fuel pressure and NA tunning questions

[mellow65]

calling all the motor gods out for some questions

 

Ok here is what i got. I have 99 RS motor in my 90 legacy running the stock ej22 ecu. I have a cone style filter and header with a 2.25 outlet and a 2.5 all the way back. I also just installed a set of 2000 grind delta cams.

 

First thing I want to do now that everything is back together is check to make sure I'm not running to lean with all the new air coming in and going out. I have a buddy of mine with a wideband that we are going to throw on it here soon but I am looking for some numbers to work with.

 

Where should I be checking the ratio, ie WOT, idle, cruising at 2500 or what ever? And what kind of fuel ratio should a NA car be running at those points?

 

So assuming my ratio is a little lean I have plans of bumping up my fuel pressure to bring it up to par. I know the stock 2.5rs FPR runs about 42.5 in what kind of increments should I step up in? ie 1psi, 5psi, 10psi.

 

thanks

[Legacy777]

The chances of you running lean on an n/a motor is pretty slim. You will more then likely still run richer then ideal. Adding a cone filter, and changing cams may increase air flow, but the MAF sensor should calculate that, and add the appropriate fuel.

 

It has been found that adding a cone filter can play havoc with the MAF sensor, and cause it to give false readings. So, you may want to try swapping back to the stock air box, depending on how the car seems to run.

[mellow65]

The chances of you running lean on an n/a motor is pretty slim. You will more then likely still run richer then ideal. Adding a cone filter, and changing cams may increase air flow, but the MAF sensor should calculate that, and add the appropriate fuel.

 

It has been found that adding a cone filter can play havoc with the MAF sensor, and cause it to give false readings. So, you may want to try swapping back to the stock air box, depending on how the car seems to run.

 

well that's always good to know, i was thinking of going back to the stock air box it was kind of iffy how i had to mount it.

 

that and that damn bling bling tube drives me nuts.

 

my only thought on the whole thing was the ecu was only meant to see a 2.2 and now it's pulling 2.5 with cams. i know it's not crazy different but it made me think about just checking if it was running lean at all. but i guess you are right if it "sees" the air come in it should know how much fuel to put in.

 

i am replacing the fuel pump with a high flow one just to be on the safe side. not only does it give a more flow but it replaces a 18 year old pump.

[Legacy777]

If your ECU was MAP based, then yes you would have a problem. However your ECU is MAF based, and accurately measures the air entering the engine, and will adjust to modifications.