maxlinegtr

iTrader: (3)

To the most of u who put in the 370cc injectors...What set up do u have in fuel delivery? fuel pump...Regulators ...ECU..and such. Can I use the 370cc with just stock fuel set up plus the walbro pump? When i did the motor swap the injectors were puttin out way too much fuel...i am just trying to figure out if the injectors are in good condition. I will mostly send them to RC for flow test.
thanx
Tay

midnightmax01

there are three things that affect actual fuel delivery........fuel pressure, size of injector, and injector duty cycle. if you put a larger injector in the car without changing anything else you will have cold start issues. most people run some sort of air fuel controller, a walboro 255 lph fuel pump, and sometimes even a boost dependent fmu, also an adjustable fuel pressure regulator. to control all of these areas so that they have the largest range of adjustment for tuning.

midnightmax01

most people go with a jw ecu because he can program it to accept the larger injectors.

maxlinegtr

iTrader: (3)

So for now I should not install the 370cc injectors with out an AFPR or an ECU program? I thought it would be "okay" to have it in without starting issues. anyone know of a site to check for one?
thanx

slimer

iTrader: (13)

send then to witchhunter instead. they are half the price of rc, and he puts all new o-rings and pintle caps on there for you, free of charge.

you do need an afpr to adjust base fp for the 370's unless you are planning on using a z32 or j30 maf in its place.

midnightmax01

i thought that he would need the ecu reprogram in order to run the z32 maf. the ecu just uses maf voltage when its in open loop which would mean if you put larger injectors on the car but kept the same fuel pressure, the ecu uses a "look up chart" to determine how much fuel it needs per amount of air (measured by the maf) during open loop. if you use larger injectors the ecm has no way to compensate until it gets input from the o2 sensor. this is why we talk about "cold start issues". some people have been able to compensate for this by using a boost dependant fmu, lower fuel pressure at idle but they still have the fuel pressure they need during boost. so to answer your question, no its probably not a good idea to just throw some injectors on there, until you have a way to manage them.

crewchief264

I just recently learned that while running a fuel psi regulator to try and compenate for the larger injectors works it has problems. Reason being is that the factory sets the fuel rail up to flow at a certain harmonic and that harmonic is effected by pressure. So by putting a fuel psi regulator on and turning the base psi down the harmonic is effected and you may be running one cylinder richer or leaner than another one. The best way to adjust for your new injectors is an ECU Reflash. Second best is a piggy back like emanage.

midnightmax01

just a quesiton to you crewchief, would this not be because of the fact that when one injector opens it drops the pressure before the other injectors....wow that was confusing hopefully you inderstand what im trying to say though.....like since the injectors fire of sequentially, one injector would open before the others on the same fuel rail and might only drop the pressure to the other one (or two on the rail) while still maintaining set fuel pressure to the first injector or the injector with the most time in between opening. please explain what you mean by harmonic. i think i might be a little confused. yet still i agree with you when you say that he sould not put them on there unless he has some way to manage the larger injectors.

Brad92SE

iTrader: (9)

Going along with what Steve said, the SR20 guys run a z32 MAF with those injectors and do not need any ECU tuning. At least thats the way I understand it. The physically larger MAF size "tricks" the stock ecu, so basically everything balances out and the car will run. If it works for them I don't see why it wouldnt work for us. An adjustable fpr would definately be a very good idea though.

crewchief264

My understanding is that there is a certain Harmonic(a wave as in what you might see on a scope) inside the fuel rail. Well my understanding is that the factory sets this harmonic up to be a certain wave length and height if this changes it can cause the injector to flow less or more fuel. the only way to know if this harmonic is to use a Scope. So messing with the psi can have adverse affects on drivability whereas adjusting the injectors via an ecu or emanage is much safer and better for drivability, cold start, idling etc...

