Best Size T/B?


coolkidirish

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I'm looking for a bit of advice here, what do you think...

So im running a B18C Type R with a Mugen air box, ITR T/B, skunk2 inlet, spec 3 Buddyclub cams, PLM RMF Manifold which is 2.5" at flange and then a 70mm Skunk2 Catback

I have a brand new skunk2 pro series 68mm T/B lying around and im thinking of putting it on but half paranoid I could lose power? What ya think?

After a map could i potentially regret it do you think?
 


KieranEG6

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Would still say standard 62mm ITR body would be best suited for your setup.

As a rough quick guide I found on the net. Your intake system needs to flow 1.5 CFM per engine horsepower, and your exhaust system needs to flow 2.2 CFM per engine horsepower.
 


firebass

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if u read here the sticky threads they say that the intake tubes should be bigger than the exhaust ones , make the calcs and u ll get your answer !!!!
 


coolkidirish

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Would still say standard 62mm ITR body would be best suited for your setup.

As a rough quick guide I found on the net. Your intake system needs to flow 1.5 CFM per engine horsepower, and your exhaust system needs to flow 2.2 CFM per engine horsepower.
Hi Kieran,

Is there a calculator or something online that helped you calculate that? If so do you have a link by any chance? I wouldn't mind trying it out to try and see what would be the best set up?

Thanks
 


KieranEG6

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How To Calculate Muffler Size and Exhaust Pipe Diameter | Exhaust Videos

Thats the link I found a while back researching exhaust sizes. As it explains quite plainly why the intake is smaller than the exhaust in terms of diamiter and flow ability's. An intake is flowing ambient air at average temperatures where as an exhaust has to flow the same air that has just been considerably heated up under combustion, will have expaneded a fair bit, thus why your exhaust is generally wider than your intake. As after combustion it has to flow the volume of air that was inducted but that has now increased in size. So a larger volume of air.

People bash big 3" bore exhaust systems as being to big for N/A constantly on these forums but rave about big ass throttle bodys being great??.... :angry2:

When you break it down and think about what an engine is and does at each end it does become quite simple. Generally manufactures have already done all the R&D when it comes to these things.

Think of your intake manifold and TB as your Exhaust manifold both are what control aspect characteristics of the engine (To an extent).

I should find some links to these things, as I seem to have to quote them so often. Consider the fact that the Mugen 270hp K20 runs a 64-65mm TB. Surely if a bigger TB was benificial in any way would they have not used one???..... Many more examples like even the toda racing TB for race trim 300hp FD2's is only 66mm. Pretty sure toda KNOW their **** when it comes to tuning Vtecs and its not like they are keeping the TB small to make them economical or anything hahaha
 


Lee s

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My spoon tb is 70mm - more flow and manufacturer type reliability, looks boring though.
 


KieranEG6

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My spoon tb is 70mm - more flow and manufacturer type reliability, looks boring though.

Spoon TBs are 62mm at the butterfly. In fact they are just standard DC2 TB's with a tapper port on the inlet openning from approx 67-68mm out to 70mm to aid velocity as air enters.
 


coolkidirish

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How To Calculate Muffler Size and Exhaust Pipe Diameter | Exhaust Videos

Thats the link I found a while back researching exhaust sizes. As it explains quite plainly why the intake is smaller than the exhaust in terms of diamiter and flow ability's. An intake is flowing ambient air at average temperatures where as an exhaust has to flow the same air that has just been considerably heated up under combustion, will have expaneded a fair bit, thus why your exhaust is generally wider than your intake. As after combustion it has to flow the volume of air that was inducted but that has now increased in size. So a larger volume of air.

People bash big 3" bore exhaust systems as being to big for N/A constantly on these forums but rave about big ass throttle bodys being great??.... :angry2:

When you break it down and think about what an engine is and does at each end it does become quite simple. Generally manufactures have already done all the R&D when it comes to these things.

Think of your intake manifold and TB as your Exhaust manifold both are what control aspect characteristics of the engine (To an extent).

