Flow capacity of stock fuel lines and integrated fuel rail

[dyc1077]

Guys,

At what point do the factory fuel lines and integrated fuel rail run out of flow? I am wondering if I can just get upgraded drop in injectors and dual in tank fuel pumps to support max 750 rwhp. Will the factory fuel lines and fuel rail support the need flow?

 

[AndyMac]

Short answer, yes.

What year/model car do you have? It's a lot easier to change the fuel pump in the GTS.

Either way, you can easily make 800whp with side feed injectors in the intake. Been done lots with great success, and there are a few different options on how to get there.

Later,

 

[dyc1077]

I have a 1999 gts. Paxton is getting installed but I want to start thinking about what to do if I up the boost or want a more robust fuel system but don't want to break the bank.

 

[coupe]

I wouldn't even mess with the factory feed-line; it's pretty tiny. I used a -10 from tank Y'd into two -8's, each of which connected into the back of the intake (there are plugs that can be removed to access the fuel passage). Then removed factory feed line and re-threaded there for a return line. Worked like a champ with 60lb/hr side feed injectors.

 

[AndyMac]

Side question coupe, did you run a line at the front of the manifold to equalize the rails? I believe there is just a cross over in the rear. I am planning to do what you mentioned, but was thinking of drilling and tapping the rails at the front for a cross over line. (maybe even tee in the regulator there)

 

[plumcrazy]

at 750rwhp, id be more concerned about valve springs. but coupe gave some great info

 

[Viper Specialty]

at 750rwhp, id be more concerned about valve springs. but coupe gave some great info

Valve springs are far more susceptible to RPM increases than horsepower itself. If trying to make power at the 6K mark+, then it becomes a concern... all depends how high you rev with your setup. Theoretically, you could make 2000 horsepower at 5000 RPM on stock springs, and the springs wouldnt really care.

That being said, stock springs & retainers are VERY heavy, and dont like anything much over low-mid 5's. Any car revving to 6K+ will see improvements from a more stable valvetrain.

 

[plumcrazy]

pffft, thats what i said

 

[coupe]

AndyMac...I did not connect the front of the fuel passages, but it would definitely work fine.

 

[FastMatt]

My heads/cam/paxton car is making 873 rwhp on the stock lines. I'm running the stock in tank pump with a KB boost-a-pump on it and the 2 Walbro HP 255 pumps in line and Paxton FMU, with 46lb/min injectors in the stock location.

 

[AndyMac]

My heads/cam/paxton car is making 873 rwhp on the stock lines. I'm running the stock in tank pump with a KB boost-a-pump on it and the 2 Walbro HP 255 pumps in line and Paxton FMU, with 46lb/min injectors in the stock location.

I was thinking that this combo would be good for around 1000whp, and if you remove the parasitic loss of the supercharger, then it would be damn close.

So Matt, what fuel pressure are you running at max boost? (or what is your max boost and FMU ratio). Thanks!

 

[AndyMac]

I was thinking that this combo would be good for around 1000whp, and if you remove the parasitic loss of the supercharger, then it would be damn close.

So Matt, what fuel pressure are you running at max boost? (or what is your max boost and FMU ratio). Thanks!

Actually my calcs were with 600cc/min injectors. 46lb injectors seem borderline for those numbers.

 

[dyc1077]

My heads/cam/paxton car is making 873 rwhp on the stock lines. I'm running the stock in tank pump with a KB boost-a-pump on it and the 2 Walbro HP 255 pumps in line and Paxton FMU, with 46lb/min injectors in the stock location.

is the KB boost-a-pump very different than what the paxton fuel set up comes with? are those in-line walbro pumps the ones that the paxton kit comes with? what are you using to adjust the fuel maps for the 46lb injectors? what injectors are they?

 

[FastMatt]

I was thinking that this combo would be good for around 1000whp, and if you remove the parasitic loss of the supercharger, then it would be damn close.

So Matt, what fuel pressure are you running at max boost? (or what is your max boost and FMU ratio). Thanks!

I had to play with the FMU disks a bit to get everything right. I bought the FMU tuner kit with all the Disks. It was a wile back but I think I ended up with the 4 to 1 FMU disk in there I'll need to check what disk in missing out of the kit. I change it so many times I cant remember lol. But I ended up removing the spring from the FMU too. I'm only running 6.5psi of boost (the car made 612 rwhp all motor with the striker heads/cam and it's 11.1 to 1 comp, so it did not take much boost to really kick up the power) . But my fuel pressure at full boost is right about 75-80psi at full boost (From what I have seen the boost to FMU ratio of the Disks is more Approximate then Exact for that disk you use). With playing with the FMU and with Chris from DC's help with E-mailing me changes to my tune based on my feed back we were able to get my A/f perfect, 11.5-11.6 at WOT.

I'm running the 3.25" pulley right now, I'm thinking the 3" pulley would get me very close to 1000rwhp if I dont run out of fuel.

 

[FastMatt]

is the KB boost-a-pump very different than what the paxton fuel set up comes with? are those in-line walbro pumps the ones that the paxton kit comes with? what are you using to adjust the fuel maps for the 46lb injectors? what injectors are they?

The KB boost-a-pump is a volt booster that brings the V up to 18V on the power line to the stock pump when I get into boost.

I'm using the SCT tuner, with a E-mail tune from DC performance. I got the Side feed injectors from DC I dont remember what brand they were.

 

[FastMatt]

Actually my calcs were with 600cc/min injectors. 46lb injectors seem borderline for those numbers.

Not if your running 75+psi to them with a FMU....

 

[AndyMac]

Not if your running 75+psi to them with a FMU....

46lb injectors at 75psi = 60.4 lb/hr
1000 flywheel hp with 100% duty cycle and a BSFC of .65 is showing a required injector size of 65 lb/hr.

Also, if we factor in the boost pressure working against the fuel that the injector is trying to inject, your injector flow rate goes down.

With my 550cc(rated at 43.5psi) injectors at 60psi (that is about 61 lbs/hr), I was running out of fuel at 700whp. I was also running 680cc/min of methanol as well.

Can't argue with your results though, very impressive.

 

[FastMatt]

46lb injectors at 75psi = 60.4 lb/hr
1000 flywheel hp with 100% duty cycle and a BSFC of .65 is showing a required injector size of 65 lb/hr.

Also, if we factor in the boost pressure working against the fuel that the injector is trying to inject, your injector flow rate goes down.

With my 550cc(rated at 43.5psi) injectors at 60psi (that is about 61 lbs/hr), I was running out of fuel at 700whp. I was also running 680cc/min of methanol as well.

Can't argue with your results though, very impressive.

Good Example of the difference between what works on paper and what works on a car being quite different. Those fuel calculators have always seemed to be quite conservative IMO. If you take a car like the Dodge stealth and plug them into it the cars stock injectors cant even support the power the car makes stock, and in the real world you can add about 110 hp to the wheels to that car with the stock injectors still in place.

I'll give you a better one, my 8.7@168mph 1/4 mile stealth put 1093hp to the wheels on SIX 1000cc injectors (1000cc rated at 43psi and I was running 50psi base).