Hello, I recently installed a Holley adjustable fuel pressure regulator. I forgot to check my stock pressure before I put the new one on and put it up to about 44 or so. I am new to burning my own proms and I read in one of those great tech stickys up there that "if your changing the pressure, the number you multiply with is given by this formula squareroot{(new psi^2)/(old psi)^2}"

So my question is if there is something else I can do or if there is someone who can tell me what the stock fuel pressure regulator ran at in a 1987 IROC Camaro 305 TPI.

I assume in tunerpro it is just a matter of adjusting the injector flow rate?

Any help is great guys.

 

Stock pressure is roughly that. Don't sweat it.

Brief rant:
Not sure why people buy AFPRs, though, and keep the stock pressure. If you are running out of injector (high Duty Cycles at full throttle near HP peak), then yeah, you can band-aid it with that and raise the pressure (but also raise the inejctor constant), but realize the pump's total flow rate goes down, current load goes up, and lifespan goes down. It's a large tax on an aged pump. With a new walbro, though, no problems. AFPRs should not be used as a fuel mixture control device - that's what the PROM is for. Proper size injectors won't tax the fuel pump at all (but the pump has to be able to flow enough for the engine still).
On the TPI board I read AFPRs are high on the list of good mods. Maybe it's a good placebo, or maybe a knock suppressor, or engine cooling device, or a traction "enhancer" (read slight bog). The better vaporization is BS in my book, unless your injectors are shate. The extra richness surely isn't necessary when compared to the factory's high 11's A/F.

 

Hey thanks for the info. In my first post I made a mistake and said I set it at 44psi. I actually set it to 47psi which was reccomended by TPIS. So what happened was I forgot to check my stock pressure before I put the adjustable in. So I was wondering how much a change over stock 47psi is. You stated that stock is roughly 44? I will use that as a base to calculate adjusting my PROM for the higher pressure. I am kind of doing this PROM stuff on my 305 to practice for when I put in my built up 350 in which case I know I will need to go to probably 24lb injectors.

Oh by the way, when you get back to the states, I just live up the road in Atascadero and I would love to pick your brain on setting up my system for my 350. How much longer are you going to be in China?

 

Oh how I miss SLO (and Atascadero, for good measure).

I admit, my AFPR is set to stock pressure. I have it because I got it for free, and because I don't know what I'll be running in the future.

 

Where are ya at now Mangus?

I also am wondering what I add to my current injector flow rate constant. It is at 20.82 for both single fire and double fire. If my stock FP pressure was say 44 and I bumped it up to 47 what would I need to adjust this to?

 

I'm in China until AT LEAST Christmas (actually planning to get married here!). I also don't have a job or apartment in SLO anymore, which sucks (company shut down, probably because I left, hehe). My stuff and cars are in storage there, though. That'll be fun re-smogging them.
I'll definitely be looking for a job in that area, but I do have a standing offer to work for a guy in LA - he's the guy that did the mooneye's fuel injection, and smart-shift, and I've done some work for him before - even was on American Hotrod with him.
We've got a few more projects this year out here. EOBD is our next development, and 2 more OEM engine EURO 3 calibrations.
Actually, we used to work out of a residential garage in Atascadero before moving to SLO. I can't think of the street name, but it's on the hill side of the 101. Lots of mangy deer there.

Anyway, sure, IF I'm back in town, I'd be happy to talk anything american car related, hehe.

 

I'm gonna give a bump for my last question there... Any help would be awesome.

 

a) They should always be the same for both single-fire and double-fire
b) The constant should be whatever your injectors are said to flow. Use the MAF tables to tweak your BLMs in. That's my methodology, anyhow.

Contrary to that, some people use the injector constant as a "global" fuel trim, in which case you would use some datalogging/monitoring and some adjustment to the injector cosntant to "rough in" your BLMs, then use the MAF tables to get it even across the load/RPM range.

In the end, the ALDL output and/or your wideband is your friend. IT and only it should tell you where to set your fuel. Not some schmuck like me on the Net who's never driven or even seen your vehicle.

 

Thanks for your help on this. I am just getting into DIY PROMs and I don't even have a way to data log yet. Learning as I go!

-Jason