I'm thinkin about taking my car to the dyno to get tuned soon, but I had a question first. What's the advantage of raising your fuel pressure versus just richening your fuel curve? Thanks in advance.

 

First off, the FPR can either richen your fuel curve or lean it out ACROSS the RPMS band. Allow me to explain. If you have a fuel pressure of 55 (vacuum hose not pinched) and you want to richen the fuel curve across the rpm band you would want to increase the fuel pressure 2-3 lbs or more depending on how lean you were. On the flip side you can decrease fuel pressure. So in essence you can only decrease or increase fuel pressure across the RPM band.

VAFC on the other hand will fine tune your RPM band. You can set it at whatever tuning RPM points you want and lean it out or richen it up to a certain point. I forget how much you can lean it out before a CEL will happen from what i am told. I haven't gone that far. So to recap, FPR you want to tune first and then move to the VAFC and fine tune the fuel curve.

Mike

 

But in essence, they do the same thing correct? For instance, if I raise my VAFC fuel points 10% across the board, it would be the same as raising my fpr 3lbs. These numbers are just example purposes, but what i'm getting at is that it has the same affect... ??

 

yes they can do the same thing but have different parameters. you want to tune the FPR across the whole RPM band and then fine tune it after that. For fine tuning an example would be to lean it out on top for that top end power.

 

The FPR is a bazooka and the VAFC is a sniper rifle

Your state of tune will depend on how "tuned" you want your A/F ratio to be.

You may have a lean spot at 7600rpm to 8000 rpm but run a tad rich before that.....with the FPR raising the fuel psi to combat the lean spot at the top creates a rich flood at all rpm points below 7600 (as an example)

The VAFC will allow you to take care of multiple hot spots in your A/F while the FPR should be used in support of the VAFC to compensate when your so lean you have to max your settings to take care of a certain hotspot.

At which point being able to raise the fuel psi a few psi and then lean out the other areas works better than just lowering the timing and settling on losing power you know you COULD have had you had the capability to add a little more fuel....not a bucket full

 

Sweet. Thanks for the help guys. I'll get an FPR eventually... for now, VAFC is just richened like a ****.

 

I learned my lesson real quick......I have my settings maxed.....

Needless to say my B&M FPR and Fuel Pressure Gauge are going in before my next dyno session

For Less the $70 having a whole new dimension to you fuel tuning is a good deal.

 

What's your setup to have your settings maxed? I'm running basic bolt-ons and CTR cams and running 9% before hi-cam and 12% after engaugement.

 

The FPR is a bazooka and the VAFC is a sniper rifle


I like that analogy SERG.

 

AFC cannot adjust more than 5-10% positive AT MOST.
Its really not that effective at richening the mixture which is why you need
to be able to raise fuel pressure

 

C'mon now, remember I am an expert with an M16

Now I am debating between a B&M or splurging for an AEM FPR.....any real differences besides the reliabilty of the AEM unit I should know about?