getting tuned anywhere, if you want to feel "safe" just tell the guy tuning that the car will be in a different elevation and not to really touch the barometer sensor calibration (even though most will not touch it when tuning).

 

i was at Pikes Peak. With a few teams, but I got to see some of it from inside turn 2.

You misunderstood what I meant.
Provided you maintain an optimum a/f ratio, any car will make less power as it goes up in elevation. Simply because there's less air, so you deliver less fuel, and hence make less hp. Obviously, if you didn't maintain an optimum a/f ratio, and the car went richer & richer as you go up, you're not going to make power from being pig rich either.

 

Sorry for the delay, for some reason, update emails were going to my spam folder...
but THANKS for all the feedback!

So it sounds like I might need gauges before getting a tune? I am using this car as a daily driver and don't have any plans of any more horsepower mods until my warranty expires. I was hoping to avoid getting gauges since they might make the dealership less trusting but it doesn't sound like I can avoid them... Gotta see if I'm running lean!


This is a very good point. I guess what I was worried about is - is there anything the tuner would change that would make the car less able to account for altitude as it does in its stock form? For example, if I add in an intake (as I'm planning), and they don't rescale the MAF table (instead, they just compensate for this in the main fuel tables), the car would no longer be fit for changing altitudes because the way the new intake responds at different altitudes is unknown.

It sounds like you guys don't foresee any major problems (knock, running lean, horrible performance, etc.) - is this correct?

Thanks for all the help!!!

 

Get a safe tune, get the gauges to keep track of everything and let your tuner know about the potential elevation changes and to compensate for said. You should be in good shape then.
Good luck.