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Best Throttle body for my future setup???

18K views 16 replies 7 participants last post by  0720Steve 
#1 ·
I have a 2008 honda civic Si, I am planning on getting the full race turbo kit with the efr turbo and 4inch CAI. I currently have a skunk2 cai and skunk2 76mm exhaust. I know I will have to lost the skunk2 CAI when I go with this kit which is why I'm getting the 4in full race intake with kit. My problem is I want to buy a throttle body first but don't know what will be best with this kit or what will fit the full race intake when I get it, but be able to use my skunk2 intake in the meantime. This is the kit I'm getting.
http://www.full-race.com/store/turbo-kits/honda-civic-si-k-series-fg-fa-turbo-kit.html
 
#8 · (Edited)
I have a skunk2 throttle body on my turbo fg2 setup. I'm afraid if I go with a oem tb I will loose power so I just kept my ported IM and s2 tb.


But yes get a j37 and big bore coupler skunk2 sells them on ebay. Going all motor on my next car too got a fa5 lucky me.

If you want pm me and I will tell you how to mod your delete maf sensor coupler and toss that restricted air coupler s2 makes.
 
#9 ·
I want to pair the j37 TB with the RRC intake manifold. From what I understand the RRC manifold has a 64mm inlet, and the j37 has a 70mm outlet. I saw an option for the j37 to get it tapered to stock inlet, does that mean the p2r adapter will be 64mm also??? Or how do I go about buying this combo. Also I see everyone getting the 70mm outlet, will that fit comfortably on the RRC Intake manifold without porting or anything else?
 
#10 ·
well if you're gunna get a RRC, find a used TSX tb for cheap to get a couple extra MM on the inlet. i wouldn't bother going J37 unless you plan to bore the RRC out and even then, i don't know it's necessary for a turbo application. i think it would be a waste to pay for a j37, then have to bother with a tapered adapter. RRC for $400ish, and a used TSX tb $100 and you're set. those 2 mate up perfectly.
 
#12 ·
MANIFOLD:
Don't get the SK2 Manifold, in my experience the casting is inferior compared to OEM and you won't make more power. For the same price you could get an RRC intake that far out performs the SK2 manifold on NA motors with bolt-ons.

You may see larger gains on a turbo build because the SK2 intake has a larger plenum volume. Below I added some articles on the RRC:

K-Series Intake Manifold Shootout - Super Street Magazine

JDM Intake Manifold and Kelford Cam Install - Honda Civic - Import Tuner Magazine

THROTTLE BODY:
Your best choice is either the J35 or stock throttle body, the extra aperture you get from a larger TB wont help much since the throttle body is not the most restricting part of your intake system.

If you increase the size of your throttle body too much you lose resolution in metering the amount of air the engine gets. This can cause 'map hunt' at idle where the idle is unstable.

I've got an high compression NA K20/24 with ASP headers, a J35 TB and a SK2 76mm Exhaust so the engine consumes a lot of air. Even so this TB may be too big!

Look at this WOT datalog and XY plot of MAP vs T-plate, watch how quickly the MAP "saturates" to just below atmospheric pressure even at low throttle opening. The MAP pressure also stays relatively constant during the WOT pull.



So your engine doesn't need all that extra throttle body diameter, in fact an incorrectly sized throttle body can lead to higher pumping losses (less efficiency)! If you have a flashpro you can make your own graph and decide if you need a bigger TB.
 
#13 ·
I emailed Vit a while back about his thoughts on TB/ IM as well as Nst pullies. Here is what he said.

"Neither the IM nor TB do anything. The NST pulley is absolute junk as well lol."

my reply

That is interesting you say that. I have read on various forums and seen dynos of results. People are gaining anywhere from 4-8hp with the tb/ manifold port/swap and more with cams. By nothing do you mean minimal gains? A lot of people said they felt a difference after a j35/37 and a port match. Are all of these false or am I missing something ?

His reply back

"People's butt dynos are broken. I've tested those things in detail.. the TB makes 1-2hp, I can stick a fan infront of your intake and make more HP. The pullies never make any power. I can certainly whip out dyno sheets showing that they do, it's not that hard to even unintentionally fudge a pull that shows 4hp. Only time a slightly bigger TB and ported IM help is with a big N/A build. Hell I'm making 900-1000whp on stock intake manifolds & 65mm TB, LOL."

"De Nile" isn't just a river in Egypt. lol. It's the placebo effect, spent $$$ so it's gotta do something. Most "dyno" results you see of those mods online are on a roller, strap down differences and daily conditions can swing power figures a lot higher than you think -- most "tuners" and their customers are clueless (well ignorant really) when it comes to the finer details and will argue a jiggity 3hp on a dynojet print out. lol"


Sounds like the only way you benefit is if you are cammed. I took his advice and saved my money.
 
#14 ·
I've read that too under the knowledge base on his website.

I would caution against blanket statements like "all TB and IM" are junk, but I tend to agree with him in that TB and IM will have more effect on big NA builds. Internal combustion engines are extremely complex systems that are difficult to optimize. When you get into the details its small wonder OEMs typically take 7-10 years developing an engine.

I will say a bigger TB can make your car FEEL faster because it acts like an ON/OFF switch. This might be why some peoples butt dynos are off.
 
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