Boost referenced fuel system installed, and functional
Thread Starter
Joined: Jun 2004
Posts: 1,501
Likes: 7
From: Ft. Irwin, California (But Virginia is home)
Boost referenced fuel system installed, and functional I wrote a thread recently about making a return style fuel system for my STS car with a boost referenced fuel pressure regulator. The reason for this is that the car was leanig out at high RPM's, a product of the injectors struggling to push fuel against the boost pressure.
Well, here's the completed project. Big thanks to my friend CAT3 for designing this setup. It uses the STOCK factory feed line and a return line plugged into the stock return port on the tank. THERE WAS ABSOLUTELY NO DRILLING OF THE FUEL TANK. The regulator keeps 58PSI at idle, and pressure actually INCREASES on quck throttle bursts. On gradual increases of throttle it remains about the same 58PSI.
Tuning will be done tonight or tomorrow. As of now the added pressure is actually making the car run a bit rich. Soon we'll have a how-to guide for those interested in doing the same.
Here's the pics. Enjoy!
Adjustable fuel pressure regulator hooked up:
Pressure at idle:
The complete under hood fuel system:
T-block capped with 14m 1.5thread fitting and 6AN cap:
Return line connected to fuel tak via a QD:
Return line run uder passanger side of car:
Well, here's the completed project. Big thanks to my friend CAT3 for designing this setup. It uses the STOCK factory feed line and a return line plugged into the stock return port on the tank. THERE WAS ABSOLUTELY NO DRILLING OF THE FUEL TANK. The regulator keeps 58PSI at idle, and pressure actually INCREASES on quck throttle bursts. On gradual increases of throttle it remains about the same 58PSI.
Tuning will be done tonight or tomorrow. As of now the added pressure is actually making the car run a bit rich. Soon we'll have a how-to guide for those interested in doing the same.
Here's the pics. Enjoy!
Adjustable fuel pressure regulator hooked up:
Pressure at idle:
The complete under hood fuel system:
T-block capped with 14m 1.5thread fitting and 6AN cap:
Return line connected to fuel tak via a QD:
Return line run uder passanger side of car:
Thread Starter
Joined: Jun 2004
Posts: 1,501
Likes: 7
From: Ft. Irwin, California (But Virginia is home)
Originally Posted by Blackbird
good lord, glad it's working good for you, but boy did you do it the hard way.
so the regulator you went with is only boost referenced? not vacum/boost?
so the regulator you went with is only boost referenced? not vacum/boost?
The regulator is an Aeromotive unit.
Looks more coplicated than it was. Planning took longer than constructing. There's about 5 hours of actual build time in the whole deal.
TECH Addict
Joined: Nov 2001
Posts: 2,659
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From: Bellevue, Wa
if it was vacum referenced as well then your pressure at idle will be below 58.
You set FP with the line disconnected right?
Once you then put the line on you should see FP read about 52 on the guage due to the vacum. Only time it will hit 58 is at 0 vacum then it should climb from there 1psi for every psi of boost assuming you got a 1:1 regulator.
You set FP with the line disconnected right?
Once you then put the line on you should see FP read about 52 on the guage due to the vacum. Only time it will hit 58 is at 0 vacum then it should climb from there 1psi for every psi of boost assuming you got a 1:1 regulator.
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Verdad Gallardo Thread Starter
Joined: Jun 2004
Posts: 1,501
Likes: 7
From: Ft. Irwin, California (But Virginia is home)
Originally Posted by Zombie
Unless he forgot to remove the in tank regulator.
And it is referencing boost on a 1:1 ratio. I didn't unhook the vacuum line before setting PSI, but I also set the psi by cycling the fuel pump..not just turning on the car and hoping for the best. It remains constant at 58PSI....till the engine revs up, and then pressure increases. Part throttle it remans the same at 58PSI. A quick rev will give a 2psi increase....and the car is still in vacuum at that point....which is what I thought you meant Blackbird when you asked if referenced vacuum too. Anyhow, despite the critics, it work just fine.....and looks decent too
. Last edited by Schantin; Jun 23, 2006 at 01:04 PM.
