I recently got my injectors cleaned from RC. Im about to put the injectors back in but I saw those plastic things that hook up to the injectors. The diffusers slightly restrict the fuel flow from going into the manifolds. I wonder if its safe to remove them. Did anyone remove them and did you feel a significant difference?

 

keep them they help atomize the fuel better

 

They aren't "necessary" but they help with fuel efficiency.

 

do you think it would effect the throttle response?

 

And by doing so they promote atomization of the fuel....which is what you want.

 

leave them in

 

i take them out,, they are old and cost engines when they break
my engines are late close ported and run aftermarket ECUs with no diffuser but are still capable of a decent idle

also i more oftent than not upgrade my engines for 2 x 1000 secondarys or 4 x 1000 cc packages

these injectors ( disk type ) have there own inbuilt spray difuser

so the mazda stuff is nothing but risk,, and a restriction to higher airflows and fuel flow from bigger injectors
( ask Howard Coleman CPR, a part of one of those difusers cost him a rebuild recently )

if fitting the rochy type ( marren ) 1000 cc injectors then you replace the secondary diffuser with an extra rubber base grommet
if fitting these injectors to the primary you can use two more rubbers or a single rubber on top of the top section of the two part difuser installed up side down

i have done this many times and i am yet to see any issue

 

The injectors also won't seat properly if you take them out. Leave them alone.

 

good point there bumpstart but i dont think the oem 460cc denso injectors have built in diffusers. im pretty sure you can replace the diffusers with o-rings to fill in that gap but i think im just going to leave them in. i wouldnt want my engine to burn non-atomized fuel. time to remove the intake manifolds from my bucket of vinegar and baking soda and start scrubbing that carbon off!

thanks!

 

speaking only for turbo setups
i have put normal turbo injectors in the same situ,, regained the mounting position same with extra base rubbers
i also have coolant crossovers blocked ( ambient is 5- 42 C here coldest/hottest )

and in the turbo cars it does not cause any noticeable differences,, no added injector pulse width for idle,, no puddles,, no stains
-- manifold is more than hot enough despite no coolant crossover in these conditions

the only time i would think there is an issue without the cups or coolant crossovers would be in very cold ambient conditions or when there is emissions idle checks

 

The s4 primary diffusors are actually quite robust and don't protrude very far into the air stream, I don't recommend messing with them...the secondaries however are a bit thin. My method of removing them is I simply break their legs off leaving the upper plastic seat, this way no additional o-rings or spacers are required.

 

I'm considering replacing my diffusers. One broke while removing it to have the S5 turbo LIM powder coated. What I have read about people doing is once they loose the diffuser part on the end they cut the remainder and use the o-ring part so that the injector seats correctly.

 

So are the secondary diffusers necessary or not? I have the top part still intact but the bottom part with the legs broke so I wont have any seating issues.

 

Now that's for the primary injectors. I doubt it matters as much on the secondaries because they don't come on at low speeds. The biggest reason for the diffusers are HC emissions and to a lesser extent fuel economy.