I went for a drive today. I wanted to have some fun on Washingtons North Cascades pass. It's a moderately twisty road that gains a few thousand feet in elevation. Down closer to sea level, I can pull out and pass most anyone, even uphill. However, I was having trouble passing in the mountains. I've had similar trouble on carb'd cars, but all the newer FI cars have been great about not losing too much power at higher elevations. Does the factory ECU in my '87 N/A not compensate for altitude? Will I have to wait 'till I can go stand alone to have any power going over the passes? I got stuck behind p/u's because I didn't have enough power to pass, even on a half mile straight. Once I got back out of the mountains all was well, but the mountains are where the roads are.

 

Time for a turbo II my old house in winterpark,co was @ 9,200 feet above sealevel! sriving down to denver was a real treat.

 

Actually, the plan is to finish up my suspension, than go with a large street port and whipple twin screw s/c. I know, s/c aren't popular, but I have very specific plans in mind.

Am I to understand, then, that the computers in our cars are not as good at compensating for altitude as the friggin' pick-ups I couldn' pass? Will a haltech help with that problem?

 

Higher altitude will naturally yield lower power due to the thinner air. I know when we took my friends Sequioa to Big Sky the thing was a dog going up from the lower meadows

 

I am unsure about how the ECU can compensate for altitude gain. You are fighting mother nature on that one. As you gain altitude there are less air moulecules per unit of air. The ambient pressure is much less at a higher altitude.

So if your at sea level and the pressure (Barometric that is) 29.92 " of HG that is the most your cars engine can pull in at full throttle. That is the most air. Now, as you climb you loss approx. 1" of HG per 1000 feet. So, lets say you floor it at 7000 feet the ambient pressure is 22.92" of HG. There is less pressure and there for less air for your engine to consume.

And if there is less air then there is less power.

So, when you have a turbo you are increasing that pressure. You can now build pressure above the highest ambient pressure.

James

 

Nice work James!

 

Modern ECU's lean out the fuel mixture to compensate for lower ambient pressures (less oxygen).

I ask if the ECU in my 7 is less capable in this department because I used to own a 3.8L Mustang. At sea level, my 7 would walk the Mustang any day. However, the 'stang didn't lose power like the 7 does.

I understand that all cars lose power at higher altitudes (even forced induction, though to a lesser degree). I had expected, however, that I would lose power at the same rate as every other FI N/A vehical on the road.

 

Next time you're in the mountains. Pull over and shut the car off and restart it. See if this helps. In older FI cars the ecu takes an atmospheric pressure reading when you start the car. The logic being atmospheric pressure stays pretty much the same driving through town/city because the elevation doesn't chance all that much.

 

Should I let it sit for any length of time, or just off and back on? Also, do the aftermarket ECU's take readings constantly? I would expect yes, since they are newer, and AFTERMARKET.

 

Check your fuel pressure. The loss of ambient pressure can cause a loss of fuel pressure.

Yes, an aftermarket ECU can compensate for differing air pressure, however it cannot INCREASE your intake air pressure. While an aftermarket ECU may produce more power across the board if tuned correctly, the engine will still perform better at low altitude and in cold temperature, as the physics of producing power cannot be changed.

 

shows how lucky you sea level guys are. but we do have a advantege when we build are cars up here and we think they are fast, then we go down to sea level and holly ****. what a difference. One thing that realy sucks is up here at 12.5 psi atmuspheric pressure my dam turbo will never turn off because of the extra load.

 

Count to 10 and then restart it.

 

So at a high altitude the car seems slow because it is dumping fuel into the engine. So maybe the lowered power is coming from two factors. First the lowered pressure. And because the ECU is still using the fuel that is need for sea level. That should be way to much fuel. So the engine runs rich that should kill power. Sort of a double wammy. Both altitude and fuel hurting performance.

Wonder how your Mustang was different from the 7.

I know if your in a piston powered aircraft you are supposed to lean the mixture before take off. And not takeoff full rich.

James