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Joined: Nov 2001
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From: Bellevue, Wa
not being a critic. actually asking questions that will help you in the long run.
so just be aware then if you set it with the line hooked up your base fp is NOT 58, it's more like 64, so set your IFR table accordingly otherwise your starting off with a big % error when you tune. simply unplug the vacum line to the regulator to find out exactly what your base FP is now set to. based on my experience it is, as I mentioned above, likely 64 or darn close to that.
so just be aware then if you set it with the line hooked up your base fp is NOT 58, it's more like 64, so set your IFR table accordingly otherwise your starting off with a big % error when you tune. simply unplug the vacum line to the regulator to find out exactly what your base FP is now set to. based on my experience it is, as I mentioned above, likely 64 or darn close to that.
Originally Posted by Blackbird
not being a critic. actually asking questions that will help you in the long run.
so just be aware then if you set it with the line hooked up your base fp is NOT 58, it's more like 64, so set your IFR table accordingly otherwise your starting off with a big % error when you tune. simply unplug the vacum line to the regulator to find out exactly what your base FP is now set to. based on my experience it is, as I mentioned above, likely 64 or darn close to that.
so just be aware then if you set it with the line hooked up your base fp is NOT 58, it's more like 64, so set your IFR table accordingly otherwise your starting off with a big % error when you tune. simply unplug the vacum line to the regulator to find out exactly what your base FP is now set to. based on my experience it is, as I mentioned above, likely 64 or darn close to that.
Blackbird, why do say its done the hard way? I only seen a few of these, asked around before, and kept most info in memory until Phil mentioned he wanted to fix his fuel vs. boost problem. I happen to be very proud of this setup and acting like King Kong when I got back to my Hotel room after installing it...wife was the beautiful girl ya know the rest, anyway. Working with Phil, I wanted to set this up for no cutting of the stock tank, module, etc.. and other than assmebling the actual AN Hose, its all plug-n-play (or glue-n-screw to more accurate). Hell, after posting on several boards I couldnt get an answer on the size of the fitting in the T Block...but now I know its 14mm 1.5 to 6AN.
Now, another part of this ultra long term project is Phil can run a -8 (or -10) feed line when he gets back from Iraq, and follow the same pattern we have started, utilizing stock locations etc..other than the larger hole that will be required in the top of the fuel module to adequately support a -8 or 10 hose, the rest will be glue-n-screw just like this.
Charlie
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Joined: Nov 2001
Posts: 2,659
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From: Bellevue, Wa
I will have to get the car in the air to take pics to show what I mean.
You did a fine job. Front mounting is definetly a bigger project.
If your not trying to squeze every last ounce out of your fuel system though mounting it out back is alot simplier and cheaper since you don't need a ton of fittings, braided line,etc....
In any case, no dis, I was just shocked to see all that was involved because it was done so differently.
Next time I am on the Island we should all hook up. Would be fun to see the car and maybe I can lend a hand. Been tuning for a number of years and I know the STS kit quite well too.
You did a fine job. Front mounting is definetly a bigger project.
If your not trying to squeze every last ounce out of your fuel system though mounting it out back is alot simplier and cheaper since you don't need a ton of fittings, braided line,etc....
In any case, no dis, I was just shocked to see all that was involved because it was done so differently.
Next time I am on the Island we should all hook up. Would be fun to see the car and maybe I can lend a hand. Been tuning for a number of years and I know the STS kit quite well too.
