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Is a Bigger Mustang Throttle Body Always Better?

Written By: Lisa Schaefer

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When it comes to Mustang throttle bodies, size does in fact matter and bigger is not necessarily better. Choose the throttle body that will give you the most power and bang for your buck.

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This is a guide to understanding the difference in performance and function for variously sized Mustang throttle bodies. Despite what some might say, bigger is NOT always better.

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Installing A Bigger Throttle Body on Your Mustang – The Facts 

70mm 1999-2004 Throttle Body

When it comes to modding your Mustang, it’s well-known most people follow the notion that bigger is always better. Well, when it comes to choosing which throttle body to install to produce the best performance results, bigger is NOT always better. The goals you have in mind for your Mustang as well as the current mods your running will both play a large part in which direction to take.

  • More airflow caused by a bigger throttle body can increase power and improve throttle response
  • Mildly modified/stock Mustangs do not have enough air flow to fully benefit from the largest throttle body, and consequently, can reduce throttle response
  • With an upgraded throttle body, it is not necessary to invest in an intake spacer
  • It is not necessary to recalibrate your computer with a custom tuner with a new throttle body, but to fully utilize your mods, it is recommended to purchase a custom tuner
  • Trying to push too much air flow withou the fuel to compliment it could risk damaging your engine.

Mustangs With Bigger Throttle Bodies - Performance Benefits

SCT Handheld Mustang Tuner

The more airflow, the better your engine breathes and the more power your Mustang will produce. By opening up the bore size from factory to an aftermarket throttle body, not only will power increase but the throttle response will improve as well for an upgrade you will feel! However, if your Mustang is stock or mildly modified, your engine doesn’t flow enough air to fully benefit from the largest throttle body available and can consequently hurt your throttle response. Think of mild mods as a cold air intake, a cat-back, or a axle-back exhaust. You'll need further fuel modifications to compensate for the added air the largest throttle bodies can offer. Running too lean can damage your engine.

For example: take a 1996-2004 naturally aspirated GT with an intake and an aftermarket exhaust. The 70mm throttle body would be the best option for HP and throttle response gains. A 78mm would be too excessive and cause lean air/fuel mixtures. Even if you plan to add several additional bolt-on mods, the 70mm would be plenty big enough. It is larger than stock to increase air flow over the stock restrictive unit, yet not too large that it results in lost velocity and ultimately decrease mid-range rpm gains.

Moving away from the 4.6L engine, if you are driving a naturally aspirated 5.0L with some mods, moving up to a 90mm throttle body would be a solid choice for improved power and performance. A 90mm throttle body is a great step up from the stock TB, givng both naturally aspirated and forced induction motors a healthy dose of air, helping to give you a strong powerband.

If you have a heavily modified Mustang (forced induction or extensive head work, anything that makes signifigant changes in air flow), then a 75mm throttle body or larger would be your best bet. A BBK 78mm throttle body is one of the most popular options. It incorporates a high flow intake plenum and is a great combo to compensate for the increased air flow from the engine. Just don't forget to add fuel injectors and perhaps a boost-a-pump for all that extra, supercharged air. 

The Truth about Mustang Throttle Body Spacers

Plain and simple – if you upgrade to a larger throttle body, you should not use a spacer as well. Intake spacers are intended for use with the stock throttle body to increase fuel mileage and throttle response. The bore on the spacers are matched to the bore of the stock throttle body. If you were to couple a spacer with an aftermarket throttle body, you would essentially open up the air flow, but immediately restrict it again by using the spacer. So, the only time you want to use a spacer is in combination with your stock TB.

Stock Mustang Throttle Body Sizes

YearThrottle Body Sizes
1979-199358mm
1994-199560mm
1996-200465mm (The 1999 2V GT has a 66.8mm throttle body)
2005-2009Twin 55mm
2010-201680mm

Will my Mustang Need a Custom Tune?

Another great debate in the performance world! When you upgrade your throttle body, it is not always required to recalibrate your computer with a custom tune. That being said, we highly recommend getting a custom tuner to fully utilize not only your intake mods, but all of your upgraded parts. Our Bama Tune Specialists can incorporate the larger throttle body into your tune files to ensure you get optimum performance from your upgrade. The custom tune will let your Mustang’s computer (ECU) know there is increased air flow and will correct the air/fuel ratio.

More often than not, you will likely need to retune your Mustang in order to get it running properly, maximizing performance at the same time.

If you are looking for your next bolt-on mod and don’t know which direction to take, upgrading your throttle body is a very common and popular route to take. Just make sure you think about what your ultimate plans are for your Mustang when deciding which TB best suits your application!

Adding Power With a Throttle Body & TB Spacer

Gains from a throttle body can be dependant on modifications. Generally speaking, anytime a throttle body is added, there will be some added horsepower. The amounts can range from 5-25 hp depending on what other modifications are done to the engine. In stock form, the gains will be on the smaller side of that range while a heavily boosted mustang will see gains on the higher side of that range. A throttle body spacer is more of an aesthetic and sound mod.

While you get increased throttle response, there is little to no gain power wise from a spacer. In summary, if you are aiming for more throttle response on a budget, get a spacer. If you want more power with your increased throttle response, go ahead and check out throttle bodies.