Fuel System Problems at 202HP

[DarkFalcon]

I found an interesting specification in the service manual: fuel pump discharge for the Busa over one hour is 68.7 quarts or 17.2 gallons/hour at 43psi. Assuming the weight of gasoline to be 75% of that of water, one gallon of gasoline would weigh 6.2 pounds; thus the Busa fuel pump releases around 107 pounds of fuel in one hour. In the fuel injector world, it usually assumed that one NA horsepower requires .45 pounds of fuel over the course of one hour; thus, 107 pounds of fuel/hour should be able to support a maximum of 238HP at 100% injector duty cycle. At 85% duty cycle, which is the recommended maximum for continuous operation, the maximum support would be reduced to 202HP. If this line of thinking is correct, it could explain many issues, including the range of results achieved with 1397's and larger motors. Above 202HP, a bigger fuel pump may offer more than a larger set of cams

[THEMOTORHEAD]

EFFICIENCY DICTATING THE BSFC WILL HAVE A BIG PART IN THAT
MOST STROKERS ETC ARE RUNNING PUMPS AND REGS NOW
AND YES YOU DRIVE HOME A VERY GOOD POINT

[DarkFalcon]

quote:Originally posted by MOTORHEAD:
EFFICIENCY DICTATING THE BSFC WILL HAVE A BIG PART IN THAT

I agree but I had to start somewhere. It could also help explain some of the differences in big bore kits with identical designs; the so called good ones may just have better fuel pumps within the range of factory tolerances.

[dragzooks@indy]

i definitely agree with you on the fuel system not supplying enough fuel for the big engines/hp numbers

every 1397 i do that has the early model stock fuel system (external pump)seems to quit making power around 205hp

you add the later model in tank set up and it helps sometimes

aftermarket pump/regulator seems the way to go

[BlackBusaRookie]

I hope one day maybe I can understand all of that.  Wow.      

[fastby busa]

WERE OR WHO IS MAKING AFTERMARKET PUMPS THAT WORK FOR UP TO 300 HORSEPOWER AND I HAVE HEARD A FEW GUYS TURNING UP THE STOCK REGULATOR BUT BY WHAT YOU SAID EARLIER IT STILL WONT BE ENOUGH I HAVE A 03 WILL THAT SYSTEM WORK DUE TO THE FACT IS SEQUENTIALY FIRED IT WOULD BE MORE EFFICIENT BUT DOES IT HAVE ENOUGH EFFICIENCY

[Steve A]

Almost any inline automotive FI pump will work!

[SlammedStance]

welcome guys i have been running a fuel pump and reg for over a year now on big motor picked up over 6 mph on my stock bore like 1-2 mph  

[AssAbuser]

Where and how much can we get this aftermaket pump and regualtor set up does anyone have some pics?? I am in Dire need of one...

[Steve A]

Summit has a raft of the stuff!!!

[SlammedStance]

around 500.00
i have a trex pump and a aero reg

[DarkFalcon]

Slammed
Did you experiene any mapping difficulties and/or end up with alot of negative values in the map matrix when you went to the Trex? And how much does the pump flow?

[AssAbuser]

Which regulator do you have?

[SlammedStance]

i ahve the aero reg high pressure. No prob mapping it i started with a base map and tuned with a a/f meter on the road.

[DarkFalcon]

I'm thinking out loud here. I have not run the math but I would think that you would not want to increase the pressure much above 50psi along with a pump that will move .5 pound of fuel per HP for your set-up. Example: a 250HP motor would need a pump that releases 125 pounds per hour, while a 300HP motor would need a pump that releases 150 pounds per hour. The .5 is BSFC, a commonly used factor.

[AssAbuser]

Steve I can't remember what you told me to set the pressure at was it 58??

What pressure would be ideal for about 260 on motor?

[SlammedStance]

try around 47-48 idling should jump to 50-51 when ya wack it. yer gonna have to get it dyno tuned it will be too fat down low

[AssAbuser]

I will try that did you go with aftermarket injectors and fuel rail?

[SlammedStance]

ya dont need it

[SlayerZ]

Really interesting Information... Thanks Dark Falcon For bringing this up....        

So now,lets talk about the 1397 with cams (most say they make 210-220) does that mean people who claim they are making these figures on the stock fuel system are wrong        . Or if it’s true that means their pushing their injectors to over 85%?

Reading from previous posts it seems that people are making 1397 motors run rich on the stock fuel system. How come you need to upgrade the fuel system when you can make 1397 motors run rich on the stock fuel system?        

If so would the solution be to increase the size of the fuel pump? Also wouldn't going up on the pump size create more flow causing an increase in the injector duty cycle? If that’s true then do I need to go up in injector size?

What I’m wondering is what would it be the best fuel pump and injector combination? and keep in mind that we don't want to max out the injectors, keeping them at a 60-65% duty cycle

Correct me if I understood anything wrong, but my point is that would you need to upgrade the fuel pump and injectors on a 1397 motor.

[SlayerZ]

[SlayerZ]

[DarkFalcon]

It would appear the current pump and regulator can support up to 238HP; beyond that point, the fuel delivery is simply insufficient to accomodate additional power. Between 202 and 238, the injectors are working above a desired cycyle limit and will, among other things, get sloppy and overheat. They can keep up though in the dydno room during short bursts and can be tuned as well under these conditions. It is at the drag strip, though, that the limitations are seen and felt due to the continuous load placed on the fuel delivery sysytem. Bear in mind, though, that results can vary from bike to bike as a result of manufacturing tolerances and acceptable variations. While I have not done the math, the sizing of the present fuel rail and injectors is probably adequate; the big limitation is the pump and regulator. Upgrade to something that operates in the 50 psi range, both units, and it should solve the problem.

[surprenant]

SLAMMED I WONDER WHERE YOU GOT YOUR IDEAS??LOL....EXACT SAME PUMP,REGULATOR,FUEL PRESSURE THAT I WAS RUNNING LAST YEAR WHEN YOU WERE AT MY TRAILER LOLL..AIN'T THAT A COINCIDENCE HUH???  

[AssAbuser]

Steve do you have any pics of your set up?