zland

I have read that ATI SC kit has a fuel pump that boost fuel pressure to stock injectors. I am interested to know if this will effect the durability of the injectors/can they handle that? Is this a good approach? Maybe you guys with a lot of FI experience can add your knowledge?

If it will effect the durability, how quickly would they get ruined. I am wondering about unforseen costs to this mod.

Thanks, Jeff

jran76

iTrader: (1)

The sttock injectors are 300cc/min, which people have previously stated that is good for about 350 crank HP.

Obviously the procharger kit (or any FI kit) will exceed the 350 HP mark. I am not sure how much damage it would do to the injectors (although it is not great), but the fact that the injectors cannot supply enough fuel to the engine would be of more concern (lean mix?).

I know I did not answer your question, truth is I don't know the full answer, but it does seem harmfull to the engine....Nismo injectors should be available, PE has some available now, as does RC (although I have heard that RC injectors are not all that great vs. Nismo).

GaryK

Injectors are rated with a max flow rate at a given pressure. Changes in the pressure mean changes in the flow rate. This is how the fuel volume is increased using an FMU such as the one in the ATI kit. I don't know if this will hurt the injectors or not.

FYI, after I do the initial install with my kit, it will get dyno tuned at a lower FMU ratio with a computer reflash. Should be easier on the injectors and make it more driveable as well.

zland

Thanks thus far. I hope others can add to this thread. If I do have to go bigger injectors as stated, what will it cost approximately?

GaryK: If you cut the flow rate of fuel aren't you then reducing hp or running too lean?

Are there any tuners out there that know the answer to this one? Paul, at Avalon, maybe you know? Anyone else?

Jeff

jesseenglish

I've considered tuning the FMU with larger injectors. The only problem that i can see arising is at no boost your engine would be running pretty rich. Any thoughts?

GaryK

Ok, I'll try to answer some questions based on what I know, and without writing a book here.

In general, you have to add fuel as you add boost. By pressurizing the air, you shove a larger volume of air into the cylinder on each stroke. To go with that extra air, you need a larger fuel volume. This is what the FMU does. For every pound of boost, it adds some amount of fuel pressure in order to get more fuel into the mixture. The advantage to this method is that you don't have to worry about whether the ECU understands what boost is and what to do as a result.

Now, I don't know a lot about the 350z ECU, but I think it could work by using larger injectors and tuning it accordingly. The question is how well can the Mass Airflow Meter measure the air entering the intake. Regardless of the answer, it will probably be tricky to tune it this way.

For now, the plan is to tune mine on the dyno using a combination of ECU reprogramming and a lower FMU ratio. This means the FMU will be adding less fuel pressure per pound of boost, but the ECU will be running the injectors at a higher duty cycle (open longer) to make up for it under load. So to answer your question Jeff, about cutting the fuel flow rate...the overall fuel added will be approximately the same so we're not really cutting the fuel. As far as how it runs without boost, it should not be a problem because the MAF will show that air flow is low and adjust fuel accordingly. In addition to all this, ignition curves can be altered to make the whole application more "boost friendly". The tuning will be done by the shop through which I'm buying my kit (Altered Atmosphere). Later on, we will likely retune with larger injectors and no FMU at the same time as some other possible upgrades.

Apexi350z

iTrader: (3)

It's also possible to use Apexi SAFC-II with larger injectors to control our fuel output.. but don't know if they have English manuals yet...

zland

GaryK:

Do you see the advantage of tuning with larger injectors a performance gain or simply less stress compare to using stock injectors?

Would larger injectors automatically mean less mpg or running to rich? It seems by your explanation the answer is no.

Can i conclude that if larger injectors are put in, tuning the ECU is required?

Jeff

GaryK

Technically, as long as you get the optimum air/fuel ratio, it doesn't matter how you achieved it. So no, larger injectors aren't really a performance gain if you can tune to the optimum air/fuel ratio with the FMU...and that's a big if. I don't have experience with FMU's so I'm making an assumption here, but I expect that the tune with the FMU will be "rough". That is, it isn't going to be possible to get the ratio perfect throughout the range of boost with just the FMU. Considering this, larger injectors with an ECU reprogram could end up with a little more horsepower.

I see the larger injector option first as a more reliable method to achieve the end goal. By taking the FMU out of the picture, there's one less mechanical thing to go wrong. The other advantages to larger injectors and ECU programming are possibly better driveability and more potential to run higher boost.

Larger injectors, with a proper tune, will not cause an excessively rich condition or less mpg. If you just put larger injectors in without tuning the car accordingly, the engine will run very rich while cruising and decrease mpg. Even when tuned properly, no matter how its done, fuel consumption under heavy load will increase because it has to as a funciton of making more hp.

So when installing larger injectors, it is necessary to do something so that the proper amount of fuel is used under various conditions. In most cases the ECU is programmed to account for the change. In fact, a lot of ECUs have a setting that represents injector size, and changing this is usually the first step in the fuel tuning process I think. There are other methods for dealing with injector changes, such as modified MAF meters, but I don't know if that is an option for this car.

