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tial WG but what spring?

my wastegate is bad. i am going to buy a tial F46 but i have read that i should use a lighter spring if i have a header and free flow muffler.
i also have a "dial O death" knob installed.
i am looking at 2 options.
1. run .8bar with maybe going up to .9.
with the DOD i could fine tune the pressure to .8 and lock it down.

2. have the option to drop it down to .6 or up to .9. not sure why i would drop it down, just thought the option might be nice.

i have a RUF boost gauge installed where the clock was.
i dont know how much range the DOD will give me since the WG was bad when i bought the car.

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Old 06-03-2013, 07:42 AM
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In a nutshell:
With the DOD installed as you describe you have to install a spring less than the minimum boost you are ever gonna run. So if you want to target 0.8 bar use the 0.6bar spring and make up the remaining 0.2bar with the DOD.
Running a 0.9bar spring will never allow you to go less than 0.9bar....its just the way the wastegate works with your DOD installed correctly.

Fred
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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
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Old 06-03-2013, 01:02 PM
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what about the exhaust system. does a header and muffler change the boost pressure?

if i had a .8 bar spring giving me .8 bar of boost with a stock engine, does a .8 bar spring give me more boost with a free flowing exhaust.
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Old 06-03-2013, 01:43 PM
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Quote:
Originally Posted by fredmeister View Post
In a nutshell:
With the DOD installed as you describe you have to install a spring less than the minimum boost you are ever gonna run. So if you want to target 0.8 bar use the 0.6bar spring and make up the remaining 0.2bar with the DOD.
Running a 0.9bar spring will never allow you to go less than 0.9bar....its just the way the wastegate works with your DOD installed correctly.

Fred
Exactly.

As to his questions re: higher boost, the answer is no...free flowing headers and mufflers don't in and of themselves result in boost beyond the spring setting of the WG....but may result in boost spikes on occasion, depending on a lot of things. I would start with a .6 spring if the intention is to use the DOD, set it for .8bar boost, and if it spikes or creeps beyond that then simply dial it down.
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Old 06-03-2013, 02:01 PM
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Definately go with the lighter spring. I run a 0.6 bar spring with a Hallman DOD and it makes for a very linear and predictable effect.
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Old 06-03-2013, 02:31 PM
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patrick motorsports web site said to get a .3 bar lower spring if you have free flowing exhaust.
this was on tails website:

Note: Boost pressures are only an approximation based on intake manifold pressures equaling exhaust manifold pressure.


i ordered the F46 with a .8 and a .6 spring. $480 total.

was a bad porsche WG worth? someone wants mine.
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Old 06-03-2013, 04:07 PM
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RUF put a .6BAR spring with DOD and it gives .9BAR with boost dialed all the way in. For everyday street use you are pretty safe with a stock intercooler at .9BAR. My understanding is that much more than .9 and you will want a bigger intercooler.

My experience with upgrading to a B&B Headers/Exhaust with the wastegate is that it will still open at the prescribed presure corresponding to the boost as it did before the free flowing headers and exhaust. You should get there quicker though.
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Old 06-03-2013, 06:19 PM
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i have the RUF IC but it needs to be sealed up around the tail/decklid. i was planning on a post for this. there are also some holes in the engine tin i would like to seal up. i am losing a lot of airflow around the IC plus i am pulling some hot air from under the engine. i think i can make some plugs for the tin, but the IC seal is going to take some more thought.

.9 max would be good. i was thinking about it coming in this morining. i may have the .6 installed. if someone else ever drove the car i can turn it down. plus if i ever track it i can turn it down until i get a better feel for the car. another bonus is hearing the wg open more.
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Old 06-04-2013, 02:42 AM
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been thinking about the exhaust flow and WG spring thing.

the spring is pushing the valve closed. that is a constant. the boost pressure from the IC is trying to open the valve, BUT....what about the exhuast pressure on the bottom of the valve?
thats pushing up on the valve trying to open that too, no?
so if the exhaust flows more freely out of the muffler then there is less exhaust pressure under the valve pushing it open thus requiring MORE boost pressure from the IC to open the WG.
i guess i will find out for sure. i have a .8 and a.6 spring on the way.
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Old 06-04-2013, 08:48 AM
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Quote:
Originally Posted by T77911S View Post
i have the RUF IC but it needs to be sealed up around the tail/decklid. i was planning on a post for this. there are also some holes in the engine tin i would like to seal up. i am losing a lot of airflow around the IC plus i am pulling some hot air from under the engine. i think i can make some plugs for the tin, but the IC seal is going to take some more thought.
.9 max would be good. i was thinking about it coming in this morining. i may have the .6 installed. if someone else ever drove the car i can turn it down. plus if i ever track it i can turn it down until i get a better feel for the car. another bonus is hearing the wg open more.
Here is what I did with mine back in 2009 (hard to believe it has been that long ago) -

Intercooler Shroud - Home Brew !!

Last edited by Ronnie's.930; 06-04-2013 at 05:06 PM..
Old 06-04-2013, 09:09 AM
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Quote:
Originally Posted by T77911S View Post
been thinking about the exhaust flow and WG spring thing.

the spring is pushing the valve closed. that is a constant. the boost pressure from the IC is trying to open the valve, BUT....what about the exhuast pressure on the bottom of the valve?
thats pushing up on the valve trying to open that too, no?
so if the exhaust flows more freely out of the muffler then there is less exhaust pressure under the valve pushing it open thus requiring MORE boost pressure from the IC to open the WG.
i guess i will find out for sure. i have a .8 and a.6 spring on the way.
Now you are thinking and starting to see how the whole system works!

