HELP: Backfiring in the intake and 20 PSI of boost

[Jack Gagnon]

How much spring pressure are you running?  Do you have an adjustable seat?
If the spring pressure is cranked up, the spring will override the ecu
frequency valve control. and result in overboost.  Try reducing the spring
pressure or put in the stock spring.  The fact that you get overboost
without the wgfv hooked up indicates the spring is controlling the boost.

Jack



-----Original Message-----
From: quattro-admin at audifans.com [mailto:quattro-admin at audifans.com]On
Behalf Of Tim Penasack
Sent: Sunday, June 09, 2002 12:10 AM
To: Quattro
Subject: HELP: Backfiring in the intake and 20 PSI of boost


The subject line says it all and I think that they are related:

86 4ktq Rally car
 - running a 1987-88 5k MC-1 engine with a single knock sensor
 - running the Charlie spring at 1 bar.
 - stock ECU
 - MAP sensor is grounded
 - I have not wired a light to read the diagnostics.
 - 5K bypass valve plumbed through the 3rd opening of the IC and into the
down pipe
 - brand new cap, rotor wires and plugs

There are no other engine modifications.

I installed the waste gate frequency valve last Thursday night and took it
for its first long test drive today.  Here is the problem(s);
- It sounds like I am getting some back fire into the intake manifold
- I am getting 20+ PSI of boost (my gauge max's out at 20)

When I disconnect the WGFV I don't get the backfire into the intake.

With our without the WGFV I get more than 20 PSI of boost - while this is
fun its not practical I will eventually blow the turbo.

Questions:

- How come the WG is not opening up after I exceed 1 bar? (WG diaphragm bad?
WGFV plumbed incorrectly? are there issues running the vacuum for the bypass
valve and for the WGFV off of the same fitting? (it comes after the throttle
body)

- Is chipping the ECU going to the resolve my problem or will it just
correct the fuel/air mixture to reflect the environment  due to the stiffer
spring?

I need to get it running smoothly very soon since I need to install a turbo
restrictor due an upcoming race in Canada.  I would like to get these issues
resolved prior to installing the restrictor (less variables to contend with)

Thanks I am open to any ideas
-Tim

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