2 bar map sensor Options

[jesterwr217]

ok im currently using check valves and im wondering what i have to do to put a 2 bar map sensor on just take out the map sensor and put the new one in and replace the check valves with regular vac hosing? and i have an safc 2 what do i need to change on it so my ecu isnt all screwed up? and if anyone has a link to somewhere i can buy one that would be great

[NuclearHappineS]

Here's where he's right

the voltage vs vacuum/boost scales he posts are correct, that's why we chose to switch to a 2 bar.

If setting 8 is truly a 2 bar
and setting 3 is truly a 1 bar

then at 5psi , the map sensor should output 3.3333 volts
The safc using 8 IN should read 3.333 volts as 5psi because it knows it's a 2 bar (From the setting #8)
The it applies your correction, for simplicity let's say it's 0%
Then it wants to translate 5psi into what a 1 bar would see at 5psi (because of setting #3)
So it will go to a lookup table and lookup 5psi on a 1 bar it should go ahead and output 5 volts
You should hit fuel cut

So his logic is incorrect... it just doesn't work like that...

As far as the FPR comment that's wrong too.... flat out wrong

There are 3 things that control fueling

1 is duty cycle
2 is the actual size of the injector
3 is the fuel pressure
4 (is the voltage at the injector but we can ignore this for now)

Duty cycle is how long the injector says open as a percent of maximum, this is a function mostly of your map sensor, and your rpm

1- example: 6000 rpm, 14psi is 90% and 3000rpm, 14psi is 45% these are figures programmed into the ecu.
2- the size of the injector for example stock is 200cc/min and upgraded is 400cc/min
3- the fuel pressure stock is 40psi differencial, with FMU is 100psi differencial
4- ignore

so at WOT with a 1 bar with 400cc injectors with no fmu @ 5psi
@ 3000 rpm you will get 45% * 400 * 1.0 = 180cc/min of fuel or 123 hp of fuel
@ 6000 rpm you will get 90% * 400 * 1.0 = 360cc/min of fuel or 246 hp of fuel

with a 2 bar, 400cc injectors, no fmu @ 5psi
@ 3000 rpm you will get 30% * 400 * 1.0 = 120cc/min of fuel or 82 hp of fuel
@ 6000 rpm you will get 60% * 400 * 1.0 = 240cc/min of fuel or 164 hp of fuel

with 1 bar + fmu + 400cc @ 5psi
@ 3000 rpm you will get 45% * 400 * 1.58 = 284cc/min of fuel or 195 hp of fuel
@ 6000 rpm you will get 90% * 400 * 1.58 = 568cc/min of fuel or 390 hp of fuel

with a 2 bar + FMU , @ 5psi , 400cc injectors
@ 3000 rpm you will get 30% * 400 * 1.58 = 189cc/min of fuel or 129 hp of fuel
@ 6000 rpm you will get 60% * 400 * 1.58 = 378cc/min of fuel or 259 hp of fuel

Let me redo the numbers for 14psi so you can get teh whole picture...

1bar , 400s, no fmu , 14psi
@ 3000 rpm you will get 45% * 400 * 1.0 = 180cc/min of fuel or 123 hp of fuel (same as 5psi)
@ 6000 rpm you will get 90% * 400 * 1.0 = 360cc/min of fuel or 246 hp of fuel (same as 5psi)

with a 2 bar, 400cc injectors, no fmu @ 14psi
@ 3000 rpm you will get 45% * 400 * 1.0 = 120cc/min of fuel or 123 hp of fuel
@ 6000 rpm you will get 90% * 400 * 1.0 = 240cc/min of fuel or 246 hp of fuel

with 1 bar + fmu + 400cc @ 5psi
@ 3000 rpm you will get 45% * 400 * 1.58 = 284cc/min of fuel or 195 hp of fuel
@ 6000 rpm you will get 90% * 400 * 1.58 = 568cc/min of fuel or 390 hp of fuel

with a 2 bar + FMU , @ 14psi , 400cc injectors
@ 3000 rpm you will get 45% * 400 * 1.58 = 284cc/min of fuel or 183 hp of fuel
@ 6000 rpm you will get 90% * 400 * 1.58 = 568cc/min of fuel or 368 hp of fuel << this is why i say not to use an FMU With 400s, no one on here is making that kind of power...

the problem with a 1 bar or simulating a 1 bar is that you have no boost based fueling ... you get the same fuel at 3psi as you do at 14psi...

that's what i'm objecting to...

if you redo all these numbers with 200cc/min (stock injectors) then divide all the hp figures by 2 and you will see why you need an FMU with stock injectors

for example 2 bar + fmu + 200cc injectors @ 14psi = 184hp @ 14psi which is sorta close to what you'd see from a car that has around 100hp stock... ...

This post has been edited by NuclearHappineS: Aug 10, 2007 - 3:54 PM