Bigger Tb

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Senior Member
Sup everyone,
The other day I installed an Erick's Racing 68-66mm TB on my fully built B18C1. I'm currently running a Skunk2 IM. I believe the opening on the IM is 64mm. I know it would have been ideal for me to get a TB that matched the opening of the intake manifold, but I really like the way the Erick's Racing one looks, and I was told that the 2mm difference won't hinder performance. I haven't got my car tuned yet so I can't tell if I gained anything yet. I do know that when I have my stock axle back on, and I engage vtec in 4th gear, I feel like I'm loosing mad power, like my power band completely drops off :eek: !! I was going up the 405N today in SoCali and I downshifted to 4th and when vtec kicked in, I jerked forward in my seat like if I had hit the brakes by accident!! :wtf: :( When I have my full exhaust on, it feels better. I never had this problem when I had my stock TB on. Is it because I have the stock muffler on and the engine is sucking in more air that can be exhausted? Do I just need tuning? Is it because the TB is 2mm bigger than the intake manifold??? :eek:

On a good note, it feels like the car has more power on the top end but just barely. If I am loosing midrange, will I be able to gain it back with good tuning???

If it helps, my mods are
OEM P30 pistons (11:5ish) stock bore
ARP rods/bolts
Micropolished balanced crank
Crower stage 3 cams
P&P head
Skunk2 IM

I realize that I should probably have the intake manifold match ported to fit the TB, but can't afford the downtime.



Super Moderator
ya, i bet its your exhaust that is holding you back, and maybe vtec is kicking in too early. when i put my larger tb on, it felt better to have the vtec engage later. you should get the tb and intake portmatched.


Senior Member
I would definitely consider port matching those parts.

That kick your experiancing could be quite severe. If you downshift suddenly and all the exaust gas can't escape, the pressure could build really high and actually cause a reverse shockwave in the engine. Ie making it almost impossible for your motor to expel exaust gas properly.