Injectors get bought by the cc number off a forum post, and that is how people end up with a set that is either out of puff at the top of third gear or so big the car will not idle. The number on the box is only half the story. The other half is the pressure it was measured at, the fuel you are running and whether your ECU has the data to drive it properly.
The short answer
- Size for the fuel you plan to run, not the fuel in the tank today. Ethanol needs a lot more volume than petrol for the same power.
- The ID1050-XDS at 1065cc covers most street and club level builds, in vehicle specific sets.
- Step up to the ID1300-XDS or the ID1750-XDS when the turbo is bigger, the fuel is ethanol, or both.
- Check the o ring size and the length before you order. That is the part people get wrong, and adapters exist for a reason.
How injectors are rated and what the numbers mean
Injector flow is quoted in cc per minute at a stated fuel pressure. Change the pressure and the number changes. On a boosted engine the regulator references the manifold, so rail pressure climbs with boost and the pressure drop across the injector stays roughly constant. That is the point of the setup, and it is why a static flow figure only means something with a pressure beside it.
The other number that matters is duty cycle, which is how much of each cycle the injector is open. Push a small injector to full duty and there is nothing left when the tuner needs a bit more fuel on a hot day. Leave headroom.
Then there is dead time. An injector takes a moment to open and close, and that lag changes with voltage and with pressure. Injector Dynamics publish characterisation data so the ECU can compensate, which is why their injectors idle properly at sizes that used to make cars stumble. Load the data. A tuner who has to guess at small pulse widths will make the car driveable, not good.
Picking the right injector for your build
Street and club builds
The ID1050-XDS is the workhorse. We stock it as vehicle specific sets, so you get matched injectors and the right length in one box: the WRX 02 to 14 and STi 07 to 17 set, the Evo X set, and the GR86, BRZ and FR-S set. Six cylinder builders get the six injector set, and there is a single injector when one gets damaged.
Barra owners are covered too, with sets for the BA and BF Falcon XR6T and the FG.
Bigger turbo, or E85 in the plan
The ID1300-XDS at 1340cc is the next step, and it is where a lot of built four cylinder cars land once the fuel changes. Ethanol is the deciding factor more often than power is.
Big power builds
The ID1750-XDS at 1728cc is the top of the range we stock. If you searched for an ID1700x, this is the current part. It suits an engine that is already built and tuned by someone who logs everything, not a stock bottom end with a big turbo bolted on.
Flowmatched Bosch through Haltech
Not every build needs the top shelf. Haltech supply flowmatched Bosch sets, including 980cc in fours, sixes and eights, plus 1462cc sets of four and six. They are a sound choice on a Haltech car where the injector data is already in the software.
| If you want | Go for | Why |
|---|---|---|
| A tidy street build on pump fuel | ID1050-XDS in your vehicle set | Matched set, right length, data available |
| Room for E85 later | ID1300-XDS | Volume for ethanol without going silly |
| A serious ethanol build | ID1750-XDS | Largest in the range, for engines built to suit |
| A Haltech car on a budget | Flowmatched Bosch 980cc or 1462cc | Known quantity, data already in the ECU |
Making them fit: 11mm, 14mm and adapters
The cc rating tells you nothing about whether the injector will physically fit. Two things decide that: the o ring diameter at the rail end, and the overall length between the rail and the manifold.
Injector Dynamics list the same injectors in both sizes, so browse the 11mm injectors or the 14mm injectors depending on the rail you are running. Length is handled with adapters, and Haltech has the useful ones: 11mm three quarter to full length, 14mm half to full length and 14mm three quarter to full length. Nissan owners get a Nissan base adapter and an RB26 specific 10.5mm adapter. The whole Haltech injector and adapter range sits in one place.
Measure before you order. A set that is 10mm too short is a set you cannot use.
What to buy with it
Filtration comes first, because a big injector is a precision part with a small orifice. The ID F1250 in line filter kit arrives with its bracket, and the F750 has replacement elements and bowl o rings so servicing it is not a whole new purchase. There is also an optional pressure and temperature sensor block if you want to log what the fuel is doing before it reaches the rail.
The rest of the fuel system has to keep up. Injectors that size need a pump that can feed them and a regulator that holds pressure while they are open, so size all three together rather than one at a time.
Where NZ Performance fits
We hold Injector Dynamics stock in Palmerston North alongside the Haltech sets and adapters, and it ships nationwide. The Injector Dynamics hub page lists the range in one view if you would rather browse than be told.
Read the fuel pump sizing guide next, because injectors and pumps run out together, and the fuel pressure regulator guide for the part that keeps the pressure honest. If the whole fuel system is still on paper, choosing turbo size and fuel system puts the pieces in order.
FAQ
What size injectors do I need?
Work backwards from the power you want, on the fuel you plan to run, at the pressure the engine will actually see. Then leave headroom so the injectors are not sitting near full duty at the top of a run. If E85 is anywhere in the plan, size for E85 now rather than buying twice.
How much bigger do injectors need to be for E85?
Meaningfully bigger. Ethanol needs a lot more volume than petrol for the same power, so a set that was comfortable on 98 gets tight on E85 at the same output. Most builders who plan to run flex fuel go up one size in the range.
Are ID1700 injectors still available?
That part is now listed as the ID1750-XDS at 1728cc. It is the largest injector in the Injector Dynamics range we stock, and it suits big power builds on ethanol rather than a mild street car.
What is the difference between 11mm and 14mm injectors?
It is the o ring diameter at the rail end, and it has to match the fuel rail you are using. Injector Dynamics list the same injector in both, and Haltech sell adapters that convert 10.5mm, 11mm and 14mm bodies to full length so a short injector fits a taller rail.
Will big injectors make the car idle badly?
Not if the ECU has the right data. Modern injectors need characterisation data for dead time and small pulse widths, and both Link and Haltech accept it. Loading that data is what separates a big injector that idles cleanly from one that hunts.
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