What is the purpose of the front vacuum switch under the intake manifold that has 2 vacuum connections on it? I know the other switch in the rear is for EGR, but what is the front one for? Seems to me like I remember seeing it had something to do with the fuel system. Any help would be appreciated, thanks guys.
Question on Mystery vacuum switch under intake
- Thread starter SupraMan1987
- Start date
SupraMan1987;1438189 said:
your afpr will need a vacuum feed to raise FP by 1:1 (every extra psi in your manifold should equal one extra psi of fuel pressure).
edit:
Not to be an ass or something but when you don't know the purpose of a VSV for fuel, please start reading every bit of information about this subject before upgrading with a walbro and afpr.
If you don't, you'll kill your engine because you don't really know what your doing.
My 2 cents.
I was questioning Toyotas purpose of putting it there. I know perfectly well how to install a Walbro, and an AFPR. I just didn't know if it was something emissions related with the fuel system, or if it was an actual necessary component. What exactly does it do? The switch that is. Just signal for higher voltage to the fuel pump at start up?
No, it changes your fuel pressure on startup by allowing the FPR ambient pressure instead of manifold pressure.
GrimJack;1439144 said:
So it makes you run rich for awhile? What are the negitives with removing this?
It acts with the same principal as the cold start injector. The fpr rises 1:1 with boost and falls 1:1 with vac. The valve keeps vacuume from the fpr for start up so it has the fuel required to start properly/smoothly.
I havnt run one since I first pulled my motor 3 years ago and never had an issue in my experiace.
Possible side effects of removing are longer crank time and/or stumble on startup.
I havnt run one since I first pulled my motor 3 years ago and never had an issue in my experiace.
Possible side effects of removing are longer crank time and/or stumble on startup.
I disabled mine also. No bad side effects yet. Sarts and runs hard when its cold out, but smooths right out when the engine warms up.
^If it doesn't run right it isn't the fault of any startup equipment (CSI or the FP up VSV). Both are only operational with the key in "start" AFAIK.
mkIIIman089;1439470 said:
I know the CSI is wired that way but i believe the VSV is controlled from other variables.
Confirmed http://www.cygnusx1.net/Supra/Library/TEWD/MK3/manual.aspx?S=Main&P=45