The oxygen concentration remains about the same at higher altitudes but the absolute amount of oxygen molecules does significantly decrease. This will affect the performance of the engine.

 

Not if your getting same PSI. The thing is that to get to that PSI, turbo has to work harder and hotter. Hence the preformance reduction. amount of oxygen in a given presure is the same at any altitude.

 

Exactly.

From the ideal gas law: number (moles) of oxygen molecules = PV/RT

I'd imagine that the affects of altitude are much more pronounced for naturally aspirated cars.

 

Right,
I didnt want to go that deep into thermodinamycs lol but yes. Let see if they can come up with something to fix the tune. I know this has been happening with other fellow miniacs, with the same tune and with other canned tunes.

 

And this is why we use mass flow fate for everything instead of psi in the real world. too many variances in the system to just talk about psi differences.

 

Boost pressures at altitude are different.
Atmospheric pressure at sea level ~14.7 psi.
Atmospheric pressure at 4000 ft. ~12.7 psi.
Manifold pressure - atmospheric pressure = boost pressure. So.....
Sea level boost pressure of 10 psi = 24.7 psi manifold pressure.
4000 ft boost pressure of 10 psi = 22.7 psi.

The general rule of thumb is that engine output will drop ~3% for every 1000 feet above sea level as there is roughly 3% less oxygen in the same volume of air due to the lower density.

 

Thermodynamics apart the issue with the tune is that doesnt hold boost

 

Refresh my memory please. What turbo are you running?

 

I think runs the JMTC Dom 47mm

mQubed Motorsport, Manic Tuning Dealer

 

Right-

 

i know it is a pain but have you put the stock turbo back on it and see how it runs? Remember the stock turbo will only hold boost in the upper gears ( 4th on ) till around 4500 rpms and then it runs out of breathe. Doesn't matter what tune you have on it the turbo is just out of air .
If you put a new turbo on and you have slowed down from a stock turbo then I would look at what has changed. Your manic tune is pretty much the same "safe" tune he sends everyone for a base start.
I had stage2+ and just changed the turbo and picked up major hp without even going to stage3+ tune due to the new turbo being able to keep pressure/flow all the way to red line ....

This video is just for information only.... But there are plenty out there to watch that kind of has the same info ...

 

No, I havent tried that yet. I think I can throw in the old JCW turbo and see what happents. But you mean leaving in the stage 3 tune?

 

I would consult your tuner on that .
Do you have the switch ? I would think map a or b would be okay cause your jcw turbo might can achieve target boost on A map. B or C it's prob going to pin the wastegate cause your not going to be able to make the target boost, the part I'm not sure of is will the ecu hold timing back cause you have not hit the target. The load table comes in effect as well...

So I would check with your tuner cause I don't want to say yes and something happens but I personally think you will be okay .

As far as altitude, remember back in the day you had to jet the carburetor if you where going up or down in altitude, when fuel injection came out it corrected for altitude using MAP and BARO sensors. Yes the air is thinner and yes performance will drop some but you still should have a good running motor.
I did trends last weekend going from 2k to 8500.
At full throttle map sensor was:
8k- 66
2k- 75
Load table
8k- 69
2k- 93
MAF
8k-17
2k- 24
Boost
8k- 21
2k- 23


Now around 4-5k altitude I had some boost swing but the road was short and a few of my logs where 3rd gear

Yes I could butt tell that the car was not at its peak performance but the car still spun the tires with 3rd gear punches.

Now my standalone boost gauge was going negative at idle cause it's not compensate (I think I saw -5 at 8k)so if I was watching my gauge it was showing 17 psi full throttle at 8k altitude
Take the -5 plus the 17 and that's a span of 22 which is what my logs showed. The ecu will compensate.

 

Now that I think about it, can you log your MAF? That could show if your turbo is doing what it's suppose to be doing .

 

Hi Guys, I currently run stage 3 on the AP but really want to upgrade to manics stage 3 tune, I live in Indianapolis and unfortunately there is no manic dealers on the Midwest so I will have to send the ECU to manic, would you guys recommend doing this? I don't like having to take the ECU out of my car

 

I gotta agree with RidinDirty --- turbo is everything at high altitudes. I'm only at 4500' but have (had) a big Garrett and never had an issue with losing boost at high RPM's. I held 30PSI all the way to 7200RPM --- from -3 to +27PSI on my external boost gauge.

There will still be a noticeable performance change between sea level and "high" altitudes, even with consistent boost pressures. I have to agree with Cerenkov about oxygen --- "The oxygen concentration remains about the same at higher altitudes but the absolute amount of oxygen molecules does significantly decrease. This will affect the performance of the engine." I don't know what else could be causing the performance loss at elevation --- my turbo is (was) not controlled by the ECU --- waste gate has a Manual Boost Controller (positive pressure, not vacuum), and DV (BOV) is externally set for a 10psi differential.

 

Do it! Just remember to disconnect the battery first --- apparently there's a counter someplace that knows when maps are changed. My '07 has a couple tabs under the ECU, holding it in place --- similar to a connector tab that needs to be pressed to release the unit. Not readily visible. Well worth the effort tho. Talk with your chosen tuner about ECU removal --- maybe he can advise. I used EuroTechs in AZ --- really easy to work with.

 

Wow, lets hope a well known vendor in this forum doesnt do that

 

I have some logs, whatd PID will be the MAF?

 

If you want to private message me I can tell you my experience with " a well known vender " on this site ...

MAF. - mass air flow. What are you using for data logging? I think my stock turbo ( non jcw ) maxed out around 19lbs/min , with the size turbo you have and it's built correctly you should max out the MAF which is 25lbs/min . With my stage 3 my MAF is maxed to redline.

 

VCDs. I logged a couple of runs and the Manic Dealer three more. Dont know if that was logged though

 

I use Palmer so I can't tell you if it was logged, but with Palmer you don't have to have it on the log during the run, you can go back and add it.
If your going to play in the game go ahead and look at Palmer, under 100 bucks and you can get the software, cable,wifi and log it yourself. Also reset codes etc. one thing I learned if you are having issues is to put the stock tune back in and go put 15-20 miles on it and come back and look at faults. It will capture more codes in stock than with tune in. I was having sputtering issues and could find anything, popped it back in stock and got a code for #2 misfire, turned out I had water from when I washed the engine sitting around my plug, put the shop vacuum on it and everything went away. So it's helpful to have and cheap.
Use laptop, phone, tablet etc ...

 

+1 on Palmer. I use it on the iPhone and laptop w/cable to datalog. Comes in handy when I send logs to Nick at Manic as he uses the same.

 

Ok, but Im no tunner, just want my GP tu run fine!!!!

 

You don't have to be one, but it help to see what's going on so you can trouble shoot or have others look at it .
You can send log files to your tuner as well