Working on a 468 Chevy that has has F.A.S.T. XFI with a friend of mine.... Currently it is NA but will be turbo later. There is a base file that come with the XFI that is for a 450ci v8 with 42lb injectors... the engine I'm working on has 65lb injectors (for future turbo). My question is.... would scaling back the Base Fuel VE tables 35% be a good place to start.. Ive thought about it a lot and that seems to be the best first step to getting the VE tables close to the target A/F ratio....

any input would be great.... thanks in advance...

Scott 8)

 

I'd say pick a GCT file that is the injector size you have to start with regardless of the engine size.
However if the file is NA now and you want to switch to a 2 or 3 bar MAP later you will have to start from scratch anyway.

You might want to consider using a 2 or 3 bar MAP sensor now and picking a GCT file for a 2 or 3 bar and tune your NA motor for that.
Then you won't have to start from scratch for the future turbo upgrade.

 

currently it has a 2 bar MAP.... I have not seen/found any GCT files that are for 65lb injectors... everything but that size... If anyone knows of anyone let me know... I will be on the lookout for one in the mean time... Turbos are currently installed but have hat off for now... wasnt sure if we should break it in NA or reinstall intercooler pipes.

 

Just pick one that is close to your injector size, i can't remember all of them, but there should be one with 83's and one with 60's. Just change your fuel calc/firing order, ignition type, and make sure you have it set for your 2 bar map sensor and go from there.

 

I see at least three GCT files with 65# injectors. Some are NA and some are SC.
Download the 1.34 version of the software from the www.fuelairspark.com website and you can review them.
http://fuelairspark.com/Products/Information/Software.asp

If you are just starting it would be best to flash in the latest software first anyway.

 

Due to my car being in the body shop, I havent screwed with the fast in awhile, but shouldnt you be able to change the injector constant and it will compensate the inj. PW to suit?

 

After looking on my C-com, find the file thats closest to what you have, set the engine size, set MAP sensor to whatever bar you need to use (2 or 3) and set your injector flow to the correct size and start it up. Do not screw with the VE table to correct injector size when the XFI will do it for you.

 

Use the file 575sc65 file in the c-com. That will get you close. You may have to adjust the idle cell a little bit to get it where you need it, just look at he 02 readings. A nice feature in the xfi is when you are in closed loop it will show the 02 correction % in + or -. In steady state cruising use the L key and it will automatically adjust the VE table based on the correction percent in the cell that the car is running in! In WOT i have mine set up for the 02 to PULL 5-10% fuel in case of a wideband failure.

 

The only issue with doing it that way, is what if its not centered in the cell but actually in the middle?

Its a nice feature, but unless youre on a dyno and you can load the motor accurately, its kinda useless.

 

WOW !!!!
Great information guys. We have discovered another issue and have not been able to work on this . Hopefully by next weekend we will be able to work on it again. I think that we have gotten all of the gremlins fixed and can finally get this thing going and then start fine tuning soon. This is what happens when you give a dumb old hillbilly something high tech. ha ha
Thanks Guys,
Dusty

 

Well, its not really useless. Even if it's in between cells, it will take it to the cell with the most influence. Mind you this is steady state cruising, IE highway driving where you aren't going in and out of the throttle a lot and not a big jump in vacuum numbers. The big jump in throttle changes that take place, i have found it is best to use the AE fueling tables.

I didnt see this was going to be NA for a while, try the 555na65inj tune and enter your 2 bar map values as need be.

Anthony

 

It's not. We have just had the hat off while we were trying to get it to run. Don't know if you remember , but I PMed back and forth with you about this project a week or so ago. VWAUDIGUY is a friend of mine that has been helping me try to figure this thing out some.
Dusty

 

Ok cool, let us know how it turns out!

Anthony