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.