The exhaust backpressure does add to the force slightly opening the valve. But it is negligible to the force from boost on the wastegate diaphragm. Plus it no longer has any effect once the valve cracks open breaking the seal with the valve seat and pressure equalizes on both sides of the valve head.

Fred
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Old 06-04-2013, 09:13 AM
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yea, i just have to take some time to think about things.

thats what i figured, once open the exhaust pressure is no longer an issue.

now my next questions are is the boost pressure the same above the throttle plate as it is below the plate at part throttle.
with my control pressure at 3bar and my AFR at 14.4 at 2500 rpm, am i causing my slight miss?
will it go very lean again if i raise the CP?
this AFM acts or reacts a lot differently to mixture adjustments than my 77s did. its taking some getting use to.
what i have been mulling over as far as the AFM is that with the lower pressure, the plate will be further into the "cone" at 2500 and even though the CP is lower, the plate may not be moving enough to provide the proper mixture. even though the CP has rich end the mixture, how much has the mixture screw compensated for that since i would have to lean it back out enough at idle to get 12.5 far.
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Old 06-04-2013, 04:54 PM
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Quote:
Originally Posted by fredmeister View Post
Now you are thinking and starting to see how the whole system works!

The exhaust backpressure does add to the force slightly opening the valve. But it is negligible to the force from boost on the wastegate diaphragm. Plus it no longer has any effect once the valve cracks open breaking the seal with the valve seat and pressure equalizes on both sides of the valve head.

Fred
Let me chime in, Fred is correct, the exhaust pressure does factor in to the WG's initial valve opening. That's why if you were to bench test your WG, you'll find that (even with a brand spanking new WG) it won't open at the spring rating...be it .8 bar or whatever's in there. It usually takes a few psi more. .8 bar is just shy of 12 psi, and if I recall it took close to 16 psi to open my Tial (I bought it used, so take that into consideration). All of that is factored in when they design the proper spring tension to deliver whatever boost you're after (I got this trinket of wisdom from personal experience when I first got my Tial and decided to test in prior to installation. Freaked out, contacted Tial, and the rest is history).
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Old 06-04-2013, 07:15 PM
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it took about 21psi to open my porsche WG. the spring in it is .207 in thickness. someone said that was a 1bar spring. i never could hit 1bar. i started thinking something was wrong with the DOD, dial o death.
i am going to send it to osiblue. he wants to check it out.
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Old 06-05-2013, 02:53 AM
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Bench testing a wastegate using only compressed air to the inlet port will not yeild true results as there is no exhaust pressure on the valve.
Back pressure from the stock muffler is taken into account with the OEM wastegate spring and will not yield exact results when the exhaust system is altered. The spring used must accommodate the new (different) pressures created by the new exhaust system to remain identical in cracking pressure and full boost pressure.
There is no such thing as a "1.0bar" spring for every application. Close, yes, but not exact.
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Old 06-05-2013, 03:57 AM
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thanks.
what i found out with the compressed air was there is a LOT leaking past the valve guide with the valve closed.
i figured the opening test was not that reliable.
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Old 06-05-2013, 08:11 AM
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Quote:
Originally Posted by RarlyL8 View Post
Bench testing a wastegate using only compressed air to the inlet port will not yeild true results as there is no exhaust pressure on the valve.
Back pressure from the stock muffler is taken into account with the OEM wastegate spring and will not yield exact results when the exhaust system is altered. The spring used must accommodate the new (different) pressures created by the new exhaust system to remain identical in cracking pressure and full boost pressure.
There is no such thing as a "1.0bar" spring for every application. Close, yes, but not exact.
True Brian.
You have done alot of dyno testing and exhaust systems. Can you give a range of exhaust backpressures that we are likely to see in our turbo cars?
Say for a typical upgrade like a set of your headers and a k27S turbo with performance muffler what would the exhaust backpressure be in the manifold at the wastegate?
I am just interested in a ballpark number to see what kind of pressure we should expect. Not having instrumented my exhaust system I have always wondered what type of pressure the turbine housing sees and you might have this info.
How much would changing the performance muffler to a zork change this number as well if you have this data?

Thanks,
Fred
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Old 06-05-2013, 09:08 AM
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i finally got the WG.
i have it in with the .8bar spring installed and only the signal (boost) line connected.

i am getting .9 bar of boost out of it. (i have the RUF gauge installed).

i want to put in the .6bar and connect the dial-O-death (DOD). just to make sure, the tial works the same as the factory WG, i "T" off the sginal line to the WG then to the DOD and back to the TOP of the tial. the only reason i ask is the paper that came with it said the top was a vent.

response is much better. i did not get any major increase in AFR's. it went from 14.4 to 14.3 at 2500. but some other changes made it better.

check my timing thread
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Old 06-13-2013, 04:00 AM
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the .6bar spring did not do what i wanted. minimum boost was .7 and it only adjusted up to barely .8
now i am back witht the .8 spring but the funny thing is it will not adjust. oh well. i may just take the DOD crap out.

so i think there is something to getting a lighter spring than what you want if you have a free flow exhaust. for me it was only .1 bar.
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Old 06-14-2013, 02:40 AM
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That sounds like your DOD is not operational. What type is it and have you inspected all of its components for proper installation/function?

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Old 06-14-2013, 08:06 AM
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