http://www.kennebell.net/accessories...boostapump.htm

it increases the output of the stock fuel pump.

"How it Works - While dyno and street testing, our On Board Data Logger told us that fuel flow was less at night when the lights, stereo etc. were on. The voltage to the pump was varying between 12 and 13.5 volts and fuel was being reduced up to 15%. Further testing in our Fuel Flow Lab indicated that by elevating the voltage to the pump we could safely increase fuel capacity by as much as 50%. The Kenne Bell BOOST-A-PUMP™ does just that - and it automatically maintains the pre-set voltage or % increase with as little as 10 volts at the battery."

 

I didn't go to the link, but dabbling with fuel pumps is not the answer to replacing your FMU. Your stock pump is fine. The problem lies with the FMU. I've owned several blown cars and have NEVER used an FMU. If you need more fuel than your stock fuel system can hande, get bigger injectors. I understand they're not available right now and it's the main reason I'm waiting. FMUs are a cheap bandaid IMHO. The real way is with injectors and ECU tuning to adjust injector pulse width. You shouldn't have to touch your stock fuel pump unless you're running very high fuel pressure (which wears the pump). Increasing voltage of the fuel pump leads to premature failure by the way.

 

What is so unique about the stock Nissan injectors that larger ones are not out there? They are out there, just need to know what to look for. biggest prblem I see is getting an ecu to control them....not many options in that arena yet.

As for increasing vltage to the pump,it actually works very very well, and there is no downside whatsoever - we are not talking 16-17 volts here, just a more consisten mid 13-mid 14 volt signal to it.

I ahve not looked intot eh wiring yet of the stock Z, but many other cars, DSM's and Supras included, use a voltage regulator on the pump to aler fuel flow depending if the car is under throttle or not. Hardwiring the pump and eliminating the regulator is a great way to increase flow, and extends the life of the pump as well.

What ist eh stock output of the Z's pump?

 

adam,

interesting... so do I need to remove the stock regulator
before increasing the voltage to the fuel pump?

thanks,
rob

 

More voltage = hotter fuel pump = shorter life

Increase the flow all you want. It won't be properly tuned though.
Most supra guys install a 2nd inline pump with a relay to come on under boost. We're working on a T-78 2jz right now and this is what the guy wants (per instruction). But it is not needed. I can see how it would be useful if the stock pump were to fail under boost though..Then again, what are FP gauges for in the first place eh?

You can't just increase fuel flow and be done with it. You will be rich/lean all over the RPM range. This is where ECU comes into play. So right now, we are pretty much stuck.

Why in god's name would you want to eliminate the fuel PR? Makes no sense. The way to do it is to get an AFPR

 

I did not say remove the fuel pressure regulator, I said remove the voltage regulator.

yes I can se the point in a second inline pump as well - but its only needed for truly high HP cars, none of which anyone on thsi baord has yet.

 

Yep, the best way to get more fuel is to properly adjust the injectors and thier duty cycle. A lot of aftermarket FI kits use rising rate fpr to jam the fuel through the injectors. Some of them go as far at 125 psi on a stock injector, this is crazy. Injectors max at about 100 psi, you can only squeze so much through! BTW, I am talking about FI kits in general, not specific to the Z. On my eclipse my computer will not add enough fuel for my needs, so i installed more injectors into the intake runners on a standalone fuel computer. I don't believe in fuel pressures over ~45psi.

 

Yep agreed, and at 100psi you can bet you've passed the 80% duty cycle mark for your injectors. Not to mention 100psi will kill *most* stock pumps after a short while.

 

45 psi si fine for NA, not for FI though......but agreed, doing it the right way is always preferred, though its much more costly, and not always even an option.

 

I've run FP around 42psi@wot on a FI application with injectors,one pump and ECU (no fmu or knock retard box) . So it is possible. It's all in the tuning

 

Yeah, but it wasn't the 350Z ECM which has no boost sensing capabilities.

Yes you could run larger injectors and they are available from RC Engineering and PE. Problem is the ECU must be reflashed so the idle won't go to crap and you've still got to have a way to sense boost. Currently the only thing available is the Aeromotive Digital FMU.

 

that kb boost-a-pump "DOES" sense boost.
It only turns on when it sees >0 psi boost
so it does'nt affect your idle or off boost fuel
settings... after boost, it only has a gain setting though...

rob

 

huh? This makes no sense...

Of course flashing the ECU would be necessary when bigger injectors are installed.

