Wastegate Spring was [MRC Chip = Red Rocket!]

[Ben Swann]

The rating on the spring depends on quite a few variables that result in the
compression force being applied as the wastegate is opening - or how much
force is needed to clamp the cap down all the way.

 

Wire diameter, number of coils, diameter of the spring, and material
(compression modulus) make the spring do its job.  You may even find a 2 bar
spring that is shorter than a 1.8 bar because of the wire diameter or spring
metal it is made of.

 

see: http://www.engineersedge.com/spring_comp_calc_k.htm

 

Basically the spring keeps the wastegate clamped shut until a
counter-opposing force of equal or greater is present - such as boost
pressure regulated by frequency valve or other method.  If the ECU/Frquency
valve is not enough to overcome the speing force you will get overboost.

 

If the spring is sufficient to clamp at a value that the control system will
accommodate, then there is really no problem ( in most cases) with using a
beefier spring.

 

Advantages are: wastegate is clamped sooner/loneger so spoolup is quicker
and also frequency valve assist will help keep boost longer.  This all
depends on how the control system (ECU, freq. valve, pressure regulator,
etc.) is made to work. 

 

So in general the stronger spring is a good thing as it provides additional
assist,  providing it is not overcome the control system.  Don't use a 2 bar
spring on an ECU with a 1.8 bar chip for example.

 

HTH

 

Ben 

benswann at comcast.net

[Date: Fri, 10 Mar 2006 12:30:35 -0500

From: "Postupack, Jeff" <Jeff.Postupack at analog.com>

Subject: [s-cars]  MRC Chip = Red Rocket!

To: <s-car-list at audifans.com>

Cc: barmstea at IBB.GOV

 

Brian, Emre,

 

The 1.8 BAR, or [1.9BAR spring depending on who's Marketing you read] ... is
tempting, Lord knows I've installed one in the '93 and feel the same initial
WOOT! It is a thrill but frankly I don't really know what I am trading off.

 

BTW: The 034efi spring is painted with Yellow markings, Brian and is shorter
than the OEM spring.

 

The beauty of 'Tha List' is the experience and technical analysis that
traverses many years of trial and error, testing and proof. I enjoy that
sentiment because I've found no other 'forum' that blends innovation with
sound mechanical basis. 

 

This experience has saved me from suspect mods that offer low cost MAX gains
at the detriment of the machine. I want to drive my S car a long time so
reliability is paramount. (Should I take that spring outta there and sell
it?)

 

Not to say this WG spring _is_ that suspect, I think the jury is still out!
I don't really have proof in a technical sense. This is similar reasoning to
why 'Tha List' may not endorse TAP methods in a big way.  BTDT, toss it
aside.

 

Before you pop that spring in there and roar around at WOT, I think it might
be beneficial to see who else responds with technical basis. Pro or Con. (No
offense intended Emre!, where's the analysis that might intrigue Mr.
Dawson?)

 

I call to your attention those responding positively WRT to this mod
suggesting it's "choose your adjective" and those who are not.

 

It may be peculiar that Hap, Dawson, Pederson, Payne, Ackley, Charlie Smith,
Trevor, Amoroso, Taka, B Rossato, Elijah and many other people I've come to
respect are not replying. These guys use more than the Butt Test to qualify
a mod.

 

Seems to me that 1.8 BAR spring is changing the feedback control system, and
as such, the ECU should know about it, No? 

 

Hopefully this mod proves harmless because there is a market frenzy buying
these $40 things. 

BTW: About 6 years ago Charlie Smith rolled a few of these springs and
offered them FS at $10. 

My oh my has inflation hit again? Charlie has BTDT. For example, his website
is the source of much history, I want the 'founders' to get the credit here,
not Audiworld.

<snip that bull>

 

Posto]