3900 fuel injector upgrade.

[Mars]

As some of you know the 3900 uses a different fuel injector vs. the 3X00 motors.

They are much shorter.

I discovered that there are some aftermarket ones that fit with modification.

http://www.poweraddersolutions.com/fcode60lbhii2.html

Those injectors will fit, but the LIM needs to be modified.

As they stand those Deka injectors are 1/4" shorter than the 3900 injectors, not a huge deal, the 3 "standoffs" where the fuel rail mounts can be shortened 1/4" to make up for the difference in height. So after cutting the rail mounts down (I used a hacksaw blade held in my hand) lol, these fit perfect in a 3900.

I was a little afraid that I had wasted 300$ on injectors after I compared them to my stockers... But after looking at the LIM and rail setup this simple mod and they slide right in using the 3900 returnless rail.

Obviously you want to chase the threads with a tap and get slighty shorter bolts because the stock ones now bottom out in the bores.

[caffeine]

I was thinking of getting something like these for my build: http://item.mobileweb.ebay.com/viewi...d=330713666015
(Bosch EV14 injectors). It seems like they also fit Audi S4s so I'm keeping an eye out for a second hand set. They are also 48mm o-ring to o-ring and I thought they would be a direct fit for the return less rail but shortening the fuel rail mounts isn't too bad. I was looking at these mostly because I wouldn't have to source a set of injector connectors too.

[Mars]

I have the motron 60's with a 3400 fuel rail in my 3500, works very well.

[caffeine]

Eh I just figure if I'm needing injectors I might as well use the rail I already have. An afpr would be nice anyway.

[Kaiju Senso]

I was thinking of getting something like these for my build: http://item.mobileweb.ebay.com/viewi...d=330713666015
(Bosch EV14 injectors). It seems like they also fit Audi S4s so I'm keeping an eye out for a second hand set.

Not particularly relevant to the discussion at hand but yes, the Bosch EV14 injectors are a direct fit (with connector adapter) for the Audi S4 2.7T. I am running them now with 24 psi of boost.

[Mars]

Ahh see the EV14 ones are the correct length for a stock 3900, but these Siemens ones I got are even shorter than those ones...

The EV 14 ones I doubt would require mods to work. damn should of bought them instead.

[ericjon262]

These are the injectors I am using, on a 3500 with a 3400 rail, they fit perfect.

http://www.lingenfelter.com/mm5/merchant.mvc?Screen=PROD&Product_Code=L730030000&Category_Code=C77&Store_Code=LPE

[Mars]

Yeah. Thats just stock size for any 3X00.

For a stock 3900 you need 47mm Oring to Oring (54mm end to end)

[caffeine]

Just received my EV14 Bosch injectors today. Looks like they are actually slightly longer than the stock 3500 injectors (I'm assuming they're the same for the 3900 too), but I should just be able to space out the rail a bit if its an issue. Pic to show the difference:

[NateD4]

I think that's what I concluded on my 3900 injectors. It was tough to find 90 lb/hr that fit the stock packaging.

[3400-95-Modified]

90lb/hr...

This not sufficent?




All this injector talk makes my 28's sound small...

I think I'll be moving to a set of 42's sometime soon if my plans do pan out.

[NateD4]

Excess is always just enough lol.

[caffeine]

Well I bolted them into the lim today to see how they fit and I didn't need to shim anything to bolt the rail down. That being said I'm not 100% sure they are supposed to stick out of the ports as much as they do:

[Mars]

I'd be happy with that...

[NateD4]

That should be ok. I had the same concern when I got my injectors. If they stick out a bit that'll add a slight bit of turbulence and some mixing and more importantly get them into the flow.

Anyone else have input?