I30tMikeD

iTrader: (8)

You can not just put a z32 MAF in without some other management system. The voltage curves between a 4th gen MAF or a stock 240 MAF are not the same as a z32 MAF. The higher the rpm's the more the curves differ. There has to be at least an SAFC involved to make it work right since it has the feature of Z32 MAF in and A32 MAF out.

From Fresh alloy, a post by Enthalpy the premier SR ECU tuner

Ok heres the deal:

Stock Z32 MAF = 530 WHP
Stock SR MAF = 260 WHP

so the Z-32 MAFS can flow 2.04 times as much air as the stock maf. this is great for High HP cars. so IN THEORY say your car is cruising down the road and you are making 50 hp under a light acceleration. Now airflow meters are not a linear response but have more of a exponential response. but for this example we will assume a linear response to make things easier...when you get into the exponential response you need to include a conversion function that is beyond the scope of this response...and in the end makes no difference in the final answer (thanks regis)...

So where were we? oh yeah 50 Hp...so by the conversion factor and assumed linear response above the SR maf would read .96 volts and the Z32 would read .47 volts. Now for your car to run correctly using the Z-32 and stock injectors the ECU needs to be seeing .96 volts. the S-AFC knows the response multiplier and multiplies the incoming MAF voltage (.47 from the Z-32) by 2.04 and sends out a .96 volt output to the ECU....and you drive down the road with no problem.


then you lay into full power...say for this example your car has 300 Hp capacity with it's ncie s-15 BB turbo, but stock injectors (good to 270ish WHP) you lay into it and at 260 Hp the stock MAF would max out (5.0 V) and this is what the ECU would need to see to make the car run right. the Z-32 would now be outputting 2.45 volts into the S-AFC. it multiplies by 2.04 and you get 5.0 Volts and your car shuts down. The ECU sees anything greater than 5.0V as a fault and shuts the system down until proper voltages are seen (maybe a grace window to 5.12V as stated earlier). So how did i run 380 HP on a S-AFC and a stock ECU??

Injector correction!!

so being smart and realizing you have 300 Hp on tap but only 270HP worth of injector you go out and buy new injectors. A bright Yellow new set of new Tomei 555cc Side feeds...life is good! you go back and do the calculation for baseline correction for the injectors.

(370/555) - 1 = correction factor = -33%

so you go in and set all your high and low throttle settings to -33%. and you go drive your car!! now in the real world the settign once tuned on a wideband would be much different due to ECU mapping...on my car with the described setup there were places where i was runnign -45% correction to get a desired 12.0:1 AFR...but that is irrelevant for a 300 HP car such as this example!!

so back on the highway light acceleration 50 Hp...for the car to run properly the injectors need to see 2/3 of the on time of the stock 370's at this power, and thus 2/3 of the expected original MAF voltage....if you dont understand this i can clarify in another post. so you would usually have .96v coming in...but were on the Z-32 so we have .47. the S-afc performs the airflow conversion of 2.04 and you have .96V. next the S-afc performs the programmed correction factor of -33% that you entered. so you have

0.96 - (0.96 * .33) = output to ECU = .64V

now as you can tell that is exacly 2/3 of the ORIGINAL (stock maf/injector) air flow that would have been needed to run the car. and you drive perfectly down the road..

then you come across that pesky mullett in the 5.slow Rustang and you decide to let the SR breathe and show this neaderthal who is king of the road. you wind your SR all the way out to it's full 300Hp potential and leave mulletore wondering what happened...but how did it work??

so you went all the way to 300 HP. on a stock MAF that would have been 5.77 volts..not possible. and as you know the ECU would have shut you down at 5.0 V anyway. but we have the Z-32 and we were runnign bigger injectors so here is what we had!! Z-32 output was 2.83 volts...Airflow meter corection is 2.04 and the Injector tuning had you at -33%. so our final voltage to the ECU was as follows..

