Porting throttle body

[mikewohlford]

Sorry if this particular topic was discussed earlier, but I am a machinist and am currently porting my throttle body for my 3.4L grand am. I am cutting the diameter alittle smaller than the typical 62MM aftermarket body. I am getting alot of crap from people at work who work on cars and stuff saying that my computers and sensors are going to go crazy and I will screw everything up. I just need to CNC machine the butterfly in the next day or so. I am looking around the Internet and it doesn't say anything about the sensors messing up with more air flow. Will everything be OK? Anyone care to comment? Thank you.

[xeroinfinity]

Shouldnt hav any trouble. I hav a 62mm TB and when I installed it I didnt do anything weird causing great concern.
ITs more like taking off a 2barrel carb and puting on a 4barel. Just more air, which you cars MAF should pick up on it and adjust things its self.

But a modification to the Pcm will alow you to tune it a bit, to get the max HP gains.

So you milling out the TB, or you doing it by hand with a die grinder? Just wondering.
The trick is geting the butterfly just right, Good Luck.

[maxwedge]

The shape of the throttle body opening should stay consistent with the stock configuration, so try and follow the original contour when machining this. Keep in mind any increase in performance will be realized at high rpm under maximum air flow demands, over done this can hurt low speed mid range throttle response.

[mikewohlford]

xeroinfinity,

I am using a boring head on a CNC HAAS to bore out the TB. Nothing done by hand here to bore it out. So far, that is done. I have to extend the length of the slot on the shaft that the butterfly slips into to accomodate the bigger diameter of the butterfly Im going to machine sometime this week.

Thanks for the quick responses guys. I hope things turn out great so I can tell the 5+ guys at work that they were WRONG!!!. Haha.

[xeroinfinity]

Kool Kool! Sounds like you about there

Have a laugh on them, cause you will be fine.

[mikewohlford]

I finished my throttle body and put it back on. Starts fine, sounds good, no alarms, errors, nothing. Rides good too. Those guys at my work are idiots. Im going to give them some crap monday. Let me tell you one thing. If you take on this job, and someone tells you that you are going to screw stuff up and they never owned a grand am, ignore them. You have my vote if you get a 62MM throttle body. As long as you know what you are doing. I was told a few things I didn't know that I could have messed up, but as far as the "your an idiot" part, screw them.

[maxwedge]

You are right, any increase in airflow is recognized ,to a point, by the maf.

[xonelith]

Good Job! Glad it all worked out.

Keep in mind though, you still have quite a few limiting factors, mainly your Upper Intake Manifold. You should also port that out for 62mm, to match the TB.

Also, I"m not sure what the opening size of the MAF is, but that could also be limiting. Option here is to get an LS1 MAF or at least something bigger (requiring custom tuning).

Finally, do you have a CAI? or the stock airbox? If it's the stock airbox, you won't see much from a bigger TB. If you have a CAI, you'll see more, but the computer will still attempt to compensate for the additional air.

Another thing to keep in mind, the more air you are bringing in (assuming you get tuned), the more fuel you're going to need. If you start bringing in alot of air, you'll probably need to upgrade your injectors.

Next mod will be computer tuning!

Good Luck!

[maxwedge]

Getting in more air is still a function of valve size, cam timing and intake port size, this is the limiting factor in any factory stock non- performance engine.