Banshee Ben

iTrader: (4)

On my bike I run a 6:1 boost referenced regulator. So at idle/sub boost I run 60 psi and at 1 psi boost it goes to 66 psi. Don't I need the same thing on my current build? I've read on here that some just set it to a flat 60. How would that tune under boost?

EPP

iTrader: (22)

On a stock bottom end you don't need a boost referenced regulator, or for that matter up through 650 plus rwhp or so. A lot of guys get by at 650 or so rwhp with just two Walbro fuel pumps tied together in the fuel tank, with the stock fuel system. Bob

MIGHTYMOUSE

iTrader: (59)

i don't think it is ever a 'must'

your bike has more of an FMU which thows fuel at it manually vs in the tune up. it 'works' but you are surely not getting the most out of it.

a referenced regulator keeps the pressure delta across the injector constant, which FOR ME makes sense and allows me to pull pressure away in vacuum which helps my big injectors putt around town without getting into 0-1% duty territory

slow

iTrader: (7)

Ditto, also, if you do not run a boost refereneced regulator (1:1) your injectors get smaller under boost, so you have to lie to your pcm somewhere, either commanding a richer airfuel ratio, or telling the pcm more air is entering the motor, than what is actually occuring.

Ryan

kp

iTrader: (34)

I run 95lb injectors @ 65psi static and can idle cruise @ 14:1 a/f all day. If you look at your a/f at low pulsewidths going from 40 to 60psi really doesnt change things a whole bunch, but it is easier on the pumps to run less pressure if you are street driving I guess..

But ever since I put a nice fuel system in the car I dont boost reference, havent for a couple years..

ALLBOTTLE

iTrader: (13)

The Boost reference also come into play with equalizing the pressure between manifold and rail pressure.

At vacuum or 0psi you get the full Rail pressure 45/55/65psi etc. at 20 psi of boost you now have 20 psi of positive pressure in the manifold causing the net fuel pressure to be 20psi below rail pressure. With a Boost referenced regulator it will raise the pressure equally to get the same net fuel pressure.

Websy21

iTrader: (34)

From what I've read they are worth it when running any decent ammount of boost and making allot of power. I've heard about 650rwhp too, it me be a bit harder on the pump but cheap insurance for the motor imo.

kp

iTrader: (34)

Anytime you use rwhp for anything to do with a fuel system you are going down the wrong path.

Its not that complicated, if you run 43psi base pressure and are running 20psi of boost you should have 63psi of fuel pressure to make up for it.

Thats all fine and dandy but a lot of people start at 60psi base and try to get 80+psi and in most cases that just doesnt happen very consistently when things start heating up. Instead, since I can still idle just fine with 95lb injectors @ 65psi I choose the KISS method. If I do the rpm vs DC calcs I'm right where I should be. Maybe with 160lb that wont work but I'll worry about that when I get there.

Naturally its best to just run some bigger injectors but with a stock hi-z PCM you are a bit limited..

Zombie

iTrader: (2)

I'm not running a referenced regulater either. My setup is just like KP's. 65psi static all the time with 95lb/hr injectors. Works great, but I'm using a mega squirt II to control them.

Websy21

iTrader: (34)

Hmmm news to me but thats great if its working for you guys than its definetly good enough for me besides that I've already bought one.

kp

iTrader: (34)

Well my regulator has a port for it and I have hooked it up several different ways. Pre and post throttle blade, but I saw no advantage of doing it that way and top end fueling was a little inconsistant for my tastes. You dont have to hook the port up. According to some the BS3 internal fuel map is more set up for boost referencing but it works fine for me static. I'm not implying my way is the only or correct way but it works for me and I havent blowed anything up yet..

It really depends on your fuel system overall, if you start getting over 750-800 uncorrected hp you have no choice with hi-z injectors other than crank the pressure up and not many streetable fuel systems are going to last long at a constant 80psi. Some injectors dont work well at high fuel pressure either so you have to be careful at high DC and high pressure.

Photochop

iTrader: (74)

Well this is good news for me as I'm not going 'full tilt' with my build until I can afford to do a better converter or a th400 swap. I'm shooting for around 500-550 rwhp with around 7-8 lbs of boost as a baseline pump gas on the car when I get it running. So far I've got 2 walbro 255 intank pumps, racetronix harness, stock lines, speed inc rails, and motron 60 lb injectors. So with the base power I'm shooting for a boost referenced regulator and replumbed fuel system changing the evap over to a return line isn't necessary? I'm fuzzy on static fuel pressure if I'm not using monster injectors. If my base pressure is 43 then 51 is what I want the static to be at?

Banshee Ben

iTrader: (4)

Wow lots of info.

To be more precise I have an external accell pump, 60cc inj, fuel rail, and aiming for 750hp. 12-15 psi boost.

So is a 1:1 better so I can run 40psi at idle and 55psi at full boost?

Or still just set it at 50-60 and call it good.

Recommended regulator?

How does the computer know to put more fuel in at 5 psi boost at 3k rpm vs 3k rpm and 2 psi boost? The map? And if that is the case wont a rising rate reg mess up the equation as there are no sensors for that?

ALLBOTTLE

iTrader: (13)

When ever possilbe you wan to run the lowest Base fuel pressure possilbe, this will help keep the fuel cool and the pump happy. You may wan to go with larger injectors.

gametech

iTrader: (1)

Most bike computers have such limited (or no) tuning ability, that a rising rate fmu is the only way to throw more fuel at it with any sort of control. The car PCM's have a lot more capability to tune properly. You CAN tune around a constant fuel pressure, but it becomes more and more of a problem at higher boost levels. An extreme example would be a base fuel pressure of 65psi, but a boost pressure of 40psi. That only leaves a fuel pressure delta of 25psi to feed a monster motor. The less boost you run, the less this would be an issue.

slow

iTrader: (7)

The airflow model will be different, regardless if you run a 2 bar map sensor, or if you run a MAF sensor, the airflow will be different.

the pcm only responds to vacuum, in regards to changing injector flow rate (injectors get bigger under vacuum)

Ryan

MIGHTYMOUSE

iTrader: (59)

my all time favorite regulator and the one i use is the kirban race regulator kpp5071, matter of fact i have a brand new one here on my desk to put in my truck

your IFR table becomes a constant number (flat) across the table as opposed to a slant

frcefed98

iTrader: (16)

no boost reference here either.


Twin intank walbro pumps, high flow rails, 60lb injectors, -8an feed, -6an return and a CAS fuel pressure regulator.
J

Websy21

iTrader: (34)

Hmmm, jsut curious if you don't mind me asking what hp numbers you are making? Flwheel estimate even? Judging by your sig I am sure its no slouch, just curious on the boost and hp numbers.

frcefed98

iTrader: (16)

15psi is what I have it at right now. No dyno #'s on this combo yet, but hope to have some at the end of the month, we have a shop here locally that has a load dyno now

Track times will hopefully be posted after the 15th of this month (opening day)

I'm pretty stoked to see what she does with a tranny that can take the turbo abuse, and launches off the T brake should help a bit too. Never got a clean turbo pass last year due to tranny issues and a melted cat converter that was keeping my boost to 9psi LOL. All the drama is fixed, no cat to worry about, TH400 with a nice converter built for the turbo, and a Moser 9 that'll take a T brake launch without blinking an eye.

BUT its the same fuel system that i've had on the car since my procharger days. Best time then was 11.10@124.74 with a DA in the upper 7000's....being up a mile high sucks *****. Car weighs in at 3600.

Sorry I couldn't be of more help.

For pics of the set up go to www.fquick.com/frcefed98

J