I currently have a 12:1 in my vortech fmu/fpr, and obviously thats too rich.. but how do i decide if i need a 10, 8 or 6:1 ? because i dont feel like spending 120$ to try all 3...

sorry if this is a stupid question, and thanks for any help !

 

You don't unless you dyno.

http://www.vortechsuperchargers.com/...ries/fuel.html $44.60
P/N 6Z270-010 Recalibration Kit, Includes 4:1, 6:1, 8:1, 10:1, and 12:1


I believe the 3:1 is in the kit also (they didn't list).

 

yaay, boy can i say i feel stupid.. ive been there a million times to check prices of each disc, and was about to order a 10:1 and 8:1 haha, which would be more expensive then the whole kit.. thanks !

 

Like Kevin said, you will HAVE to put it on a dyno with wideband O2 sensor readings. The amount of fuel you need has a direct relationship to your injector duty cycle (assume 100% unless you have AFC or ECU mods), BSFC, crank Horsepower.

Take a look at this site. It has a very good Fuel Injector Worksheet.
Find out your crankHP.
Assume 0.525 BSFC (no less)
Max duty cycle 80-100%
Fuel pressure - ??? Play with some numbers here ensuring that the Static flow injector stays around 240cc +/- 5cc/min.

This will tell you how much fuel pressure you really need. The vortech FMU disk, say 12:1 will give you 12 psi increase in fuel presure for every Pound of boost it "reads" via the vaccumm line.
If you are pushing 5 psi boost, your fuel pressure will be:
(static pressure) + 5x(disk ratio) = 43.5 + (5x12) = 103.5psi fuel pressure at fuel rail. Some say that you should divide the static pressure by 2, but I have yet to confirm that.

Here are Vortech S-FMU Instructions . This should give you a good understanding of how to calibrate/tune your fuel using Vortech FMU.

There is also a calculator that calculates the size of your FMU disk but I would double check before popping a disk in there & going full boost.
http://www.turbosaturns.com/resources/boost.html

Good Luck & please share your findings.

 

i ordered it.. I know a/f guage isnt very accurate , but is it enough to know if im using the right disc .. ?

 

By the time you read "lean" on the Autometer a/f gauge... motor.

Start big, then go small.... 12:1, 10:1, then 8:1. I wouldn't run smaller than 8:1 unless you are on the dyno since we don't have enough data from the select few turbo owners.

I'm going to run rich until I get on the dyno.

 

another stupid question.. where do i want the guage to read under WOT idealy ?

 

A little on the rich side.

 

12.5:1 A/F right?

 

I don't recommend going leaner than 12.5:1. During the SC dyno, I found that 11.X:1 yielded more hp than a leaner 12.X:1 so