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Vacuum lines and gauge install Help to Newbs

Old 04-11-2008, 01:39 AM
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where would you pull reference for a FPR with boost 1:1
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Old 04-11-2008, 10:04 AM
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any source before the Throttlebody,otherwise sometimes its possible that when the car isnt in boost and is in vacuum the FPR will actually drop the fuel pressure according the vacuum.
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Old 05-13-2008, 09:52 PM
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all great info. ill be looking at this as i install my goodies. i have a question tho

you said that if you have an intercooler and ref. the waste gate off the turbo *say it has a 8psi spring in it* you would be getting less PSI to the motor, like say 6-7psi correct? and as long as i hook my boost gauge up AFTER the TB. i would be a correct motor boost reading?

im asking this becuse i have a stock lt1 and my w/g came with a .6 bar*8.7psi at sea level* and i was thinking if i reff it off the turbo i could get some boost drop threw the piping and intercooler and say run 6-7psi at the motor with out changing much...could this work or am i just being a silly teen?
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Old 05-13-2008, 09:57 PM
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Originally Posted by 94m6Z28 View Post
all great info. ill be looking at this as i install my goodies. i have a question tho

you said that if you have an intercooler and ref. the waste gate off the turbo *say it has a 8psi spring in it* you would be getting less PSI to the motor, like say 6-7psi correct? and as long as i hook my boost gauge up AFTER the TB. i would be a correct motor boost reading?

im asking this becuse i have a stock lt1 and my w/g came with a .6 bar*8.7psi at sea level* and i was thinking if i reff it off the turbo i could get some boost drop threw the piping and intercooler and say run 6-7psi at the motor with out changing much...could this work or am i just being a silly teen?
ive never heard of anyone purposely trying to get LESS boost but i think that would work....but theres no way to tell exactly how much less boost you would get.....wow that was a weird post
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Old 05-14-2008, 01:42 AM
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well. its my DD and id rather be safe then sorry *higher mile stock lt1*. PLUSS its always easier to turn the boost up from a lower point then it is to turn it down from a higher point so if its to low i can always up it..if its to high im kinda SOL becuse id rather not change the spring
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Old 05-14-2008, 08:53 PM
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Hey man, this is how I just finished hooking it up for the same exact reason. I say it will work too, I am waiting on parts at the moment so can't tell you for sure. One good thing about it is though I did read in a post from Jose at Forced Inductions and he said that is a good place to use as a reference.
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Old 05-14-2008, 11:27 PM
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ddnspider, is there anyway to keep the boost gauge from bouncing around between shifts. Or is that normal, never had a boost gauge so I am not sure. I have it referenced just before the TB, if that helps.
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Old 05-14-2008, 11:32 PM
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Originally Posted by D-Webz View Post
ddnspider, is there anyway to keep the boost gauge from bouncing around between shifts. Or is that normal, never had a boost gauge so I am not sure. I have it referenced just before the TB, if that helps.
the purpose of a boost gauge is to read positive pressure(whether it be in psi,kpa's,or bar) and if so equipped it can also read vacuum in inches i believe.im assuming youre a manual car and dont powershift,so when you shift the throttle shuts closed for a split second which drops the boost pressure.Then when you hit the gas again in the next gear it will take a short moment for you to reach full boost again(lag). thats why it fluctuates in between shifts.

EDIT...saw ur sig.you are a stick.and i see you have centrifugal blower.boost is based on RPM with those.so when u shift your RPM drops causing boost to drop with it and as rpm rises so will your boost gauge.
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Old 05-14-2008, 11:52 PM
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should it also be reffed after the TB not befor?
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Old 05-15-2008, 12:28 AM
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Originally Posted by ddnspider View Post
the purpose of a boost gauge is to read positive pressure(whether it be in psi,kpa's,or bar) and if so equipped it can also read vacuum in inches i believe.im assuming youre a manual car and dont powershift,so when you shift the throttle shuts closed for a split second which drops the boost pressure.Then when you hit the gas again in the next gear it will take a short moment for you to reach full boost again(lag). thats why it fluctuates in between shifts.

