NethercuttML2

So I'm wondering how/what you tune the fuel curve to look like.

If a stock unmodded N/A car is tuned for a smooth flat torque line, does that mean that a turbo fuel curve would start low, and then increase eventually sweeping up in RPM? And would a Supercharged fuel curve look similar to the stock N/A fuel curve, only moved higher up the graph for more fuel overall?

Here's kinda what I am getting at.

http://www.turbominis.co.uk/forums/a...s/167289-1.jpg


Assuming this flow map. Let's say I had a magic switch that would flow 145 CFM (10lbs/m if I understand the conversion right) through this turbo. Assuming I wanted to run ~7PSI (1.5 compression ratio?) that would put me in the 78% range on that turbo. (If I can read those things right, I don't even know....) But, if I had this magic instant on turbo, when tuning with standalone, do you build the fuel and spark maps around the boost, assuming that it is always there? Or does the standalone only add the additional fuel when it sees the pressure?

So, if there were such a thing as a On/Off turbo, could you easily drive it well with the turbo off, and once switched on, the standalone would check MAP to determine if it needs the additional fuel, right?

These are dumb questions I know, but I'm just wondering. I've never tuned a car, never dealt with boost, and never tuned a boosted car. So just trying to get the scope of it. Thanks fellas.

QikEnuF

I think most only add fuel when it sees increased pressure at the manifold, but I could be wrong. I know a boost referenced fuel pressure regulator works that way..

E-b0la

basically there are maps for all possible vacuum/boost levels and RPM values the car will see. Depending on what the MAP sensor reads and the RPM, The ECU reads the cell using that as input and puts the signals out to the injectors to dump appropriate fuel and change the timing accordingly.

I don't think what the curve LOOKS like is really that important, as long as there is proper A/F and proper timing.

not really sure I understand the Question :1 :P

HiProfile

Ditto. As I like to say, every turbo car is an NA car at low load.

You are possibly thinking more in terms of a MAF-based system. They use 'curves' for certain aspects of the system, but still base it off overall intake volume. To tune MAF, you alter that curve a little, then alter certain tables. WIth a MAP based system (Honda), you have a big matrix of PSI vs RPM. If you are at 5000rpm and 10psi, it has a specific fuel value it uses. If you suddenly close the throttle, it will instantly read from the 5000rpm cell that the map sensor points to (likely to be -26" Hg in this case).

In other words, every few hundred rpm has its own 'curve' from 0psi absolute to whatever psi you can read with your MAP sensor.