Fuel pressure?
 

I have installed a Stillen SC with a 9 PSI pulley and an upgrade 928 motorsports impeller and now the tuner is saying the car is running out of fuel above 6800-7000 RPMS, does anyone know off the top of their head what the 600cc injectors should be running at in this RPM range? I'm only hitting 440 at the wheels at about 7K when the injectors are at 100% duty cycle, is this normal?

I'm thinking I somehow mesed up the fuel pump install and just don't have enough pressure, is there a way to check fuel pressure on this car?

Fuel pressure gauge

You may have to increase voltage to the fuel pump by way of a relay to supply battery voltage to the fuel pump.

Or go all out and install a fuel pressure return system with the power supply voltage relay.

It's more of a common problem than what most people realize with FI and bigger injectors. A good steady 14 volts to the fuel pump, would go a long way.

In my case, fuel pressure drops to 42 psi @ 7500 RPM. Idle 62 psi. I had a plugged pump suction screen before and only had 24 psi @ 7500 RPM causing a extreme lean condition. :eek:

For the record, I haven't done the power relay yet, but plan on a complete fuel return system, voltage relay, regulator and fuel filter to be located on the outside of fuel tank, where they belong. I don't like the OEM fuel pump/filter/regulator design at all and will be changing it this spring.

did they drill out the fuel pressure regulator in your fuel pump assembly?

page 15 or 16

http://www.gtmotorsports.com/Manuals..._G37_Coupe.pdf

Yes, I did as per Stillen's instructions. My main question really is, is this a normal thing? Are people maxing out the 600cc injectors like this?

I would say something is not right, a lot of guys are running 600cc injectors with that power without hitting 100% load.
I would have them tear down the fuel pump assembly and inspect it for problems.

That is my thought as well, even the GTM stage 2 SC only comes with 650cc injectors and I'm sure GTM has factored in a safety margin for them keeping the DC well below 100%. Though I'm not sure how much of an affect my ARK exhaust and Motordyne ART pipes are having as well, causing raw fuel to be dumped right out the exhaust from the overlap.

Edit: I should say that is my HOPE, I'm hoping it's simple and in the pump rather than requiring replacement of the injectors and removal of the Stillen intake manifold.

You can use this calculator to figure out the right size injectors...

RC Fuel Injection

The 600 cc's may be fine for the stock levels of boost, but maybe not for the upgrade?

Another possiblity: I wonder if your K values for the injectors need to be adjusted?

It could be that you do have more room with the injectors, but if it's all calculated based on the K values, possibly you can go beyond "100%", and everything just needs to be rescaled a bit.

Double check that all the values modeling the physical parts are correct -- after that, it's either injectors or pump.

Enlarging the fuel pressure regulator and swirl jet orifaces in the fuel pump assembly are to increase return side flow to eliminate the fuel pressure spike at idle with a larger fuel pump. When you increase the fuel pump output, the regulator is unable to do its job when the engine is at very low load and idle, causing fuel pressure to spike up until you increase load or RPM.

This modification is only for low engine load/RPM fuel pressure control and will have absolutely no effect on overall output capacity of the pump/assembly. It is unrelated to any pressure drop at the top end... it is only related to maintaining pressure control at idle.

Unless you have added some type of FMU fuel pressure riser setup...... which you may have done, i dont know your setup.

Fuel pressure in a 370z should ALWAYS be the same. It is a static base pressure returnless system.

If your idle is 62psi, that is too high, your regulator is unable to do its job. Normally I would say your fuel pump is too large for your configuration and you need to modify the swirl jet oriface, but if you are down to 42psi at 7500rpm than your fuel pump is unable to keep up with your HP needs.

If you are running just a basic pump upgrade and injectors, than your fuel system is performing poorly all around. You should double check your numbers and contact me I will help you get it right.

This is mostly correct aside from one consideration.

You must keep in mind that TT cars are able to take the same fuel system noticable further. The supercharger systems use a lot of the HP they generate, so a larger fuel system is required to generate the same power to the wheels.