I should find some links to these things, as I seem to have to quote them so often. Consider the fact that the Mugen 270hp K20 runs a 64-65mm TB. Surely if a bigger TB was benificial in any way would they have not used one???..... Many more examples like even the toda racing TB for race trim 300hp FD2's is only 66mm. Pretty sure toda KNOW their **** when it comes to tuning Vtecs and its not like they are keeping the TB small to make them economical or anything hahaha
good points, and that link you gave me is a great read:nice:
 


Burny

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Have you decided to do it mate? Im in the same boat as you i also have a b18c, mugen airbox and other bolt ons. I had a skunk2 inlet and TB on my old B16B and that thing flew! Surely with a map there must be more power to be made than over stock..
 


KieranEG6

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Are you serious!!

You do realise the likes of Mugen, Cosworth, Toda have the ability to Map their cars..... So generally if they are only fitting 64mm TB's on engines tuned to acheive 270hp why on earth would any B series running less power and even less CC Need a bigger TB.???
 


Topher-EK9

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I think what Kieran is getting at lad's is that for any of our setups the OEM T/B is absolutely up to the job,

there are many things you can change to get power before worrying about T/B size..

Evidently he knows what he is talking about.. :win: :bow:

If it really was a case of Biggest is best, we'd all have 90mm T/B's ;)

always beats me why, on this forum, someone will offer advise knowing exactly what they are talking about yet still others seem to just Ignore the advise given and plod on regardless


Burny - i am sure your EK9 was fast but we can't go by "i had a skunk2 inlet and TB on my old B16B and it flew" thats not me picking you out bud, but i'm sure you understand what i mean :nice:
 


KieranEG6

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Sorry if I rant about it, but These Big ass TB threads do my nut in. I tend to jump on them as soon as I can before more false info on how mega powerfull they make your car get posted. When In reality they are a waste of money.

The facts are there to see plain as day. If Cosworth/Mugen found that a 64-65mm TB was optimum for a 270hp N/A 2L and Even Toda supply 66mm ones for the likes of 300hp FD2 race cars, then on what planet would a 190-250hp b16/b18/b20 gain power or run more efficiently with a 68-70mm TB.

Really guys don't waist your money.

Cheers Topher.
 


Rich777

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OEM is fine. The throttle body size doesn't work like most people think. You can have the biggest throttle body in the world, but unless the manifold and head can flow as well you're waisting your time.
 


kulo

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I had a maxbore.com tb
65 at the plate tapered to 70mm
 



Burny

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Yeah ofcourse i understand, however theres pros and cons. Ive read threads on this forum saying stock intake pipes are good, the 3" intake pipe was the best mod i ever done!
 


KieranEG6

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Yeah ofcourse i understand, however theres pros and cons. Ive read threads on this forum saying stock intake pipes are good, the 3" intake pipe was the best mod i ever done!

Based on what??!!!! Define "Best" ??

Proven gains or just made your Vtec megaa!!!

Im yet to see any proven Pro's to fitting a substancially bigger TB to any N/A B series running mild power.
 


W80 YAU

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So Kieran, would you say a bigger tb is fine for a boosted engine??

I have a Skunk2 inlet with skunk2 tb (either 68 or 70mm, cant mind) for my boosted c4.
My mechanic hasn't really said anything so far regarding skunk2 tb being too big so im presuming that will be fine then??
 


tama666

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OEM is fine. The throttle body size doesn't work like most people think. You can have the biggest throttle body in the world, but unless the manifold and head can flow as well you're waisting your time.

^dead on!
Unless the head is professionally worked keep it stock.
 


Burny

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Based on what??!!!! Define "Best" ??

Proven gains or just made your Vtec megaa!!!

Im yet to see any proven Pro's to fitting a substancially bigger TB to any N/A B series running mild power.

I completely see where your coming from, but im not one of those people that think "bigger is better". However a 3" intake pipe gave me an extra 5mph top end speed on a 1 mile straight stretch of road.
 


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