Fuel pressure with FAST

[Alaskabuick]

This may be are dumb question. But do the same basic guide lines apply for Fuel Pressure running fast? 42-43 pounds?

Additionally, where should I have the 2nd pump come on running a quad air double pumper?

Just starting to tune and new to the system. I seem to be always be running rich. Should I just turn the fuel pressure down and see what happens before I start tunning with the fast fuel tables? Would this not be the simplest way to start getting on track?

Dennis

 

[JDEstill]

Not an expert, but for what it's worth...

The FAST uses the injector size as part of the pulsewidth calculation. For a given set of conditions it will figure up a lower pw for 72's than it will for 60's so that the same amount of fuel is injected either way. The best thing to do is to give the FAST the most accurate information you can. So if you have 72's for example, you want to tell the FAST you have 72's, and you want to make them flow like 72's. That means setting the fuel pressure at 43.5 psi or so, which is where they are rated at 72 lb/hr. You can run a different fuel pressure if you want, but then you ought to tell the FAST what you are doing. Say you wanted to run them at 35 psi. That makes the injectors act smaller, not like a 72 anymore but more like a 65 I think, so to get the right fueling you'd want to tell the FAST that you now have a 65 lb/hr injector.

Double pumper, you can essentially turn it on at any point where it doesn't give you a rich spike. If you turn it too early the extra pump capacity is too much for the regulator to handle, the fuel pressure jumps up, and you go rich. A little experimentation ought to find that point. I would guess that a lot of cars don't need to turn it on until they get to 15+ psi boost. If you've got a nice big return line you can turn it on at a much lower pressure, or even run both pumps full time. The problem tends to be not a big enough return line rather than the regulator not being able to handle the flow.

As for running rich as you start your tuning, I wouldn't mess with the fuel pressure as a starting point. I'd set it at 43 psi like normal. Get it good and warmed up, and start adjusting the VE table so the correction goes to zero. You want the actual measured a/f ratios to equal the a/f ratios commanded in the a/f ratio table. Once you get that happening, and you think it is rich or lean, you then adjust the a/f ratio table to make it behave like you want. But the first step is to get the VE table tuned.

Hope that helps

John

 

[HighPSI]

Where is your IAT sensor located?

 

[Alaskabuick]

Iat

Where is your IAT sensor located?

Cal,

it is located in the up pipe about 9" ahead of the TB.

Thanks,

Dennis

 

[HighPSI]

The reason I asked was because you are in Alaska where it can get quite cold. The FAST uses the IAT sensor to calculate how much fuel the engine needs.
Make sure that there isn't any additional fueling being applied (COOLANT, battery, afterstart,etc...)
Make sure your MAP is reading correctly (100KPA - key on , engine off)
Is the car running rich at idle, WOT, cruising...?
Are you running a 16 volt battery?
I don't know your combination so I am guessing on quite a few things. Probably best to call whoever you bought your FAST from.

 

[Reggie West]

The trick with a double pumper set up is to get the second pump to come on when it is needed.

I would set the second pump to come on at 10 psi.

Then watch the correction values on your fuel table. The wide band will pull a lot of fuel out of the map to get to the desired A/F ratio you put in the table. It will only pull out a max of 25% if that is what you have the wide band set up for. You may want to check to see what the settings are on it.

Once you turn on the second pump you have effectively doubled the volume of fuel at the injectors and it is up to the computer to compensate for it.

With a GT67 wheel you will need both pumps and the turbo will flow plenty of air.

You can trim up the fuel map so it is not running rich. Just data log the runs and you will see where the second pump kicks in. Run a data log with PSI and O2 correction vs rpm and you will have the info you need.

 

[Alaskabuick]

double pumper

thanks for the input guys.

I am just starting out on this FAST system and have just learned how to log and read the info with the 3d. Cal you helped me with this on another post a while back.

I have not really had a chance to log any real good pulls. It spins soo bad on the street, the best I can do is a steady 2nd gear roll and then lay into it and log WOT thru 2nd and then 3rd. So Im getting that info.

The correction tables are set at 20%. The Double pumper is a quad air and I think it is set at factory setting of 10 lbs? Is that right? The hobs switch looks as it has no adjustment? Is their a place to change where the 2nd pump comes on?

This car is new to me and I did not do the install on the QA. Although I have had it ripped all the way down to the short block this past winter to do the Heads. You guys may remember a post of mine last fall "Car breaking up at 5300", It ended up being that the guy that built the motor put the wrong valve springs in for a roller cam. Problem solved with a little help from Dan Strezo installing new springs.

Cal the car runs rich at idle, Ill check on the map readings.

One question I have is how to lean it out to be more responsive when you nail it. Seems a little laggy? Have a 911 3600 stall from PTs. To do this do I simply log a run when I hammer it and then go back and adjust the VE table at that point? Do we adjust even where we were not at full throttle but in transition?

Im trying guys, slowly figuring it out. The good new is the car is sick fast as it is, but I know she has alot more on tap.

Dennis

 

[Reggie West]

Send me the data logs and I can look at it for you.

The closest I have for a program is with 83# injectors but you can look at it for comparison.

When you data log it set it up to record for 30 seconds that way you can drive it without worrying about the length of time it will record.

Most of the double pumpers kick in at 10 psi. You can adjust it but 10 is fine.


Yes you can lean it out to make the motor more responsive. Be careful doing it, you do not want to lean out the motor under boost. Example, you can run A/F ratio of 13:1 at lower rpms but once you see boost start increasing the A/F ratio to 11.5 .

I will send you a program to look at.

Remember too that when you are torque braking the motor off of the line it is different than nailing it from a dead stop. You can work on that on the street but be very careful where you do it. You know what I mean.

You want to lean it out to get the turbo spooling and once that happen the monster awakens

thanks for the input guys.

I am just starting out on this FAST system and have just learned how to log and read the info with the 3d. Cal you helped me with this on another post a while back.

I have not really had a chance to log any real good pulls. It spins soo bad on the street, the best I can do is a steady 2nd gear roll and then lay into it and log WOT thru 2nd and then 3rd. So Im getting that info.

The correction tables are set at 20%. The Double pumper is a quad air and I think it is set at factory setting of 10 lbs? Is that right? The hobs switch looks as it has no adjustment? Is their a place to change where the 2nd pump comes on?

This car is new to me and I did not do the install on the QA. Although I have had it ripped all the way down to the short block this past winter to do the Heads. You guys may remember a post of mine last fall "Car breaking up at 5300", It ended up being that the guy that built the motor put the wrong valve springs in for a roller cam. Problem solved with a little help from Dan Strezo installing new springs.

Cal the car runs rich at idle, Ill check on the map readings.

One question I have is how to lean it out to be more responsive when you nail it. Seems a little laggy? Have a 911 3600 stall from PTs. To do this do I simply log a run when I hammer it and then go back and adjust the VE table at that point? Do we adjust even where we were not at full throttle but in transition?

Im trying guys, slowly figuring it out. The good new is the car is sick fast as it is, but I know she has alot more on tap.

Dennis