I received my s4 t2 keg from my rebuilder all complete yesterday. He did not include the fuel injector diffuser / air bleed. These are the little plastic caps/spacer in the primary injector holes. He said that they were old and brittle, and wouldn't use them in fear of them breaking and falling into the engine. Understandable.

They seem to be rediculously overpriced! It's only tiny pieces of plastic! Is there another place I can look for these guys or do I have to drop over a bill for these things? Any aftermarket ones?

http://www.mazdatrix.com/c-6.htm
http://atkinsrotary.com/store/home.php?cat=781

Thanks.

 

They helped to atomize fuel w/ the older style injectors that came with the car stock. If you are running newer ID style injectors with superior fuel atomization and better spray patterns there is probably little value in retaining them.

When I rebuilt my engine last month I kept them from the primaries because I am using Seimens 750's x4 and their spray pattern isn't the greatest. My LIM didn't have diffusers for the secondaries and I didn't worry about it, there should be sufficient turbulence in the intake runners to mix the fuel and air adequetly. No problems so far.

 

I'm running id725/2000.

 

Then I wouldn't worry about replacing them.

 

I would recommend replacing them. Yes, they are expensive (who knows why) but I have tuned the exact engine with and without diffusers. Without the diffusers took about 5% more fuel at light loads than with the diffusers. Plus without, it never would idle as smooth as with them installed.

 

yes. i get funny idles when they remove the diffusers.

 

Numbers > conjecture.
Learn something every day!

 

Related question as I don't know the answer.

Are the diffusers in an NA the same used in a TII block?

Are the diffusers in an S4 different than what used in an S5. I believe the answer to this one is yes, but I'll stand aside and let others more hand one confirm.

 

Click on the Mazdatrix link I posted note the pictures and part numbers. Your questions will be answered without me confusing you.

 

That was too obvious.

To answer my own question, there is some cross compatibility between NA and TII, and between S4 & S5. But you need to check that Mazdatrix pictures to as too many variations to pull togther in one narrative answer. For instance, the TII Primary Top's are the same between the S4 and S5, but the primary bottoms are different.