420A Boosted 420a FPR

[Lilsquidz]

Can someone give me the formula/ math/ exact number in order to properly tune my FPR for my turbo. I’ve seen people say 45 psi but that’s for stock 420a, and if I am supposed to be running 45 psi can someone confirm that ?

Putting on a bigger turbo then the one shown in picture this afternoon

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[97egl]

The only real reason I could see to bump the fuel pressure up from stock (or where it is currently set) would be if you are running out of fuel on the injectors you have. And that is more-so a temporary band-aid to the problem. The better way to go would be to get bigger injectors if you are running out of fuel.

Unless you are trying to tune in the car with no engine management system and just adding fuel pressure? If thats how the car is set up I would NOT recommend putting an even larger turbo on it.

 

[99dsmer4g63]

Bro is that black duct tape over the intercooler pipe where the blow off valve is to be at?

I see you are on a factory ECU still. You have an FMU or something on this car?
-Daniel

 

[jesse12345]

I ran a adjustable FMU made by this company called Spa. It worked well for my setup but I used a fuel pressure gauge and wideband along with it. It raised fuel pressure as I got into boost. I wouldn't run anything big with the FMU, because your really tuning with just fuel pressure.

 

[Lilsquidz]

Bro is that black duct tape over the intercooler pipe where the blow off valve is to be at?

It flew off one night ima get a new one old engine pic it’s not at my house

The only real reason I could see to bump the fuel pressure up from stock (or where it is currently set) would be if you are running out of fuel on the injectors you have. And that is more-so a temporary band-aid to the problem. The better way to go would be to get bigger injectors if you are running out of fuel.

Unless you are trying to tune in the car with no engine management system and just adding fuel pressure?

If thats how the car is set up I would NOT recommend putting an even larger turbo on i

So from stock psi (which is 45?) which one would make it run a little richer? 50 or 40, I want it to run richer so it’s safe

 

[Canadian_CD9A]

So from stock psi (which is 45?) which one would make it run a little richer? 50 or 40, I want it to run richer so it’s safe

The ECU compensates for that with fuel trims, it won’t do anything useful. You set your pressure gain to achieve that richness in boost, but really there’s no such thing as safety with the FMU. If you enter positive boost without going wide open throttle, you remain in closed loop and the ECU will always try to achieve 14.7:1 AFR, which is dangerous and could cause detonation. FMUs only operate ‘properly’ at WOT. They are ancient and obsolete, I strongly recommend against using it.

 

[Lilsquidz]

The ECU compensates for that with fuel trims, it won’t do anything useful. You set your pressure gain to achieve that richness in boost, but really there’s no such thing as safety with the FMU.

FMUs only operate ‘properly’ at WOT. They are ancient and obsolete, I strongly recommend against using it.

Okay so how do I make it safe with just a FPR and no FMU

Bro is that black duct tape over the intercooler pipe where the blow off valve is to be at?

I see you are on a factory ECU still. You have an FMU or something on this car?
-Daniel

Yes duct tape on the BOV (I noticed when I did the it actually made the car run better) but no i didn’t do it on purpose, it flew off one night with all the connectors. yes factory ECU, and stand alone FPR and FMU together, but what’s the correct psi for it to be safe 43?

 

[Mello]

Can someone give me the formula/ math/ exact number in order to properly tune my FPR

FPR are not tuned. You adjust them for a specific pressure & they keep this pressure constant between the the intake manifold & fuel line so the difference is always the same (i.e.: the pressure difference across the fuel injector in & out needs to remain the same). You adjust tuning through the ECU by making changes to the appropriate ECU maps.

 

[Lilsquidz]

The ECU compensates for that with fuel trims, it won’t do anything useful. You set your pressure gain to achieve that richness in boost, but really there’s no such thing as safety with the FMU. If you enter positive boost without going wide open throttle, you remain in closed loop and the ECU will always try to achieve 14.7:1 AFR, which is dangerous and could cause detonation. FMUs only operate ‘properly’ at WOT. They are ancient and obsolete, I strongly recommend against using it.

I found out from searching up the brand that’s it’s a stand alone fpr fmu together 1 psi for 1 psi of boost, is that safe for the car?

 

[Dericsh]

I found out from searching up the brand that’s it’s a stand alone fpr fmu together 1 psi for 1 psi of boost, is that safe for the car?

You need to install a wideband instead of a bigger turbo so you can see what’s going on.

 

[1990TSIAWDTALON]

On turbocharged applications, the fuel pressure is a 1 to 1 rising regulator and that is the correct amount of fuel per pound of boost as long as the car is not running lean all the time, in which case you would bump up the pressure until you have close to stoich at idle @Dericsh is correct that you really really need a Wideband O2 sensor to see what the motor is ingesting as its mix, with 14.7 being stoich. That sensor is what you need to see if the tune is working right or not.

 

[steve]

Also on a turbo car the ECU measures the air flowing and know what to do when boost happens. Many NA ECUs don't like that at all and need various tricks to keep them from freeking out.

So there is more to it than just raising the fuel pressure 1:1 with boost. That's just to keep the injectors output linear otherwise as the pressure in the manifold increased the injectors would start to reduce their output to a dribble.