My $0.02 on V6 fuel rails

[5HTP]

These are the three types of fuel rails that I have encountered:

A: 3VZ rails, FPR/return hose, marked "1D" on each rail. AFAIK all 3VZ's use these rails.
They WILL NOT work on a 1MZ. They look like they should work, but the injectors do not seat properly the o-rings deform and leak (don't ask me how I know).

B: 1MZ rails with FPR/return hose, marked "1C" on each rail. Apparently you can only find these on 1996 1MZ's. Good luck.
This is the simplest and most cost-effective option for a 1MZ-Mk2 swap. Cut the crimp connectors at each end of the inlet line with a rotary tool, insert a slightly longer fuel line that will reach your fuel filter and hook up the return line. Done.

C: Returnless 1MZ rails, front rail is marked "1A" rear rail is "1B." These are what came on my 1997 Camry donor car and are found on all subsequent model year 1MZ's.
The simplest way to use these rails in a Mk2 swap (if option B isn't available) is to insert a tee fitting on the inlet line between the fuel pump and rail, with a FPR coming off of the tee. The fuel bled off of the FPR is sent to the MR2 return line. Done. No tapping the rail nonsense involved!

[AusV6]

Great work! So I guess you've been running this for a while now? No problems?

[Paul Woods]

We were aware of this but it's great to see the info condensed into one post, great work.

We tried to fit 3vz return style rails to a 1mz about 7 years ago based on information on a US forum that it would work, well we nearly had a serious engine bay fire as a result of this bad info, the 3vz rails look like they will work but the spacing is off by about 10mm, enough to fit the injectors but they are cranked at a slight angle rendering the O ring seal useless.

For that reason this deserves to be a sticky :thumbsup:

[MMaddict]

Whats the exact difference except the one is returnless and the other isnt? Any advantages - disadvantages ?

[AlunJ]

Returnless looks cleaner due to the lack of a return line and is slightly cheaper to initially manufacture due to the lower parts count & reduced number of machining steps.

Thinking about it there should be some benefits in terms of fuel pressure stability too as each rail is independantly supplied with fuel at the same pressure, with no long crossover pipes to cause restrictions and resulting pressure drops between injectors. But you could get the exact same improvement by replumbing A or B slightly, same as we do with flat 4's.

[MMaddict]

Returnless looks cleaner due to the lack of a return line and is slightly cheaper to initially manufacture due to the lower parts count & reduced number of machining steps.

Thinking about it there should be some benefits in terms of fuel pressure stability too as each rail is independantly supplied with fuel at the same pressure, with no long crossover pipes to cause restrictions and resulting pressure drops between injectors. But you could get the exact same improvement by replumbing A or B slightly, same as we do with flat 4's.

Cool, thnx for your thorough explanation! I already knew the advantages for the manufacturer since Im educated to set up production cells ;)

But now I also understand the advantages of each to its users :) And since I got a set of C's im quiet happy :P (Im talking about fuel rails :p )

[MRV6]

We were aware of this but it's great to see the info condensed into one post, great work.

We tried to fit 3vz return style rails to a 1mz about 7 years ago based on information on a US forum that it would work, well we nearly had a serious engine bay fire as a result of this bad info, the 3vz rails look like they will work but the spacing is off by about 10mm, enough to fit the injectors but they are cranked at a slight angle rendering the O ring seal useless.

For that reason this deserves to be a sticky :thumbsup:

Yes mate, bloody keyboard mechanics. Very dangerous especially when I had the bairn in the car with me.

[AusV6]

So my 3SGE was regulated at 33 - 38psi and a 1MZ is 38 - 44psi according to the BGB.

Anyone got a suitable inline regulator they could recommend?

[MMaddict]

So my 3SGE was regulated at 33 - 38psi and a 1MZ is 38 - 44psi according to the BGB.

Anyone got a suitable inline regulator they could recommend?

Why not the 1mz regulator?

[bigpitty1]

Why not the 1mz regulator?

If its the returnless fuel rail like I think the 1MZ's from 97 and on, the regulator is a part of the fuel pump assembly, this is what makes them returnless.
If you wanted to use a 1MZ regulator you'd have to get a earlier 1MZ fuel rail that has a regulator, from what I heard they can be used on all 1MZ's.

For a recommend regulator I used a SARD rising rate fuel regulator on my 3SGTE and will most likely use it on my 1MZ when its in, but if you don't plan on forced induction any adjustable regulator will be fine because then you can adjust the fuel pressure to where you want, rising rate is good for forced induction, the more boost you run it increases your fuel pressure higher which makes it a little safer and less likely to lean out.