Why You Need Injector Seals – Part 1

Why You Need Injector Seals Part 1 


If you’re a car enthusiast that wants performance, reliability, and of course cost effective upgrades, then injector seals should be on your wish list…wait doesn’t everybody want that for their Mazda? I think so; let me tell you why…

As car enthusiasts we all ultimately seek more power. It starts with an air intake, and then we need more fuel, which leads to the high flow pump internals, but that only scratches the surface. Oh then, Mr. Cobb finds himself plugged into your OBD II port and you’re running 20+ psi grinning ear-to-ear.  It’s OK, we are all guilty; some more than others, but something has to give and so it does. What that is that gives, well it’s easy to miss, because your car is smart and compensates for it, but it’s happening. You’ve got bad injector seals! Don’t believe me?  I’ll prove it!

You have probably run across injector seals while shopping for various other parts, but didn’t pay attention to them. Essentially, they are fancy little cups that fit over the nozzle of the injector.  Now for the real question: have you ever seen an OEM injector seal? Doubtful. They are tiny steel washers designed to crush and seal…the stock ones are pitiful.

What happens when a seal doesn’t seal? All of your hard earned power escapes around it, making a mess of the injector and fuel rail. Look below you’ll see that the injector ports in the cylinder head are filthy.


Starting on the left, the injector port is clean and shiny like freshly machined aluminum.  Now look at the port farthest to right; black as night and a bit gritty.  That seal gave up before the rest and I have a sneaking suspicion that it has to do with the EGR going through mainly that cylinder, but we will save that for another day. Here is a close up of the dirty injector before and after a scotchbrite rub down.

Seals-Rail-Intake-Manifold-CorkSport-Injectors-Tokay-DISISeals-Rail-Intake-Manifold-CorkSport-Injectors-Tokay-DISI-NewNow that is a big difference huh! Do you believe me yet? Maybe? Let’s compare the seals…

Look at that picture below and let that sink in…

New Seals:Seals-Rail-Intake-Manifold-CorkSport-Berrylium-Copper-Tokay-Injector


OEM Seals:Seals-Rail-Intake-Manifold-CorkSport-Berrylium-Copper-Original-Injector-OEM-used

Are you flabbergasted like I am? Huge difference! So, why do the differences matter?  First off, it’s no longer just a washer with one sealing surface.  It’s a cup, so it seals in the OEM location AND along the side of the cup.  That’s not all! The secret is in the design (which is all thanks to @Tokay444; from MazdaSpeedForums.org).  Here is how it works. The lip at the bottom of the cup is flared just a bit so that it crushes down tight against the cylinder head, and as it crushes down it also crushes outward, pushing against the wall of the port much like an O-ring.

These four little beryllium copper cups are cheap and reliable, but how do they improve performance?  Let’s go back to our power hungry example running 20+ psi; with blow-by around the injector seal. That leak has now disappeared, which means if it’s not escaping there then it must be doing “something”.  That “something” is more power to your wheels and a happy MZR.  Our previous dyno testing with the OEM seals and 21psi were never consistent, declining with each consecutive run. Our new seals restore that decline, each dyno pull now falls on the previous line perfectly and that was in 90+ degree weather.

Have I convinced you yet? Stay tuned for part 2; we are going to put some hard miles on the MS3 and then inspect the seals.


6 Replies to “Why You Need Injector Seals – Part 1”

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