Thread Starter
Joined: Jun 2004
Posts: 1,501
Likes: 7
From: Ft. Irwin, California (But Virginia is home)
Originally Posted by Blackbird
not being a critic. actually asking questions that will help you in the long run.
so just be aware then if you set it with the line hooked up your base fp is NOT 58, it's more like 64, so set your IFR table accordingly otherwise your starting off with a big % error when you tune. simply unplug the vacum line to the regulator to find out exactly what your base FP is now set to. based on my experience it is, as I mentioned above, likely 64 or darn close to that.
so just be aware then if you set it with the line hooked up your base fp is NOT 58, it's more like 64, so set your IFR table accordingly otherwise your starting off with a big % error when you tune. simply unplug the vacum line to the regulator to find out exactly what your base FP is now set to. based on my experience it is, as I mentioned above, likely 64 or darn close to that.
Now...here's the problem. Get on the car....all is happy. Drive normally, all is happy. Come to a stop, the f'n car goes super lean and wants to stall, then overshoots and goes pig rich. I know why. The vacuum will overshoot from the 17in/hg at idle to 22in/hg or more during a decel. With the fuel pressure already at 51.5PSI at 17in/hg, it's dropping in the 40's (or less) on the overshoot/ or light load coasting at 22in/hg, and creating the lean condition (A/F about 16.5 to 17.5 to 1.....which is BAD for a turbo car.) It then skews the other way to a rich condition (about 12.5 to 13.0 to 1) as the vacuum returns to 17in/hg. Then it fluctuates from 13 to 16 to 1 trying to find the happy 14.7 to 1 ratio again, causing the car to surge at idle.
I could alter the tune at idle (richen it up), but then the short term fuel trims would be quite negative till decelerations to idle. When the PSI was set (with vacuum) to 58PSI, this problem wasn't apparent. The only difference was the car ran a bit rich at WOT, but nothing too crazy.
Anyow, that's the problem I had setting the fuel pressure as you described. Any input would be nice. Thanks.
TECH Addict
Joined: Nov 2001
Posts: 2,659
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From: Bellevue, Wa
as for the vacum dropping below 17 thats fine. what goes on with a vacum/boost referenced regulator is it maintains the proper FP based on whats going on at the intake. Like under boost, you have 5psi of pressure pushing against the fuel system so it increases FP by 5 psi to maintain the base FP in the manifold. Same with vacum, now under vacum there is a negative pressure at the manifold so again the FP regulator adjusts by now lowering the FP as less is needed to deliver the fuel and maintain the base FP.
Originally Posted by Blackbird
what does your IFR table look like now?
can you send me your .hpt file and I can take a look to see if I see anything blaring out at me.
can you send me your .hpt file and I can take a look to see if I see anything blaring out at me.
Thread Starter
Joined: Jun 2004
Posts: 1,501
Likes: 7
From: Ft. Irwin, California (But Virginia is home)
Originally Posted by Blackbird
as for the vacum dropping below 17 thats fine. what goes on with a vacum/boost referenced regulator is it maintains the proper FP based on whats going on at the intake. Like under boost, you have 5psi of pressure pushing against the fuel system so it increases FP by 5 psi to maintain the base FP in the manifold. Same with vacum, now under vacum there is a negative pressure at the manifold so again the FP regulator adjusts by now lowering the FP as less is needed to deliver the fuel and maintain the base FP.
Charlie.... the car's definetly liking the setup now. Each pull is getting stronger and stronger. Can actually feel the HP increase with each blast. Guesing this is the LTFT's learning themselves back to a low #.
I was testing this by going WOT at different (set) RPM's. IE 3K WOT, then 3.5KWOT. After a couple passes on a particular RPM, I could feel the car increase power on runs 3-4 at a given RPM launch. I can see that on the initial hits the car is quite rich after letting off the gas, will swing lean to copensate and then find itself in the 14 A/F range. By the 3rd or 4th shot, the swing is much reduced. 
Originally Posted by ls1CANTU
HERE ARE SOME PICS OF MY 99 TA, I DID A RETURN FUEL SYSTEM BUT ALSO RE DID THE FEED LINE AS WELL BUT I RAN MINE ON THE DRIVER'S SIDE.
