Fuel Pressure Regulators and you...

[TomsSVX]

Well I have my walboro 255 installed and the car ran excellent. I then later installed my adjustable FPR and the car proceeded to run great. Once the temps rose again to the mid 60's to mid 70's the car began to run a little off and stall quite frequently. Tomorrow I am going to go outside and turn the FPR back a little and set it back toward stock pressure of 36psi. Right now I am running about 42psi. The tips are really black(worse than they used to be). I get the feeling I am running too rich and choking out the motor in warm humid weather but it is running great in cold dry weather. I figured everyone should know this so I would share so anyone looking to go with a higher pressure FPR or an adjustable could use this info for themselves

Tom

[Chiketkd]

From the graph Mychailo posted when he did some testing with his wideband using an Impreza fpr (raises fp to 43psi), our cars will run extremely rich in open loop at that fuel pressure.



I've also noticed a steady blackening of my exhaust tips after installing the Impreza fpr in my car...

-Chike

[TomsSVX]

Yes, but I think the Walboro is pushing it a little too far for an N/A engine

Tom

[Chiketkd]

Originally Posted by TomsSVX

Yes, but I think the Walboro is pushing it a little too far for an N/A engine

Tom

Good point. However, I'm not sure what effect the Walboro is having b/c from a diagram Mychailo posted, it shouldn't affect fuel pressure.

[TomsSVX]

I did not think so either but my car is running like crap last night and it did not feel right earlier. I am gonna back off on the pressure and see what happens

Tom

[mbtoloczko]

Tom, I guess you have a fuel pressure gauge mounted on there somewhere? Is this with the Stage 2v4 hardware? If so, didn't LAN say it was tuned for 43 psi?

[mbtoloczko]

Originally Posted by TomsSVX

.... Right now I am running about 42psi. The tips are really black(worse than they used to be). I get the feeling I am running too rich and choking out the motor in warm humid weather but it is running great in cold dry weather....
Tom

The exhaust tips on my car also have a fair bit of black soot also. Runs well though in any weather though. I do have some stalling problems, but I have been attributing it more to the light flywheel with my 5MT and the fact that the ECU wasn't intended for a manual tranny. Does your car stall when its idling, or does it stall when decelerating and pushing in the clutch?

[cdigerlando]

Originally Posted by TomsSVX

Well I have my walboro 255 installed and the car ran excellent. I then later installed my adjustable FPR and the car proceeded to run great. Once the temps rose again to the mid 60's to mid 70's the car began to run a little off and stall quite frequently. Tomorrow I am going to go outside and turn the FPR back a little and set it back toward stock pressure of 36psi. Right now I am running about 42psi. The tips are really black(worse than they used to be). I get the feeling I am running too rich and choking out the motor in warm humid weather but it is running great in cold dry weather. I figured everyone should know this so I would share so anyone looking to go with a higher pressure FPR or an adjustable could use this info for themselves

Tom

You are going to need to tune. If you can get someone to tune the ECU for you or go with some stand alone engine management this would work. Then you could run the pressure up to where the Walbro is most efficiently designed. Any idea what pressure that is? Got a pump curve?

[TomsSVX]

no pump curve. Right now the car is still 100% N/A and these are just upgrades in preparation for the twins this winter. I was just mentioning that the upped fuel pressure is not helping, infact hurting the performance of a naturally asperated 3.3l on a stocker ecu

Tom

[Myxalplyx]

Bringing this ancient thread back up. Noticed that stock pressure is 36psi and people have been bumping them up to 43psi.

Let us say that your air fuel ratio is 13.6:1 and you want to bring it down to 12.8:1 for WOT horsepower purposes (Just because in your head for some reason you think it will make more power in the 12.5:1 to 13.0:1 range being naturally aspirated). Just a guess but how much of a pressure increase will you need to make this happen from the stock fuel pressure of 36psi? I am curious as to if there is a formula for this (Ex: +2psi fuel pressure increase = -.4:1 air/fuel ratio drop or richer fuel). If not, then just will have to do it by trial and error. I wish I could do a cool graph like Chike put up. Thanks for any input!

Also, is there a how-to for installation of a fuel pressure regulator here somewhere? I have a fpr regulator and gauge from my Subaru RX turbo in my garage. May as well put them to use.

BTW: Browsing the internet I ran into an interesting before and after air/fuel ratio tuning article on a Honda.
http://www.turbomagazine.com/tech/02...ing/index.html
I am not saying we can expect similar gains but it does show what proper air/fuel ratio tuning is capable of.
Wish an SAFC could be used on an SVX.

[cdigerlando]

Originally Posted by Myxalplyx

Bringing this ancient thread back up. Noticed that stock pressure is 36psi and people have been bumping them up to 43psi.

Let us say that your air fuel ratio is 13.6:1 and you want to bring it down to 12.8:1 for WOT horsepower purposes (Just because in your head for some reason you think it will make more power in the 12.5:1 to 13.0:1 range being naturally aspirated). Just a guess but how much of a pressure increase will you need to make this happen from the stock fuel pressure of 36psi? I am curious as to if there is a formula for this (Ex: +2psi fuel pressure increase = -.4:1 air/fuel ratio drop or richer fuel). If not, then just will have to do it by trial and error. I wish I could do a cool graph like Chike put up. Thanks for any input!

Also, is there a how-to for installation of a fuel pressure regulator here somewhere? I have a fpr regulator and gauge from my Subaru RX turbo in my garage. May as well put them to use.

BTW: Browsing the internet I ran into an interesting before and after air/fuel ratio tuning article on a Honda.
http://www.turbomagazine.com/tech/02...ing/index.html
I am not saying we can expect similar gains but it does show what proper air/fuel ratio tuning is capable of.
Wish an SAFC could be used on an SVX.

If you start pushing your fuel pressure up, you are going to run very rich at idle, unless you tune. Bottom line is you need to be able to tune your injectors to do any useful and safe air/fuel ratio changes. I've had to run stock fuel pressure on my new setup with the nismo injectors and Tec 2. Anything less is not tunable (the injectors can't flow less). The FPR increases the pressure on the fuel rail 1:1 with an increase in manifold pressure so if I were running 20 psi of boost the pressure would rise from 35 psi to 55 psi. But this is all tunable.

[Myxalplyx]

Originally Posted by cdigerlando

If you start pushing your fuel pressure up, you are going to run very rich at idle, unless you tune. Bottom line is you need to be able to tune your injectors to do any useful and safe air/fuel ratio changes.

I plan on using what I have lying around. I have a Jumptronix digital air/fuel ratio meter on my FWD XT6 over my sisters house. That was a very reliable tool to use on an N/A engine and it worked well on 'tuning' the XT6 when Gary Gross installed Delta cams in it. What I did was raised and lowered the fuel pressure to get a flat line on 13.0:1 at WOT. Once this was established, I was gold.

However, I plan on doing the same thing with the SVX but need to use the SAFC to trim fuel down during neutral and light throttle conditions. This worked well on my Outback Sport so I figured why not try it on this. There are two important setup info about the SAFC that I need to find out. I may need to post this in an SAFC thread.

What is the Sensor Calc and Sensor Number settings to use the SAFC on an SVX? Does anyone know? I only think I need to adjust the fuel. I will know after tomorrow.