Fuel pressure?

Neo187H

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.

GambitX

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


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

phunk

^^ 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.

__________________

SAM@GTM

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.

phunk

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.

__________________

SAM@GTM

The 2009+ G's have the newer pump.

phunk

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.

__________________

phunk

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?

__________________

Ron

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?

__________________
2011 Twin Turbo PW nismo #113 - My Journal - My TT Build Thread
[ GTM GTX Stg2 TT || HKS EVC6 || Custom CarPC || F.I 3'' TDX CBE || SB 6puck clutch/ZSpeed CSC || BC BR Coilovers || SPC camber arms || Work VSS-X || Custom Headlights || PW:JDM CF Covers || Seibon CF Engine Cover ]

phunk

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.

__________________

Ron

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

__________________
2011 Twin Turbo PW nismo #113 - My Journal - My TT Build Thread
[ GTM GTX Stg2 TT || HKS EVC6 || Custom CarPC || F.I 3'' TDX CBE || SB 6puck clutch/ZSpeed CSC || BC BR Coilovers || SPC camber arms || Work VSS-X || Custom Headlights || PW:JDM CF Covers || Seibon CF Engine Cover ]

phunk

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.

__________________

Ron

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

__________________
2011 Twin Turbo PW nismo #113 - My Journal - My TT Build Thread
[ GTM GTX Stg2 TT || HKS EVC6 || Custom CarPC || F.I 3'' TDX CBE || SB 6puck clutch/ZSpeed CSC || BC BR Coilovers || SPC camber arms || Work VSS-X || Custom Headlights || PW:JDM CF Covers || Seibon CF Engine Cover ]

SAM@GTM

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

phunk

^^^ 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?

__________________