Part Throttle Boosting...

[Blitzeclips]

I've heard from a couple people that this is bad. Anyone care to explain why? I'm looking for a solid reason not what why you would think it's bad. A logical and relative reason. Thanks to all who reply!

 

[project_tsi]

If you have compressor surge, and end up with full boost at mid throttle, then your car will not run on is WOT map, meaning a/f and timing maps will not be the same as under WOT.

 

[Zenja]

The ECU calculates that based on airflow anyway (at least the 1g does) and not things like throttle position. It will run the right amount of fuel/timing for the load it sees.

I've heard people saying that it's possible to make it run a lot more boost from the turbo than what shows in the intake manifold (and your boost gauge) because the throttle plate is restricting the airflow. I can't really see this happening though, especially if your get your boost controller signal from the right place (the turbo compressor housing). Then even if somehow you do run a lot more boost in the IC piping than the intake manifold, it still can't go over what your normal full boost is set at anyway.

 

[CanadianTSi]

The ECU calculates that based on airflow anyway (at least the 1g does) and not things like throttle position. It will run the right amount of fuel/timing for the load it sees.

Bingo

 

[Blitzeclips]

I've heard people saying that it's possible to make it run a lot more boost from the turbo than what shows in the intake manifold (and your boost gauge) because the throttle plate is restricting the airflow. I can't really see this happening though, especially if your get your boost controller signal from the right place (the turbo compressor housing).

Thanks for the replies.
Exactly my thoughts. The turbo can't create more boost out of nowhere, and the boost controller physically will not allow more air to pass.

Perhaps it has something to do with excessive load (and/or backprssure) going into the turbo once there is already a decent amount of air flowing through it already. Then the sudden burst of the charge causes an abrupt change in the flow on the compressor. I don't know.

 

[cs82685]

Thanks for the replies.
Exactly my thoughts. The turbo can't create more boost out of nowhere, and the boost controller physically will not allow more air to pass.

Perhaps it has something to do with excessive load (and/or backprssure) going into the turbo once there is already a decent amount of air flowing through it already. Then the sudden burst of the charge causes an abrupt change in the flow on the compressor. I don't know.

Here's your answer...

is it normal for car to be lean during half throttle accelleration W/ boost?

Thats the ECU staying in closed loop during boost, and its still reading off of the o2 sensor to keep the A/F around stoich(14.7:1). There really isn't much of a way around this with that setup.. Either boost it a bit lighter, or put it to the floor, to kick it into open loop. As long as you are not getting any detonation, and you dont go though all the gears like that, then it should be fine. This is another reason I'm really going to like the Megasquirt.

-taken from a thread on 2gnt.


I'm not positive, but it almost seems that for boosted 420a's The ECU will fight your fmu, one wanting to lower fuel pressure (or keep it the same) while the other wants to raise fuel pressure until you are in open loop where your rising rate fpr takes over completely :shrug THis could but won't necessarily cause knock and high egts


Anyways Tom, this thread's a good read even though I know you're not on 2gnt. Definetly some interesting discussion on the issue

http://forums.2gnt.com/dcboard.php?az=show_topic&forum=8&topic_id=84050&mode=full

 

[Thomas91169]

If you have compressor surge, and end up with full boost at mid throttle, then your car will not run on is WOT map, meaning a/f and timing maps will not be the same as under WOT.

im not 100% sure but i am pretty sure this depends on what he is tuning with. If its a SAFC then he will not run his WOT map until it reaches the throttle percentage set by the user to engage the safc's correction. if your safc is set to engage at 80% throttle then until you hit 80% or above your ecu is just running off of what it sees normally, as you likely know a safc is a piggyback and merely fools the ecu into seeing more than what is there, thusly adding more fuel.

if its dsmlink you can PTB all day long, it will not just look at throttle to input fuel maps, but also airflow, and everything else your ecu does stock to calculate what fuel and timing maps to run. this is why dsmlink>*, you can input global setting and idc (injector dead times) and basically drive off into the sunset, dsmlink works with your stock ecu based on the settings you input for wot, anything less dsmlink runs a compensation factor for fuel, timing, airflow, etc.

just noticed hes n/t, so all of what i said doesnt apply. i suck @ teh forumz.

 

[totaleclipse_05]

I'm pretty sure it has to do with your MAP sensor. You have an FCD right? Well the FCD is holding the voltage at 4.6Xv when you are in boost. Because it is doing this, you aren't getting all the fuel you need for the amount of air you are giving the engine (ECU is giving the engine enough fuel for 4.6Xv, but not for 5.00+v which it is probably getting, but the ECU doesn't see it). When you floor it, the car goes into open loop mode which will deliver max fuel for the amount of boost (via FMU). It makes sense in my head, just hard to explain and put it into words.