Ok so im wondering what are the best ways to tune for different altitudes and air density's without remapping the whole fuel map.

Will it be a maf compensation or something else?

If I haven't looked very hard and its front of me sorry but hopefully you guys can point me in the right direction.

Thanks

 

What do you mean? I've climbed 7500ft in the evo it doesn't need a retune but cranking the boost up becomes the biggest issue the stock turbo really doesn't want to hit full boost at high altitudes.

A Boost controller perhaps is what you need.

 

Shouldn't PSI based boost control solve this dilemna as well?

 

Last time I tuned the car and then recently went to the track at a different elevation it was super rich and I had to take out lots of fuel.

 

Fuel trims changing?

 

As your altitude raises, your load will increase for a given mass airflow rate. Thus you'll end up in different sections of the map even when boost (MAP) stays the same.

 

Interesting, ok, makes sense. I am curious for this is one of the things that I wanted to be able to tune for as well. I wanted to be able to run from sea level to 10k without having to adjust the maps. or fuel...

I also thought that the ECU did some things when it was stock to control the elvation shifts in relation to fueling?

Would Speed Density boost control help with this, or do we need to drop the boost control all together and focus on the fuel. What do some of the Rally Cars do to solve this. Ok, well they probably tune for each leg of a race...lol.

...But what about us Road Warriors?

 

I think in this case, load based boost control is smarter....probably why Mitsu used it from the beginning?

 

. Here I was doing the PSI based, and then getting ready to go over to SD based boost control.

So for those of us who do open road racing, long hauls, or the occasional Cannonball... , load base FTW?

Thanks Jack.

 

Or you can tune the areas of your map that are used while at the different altitudes, so you have a FULLY tuned map for your application.

 

New to the whole tuning process, been tuning my car for approx 6 weeks currently and just taking my time to learn all the area's. Can you give me some logic in walking through the areas for different elevation? Im confused on combining the elevations in say timing... How would I tune for different elevation utilizing the same timing map?

 

you'd datalog your timing,rpm,2 byte load while at the other elevation and adjust those areas of your fuel and timing maps accordingly.....blending them with the areas you already have tuned for the lower elevation.

 

The problem with load based boost control is power will drop with altitude, by a large margin. By 4500', you'll be down about 15% from sea level. This is usually not what you want as it makes the car less predictable in power delivery.

I could be wrong here, but I believe the speed density patch virtually eliminates the baro correction applied on the load calcs. This means load will stay constant based on manifold pressure and changes in barometric pressure will not really matter. This is not the case with the stock MAF system as there are three load values. Uncompensated (used for fuel?), Baro Compensated (only used under certain low temp conditions?), and Temp + Baro compensated load (timing?). Because there is no longer a baro input, the uncompensated load and the barometric load should be equal, thus fueling will remain the same regardless of altitude.

On the speed density patch, if you used pressure based boost control, you could potentially hold power pretty constant. As your altitude increased, the ECU would raise boost pressure (gauge) to keep the manifold absolute pressure at a constant. All else being equal, manifold absolute pressure will directly correlate to engine power.

The only major issue here though is that as your altitude increase, the pressure ratio the turbocharger runs at increases even while gauge pressure remains constant. This increase in pressure ratio increases exhaust back pressure, which will reduce engine volumetric efficiency. This is amplified by the fact that you will have to increase gauge pressure to maintain absolute pressure.

One potential solution is to tap into the factory baro correction. The factory values help compensate for air density. You could potentially remap the values to accommodate the changes in VE. It would require a new baro sensor which should be pretty straight forward as the factory sensor is 0-5V.

 

The ECU adjust everything well under 5000 ft. I think it will be good to work on MAF / Barometric sensor calibration/ compensation above 5000 ft only. I wont recommend any patch that eliminates baro input for someone who is going far from home with his car. For example, here in Mexico city (7200 ft), we need to have "specific maps" to go on the limit but I know I can not get straight to Acapulco with the same Rom, knock will appears under 5000 ft...

 

Im still very confused on adjusting the maf/barometic compensations... maybe i just need to sit down and re read some stuff tomorrow.