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Choosing a drive by wire adapter comes down to two measurements: the bore of your Bosch electronic throttle body, and the bolt pattern on the manifold or plenum it has to mount to. Bosch uses a square four bolt pattern in M6 on all three of the sizes swap builders commonly run, and the spacing changes with the bore: 65 x 65 mm on the 68mm, 70 x 70 mm on the 74mm, and 75 x 75 mm on the 82mm. Get those two numbers and the adapter choice is straightforward.

Autosports Engineering machines billet adapters, weld on flanges, hose adapters and bore reducers for all three sizes, in house in Lakeland, Florida. This guide walks through identifying what you have, picking a bore, and finding the part that bridges the gap.

In this article

• How do I identify my Bosch throttle body?
• Which bore size should I choose?
• What are the three ways to mount a Bosch DBW throttle body?
• Which ASE adapter matches my manifold?
• What else does a drive by wire conversion need?
• What if my manifold is not on the list?
• FAQ

How do I identify my Bosch throttle body?

Bosch Motorsport electronic throttle bodies are stamped with a ten digit part number on the housing. If the number is worn off, measure the bolt spacing center to center across the flange. Each bore has its own pattern, so the spacing alone identifies the unit.

All three share the same six pin electrical interface with dual potentiometer redundancy, and all three use the same mating connector, Bosch D 261 205 358-01. That means the wiring side of the job does not change if you later step up or down a bore size. Only the mechanical interface does, which is exactly what an adapter solves.

Which bore size should I choose?

Bigger is not automatically better. Throttle bore sets the ceiling on airflow, but it also sets how much air moves per degree of blade rotation. Oversize the throttle on a street car and the first ten degrees of pedal travel become twitchy, which is a tuning problem you then spend time papering over in the throttle map.

A practical way to decide:

• 68mm suits four cylinder and smaller six cylinder builds, and anything where part throttle manners matter as much as peak power. It is the common pick behind a Skunk2 or similar aftermarket four cylinder manifold.
• 74mm is the default on most 1JZ, 2JZ and RB builds. It flows well past what a stock displacement six needs and still has usable resolution off idle.
• 82mm is for large displacement, high boost, or anything where the intake tract is already sized to match. On a smaller engine it mostly buys tuning headaches.

One more constraint worth checking before you order: the throttle bore should be in the same ballpark as the plenum inlet and the charge pipe feeding it. A 82mm throttle stepping straight into a 3 inch pipe is a restriction moved rather than removed.

If your manifold is already machined for the 82mm pattern but you want a smaller blade, you do not need a new manifold. ASE makes bore reducers that bolt to the 82mm pattern and accept a 74mm or 68mm Bosch throttle body.

What are the three ways to mount a Bosch DBW throttle body?

Every DBW conversion uses one of three mechanical interfaces. Which one you need depends on whether you are bolting to an existing flange, fabricating from scratch, or joining to a hose.

1. Manifold adapters. A billet plate with the Bosch pattern on one face and a known manifold pattern on the other. This is the bolt on route if you run a common aftermarket manifold.

2. Weld on flanges. A machined flange you weld to your own plenum or tube. ASE offers these for 68mm, 74mm and 82mm, in 4 inch round, 5 inch round and 5 inch RMR D plenum profiles, plus a 74mm version cut for 4 inch extrusion.

3. Hose and clamp adapters. A billet transition from the Bosch flange to a silicone hose or a clamp style joint. Available in 2.5, 2.75 and 3 inch hose sizes, plus Vangen style and Plazmaman clamp profiles in 2.5, 3 and 3.5 inch.

Which ASE adapter matches my manifold?

Bolt patterns overlap between brands more often than people expect, so an adapter cut for one manifold will sometimes bolt to another. Where a part is listed for your exact manifold, use that one: the outer contour is machined to match the manifold face, so it looks right as well as sealing right.

Finish is a build choice, not a fitment one. Adapters are available raw machined or anodized in black, red and purple. Anodizing is done in house, which is how the tolerance on the sealing faces stays where it was machined rather than drifting under an outside vendor's process.

What else does a drive by wire conversion need?

The adapter is the mechanical half of the job. The electronic half needs three things, and they are worth confirming before you buy hardware.

• An ECU with electronic throttle control. Not every standalone supports it, and on some platforms it is a licensed or optional feature rather than something enabled out of the box. Check the specific model, not just the brand.
• An electronic accelerator pedal, or a mechanical pedal fitted with integrated position sensors. Bosch throttle bodies will not operate from a cable.
• Wiring for both ends. Six pins at the throttle body, plus the pedal, plus the safety logic your ECU expects for redundant sensor checking.

ASE machines the mechanical interface. The throttle body, pedal and harness are sourced separately. We do stock Haltech engine management, and several models in that range support electronic throttle control, so it is worth confirming the throttle feature list against the ECU you are planning around.

What if my manifold is not on the list?

Custom adapters are part of what the shop does. ASE runs 3D scanning, CAD and CNC machining in house, so an unlisted flange is a scanning and programming job rather than a dead end. Adapters get developed from measured geometry off a real part rather than from published dimensions, which is why the sealing faces land where they should.

If you have a manifold that is not covered, get in touch with the manifold make, the throttle body size you want to run, and photos of the flange face. Lead time depends on what is already in the queue, so ask before you plan a build around it.

Frequently asked questions

What bolt pattern does a Bosch 82mm drive by wire throttle body use?

75 x 75 mm square, four M6 fasteners. The 74mm uses 70 x 70 mm and the 68mm uses 65 x 65 mm, all M6. Measuring the spacing center to center is the quickest way to identify a throttle body with a worn part number.

Can I run a 74mm throttle body on a manifold machined for the 82mm pattern?

Yes. A bore reducer bolts to the 82mm pattern and accepts a 74mm or 68mm Bosch throttle body, so you can change blade size without touching the manifold.

Do I need a different adapter for a different anodized color?

No. Finish is a variant on the same part. Raw machined, black, red and purple are all the same machined geometry.

Will a Bosch DBW throttle body work with my existing throttle cable?

No. Electronic throttle bodies have no cable provision and no return spring arrangement intended for one. The conversion requires an electronic pedal or a pedal with integrated position sensors, and an ECU that supports electronic throttle control.

Does an ASE adapter seal with a gasket or an O-ring?

It depends on the part. Adapter sealing method is listed on each product page, so check the listing for the specific adapter before ordering gasket material you may not need.

My manifold brand is not listed. Can you make one?

Yes. ASE scans the flange and machines a one off adapter in house. Send the manifold make, the Bosch throttle body size you plan to run, and clear photos of the flange face to get a lead time.

Unless otherwise stated, aftermarket performance parts are sold for off road and competition use. It is the purchaser's responsibility to comply with applicable local and state law.