The GTM SC kit uses a supercharger that is supposed to be much more efficient in its losses, so I would expect that GTM will be able to take the same fuel system configuation slightly further than the Stillen/Vortech.



To the OP: Your WHP doesnt sound too far off from where I would expect those injectors to max out with that type of SC, but that depends greatly on the type of the dyno you are measuring on. If you are on a dynojet, I think you should be able to get a little further if your injectors are actually that size.

I will have to look into what Stillen does to the fuel system for their kit to give you better information.

sub'd I wanna know if this is also happening to other FI'ed guys

Phunk, true, I was thinking of RCZ numbers who are about the same and he was not near 100% but with the upgraded propeller and possible for a non-dynojet he might be pushing the kit beyond its limits.

almost 3 years ago I put together this page for people to understand the 370z fuel pump assembly, but it might make a lot more sense to people who are already familiar with how the 350z version works. BTW some of the G37 have the 350z fuel pump assembly and not the 370z fuel pump assembly.

Perhaps today I will go into this page and update it to explain a lot more and with what findings we have had since actually using these fuel pumps after modifications. I can also add details into specifics with the rest of the 370z fuel system so people know exactly what they are doing and why to do it.

cj-motorsports.com

What does the Stillen kit include for fuel system upgrades? Is it just an in-tank walbro and injectors? Or do they use an external inline walbro with a FMU to raise fuel pressure as you boost like the old 350z Vortech kits?

Parts included in the kit:

• Vortech V-3 Series Compressor w/Pre-Assembled Laser-Cut Billet Aluminum Mounting Assembly
• (6) 600CC Fuel Injectors
• ECU Based Tuning Device
• High Output Fuel Pump
• Air-to-Water Intercooler System (Intercooler, Heat Exchanger, Pump, Hoses, Mounting Brackets)
• Polished Aluminum Intake Charge Pipe
• Cast Aluminum Intake Manifold
• Cold Air Intake Y-Pipe w/Draw Through MAF Sensor Bosses (as recommended by NISSAN)
• Genuine K&N Intake Filters

Here is the original thread for the kit: http://www.the370z.com/forced-induct...ouncement.html

Thanks for all of the input guys, I will have the car back tomorrow to go through it and know all the specifics of whats going on.

I don't even know currently what the tuner has the AFR set to, the only thing I really know for certain is he currently has the RPM cutoff set at 6500RPM and it makes 387WHP at that RPM.

ahh that i did not know! thank you for the information :tiphat:


also so my G37 has the 350z version im assuming because its a early 08 model. Which of the fuel pump assembly is better? 350z/g37 or the newer 370z for FI applications with upgraded pumps or is there really none

^^ the 370z and 350z fuel pump assembly, while very different in appearance and construction, have essentially indentical features. I would not say that one is any better than the other. 350z owners have less issues with fuel starvation in high load turns but I think that is more related to the fuel tank dimensions since the fuel pump assemblies are so alike. The tanks are similar overall shapes, but the dimensions are rather different.

I am not sure at this point which G37s use the 350z assembly. I dont know if its related to sedan versus coupe, or build date, or what.

The easiest way I can describe how to tell which assembly a G has is to remove it from the tank and look. The 350z unit has all its passage ways and plumbing molded into the housing, so you cannot clearly see how it is plumbed. The 370z unit has all external plumbing, so you will see black nylon hoses connecting the components within it.

We have been using 600cc/min injectors on all our Stage 1 Supercharger Kits as well as our Turbo Kit without running into any fueling issues. Here are some dyno graphs displaying the AFR with different boost levels. All these graphs are with 600cc/min injectors. Notice the 600whp graph starts to taper up at the end due to maxing out the injectors.

So, if you are running out of fuel, I would definitely perform some of the basic checks to make sure that you have a good fuel pump and base pressure. Also, we use a 255lph Walbro Fuel Pump (GSS-342) in all our kits. To my knowledge, Stillen doesn't use that part number, and I'm not sure what the rating of their pump is...you may want to check with them on that.

Phunk brought up a few good points as well as far as the supercharger's parasitic horsepower loss...especially on the Vortech unit.