 

why on earth would you run 42 psi on a car seeing positive manifold pressure? that tells me your fpr was not working properly. Something does not make sense.....

on a tubro car, typicall they run a base fuel pressure in the low to mid 30 psi range with the vacuum nipple to the manifold hooked up. At atmospheric (0 psi, or with the nipple to the manifold disconnected) it jumps up to the low-mid 40's (usually 42-45). From there, fuel pressure should increase 1:1 boost:fuel. So for every 1 psi of positive manifold pressure you see, fuel pressure increases 1 psi. If your fp is only maxing at 42 psi, you have got lots of tuning to do, and an fpr to sort out (maybe the vacuum line was disconnected - this would explain why it did not rise as it saw boost becuase it was never seeing boost). All facotry turbo cars run like this.

 

Lot's of tuning to do?
Did you not read what I wrote: The fuel injectors were replaced after the blower install.... from 19lb/hr's to svo 24lb/hr's. The car's PROM was then updated with the pulse width decreased across the board (but mostly on lower RPMs). The AFPR was basically left close to stock 36psi @ idle and 42psi @ WOT.

19lb injectors @ 42psi < 24lb injectors @ 42psi.

 

I read it, but if the car runs at 36 psi at idle, is that with the vacauum line connected or not connected to the FPR?

Also, at how much boost?

 

8lbs of boost @ 5000RPMs
Yea, the 36psi was with vaccum connected.

 

Not to beat a dead horse But if you had the vaccum line connected, your base pressure at idle was 36 psi,,akes operfect sense, as nearly every modern fuel injected car runs base fuel pressure in and around this figure. At "o psi" of boost (aka WOT on an naturally aspirated car or when you do the initial stab on the pedal on a turbo car), fuel pressure moves up to 42 psi (aka atmospheric). You cna also reach 42 psi as your base if you disconnect the vaccum line to the fpr while the ca is at idle.

Now, at 8 psi of boost, your fuel pressure should be 50 psi at WOT and full boost, assuming you are running a 1:1 fuel pressure regulator 9which every stock car comes with). That's 42 psi pressure at "0 psi" of bosot, then increasing 1 psi of pressure for every 1 psi of boost you are running this is exactly how any stock tubrocharged car runs, and its the most desirable way to tune a car in general, as it keeps the ecu happy. if it was not, either your fuel prssure regulator was not working, or your gauge was faulty. For many aftermarket kits, they are often packaged with a rising rate fuel pressure regulator that either eplaces the stock regulator, or sits iline with it (both ways work). In doing so, you are able to make the stock injectors behave klike alrger ones simply by increasing the pressure fed to them. This can be very effective to a point,but it is only suitable for low boost setups (i.e in and around 5 psi). over that, and your net result is fuel pressure that is simply higher than desirable for the stock system (especially the ecu), and you would be better served going to properly sized injectos and running the stock fuel pressure curve (via a 1:1 fuel pressure regulator).

By placing some brands of FMU inline with the stock fuel pressure regulator, you often can run higher boost levels, becuase this method allows you to set when the FMU kicks in. Let's say for example the stock FPR for a given ar can safely go to 55 psi, or roughly 13 psi of positive manifold pressure (aka boost). A datalog of the car shows it start to run a bit leaner than desired over 7 psi of boost. By fitting the regulator inline (some brands only) with teh stock regulator, you can "tell" the FMU to kick in once it sees manifold pressure read 6 psi (or just before the datalog showed the car running leaner than desired). Does it get the job done? Ys, for lower boost setups it works very well, and can do so very reliably. Is it the ideal way to to do things? No, not at all - ideally the ca should increase 1 psi of fuel pressure for every 1 psi of positive manifold pressure (keeps the ecu happy and is much easier to tune, plus you don't run the risk of pumping too much presure through the lines and injectors). However, fitting larger injectors also requires some way to control them, and not every car takes kindly to piggybacks (the Z is one of them Subaru's are typically another - both allow you a fairly narrow area to adjust before the ecyu freaks out and starts scaling things back. Mitsubishi's on the other hand (at least the factory turbo ones such as Eclipse, Galant, 3kGT, evo), are VERY forgiving about piggybacks and allow a tremendous range of adjustment). Fitting larger injectos and a method to tune them is often very expensive, or not easily done depending on the car, so a rising rate regulator can be an effective means of extractign a bit more from the stock injectors. There are plusses and minuses to it as stated above, so its all about what you are most comfortable with.

 

Yes I'm aware disconnecting vaccuum at idle simulates WOT @ 0psi (no boost). I can not say for certain, but I believe fuel pressure was around 42psi @ WOT with 8lbs of boost. Since I am not 100% sure, I will have to check .You've brought up some excellent points and got my brain thinking (that's a rare thing).

I'm going to do a full throttle run (in the car I spoke of previously) tomorrow. I'll record: baseline fp, fp w/ no vacuum, and fuel pressure under boost. I'll come back to let you know the numbers I got. The gauge I'm using is an Autometer and is +-2 accuracy compared to mechanical.
Thanks

 

is the FMU the weak link for the ATI or do you guys just want to use something different?