Ducman82

there is holding tabs that mount the rail to the engine. that keeps constant pressure on the injectors, so they wont move

Carl Fausett

Exactly.

Nothing holds the injectors into the rails. The rails are held down to the manifold and the injectors are captured. They have an end in each of the manifold and the fuel rail. The injectors must be allowed to float, they are never held tight. Thats why the o-rings are so thick.

Fabio421

What about on the stock 85 - 86 rails? Please define "float".

Imo000

Carl,

I don’t know what to make of this but it concerns me to say the least. The original rails, on the early 32Vs, are designed to hold the injector with a clip and the entire assembly is held down to the intake manifold by the fuel rail mounting tabs. Yours has this feature completely eliminated. Correct me if I’m wrong but, the injectors in these rails are only held down by the force of the rail mounting tabs, right? Isn’t this a little risky?

Here’s my concern, if the rail tabs bolts get loose or the rail moves, there will be nothing holding the injectors to the rails and fuel will spray out of the rail. Is this correct? In the originals setup, the clips will ensure a physical barrier for the injectors to stay in place, even if the rail gets loose or moves.

Carl Fausett

Our design mirrors most all other aftermarket designs. Injectors are commonly sandwiched between the unmoving intake manifold and the unmoving fuel rail. This design has years and years in the field with no problems.

The concern you have about an item coming loose and spraying fuel can be applied to any part of the fuel system anywhere.

We use nylock nuts on our fasteners so they are vibration resistant. The hold down clamps are much stronger than the pressure they are holding against. Honestly, its not a problem.

Carl Fausett

Our website http://www.928motorsports.com/parts/...l_rail_kit.php
specifically excludes the 85-86 32v engine from the application list. This is because they are not yet tested for fitment on the pipe organ manifold and until they are, I cant recommend them.

Float: the injectors are not hard-clipped into the engine for several reasons:
1) heat transfer - if the injector was allowed to get hot by conduction with the engine they would perform poorly.
2) viration - engine vibration can cause an injector to weep as the needle can bounce off the seat
3) temperature delta - the engine expands as it warms up, and the heads move. Then the magnseium manifold expands and it moves too, but at a different rate. The injectors on the other hand are constantly cooled by cold fuel running thru them, and they travel in yet another direction. They float in the large o-ring so they can keep their center as best they can thruout the temperature range.

Larry928GTS

More than one 928 has had an engine fire or fuel leak when some of those clips were left off.

Imo000

Perhaps yes but now you are adding one more possible failure point. I’m guessing the reason others have the same design too is cost. It would cost substantially more to have rails that incorporate the OEM clip design as opposed to the drilled extruded bulk bars that these are all made from. So now there is a compromise to leave this feature out to save on cost. Looking at the pics, the 16V rails are not tied to the manifold either but to the cam towers.

All OEM FI rails that I’ve seen and worked on for the last 20 years have clips on the injectors. Maybe this is a secondary back up safety feature but either way, its sound engineering. It’s the same as having cotter pins and nylon locking nuts on tie rods/ball joints. They are there as a back up and they may never bee needed, except for that one occasion, for that one unfortunate driver. It may very well save his life.

To me this is the same thing as not to ever run a mechanical fuel pressure gauge into the cockpit.

Carl Fausett

Yes. Absolutely correct.

BUT - that is because the OEM system was deigned to require the clips. The old design would allow the injectors to be pushed out by the fuel pressure without the clips.

This is a different design. Designed not to need nor use clips. And thereby removing one more failure point.

With the weakness of the OEM system so reliant on those little clips.... it could be argued that this system is MORE secure and less likely to leak than OEM.

svp928

You guys missed Carls point about how the injectors fit OEM vs the billet rails- The OEM design allows SO MUCH movement, that the oring can come out of the bore on either end- the clip prevents that. The billet design, which is common to most all other race-type rails, does NOT allow that much movement. The injector can't move far enough to break the seal, so the only way its going to leak is if the whole rail comes loose- just like the stock one will, also.

So, the stock one can leak 2 ways- if the clips fail, or if the rail come loose. Carl's can only leak one way- if the rail comes off. So, its actually an improvement......

Before you accuse me of being on Carl's payroll- I'm not. I have never met or spoken with him. In this case, he is not re-inventing any wheels, he is using a design that has been working well for years, and is not prone to failure unless the operator screws it up....

Steve

svp928

I see Carl beat me to it---but he's right.

Imo000

The stock rails will not leak if they comes loose. If they do, the clips will hold the injectors in place.

svp928

Imre, if the hold-down bolts come loose, the rail and all the injectors will come out of the head, but I see what you mean Stock, this will just result in fuel coming out of the injector tip squirting around the engine. On the billets, it could pop an injector off, making a bigger leak. Still requires the whole rail to come loose, but possibility of a leak if stock clip comes off, which is more likely than the whole rail coming off.....

LEADASS

I unfortunately have an 86 32v when can I get mine!

auzivision

These look sharp. One more thing to add to the to do list.