We have made over 460whp on our supercharger kit with 600cc/min injectors without issues. However, on our Stage 2 Supercharger Kit, we elected to go with 650cc/min injectors and a fuel pump voltage stabilizer to give us an extra margin of safety.

One final point is that there is a direct relationship between the K multiplier, MAF voltage, and target AFR. Just make sure that whoever is tuning the car is well aware of that.

As you see, we always post our AFR on our dyno results so that there is no question that our tunes are safe and solid.

I started writing a detailed document with photos describing the 370z fuel system, which will also apply to the G37 with the only variation being the ones with the 350z fuel pump assembly, which I will add a brief description of the "need-to-knows" for as well.

I will post a link either tonight or tomorrow to this document.

The 2009+ G's have the newer pump.

Sam: Do you know the specifics as to which G37's use 350z fuel pumps and which use 370z fuel pumps?

To be honest, for all I know, all G37 may have the 350z sending unit.

EDIT; just saw your post, thanks.

Another curiousity I have into the fuel pump assemblies...

The 370z sending unit is several inches taller than the 350z sending unit. The G37s with a 350z fuel pump assembly must either have a modified version of it that is taller, or the G37s with the 370z fuel pump assembly must have a modified version of it that is shorter? Both the assemblies are self adjusting in height by compressing against the floor of the fuel tank, but I am not sure that the range of travel is enough to compensate for the height difference between the Z33 vs Z34 assemblies.

Any insight on that, Sam?

Sam or Phunk.. what do you think about a fuel return system for FI.. most people here don't get them with their kits. But owners of other platforms consider it a necessity when going FI for stable/adjustable pressure. What are your thoughts on this?

With the 350z, a return fuel system serves more purpose than in a 370z.

Return fuel systems with the 350z come in a few variations. There are entry level systems that are simply a conversion to return fuel, but do not improve flow on any of the feed plumbing.

There are only 2 reasons to convert to a return system of this style with the 350z/G35, and they do not have the same value in a 370z/G37.

1: Adjustable fuel pressure. Using an external regulator allows you to control exactly what your fuel pressure is. Not everyone needs this, but some people want it. When tuning cars with full standalones using speed density based fuel injection, or using piggy backs that add compensation fuel with their own speed density system (MAP addon), you can run into inconsistencies in the tune as environmental conditions change. In a full standalone this is technically avoidable within all the available correction parameters, but it can be difficuilt to dial those corrections in perfectly, especially when you are tuning the car under one specific set of conditions. You can only make educated assumptions how environmental conditions will change it. So to be able to adjust your pressure can, while not the most ideal, offer you a way to make a quick painless adjustment that will alter your end A/F ratios without having to get into the laptop. You would only do this for very minor adjustments, such as 1-2psi +/-. This is much less relevent in cars tuned 100% on MAF style fuel injection systems, which is what everyone is doing with the 370z (via UpRev reflash). The air metered through the MAF sensors is accurately and consistently precisely the volume of the air entering the engine with environmental conditions included. So unless you have come up with a specific reason that you need to change the fuel pressure, you arent really ever going to need to.

2: Vacuum referenced regulator. External regulators have the option to hook up a vacuum line. Using the vacuum reading, the regulator will add or remove fuel pressure in direct relation to manifold vacuum/pressure. This means at idle vacuum, the fuel pressure is lower. This also means that under boost, the fuel pressure is higher. This can make it easier to tune out larger injectors for idle, while still maintaining their potential on the top end under boost. However, this function is entirely irrelevent in the 370z due to the VVEL system choosing its own target manifold vacuum/pressure without direct correlation to engine load. This would make it an endless tuning nightmare as you will find your fuel pressure changing with no consistency outside when you are boosting. So you could not hook up the vacuum line to the regulator on the VVEL engine.

What all this means for the 370z; the advantages of simply performing a return fuel system conversion are entirely irrelevent. There is no advantage to altering the fuel system outside of pump or injectors, until the plumbing inbetween these points has become a restriction or starts to cause individual cylinder tuning grief as fuel will eventually bias cylinders when you start to push the plumbing too far.

