Frequently Asked Questions

General Questions

Q. When can I order your throttle bodies?  How much are they?

A:  We are targeting availability of our ITB systems in late Spring 2007.  You can reserve one of the first systems by placing a deposit at www.extrudabody.biz (our online store).  Our introductory prices are over 15% less than our retail price and can be found at the online store as well.   Fair warning: we haven't decided how long we'll hold our prices at these levels.

Q. Why does Extrudabody make "modular" throttle bodies and universal fuel rails?

A: Several reasons:

• Adaptability. 
  • Existing Individual Throttle Body (ITB) products have built-in base plates so our competitors must build a complete throttle body specific to one application.  Our ITB-3850 Throttle Body can be bolted to any of our 3 types of Base Plates, or you can make your own custom base plate for a professional fit and finish at a price much lower than you might expect.  
  • Similarly, existing fuel rail offers are either completed rails specific to an application, or raw fuel rail extrusion.  Our fuel rail is more easily adaptable than raw extrusion but costs are similar to mass market fuel rails.
  • Finally, we will soon offer a variety of additional options such as Spigot Adapters to enable our ITBs to be more easily used in Motorcycles, Snow Mobiles, and Personal Water Craft.  Also, we will offer Tapered Extensions to create more options to optimize air intake.
• Tuning.   
  • Our design offers an amazing range of runner length tuning (aka "Acoustic" or "Induction Runner" Tuning) - up to 160mm of added length using our Extensions.  You can add some extension, dyno tune, then add or subtract extensions until to achieve your desired response.
  • Our Extensions can be placed on either side of our ITB, therefore, the fuel injector can be placed farther or closer to the Valves as you like.  (Injector to Valve Tuning)
• Cost: Since our core ITB is the same for all applications and is made from extruded (not cast) aluminum, our cost and therefore our price are unmatched.  Since our design is Patent Pending, our performance to price ratio won't be matched anytime soon.
• Quality:  We use the best materials and production processes to achieve consistently strong, high quality product.  From 6061 T6 Base plates to 6063 T6 Extrusions to all Stainless Hardware, Extrudabody makes products that will withstand the harsh conditions of high performance engines.
• Beauty: The ease at which the Extrudabody Extrusion’s can be “Show polished” is unmatched in the Market Place.  Furthermore, since almost everything we sell is either anodized, polished, or stainless steel, it's very easy to clean up after the race or before the show (unlike cast aluminum throttle bodies).  Our system is more than show, but never hurts to look good going fast!

Q. Why Fuel Injection over Carburetors?

A:  Although EFI may require a bit more time and money to install compared to carburetion, the carburetion advantage ends there.  EFI offers:

• Better Power.   Although it's completely possible to get horsepower from carbs from professionals, it's easier for most to optimize a fuel injection system.  The computerized aspect of EFI simply makes retuning and refining the power curve faster and better.  Furthermore, ITB systems have been proven to extract the most power compared to standard EFI systems.
• Higher Economy.  By using a Air Fuel / O2 Sensor, fuel injection can burn fuel at the optimum ratio, regardless of altitude, weather, or engine load. 
• Lower Emissions.  Fuel is metered and used only as required and burned so that harmful emissions are minimized.
• Better Drivability.  Starting is faster and easier, cold operation is much easier to manage, hesitations can be programmed out with keystrokes instead of jetting and fiddling with carb settings, etc.

Q. What does a Typical EFI system look like?

A:  See our Example Installations page

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Individual Throttle Bodies (ITBs)

Q. What is special about Extrudabody over the competition?

A.  Quite a lot!  Please take a look at our Products page for the details.

Q. What Size ITB Bore Size do I use?

A: As a general rule, when looking at the engine horsepower per cylinder, use 40mm iTBs for ~50hp and less per cylinder (i.e., under 200hp 4 cylinder).  ~45 to ~65 hp, use 45mm (i.e., up to 500hp V8) .  ~60 to 80+ hp, use 50mm ITBs.  If these recommendations surprise you, it may be because a common practice is to use a larger throttle body than truly needed for optimal power output.  An overly large bore will generally sacrifice low end torque because air velocity is low at low RPMs compared to an appropriately sized throttle bore.  That said, we've run our 45mm ITBs on engines making more like 30hp per cylinder with good results.

Q. What is the Minimum Bore Spacing of Extrudabody’s ITB-3850’s?

A: 80mm! At 80mm there is 11mm between ITB’s. There is no maximum, but you'll need extra 8mm shaft material and an extra coupling to go above 130 mm of spacing.  At long spacing distances, you may consider using a highly flexible coupling instead of our aluminum coupling. 

Q. What is the Minimum and Maximum bore ID of ITB-3850’s?

A: The ITB-3850 gets it name from the Minimum and Maximum ITB Bore Diameter which is 38mm and 50mm.  Our plans call for building 45mm ITBs first, then adding 40 and 50mm according to market demand.  However, we can custom build at a premium anything in between!

