So you don't know for sure. One thing I realised a while back is that your a text book engineering kind of guy. I've unfortunately have had to work with professionals like you and can tell you that while a book or web site might give you some insight into the real world it doesn't tell the whole story.
BS Rick. I rent Gingermann Raceway in MI a couple times a year for testing. I test all sorts of systems (intake, exhaust, turbos, fueling, water cooling, suspension, awd, lockers) at Steamboat every year. Ask anyone in the audi arena, you are way off base. I am one to understand theory and applications of systems, it helps when I look at SC issues on the 80. Now, based on my knowledge of fuel systems, I KNOW that if you put 2 supra fuel pumps on the 80 with a 1/2in system feed line, and put a stock FPR on the truck, you have done nothing for the fuel needs of the truck. The only way that can work is if the FPR can't do it's job anymore because system pressure is too high (read: Fuel return). I KNOW that if someone wants to claim differently, there is no supporting documentation.
I personally respect most of the people on this site.
I respect all of the people on the site. I also can get very intense on what goes into the archives has some educational information in it. Here, there is no opinion to debate.
Christo claims that he doesn't need the Supra pump to support a turbo with greater fuel needs.
Others with the SC have seen a need for more fuel and claim the Supra pump works well.
So for a minute lets give these guys some respect and credit to their observations and digest this info for a minute.
I understand what folks did. I also have a pretty good idea what is happening, because you can't change HOW a fuel pressure regulator works, you can make it not work, and get more fuel.
So if the stock fuel pump can't keep up with the SC why can it then on a turbo with a greater appetite.
My conclusion is that there is a PSI drop in the fuel rail which will lean out on a SC but the extra injectors on Christo's turbo can deliver the needed fuel because the total flow through 8 injectors at the lower PSI is more than what's required.
NO. You can't increase flow with lower pressure on the same size line, that defies the laws of physics. No one has shown that the stock fuel pump can't keep up with the SC, only that a Supra fuel pump appears to.
So the only way to get the needed flow out of the 6 injectors is to increase the flow from the pump to maintain the fuel rail PSI. Which was the intended purpose of the Supra pump.
You jumped a step. Where is the DATA that shows that the stock pump can't meet the needs of the motor. It's fuel into the motor to meet demand, put 10 injectors in if you want. The pump can either do it or not. Added pressure to the system pressure doesn't give more flow to the injectors! Added pressure at the injector rail does that. More pressure to the system pressure only increases system pressure and flow, specifically flow back to the tank.
Now your concern is that the return line is restrictive enough to not allow the extra flow of the Supra pump to be bleed off to the tank during idling or other periods of low fuel consumption. This would seem to me to be a valid point and should be investigated.
Investigated? No, what should be TESTED, is the 'theory' that the Supra pump is doing what folks think, specifically, the stock pump is not capbable of providing the fuel. Read post #6
T-ing into the return line just after the fuel reg. and reading the pressure at idle with the relay jumped to the high side would be the first step, right. Because if it passed this test then all possibilities would be covered.
Seems to me it's time to put down the pencil and paper and take some real world readings. I'd be more than happy to do this however I'm not in a place with my truck to help.
Take the fitting off the FPR and measure system pressure. If you have system pressure and you have line diameter, you can math out flow. Or take the line off, measure the fuel pump output at 12v @ 1minute. That's total system cc/min. Divide by 6, that's fuel available to 6 injectors. IME, I'd put a bet that the total is more than double max engine demand at 43.5psi rail pressure.
The procedure for cking fuel rail pressure is in the FSM.
Then again maybe a 10 year old fuel pump is just weak with age and the new Supra pump is no better than a new stock one.
That's possible, as is the wires to the fuel pump have higher resistance since they travel some 15feet in the 80. I see this all the time in my shop. Regardless of pump, I'd be testing voltage at the pump, and fuel pressure (system and rail).
There is no question in my mind that the Fuel pressure regulator is the target FIRST. I respect the fact that folks *want* to believe the Supra pump is better. There isn' any data that supports that yet. Selling folks on the idea that it's a must do, is where I got into this mess. I didn't understand why, and I still don't, because the math doesn't add up, and no one has put forth any real world data to support it.
What I do find, is Christo's post #6 consistent with my math, and a lot of real world EFI system experience.
ST
