ecu mods--elec. boost controllers

Ameer Antar ameer at
Wed Oct 18 17:43:24 EDT 2000

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 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.

'84 5kT

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