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Old 03-16-2010, 04:57 AM   #1
Loafer987
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How big of Throttle body is too big?

Hello again everyone! I am running an H23A vtec (blue top) and I am just curious... I found a wicked deal on a skunk 2 intake and modded throttle body. however the throttle body is 77mm and the intake is portmatched to it. If I was to buy this setup I realize I will need tuning, but is this throttlebody too big for a stock motor? I do plan to upgrade to the Type-S cams eventually. This setup would haul ass for a boosted H22A but I don't know if this may be overkill for my stock N/A motor. Let me know what you think.

I will probably pick up this package cheaper than I can buy a 70 mm throttlebody for my stock intake so keep that in mind when dropping your input.

Thanks!
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Old 03-16-2010, 08:54 PM   #2
jdmwannabee
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it's about 3"
if you got a tune you would make decent numbers.
if it's for a steal, pick it up.
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Old 03-16-2010, 09:06 PM   #3
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Truly determining the ideal throttle body size is rather involved. Too small and you are choking the motor and too large, you are reducing velocity and possibly causing cavitation in the plenum.

A larger than stock throttle body will usually give better throttle response, because stock throttle bodies are often restrictive, but 77mm is massive, so I'd be concerned that its too large.

77mm is about 3 inches as mentioned, and most people with h22, or h23 engines use a 3 inch diameter intake. You want a slightly smaller throttle body diameter than your intake tubing to create a venturi effect into the plenum.

If the throttle body is larger than the intake, it will act as a diffuser rather than a nozzle, and the mass flow of air being pulled through the runners may be greater than the mass flow incoming, which isn't good.
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Old 03-16-2010, 09:15 PM   #4
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Plans

What are you plans for the motor.

If you are going FI, then 77mm is fine, but it might suck low end until you get the turbo in there.

If you are going NA then 77 is fairly large for an outlet. You should find out if it is 77mm inlet and outlet, or if it is tapered.

If you are going NA, then I would recommend smaller, I don't know for sure that it will be worse, but it could be.

I am running a 74-68mm tapered and love it, I have no issues what so ever.

EDIT: It may not be a 77mm tb, at least at the outlet, as the skunk2 website says 75mm is the largest bore they recommend on their h22 manifold...

If you can go get a digital caliper and measure it. People are full of shit

Last edited by Ghetto_CB7; 03-16-2010 at 09:19 PM.
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Old 03-17-2010, 03:19 AM   #5
Loafer987
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this is definately 77mm. i think i might be better off with a 70 mm or so on my motor. I think i am running a 65 right now which is stock on the H23A Vtec. it does taper and mate the intake almost perfectly though...
I can't really afford it right now anyways so I hope someone on here can pick it up.

http://cgi.ebay.ca/Skunk2-AEM-B-M-Ho...item4cee214c7a
I hope that gets you to it properly. Good luck guys. Someone will get a sick deal on a killer FI setup.
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Old 03-17-2010, 03:23 AM   #6
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77mm is HUGE. You'll probably end up losing power if you're going NA.
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Old 03-17-2010, 10:15 AM   #7
Ghetto_CB7
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...

Find out the inlet size of the manifold.

If it is 77 tapered to something reasonable, you may be ok na, however if it is 77 to 75 it will most likely be a little big for na.

If it is tapered to like 70 then you should be ok.

If he says it is 77 at the inlet of the manifold, I would not buy it, since the guy is either lying, or was an idiot and had had a max bore 75 mm manifold bored to 77 and probably screwed up some iacv ports.

Find that out first...
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Old 03-17-2010, 01:07 PM   #8
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i say buy it and go turbo!
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