Q. Can the Throttle Cam and TPS mount on either side of the ITBs?

A: Generally no, the Cam goes on left side of the ITB (as you look down at the ITB with the injector on top spraying away from you) and the TPS goes on the right.   If you use only an external throttle return spring, you could swap sides however, it just wouldn't look quite as clean.  Easier just to get a longer throttle cable and shorter return spring

Q. Can I use my Stock Throttle Cable?

A: Yes the Throttle Cam has a ¼” hole that excepts brass Cable Barrels you can find at every Help section of basically any parts store, another great place is your local lawn equipment repair shop! We will also offer an assortment of throttle cables and related hardware.

Q. Can I use my stock TPS?

A: We recommend using our TPS - it is very reasonable priced (including in all our ITB packages) and designed to easily mount to our ITB.  It uses a common Delphi/GM Weather Pack electrical plug and comes in two styles to help ensure clearance of the subharness.  However, you may want to use your existing TPS to avoid recalibrating your ECU.  We have not tried to adapt stock TPS sensors to our ITB’s, but anything is possible if you need it to work that way!

Q. What Voltage is the Extrudabody TPS sensor?

A: We use a 5V TPS with a Weatherpack-style connector with 3 electrical connections: 1) 5V Power 2) ECU signal 3) Ground.

Q. What Vacuum ports should I use?

A: Each ITB has 2 ports, 1 is for Vacuum and the other is for Idle Air Jet. The 10/32" threaded port located on the Top is the Idle Air Jet and the 10/32 Port on the Bottom is for Vacuum sensing.  Nickle plated 1/8" barb connectors are standard features of our ITBs and we also offer Plugs to seal them off.

Q. What Kind of Fuel Pressure Regulator do I use?

A: Currently, our fuel rails are best suited to using stand-along regulators with AN fuel fitting.  You can also easily use hose-barb style regulators common to OEM applications.  In the future, we plan to offer a rail-mounted, adjustable Fuel Pressure Regulator.  Probably the easiest source for AN fittings and FPRs is Jegs or Summit Racing.  A bit lower cost route is to find an OEM FPR that uses the fuel pressure that you need.  The Megasquirt folks list a few options.

Q. What kind of Air Filters can I use?

A: Our Air Horns are built to accept a custom made foam filter available at our store and included in our ITB packages.  We chose the foam design because it is easier to mold to engine compartment constraints.  Another product in our pipeline is an air plenum that will utilize a single air filter easily adapter to a cold air intake.

Q. Is Cold Air Induction a good idea?

A: Yes without question it is.  If the Air horns can be section off in the engine compartment and this general area fed cold air it will increase Horse Power! Sometimes this is not always easy to do so some cold air Ducting that funnels air to the filters general area is better than nothing at all.  That said, the power benefits of a properly tuned ITB system far outweigh gains from a stand-alone cold-air intake. 

Q. What is the Air Horn's Outer Diameter (OD)?

A: Extrudabody Air Horns have a 3” OD and ½” inner Radius.

Q. What kind of Injectors do I use?

A: Standard Bosch Port-style injectors may be used with 14mm O-rings. PICO style injectors may also be used for tight clearance areas where the fuel rail may be an issue. The Fuel Rail Standoffs will have to be modified or you can measure and purchase from Extrudabody the correct length.

Q. Do the ITB’s have Bushings or Bearings?

A: We use Viton sealed stainless steel bearings that are prelubed.  Bearings are a standard size and easily replaceable.

Q. Can I use Extrudabody ITB’s for high vibration environments like off-road racing?

A: Yes you can, however you might consider additional bracing of the ITB system as a whole, this is common even in our competitors CAST Base and Body systems!   The fact that our ITBs have flat edges makes it easy to use some stock Aluminum to create an extra brace across the ITBs.  Using Epoxy in addition to gaskets will also help with vibration resistance.

Q. Do I have to mount my injectors on the “wide” side of the IDF, DCOE, IDA or other carb-style manifold Base Plates?

 A: No! One of the beautiful design features of the Extrudabody ITB system it allows the ITB to be mounted at 90 – 180 – 270 – 0 Degrees with regards to our competition. 

Fuel Rails

Q. Do you offer a Fuel Rail pre-made for my Honda / Toyota /VW / Chevy, etc.?

A.  No we don't.  Our rails are designed to be easily customized, but you'll either have to do that yourself, or use our Cut-to-Length and/or Injector Hole Services for an extra fee.  See our Technical articles on fuel rail customization for more info.

Q. I'm not the handiest person with a drill, can I drill the injector holes myself?

A.  It is possible to drill the holes with a home-quality drill press but we do not recommend using a hand-held drill.  The most critical aspect is marking the rail to your specifications so you get the holes within 0.5mm of the target. If you used a small pilot bit in the exact center, then followed with larger bits, you should be able to achieve this accuracy. However, with a hand drill, ensuring that the holes are straight up & down might be a challenge. Luckily, fuel injector o-rings are fairly large and forgiving, so the injector can angle a slight amount between the rail and the manifold or throttle body without risking a leak. But in summary, most customers who aren't already comfortable with a small drill press might be better off having us drill the holes on a professional quality machine.

A: You can remote mount the Regulator, or you can attach it to the T-Slot system using an extra Rail Strut, or below the ITB’s utilizing the bottom Cable Strut Holes and extra Rail Strut.