The stock fuel system in the 370z has proven to flow more than adequately for any amount of power you are safe to generate on a stock engine. As a matter of fact, in my own car, I am using E85, which requires significantly more fuel quantity to acheive the same power... and I am still on stock plumbing.

I do not think anyone will have to worry about playing with the fuel system in this car (aside from pump upgrades and injectors) until they are at the point of requireing a second fuel pump.

Thank you phunk, very interesting. I guess E85 setup requiring more fuel for the same amount of power is why you went with larger injectors than the ones on the GTM kit

When I selected the 1000cc injectors for my car, I had not planned on E85. I just knew that at some point down the road my car will need them after I build a stronger bottom end for it. As an experienced tuner with standalone systems, I was confident I could tune my car to run them just as well as a smaller injector for start/idle/cruise and all conditions.

Well, tuning the UpRev has a bit of a learning curve, regardless of experience with other EMS. Matter of fact, experience with other EMS probably made it worse because I kept looking for things that are not there or not needed with this style of engine management. I also tend to require a certain level of understanding with what exactly I am working with before I will try and work with it. At any rate, tuning the UpRev with 1000cc injectors (with gasoline) was a little over my head as a first time project with that software. I was having a lot of trouble getting the car to run well in all conditions. I could make it start and idle, but then it drove like crap. I could make it drive great, but then it wouldnt idle. Etc.

So I decided I would make my life easier, preserve my engine, and learn on a more typical configuration. I elected to switch to E85 to, in essense, water down my injector size. Tuning E85 with the 1000cc is more like tuning gasline with 700cc or so. It worked great and the car performs great. I would like to think that should I decide to switch my car back to gasoline, with what I have learned with the UpRev software, that I could take on the task now. But, theres only one way to find out.

Ok I wasn't that far off then. Thanks for the info again! Sorry Neo if I jacked your thread a bit. We can get back on topic now :D

It really depends on the horsepower levels. For anything up to 550whp, you can get away without installing a return fuel system no problem. A few reasons for this are:

1) simpler is better and more reliable. Not having a rising rate fuel pressure regulator, fewer lines will minimize leaks, vacuum lines popping off, etc.

2) The other main reason is that when Nissan develops an ECU map for these cars, they have gone through serious amount of testing and development of all aspects of this engine and its characteristics as far as air flow and individual cylinder VE. For example, if you take a look at the engine management for a well developed platform (Subaru, Evo), you will see that there are many fuel maps that are designed and put in place based on that particular engine. So you will see a low fuel det map (engine is happy and ignition advance multiplexor at it's peak), and you will see a high det fuel map (richer map) that will have more fuel for knock detection condition. Also, you will see that there will be 4 individual cylinder fuel maps that are all different since there is no way that the OEM intake can supply the same amount of air to each cylinder. So you see, all this technology is already in the factory ECU mapping and fuel curves. The minute you add your return fuel system which will change the fuel curve and is not based on load and MAF voltage, you just threw all that out the window. Of course in some cases you will have to do that. Take for example our White Dragon project. Once we installed a return fuel system, we also installed 6 EGT sensors (one for each exhaust runner), dual Knock device to monitor both banks, so we can make sure that we're not overfueling or underfueling any individual cylinder. That's what it really takes once you are no longer relying on the back end of the ECU to do the work for you.

Sam

^^^ and the white dragon is using a twin fuel pump assembly. in this circumstance its a requirement. An external regulator is required. The stock regulator is a part of the stock fuel pump assembly. With the twin assembly, its gone. And we didnt make a way to include it in the twin pump because it would be too small to handle twin fuel pumps unless you were to stage the pumps (activate the second pump only at high load).

Sam, youre not using a vacuum line on the regulator on that car are you?

:tup: Sam, can you pm or email me info on what you are using to monitor knock? I sent you an email on that, specifically about the J&S Safeguard. Thank you Sam and phunk. I think this thread has turned into a VERY informative one.

Ron, you should scan through the UpRev website. They have on there detailed information to building a dual channel knock amplifier so that you can build a little circuit that allows you to plug in headphones and listen to the knock sensors with one sensor per ear. I bought all the components but I havent put it together yet... not much to listen to with E85 from what I hear.

