75mm TB too much? What MAF to get?

[c.moser]

I just bought a 98 gt convertible a couple weeks ago. It already has a Trick Flow upper intake plenum, BBK CAI, and a BBK 75mm throttle body. As far as I can tell the MAF is still stock. I have a couple questions. One is the 75mm TB too much? The car is daily driver and I never race it or have any plans to. Is this killing my low end or would switching to a 70mm make a difference? The throttle also seems a little sticky at times, is this normal with an aftermarket TB?

What size/brand MAF should I go with? I plan on upgrading to PI heads/cams eventually if that makes a difference.

Thanks for any help/input.

 

[trinity_gt]

I just bought a 98 gt convertible a couple weeks ago. It already has a Trick Flow upper intake plenum, BBK CAI, and a BBK 75mm throttle body. As far as I can tell the MAF is still stock. I have a couple questions. One is the 75mm TB too much? The car is daily driver and I never race it or have any plans to. Is this killing my low end or would switching to a 70mm make a difference?

Couple of things:

1) The engine spends most if its time throttled to varying degrees, which you control with your foot. You're not losing any low-end torque with that throttle body.

2) It's doubful the car needs that much TB diameter because it's got NPI (non-performance improved) heads and probably doesn't flow enough to take advantage of that TB. Still, it's a decent TB to have on the car if you decide to upgrade other parts later.

The throttle also seems a little sticky at times, is this normal with an aftermarket TB?

No. Get under the hood and check the linkage manually. Operate it to its full extent (engine off) and look for binding, hanging-up etc. Also check the return springs.

What size/brand MAF should I go with? I plan on upgrading to PI heads/cams eventually if that makes a difference.

I'd stay stock. You'll get the best driveability out of the stock meter. After you go the PI heads and cams route you might think about upgrading to a 99-04 MAF but you won't need any more than that.

 

[Dark04GT]

Trinity pretty much has this one taken care of.

TB combined with plenum offers a couple hp and could be a worthwhile mod. With your car I would do the PI swap (at least intake manifold and cams) before I spent any time working on the TB or the plenum.

As far as the TB goes:
I've seen dynos done by C&L that claims that the 75mm is superior to the 70mm in basically stock NA stangs, they claimed something like 1-2 hp gains with the 75mm over the 70mm (both have aftermarket plenum and CAI if I remember). That being said, I have a little scepticism of those numbers and I think you cannot go wrong with either the 70mm or the 75mm TB.

 

[c.moser]

The car already has a the 75mm TB, I just wasn't sure if I should get something smaller or not.

If I get the P.I. intake, should I still use the Trick Flow upper plenum I already have and use just the lower P.I. intake, or would I be better off using the upper and lower P.I. intake?

 

[trinity_gt]

If I get the P.I. intake, should I still use the Trick Flow upper plenum I already have and use just the lower P.I. intake, or would I be better off using the upper and lower P.I. intake?

Use the T/F upper on the PI lower.