fuel pressure question

[tjc]

So this is my thought....could you get the fuel pressure in the system high enough with for 6 pounds of boost? Say you buy an aftermarket pump and regulator such as: http://www.bellengineering.net/product_ ... ducts_id=4.

Stock Nytro fuel pressure: 46 PSI
Stock engine HP: 135
Goal HP: 180
Increase of 45 HP or 33% approximately

So Increase fuel pressure 33%: 46*1.33= 61 PSI needed

So could you hypothetically run a 4:1 or 5:1 rising rate regulator based on boost up to 6 PSI boost pressure and not need a piggy back or fuel controller?

I know this is primitive, but what if you limit it to 180 HP?

 

[mbarryracing]

Check out the Full Power Performance website for their stage1 Nytro kit description. You'll see that they use the stock fuel system without raising the fuel pressure, list the HP / boost max and also have dyno sheets. It's already been figured out for you.

 

[TBird]

Well, he add's fuel with an EFI controller, as everyone else with their "180" kit's

 

[mbarryracing]

tbird,
Thanks! I totally missed tjc mentioned WITHOUT a fuel controller. Yup, FPP uses a piggy back controller to add fuel to match the additional air.

In the old days when boosting was taboo, they used the Rising Rate Regulator method but it provided such a ball park AFR for sure that the transition was poor and it wouldn't be fun to ride on a sled unless you were just going to do dyno pulls with it.

 

[tjc]

I was curious about the response time and accuracy of the FPR only set up....I know it has been done before on cars I was curious if anyone tried it on a sled.

I feel like Yamaha spent a lot of money and time on the stock fuel system so why mess with it when idling/cruising.

Maybe put the IAT sensor in the charge box to help the stock computer adjust the fuel to the motor based on the temps.

Just thinking out loud.

 

[mbarryracing]

I figured that is where you were getting that idea from.
For some reason most turbo kits don't run the IAT in the intercooler / airbox, just hang off the harness. Guessing it's so things stay running rich and not lean out when the intake temps get warm under boost.
Cool that your gears are rolling in your head!

 

[tjc]

So just for my own interest I called BEGI today and spoke with Corky, he said the FMU is a viable option up to 6-7 psi but after that it is pointless. My guess was a little low he suggested 90 PSI with a walbro 255 inline with the stock pump. Kinda interesting stuff. The regulator is adjustable in 2 ways. You can adjust when the increase in pressure starts and you an adjust what the rate of rise is.

He said he has never put it on a motorcycle or snowmobile himself but people have done it.

 

[nate007]

Adding fuel simply using pressure is too risky in my opinion, and can be too hard on the injectors when increased too far.
It's always best to add a controller that adjusts the injector electronically and will do a far better job of measuring the fuel needed. While the stock injectors will run fine with higher pressure, it's always best to keep the pressure constant to the rails and let the injectors adjust the fuel with a longer pulse. Doesn't sound like you're going too extreme with your boost, and another regulator and pump may actually cost more and more of a pain to install than a plug and pay fuel tuner.
I would be personally a little worried about putting that much pressure to the stock injectors when the OEM pressure os only 46. More pressure will only wear the injectors more, and any discrepancies with the regulator will most likely foul plugs at idle, leaving you stranded somewhere. I do alot of tuning work on automotive aplications, and don't usually change fuel pressure on boosted cars unless the injector pulse width drains enough fuel from the rails to drop the fuel pressure. Even then, it usually only needs an additional 5-10 on a factory 58psi system and only for the high boost, wide open throttle situations where there is a chance of running lean. Several of the Kenne Bell Camaros I've built all use the stock pressure but jump to a 60lb injector instead of the 45's, and only boost pressure for long, hard dyno runs or at the top end of a drag strip when the rpms are calling for the largest quantity of fuel.
To do it using a straight percentage or ratio to power increase would be technically adding way too much, and stressing the stock injectors to the point of failure.
I would say if you get to where your AFR's won't stay where they should be at no more than 55-58psi, I would go to a larger injector and start back at the factory pressure. Larger lines and fuel rails will allow you to flow more fuel as well and not need as much pressure.