RE: Turbo/wastegate questions

["Dupree, Jim" <dupree@alldata.com>]

I just bought a 1984 5k turbo engine (Thanks Scott) to go into my 84 4kq and
was wondering what mods are available for this early engine? The intro book
I have on the 84 5k turbo seems to indicate the boost level is controlled
simple by the WG spring tension. The system has a WG valve so the ECU can
open the wastegate to lower the boost if there is knocking and timing has
been reduced to the limit and /or if the engine is overheating. From the
description and hose diagrams it appears the ECU does not actively control
the boost level just reduces boost to compensate for a fault.
If this is the case then a heavier WG spring or a separate boost control
system (such as HKS) would allow me to increase the boost level. I know at
1.6 bar the ECU will shut off the fuel pump, what are the solutions to this?
Does anyone know if the On Board Diagnostic system used on this engine can
be made to work in a 4k. Since it uses the tach as part of the Trouble Code
display I did not think it would work with the 4k tach. 
What wrong with this picture? I just agreed to buy this engine on Wednesday,
it has not even been shipped yet (Scott is probable still packing it up) and
I am already trying to figure out how to modify it!? I haven't even given
Scott the shipping address yet and I won't have time to do the conversion
until this summer.
Just dreaming
Jim Dupree


		-----Original Message-----
		From:	isham-research.freeserve.co.uk@pop.pol.net.uk
[mailto:isham-research.freeserve.co.uk@pop.pol.net.uk]
		Sent:	Thursday, November 25, 1999 4:00 PM
		To:	BSWANN@arinc.com; quattro@audifans.com
		Subject:	Turbo/wastegate questions -  K24, WG Spring
etc.

		> Since I've never actually cracked the wastegate open, are
there any diagrams
		> of a wastegate blowup.  did not find any in Bently or SJM
great site.  How
		> difficult is it really to replace a spring or install a
shim?  I'm willing
		> to try new things, but not if they are likely to cause
irreversable harm.
		> Javads adjustable cap seems to be a pretty good idea, but
I can't even tell
		> how it would work without seeing a full diagram of a
wastgate assembly  Got
		> pictures in my head from what everyone's saying, but..any
diagrams?

		No, fiddling with the top of a wastegate is easy and utterly
risk-free.
		Just unscrew the six nuts and the wastegate cap will slide
up under
		moderate force - easily controlled by an adult hand.
Shimming should be
		done in 1mm or 0.5mm steps - a stock ECU boost cut-off is
quite sensitive.
		I've seen several cars where 2mm was too much for the stock
ECU.

		> Regarding Phils last comments though.  Have I lost some of
my low end boost
		> by Bypassing WGFV with pressure regulator which I
understand is a popular
		> and inexpensive mod.  Would it benefit to tee the original
line back in
		> using a one way valves so you get the vacuem lift on the
low end,  and the
		> needed bypass on the high end(trying to explain what I
think againg without
		> actually knowing what one of these looks like taken
apart).

		No, don't mess with it.  Under WoT the ECU is very active in
managing
		boost - any non-linearity you introduce will defeat its
efforts.

		> My apologies to those who sell the mod kits by the way, as
I'm sure they are
		> worth it.  Some of us just can't afford or justify
expensive chips, new
		> turbos and the like.  I'm not a racer, don't have the
money or time - maybe
		> some day.  Just want to get the best performance available
without spending
		> more than the car is actually worth.   I learn from the
expert advice on
		> this list and other sources, and then I'll apply what I've
learned if
		> prudent as a home mechanic/hobbyist.

		I don't think the ECU/spring modifications, as produced and
sold by
		various parties in the USA, are 'expensive'.  For one thing,
they're
		100% reversible - not the case with, e.g., hybrid turbos and
ported
		heads.  In my experience, most buyers want stock cars -
highly modified
		ones are very hard to sell.  Secondly, these modifications
retain the
		best attributes of the car - especially its driveability.
I've just
		bought Scott Mockry's MAC14 kit (despite being quite capable
of burning
		chips myself) for this reason - I will be able to sit in
High Street
		traffic and not stand out, but I'll still be able to burn
off BMW M3s.

		As regular readers will know, I _love_ stealth.  Enquiries
at VAG UK
		have revealed that my MC-2 MAC14 Type 44 quattro Avant is
one of _FIVE_
		imported to the UK in 1989/90.  I've taken the badges off
the back and
		replaced them with:

		           "Audi 100 CC         oooo           Avant"

		Which is the badging for the base non-turbo non-quattro
model - they
		sold several thousand of _those_.

		--
		 Phil Payne
		 UK Audi quattro Owners Club
		 Phone +44 7785 302803  Fax +44 870 0883933