VAFPR and dialing in high pressure spring I read lots of mixed opinions on whether or not a VAFPR is a worthwhile setup on a TBI using a 7427 PCM. I currently have a 27 PSI spring in my regulator, hoping to fuel a SBC that I estimate should make about 400 FWHP. So, should I be using a VAFPR to lower pressure at idle? Or can this be tuned around without using a VAFPR? |
Re: VAFPR and dialing in high pressure spring After about 18 psi you want to go to a VAFPR. The problem with high pressure @ idle is overfueling. |
Re: VAFPR and dialing in high pressure spring
Originally Posted by morgsie
(Post 6272713)
After about 18 psi you want to go to a VAFPR. The problem with high pressure @ idle is overfueling. |
Re: VAFPR and dialing in high pressure spring Fast, so you were running 30 psi WITHOUT a VAFPR?? Will you please elaborate on what parameters you had to tweak to get idle not to be crazy rich? |
Re: VAFPR and dialing in high pressure spring
Originally Posted by Fast355
(Post 6272730)
I have also taken a lesson from 2.8s and 4.3s and 454s and run completely asynch calibrations to stretch the injectors further at both idle and WOT. |
Re: VAFPR and dialing in high pressure spring
Originally Posted by Cdeez
(Post 6272734)
Fast, so you were running 30 psi WITHOUT a VAFPR?? Will you please elaborate on what parameters you had to tweak to get idle not to be crazy rich? |
Re: VAFPR and dialing in high pressure spring
Originally Posted by DynoDave43
(Post 6272760)
And can you explain this as well? :) |
Re: VAFPR and dialing in high pressure spring
Originally Posted by Fast355
(Post 6273365)
I ran 30 psi without a VAFPR. Pulse width was about 1.1-1.2 msec at idle on my setup. Biggest change I made was use the injector correction data from a 1995 454 that used the high pressure fuel system to start with. Even though those 454s used the smaller high pressure 4.3 injectors it is still a closer starting point than the low pressure stuff.
Originally Posted by Fast355
(Post 6273370)
The 2.8/4.3 and later 454s often have asynchronous injection only. Asynch fires the injectors at a fixed rate rather than in synch with the distributor reference pulses. This gives you more control over them at both low pulsewidths and allows you to run a longer pulsewidth at higher PRM. Asynch fires at a fixed 80 hz or once every 12.5 msec. |
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