2.83 * 2.04 = 5.77 (same as before)

now for injector correction

5.77 - (5.77 * .33) = final output to ECU = 3.87V

now as we discussed earlier this needs to be 2/3 of the original injector on time .... and it is very close (off by a few thousnaths of a volt). the ecu has no problem with a 3.87 Volt input and you are merrily going along leaving the mullet junky in the dirt!!

now...you get a good bonus at work and decide to upgrade the turbo!! you put on nice GT25R and you are now capable of 390 Hp (if only you could find that mustang again and really give him a lesson!!) so you go out there and stand on the gas!!. spool that baby upa nd right before redline the car shuts off. Agrhh...your frustration is un-paralleled by anything known to man!! why you ask yourself as you cruise back to the garage in low boost mode!! lets do the calcs!!

390 Hp on a Z-32 would produce 3.68V out of the MAF...it goes into the S-AFC

times 2.04 = 7.50V

Injector correction = -33% so

7.50 - (7.50 * .33) = final output to ECU = 5.02V

oops theres our problem the ECU shut us down again! its time for a re-program or bigger injectors....but at this point you are so far away fromt eh origianl power levels...i suggest just a reprogram.

Hopefully that clarifies any misconceptions about the S-afc and S-afc2!! and how they work!!

Scott

I30tMikeD

iTrader: (8)

The MAF signal is used at all times for timing and fuel delivery, not only in open loop. The o2 sensors are used only in closed loop.

You cannot just add larger injectors
You cannot just add a Z32 MAF
You cannot just add larger injectors and a Z32 MAF

There has to be some other type of AF control, an SAFC or FMU being the minimun. Let's say the z32 MAF flows 50% more than the stock MAF and you have 50% larger injectors, it still won't work. The voltage curves of the two MAF's are not the same. This has been done with a maxima. The addition of an SAFC and FMU can kinda make it work and get you a safe AF, but it is certainly not the best solution.

Stephen Max

iTrader: (59)

Fortunately for us, we don't have ecus that shut us down when maf voltage exceeds 5V.

Or maybe it is unfortunate for those poor souls who don't have other provisions for increasing fuel once the maf voltage goes above 5V.

slimer

iTrader: (13)

great post mike. Midnight, I see that you have not donated. Do yourself a favor and donate so you can search. These types of questions have been covered many times. I know that many of us are willing to help you out, but there are a bunch of situations that you have not even thought up that have been thoroughly discussed.

My suggested area of light reading includes:
Maf signals
FMU Calibration Calculations
Injector Duty Cycle
Detonation
Piggybacks (emanage, smt, and safc)

Anyone have any else?

Also, Mike's brother owns www.deatschwerks.com He can get you anywhere from 400cc-750cc injectors at a significantly lesser cost than oem injectors. Check out that and RC Engineering's site for more useful fuel related information.

Brad92SE

iTrader: (9)

Good info Mike, I stand corrected.

sleeper

i used 370cc injectors, with z32 maf, walbro 255hp, adjustable fuel pressure regulator, jwt ecu (96-5speed) modded for 370cc, z32 maf, with this set up everything worked perfect.

matty

iTrader: (54)

That will be my setup in about a week. I will have a 3" charge pipe as well

-matt

sleeper

make sure your plug is wired properly, i had mine backwards, and it was aweful, until i figured out what i did wrong.

matty

iTrader: (54)

How do they go ??
I havent looked into the wireing sceam yet, but I looked and saw a White black and red on my A32 MAF

-matt

maxlinegtr

iTrader: (3)

Thanx for the info...I thought I can just slap on the 370cc and have it running but I thought wrong. I just wanted to change the injectors to be safe. I guess I will just use the stocks for now. BTW i have 2.87 pulley w/ I think 9:1 disc.
sleeper: Can u give us a little more detail?
thanx

slimer

iTrader: (13)

what detail do you need? the maf wiring diagram?
http://jimwolftechnology.com/wolfpdf...%20NISSANS.PDF