need help, Fred, injuneer, in here please ? about fuel system

[azkkn]

been a while since i posted on the forum, because i sold teh camaro. i am trying to finishthe vette though and i am having a hard time with the fuel system. i got the FAST 1000hp kit and it says to use like 3 different sizes of line. i am running a 1992 LT-1 with a 96 LT-4 intake and fuel rail setup on it. the car is blown, with the FAST ECU and 65lb per hour injectors. question # 1, what size feed and return line should i use. i am thinking a -6 and a -8 but am really in the dark here. i also am trying to figure out the best way to hook the feed lines from the Y block to the fuel rails. are there fittings i can buy and thread the ends of the fuel rails? thanks for any input guys

[fastTa]

How much HP will this car make? If it is going to be in excess of 600-650 at the crank, I would go with a -12AN sump feed line to the first inline filter, -10AN supply, and a -8AN return.

I'm assuming being blown this thing is going to make some power. So the fuel rails really should be fed in parallel off of the y-block. Product Engineering, Aeromotive, and Earls all make quality fue;l products.

First you will need to remove the hard supply line. A cutoff wheel or die grinder with a cutoff disc work perfect. You can then drill the holes for the reducer AN fittings in the back of the rail. I would use a -10AN to -8AN for the parallel supply lines. The reducers fitting should be TIG welded to the back of the rail. You will obviously need to remove the crossover tube and TIG the holes shut as well.

[azkkn]

what about the return side of things? as far as comming off of the fuel rail?

[azkkn]

How much HP will this car make? If it is going to be in excess of 600-650 at the crank, I would go with a -12AN sump feed line to the first inline filter, -10AN supply, and a -8AN return.

I'm assuming being blown this thing is going to make some power. So the fuel rails really should be fed in parallel off of the y-block. Product Engineering, Aeromotive, and Earls all make quality fue;l products.

First you will need to remove the hard supply line. A cutoff wheel or die grinder with a cutoff disc work perfect. You can then drill the holes for the reducer AN fittings in the back of the rail. I would use a -10AN to -8AN for the parallel supply lines. The reducers fitting should be TIG welded to the back of the rail. You will obviously need to remove the crossover tube and TIG the holes shut as well.

thanks, got any pics of a setup like this?

[fastTa]

You are going to need a 2 port(bypass) regulator that has a boost reference port. I like the Product Engineering products. The boost reference regulator that they make for your application has I believe -10AN fuel ports. So again you would just need -10AN to -8AN reducers to accept the fuel lines coming off the fuel rails.

Also, the nice thing about running a 2 port bypass regulator is that you can make fuel pressure adjustments easily without the motor running if you wanted to. It will also help to eliminate any reverse pulsing and intermittent pressure spikes common with non-bypass setups.

[Injuneer]

I'm going to offer an alternative opinion here.... and its something I learned from a bunch of guys building 7-second Pro5.0cars, and 1,000+HP F-Bodies. My setup is a 205LPH Bosch pump in the normal in-tank position, and another duplicate pump off a sump in the back of the stock tank (the outboard pump only runs when the nitrous system is armed). Together, the system will support 1,000 (flywheel)HP.

The suction line for the outboard pump is a -10AN. The discharge lines from both pumps are only -6AN, and they go into an NOS "Y" fitting, and out as a SINGLE -6AN line. That line goes to an SX billet filter, and then continues as a -6AN line to the rear of the engine, where it splits through another NOS "Y" into -6AN lines into the back of each fuel rail.

At the front of the fuel rails, on the diagonal crossover pipe, there is a -6AN fitting welded on, with a -6AN line back to a Weldon AFPR under the cowl, and then a -6AN line back to the tank.

When these guys told me what they were going to do, I told them the supply line was too small.... they just sort of snickered, verfiying their opinion that I was just a know-it-all engineer, who didn't really know much at all. They were right. They were able to show me, and convince me that you do NOT want large diameter lines. Their reasoning was that the mass of fuel in the lines is subjected to the G's that the car is pulling on launch, and will actually cause the fuel system to have a sudden pressure drop, proportional to the mass of fuel in the lines. Less mass of fuel in the lines, the less pressure drop in the line, the more constant your fuel pressure stays at launch. And when you consider that an launch, with a 300-shot (dry - its all going through the injectors), I'd be at 5,000rpm and at peak torque/fuel comsumption, and losing fuel pressure just when I need it most.

I have seen them use a -10AN supply line, but that is for setups of 1,300HP and above. They also go to a return line off the end of each rail (rather than just one off the cross-over pipe) at the 1,000HP level.

Another consideration is the fuel system operating pressure. The higher the pressure in the system, the less variation you will get in fuel flow through the injectors for a given loss of pressure in the lines or rails. Even by minimizing the diameter of the supply lines to minimize pressure loss at launch, you still see some loss, but the affect of that loss can be minimized by maximizing the system operating pressure. I run 4bar (58psi) in my system, and that gives me more headroom on the 64# injectors, since they are flowing 78#/HR, and I see a duty cycle of no more than 70% at peak fuel consumption.

[fastTa]

On a forced induction motor, you are obviously going to want more fuel pressure. I have talked with and seen hundreds of logs of fuel pressure readings anywhere from a few of my friend's h/c LS1/LT1's to 1500 RWHP outlaw 10.5 cars (mostly mustangs). A friend of mine with a 1996 Camaro Z28 with a 409ci twin turbo LT1 making about 800 HP at the crank on a mild tune with pump gas have been using -10AN supply lines for years now. These guys have too much money burning holes in their pockets so they go all out when it comes to having all the high tech stuff. Their logs show no "loss" of fuel pressure when leaving the line with a -10AN supply line and a in-line pump with a pre-pump filter, a after pump filter, and a filter before the fuel rail. They are running 65 PSI and have never ever had a fuel pressure drop problem. And these cars ain't leaving soft.

Use your best judgement azkkn, but this ain't my first rodeo, and I am just trying to steer you in the right direction. At 65 PSI of fuel pressure, you are not going to experience a fuel pressure drop with your Vette. Just won't happen. Whether you choose to use -8AN or -6AN for the parallel supply lines off the y-block and the off-rail regulator feed lines is up to you. It is going to depend on how much boost and how much fuel pressure you heart desires.

[Injuneer]

I guess I really need to learn, as we've agreed in the past, not to even respond once you've posted to the thread. But he asked my opinion, and I gave it, in a way that I hoped wouldn't ruffle your over sensitive feathers. I didn't challenge you, I didn't say you were wrong, I didn't suggest you didn't know what you were doing.

I have learned, and I wll stay out of your way.

[fastTa]

I guess I really need to learn, as we've agreed in the past, not to even respond once you've posted to the thread. But he asked my opinion, and I gave it, in a way that I hoped wouldn't ruffle your over sensitive feathers. I didn't challenge you, I didn't say you were wrong, I didn't suggest you didn't know what you were doing.

I have learned, and I wll stay out of your way.

I am out to help all of my friends here on this board as much as I possibly can with my experience and knowledge. For some unknown reason personal to you, you and only you are the one who always seems to pick me out of a thread and ask why it is that I felt like you challenged me. I'm not sure why you always insist on trying to make me out to be the bad guy here. You made the mistake of thinking I was replying directly to your response. I was not. If that had been my intention, I would have used the quote feature hence the reason it is there. Sounds like it's not my feathers that are sensitive.