ecu mods--elec. boost controllers

[Ameer Antar]

I see what your saying about the zener diode, but I don't see how the 
resistor(s) come into play. I agree a zener diode would be great at 
allowing a lot more boost, and it wouldn't interfere with 1.3bar and lower 
operation. But there would be no way to control the max limit. No matter 
how high a voltage the pressure sensor was allowing for, the zener diode 
would still put out the zener voltage [2.7V or whatever]. So no matter what 
the actual boost is, the ecu would only see a max of 1.4 bar. I think this 
set up is too dangerous unless you have a good 2nd boost gauge and a 
watchful eye. But, I'd rather have the limit controlled electrically, 
instead of having to control it myself. I understand that the wg spring 
actually has a lot to do w/ max boost since the air-pressure on top of the 
wg diaphragm can only add a certain amount of boost on top of the spring's 
rating. But I'd rather know that the ecu could control the boost if 
something happened to the diaphragm or other problem. Maybe I'm missing 
something about this mod. I haven't really gotten the details about this 
mod. I'm studying EE, so if you have any technical info or links, that'd 
help a lot. Thanks much.

-ameer


At 05:39 PM 10/18/00, you wrote:
>Ameer,
>
>What you suggest would almost surely work.  But I don't see why you'd want 
>to do it that way when, for about $4.50 and twenty minutes of your time, 
>you can do the resistor/zener mod and have the same effect.
>
>Granted, the R/Z mod isn't the ideal way to go but then neither is what 
>you are suggesting.  The R/Z mod does not change anything below the zener 
>trigger voltage.  It should not change anything below 1.2 or 1.3 (or 
>whatever) bar.  It simply lies to the ECU when boost pressure rises above 
>the value set by the zener.  This is also what your computer controlled 
>bleeder valve will be doing.
>
>BTW, an '89 200tq I did the R/Z mod on (to 2.2+ bar - YeeeeHaaaawwwww!) 
>ran perfectly for me for 60K miles.  I have since sold it to another list 
>member and, from what he tells me, it is still doing a fine job for him 
>after another two years of service after the 60K miles I put on it with 
>the mod.  However, YMMV.