Lack Of Boost

[Dandu 0]

Hi mates,

 

I recently tried to raise the boost of the engine mentioned above. While I was fiddling the boost-/overboost-maps, I got in trouble twice. At first it seemed like the tuning-ECU (0261200219) got out of order. After that I suddenly lost the boost with my standard-ECU (0261204839), too. The whole story is depicted in:

 

http://forum.205gtidrivers.com/index.php?showtopic=121378

 

The current problem actually doesn't have anything to with modifications. Therefore I decided to cross-reference the thread in this section as well. Just now I'd like to see the engine up und running fine with a standard ECU (0261204839) with standard boost.

 

I hope, there is anybody, who already dealt with a lack of boost. Please feel free to update the thread in the modifications-section of the forum.

 

Thanks in advance,

Dandu

Edited July 15, 2010 by Dandu

[blniasgti 0]

hi i have never delt with this type of turbo'd engine but have had 2 turbos before (R5 GT Turbo and Fiat Uno Turbo) the R5 cant compare as it was on a carb but with the Fiat i found you could just unplug the overboost sensor then set the boost to whateva you fancied (obviously making sure the turbo could cope.....) without touching the ecu.

 

As far as lack of boost i can only guess the fuel cut off is cutting in on acceleration and i would personally not bother with trying to re-map or chip the ecu but to mechanically turn the boost up by either the actuator or by putting in a mechanical valve and setting the boost with them...

 

I dont know how much boost you would be looking for but for most stock turbos anything over 1 bar pressure would greatly reduce the lifetime of the turbo thats if it could handle it at all !

 

First thing i would do before playing with your ecu as you state that the boost is changing constantly is :

 

1. make sure you have no splits tears or perished pipework,

2. make sure your wastgate and actuator are correctly functioning,(check both springs)

3. visually check the impella blades and spin by hand (if there is play in the shaft then this could cause the turbo not to spin centrifugal and create constantly different pressures)

 

Otherwise if its still giving you random figures you could give your turbo to a specialist who can tell you if its spooling up properly as from what im getting from reading your other thread is it maybe the turbo thats your problem ?

 

Hope this may help ?

[Dandu 0]

Hi blniasgti,

 

I'm grateful for your advice. You can be sure, at the moment it's not my intention to raise the boost. ...

 

I began with raising it, as the engine / car seemed to be pretty healthy. And actually I was successful in doing it. That means, I figured out which maps to alter and how to alter them ... to increase boost and leaving overboost out, just to apply 1bar boost pressure constantly.

 

Applying a mechanical boost controller doesn't give me the chance to do that. As far as I understand the principles of a mechanical boost controller, I can only set up one value for pressure to be released from the system. Let's say: 0.35bar. Although a pressure of 1bar enters the feed line of the wastegate actuator (starting at the boost solenoid), only 0.65bar arrives at the end. Therefore keeping the wastegate open, forcing a lot of exhaust gas to bypass the turbine wheel and keeping boost pressure constantly at 1bar. But what happens, when the overboost sets in? The boost solenoid reduces pressure going to the wastegate. The pressure entering the wastegate feed line goes down, the mechanical boost controller releases 0.35bar of the pressure, finally we have less than 0.65bar pressure at the wastegate. Motivating the wastegate to close, giving the turbine wheel the chance to increase speed and the compressor wheel to raise boost ... It will finally result in a boost pressure higher than 1bar. The end of the story is the fuel cut setting in. Thus, running a mechanical boost controller makes it necessary to pay attention to the overboost as well. Finally you will have to alter the pressure, that is released with the help of a mechanical boost controller, to a value close to approx. 0.2bar. Giving the system a chance to deal with the overboost properly, but reducing standard boost to approx. 0.8bar. I appreciate any kind of correction, if my theory is wrong.

 

But I deviate from the topic. I'd like to run the basic setup, preceding a proper solution for my current problem "lack of boost". Your ideas are pretty good, although I don't like your final conclusion. )

 

I'll keep you informed. Bye Dandu

Edited July 15, 2010 by Dandu