Fuel rail configuration?

[Neffets]

So I'm going to fabricate a fuel rail for my ITB project, but where to put the FPR?
There were several configurations during the years.

I was thinking of going the easy route like the 996, but looking at the previous years I wonder why they did all the other configurations?
for instance on the 993 the return line exits between two injectors.

[Neffets]

Doh, forgot the picture

[HawgRyder]

According to rules of hydraulics...so long as the ID of the pipe is the same...the pressure should be the same throughout the system.
Now...when you figure in "flow" all that changes.

In high power engines (drag cars) ... we oversized all the tubes so that none of the cylinders got starved for fuel.
The 996 system seems best to me...fuel in one end...and the relief valve and pipe at the far end.
Personally...I would stick a cleanable filter in the system just before the fuel gets to the rails...this way the injectors stay unclogged...and it's easier to get to the filter if it's up close the the rail and at the rear (rear of car) for easy access.
Check out cleanable filters as used in motorcycles.
Bob

[al lkosmal]

+1

[Walt Fricke]

Well, I favor the ring configuration, like the 964. The notion is that if one line gets obstructed, there is an alternate route. Not bloody likely that lines this big will get obstructed, of course. But it looks good. Carbs for racing were often done this way.

[Raceboy]

964 method is what is preferred in high-powered turbo cars. That way the distribution is equal and you will not lose much flow on the last cylinders. 996 approach is done purely for cost considerations (if you have to produce like 100 000 kits like this, every centimeter of hose counts).

[psalt]

964 route is best, with a "Y" rather than a "T" before the rails. Avoid any 90 degree fittings and use bent tube fittings at the front of the rails.

[proffighter]

Version 996 on my 930 Turbo with no issue. Rails have more volume than stock 964 etc. and lines are AN-6, no pressure drop even on the last cylinder

[proffighter]

Maybe a pic

[911pcars]

On a basic hydraulics level, if the source pressure and volume is equal to/greater than that used by the system at all engine speeds/loads, the injectors should deliver the correct amount of fuel as designed. Is there an identified roadblock in the factory systems?

Yes, a boosted engine must contend with variable compression and combustion environments. I see more of an issue in those engines.

Sherwood

[jpilcher]

Hey Roland

Sorry to hijack thread.

Quick question. What vacuum source are you using to feed your blowoff valve?
Is it on intercololer side of throttle body?
I have a tee in line supplying map sensor, similar to you configuration on back side.
See any problems with this?

Did you get your cold start figured out?

Regards

John

[proffighter]

Originally Posted by jpilcher

Hey Roland

Sorry to hijack thread.

Quick question. What vacuum source are you using to feed your blowoff valve?
Is it on intercololer side of throttle body?
I have a tee in line supplying map sensor, similar to you configuration on back side.
See any problems with this?

Did you get your cold start figured out?

Regards

John

John

The port (stock for Distributor on my ROW '81 Turbo) is below the throttle plate, so correct vacuum at all loads. I use this for my BOV.

Concerning my EFI progress: As you can see in my rust combat thread, I cannot run the engine for a while, so no chance to work on the map. But it was not that bad so far...

[porterdog]

The rail I put on my turbo Miata conversion was fed from both ends. This was in ~'00, so my recollection may be flawed, but as I recall one of the primary concerns in rail design was local pressure fluctuations caused by the injectors going on and off. Designs fed from both ends were said to be better at damping the resonances which could result at certain points in the operating range.

[Jeff Alton]

we have always used the 964 style without issue. But that is not to say the other solutions won't work.

Cheers

[safe]

I use the 996 style on my engine. Didn't give it much thought at the time. Works fine as far as I know.