hey everyone:

how does it work if my car is tuned and running, say 7 pounds of boost at 4000 ft altitude, and then i take a trip to an area that is at sea level....? will this icrease the compression considerably and now create an unsafe level for the motor?
just wondering...

 

I believe that with the TT, you will still reach the same boost level at the different altitudes. Closer to sea level where the air is more dense, the turbos will not have to work as hard to produce the desired boose pressure.

 

i was reading an article about turbos http://www.turbomustangs.com/turbotech/main.htm

it says that at higher altitude, turbos work better because there is less difference in atmospheric pressure and boost pressure-or something like that.. anyway, my take was that a turbo worked less at higher altitude/ opposite of productivity of an engine- producing less at high altitude because of the decreased density in the air....
if anyone knows more detail about if i need to look out for anything at sea level, please let me know

thanks

 

Turbos do not work better at higher altitude. They lose HP but at a lesser rate than a normal aspirated engine.

 

When you go down to sea level, you will make a lot more power and will definitely need to retune. I can nearly guarantee a fragged motor if you don't retune.

The issue that comes into play is absolute pressure and it's relationship to cubic feet of air per minute (CFM).

At 4000 feet, the ambient atmospheric pressure is somewhere around 13psi. Your boost controller is set to 7 gauge psi. This yields a total absolute intake pressure of 20 psi.

At sea level, the atmospheric pressure is 14.7 psi. Again, your boost controller is set to 7 gauge psi, yielding a total absolute intake pressure of 21.7 psi.

At sea level, your engine will flow significantly more cubic feet of air per minute. 8.5% more, in fact.

Given that your engine management is based on gauge psi and RPM, the system will behave no differently than it does at high altitude. In other words, it will not spray enough fuel to compensate for the higher atmospheric pressure. Your engine will go lean and pop, probably before you get to your destination.

 

thanks for the imput... but you guys are giving me the problems, not the solutions
so i retune the var the day before i drive out to a lower altitude, or will the profec-e01 allow me to tune it to compensate???

any input?

 

ATTN: Gary..you said,
"Turbos do not work better at higher altitude. They lose HP but at a lesser rate than a normal aspirated engine."

and i quote...
this says that that isnt the case, any comments/explanation?

"The high-altitude performance of a turbocharged engine is significantly better. Because of the lower air pressure at high altitudes, the power loss of a naturally aspirated engine is considerable. In contrast, the performance of the turbine improves at altitude as a result of the greater pressure difference between the virtually constant pressure upstream of the turbine and the lower ambient pressure at outlet. The lower air density at the compressor inlet is largely equalized. Hence, the engine has barely any power loss."
this was found on that website i listed a few posts up the page.

i'm not trying to argue, i desperately want some ACCURATE advise.
Thanks...

 

Yes, the wording there is a little misleading.
"the performance of the turbine improves at altitude"
Yes the turbine will spin faster as altitiude increases to keep the boost level constant but hp still degrades as the air is less dense although not as fast as normally aspirated.
As an example a normally aspirated engine will develop only 74% of sea level power at 10,000 feet while a turbocharged engine will produse 81.5%. That is why aircraft sometimes employ turbocharges.
(source: Turbochargers by Hugh Maclinnes)

 

So are F/I owners going to have to tune their engines when at different altitudes? I find this hard to swallow.

How does Subaru/Mitsubishi/VW/Audi handle this on their new turbo cars?

 

factory turbo cars have more advanced engine management. Usually they will include a barometric pressure sensor to help figure out whats going on "self calibrate"... factory turbo cars run a lot more rich and conservative as well so they have plenty of room for error anyway. Factory turbo cars with MAF put the sensor before the turbochargers and see precise input as to air volume as well. All of our FI 350z are running horrible hack job band aids to compensate for the boost... when its done from the factory its done right and you dont need to worry about that stuff.

 

would you consider the pe kit with technosquare flash a horrible hackjob?

 

Yes.

It's still not an ECU designed to control or read positive intake pressure. It's an N/A ECU hacked to spray more fuel to (hopefully) make up for the increased air consumption.

Definitely a hack job, in my opinion.

 

So none of the available F/I kits can account for varying altitudes? All are hack jobs?

I would hate to go to another state and have my engine blow-up. This is definitely a show-stopper for folks who like to travel.

 

For the people who are worried about their cars when they get to sea level your solution is to save two tunes on your computer. U will just have to upload it in your PCM or whatever you are using to tune if u know ur going down to sea level. U can even upload it before u start your trip just to be safe even if u are going to run a little bit rich until u get to sea level. I dont see a problem in doing that.

 

I am clueless as to uploading stuff into the car, so this solution won't work for me.

But then again ... maybe most people who do F/I will be knowledgeable in this stuff? In other words, these F/I kits are not designed to be operated by the average Joe?

All I want is a mild-boost/safe F/I kit that I can just have somebody put on my car and forget it. I was really hoping to F/I my car someday, but looks like I don't have the knowledge to maintain such a beast.

Makes me appreciate factory-turbo cars even more.

 

azrael is right. It is quite a rough setup and it has limits but it still does make good power (obviously).
The big problem comes from the fact that they are using a blowthrough MAF system. The MAF is reading the air after the turbo. It doesn't compensate too well for higher pressure air. The emanage is supposed to cover the enrichment. The problem is, it uses a relative pressure sensor.
Most turbo cars nowadays run the MAF before the turbo and they know enough about boost and whatnot to properly enrich for it. N/A cars usually don't, however.
This setup will work until AEM or someone else comes out with a reasonably priced and reasonably advanced engine management system that is MAP based to solve most of the issues. Then you have no MAF and enrichment is properly set up to match the varying altitudes, etc. They use a proper Manifold Absolute Pressure sensor.
Tweety you are right, however. The F/I kits require a moderate amount of knowledge to safely operate the car. You can't just throw this on joe blow's Z and say, there you go; have fun. That is mostly the case with forced induction (and especially turbo) cars. Just educate yourself as best you can while you save up for the mods. Understand how they work and what things will put you closer to the danger zone and you will be perfectly capable of owning one.

Mark
www.Quantum-Racing.com

 

Thanks for the info QuantumZ/Mark, that was a very informative post and I appreciate it!