Fuel System setup for 4agte

[dangdang]

Dead time on the injectors you mean?

What is the stock 4age regs rail psi?

So as I understand the stock reg will give me 1psi more for every pound of manifold pressure above ?zero? (14 odd above absolute)?

[oldcorollas]

rising rate is never really a good option

say you have 1.7:1 and 20psi boost.. thats an extra 14psi +20 + base = 74psi?
injectors have no need for the extra pressure, and it will reduce your pulse width a bit with the higher pressures.. if your pump is happy to keep up flow at those high pressures...

most toyota (and many other?) regs are set at 40psi ish

there is no reason to go rising rate, unles you are trying to do an old-school job of boosting an NA motor with an NA ECU and a MAP interceptor....

yes, most regs should be 1psi per psi of boost and 1psi less with every psi of manifold vacuum
so you'll probably have 40psi with engine off, 32-35 with engine idling, and 60psi wth 20psi boost.

ie, always 40psi pressure differential across the injectors.. which is how they are supposed to work

[fixeruperer]

just get it tuned so you dont need to run a 1:1 reg, if your injectors will do it. the reg will handle any boost.

the stock reg is set at around 38psi.


haha i took too long to answer, OC..

[oldcorollas]

1:1 reg IS a stock reg

here is why you don't want a rising rate reg with a Walbro pump...(above 70psi line pressure)
the bosch are generally better at maintaining flow with pressure, but will pull a lot of power (as is needed)

[fixeruperer]

haha, i didnt know that actually. i thought it cut a little over 40psi.

[dangdang]

ACE!!! That just helped demystify that greatly for me!

Thanks guys

One more thing, any recommendations for some new 550cc injectors?

I was quoted a fairly obscene price of $160 for Bosch topfeeds and a more reasonable $110 for siemens which are actually slightly larger at 600cc.

Would I lose any tuning resolution worth worrying about with the 600's?

[fixeruperer]

ask your tuner, they have tuned most things and know what tunes easy.

[dangdang]

Good point, I will get in his ear tomorrow and pick his brains a bit

[oldcorollas]

haha, i didnt know that actually. i thought it cut a little over 40psi.

nah, the manifold pressure reference will reduce the fuel line pressure by the amount of "vacuum" in the manifold OR the amoutn of pressure, such that the pressure difference between manifold and fuel line will always be the same, ie 40psi..

so with 5psi vac in manifold you have 35psi line pressure, and 30psi boost would have 70psi line pressure

[dangdang]

But will the factory 4age reg give 60+psi pressure?

[oldcorollas]

toyota 3SGTE has 550CC injectors (iirc).. probably aroudn $130-150 each?

$160 for a new injector is not obscene... considering the importance of the part in the performance (and life!) of your engine

[oldcorollas]

But will the factory 4age reg give 60+psi pressure?

don't see why not... the diaphragm in it will still have the same pressure difference across it...

the usual question is "will it flow enough at idle, to keep fuel pressures down"

you can test it by running the pump and putting 20psi on the reference line (bith bike pump or something?) and see what happens to the pressure.

i'd trust a stock one over some of the aftermarket ones (and their common copies on egay)

[dangdang]

So you mean it may struggle at lower revs with the increased volume?

Obscene was a bit tongue in cheek I know the Bosch gear would be top notch

[oldcorollas]

i don't know how much a stock fuel reg can flow, but chances are it is a fair bit.

it needs to pass the highest flow when the car is at idle, since fuel consumption is lowest, and fuel flow from the pump (at the reduced line pressure) is highest.

at WOT, your injectors will be using a lot of fuel anyway, so there is less for the reg to return at the higher line pressure

[fixeruperer]

i dont know what the stock reg can flow either, but ive never heard of an issue before with them, i just didnt like the tiny line that came out of it.