rerference sources
Sep 4, 2008 | 01:08 AM
#1
rerference sources
alright i read the sticky on tech and it seemed like a typical argument on tech. im trying to get solid answers on where to reference my sources from.
wastegate.....before or after TB?
......when using a EBC is wastegate before or after TB
1:1 FPR is it before or after TB
i know the boost gauge and BOV are after TB
wastegate.....before or after TB?
......when using a EBC is wastegate before or after TB
1:1 FPR is it before or after TB
i know the boost gauge and BOV are after TB
Sep 4, 2008 | 06:45 AM
#2
Everything should be after the TB.
If you aren't running an intercooler, or don't care about the psi you loose from the intercooler, you can pull the WG reference off the snail shell itself, but it's just as easy to block that one, and pull from the manifold.
If you aren't running an intercooler, or don't care about the psi you loose from the intercooler, you can pull the WG reference off the snail shell itself, but it's just as easy to block that one, and pull from the manifold.
Sep 4, 2008 | 07:40 AM
#3
buy you something like this: http://www.full-race.com/catalog/pop...71829b36a55fa5
install it on the firewall...hook it to the vac port on the left side of the manifold and run all your other stuff from it....very nice!!!!
install it on the firewall...hook it to the vac port on the left side of the manifold and run all your other stuff from it....very nice!!!!
Sep 4, 2008 | 10:39 AM
#4
alright but im going to question your post just cause im ignorant to subject. on tech the guy says that teh FPR should be before the TB. so it makes Idling easier to tune.. now not knocking you just trying to understand. since its a sticky i just want to do this right the first time
Sep 4, 2008 | 11:03 AM
#5
If you put the FPR before the throttle body you will see boost only, not vacuum. You want to be able to see both. When the FPR sees vacuum it drops the fuel pressure, which should make it easier to tune the idle and part throttle stuff, especially with large injectors. Do you have a link to the thread on tech? The guy you're talking about sounds like he doesn't know what he's talking about. I can't see any reason why you would want to isolate the FPR so that it sees boost only.
The whole point of a regulated fuel pressure system is so that the pressure differential between the manifold and the injectors stays constant whether under vacuum or boost, which allows you to run a flat IFR table in the tune, rather than the sloped one that the returnless guys have to use.
The whole point of a regulated fuel pressure system is so that the pressure differential between the manifold and the injectors stays constant whether under vacuum or boost, which allows you to run a flat IFR table in the tune, rather than the sloped one that the returnless guys have to use.
Last edited by thunder550; Sep 4, 2008 at 11:12 AM.
Sep 4, 2008 | 12:32 PM
#6
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Sep 4, 2008 | 01:04 PM
#8
Sep 4, 2008 | 01:41 PM
#9
Here's what I posted in there, for anyone who is interested:
I know this is an old post, but I just saw it and wanted to put in my 2 cents. Putting boost pressure only to a FPR is wrong....the purpose of running regulated fuel system is so that the pressure differential between the fuel system and manifold remains constant, so that the injector flow rate is always the same.
My explanation here will be a little bit lengthy, but hopefully will make this make sense. Let's say for a minute that you fix your fuel pressure at 58 psi on your fuel pressure gauge. When your manifold pressure is equal to atmospheric pressure (meaning you're at 0 vacuum, 0 boost), you are getting 58 psi pressure differential between the intake manifold and the fuel system.
Now, let's say that your car is sitting there idling somewhere around 16 hg-in of vacuum, which I believe is somewhere around -7 psi. Now, the pressure differential between your fuel system and intake manifold has gone up to 65 psi. You can think of this as vacuum in the intake manifold helping to "suck" fuel out of the injectors, making them flow more fuel than when the intake manifold was at atmospheric pressure.
Conversely, if your manifold pressure is positive (meaning that you're in boost), the pressure differential between the fuel system and your manifold drops. If you're at 6 psi boost, now the pressure differential is 52 psi, meaning that the injectors will flow less because the positive pressure in the manifold is pushing against the flow of fuel.
