Aftermarket throttle bodys. Is bigger better? 56mm or 61mm

[RyanDS650X]

Im on a mission to sort out my strange idle issues and the throttle body and associated sensors are OEM and with the truck at 180k its time. My top end is all aftermarket and the last piece of the puzzle is the throttle body and i see BBK offers 56mm and 61mm products http://www.autoanything.com/air-intakes ... 90474.aspx
They are the same price for either unit so thats not a consideration.
So the age ol question.... Is BIGGER better?

[BDKW1]

Which intake do you have? The stock one will need heavy porting to match the 61MM. Even the Edelbrock one needed to be opened up a little.


If your going to replace it, go big.........

[BDKW1]

Edit, Also NOT recommended for speed density systems unless you have a fully tunable aftermarket computer.

[RyanDS650X]

Ive got the Edelbrock package, upper and lower intake manifold and cylinder heads. Im not afraind of a little porting. The truck goes on the dyno for a tune after these next few upgrades and general tune up. ive got a 96 with MAF so its not an issue for me. Thanks for the input.

[BDKW1]

There was a larger MAF that you could get also. Would be nice with the larger TB if your going to get it tuned.

[BDKW1]

Another edit.......

Pull the cover off the upper and give it the once over with the die grinder. Mine was kind of ugly in a few spots. A little work with a burr and some cartridge rolls made a huge improvement.

[BDKW1]

You could probably get pictures from Steve........

[ChaseTruck754]

We'll see. Since the move & I sold the supercab that build is on hold = that stuff is now neatly packed away and buried in the garage. Takes a bit of effort to dig out pretty much anything I've squirreled away for that build.

[RyanDS650X]

BBK doesnt make a truck or bronco specific unit but the one for the 94-95 mustangs look very similar to mine...
http://www.bbkperformance.com/products/mass-air-meters/

[CPT. SPRINGINGTON]

with larger throttle bodies you'll lose throttle response and normally see no HP. You'll notice they use the same throttle body of a 302 on a 460. There's calculators out there for you to do the math of airflow through your intake and heads to see what works best for you, but I wouldn't go larger unless you are force fed and pushing more than 10psi or so.

What's you idle issue?

[BDKW1]

Force fed does not need the bigger throttle bodies. The stockers flow plenty under pressure. NA benefit more from this as they remove a lot of restriction under WFO conditions. The off idle response issues is due to how much more they flow at partial openings. If you do not have a MAF system or recalibrate your speed density for this your fuel curve will be way off and give very poor response.

[CPT. SPRINGINGTON]

For force fed, whatever has less restriction from the valves to the turbo/procharger is good, starting with the cam first of course.

here's a good write up and some "figuratively speaking" charts to get the OP thinking.
http://www.stangnet.com/mustang-forums/ ... ter.692440

[RyanDS650X]

Ive got the Ford Motorsports E303 cam.

[damon1272]

Seeing as you have an aftermarket top end you should be alright with a 61mm. If you were running stock parts I would not go over the 56mm. I suppose the former owner upsized the mass air meter. Seeing as the former owner had a ton of aftermarket stuff on that truck before he sold it I imagine the mass air meter was done also.

[RyanDS650X]

Unfortunately not. The airbox, meter and TB are OEM. Which is why i want to upgrade before its dynoed.

[damon1272]

If the mass air meter is not upsized then I would not waste the money at this time. The airbox will flow the air but the factory meter is pretty small I think 55mm so not worth the dough to upsize the throttle body at this time.

[RyanDS650X]

here's a good write up and some "figuratively speaking" charts to get the OP thinking.
http://www.stangnet.com/mustang-forums/ ... ter.692440

Thanks that was a good read. So just taking ballpark figures from this (taken from the link above)
"Below is a chart with the CFM requirements, based on displacement (in cubic inches) and RPM. This chart will work for any piston engine with any number of cylinders. After you have determined the CFM for your specific engine combination, you can then choose the corresponding throttle body or carburetor size to best fit that combination.

DISPLACEMENT………….6000 RPM……….6500 RPM……….7000 RPM
280………..…………………486………………..527………………..567
290……..……………………503………………..545………………..587
300………..…………………521………………..564………………..608
310……..……………………538………………..583………………..628
320……..……………………556………………..602………………..648
330………..…………………573………………..621………………..668
340……………..……………590………………..639………………..689
350……..……………………608………….…….658………………..709
360………………..…………625………………..677………………..729
370………………..…………642………………..696………………..749
380………………..…………660………………..715………………..770
390………………..…………677………………..734………………..790
400………………..…………694………………..752………………..810
410………………..…………712………………..771………………..830
420………………..…………729………………..771………………..830
430………………..…………747………………..809………………..871

This chart should give you a general idea of the amount of air your combination will pump. Engines will pump less air because of the restrictions in the cylinder head or intake manifold design or valve lift, or all three. But, the chart still gives you a ball park starting point.

With an EFI system the throttle body only controls air flow. A computer monitors the gasoline supply and the mixing of gasoline and air takes place inside the intake port, and not inside the carburetor. Using an oversize throttle body is not nearly as detrimental to low and midrange performance as is using an oversize carburetor."

A port matched 56mm would be more than enough for my application.
So would the stock MAF not keep up or is it just a restriction issue?

[yikes]

That's a handy chart Ryan.

[damon1272]

The MAF will be a restriction issue rather than keeping up.