Can I safely run 750hp FP with big turbos, etc and leave fuel rail, lines stock?

[speedtrapped]

So for sake of starting a new thread, I tried to dyno tune my beast, FMU CAI, DBR hybrid turbos, 3" DBR DP, 100 cell DBR race cats, 5 bar fPR, 750hp rated dbr FP, 52lbs ev14 injectors, and guess what, as my tuner dialed in the boost, easily over 25psi, my AFR was 12.5-12.8. He turned it down, suggested I get 90mm MAF housing, I was 340g/s at 4rpm, and suggested maybe the fueling is starved, ie rails and fuel line, which are stock. Now my set up as many remember was done at KMD, and Maha dyno'ed 644/788 at crank. I never did see an AFR reading on dyno sheet, but I did log, and I was getting same lean condition, only diff this time was tuner would not crank it up and leave AFR's lean, so kudos to Josh the tuner.
Any members have suggestions? Is there a fuel rail that will work, and what size ID line do I need for fuel line.
Tia

[kismetcapitan]

-6AN lines should be fine, but you should design a system that runs 2-4 of these lines as feed lines, and 2 as return lines. It's fine to run -8AN or -10AN singles to the engine, then use Y-blocks to split up the flow.

Japanese tuners have tuned to 12.5 AFR, but they have mystically detonation-free gasoline. I personally like 11.5:1, any richer and you start losing power and response, although when I run a full 30psi boost I will use a map that goes to 11:1 or even down to 10.8:1 - I'm not gaining power at that boost level, but I am gaining torque.

What interests me is that no hardware changes seem to be needed when running this kind of power? A tuner can map and reflash our stock ECUs even at 750bhp...that's cool.

I don't know if Audi used braided fuel lines; if they didn't, they will start popping pinhole leaks once you start pushing more fuel through them.

One way to confirm that fueling is the problem - have a fuel pressure gauge on the fuel rail (1/8" NPT port). Fuel pressure should rise in step with boost, but if the fuel pressure suddenly starts dropping, and if you've got the AFR gauge right there, you'll see AFRs climb as fuel pressure drops. Having 13+ gauges is very ricey, but for self-tuners, having that much info available is invaluable.

If someone can post up a diagram of the stock fuel system, we can start to design a custom fuel setup for you. And set up an account with Summit Racing - when you need serious fueling, you want NASCAR-spec gear. Aeromotive, Earls, etc.

FWIW, fuel rails aren't commonly the bottleneck in a high-flow fuel system. It's always the pump, and it spooks me that you're still using the stock system! But if you upgrade pumping capacity without doing the lines, you'll burst the lines. And if you go with larger diameter lines without upgrading the pump (or adding more pumps), you lose pressure and can burn out the fuel pump. I suspect that if you can feed the stock rail from both ends, and with good braided steel fuel lines and at least a twin-pump system, you should be fine.

Last thought - fuel pump controller. I am sure that Audi, like everyone else, has variable control on the fuel pump. The simplest setups cut voltage to 11 volts at idle and low-load and ramp it up to 14 volts when you really get on the gas. It may or may not be necessary to fiddle with the fuel pump control system. In my Skyline, I just hard-wired my pump relays to the battery, so they are always at maximum flow. This has the downside however of losing fuel efficiency as the constantly recirculating fuel generates a fair amount of vapor that gets vented out of the car.

[na1mt]

He is NOT using stock pump. http://www.dahlbackracing.se/images/...mp/pump670.jpg. This is the pump being used. If this pump will flow what is needed, than upgrading the line size and installing a Y and feeding each side of the rail would work.

[speedtrapped]

I am thankful for your input, but please look at the other thread, the pump is not stock! I swear! It's rated for 750hp, I bought direct from DBr. Are my lines stock yes. Take a look at fluid motor union.com they have a Frankenstein RS6 as an ongoing return customer, and have designed a 1600hp fuel system. I sent an email to Andrew krok there for some advice on fuel rails.

