i recently came across a good deal on an AFPR and considered buying it. called the guy and didnt get a response that day, so i got online to see what a new AFPR runs retail. then i went on a popular LT1 forum to see what people had to say about adjustable fuel pressure regulators. while i was looking up prices and information i came across some info that the presence of an adjustable fuel pressure regulator is basically useless on the LT1. even if you step up the fuel pressure, your pcm will lower the pulsewidth of the injectors to make up for the increase of fuel. a lot of times people (afpr companies) will throw an afpr on a car then put it on the dyno right afterwards and see a small (5-6 rwhp) gain. what they dont show is that most of the time the next day that added horsepower is gone, along with your ~$100 you spent on the fuel pressure regulator. the pcm adjusted the injector load accordingly to the increase in fuel pressure. a lot of people argued saying "yea well it can be adjusted in the pcm to allow for an afpr"... wrong. the only way to adjust anything fuel related is through the pcm.

the only use for an adjustable fuel pressure regulator (on an LT1) is if you are exceeding your injectors' duty cycles which is a bad idea anyways. you dont want to run over 85% let alone run them at 120%

just something to think about. i know i dont have $100 to blow on a useless mod.

 

note: not applicable to speed density motors ^

 

or individuals without a stand alone ECU

 

haha yea i dont think that applies to the majority of people that modify their cars with simple bolt-ons such as AFPRs, but youre right

 

Actually, most cars will self-trim the injector duty cycle if they start getting rich, that's what oxygen sensors are for. If you need the extra fuel, and the injectors can't keep up the flow, then a adj reg would work. That's a ridiculous waste of money for 5 or 6 WHP if you don't have enough mods to need the fuel control it gives you. I don't see the point. i'm sure that an FPR will help when you get out of the range of what the injectors can flow on their own..

If you don't need the extra fuel anyway, why does a FPR matter????

 

exactly right a good point.. however i used a afpr on my set up sucessfully this way:


took the injector flowrate table in he computer and moved it to a constant value (this compensates for the computer automated addition of fuel between max vaccum and o vaccum

then i pulled the base fp down from 60 to 50 so that my 42# injectors would idle decently then i let the regulator move my pressure back up 1psi per psi of boost i ran. so i only had to keep tabs on my one injector constant and of course my wide open multiplier.

if you are basically stock it would be easier to use something like a maf translator if you are looking to increase hp. you CAN do the same thing with a afpr BUT you can screw up the pulsewidth and wide open ratio up at the same time wich is no good.

all obd2 computers that i know of try to always correct themselves up to 25% of enrichment.. most times they sit slightly negative, around -10% fuel subtracted from the base table to cover a rich condition.. anyways if you have a scanning tool you can turn back the reported air to the computer with a translator (or edit programming) to get this percentage as close to zero as you can.. this would be where the computer is running dead nuts on... in some instances you will find a car running +10% (computer adding 10% more fuel to cover a lean condition) in this case when the trims are positive it will hold this percentage over top of the wide open fueling as well, causing a power rich condition, which robs horsepower.. getting rid of this with tuning or fuel pressure(increase) will definitely help.

make any sense? feel free to im me if i can help.

 

Tuning the ECU would really be the answer, but I don't know what's available to the OBD2 LT1 crowd these days. Fine tuning the injector duty cycle is really the proper way to do it, and then you won't need a FPR at all. If you need higher flow, get bigger injectors and trim back the part throttle and idle duty cycle. Or, keep the stock injectors, get a FPR, and trim back the duty cycle to compensate for the higher volume from the FPR. You're not talking about a rising rate regulator, are you? I hate those things..

 

yes boost referenced.. since the stock computer isnt boost referenced.. having a regulator trim in the fuel for me is a big bonus for tuning.. i have a charged air regulator, they are pretty huge with the buick crowd..

lt1s can use a bunch of stuff, most likely lt1 edit, as i used to use ls1 edit, both available from carputing.com

 

yes a fpr would serve some purpose with certain ecu manipulation but i am talking from a bolt-on basis only. and wouldnt you agree that adjusting fuel pressure, which would lower the injectors' pulsewidth, but exceed the injectors' duty cycle is not exactly the best idea? yes my motor is going to be starving for some fuel, but i plan on compensating for that by increasing the injector capacity, not by just upping the fuel pressure.

but your setup (MIGHTYMOUSE) of having the fpr increase fuel pressure per lb of boost definitely seems way more legitimate than most other peoples' setups.