EDIT...saw ur sig.you are a stick.and i see you have centrifugal blower.boost is based on RPM with those.so when u shift your RPM drops causing boost to drop with it and as rpm rises so will your boost gauge.
I guess I should be more clear I understand all that. The needle flutters meaning it bounces from zero to whatever until I get into gear. It is not a smooth linear decrease like it is as boost is building. I figured it would be like any other type of pressure gauge where it would drop instantly and then increase again. I guess my question doesnt really matter if its normal for the flutter to occur anyway.
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Old 05-15-2008, 02:46 AM
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im thikning its becuse its infront of the TB. soo seeing boost to the motor. not the boost at the motor
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Old 05-15-2008, 09:29 AM
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for a turbo setup if u wanna see the boost level of the spring or whatever you reference it after the TB.for a centrifugal blower its rpm dependent.when youre between shifts the throttle plate slams closed so no air goes in,ie no boost.
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Old 05-15-2008, 10:39 AM
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Originally Posted by ddnspider View Post
for a turbo setup if u wanna see the boost level of the spring or whatever you reference it after the TB.for a centrifugal blower its rpm dependent.when youre between shifts the throttle plate slams closed so no air goes in,ie no boost.
I was just concerned that my bypass valve was not working properly hence the gauge flutter, thats why I was curious. As it turns out it seems to be working fine as I thought maybe I had a vacuum leak to the BP valve so i tested it out.

Thanks for your response
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Old 05-15-2008, 10:06 PM
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Originally Posted by ddnspider View Post
any source before the Throttlebody,otherwise sometimes its possible that when the car isnt in boost and is in vacuum the FPR will actually drop the fuel pressure according the vacuum.
not to be a jerk but that is actualy wrong what ever the pressure is in the intake manifold is what the engine is recieving and at idle when you are in vac. fuel pres. is supose to go down. If hooked up before tb when you boost your car and then let off your fuel pressure would go up when it doesnt actualy need the fuel so go real rich. if no cat u will belch flames which i cool but plugs burn up fast
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Old 05-18-2008, 10:46 PM
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Originally Posted by Shaine View Post
not to be a jerk but that is actualy wrong what ever the pressure is in the intake manifold is what the engine is recieving and at idle when you are in vac. fuel pres. is supose to go down. If hooked up before tb when you boost your car and then let off your fuel pressure would go up when it doesnt actualy need the fuel so go real rich. if no cat u will belch flames which i cool but plugs burn up fast
I disagree, as it seeing vac wil put even more of a delta pressure on the fuel pump. There is no need for it to be lower than the base pressure whatever it is that you set it at. Its the proper way to connect the regulator reference before the T/B.
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Old 05-20-2008, 10:19 PM
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well if it is a fully custom set up with flat longterm fuel maps only for race kinda car but if its a moded up street car thats how you want it. because thats how it is factory and it is simple tunning is much more of a pain a factory fuel system has a 1:1 fuel press. regulator that lowers pressure at idle because its after tb. now you hook it up before and when you let of throttle you get adverse effect a spike in pressure meaning you get more fuel and you just let off the throttle so the need for more fuel... minimal when you test for bypass accuracy on a dyno you hook a boost gauge up before tb and you wound be amazed when you are in boost at say 4,500 and let off thottle that tb slaps shut that air piles up so fast a 8 psi system can comanly spike to 18 before tb and with a 1:1 fuel pressure regulator it is not a big deal but if you have a higher ratio or a fmu after regultr say a 12:1 thats 216psi at 18 psi of boost pop you just blew a fuel line ask anybody who runs a shop that commanly supercharges or turbos f-body cars they will say all pressure refrence fuel componants need to go off after tb pressure because thats thats what pressure the engine gets
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Old 06-09-2008, 09:24 PM
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you pick a source BEFORE the throttlebody for a reference for a FPR so that it will only see boost.you will not see vacuum BEFORE the throttlebody.AFTER the throttlebody the intake manifold will see vacuum,therefore it can possibly drop your fuel pressure below the intended base fuel pressure causing you to go lean.Ive had the car on a dyno and have watched my fuel pressure gauge on the FPR when in boost vs no boost.having it before the throttlebody makes for less fluctuation in the fuel pressure so why complicate it more by having to tune for a larger range of fuel pressues.
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Old 06-09-2008, 10:22 PM
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question, can you reference the wastegate from the PCV port on the throttle body?
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Old 06-09-2008, 11:07 PM
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so long as there is no check valve.i dont recall if there is or not.
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Old 06-10-2008, 12:23 PM
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lol i was going to ask that too i dont think there is any check valve there just a straight opening to where the iac valve seats against
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