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BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Powertrain and Drivetrain Discussions > NA Engine (non-turbo) / Drivetrain / Exhaust Modifications > Throttle Body Size...power gains?



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      07-03-2013, 02:49 PM   #1
cuco
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Throttle Body Size...power gains?

I found this interesting site that calculates the TB size according to engine size/rpm/bore/stroke...etc...this helps determine the correct TB size for engine application, even takes into account if engine has tuned exhaust and cam.

Here's the link:
http://dairally.net/daihard/chas/Mis...8&Button=Reset

I know there is a lot of debate about the power gains, if any, on boring the TB to 79mm (like the Dinan TB). I also found this other site that explains the science behing TB size selection and why sometimes a bigger TB size doesn't yield any gains.

http://www.musclemustangfastfords.co...t/viewall.html

From what I've read, it looks like no one can label that 'x'mm increase in TB size will yield 'x' amount of net hp. The TB power gains depend more on the intake/exhaust CFM capacity, intake air pressure, cam timing and other factors.

Enjoy
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      07-03-2013, 05:33 PM   #2
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If someone wants to figure out the ideal number for our car, I have an extra tb and a lathe so I could bore one out and see if it makes a difference. I probably would just be gains according to the dyno, but it wouldn't take long to set that up
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      07-03-2013, 07:17 PM   #3
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I played with the TB calc for a while and 79mm looks like a good number. My gut feel tells me that a stock car won't see much improvement cause of the intake and exhaust restrictions, but I'm pretty sure there will be a difference felt on cars with headers, 3 stage inake and tune. Also, Im sure Dinan did some research before coming up with that number. Here is a screen shot of the calculated results considering that the engine has a modded exhaust and tuning.

The values at the lower right represent the ID size in mm. The results represent different calculation methods.

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      07-03-2013, 09:13 PM   #4
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Somewhat cheap to check.

Buy salvaged TB
Maxbore.com

Under 350 total cost
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      07-03-2013, 09:54 PM   #5
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I got one attached to my three stage. The thing Im worried about is getting an error or something because i would have to take it apart to get the throttle off the bore the whole way through
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      07-03-2013, 10:36 PM   #6
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Rb

[quote=SDemetris;14266684]If someone wants to figure out the ideal number for our car, I have an extra tb and a lathe so I could bore one out and see if it makes a difference. I probably would just be gains according to the dyno, but it wouldn't take long to set that up[
Never mind

Last edited by 07tundra; 07-03-2013 at 10:45 PM.
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      07-03-2013, 10:42 PM   #7
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Sorry guys I didn't see this was under na. I just hit new post and it was interesting so I posted. Sorry again!
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      07-04-2013, 12:31 AM   #8
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as you guys know me and throwing money at my n52b25. I would probably try this too.
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      07-04-2013, 06:08 AM   #9
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Quote:
Originally Posted by andrey_gta View Post
Somewhat cheap to check.

Buy salvaged TB
Maxbore.com

Under 350 total cost

Wow...compared to the $990 Dinan product.
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      07-04-2013, 07:32 AM   #10
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Quote:
Originally Posted by SDemetris View Post
If someone wants to figure out the ideal number for our car, I have an extra tb and a lathe so I could bore one out and see if it makes a difference. I probably would just be gains according to the dyno, but it wouldn't take long to set that up
If you bore it out, a new, bigger butterfly would have to be made too. I would also compare the ID of the intake hose that connects to the TB. If they matched then I would polish the ID of the TB after boring.

Quote:
Originally Posted by andrey_gta View Post
Somewhat cheap to check.

Buy salvaged TB
Maxbore.com

Under 350 total cost
I checked maxbore.com and it looks like he does the boring/tapering, new butterfly, polish etc.
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      07-05-2013, 01:17 PM   #11
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i have a spare throttle body and plan on having George @ maxbore bore it out. don't expect any noticeable gains, but filing this in the "might as well" category...
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      07-05-2013, 01:47 PM   #12
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Quote:
Originally Posted by cuco View Post
If you bore it out, a new, bigger butterfly would have to be made too. I would also compare the ID of the intake hose that connects to the TB. If they matched then I would polish the ID of the TB after boring.
Actually that is not necessary in our cars since the tb is open all the time. we dont need the plate at all in reality. but for every other car that isnt a n52/n55, yes that would have to be done
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      07-06-2013, 12:08 PM   #13
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Your TB uses a system to hold the butterfly in place that I cannot duplicate.
The TBs I bore use screws and a smooth faced butterfly. Your TB uses slots in the butterfly and what seems like very special clips to hold the butterfly in place.
Sorry I can't work on it.

George
www.maxbore.com
Looks like I get to save my money.
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      07-06-2013, 04:53 PM   #14
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Looks like I get to save my money.
lol figures
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      07-06-2013, 05:02 PM   #15
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Looks like I get to save my money.
Hmm, so it requires some additional machining and fab. Can anyone with a spare TB take it apart and take pictures of the butterfly assembly?
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      07-06-2013, 07:49 PM   #16
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Quote:
Originally Posted by SDemetris
Quote:
Originally Posted by cuco View Post
If you bore it out, a new, bigger butterfly would have to be made too. I would also compare the ID of the intake hose that connects to the TB. If they matched then I would polish the ID of the TB after boring.
Actually that is not necessary in our cars since the tb is open all the time. we dont need the plate at all in reality. but for every other car that isnt a n52/n55, yes that would have to be done
The butterfly serves as a backup in case you have a valvetronics motor failure. I forgot to connect the valvetronic motor wiring after changing my vcg and didn't notice it for a week.
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      07-06-2013, 07:51 PM   #17
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Originally Posted by 07tundra View Post
Sorry guys I didn't see this was under na. I just hit new post and it was interesting so I posted. Sorry again!
Greedy motherFer. Already wanting more power lol
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      07-06-2013, 09:29 PM   #18
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Me wants more!! I think it wld be worth looking at
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      07-06-2013, 10:16 PM   #19
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no need to upgrade a throttle body on a n/a engine unless you have internal upgrades to support. you will see no power gain. it will feel different since it is the throttle you are messing with
a but there is no need to introduce a larger volume if your engine is not calling for it. if you had to drink a mcdonalds milk shake from a cup would you be able to get more out with a straw with a hole the size of a half dollar? would you be able to get more tasty beverage in faster? or would you have to pull harder and most likely get less. i cant think of one na car bmw or others ive worked on where the throttle body unlocked power unless compression was increased. s
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      07-07-2013, 07:29 AM   #20
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The butterfly serves as a backup in case you have a valvetronics motor failure. I forgot to connect the valvetronic motor wiring after changing my vcg and didn't notice it for a week.
Hmm, im not familiar with this, I'll have to dig in. So is the buttefly open all the time when the valvatronic motor is connected?
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      07-07-2013, 01:50 PM   #21
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no need to upgrade a throttle body on a n/a engine unless you have internal upgrades to support. you will see no power gain. it will feel different since it is the throttle you are messing with
a but there is no need to introduce a larger volume if your engine is not calling for it. if you had to drink a mcdonalds milk shake from a cup would you be able to get more out with a straw with a hole the size of a half dollar? would you be able to get more tasty beverage in faster? or would you have to pull harder and most likely get less. i cant think of one na car bmw or others ive worked on where the throttle body unlocked power unless compression was increased. s
Wouldn't a wider TB combined with a tune be beneficial though?
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      07-07-2013, 02:04 PM   #22
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Wouldn't a wider TB combined with a tune be beneficial though?
go over post #1, #3 and click on the links, I don't want to turn this thread into a "is it beneficial or not" discussion.
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