[marklar182]

As I said in the other post, I think with your current setup, the best bet is to change to Parallel feed on the rails. I believe you could modify the stock rails easily.

I am interested what FMU has setup, not that I will ever use it, but I am a nerd

[speedtrapped]

If I remember the rails have a soft line towards the front. So I could run a y there, and split the feed?, never mind the fuel is fed into FPR 1st. Ugh

[marklar182]

You can always install an aftermarket (Aeromotive) FPR on the return side so you could Y the feed, then send it to each rail, and then disconnect (cut) the hardline on the front of the rails and send those individually to the Aeromotive FPR as it has 2 inlets and one return to send back to the tank.

The Aeromotive FPR also has a 1/8NPT port so you can mount a gauge on it as well, kill that bird as well!

[kismetcapitan]

I posted on the other thread...be prepared to cry a river.

for the record, Aeromotive hardware rocks. Not a fan of their pumps, but everything else, is just awesome, USA-made, and CHEAP!

[na1mt]

http://www.fluidmotorunion.com/wp-co.../rs6_misc3.jpg
http://www.fluidmotorunion.com/wp-co.../rs6_misc4.jpg
http://www.fluidmotorunion.com/wp-co.../rs6_misc5.jpg

I think this it what you were looking for

[ben916]

Stephen, these questions might be better answered by Grizz (unit 20) or MRCtuning as I seem to remember that their foundation was:
2 fuel pumps
Larger fuel rail (2 lines in)
Larger injectors
bigger turbos - which you already have
fuel return line - I don't remember if this fits into their game plan
airbox - you have that covered...
TUNE...

[yokust]

I am not saying that the stock lines may be big enough on our engine setups. But just a thought to throw out there. And a larger liter motor may require more fuel volume.

2.7t guys with gt2871's or tial 770's have made well over 700+ WHP with stock fuel lines and just an 044 intank pump.

4.6 Cobra mustang people push well over that hp with stock fuel lines that are same size as ours

[speedtrapped]

ty yokust...yeah, i spoke w/ vast, unit20, and stratmosphere, they think lean1 side rich the other is mechanical, not tune, and not fueling. I am starting to wonder about turbulance, as the FMu box is just that, arms that feed a common box with 2 outlets underneath, that mate to the MAFs....as mentioned in an another thread, the original set up had the dbr intake as well, i sold mine to josh, as i had already ordered fmu. When the car was tuned and dyno'ed on the maha, it wasnt lean as per dion. i just dont know about the other 4 fmu users, if they have logged and seen a lean/rich result. the box always scred me, because velocity of air meets in a large rectangular box, and the outlets are only 2' long, not enough to smooth the flow out before the maf

[yokust]

If you want to pay for shipping I can send you my extra set of Apikol intake pipes, and would just need a set of 3" filters to try. But do want them back of course.

They are the rough first set made to use for the mold of the 1 pc pipes.

[speedtrapped]

Yokust solid offer and I appreciate that. I have a set of DBR pipes in close possession, will have tomorrow. Tonight hopefully I can get direction on which connectors on the firewall are the primary o2 and reverse them, run some logs...Grizz suggested, lean pass and rich driver....if that's not it, then tomorrow pipe swipe, log...etc etc... I will find the gremlin!

[yokust]

You are not just going to be able to easily switch o2 spots. They are on oppisiste sides of the engine bay, and harness's are not that long

[na1mt]

You are not just going to be able to easily switch o2 spots. They are on oppisiste sides of the engine bay, and harness's are not that long

That's what I thought made sense.

[speedtrapped]

Actually the harness was easy, and I did switch both large 4 prong o2 connectors, go figure...but kid messed with computer, so I can not vAG the lambda tonight....damn!

[yokust]

Not sure really how you did that.

Black four prong on pass side is Bank 1 o2, and Black four prong on drivers side Bank 2 o2 primarys