ecu mods--elec. boost controllers

[Robert Myers]

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.

At 04:43 PM 10/18/00, Ameer Antar wrote:

>there's a lot of ecu mod talk. Mostly about cheap and dirty ways, not 
>replacing the chip. Well, I've been thinking about it, b/c the ECU for the 
>KH engine does not have a programmable chip, so a hack is the only option 
>other than ECU/harness transplant. If the ecu is designed for 1.4 bar, I 
>was thinking of regulating the boost pressure to the ecu. I want to be 
>able to get .8 bar or so, but I don't want to change the way the engine 
>operates below 1.4 bar. The other resistor or aquarium valve mods change 
>the apparent pressure throughout the range. However, if you could 
>electronically control a ecu leak valve, you could tell it to seal shut 
>until 1.4 bar, then gradually divert excess boost beyond that point, until 
>it reaches some set limit. The circuit would probably be just need a 
>couple pressure sensors and an op-amp or 2. The only thing is finding a 
>cheap air valve that can be controlled by an electric signal.
>
>To limit the boost pressure sent to the ecu, you could make the valve open 
>slightly and adjust its position just as an aquarium valve, but by sending 
>it a voltage. Or you could do it by opening and closing the valve at 
>different duty cycles to achieve the right amount. The problem w/ this is 
>the valve would prolly have to move very fast. The problem w/ the first 
>method, is that I've never seen a solenoid valve which had variable 
>opening...ie. it's either open or closed. I was thinking of using an old 
>wastegate freq. valve, but I'm not sure how if it'd work, and my car 
>doesn't even have one. How so those boost controllers like GRreddy or Apex 
>products work? Do they use a variable valve or do they use a duty cycle on 
>the valve? Wonder if the valve can be bought separately...I guess I could 
>just buy a boost controller and replace the wg spring, but I'd rather come 
>up w/ something myself if they're like $200. I've asked lot's of questions 
>so I really appreciate any info you can send me.
>
>-ameer
>'84 5kT
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Bob
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