Trying to understand the ECU and methods for upping boost pressure.
03-15-2007, 06:26 PM
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Trying to understand the ECU and methods for upping boost pressure.
Correct me if I'm wrong, I've been doing some reading at "How Stuff Works"
Ok, the car has an ECU. The ECU reads how much air is coming into the engine as well as the pressure of that air in the intake manifold. Based on this info (and many other readings) the ECU then determines how much fuel to spray through the injectors by looking up values in a table and tweaking those numbers based on sensor readings. So for instance, more air in (boost) will mean more fuel sprayed in order to maintain the appropriate air/fuel ratio. Right?
An aftermarket chip simply replaces the lookup tables on the ECU with base values that are more aggressive. Right?
So then theoretically, if I were to massively increase the boost pressure without an upgraded ECU the car would still run fine (granted the fuel injectors can spray enough and the octane is high enough that the fuel doesn't pre-detonate). Right? How much boost can a stock ECU calculate?
Now the second part of my question...
I've been examining ways to up the boost and have found three basic methods. First, I could put a stronger wastegate spring (1.9 bar) on the car which would reduce wastegate creep and up pressure. But it wouldn't eliminate creep. Second, I could install an N75 boost valve which would only allow air to the wastegate at higher pressure levels, still with creep though (I think). And third, I could build my own boost controller like the guy at AutoSpeed did to stop boost from getting to the wastegate completely until a desired pressure is obtained.
Out of these three methods, I would only do ONE, not several, right? If I make my own boost controller then I basically take control of the wastegate way from the ECU, right? Does this have any bad side effects? This is assuming I use reasonable boost values, of course.
<a href="http://www.howstuffworks.com/fuel-injection.htm/printable">How Stuff Works</a>
<a href="http://autospeed.drive.com.au/cms/A_0670/article.html">AutoSpeed 1</a>
<a href="http://autospeed.drive.com.au/cms/A_0685/article.html">AutoSpeed 2</a>
<a href="https://forums.audiworld.com/s4s6/msgs/49283.phtml">N75</a>
Thanks. :-)
Ok, the car has an ECU. The ECU reads how much air is coming into the engine as well as the pressure of that air in the intake manifold. Based on this info (and many other readings) the ECU then determines how much fuel to spray through the injectors by looking up values in a table and tweaking those numbers based on sensor readings. So for instance, more air in (boost) will mean more fuel sprayed in order to maintain the appropriate air/fuel ratio. Right?
An aftermarket chip simply replaces the lookup tables on the ECU with base values that are more aggressive. Right?
So then theoretically, if I were to massively increase the boost pressure without an upgraded ECU the car would still run fine (granted the fuel injectors can spray enough and the octane is high enough that the fuel doesn't pre-detonate). Right? How much boost can a stock ECU calculate?
Now the second part of my question...
I've been examining ways to up the boost and have found three basic methods. First, I could put a stronger wastegate spring (1.9 bar) on the car which would reduce wastegate creep and up pressure. But it wouldn't eliminate creep. Second, I could install an N75 boost valve which would only allow air to the wastegate at higher pressure levels, still with creep though (I think). And third, I could build my own boost controller like the guy at AutoSpeed did to stop boost from getting to the wastegate completely until a desired pressure is obtained.
Out of these three methods, I would only do ONE, not several, right? If I make my own boost controller then I basically take control of the wastegate way from the ECU, right? Does this have any bad side effects? This is assuming I use reasonable boost values, of course.
<a href="http://www.howstuffworks.com/fuel-injection.htm/printable">How Stuff Works</a>
<a href="http://autospeed.drive.com.au/cms/A_0670/article.html">AutoSpeed 1</a>
<a href="http://autospeed.drive.com.au/cms/A_0685/article.html">AutoSpeed 2</a>
<a href="https://forums.audiworld.com/s4s6/msgs/49283.phtml">N75</a>
Thanks. :-)
03-16-2007, 03:19 AM
#2
Your description of how the ECU works is correct.
1. A stronger wg spring might increase boost response but will do nothing for overall boost unless you go with a crazy strong spring.
2. No such thing. ECU controls N75 regardless of what you use.
3. You could.
Given your very good description of how the ECU works, why would you then remove control of the boost from the ECU? The ECU needs to control boost to balance it with correct fueling and timing. I'd say skip all three. Do a chip and be done.
2. No such thing. ECU controls N75 regardless of what you use.
3. You could.
Given your very good description of how the ECU works, why would you then remove control of the boost from the ECU? The ECU needs to control boost to balance it with correct fueling and timing. I'd say skip all three. Do a chip and be done.
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