The example above is the scenario that cars with returnless fuel systems experience, which is why in the tune they use a sloped Injector Flow Rate table. The flow rate of the injectors changes with manifold pressure.
Now, let's look at a pressure regulated return style fuel system. We'll use the same base fuel pressure reference, 58 psi at 0 manifold vacuum. What the 1:1 FPR does is adjust the fuel pressure so that the differential between fuel pressure and manifold pressure remains constant. When you get into boost, fuel pressure goes up. At 6 psi boost, your fuel pressure would go up to 64 psi, so you still have the same 58 psi pressure differential. At -7 psi vacuum, your fuel pressure would go down to 51 psi, which still keeps the pressure differential between the fuel system and manifold the same.
That is the whole point of the 1:1 FPR. If you hook it up to a boost only source, you are defeating the purpose of using this type of system. It needs to see vacuum and boost, which means that it needs to be hooked up behind the throttle body.
My explanation here will be a little bit lengthy, but hopefully will make this make sense. Let's say for a minute that you fix your fuel pressure at 58 psi on your fuel pressure gauge. When your manifold pressure is equal to atmospheric pressure (meaning you're at 0 vacuum, 0 boost), you are getting 58 psi pressure differential between the intake manifold and the fuel system.
Now, let's say that your car is sitting there idling somewhere around 16 hg-in of vacuum, which I believe is somewhere around -7 psi. Now, the pressure differential between your fuel system and intake manifold has gone up to 65 psi. You can think of this as vacuum in the intake manifold helping to "suck" fuel out of the injectors, making them flow more fuel than when the intake manifold was at atmospheric pressure.
Conversely, if your manifold pressure is positive (meaning that you're in boost), the pressure differential between the fuel system and your manifold drops. If you're at 6 psi boost, now the pressure differential is 52 psi, meaning that the injectors will flow less because the positive pressure in the manifold is pushing against the flow of fuel.
The example above is the scenario that cars with returnless fuel systems experience, which is why in the tune they use a sloped Injector Flow Rate table. The flow rate of the injectors changes with manifold pressure.
Now, let's look at a pressure regulated return style fuel system. We'll use the same base fuel pressure reference, 58 psi at 0 manifold vacuum. What the 1:1 FPR does is adjust the fuel pressure so that the differential between fuel pressure and manifold pressure remains constant. When you get into boost, fuel pressure goes up. At 6 psi boost, your fuel pressure would go up to 64 psi, so you still have the same 58 psi pressure differential. At -7 psi vacuum, your fuel pressure would go down to 51 psi, which still keeps the pressure differential between the fuel system and manifold the same.
That is the whole point of the 1:1 FPR. If you hook it up to a boost only source, you are defeating the purpose of using this type of system. It needs to see vacuum and boost, which means that it needs to be hooked up behind the throttle body.
Here's a visual reference for those who are more visually inclined. Pay attention primarily to the red pressure differential line.
You can see that using a boost only source really messes with the pressure differential, which means your injector flow rate table in your tune would have to be a hybrid of constant and sloped to make it work correctly. You could do it, but you would have to make provisions for it in the tune. Much easier to just change the pressure source to behind the throttle body so it sees vacuum, plus lower fuel pressure at idle will make the injectors (especially the big ones needed for FI applications) easier to tune at idle and part throttle. It's also easier on the fuel pump, since it's not having to supply fuel at quite as high of pressure.
You can see that using a boost only source really messes with the pressure differential, which means your injector flow rate table in your tune would have to be a hybrid of constant and sloped to make it work correctly. You could do it, but you would have to make provisions for it in the tune. Much easier to just change the pressure source to behind the throttle body so it sees vacuum, plus lower fuel pressure at idle will make the injectors (especially the big ones needed for FI applications) easier to tune at idle and part throttle. It's also easier on the fuel pump, since it's not having to supply fuel at quite as high of pressure.
Sep 4, 2008 | 01:42 PM
#10
alright but im going to question your post just cause im ignorant to subject. on tech the guy says that teh FPR should be before the TB. so it makes Idling easier to tune.. now not knocking you just trying to understand. since its a sticky i just want to do this right the first time