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Charles, do you know the fuel line diameter on the 370z? I know the 350z's had a 5/16" line from the fuel pump basket to the fuel rails.

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phunk

The main line is also a 5/16 or metric equivalent in the 370z. There are many places inline the plumbing of much smaller size, and much larger size. This makes it hard to use any type of math to determine flow/drop etc across the *entire* system. But you could surely calculate flow through just the hardpipe itself pretty accurately, just sort of estimate the bends. Just remember to compensate for wall thickness. Hardpipe sizing is always based on the OD.. as the OD of the hardpipe is to match the ID of softlines.

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elperuano

Great info!
My only concern is how much of an issue is this if so many boosted 370s are out there and STILL out there and I can't think of much that have blown motors. There's some over 10k miles and still running. I'm at 6k n have had no problem whatsoever.
Is this really an issue or is it being taken overboard? Losing fuel at the top end would be disastrous and for boosted 370s n g37s to have been running on the road for so long with no fuel issues seems like it's not a real problem at all.

In the end it's still a great build and the attention to detail is very nice.

phunk

Well you have to look at it for what it is. I have a lot more miles than you and have not had a problem either. However, that does not mean my car isn't experiencing any fuel pressure drop.... and to not have a blown motor does not mean I dont have it. If my car has it, then I tuned around it, and I didnt even know. Thats not clean, pro, or consistent... but its my own car and im not trying to sell it to anyone.

Pressure drop, being that it occurs when part of the system is operating at 100%, means its profile can change from the slightest difference in environment.

If your car has pressure drop, and a canned tune youre running was built on a car with pressure drop... well then its going to be pretty close and you might never experience a problem. However, it leaves room for the unfortunate guy who just happens to have the wrong combination of environmental conditions to cause the pressure curve to go rogue enough and cause potential engine damage. An EMS tune on the stock computer has no way of compensating for fuel pressure swing on its own... so it can be tuned around, but if that swing moves at all, the tune is no longer good for that pull.

Thinking back... my A/F in my 370z isnt all that consistent. Some pulls im leaner or richer on top than others. I always just attributed it to the fact that I am a noob with the UpRev, or that I run E85 which is hardly consistent. The fact is that my tune is conservative enough that I have plenty of room for error.

But... on the wrong day and the wrong tank of gas, the variables could overcome the conservative buffer in my tune and BOOM.

Maybe my inconsistencies have more to do with fuel system inadequacy than my tune or selection of fuel. Never checked!

Information is boss.

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TerribleONE

Just to clear things up.. the car is not technically leaning out, you can see that in the AFR on the dyno graph. It is safe to drive and would probably run great as is for a long time however, it is not something you want happening. Im really curious if anyone else has ever installed a fuel pressure gauge

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phunk

^^ exactly. dropping fuel pressure can be tuned around all day for safe A/Fs, so long as the pressure doesnt drop too low for the power and injector size. Its very possible that is the scenario occurring in my car and many other boosted Z's.

Has anyone else actually monitored fuel pressure at the rails above 500whp?

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Mr.Squeeze

Vince@ R/T Tuning did so Charles when I was getting my built motor tuned with your fuel return system 850cc injector's DW 300 pump.My car was dropping fuel pressure over 500whp. I don't remember how much but I ended up leaving my car there to have your twin pump's installed fuel lines and rails installed, I know Vince spoke with you a few times while he was working on my car.

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phunk

You just kicked the problem straight out of the ballpark, which is respectable for sure, and often times cost effective on an individual build basis. R&D for a single car project can be more hassle than just going the route you did and washing your hands of any potential problem areas.

But it will be interesting to see what F.I. may find as to sources of the restrictions. Naturally, a full twin pump with rails kit may be cost prohibitive for many customers. So there should be some value in finding this information.

I have had intentions of building a full custom test bench for this stuff. I need to find an electrical engineer who can help me with a schematic on a custom injector driver with adjustable power source output, realistic firing order/sequence for 4 6 and 8 cylinders, adjustable simulated RPM, and pulsewidth. Anybody? Bueller?

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DEpointfive0

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G37Sam

What my shop did on the G37 was use the factory fuel supply line as the return line, and built a whole new fuel line for my twin pumps. Problem solved

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G37sHKS

I have read in other forums that installing inline fuel pump will help to keep the fuel pressure steady at high PSI of boost,

Why nobody tried that on this car yet?

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phunk

well for one, it would be completely unregulated, because the fuel pressure regulator is in the tank on these cars.

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F.I. Inc.

Update,

This dyno chart shows the comparison from Tuesday night and yesterday. Below are the comparative specs.

Run #13 from 2/19/2013
9.77 psi peak
18 Degrees of timing
91 Octane (pump)
2.5" FI straight test pipe Non Res X Pipe CBE

Run #6 from 2/20/2013
10.20 psi peak
22 degrees of timing
100 octane (pump)
2.5" FI straight test pipe Non Res X Pipe CBE



As stated in previous posts, we are dropping fuel pressure during the run. We currently are running the Aeromotive 340lph fuel pump in tank and have amped the voltage with a relay and thicker gauge wiring. In addition we have drilled out the swirl jet on the bottom of the canister as well as the FPR (Fuel Pressure Regulator). The pressure drops but stabilizes around 42 psi during full throttle in the higher rpm range. This is monitored by a gauge directly mounted to the fuel rail. We are in the process of adapting a secondary gauge to the fuel canister itself to find specifically where the pressure drop is occurring and why. Together with Charles from CJ Motorsports "aka" phunk we will come up with a solution. We are not totally convinced that the only solution is to switch to a return style fuel setup.

Since Uprev does not allow you to monitor fuel pressure in the software nor does this car have an external fuel pressure sensor plug-in anywhere, you are either installing a fuel pressure gauge right off of the fuel rail or bringing one into the car. Like I stated earlier, we feel that most people are not monitoring fuel pressure as long as the car is not running lean during testing on the dyno or street. You can see from our chart above that even though we are dropping fuel pressure we are still able to get the air/fuel ratio at an acceptable level. We are not comfortable turning up the boost anymore with the fuel pressure at 42-44 psi under a run until we can fix the issue. Because the fuel pressure is dropping it is requiring us to add substantially more fuel in the higher rpm range to the table. Every pound of boost added will make the fuel pressure drop lower in the current state that the car is in.

It is possible to run a boosted 370z with dropping fuel pressure for many years and never having an issue. That being said, there is eventually a breaking point where the pressure drop will become an problem. For example, as time goes by fuel pumps degrade, filters start to clog and your fuel pressure will eventually go lower and lower. It only takes your fuel pressure to drop below that breaking point for a split second one time at the right boost level to cause catastrophic engine failure. In addition keep in mind that your fuel pressure is much more erratic beating the car up and down the street than on the dyno. In between gear changes, constant on and off the throttle. At the end of day you are dealing with a fuel system that is mechanically regulated at the tank while fuel atomization is happening 7-8 feet away at the engine. Case in point, by the time the engine runs out of fuel it is too late for the regulator compensate.

In closing, we are getting ready to head back to the track first thing tomorrow morning. We have the car in a safe state and will run the boost around 8 psi and potentially turn it up to 10 psi. We will see how the day goes and keep everyone informed throughout the day and weekend.

Thank you all for your time and stay tuned...

Tony

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TerribleONE

On a lighter note, the new Mickey Thompson ET Street Radials are mounted and we are almost completely ready for the track tomorrow! Just need to load the car in the trailer.

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Dzel

Man that sounds very scary

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