Adjusting fpr with 272 cams.

[El Cuervo]

HI. Quick question here. How do you adjust the fpr (adjustable) when you have 272 cams? My problem here is that. Before my cams, I had my fpr adjusted to 37psi with the vacum hose disconected and plugged. My Idle was at 750rpms and I was getting vacum readings of about 18. It was all good. No gasoline scent or nothing. Now with my new cams, I get vacume of 10 to 11 and it does smell like gasoline from the exhaust. How do you guys adjust your fpr with cams? Thanks.

[BTW, this is off topic but. Yes, there is a pretty big difference between the bc cams and kelford cams and stock cams, with a stock turbo and stock psi. Kelford all the way!!!!]

 

[gsx7707]

it shouldnt affect your fuel pressure.pressure is pressure.the difference may be with the cams lift and duration.the only way to truly know where the afrs are is with a wideband.

 

[El Cuervo]

What about vacume? With more agressive cams, vacume is much less. I went form -18vac to -11vac. Doesn't that affect the fuel pressure? I was under the asumption that the more boost you have, the more fuel pressure you get. This is to feed the larger valume of air pushed by the turbo. So more boost or positive pressure on the vacume line will close the fpr. Thus allowing less fuel to return. So this could apply with vacume too. The more vacume you have, the more the fpr will open. Allowing more fuel to return to the fuel tank. Thus creating less pressure on the fuel rail. So, if I have -10vac to -11vac on Idle, instead of -18vac. Does this mean that I am getting more fuel pressure ( about 4psi more) than what I should be getting thus causing my rich condition on Idle?? I know because I can smell it and my plugs were black and smelled like gas.

 

[tenn-gsx]

The afpr will automatically adjust for the lower vacume. Thats how they work. Just make sure your fuel pressure is still 37 psi with the manifold pressure source line disconnected. Your issue is more along the lines of needing to be re tuned for the different cams.

 

[El Cuervo]

Its possible. I'm just trying to get everything adjusted before I go messing around with a tune. I'm sure that I also have a bad ISC since I'm having Idle issues when going down hill in neutral. Trying to take care of all the mechanical problems first. Besides, I still need to save some cash for a good tuning device. So, if the afpr adjust for the lack of vacume, (say 10vac instead of 18vac) why is it recommended to check for vacume leaks? And why is it a concern if aftermarket cams are used? For those that have cams and such, how do you deal with the fuel set up and low vacume? Other than the electroic way (tuning: dsmlink, jackal, maf translator, etc). Is there a way to adjust this via a mechanical way? Like I said before, I'm trying to get rid of all the mechanical bugs first. I'm 100% sure that I have some boost leaks and maybe even some vacume leaks, since its been pretty cold lately.

 

[tenn-gsx]

Im unaware of any way to make adjustments to fuel aside from a tuning device.

 

[El Cuervo]

Yeah. the only thing that I can do is to make sure that I don't have any boost/vacume leaks, and timing is set properly. Along with good spark plugs wires and properly gapped spark plugs. Long were the days of carburators. . Thanks man. If anybody else has any imput, please feel fee to post, as this will help others with similar problems.
Thanks.

jorge.