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Home  /  EFI Parts  /  Individual Throttle Bodies  /  DCOE Type

PRO-RACE throttle body DCOE sizes 45mm to 52mm

Pro-Race DCOE Throttle Body. These are our flag ship model with all the features of the Pro Street version plus tapered bores and machined flat sections across the butterfly shaft. These additions aid the scavenging effect netting torque and power gains over parallel bores. These are available in sizes: 45/43/40, 48/45/43, 50/48/45, 52/50/47 & 55/52-Straight

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Including GST for Australian Customers

AUD $590.00 (ex GST)
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Every single throttle bore and throttle plate are measured and matched as a pair to ensure the most perfect throttle fit and consistency across every EFI Hardware throttle body.



DCOE Throttle Body Technical Drawing





Tapered Bore Throttles have a clear advantage over Parallel Bore Throttles at increasing power and torque. By accelerating the air through a venturi (in this case a tapered bore) the air speed through the throttle body is increased.  This enhances the engine cycle's scavenging effect to provide more air and fuel in the combustion chamber and therefore more power and torque.


The Tapered Bore has 3 sections:

Inlet from ram tube - 45, 48 or 50mm

This then tapers down to a short parallel section for the throttle plate - 43, 45 or 48mm

There is a second taper down to the outlet flange of the throttle body - 40, 43 or 45mm




HP/kW Ratings vary from engine to engine.  The power ratings given here are only a guide, and are not absolute power ratings.  Engine power is determined by intake, exhaust, cylinder head design, camshaft design, compression ratio, fuel type and quality and many other factors.


45/43/40mm - 50HP/38KW* per throttle - with the tapered bore giving a potential for 5% above this figure.

48/45/43mm - 54HP/40KW* per throttle - with the tapered bore giving a potential for 5% above this figure.

50/48/45mm - 64HP/48KW* per throttle - with the tapered bore giving a potential for 5% above this figure.

*This number is a guide only and should be used in conjunction with real-world experience.




In the past, 12° throttle plates were the industry standard.  The problem with 12° throttle plates, is that as the plates are moved off the closed position, the change in airflow is huge.  It makes it very difficult to drive smoothly at lower throttle openings.


At EFI Hardware, we only use 6° throttle plates.  This improves off idle and cruise driveability making your vehicle far more enjoyable to drive.



Manufactured from 601 Cast aluminum and heat treated before being CNC machined.

The butterflies are measured for each bore & precision machined to a 0.0005"" tolerance.

Butterflies are secured to centreless ground brass shafts with split screws to ensure reliability and serviceability.

All are fitted with bearings rather than bushes to eliminate axial shaft movement.

Low stiction bearings for sharp throttle response.


We now recommend

and use SKF bearings.