Fuel Pressure Regulators and you...
 

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

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.

http://www.subaru-svx.net/photos/fil...czko/26185.gif

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

-Chike

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.

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

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?

no stock ecu since I cannot get a hold of a z32 MAF.

Tom

What kind of adjustable fpr are you using Tom?

Hmm... I assume the stalling occured only in closed loop operation? Might be an O2 sensor (did your ECU throw any codes?) or even some bad gas if your 5spd has been sitting for a while.

You could always disconnect your battery for a 1/2 hour and then re-connect and see if the problem returns.

-Chike

Bsfc...
 

While we're on the topic of fuel, I was wondering if anyone had a good estimate of what the BSFC (Brake Specific Fuel Consumption) is for the stock n/a EG33?

I have long been using 0.50 in my equations, but when doing some research on an LT1 vette forum, most owners there use a value of 0.45 for an n/a LT1:

http://lt1edit.com/pipermail/lt1edit...22/030527.html

Reason I ask, is b/c BSFC values of 0.45 & 0.50 will give entirely different end values when calculating the amount of horsepower my stock injectors can support with a fuel pressure of 43psi (from Impreza fpr) and a max duty cycle of 80%:

With a BSFC of 0.50 - 254.4hp can be supported
With a BSFC of 0.45 - 282.6hp can be supported

-Chike

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?

Chike,
If you take the advertised 230 hp @ crank and the injectors' flow rate at the stock pressure you'll back out a BSFC of .45 at a duty cycle of 75%
-Bill

Thanks Bill.

I suspected that the BSFC for an n/a EG33 was actually around the 0.45 range due to the high VE of our engine in the upper rpms...

-Chike

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?

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