Fuel questions - Leaning out @ top of 4th...
 

Ok, so let me start off by listing my fuel setup :

Aeromotive AFPR
850 primaries/1600 secondaries
KGParts rail
RP fuel pump from RX7.com
Lines from pump to rail are stock
Also worth noting that I'm running a dual nozzle coolingmist water/meth kit, running boost juice

We dyno'd 516RWHP with my new 4" exhaust last year, and pretty much stayed solid at 11.7 all the way to redline during a 4th gear pull on the dyno. However, it's worth noting that it was about 90 degrees with 60 % humidity. Not long after dyno'ing, I put the car away for the year. Now, fast forward to the present...

This year I am experiencing some hesitation/stuttering toward the top of 4th under a high load, and I had a friend ride with me last night to watch my WB. Well, as it turns out he said I was steadily leaning out as I pulled through 4th, leaning out to 13.xx @ 7600 RPMs (not good at all, I know). It's been considerably cooler this time of year, with MUCH lower humidity, so naturally oxygen density is significantly higher than when I dyno'd last summer.

My question is what do I need to upgrade to get my fuel system up to par here to reliably support 500+RWHP? Do I need a Bosch 044 fuel pump? If so, where do you buy them? Also, is it necessary to replace my stock fuel lines with SS larger diameter lines? If that's necessary, what do I need and where do I source those parts?

I was told previously that the RP fuel pump would be sufficient for 500RWHP, but looking on RX7.com's site it states that it'll only handle 500HP @ the flywheel. Huge difference...

Lastly, if I do just need to replace the pump and/or lines, is it necessary to go get retuned after that? I am running a PowerFC.

Any help here would be greatly appreciated! :icon_tup: Thanks gents. :)

fuel filter?

Very good point. :icon_tup: Fuel filter was changed ~8k miles ago. Possibly clogged already? :dunno:

Has the fuel pump been rewired with 10 gauge wire all the way inside the fuel tank to the pump?

thewird

I will have to check on that...pump was installed @ KDR while I was having some other work done, so I don't know at the moment.

Is that pump really sufficient for 500+ at the wheels though?

could it just need a retune, if it really is that much cooler then there that would definately cause a lean condition, you should have more than enough injector, but whats your IDC? i would probably upgrade fuel pumps as well.

well you did 500hp at the wheels with it, so i'm going to say yes.

so this year its lean, fuel filter is an easy preventative step. its also possible that the ECU temp/baro correction maps aren't setup very well, and it is hard to set those up, because you almost need to have the different weathers to tune it.

its possible there is something else going on, and it seems that more pump would be a good idea, but start with the basics.

We've tested the same pump, and its out of flow @ 460rwhp.

You need more pump!

Thanks for the info guys, I really appreciate it! :) IDC is high...IIRC, it is around 80-90%. Car was tuned by Dave @ KDR. I think I'll pick up a fuel filter just as preventative maintenance. Which pump should I go with? Is the Bosch 044 the most common? Where do I pick one of these up? Is it necessary to replace my fuel lines? Thanks again for the help!

Edit :: Looks like I can get the 044 pump @ rx7store.net...Also, am I reading this correctly? You install the 044 pump downstream of the inline pump, which provides better output? (Taken from the rx7store.net description)

Please confirm that the pump has been rewired. It probably has, but please confirm. Any kind of maps or datalogs would also be a big help. It sounds like the weather has changed enough that the air temp compensation table may just need to be tweaked. It's not easy to get that dialed in one day. Sometimes you just have to wait for the weather to change and go back over the map. One thing I would do to figure out whether it is the air temp table or not is do a test run where you add fuel via the rpm compensation table in the commander.

If it turns out to be a matter of fuel pump flow the other option is something like a Kenne Belle Boost-a-Pump which increases voltage to your existing pump. You may also want to look at a Deatshwerks 300lph pump. I haven't tried one yet but I have used their injectors before. I prefer the simplicity of a single pump when it's feasible. There's just less to go wrong and less modification in general required to the vehicle.

http://i227.photobucket.com/albums/d...pFlyerBack.jpg

http://i227.photobucket.com/albums/d...DWFuelPump.jpg

https://www.rx7club.com/attachment.p...1&d=1243124607

This is what you want, engine rpm specific correction. Try adding 5% at the 4000 and 5000rpm breakpoints and 10% after that, so 105% setting and then 110% setting. See if that does anything. This will help you narrow it down.

