3500 and 3900 part swapping and specs

[mcgavinz26]

Long time no post. Hope you guys are all doing good.

I've done some digging for about the last hour now and have a handful of questions so I'll get right to them.

3900, LZ9 questions:
What is the fuel rail pressure?
What is the injector size? Delphi's website is worthless, or I'm blind
What is the exhaust manifold inner outlet diameter? This one

3500, LX9 vs 3x00 LZx parts
Are the LZx and LX9 fuel rails physically interchangeable?
Will the LZx exhaust manifolds bolt up to the LX9?
Are all 3900 and 3500 injectors the same physical dimensions? Interchangeable?

[caffeine]

I believe the LZx injectors have the same external dimensions as the LX9 injectors, and the exhaust manifolds do not interchange. Fuel pressure should be somewhere between 55 and 60 psi IIRC.

Fuel injectors for an LS2/LQx should be close to if not the same size. LS3/LS7LS9 injectors are shorter.

[mcgavinz26]

I believe the LZx injectors have the same external dimensions as the LX9 injectors, and the exhaust manifolds do not interchange. Fuel pressure should be somewhere between 55 and 60 psi IIRC.

Fuel injectors for an LS2/LQx should be close to if not the same size. LS3/LS7LS9 injectors are shorter.

So the LZ_ exhaust manifolds are the same, but do not bolt up to the LX9? Surprising.
LS2/LQ_ injectors are the same as LX9 or LZ9 injectors?

Another question I have is about the difference between injectors on the gas an flex fuel engines. Does anyone know of a good website or resource for looking up flow rates? I only plan on running gas, not E85, but my assumption is the flex fuel engines have higher flow ratings to support the extra fuel quantity needed.

Too many x's

[caffeine]

I don't know if the ls2 injectors are the same but they should fit LZ engines. The injectors I bought for my LX9 fit an Audi S4 2.7L TT and fit fine but are slightly longer.

LZ engines have a unique bolt pattern for the exhaust flanges. I have no idea if the ports are in the same location or if its possible to make dual bolt pattern flanges to fit both LZ and LX9 engines.

[mcgavinz26]

Anyone? Still wondering about those flow ratings. If this board doesn't know...

[mcgavinz26]

I think I found the answer with some help from a guy at work. He gave me this link: http://users.erols.com/srweiss/tableifc.htm
The part number that applies there is 12588610, which shows the 3.5 and 3.9, which makes sense. Then I did some part searching at rock auto to see what cars came with what parts. Basically, it looks like all the newer 3.5 and 3.9's have the same injector and they are rated for 27 lbs/hr @ 43.5PSI. But, the LX9 3500 has a different part number that seems to be exclusive to it. I can't find any numbers for it though. Since it was never an E85 application (from what I could find) and only for the 3.5, you can assume that it is probably around 20-22lbs/hr, roughly.

Then, using the Megasquirt fuel injector calculator (http://www.megamanual.com/v22manual/mfuel.htm) I did some rough math. For my application, if I use the E85 3.5/9 injectors, it should support about 300hp @58psi rail pressure in a forced induction application, which is what I'm eventually getting to.

If anyone knows of an injector that fits the 3500 fuel rail and is 30-35lbs/hr, please chime in!

[caffeine]

I have 52 lb/hr injectors on my 3.5 rail; they are the right size to fit a 2.7 TT Audi S4. Perhaps stock S4 injectors would work for you since they put out around 300 hp IIRC.

[mcgavinz26]

Wow. If you're using most of that you must be scooting pretty fast. Thats a DOHC engine though, so isn't the spray pattern split?

I was hoping to find something that was meant for a single valve application. Finding information about spray patterns or angles seems almost impossible though, unless you have any more magic links for me.

I glanced at Rock Auto's images of those Audi injectors and they look just like the 3400/3100 injectors. Are they actually the same height as the 3500 injectors?

[caffeine]

Like I mentioned earlier in the thread, LQ4/LQ9/LS2/L92 injectors should be the right height for the 3500/3900 fuel rails as well. What you're looking for is about 48mm o-ring seat-seat.

I got my injectors from CTS Turbo in Vancouver and they were listed as fitting an Audi S4 2.7.

[mcgavinz26]

Ok, thanks again. I finally pulled the engine and started the swap process a month ago and I've been kinda scatter brained through the process.