Still working on paying my Nismo off but you definitely have my attention. The 370Z has always seemed to be $100/hp car to mod and the kits always looked so ugly to me that I figured why pay so much to destroy the aesthetics of the car for and for so few HP. This setup is very clean and it appears to change the nature of the power band in a very positive way at low boost. The curve is just so flat, it's what the car is missing. Well done!

Believe it's rod failure, not sure of the tq limit though.

I don't get the fuel problem.... Why has no one else had this problem ? And what fuel pressure gauge do you have ?

I will elaborate later once I have a chance to sit down and explain it in detail. I can promise you that anyone at this power level with a stock style return less fuel system is having this problem. If I was a betting man, I would bet most people are not watching their fuel pressure. 99% of the time all that is watched is the air/fuel.

Thanks, Tony

What kind of gauge you using or how you monitoring it?

From the research I have done it seems like almost EVERYONE is running into problems like this at this power level, they just may not be aware of it. To the best of my knowledge, up until this point no one makes a return-less fuel system that can handle this power level, we are going to try a few things and hope to make the impossible, possible! Also, while talking with Sebastian today he explained that even if you have a air/fuel gauge, by the time that starts to read lean, it is already too late. I will definitely be running a fuel pressure gauge in the center cubby as it is a small price to pay for the added protection.

It is a liquid filled XRP gauge, attached directly to the fuel rail.

I have no problem with fuel at 540hp. Not sure why u would think every boosted ride has this problem yet doesn't know it??? And about the gauges, well that kind of defeats the purpose of even having them in the first place. If calibrated correctly they should work just fine. I datalog thru uprev and lookin at the gauge it's fine. 6k miles n runnin strong

You data log what through UpRev? (Fuel Pressure) or Air/Fuel ratio? We are not having a problem with air/fuel, we are dropping fuel pressure. The reason I said most people do not know if fuel pressure is dropping is due to the fact that you cannot monitor fuel pressure through the UpRev software. That being said, please elaborate. How is your fuel system setup? Any feedback will be greatly appreciated.

Thank you, Tony

Yes, air/fuel is what I meant. I'm not running lean at all at any spots on my band so there's not a problem with the fuel pressure. If I was losing pressure I'm sure I'd be running lean at spots and I haven't seen any. I know of only 2-3 people I believe that had to upgrade the fuel system but they are built motors.

Tony, what size is the fuel pump? I know that the 255lph fuel pumps will run out of steam at 500-550whp (with boosted VQ's). This is why I switched to the 340lph fuel pumps and larger (than normal) fuel injectors.

Dyno sheet is looking good too, keep up the good work.

Yep. Something not a lot of people realize or think of.

Thanks,
Alex Goodwin
AlexG@motionlabtuning.com

Restrictions in fuel system plumbing will cause a pressure drop between the fuel pump and the injectors. Every car will experience this to some degree. The amount of pressure drop between the pump and the injectors will be awfully dynamic and impossible to determine off hand.. you have to do individual testing per application.

At engine idle, or lower power needs such as cruising, there is less fuel flowing through the lines, and the pressure drop will be less. As power climbs, fuel flowing through plumbing in the vehicles starts to increase, and each and every restriction in the fuel system will start to manifest into a sum of pressure drop.

The 370z, in factory configuration, regulates fuel pressure off the side of the fuel filter housing, inside the fuel tank, immediately inline after the fuel pump. What this means, is that the pressure regulating system is regulating pressure at the fuel filter. Before any of the substantial drops in pressure on the way to the engine bay.

If you converted to a return system, you will now be regulating pressure in the engine bay. So instead of seeing pressure drop between the filter housing and the rails, you will see steady pressure at the rails, and pressure increased at the filter housing, to compensate for such the inline drops.

At what quantity of fuel does pressure drop begin in a stock 370z fuel system? There is only one way to find out. Place a fuel pressure gauge off the rails, and place a fuel pressure gauge off the fuel pump. Nobody has done this yet. But only by doing this will someone have completed the R&D to give accurate estimates to how much the 370z fuel system can push, before pressure drop is imminent.

This final number can only be accurately described as a measurement of volume, not HP. However, it would require too much additional R&D to translate this number to a volume of fuel, and then that information would be worthless to the consumer who would be unable to translate that back to a HP figure they can relate to. Injector spray quality, fuel temperature will somewhat effect how much HP you can say the factory plumbing is good for before pressure drop. Tuning and fuel type will *drastically* effect this number. As a couple degrees of timing can go plus or minus 25 HP without changing fuel requirements.

