Blow off valve

[Jim Pearl]

Sounds like a quickie HKS EVC. The EVC I've got uses Fuzzy Logic to program 
itself. What it does is show the wastegate zero pressure until it 
calculates that you're about to hit the pressure you've punched in. When 
you hit the limit it pulses the boost solenoid to keep the pressure there. 
The Fuzzy Logic programming helps it "learn" the curve of your car so that 
it can better prevent overboost. I also get an overboost alarm, pressure 
readout (LCD), three levels of boost not including manual, and an overboost 
button that I can remotely mount that will allow the engine to overboost a 
programmed amount of time after I've released the button. Lot's of nice 
bells and whistles on this puppy. One of the nice things about it is 
quicker boost response. Since most wastegates are mechanical diaphragm 
devices they tend to begin releasing boost before full boost so you don't 
get full boost as quick as you'd like, the EVC holds the vacuum line to the 
wastegate at zero until just before max so - faster boost!

BTW - mine cost about $800 freaking bucks! If you can come up with a low 
buck way to do this that works well there are many people who'd like to 
have it. There are also some nice "graphic EQ" type devices that allow 
higher boosts at certain RPMs - these are also expensive but nice to have 
devices.

----------
>From: 	Bill Sarkozy[SMTP:mymove at serv01.net-link.net]
Sent: 	Tuesday, February 27, 1996 12:53 AM
To: 	diy_efi at coulomb.eng.ohio-state.edu
Subject: 	Re: Blow off valve

At 01:02 PM 2/26/96, you wrote:
>
>
======SNIP=====
>
>I have been thinking about this because I was considering implementing 
some
>sort of electronic wastegate to allow the boost limit to adjust from 12-15 
>pounds at low rpm to 7-10 pounds at red-line. Why? Well the way I see it
>there are all sorts of restrictions to power at the top end (air-flow,
>exhaust-flow, fuel-flow) that disappear at say half red-line why not take
>advantage of them? Any comments?
>
>~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>Jeff Hansen
>Anaheim, California, USA
>JHansen777 at gnn.com
>http://members.gnn.com/JHansen777/car/index.htm
>Seven pounds of boost is a 'Good-Thing'
>~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>
>
If you had some sort of RPM-activated switch, the solution is
easy......bleed off some of your boost via a solenoid valve to "fool" the
wastegate at low RPM.  When you hit your arbitrary limit, close the bleed
solenoid and the wastegate will see full boost and react normally.  Most
T-Bird Turbo-Coupe owners know of this trick, but simply use a manual bleed
valve to keep the boost high all the time........hang on!!!!!!





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