FAST questions - Craig?

[Not a 350]

I am new to the board and I just wanted to say that half of my questions have already been answered from reading through it. thanks for that!

On to the questions:

-With the FAST, should I be running a vacuum referenced FPR, or just run a constant pressure? I am using 29lb injectors (at 45psi) and flowing them at 58psi.

-Should I increase the injector size in the fast to reflect that I am flowing them at 13 more psi than they are rated, or just adjust the VE table to suit them?

-Any pointers on the spark tables? I have 16d at idle increasing linearly to 34d at 3000 and staying there the rest of the way up. This is at all MAP ranges. I have heard that at higher vacuums (cruising) you can run more timing although I can't find any info on it.

-Is there a quick and easy way to figure the proper amount of AE fuel in the various tables?

Sorry for the huge post, but I am new to all of this and still learning. Thank you for your time! I can send my tuneup file and datalogs if need be.

-Aaron

 

[Craig Smith]

Can't help you. I only help people with 350s.

Sorry, I couldn't resist... (I actually have a 388 SBC myself)

Anyways, you should run a vacuum line to the FPR. This is a must in speed/density mode. Fuel pressure will otherwise vary with engine vacuum/boost levels.

You should reflect that the injectors are flowing more than the 29 lb/hr they are rated at. Rule of thumb is that injector flow rate increases 1% for every 1 lb. increase over the standard 45 psi. So I would enter 32.8 for the injector flow rate.

You should be able to throw more timing at it in cruise areas and get better mileage out of it.

AE fuel is pretty much a trial and error process. Give it what it wants is about the best advice here.

Good luck with it!

 

[Not a 350]

Thanks Craig, I will leave the vacuum line on the FPR and adjust the injector size in the tuneup.

Do you have a sample file that I could pull the spark table from for reference? I need a place to start so I can look at trends in the table and adapt them to my own tune. Any help at this point would be gold to me!

Glad to hear you are a fellow "maxed out bore" stroker guy. I read you are planning on running 9's with your motor... can you fill me in any of the details of it?

Thanks again,
-Aaron

 

[bobc455]

Aaron-

For timing, remember how the guys with 350s did it - there was initial advance (which you have at 16 deg) plus mechanical advance (which you have set to 18 degrees to give you 34 deg total timing), plus the vacuum advance.

For vacuum advance, it basically behaves like this - zero degrees at idle, as soon as you crack the throttle open it will give you a lot of advance (since the port for vacuum advance is above the throttle blades), then as you get heavier on the throttle the vacuum advance backs off linearly to approximately zero (since there is virtually no vacuum at WOT).

If you play with that a bit in your tables, it will be a starting point - a lot of cars like as much as 50 degrees or more for total timing for regular highway driving (light load, relatively high RPMs).

My favorite way to nail the timing table is to have a friend drive under varying conditions and play with the timing table as they drive. I give it as much timing as I can until I see knock or the engine starts to run funny. (Note: I'm not ASE certified etc., so there may be other emmissions implications of running a lot of timing under some conditions, hopefully someone else will chime in if this is true).

One other suggestion while you're in the early stages of tuning - make sure that if your max RPM is 5000, the you don't have the tables set for 8000 - if so you will lose tuning resolution.

-Bob Cunningham
bobc@gnttype.org

 

[Not a 350]

Bob,

Thanks for clearing that up for me. I was curious as to how the vacuum advance worked, and now it all makes sense. I will try to emulate it in the tables and see how the car responds. The only problem is that it is snowing like crazy here so I may not be able to get to any tuning till March! I am dying with anxiety here!

-Aaron