entropy
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posted December 09, 2006 12:36 PM
Quiz for the experts!
Anyone know the function of vac line to fuel pressure regulator???
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Y2KZX12R
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posted December 09, 2006 03:37 PM
Karl, they use a vacuum regulated fuel pressure regulator. I havent messed with the setup on the 12r, but the TPI and LT-1 chevy engines as well as a lot of others also used this system. Starting with the LS-1's chevy started to use a non vacuum referenced regulator. Basically at higher vacuum the fuel pressure drops and it rises with the loss of manifold vacuum.
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MadMike
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posted December 09, 2006 09:49 PM
to suck air....
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entropy
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posted December 10, 2006 12:23 AM
quote:
Karl, they use a vacuum regulated fuel pressure regulator. I havent messed with the setup on the 12r, but the TPI and LT-1 chevy engines as well as a lot of others also used this system. Starting with the LS-1's chevy started to use a non vacuum referenced regulator. Basically at higher vacuum the fuel pressure drops and it rises with the loss of manifold vacuum.
Jim,
thx for the info. I thought it was some kind of vac actuated bypass and hooked my Mytivac to see if vac/pressure opened it up. Nope. Hope I didn't damage it...
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Y2KZX12R
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posted December 10, 2006 04:28 AM
Na vacuum wont hurt it. you should see a fuel pressure change thou.
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entropy
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posted December 10, 2006 04:43 AM
i did it with the TB's sitting on the bench so i didn't see any pressure change; good to hear its prolly not damaged.
It looks like the RC 370's will fit after some fiddling to accomodate the extra length (and the fact that the fuel rail is close to the frame/airbox). I'm gonna try em.
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Y2KZX12R
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posted December 10, 2006 04:45 AM
 Edited By: Y2KZX12R on 10 Dec 2006 04:59
It tees off the vacuum line from the MAP sensor.
I was just looking in the book and it doesnt seem to drop very much pressure at idle.
specs are:
43 psi pump running engine off.
40 psi at pump cut out.
41 psi idleing
41 psi WOT
I'm not sure why they even bothered to vacuum reference the regulator. Dont the newer 12r's have the regulator in the tank and thus did away with a vacuum referenced regulator and a return fuel line?
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Y2KZX12R
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posted December 10, 2006 05:01 AM
Edited By: Y2KZX12R on 10 Dec 2006 05:01
Karl, you were saying you found a hat or a regulator that fits the 12r?
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entropy
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posted December 10, 2006 08:39 AM
Edited By: entropy on 11 Dec 2006 01:13
Jim,
Yep, DaveO steered me to a variable regulator 35-85#, a cute multicolored anodized piece o' $150 kit resting comfortably in my garage. If you want make & model i'll go to the garage.
BUT, if the RC-370's get my duty cycle down to 80% or a bit less (i'm guessing here), the variable regulator may not get used.
I spent the morning fiddling with the 370's and they DID fit 
(Doug Meyer convinced me to go straight to the RC's, rather than experiment with OEM's and a regulator)
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osti33
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posted December 10, 2006 06:14 PM
quote:
It tees off the vacuum line from the MAP sensor.
I was just looking in the book and it doesnt seem to drop very much pressure at idle.
specs are:
43 psi pump running engine off.
40 psi at pump cut out.
41 psi idleing
41 psi WOT
I'm not sure why they even bothered to vacuum reference the regulator. Dont the newer 12r's have the regulator in the tank and thus did away with a vacuum referenced regulator and a return fuel line?
Jim,
Yes. My 02 12 doesn't have a return fuel line and the reg is in the tank.
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capt10ed
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posted December 11, 2006 04:55 AM
The regulator is used to prevent the pump from pushing the needle off the seat at idle thus flooding the engine. (really high ressure fuel pump) I had to use one when I installed a worked chevy v8 into an FJ 40 Landcruser.
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Y2KZX12R
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posted December 11, 2006 03:43 PM
quote:
The regulator is used to prevent the pump from pushing the needle off the seat at idle thus flooding the engine. (really high ressure fuel pump) I had to use one when I installed a worked chevy v8 into an FJ 40 Landcruser.
This is fuel injection. No needle and seat here. The regulators job is to maintain 42 psi to the rail so the fuel can be metered by the injectors exactly as the ecu was programed.
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VincentHill
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posted December 11, 2006 06:43 PM
Karl, I did not post because I am no "Expert"! But my thought is that under Acceleration and the Vacuum is low I though it functioned like an accelerator Pump! allowed more fuel in
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ninja12
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posted December 12, 2006 07:17 AM
Can you apply air to the reg to increase fuel pressure?
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entropy
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posted December 12, 2006 09:10 AM
it would easy enough to test, but i sure have no idea.
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ninja12
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posted December 13, 2006 08:07 AM
I think SMW did something like that for the dry nitrous setup.
don't know if they used the stock regulator or aftermarket.
I would be interested in the results if you can make that part of your science project .
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entropy
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posted December 13, 2006 11:47 PM
quote:
I think SMW did something like that for the dry nitrous setup.
don't know if they used the stock regulator or aftermarket.
I would be interested in the results if you can make that part of your science project .
G.
maybe i'll do this lil experiment this weekend; more fun than putting up christmas lights!
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