Exactly. So another question...Is it possible to measure the voltage at the pump with a multimeter when the key is in the ON position, thus telling me whether or not I need to rewire it? Or does the voltage change with the car running, which would nullify the test? :dunno:

you can measure the difference between the battery and the plug for the pump. this will tell oyu if you have a significant voltage drop or not.

of course you can always measure it with the car running as well.

Me tinks I'm gonna go do that right now....I'm bored....

as am I. let me know if you need help!

The only way to know if the problem is a voltage drop is to test it during a pull. Sometimes you can't even detect it on the first pull as the wires need to heat up before resistance increases. I have experienced it before multiple times. It seems fine for the first few pulls and then gets worse and worse.

However, even if the voltage is correct there may still be a problem if your pump is insufficient. The only way to test that is to notice a fuel pressure drop during a pull. All tests must always be done during a pull as that is when the fuel pressure gets increased as well as the fuel being used.

thewird

Not surprisingly, sounds like I'll need to get the car on a dyno to fully diagnose the problem...

Not necessarily. Since you already bought the new aeromotive pump, just make sure its rewired when its installed if its not already rewired. Then see if that corrects the problem. A new fuel pump does not require a retune unless fuel pressure is changed.

Something you might consider though is a fuel pressure gauge for the cockpit. That way you can always know if your fueling is good and/or when a problem occurs. I look at my fuel pressure gauge just as often as I look at my wideband.

thewird

or an empty road ;)

That's something I've always considered as well...just don't like the idea of fuel in the cockpit, although I know there are other ways. :P

I know I won't need a retune with this pump, but I will should I decide to go with 1000cc primaries.

As long as we're on the fuel subject, what's the proper way of "jumpering" the fuel pump to pressurize the system with the car off so I can check the static pressure of the fuel system? Cliff brought up a good point that I'll want to check the static pressure with the car off, and after installing the new pump set it accordingly. :icon_tup:

on the FD you jumper "F/P" and "GND" in the diagnostic box to pressurize the fuel system with the engine off. On the FC there is a yellow connector on the passenger strut tower.

Awesome, that's exactly what I needed to know. :) Thanks!

40psi on the nose. Will be interesting to see see what the static pressure is with the new pump...

The most accurate way to check your fuel pressure is to pull the vacuum line for the FPR while the car is running. When the car is off, the voltage may not be enough to verify the correct base pressure.

Also, most fuel pressure gauges now are electronic so you put a sensor in a spare FPR port and run the wires inside. So no worries about fuel inside the car.

The base fuel pressure shouldn't change with a pump change as that is controlled by the FPR.

thewird

Ah, Ok. I was told that the base pressure would change with a new pump. Either way, I'll probably check the pressure after I put in the new pump just to be sure. :)

i am late to the thread but thought i would still add my 2 cents.

your IDC (80-90%) clearly shows you have a flow restriction or pump problem.

516 rotary rwhp is 68.46 pounds of air per minute. at 11.7 AFR that is 5.851 pounds of gasoline which converts to 3486 CC/Minute.

3486/4900 = 71% duty cycle.

the addition of 200 CC of meth @ 57,250 BTUs per gallon adds 2596 BTUs net of the water's cooling BTUs so the gasoline (base fuel) CC/Min should be 3401 or 69.4% IDC, not 85% IDC.

most of this has been diagnosed above.

fixes would be better fuel pump wiring, a check of the two filters, a diff pump or my favorite a Kenne Bell Boost A Pump.

as the pump you ordered:

setting static at 43.5 pressure and adding 23 psi boost (your dyno setting) we end up at 66.5 psi.

if we use the standard line pressure of 43.5 psi static and 23 psi boost (from your dyno run) the pump delivers 270 L/H or 4500 CC/Min at 13.5V.

you should be using 3400 at 516 so you are fine.

your situation underscores the need to run a digital pressure sensor in your fuel pressure regulator so you can datalogit and KNOW that you have no fuel pressure problems... as they can be deadly. they are inexpensive and are easily wired in to your auxilary bar on the Datalogit.

once ready to roll you will be taking fuel settings down in your base fuel map.

howard

Great information, and thanks! :icon_tup: I am replacing my fuel filter just to err on the side of caution, along with rewiring my fuel pump (once I get the new one). :nod: Next will be to order a datalogic and fuel pressure gauge, just to keep an eye on things.

x10,000.

Howard, what are your thoughts on my injectors? Are they sufficient assuming proper flow from the fuel pump?

"my injectors? Are they sufficient assuming proper flow from the fuel pump?"

in a word, yes.

your turbo can make 550 SAE rw rotary hp... 73 pounds per minute of air.

at 11.0 AFR that would call for 6.63 pounds of gas per minute.

your injectors should do 4900 CC/Min at 100% duty.

we want to run them at no more than 85% or 4165 CC/Min

4165 is 6.895 pounds per min of gasoline.

howard

Love the math. :icon_tup: [I knew you'd come back with the calculations, hence why I asked] ;) And it makes perfect sense when you put it like that. Thanks again!

Howard, you are omitting injector lag in your calculations. An injector at 85% duty cycle is not flowing 85% of it's static flow unless it has zero lag time, which does not happen in the real world. Injector sizing should consider maximum RPM as well to properly account for this.

Had to come back and update this thread. I have more fuel than I know what to do with now. :lol: For anyone considering buying this pump, I have some advice for you...Do it. DO IT NOW. Seriously, why haven't you ordered this pump yet?! I changed the pump, did the rewire, installed the new fuel filter, and checked the static fuel pressure @ Dave's shop (KDR), then slapped it on the dyno.

First pull, PIG RICH...A/F pegged on both my WB and Dave's @ 10.0:1 (was clearly even richer than that). When all was said and done, we were able to drop 15% duty cycle from nearly all of my maps. This pump is insane...You just can't beat how this thing flows for the price.

(Aeromotive Stealth pump posted earlier in this thread is what I'm running, btw). I'll post a video of Dave rippin on it on the dyno after it uploads. :D If you pause when I zoom in on the dyno sheet after the pull, you can see the A/F ratio PEG at 10.0:1. ;) Dave started romping on it because Kyle was making fun of him sucking at figuring out my clutch. :lol:

http://www.youtube.com/watch?v=d34th30DvSk

Tarp, it's good to see that you fixed your problem. Sorry I missed your call I've been crazy busy the last couple months. We should ge together sometime soon. Also pleased to hear that you are happy with the pump. I'm going to have order one (or two)! ;)

Dave, you're crazy. :lol: Don't worry about missing my call...I understand you're busy! Hope things are going well with your FD! :nod:

So you had the original fuel pump wiring in there before?