Max RWHP stock fuel pump will support?

[BLOWNGTS]

Have a Paxton on my '96 GTS. Have several small uprgrades added on the system (bigger injectors(50), fuel rails, smaller pulley(275) 4R tuning. The car is making 670 RWHP and 725 Lbs of torque at 5000 RPM's w/ 10 lbs. of boost. Now the problem comes in. The car basically shuts down at 5000 rpm's. I am thinking it has to be the fuel system since it is stock. The injectors are at 82% and the air fuel ratio is 12.4 when it shuts down. Also the map sensor hits 5 volts at 4500 rpm's. I have gotten this close I hope I do not have to put on a new fuel system. If I do can anyone help there, if not what should I try. I am thinking this car should make 750 RWHP. Help please.

 

[Anthony - 98 GTS]

You need to upgrade both the fuel lines and the fuel pump. You should also consider upgrading to a return system.

 

[proracer1]

pm me your phone #

 

[Joseph Dell]

You are definitely maxing out the fuel pump. You are probably also running extremely lean. Where are you taking the A/F readings from? If a dyno, then I trust it. It is is one of those autometer sensors, I don't trust those at all... too slow!

The bummer about the fuel system is that you need to plumb an entire system. yuck!

Good luck! but don't run too lean, especially the weather gets cooler!

JD

 

[utahviper]

Plan on spending $1000-1300 installed for an adequate fuel system.

The stock system is good until about 600RWHP. There are some that will do a little more and some that will do less. Good luck.

 

[Jack B]

Everyone wants to spend your money - don't just change the pump - get data first. It is so easy, have the dyno tech put a wide band in the front oem well (remove front O2), at the same time put a fuel pressure gauge in the system during the pull. You will now have the data to make a decision. An a/f of 12.4 on the dyno might be too lean due to your cylinder pressure, plus, the fact all cars tend to run leaner toward the end of the quarter.

A fuel system up-grade is easier said, than done. One more thing, change the fuel filter before the pull. It is located at the top of the frame rail, near the front of the driver-side wheel well. I am running similar hp with NOS and an a/f of 11.5. I did this with a stock pump. I did upgrade to the 255 Walboro, however, I do not think I needed it. If you find you need more volume, to the voltage boost circuit first. The pump upgrade is not easy or clean.

 

[DChan415]

Your 2.75" pulley only gives you 10 psi? Isnt that one full inch smaller than the original 6 psi pulley?

 

[BLOWNGTS]

Thaks for all the replies. Proracer I sent you an email. DChan remember that is only at 5000 rpm's. Tested on dyno. Jack B thanks for your imput also. Have done all advised. Just hoping there is a way around plumping a new fuel system. I would even consider a little less HP but the next size pulley up makes the belt rub the water cooler. I am sure these are standard problems just first for me. Thanks again guys. Matt

 

[Russ M]

I dont know what you use for fuel management, but one thing you could do is drop the fuel pressure. And bring up injector duty cycle, will raise the volume delivery of the pump.



What are you using to measure A/F?

12.4 is a good number on race fuel, if that is your a/f and you are loosing power at 5k perhaps its an ignition issue? Spark plugs to be exact? What are your plugs gapped at?

 

[BLOWNGTS]

Thanks a lot. I will check the plugs. I am not sure what the gap is I will check. If that is good what about the map sensor hitting 5 amps at 4500 rpm's. How do you correct that? Matt

 

[dansauto]

Plan on spending $1000-1300 installed for an adequate fuel system.

The stock system is good until about 600RWHP. There are some that will do a little more and some that will do less. Good luck.

$1300? heck I am double that!! Fuel pump $400, Rails $300, injectors $800, lines/fittings $200, regulator/filter $200, sump and baffle tank $200!!! That is to support 750 RWHP

 

[utahviper]

That is what I had to spend on my fuel pump, regulator, lines,connectors,filter, and install. My rails and injectors already supported the HP requirements.

I didn't get a baffle but I may need one.

 

[dansauto]

That is what I had to spend on my fuel pump, regulator, lines,connectors,filter, and install. My rails and injectors already supported the HP requirements.

I didn't get a baffle but I may need one.

So what are you doing in the stock tank? If you upgraded to an external pump you must be draining the cansister?

 

[utahviper]

We tapped the tank but I can't run the gas down to a quarter of a tank because it starts to cavitate? I need to do some redesigning. As long as I keep it above a quarter of a tank then I dont have any problems. All of the stock stuff is still in there.

 

[dansauto]

ok, I thoght about doing that, cause I don't want to take my tank out, but might as well just do it right the first time. Summit has the sump kit and instructions how to baffle, looks pretty simple. and is not expensive. I should have more fuel and boost than my stock motor can handle.