fidelity101

iTrader: (11)

I have an S5 motor in an S4 car using the S4 electronics and all that boring jazz, so I still use my S4 injectors but I am using S5 rails. so I ordered s5 grommets for my injectors since they were going to be on an S5 block/manifold with s5 rails.

on mazdatrix's website they have the grommets listed as

84-92 All Upper Grommet 13-2520-8574
84-88 All Lower Grommet 13-2570-N326
89-92 All Lower Grommet 13-2570-N350

so I have the right upper grommet but I ordered the bolded grommet for the lower

I have a terrible vacuum leak coming from the primary injectors and the air bleeds are in there.

The 84-88 non turbos use a one piece bleed, while 86-88 turbo and all 89-92 use a two piece bleed (Top & Bottom)

so do I need to put S4 air bleeds in there or did I buy the wrong grommet?

help

fidelity101

iTrader: (11)

anyone?

arghx

iTrader: (3)

hold on. What exactly are you talking about? the grommet that seals the bottom of the injector to manifold/intake port? The metal diffuser that actually sits inside? Or the o-rings for the metal diffusers?

fidelity101

iTrader: (11)

that one

or should I be using the S4 air bleeds on the s5 block?

arghx

iTrader: (3)

The terminology gets confusing. You have a lower grommet on the injector to keep air from escaping. You have plastic/metal/whatever diffusor to affect the spray pattern. You have o-rings that seal for that. And then you have little ports on the manifold itself that provide fresh air to further enhance atomization.

Somebody else can correct me if I'm wrong, but from what I have seen the diffusor has nothing to do with the grommet on the injector itself. The grommet seals the injector to the manifold or the intake port (on the primary's) to prevent a vacuum leak. The metal/plastic/whatever diffusers affect the spray pattern of the injector. The o-rings on the diffusers i'm guessing are to keep fuel from splashing back upward and may have some role in preventing air from escaping, but I've never had one of those o-rings fail before.

From what I have seen you could take out the diffusers completely and you shouldn't have a vacuum leak provided that the lower grommet of the injector is intact and the rail is torqued properly. In fact, I had no secondary diffusors at all (metal/plastic thing) on my old s4 manifolds and I did not have a vacuum leak. You COULD have a vacuum leak if the nipple(s) on the manifold that are meant to supply fresh air are in fact open/leaking for whatever reason.

So use the upper and lower grommet for 84-88, because you have 84-88 style injectors. There is only one type of upper grommet, so that's a no-brainer.
I don't recall what the s5 lower injector grommet looks like but those injectors are all the same basic Denso style. I can't see how the grommet is much different than the s4. I have used an s5 n/a injector in an 88 s4 n/a car before.

I am using s4 injectors on an s5 manifold right now and have confirmed no vacuum leaks using a pressure tester. In this case I am using s4 style Greddy/Denso 720's, and I have been told this product started life as the stock injectors on 12A turbo cars. They are exactly like the 86-87 1/2 style in all respects except color and of course flow rate. I am using s5 diffusors with my s4 injectors. But from my own physical examination and from looking at the pictures, there are only minor differences between the two series. They are the same basic diameter and will both fit in there.