In my Fox ls1 swap I opted to run a return style fuel system. Im using S@P rails with the 97 vette regulator in the rail.

My question revolves around the stock tuning in relation to fuel pressure. I have the regulator hooked up to a vacuum sorce so it gets about 45psi at idle and maxes out my 60 psi guage at WOT. (I think it is at about 62 psi. The needle doesn't reach the stopper peg on the gauge) With this setup I get about 10mpg in the city and 16 on the highway.With this setup I have the best power and drivablity.

Now if I hook up the vacuum port of the regulator up to the hvac system tree it will pull vacuum all the time and no matter what I see 45psi. Them my milage goes way up to over 20mpg. However my SOTP meter is telling me my car is a slug at WOT. Regular driving is fine.

Has anyone else experienced this problem. This $3.59 a gallon gas in chicago is a killer when I need to fill up.

FYI. Im running a 99 camaro pcm.

 

i have the 97 return style fuel system as well, i thought the fpr was supposed to be vented to atmospheric pressure?

 

That's correct. To match the fuel pressure to the PCM calibration the FPR should just be vented to the atmosphere, not hooked to vacuum.

 

John:

I got my harness and reprogram from you a couple of months ago.

Works SUPER!

Was set up for return line system (not the vette returnless ect.)

Right now I have it hooked to vacuum (I thought when we discussed I was to hook it to vacuum). Original 2005 motor with 1999 return fuel rail.

So, vacuum to regulator on the fuel rail or not?

 

It depends on the engine or more importantly the calibration used to set it up with. If your setup is based on a truck engine then the fpr would have been hooked to vacuum. If your engine is an LS1 I wouldn't have said to hook the fpr to vacuum unless for some reason we decided you needed to (supercharger or turbo), in which case I would have set the injector table up to be used with a vacuum referenced fpr.

I'm glad everything is working well!

 

Thangs for the info. Now I just need a tune so im not getting 15mpg and worse.

 

Does anyone know where to get an ajustable regulator for the vette rails. I remember seeing one for about $120 but cant seem to find it for sale on any of the sponsor's site's.