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Smart quod bastardus
 
fredmeister's Avatar
 
Join Date: Oct 2002
Location: Baltimore, MD, USA
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Quote:
Originally Posted by 911nut View Post
All you experts are avoiding answering one question: If a shorter spring is a stiffer spring, why is the .8 bar factory spring longer than the .7 bar factory spring?

So, whoever thinks they can explain the in's and out's (and I don't mean providing links to other pages; do it in your own words) of spring mechanics to us all, have at it.
Simple answer from one of the experts.....
Stiffness and force are 2 separate issues. When you increase the wastegate blow off or opening pressure you are increasing the force acting on the wastegate diaphragm via the spring inside the housing. How you get there is the question. You can get the same force from 2 different springs of different stiffness by compressing them different amounts via Hookes Law.
You need to look at all the dimensions of the spring not just its uncompressed length to determine the end result of the force it exerts when compressed in the housing. This cannot be explained easily without looking at the equations and having an understanding of what is going on in the wastegate design.
My original response early on was not meant to insult or hurt feelings but was said in order to prevent the author of this post from doing lots of expensive damage...if I did not care to help I would not have said anything at all.
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1979 930 Turbo....3.4L, 7.5to1 comp, SC cams, B&B intercooler, Snow Perf water/meth injection, Rarlyl8 headers, Garret GTX turbo, 36mm ported intakes, Innovate Auxbox/LM-1, custom Manually Adjustable wastegate housing (0.8-1.1bar),--running 0.7bar max
---"When you're racing it's life! Anything else either before or after, is just waiting"
Old 02-22-2009, 06:38 PM
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Spring length also has to do with preload. You want the wastegate valve closed "hard" against its seat otherwise it will leak. If you cut down the spring length, you reduce the preload and the valve seat pressure will be less when it is closed.

Now, if you cut the spring down and then manage to stretch it back to its original length (about 6 3/4" in my wastegate) then you have reduced the number of effective or active coils. With less coils to bend, the spring is now stiffer because it has to move each coil farther in one inch of movement. More lb/in.

Mark
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Old 02-22-2009, 07:11 PM
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UNDER CONSTRUCTION!
 
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bingo

i think preload is the over looked factor here. im no expert but reading through all this preload kept comming up in my mind. with less preload wouldnt you in theory need to move the spring less than a longer one to open waste gate and start to dump its boost there for creating a leak sooner not allowing it to ever reach .8 bar.

ed
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Old 02-22-2009, 08:16 PM
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Would a Tial spring work in a stock waste gate?
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Old 02-22-2009, 08:43 PM
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Quote:
Originally Posted by fredmeister View Post
Simple answer from one of the experts.....
Stiffness and force are 2 separate issues. When you increase the wastegate blow off or opening pressure you are increasing the force acting on the wastegate diaphragm via the spring inside the housing. How you get there is the question. You can get the same force from 2 different springs of different stiffness by compressing them different amounts via Hookes Law.
You need to look at all the dimensions of the spring not just its uncompressed length to determine the end result of the force it exerts when compressed in the housing. This cannot be explained easily without looking at the equations and having an understanding of what is going on in the wastegate design.
My original response early on was not meant to insult or hurt feelings but was said in order to prevent the author of this post from doing lots of expensive damage...if I did not care to help I would not have said anything at all.
And I appreciate all the help offered I apologize if I ruffled any feathers I thought nobody was taking me serious with this project. I am bolting on the turbo as we speak and will start this thing up this summer. All of the advise given resulted in me getting a tial wastegate. To answer another question I think that a tial spring could not work properly in a stock wastegate because it would not seat properly ie a smaller spring.
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Old 02-23-2009, 02:55 AM
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Guys, not to whip a dead horse, but fredmeister went out of his way for me a while back
identifying boost springs and believe his findings would shed light here with his experiments for future
reference when new owners come on board.

Thanks again fred!

Boost springs

gsmith, kudos on the Tial!
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Old 02-23-2009, 07:09 PM
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Smart quod bastardus
 
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Your welcome Cl8ton. Thanks for the complement.
I did not even think to post my original link as I am very busy and figured people would have come across that in searching the boards.
I am glad I could help you out and hopefully my advise helps out gsmith660.
Getting info from the internet is always a gamble because you gotta realize lots of people chime in and info is not always correct. Trick is to weed out the good with the bad info.
I am an mechanical engineer by trade and know a little about springs as I do it all day here in Detoit metro. Also do all my own work on my 911 and 930 including engine builds. Just don't ask me about painting or welding or how to avoid speeding tickets.
See ya
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1979 930 Turbo....3.4L, 7.5to1 comp, SC cams, B&B intercooler, Snow Perf water/meth injection, Rarlyl8 headers, Garret GTX turbo, 36mm ported intakes, Innovate Auxbox/LM-1, custom Manually Adjustable wastegate housing (0.8-1.1bar),--running 0.7bar max
---"When you're racing it's life! Anything else either before or after, is just waiting"
Old 02-24-2009, 10:16 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #47 (permalink)
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If I ever ask a question about boost springs will someone please remind me
of this post. It must be time for a pill.

Cole
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Old 02-24-2009, 11:04 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #48 (permalink)
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Thanks your help was useful Fredmeister, cole930 you need more than a pill. LOL
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" Porsche there is no substitute" I always liked that saying. Air cooled is the only way to go!
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76 Blazer also restored by me
Old 02-24-2009, 01:07 PM
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this thread has gotten boring,,, let's spice it up gsmith,, have you picked a boost controller yet ??
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Old 02-24-2009, 01:24 PM
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Yeah it will be one of these. http://www.boostcontroller.com/index.php?category=35
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" Porsche there is no substitute" I always liked that saying. Air cooled is the only way to go!
76 911 C.R.A.P. Gruppe #2 BIG time TURBO C.R.A.P. Bitz EFI/EDIS Now MegaSquirt 3
76 Blazer also restored by me
Old 02-24-2009, 01:32 PM
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And after the black particle thread one of these. http://www.system1filters.com/oil_filters.htm
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" Porsche there is no substitute" I always liked that saying. Air cooled is the only way to go!
76 911 C.R.A.P. Gruppe #2 BIG time TURBO C.R.A.P. Bitz EFI/EDIS Now MegaSquirt 3
76 Blazer also restored by me
Old 02-24-2009, 01:33 PM
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What not exciting enough? Well how about this http://www.msdignition.com/Products/Ignitions/6530_-_MSD_Digital_Programmable_6AL-2.aspx
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" Porsche there is no substitute" I always liked that saying. Air cooled is the only way to go!
76 911 C.R.A.P. Gruppe #2 BIG time TURBO C.R.A.P. Bitz EFI/EDIS Now MegaSquirt 3
76 Blazer also restored by me
Old 02-24-2009, 04:12 PM
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what? me worry?
 
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Those System1 filters are really good...Have used them.. I also like the offerings by http://www.cmfilters.com/
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Old 02-24-2009, 04:24 PM
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The system 1 has a reusable screen good for 75 microns I am going to put it in between the turbo and the sump to prevent any coking from going thru the scavenge pump.
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" Porsche there is no substitute" I always liked that saying. Air cooled is the only way to go!
76 911 C.R.A.P. Gruppe #2 BIG time TURBO C.R.A.P. Bitz EFI/EDIS Now MegaSquirt 3
76 Blazer also restored by me
Old 02-24-2009, 04:45 PM
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