adjustable fuel pressure regulator

[JMo60]

is the lt-1 fuel pressure regulator the same as that on a 3100? they look very similar and was wondering if an aftermarket adjustable one will work with my 3100 fuel rail (which is on a 3400). Also, there is one made for the 3800 supercharged engine, which i think should work also.
Also, what other kind of regulators are people running?

[SappySE107]

I have a cap you can use to modify your stock FPR to make it adjustable. Cheapest solution. TCE is working on some lines to run aftermarket AFPR setups as well but they aren't done yet. The LT1 is backwards on the mounting I believe. I asked franz a long time ago when I first got these caps and he said I couldn't use them.

[prophiseer]

Casper doesn't sell the FPR for the 3400's anymore (and I can't find a listing for the 2.4L Q4's, either)

if you don't run across one, a FPR that fits a 2.4L Q4 will fit, similar style, the retainer bracket is opposite on the Q4 motor. If you carefully grind the bracket down near the bolt hole, and grind down the retainer clip also and flip it over, it'll work. You might also need to grind a very small amount on the intake neck of the UIM. This is how I got one for my 3400 motor. The adjustment range is the same for both motors.

You can get a 2.4L FPR here:

http://www.smgmotoring.com/products/52

http://www.pfyc.com/store/merchant.m...y_Code=GAUNDER

I can take some pics of my setup with it if need be

[SappySE107]

Yeah, my caps don't look that nice but they work the same way. 190? How about 40 bucks and you modify your own with a dremel and some JB weld?

[JMo60]

how difficult is it to modify a stock regulator?

[JMo60]

i think i might have to take you up on the cap for making my own. does anyone have any experience tuning with a fuel pressure regulator? was curious to the results as opposed to tuning a computer for fueling.. I have the obd 1.5 computer for a 3100 running a 3400 with a mild cam, and soon to be headers

[SappySE107]

You really need a way to tune it. The FPR is only useful for increasing fuel output and better atomization. It won't let you 'tune" it.

[treeZ24]

hows that with the fuel atomization there ben?

if i bumped, say, my 24# injectors (off a 2000+ 2.4L) to 60psi instead of 56 psi i would get slightly better atomization?

or will it really make no difference.

will the injectors like it...?

[SappySE107]

Im not sure what 4 psi will do for you but going from 43 to 55 like GM did will help. I think injectors are good to 70 psi but I really don't know for sure nor what different injectors are good for. Actually, don't the dry nitrous kits up the fuel pressure?

[mfewtrail]

hows that with the fuel atomization there ben?

if i bumped, say, my 24# injectors (off a 2000+ 2.4L) to 60psi instead of 56 psi i would get slightly better atomization?

or will it really make no difference.

will the injectors like it...?

It might make a difference if you actually need more fuel. Raising the pressure 4psi is going to make those injectors flow approximately 1# larger than they're rated for what it's worth.

BTW, why are you running 24# injectors anyways?

[hondaetr]

hows that with the fuel atomization there ben?

if i bumped, say, my 24# injectors (off a 2000+ 2.4L) to 60psi instead of 56 psi i would get slightly better atomization?

or will it really make no difference.

will the injectors like it...?

I hope this is not a highjack in progress, and this is helpful
To find the new flow rate....

NOTE: ^= square root (rounding to hex decimal)
[^ (new pressure / old pressure)] X old flow rate= new flow rate...
[^ ( 60psi / 56psi )] = ^[1.071428] = 1.035098 X old flow rate...
1.035098 X 24# = 24.842352 new flow rate and is insignificant.

TBI @ 13psi for v-8 = 61#
go walbro and up to 25psi= ^(25/13)=1.386750 X 61#=84.591779 YEAH!

To find injector size requirements..
Horsepower X Brake Specific Fuel Consumption (this is .45 for NA and .55 for forced induction) / (number of injectors X .80% duty cycle)
Ex: (160hp X .45 BSFC) / (6 X. = (72) / (4.= 15 lb/hr injectors required

To find the max hp a given injector can make..
hp = (flow rate X # of injectors X max duty) / BSFC
Ex: hp = (24# X 6 X .80) / .45 NA
Horsepower = 256 max NA (or only 209 forced induction)

[hondaetr]

Why do i see smileys??

[SappySE107]

because 8 ). Gotta put a space in there.

To find the new flow rate, I take 23# @ 43 PSI for example, and at 55 psi it will be ( 23/43 ) * 55.

[prophiseer]

Equations from Edelbrock's page

Some more info that might help anyone in the dark:

In theory, adjusting the FP too high won't do anything at all but bog the injectors - there's too much pressure behind them to spray effectively; and on the flip side with too little, the injectors won't spray enough.

Each set will have their own psi that they flow best at for their ratings, a lot of the time you can obtain this info from the manufacturer (the psi they test the injector at for what it's rated). But it's also a better idea to adjust the FP with the motor full hot and preferably after the PCM has gone into closed loop, especially on OBDII vehicles. As the motor warms, the PCM shortens the dwell time on the injectors, and they bleed off less pressure from the line (in other words, fuel rail psi is at it's highest).

If your going for performance, always buy and replace injectors in a set, even if they're stockers.

The biggest reason I argue against stockers, though, even for John Doe rollin into the shop, is that stock injectors are usually allowed a 5-6% lb/hr variance as they roll down the line; bringing the variance lower jacks the price of each individual injector, and also slows production - so if you buy a set of 6 stock injectors, you might get 2 that spray 17#, 3 that spray 19#, and one that sprays 18#. Performance aftermarket injectors are typically within 1-2% variance (depending on company), and many also sell sets that are pre flow matched before they're boxed. When each injector is spraying the same as the other, everything starts becoming a hell-o-lot more efficient and consistent (which increases hp, espcially after the PCM figures out the fuel trim).

Also to consider, though, if your running high flow injectors, it's a wise idea to install a high flow fuel pump. If your rail is set at Xpsi, and the stock pump can't deliver a high enough volume of fuel to keep a consistent pressure, psi lowers (obviously) and defeats what your trying to do.

[mfewtrail]

If you're lazy like me, there are plenty of fuel injection calculators available online.

http://www.witchhunter.com/injectorcalc1.htm

http://www.iroczone.com/calcs/injectorsize.htm