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S4 throttle body butterfly thoughts

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Old 01-08-2018, 10:48 AM
  #1
Marti
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Default S4 throttle body butterfly thoughts

Hi

I was looking for feedback on increasing the size of the throttle body butterfly on the S4/GT/GTS inlet manifold for a S4 engine running the Colinĺs cams and MSMD headers with a X pipe and remaining exhaust system being standard. The car is also running shark tuner and uprated injectors.

As bolt on replacement performance manifolds are not quite there yet I am working on modifying the S4 manifold to clean up the airflow as best I can which I hope will help. I am trying to investigate options on fitting a larger butterfly. I believe the existing butterfly is 75mm and some people have increased this size, i would like to know what size is possible and where parts are sourced

I am working on the theory that with the increased airflow now being sought by the engine that this may be worth doing especially since I have the parts off the car at present.

Many thanks
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Old 01-08-2018, 11:53 AM
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SwayBar
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With those cams, x, and proper tune, you can expect 330+ rwhp with a 5-speed.

However, after reading many threads on this topic, as well as being in-process of mocking-up an intake, I wouldn't waste any time/money on the stock intake, including a bigger TB.

Runners 5 and 8 are mangled beyond repair with their 180 degree bends. Runners 2 and 6 flow the best, thus run the leanest for batch fire, and everyone is forced to tune for them which includes pulling timing to minimize knocking on those cylinders. Lots of hp is left on the table as a result.

IMO, this knocking is the root cause of 2/6 bearing failure on the 32v, and not the oiling system.

A completely new intake which allows all cylinders to fill equally will enable a much more aggressive tune while being safer at the same time.
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Old 01-08-2018, 12:27 PM
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Don't forget to polish your plate...
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Old 01-08-2018, 01:15 PM
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https://rennlist.com/forums/928-foru...ughout-30.html
https://rennlist.com/forums/928-foru...reets-118.html
I made a larger number of 80mm butterfly valves for Tuomo (Ptuomov). He might sell you a valve. He has got all the tooling for the machining of the throttle valve housing.
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Old 01-08-2018, 01:19 PM
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V2Rocket
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http://www.maxbore.com/

like $120, quick turnaround, nice work.

i had a 944 TB taken from 55 to 60mm there.

i had a 928S3 tb in hand a while back, it looked like it could go bigger (80?)
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Old 01-08-2018, 05:13 PM
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Originally Posted by V2Rocket View Post
http://www.maxbore.com/

like $120, quick turnaround, nice work.

i had a 944 TB taken from 55 to 60mm there.

i had a 928S3 tb in hand a while back, it looked like it could go bigger (80?)
Have you asked him to do 928 S4 tb?
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Old 01-08-2018, 05:41 PM
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no but the hole should drill the same despite the weird shape of the S4 TB "housing"

they did somebody's 928 TB up to 82mm (1/3 down)
http://www.maxbore.com/europeanpictures.html
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Old 01-08-2018, 05:44 PM
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Sterling did his a good sized larger than stock. Once he changed up to ITB's he sold his to Roger and I installed it in his GTS. Would like to have one for my car also.
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Old 01-08-2018, 05:54 PM
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Originally Posted by SeanR View Post
Sterling did his a good sized larger than stock. Once he changed up to ITB's he sold his to Roger and I installed it in his GTS. Would like to have one for my car also.
The problem is that just replacing the throttle valve isn't going to increase flow much. And neither does just welding and porting the throttle body without replacing the valve. One needs to do both, and that's extremely time consuming. Then, there's the flow demand chart that lists how much hp one should expect to gain from the change, which isn't much for near-stock motors. Take a look at what Ake posted in two threads on this, plus my estimates of hp gain.
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Old 01-08-2018, 05:56 PM
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Originally Posted by V2Rocket View Post
no but the hole should drill the same despite the weird shape of the S4 TB "housing"

they did somebody's 928 TB up to 82mm (1/3 down)
http://www.maxbore.com/europeanpictures.html
His setup can't do a S4 throttle body. I asked.
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Old 01-08-2018, 05:58 PM
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SeanR
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Originally Posted by ptuomov View Post
The problem is that just replacing the throttle valve isn't going to increase flow much. And neither does just welding and porting the throttle body without replacing the valve. One needs to do both, and that's extremely time consuming. Then, there's the flow demand chart that lists how much hp one should expect to gain from the change, which isn't much for near-stock motors. Take a look at what Ake posted in two threads on this, plus my estimates of hp gain.

Oh heck with all that. I just want one so I can say "Hey, I've got a large throttle body"
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Old 01-08-2018, 06:01 PM
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Marti
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Originally Posted by SwayBar View Post
With those cams, x, and proper tune, you can expect 330+ rwhp with a 5-speed.

However, after reading many threads on this topic, as well as being in-process of mocking-up an intake, I wouldn't waste any time/money on the stock intake, including a bigger TB.

Runners 5 and 8 are mangled beyond repair with their 180 degree bends. Runners 2 and 6 flow the best, thus run the leanest for batch fire, and everyone is forced to tune for them which includes pulling timing to minimize knocking on those cylinders. Lots of hp is left on the table as a result.

IMO, this knocking is the root cause of 2/6 bearing failure on the 32v, and not the oiling system.

A completely new intake which allows all cylinders to fill equally will enable a much more aggressive tune while being safer at the same time.
I generally dislike the standard S4 manifold to, however until there is a ready replacement for it I can only really tinker with this to make what ever improvements possible. I am hoping GB will move to some limited production version of the manifolds he has been testing
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Old 01-08-2018, 06:03 PM
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Originally Posted by SeanR View Post
Oh heck with all that. I just want one so I can say "Hey, I've got a large throttle body"
Now, I do understand and approve of that motivation!
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Old 01-08-2018, 06:03 PM
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Originally Posted by SwayBar View Post
Runners 2 and 6 flow the best, thus run the leanest for batch fire, and everyone is forced to tune for them which includes pulling timing to minimize knocking on those cylinders. Lots of hp is left on the table as a result.

IMO, this knocking is the root cause of 2/6 bearing failure on the 32v, and not the oiling system.
Basic by-cylinder retard tuning patch (for ST.BINs):
https://rennlist.com/forums/928-foru...ard-patch.html
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Old 01-08-2018, 06:16 PM
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Hereĺs what I believe. The 928 cylinder filling and temperatures are different depending on whether one runs stock exhaust manifolds or long-tube headers. Most of the filling imbalances, residual gas fractions, AFR variations, and timing requirement differences are caused by exhaust blowdown interference inside the stock exhaust manifolds. The original poster in this thread will run headers so most of the imbalances at peak power will be automatically resolved by the headers. At mid range rpms, Iĺd expect the long intake runner cylinders (2, 3, 6, and 7) to fill a little better but at peak power the intake runner length shouldnĺt be cause a huge imbalance. Opinions vary on this, of course.
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