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Could someone take me to school on early vs late fuel rails?
Good morning, hope everyone had a good weekend.
I've read that the early cars use a different fuel rail than later cars and that the later ones have less bends in the to constrict fuel flow. For a stock street motor I don't image that makes much, if any, difference correct? Are there any advantages in the later rails on how they connect to the rest of the fuel system or to the injectors?
early vs late rails mount totally different. two different style of injectors , so comparing flow is Eh at this point. unless you are running a hot rod set up, no real reason to think of doing anything different from what you have on the motor now.
Why? I switched to LH/EZF from an 85 EuroS and wanted to use "clip" style injectors instead of the hose barb
How? Local friend of mine is an expert at silver soldering. He cut off the stock fittings and re-connected them for better orientation to the stock dampener & FPR locations. There is no right / wrong way to do this, just how my project ended up.
How Part 2: He also silver soldered on custom brackets which bolt down to the intake runners at the same location as the stock hold downs.
One thing I like about the later rails is the square design. Easier to grab with a wrench when removing the front ball cup to attach a gauge. I cracked a stock 16V rail at the dyno one time swapping gauges.
The stock "square" rails are very nice quality. Twin Turbo Todd uses them on his 1,000+hp 928.
At some point I'll be making a similar change to my 80. Why? Because I plan to ditch L-Jet for something else I can tune with a laptop and I'll again be swapping to clip style injectors.
Some mock-up photos. In the first one you can see how far off the stock lines are to the 85/86 rails.
EDIT - found more pics....yes they are a bit dirty. Cleaning up the rails for preparation to do the soldering took off a lot of the coating. I need to pull them & have them plated:
There's more versions of fuel rails than there are different models of 928's.
None of the rails are inadequate for stock or even high performance engines....until about 500hp.
Beware aftermarket "low volume" fuel rails marketed as "high volume". Some people will market anything to make a buck. Been going on, since the beginning of time.
You can put a megasquirt inside of the L jet box and run semi sequential injection by changing the injector grouping of the 4 connections in the stock harness.
Essentially making it a plug and play system if you ever need to put back in a L jet ECU.
It's been done over in the Alfa Romeo forums, don't see why it couldn't be applied to the 928.
For what it's worth, Todd's turbo is using stock rails with different hose connections on each end, making over 1,000hp:
The stock ends are the limiting factor on the original fuel rails. The hole isn't as large as it could be and putting larger ends on it fixes the flow limitation.
The stock ends are the limiting factor on the original fuel rails. The hole isn't as large as it could be and putting larger ends on it fixes the flow limitation.
Simply reinforcing Greg's point the stock rails flow more than enough for 99.999% of modified 928's. Many have stated the stock rails are too small (even with modified ends) to flow enough for high HP. Todd's car proves this simply isn't true.
Heat absorption should also be considered. The stock rails being made out of steel while most aftermarket units are aluminum, makes the stock ones even more superior than most aftermarket offerings.
So while yes the rail side fitting is a bit larger, the hose side fitting is actually smaller.
The reason why Todd changed over the rails was to make everything the same -6 fitting, not because he felt the flow needed to be increased over the stock fittings. Also, because he's running e85, he must flow more "fuel" to achieve the same HP as another engine making the same power with non-ethanol fuel.
07-03-2017, 11:13 AM
Could someone take me to school on early vs late fuel rails?
