jmmorriso

I want more fuel pressure. I assume a rising rate is the way to go, which ones have board members had good luck with? I was looking at a Vortech boost referenced one for my 280zx NA, thinking that vacuum would drop fuel pressure the same as boost raises it, and the vortechs are rebuildable with different diaphragm/spring setups for different boost/ fuel ratios.

NismoPick

I've been lookin at some rr fpr's as well. But they really don't do much good on a N/A car, and you don't want "less" fuel, you want more. For an N/A car, an ajustable regulator will do. For a forced induction setup, it helps to raise the fuel amount as the boost level increases.

jfairladyz

The problem with most rising rate FPR's is that they operate on a 1:1 ratio. Not all cars like that ratio. I'be heard a lot of people complaining about overfueling because of an aftermarket FPR. Some companies, and I think Vortech is one of them, offer RRFPR's that have ratios up to 12:1. But that's more so for forced induction. Nismo's right in the fact that you should just get an adjustable unit to allow the amount of fuel pressure you want/need. If your car is stock then you're waisting your money unless your FPR is bad and you want to upgrade instead of buying an OEM replacement. Until you outgrow your stock injectors you're probably not going to see the need for more pressure from your NA motor.

jmmorriso

I was also thinking about threading the vacuum port and putting a screw into the stock regulator to raise fuel pressure. Can I just run without the vacuum line on the regulator? I was also thinking about locking the ignition timing out. We dont have any problems on the chevy race motors with 40degrees timing and a fuel mixture so lean there is only color on the base of the insulator of the plug, with 11:1 compression and iron heads on 110 octane with oxidizer.

RubberBerner

If the vacuum line is off the FPR, it will just raise the pressure (rich idle). Locking the timing out as in not letting it advance or retard? if so, thats kinda dumb, because its there to keep from detonating and misfiring. Maybe you meant something else...didn't quite follow you. With 110 octane, that will prolong detonation aswell...but how often do you drive around the street with that in your tank, especially when gas prices are as rediculous as they are now!?

Bleach

sounds like the engine will run at its best only at wide open throttle and high rpms. Not good for drag racing or autocross...

You need a much bigger cam (longer duration) in that engine before you can think about maxing out the fuel injectors. These engines run rich at high rpm due to not enough air getting in. More cam is more air. Then port the head and intake... THEN you might need more fuel with a RRFPR.

NismoPick

For the N/A engine anyway... I've maxed out my injectors @ the stock fuel pressure now... she leans out when I'm boosting above 12psi. I've installed a Walbro 255lph pump & now I just need to up the fuel pressure.

jmmorriso

I didnt realize these guys were so robust. I just got my turbo AFM and will be building the hybrid AFM soon. then a big TB and header then cam. How crazy can i get with the cam without losing too much streetability? I was thinking the MSA stage 2. Any suggestions, comments?

jmmorriso

oh witht the race motors, they idle well at about 1100, and on the dyno pull pretty hard to about 8grand and the only longevety issues have been valvetrain (too much spring preassure). The latemodel class we run in runs a Holley 2barrel and we can still make a reliable 430hp. Cam specs are a secret, but we have so much lift and overlap that Idont think it would be possible to detonate it. low end isnt a problem when you have a 6.250 rod in a 4.125 bore by 3.330 crank. that length ratio is the secret to making torque in a short stroke motor like that. It keeps the piston up by the combustion chamber longer so the combustion event is doing more work, faster.

jfairladyz

For performance purposes you really don't need the vacuum advance at all. And most distributors on the L28 with any age are most likely locked up anyways as the bearings tend to dislodge which prevents the advance plate from turning. As far as the mechanical advance goes, if you're running your ignition retarded enough to do so then you don't need it. But if you retard to much you can have an issue getting the car to start. Part throttle will also suffer if you go that route. Removing the mechanical really has no benefit other than preventing timing fluctuations. But thats gonna take a whole lotta RPM's to do that (well over anything an L28 will ever see). You can also try changing out the advance spring to change the advance curve.

y2daniel1981

what fpr would be good for my 280zx turbo? I know autozone has a holley electric inline fuel pump with an adjustable fpr for like $130 but since it's Autozone I'm kind of skeptical

NismoPick

Wow... bringing another thread back from the dead.

I haven't heard of any fuel pumps w/ the fpr attached to them... kinda hard to do since you need the fpr AFTER the injectors... which is way down the line from the pump. Are you sure that Holley pump is for fuel injection & not for carbs?

y2daniel1981

That's what I was confused about after the autozone man showed me the combo!



But the autozone guy said it would work, but I'm thinking he's an idiot because of it being a fuel injection car and it did seem that the pump/fpr combo would be more for a carb. I know zcarparts says it's for carbs only, so yeah....

Ok anyone know of a good fpr and pump then?

oh wow, i just looked at the date, i thought this was from august of this year, not last! But better to continue a thread then start a new one on the same topic, right?

jfairladyz

I've seen low pressure pumps (ie. carbs) that have adjustable pressure output. But I've never seen a high pressure pump that was adjustable at the pump. There's too much distance between the pump and the injectors for it to be a reliable and consistant means of regulating fuel pressure. FI engines are very sensitive to fuel pressure. Where as a carbureted engine can have the fuel pressure vary during operation without making much difference at all so long as the pressure doesnt drop to low or spike to high. And on top of that you really dont want the regulator before the injectors. Doing this reduces the volume of fuel that reaches the injectors. This is why the regulator is almost always (I've never seen it any other way) after the injectors in a fuel injected application (and any proper carb set up as well).

WildmaN

I know for a fact, that putting the regulator before the injectors. My Z wouldn't start at all. Verry weird that it didn't until we looked at Carl's Z. And figured out it was after and not before. Sure was annoying that day, to say the least.

jmmorriso

Newer FI cars have a non return setup. the regulator is in the pump,in the tank, and theres only one fuel line to the engine.