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Re: wg spring in mc turbo
In a message dated 11/23/1999 "Buchholz, Steven"
<Steven.Buchholz@kla-tencor.com> wrote:
<< While there isn't necessarily anything wrong with putting a stiffer spring
into the WG on an MC engine, there is one caveat to be aware of. The way the
system is designed, the ECU can attempt to reduce the boost using the WGFV if
it detects knock when the timing is backed all the way down. The benefit of
the stiffer spring is that short bit of extra force when the turbo is
spinning up, which will give a little bit better lag performance, but I
wonder if anyone has actually quantified the difference. >>
I have not quantified the difference with anything but eyeballs on the boost
gauge and seat of the pants, but here is what I have experienced.
I have the QLCC code that controls boost via the WGFV. I use this with Scott
Mockry's 1.8 bar spring (according to Scott is very similar to the "Charlie
Spring" which I noticed he is again offering a few remaining ones of...).
With the O.E. spring I was not able to achieve high boost levels
consistently. I believe this was because the O.E. spring had gone soft.
Initially I used Scott's 1.6 bar spring (now donated to Wolff's car). While I
was always able to achieve max boost with the 1.6 bar spring, I opted to try
Scott's 1.8 bar version when he offered it. There is a very noticeable (and
positive) difference between his 1.6 and 1.8 bar springs in my car running
the same ECU code.
As far as margin of safety goes, Scott explained to me that the first line of
defense the ECU does are three steps of fuel mapping/timing retard, then
boost is reduced. He further explained that the WGFV is capable of pushing
the spring back a tenth or two of a bar so that there is really not much more
risk in running the 1.8 bar spring vs. the 1.6 bar spring. Also that the
check engine light should blink if the ECU goes full retard and attempts to
lower boost. (And yes, my check engine light does work because I have pulled
codes to test it.)
This is all recollection and I am not an expert in this. Scott, and others,
please correct me if anything I stated above is incorrect.
This all said, despite there never being any apparent timing retard, no codes
ever set, no blinks of the check engine light, and good running
charactoristics/performance, I have been fighting a pinging problem off and
on for some time now. Seems to get better with some batches of fuel, worse
with others. Seems to be at it's worst around 1.5 bar on the dash display and
goes away at maximum boost. Gets better with fresh plugs too. I realize I am
taking my chances and do back off if/when pinging occurs. Any advice in this
area (aside from leaving the state of crappy gas) will be greatly
appreciated. Note that this is a ping, not a knock, but still a valid concern
on a boost modded engine I'm sure.
My long and wordy .02 worth...Happy Thanksgiving all!!!! (In the US at
least...)
Mike Veglia
87 5kcstq