Of course it is...we're using a rising fuel pressure regulator, which has made it a ************ to tune. Keep in mind that the VVEL vacuum variation has a negligible affect on fuel pressure under vacuum, since the difference is only a few psi between low vacuum and high vacuum. Once you're in boost, that is no longer a concern and the rising rate fuel pressure regulator does what it needs to do.

BTW, your Twin Pump setup is doing its job very well.

Sam

^^^^ http://uprev.com/documentation/Knock...n%20Device.pdf

Yes under boost it will surely work consistently. But its the low load cruising that made me decide not to follow through with building external regulator 1:1 ratio based fuel system kits for these cars.

What about under this circumstance as an example. And yes, I understand closed loop fueling SHOULD be able to handle this situation, but it still feels improper to me.

Say you are cruising down the tollway, and the VVEL is maintaining a 0/0 vacuum environment in the intake manifold. If you simply tap on the brake but do not lift throttle. The system instantly switches to throttle control and generates vacuum to operate the brake booster. But instead of holding on the brake, it was just a mere tap (for whatever reason). Now I know this test circumstance is more like searching for a inherent flaw than it is an actual driving condition... But, we have now created a situation where we have gone from no vacuum to engine load specific vacuum. The fuel pressure will instally drop due to vacuum, and then within a few moments it switches back to VVEL load control and fuel pressure will raise.

Like I said, I know thats a strange set of conditions and not very likely to occur in regular driving... but that set of circumstances alone was what told me that I cannot depend on the VVEL system to give me a consistent connection between actual engine load and manifold vacuum. I stopped trying to theorize other conditions where this could occur... but I certain there has to be some others.

But if the car seems to drive and cruise without issue regardless, then I suppose my concerns are exaggerated for the situation.

That is good news. I figured it should work out as its based on the 350z twin design.

Build more crazy cars! I have a handful of those twin pumps with your name on them!!

Awesome information in here guys, I'm glad this has turned into such a discussion. Despite the fact that I'm now more confused than when I began :icon17:.

My tuner is an experienced tuner, mainly with Hondas, but they have no experience at all tuning Nissans or Uprev at all. They have been on the phone with Uprev throughout the day so I'm ASSUMING that they have stuff like the K factor (not that I have any idea what it is:icon17:) covered but I'll talk to them further tomorrow.

Would stuff like the K factor affect the cars running throughout the entire RPM range? It currently runs great on the dyno up until the point where it starts to lean out up top.

A rather basic question but, what should the target AFR be? Years of fixing cars and I'm totally incompetent on the tuning side of things.

The K multiplier is a constant value that models injector size and pulsewidth -- it affects injector ontime throughout the tune. To the best of my knowledge, the value typically needs to be chaged if you change injectors.

Target AFR is whatever makes best power with no evidence of detonation, and varies from engine to engine. Something on the rich side, most likely, as the extra fueling (i.e., running a mixture higher than stoich) is used to cool in-cylinder temps. Probably something around 11 - 12, but could be a bit richer (or leaner) depending on load, octane, ignition advance, CR, boost pressure, etc, etc.

If your guys have good general knowledge with tuning FI'd cars, they should be able to figure it out, at least to dial in a basic tune. Eventually somebody who has more experience with uprev and with this engine should be tracked down for fine tuning if possible.

The guys with more experience using uprev in particular and on tuning this motor in particular can probably give you more specific info...

To bump a now old thread, I now have larger 725cc injectors as well as a 300lph pump installed in the car and I'm still running into this same lean issue above 7000RPM.

Any thoughts or ideas?

I know the tuner is currently reading over this specific thread so I'm hoping maybe someone knows something thats way above my head that will give them some insight.

Sounds like the MAF values or the K fuel Multiplier is way off. You need to have a happy medium of the two. If one is way out and you try and compensate with the other it will throw BFS way out. Also a F/I 370z is a tricky car to learn UPREV on. Probaly the hardest actually. PM me if interested in maybe some E Tuning or coming down here...