Re: Boost problems, redux.

[Thomas Tornblom <Thomas.Tornblom@nexus.comm.se>]

> Date: Wed, 31 Aug 94 12:53:32 EDT
> From: glen@mass.smc.com (Glen Powell)
> Reply-To: quattro@swiss.ans.net
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> 
> 
> You're right! BAR is usually absolute, so 1.1-1.2 BAR is only 0.1-0.2 BAR
> above atmospheric, very low boost indeed. Remember, this is in a WAGON.
> I suspect that Audi sets the boost way low to extend the life of the 
> engine and drivetrain as a tradeoff vs performance. I asked Ned from IA
> about this and he said to check that the FWO throttle switch was going to
> 0.x ohms at WFO. I did and it was. So I then disconnected the vacuum line
> that the CPU and reduce the boost by. Still only 1.1-1.2 with only mechanical
> WG control possible. At this point I tried the ur-Quattro OEM black-stripe
> spring, but the CPU shut things down at about 1.6-1.6 BAR. So I reinstalled
> the stock 5000 spring, blue stripe & short in length, and made the WG
> adjustable, and cranked the boost up to 1.4 BAR with the adjustment screw
> I installed from the ur-Quattro WG, along with its spring. I'll need a 
> "chip" or other CPU mod to permit boost above this level, hence my intense
> interest in getting to the bottom of the "chip" BS. It sounds like I might
> just need to change some discreet components to allow the higher boost.
> That's what I'm trying to find out now. I'd be willing to pay a fair price
> for a "chip" *IF* it includes the spring and discreets to allow the higher
> boost.....
> 

The '87 100 turbo avant I had before only got about 0.2 - 0.3 bar of
boost pressure when I bought it. It had the electrically controlled
valve that allowed the computer to rise the pressure. I hooked up a
gauge with a T connector to the vacuum/boost hose leading to the
computer and a DMM across the wires to this valve and took it for a
drive.

I noticed that 0.2 - 0.3 bar was the max and no voltage across the
valve when driving with less than WOT. At WOT I noticed a pulsing
voltage across the valve, but no difference in pressure. It turned out
that the two hoses on top of the valve had been switched, rendering it
absolutely useless. Switching the hoses made the pressure rise to
about 0.4 bar at WOT.

This might be something more cars are suffering from.

Thomas