Simply because one persons 370z is not flowing enough fuel yet to show a pressure drop between the pump and rails (or so they do not believe, depending on what evidence they have to support this claim) does not mean other cars will not. To make such direct comparisons would be unwise. Example... I have an A/F gauge in my 370z. I have a fuel pressure gauge in the ENGINE BAY... nearly worthless. My car is making similar power to the test vehicle in questions here. Now, I dont THINK my car is dropping pressure... but how do I know? I dont. My A/F is good to redline... but I have 1000cc injectors and my pressure would have to drop quite a bit to not get the quantity of fuel I need. My pressure gauge, being in the engine bay, only allows me to make sure my pressure is correct at idle. For all I know, my pressure might be dropping by 20psi by redline. :shrug: I never had a reason to look! If this test car in question here didnt have an in-car pressure gauge, who knows if they would have even known.

As you reach the maximum output of just about anything in this world, you find that every tiny little detail begins to have massive effects on where the precise maximum is. This is why automotive manufacturers always build their cars to operate systems at much less than 100%. 100% is not reliable, and it is extremely distant from CONSISTENT.

I think that it is great that they are watching the details on this build. While I do not worry about my car blowing up, and I dont worry about their car blowing up... its a very different game when the car is in possession of experienced tuners. They can make sure its not going to break even when pushing it to the limit. BUT, they want to put together a high quality turbo system for the consumer, and some versions of that kit are going to include a tune I would assume. This means they need to watch and log everything within reason to make sure that the tune they build is going to behave the same on their customer's installations.

There are 2 options for working around a fuel pressure drop in the system in a scenario such as this, and you can optionally take both steps.

Option 1, increase the plumbing size to reduce pressure drops. This can get expensive depending on how far you take it... because a duration of the conservative sized plumbing is physically built into the inlets of the factory fuel rails. The fuel rails themselves are massive and do not need upgraded... however to cut off the ends and weld on different inlets isnt an option for customers who need bolt on solutions, and welding fuel rails is often prone to pinhole leaks. It just makes more sense to move to billet fuel rails so that its simple to add larger plumbing. Well, this gets expensive now.

Option 2: convert to a return fuel system. For one simple reason, to regulate fuel pressure as close as you can to the rails. How does this help you may ask?

Lets say you have a walbro 255, and you are running out of fuel on top. You might say to yourself... oh, I am running out of pump, so i need to put in a larger pump so that pressure doesnt drop anymore. Well, thats old school thinking... thats what it USED to mean when cars had return lines and regulators in the engine bay.

Because pressure drop. While you might be losing pressure in the engine bay with your 255... you might NOT be losing pressure all the way back up the pump. If you arent, then upgrading the pump isnt going to do a dang thing, because the regulator is still going to be holding open at the same pressure in the back. BUT... if your regulator is in the engine bay, and you still have a pressure drop... a larger pump can actually fight the restrictions by flowing greater at higher pressure. Your regulator in the engine bay can hold pressure where its supposed to, and you just let pressure skyrocket at the pump to keep up, compensating fuel pressure drop across the lines.

Basically all I am saying here, is that nobody can argue unless they have *more than one* fuel pressure gauge in their 370z. You might be surprised if you knew how much fuel pressure can drop from one end of a fuel rail to the other, let alone across an entire car.

Yep what he said:ugh2:

:iagree: i knew all this too. :icon14:

LOL I kept it short too :) Which may backfire if any engineers read that and become displeased with the way I chose to simplify some things.

So what can one do to fix this issue?

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.

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.

I cannot speak for them... but the appropriate weapon in such a battle is information.

They will have to do a little more testing before the culprit can be precisely located. You wouldn't want to just throw parts at it... that is no way to go about it when trying to make an engineered and cost effective retail product. They need to know exactly where the source of concern is, so that it can be dealt with accordingly.

With more information they can determine exactly what combinations of fuel system upgrades will be included or recommended with the incremental stages of their kits.

:iagree: I was thinking the EXACT same thing!:rolleyes:

We are using a 340lph or something in this range and larger injectors than the traditional 600cc. On behalf on everyone from F.I, thank you! :tup:

This is exactly the way we are approaching the issue!

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.

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.

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

^^ 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?

Funny guys ... U didn't know chit !!

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.

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?

:wtf2:

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 :)

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?

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

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.

http://i50.tinypic.com/2iayg5v.jpg

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

http://i371.photobucket.com/albums/o...psbf24fdfa.jpg

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

Man that sounds very scary

Time to install a circulating fuel system....


ps; where are you getting 100 octane pump fuel???