Loren04G35

...and having your car run right, its not. A fuel controller only changes the sensor inputs, you still have to deal with the same maps in the ECU. The first problem you will have is idleing. The ECU has no idea that bigger injectors are in the vehicle. There is actually very little adjustment in the map to reduce the injector pulse width. It will read the O2 sensors and try to lean the mixture. But once it hits the minimum pulse width and the car is still rich, the ECU will think something is wrong with the emissions system and issue an MIL code. Once you reach the end of the map, that's it. You will get the same thing under partial throttle. At WOT, the car runs completely off engine sensors and the maps without looking at the O2 sensors. There is a good amount of adjustability under WOT, but also keep in mind that using a device like this to change the MAF values doesn't only effect fuel. It effects timing too! I you start leaning out the fuel mixture at WOT to compensate for the injectors, it starts advancing timing. This is very bad when your ramping up boost. If it detonates, then kiss your engine goodbye.

This is why whenever 300ZX-TT's upgrade to 555 injectors, they did it with an ECU upgrade. JWT notiriously sets their ECUs rich for safety, but a fuel controller like an AFC does a great job tuning it out. They also work great when adding shanges like cams where the computer has no idea of how to work with them. With the Wolf cams, you richen the bottom end and lean out back on top.

As to the original question, no the additional fuel pressure will not hurt your injectors. You will find that the lines will fail before the injectors do. Sure they can get clogged and fail from imperfections in gas getting into them, but all they are is just a valve that opens and closes for a certain amount of time. With greater pressure, they still open for the same amount of time. They just push more fuel in for the same time. As a functional limit, I would be questionable if the peak fuel pressure was over 65 psi and worried at 80 psi. At 80 psi, the standard pressure fittings on the lines will leak. Keep in mind that increasing fuel pressure with power adders is very old and proven technology. Every aftermarket supercharger manufacturer makes systems with and most turbo kits come with a fuel upgrade of this type. This is a reliable way to fix the fuel problem, but not the best way. The best way is to use larger injectors with a properly programmed ECU that has the correct fuel and timing maps.

zland

Ok, I am learning. Does anyone know what the ATI SC kit is boosting the fuel pressure to? I do not know what PSI it is...

Jeff

VQ35DES

The Greddy R&D used 440cc RC Engineering injectors designed to fit the OE intake manifold. So at 7psi compared to the 5.6psi from Greddy, what should be used.

jhn

You shouldn't have to worry about your stock injectors. The ATI kit comes with an additional injector to supply that little extra fuel needed for the added HP. There's also two kits , one comes with an fuel regulator.

SlamMan

I have a 99 Civic Si with the greddy turbo kit. I am running the RC 440 injectors and Apexi Vafc. I push up to 8psi of boost on this setup. Basically the fuel is leaned way out on the afc and this allows your car to run off the stock fuel map and trick your car into reading boost. I know it sounds kinda crude but it works great.

jesseenglish

jhn,

I believe you're thinking of the stillen kit. The ATI does not come with an additional injector.

TheSVTKid

That depends on if you are using FP, or duty cycle to aid in adding the fuel. Greddy might be using duty cycle alone by the aid of computer programing. Vs. ATI's method of fuel pressure, to add fuel. I am not sure how Greddy does it, but that was a guess based on the emanage they will be including when the kit comes out.

On a side note, just because the cc rating of an injector is larger, the physical size does not change. So by nature there are many "sizes" that would fit the OE intake.

The injectors are able to take the pressure, even for long periods. But since you will only have the elevated psi, durring high boost loads. That will make it even easier on them. Unless you drive 100% all the time with the car under boost and load? Poor little Z

Hope this helps.
EA

VQ35DES

can anyone list everything that comes with the ATI PRO chager kit?

jesseenglish

Damn double post

jesseenglish

C2 Supercharger head unit
3 core air to air Intercooler
High flow fuel pump
Returnless Electronic Fuel Management Unit
Associated Piping
Brackets
belts and pulleys
Air Filter
Bypass Valve

That's pretty much all there is to a supercharger setup.

Loren04G35

One big point is that you are oranges from apples. A Civic is a speed density car. It runs only off a single MAP sensor. There is no MAF. Your ignition is completely independent of your fuel system. You also have a simpler ignition system with a distributer and remote coil. You can change your timing by simply turning the distributer and you can easily put an aftermarket ignition with a retard on it. The engine management is simply completely different. VQs are much more modern engines with timing controlled completely by the ECU through sensor maps and direct firing with a coil-on-plug ignition. There is not only no distributer, the crank angle sensors(there are 3 of them) aren't even adjustable. Your ignition system is completely mechanical and with the VQ there is no mechanical connection at all. For our engines there is nothing other than the signal from the ECU to fire a plug. There is no vacuum or electrical advance. Try doing what you are doing on your civic on a Supra without a VPC(speed density conversion) or a 300ZX and see what happens. The same goes for the VQ's. What works on Hondas does not necessarily work for the rest of the world.