I would say you are out of pump. I'm surprised that you are just now running into this issue with the power you've put down. I don't think Dave will rewire the pump unless you specify that when he does the install. I think what everyone needs to remember is your horsepower numbers come with a healthy dose of meth injection which is adding additional BTU's. I know some people will say otherwise, but I personally wouldn't trust a Walbro over 400 wheel horsepower and a Supra Denso over 450.

Tom, do you have a Datalogit so you can log and post your runs?

Everyone speaks highly of the Bosch pumps, but they are a little more difficult to install. You also have to be careful as there counterfeit Bosch pumps on the market.

I've been looking at the new Aeromotive replacement pumps that just came out. They are easily sourced and fairly priced. http://aeromotiveinc.com/products-pa...-offset-inlet/
http://www.3sx.com/store/catalog/fue...-flowchart.jpg

That's great information, thanks arghx. :icon_tup: The weather is total sh*t right now (rainy), unfortunately, and looks like it will be for the entire following week. :(

When I do get a chance, I'll try adding fuel via the RPM compensation table. I also agree with respect to keeping things simple in terms of 1 pump. Do you know of anyone that's had any experience with the pump you posted? I'd love to try it, but don't really want to be the guinea pig. :P What are your thoughts on the 044 pump? I assume you like that pump as well, but it adds to the complexity since it's an additional pump...but (correct me if I'm wrong) it's also a proven pump, and flows 300LPH.

Honestly though, whether it is or is not my pump causing this issue, I think it'd be a good insurance policy to get one rated to support 500+RWHP. As turblown pointed out, this one just doesn't seem to be up to the task...

Dave, unfortunately I do not have datalogging capabilities, otherwise I would post up some datalogs. :( Pardon my ignorance, but what significance does rewiring the pump have?

Good advice. We've got those aeromotive units in stock, just did one a subie yesterday...

Dave, that looks like an awesome pump. I just tried calling you, btw. :P In terms of rewiring the pump, I'm guessing the old wiring gets shotty and therefore the voltage drops, causing the pump to not flow up to its full potential? What's the proper way to rewire the pump assuming mine hasn't been done?

my 1986 FC had fuel issues and it turned out to be junk inside a gas tank from old age , everything was rotting inside .
take a fuel sample from the bottom of the tank

adjusting the RPM correction map really is a band aid for the true problem, but could help the diagnosis. I would adjust the air temp correction first, as it's just 4th gear you are having this problem in correct? well, in reality i'd be getting a new pump first, but you know that already ;)

I'd also suggest getting a datalogit so you can log all the info you really need to diagnose this problem. knowing your injector duty cycle would be a handy thing to watch while this is happening.

also, 7600RPM in 4th? you must have been CRUISING!

wha???
""dyno'd 516RWHP""
you have enough and don't even need 4'th:lol:
:lol:kidding:lol:

Haha thanks Cliff. And yes, we were cruising. :P But keep in mind it was all for the sake of isolating the problem and seeing where AFRs fell. ;) Like I said on the phone, it was perfect since so much of Airport Rd was closed. Guaranteed no traffic! :D

So yeah, I just bought that Aeromotive pump. :icon_tup: Care to take a look at my air temp correction Cliff since you know far more about the PFC than I do? :P Sorry, all of my tuning knowledge is in Megasquirt. :blush:

if i can figure it out on the commander I'd be happy to. I'm use to using a laptop with the datalogit

Psh, you can figure out the commander Cliff. Have a little more faith in yourself. :P

Once I get my pump in I'll check to see if it's been rewired. If not, I'll take care of it. Also thinking about changing the fuel filter [again] just for peace of mind. :icon_tup:

oh i have no doubt I can...I just think you underestimate my commitment to laziness.

LOL...Ok, so that much may be true...

Yes, I suggested it as a quick way to help narrow down the problem.

Adjusting the air temp correction table is trickier than it sounds. The reason why it is tricky is because unfortunately there is only a single air temp correction table that covers both low loads and high loads. Without careful adjustment you can make the engine run consistently richer during normal street driving.

Yes definitely. When an FD gets to this level of modification it is important to be able to take logs for diagnosis.

agreed, but at this point it's better safe than sorry. i'd much rather see him run a little rich than blow the motor.

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?