Stock fuel pressure on 2JZ and 1JZ

[2JZR31]

What pressures fuel do these engine engines run at? At at what pressure reference should it be tested at?

[FASTFOO]

About 35psi with high vac (idle) and about 45psi low vac (open throtle)
MATT

[2JZR31]

Cheers. Does anyone have any Toyota tech documentation about this?

Some people are telling me you must remove the vac feed to the FPR to test for 35 or so PSI.

[thechuckster]

as mentioned on PF, you set the base pressure with the vacuum source open to atmo..

from http://mkiv.supras.org.nz/injectors.htm

the Supra normally runs a base fuel pressure of 42 psi

My gut feeling is that it wont run as a high as that, as when on boost (e.g. 14-18psi) you're up to 56-60psi of fuel pressure which does seem a bit high - put more boost in and you head towards the 80psi limit (as determined by baseless internet fact) of the factory injectors


fwiw:

7MGE & 7MGTE
from http://www.1jz-gte.us/documents/SubDocs2/07_FI.pdf (8Mb PDF)
38-44psi & 33-40psi

lower pressure needed for the turbo engine courtesy of the bigger injectors, plus once you're on boost, the fuel pressure is above the static setting.

[2JZR31]

Cheers mate So the base pressure is 42psi referenced to atmo. There seems to be a lot of confusion regarding this. I was getting wildly varying results depending where I asked. I reckon the 42-45psi figures people a were giving are referenced to atmo and 35-38 are at idle vacuum, just like FASTFOO said. A few other people had the figures right but the conditions wrong.

The calc says my 550s will be good for 350rwkw through an auto with a 42psi base pressure with a 1.7:1 rising rate on a DD dyno with a 12:1 AFR. Sounds good

I reckon the "80psi" figure means nothing since pressure by its self has little relevance. Pressure difference is what matters. I reckon 80psi fuel pressure would be fine if you were running 30psi of boost. The injectors would only see 50psi pressure differential across them which is close to stock. Running 80psi at idle would be a different story.

[oldcorollas]

got healthy fuel pumps?

can they provide 2L/min of fuel at 76psi (assuming 20 psi boost)??
(walbro 255 = 29gallons at 80psi = not quite.. need 35gallons/hr to be sure)

[oldcorollas]

I reckon the "80psi" figure means nothing since pressure by its self has little relevance. Pressure difference is what matters. I reckon 80psi fuel pressure would be fine if you were running 30psi of boost. The injectors would only see 50psi pressure differential across them which is close to stock. Running 80psi at idle would be a different story.

nah, the differential pressure relates to fuel flow. the absolute pressure (i mean, the actual internal pressre of fuel inside the injector) relates to the maintainence of injector structure integrity, and sealing of the o-rings (in both top and side feed operation)

[2JZR31]

I got a 044 fuel pump.

nah, the differential pressure relates to fuel flow. the absolute pressure (i mean, the actual internal pressre of fuel inside the injector) relates to the maintainence of injector structure integrity, and sealing of the o-rings (in both top and side feed operation)

I agree. But I have never heard on an injector exploding because of fuel pressure. I guess it would be easy to test the O rings by cranking the pressure right up at idle with the FPR temporarily.

I was thinking more along the lines of the supposed phenomena where the injectors are held shut or open or something. That would have to do the pressure differential.

[Mr DOHC]

seen the vis or TRYHRD at summernats 2 years back, big inferno in the dyno cage, blew an injector oring, was a 1400hp TT commodore, , that would have to run some huge injector pressure

[BMWTurbo]

http://mkiv.supras.org.nz/injectors.htm

[thechuckster]

I reckon the 42-45psi figures people a were giving are referenced to atmo and 35-38 are at idle vacuum, just like FASTFOO said. A few other people had the figures right but the conditions wrong.

nope - that 35-38pi is the FPR seeing atmo NOT manifold vacuum.

at idle, you engine is pulling about -20 to -22 in-Hg vacuum (which is -11.07PSIg)

if you set the FPR at 42psi with the reference at atmo, at idle you should see rail pressures of about 31-33psi which is the static pressure minus the current manifold vacuum.

Am pretty sure a 2JZ does not pull -7PSIg vacuum at idle, but that's what your figures suggest.

[2JZR31]

Well then I guess the people saying 45psi are just plain wrong then? And the supra site is also wrong with 42psi?

You can probably see why I have made so many threads on it. I am still confused!

I would love to see the Toyota tech info for it.

So Chuck, your final call 35-38psi with reference to atmo?

[thechuckster]

my call is based on the mark II and mark III TSRM for Supras - that covers 5MGE thru to 7MGTE. They're genuine tech docs that are relevant for what you are testing.

I can post the URLs to them if needed.

Personally i think 42psi is too high if you run large amounts of boost. 45psi i call shennanigans on.

At 80+psi rail pressure, your o-rings are at danger of failure and you want a good 10-15 psi buffer between your maximum operating pressure and that limit.

[mrshin]

at idle, you engine is pulling about -20 to -22psi vacuum

That's impressive.


Global warming may be be affecting our weather, but I'm tipping we'll be well dead before it gets to this stage...

[thechuckster]

arrgh - my use of measuring units sucks - that should be -20 to -22 in-Hg vacuum

well on my ubercheap boost guage - idle (anywhere from 25-40kpa on the 18RTE) shows as -20 something - what units it's referring to is uknown...

Now a 2J should be pulling better vacuum at idle as it's not a shitty old engine like mine.

So if it's got 25kPa at idle, that (by this http://not2fast.wryday.com/turbo/boost_converter.shtml ) it should have:
-22.54 in-Hg vacuum or
-11.07 PSIg (0=atmo)