Fuel pressure?

Neo187H

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?

Zat_Zuma

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.

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.

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GambitX

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

Neo187H

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?

theDreamer

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.

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Neo187H

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.

Jordo!

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.

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phunk

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.

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phunk

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.

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phunk

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.

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Ron

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

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theDreamer

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.

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phunk

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

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phunk

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?

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theDreamer

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: STILLEN 370Z Supercharger System - Announcement!!!

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