JDM 2JZ-GTE A/F at boost levels greater than 14psi
I found this is SF's and thought it would be informative here and also give a chance for JDM 2J GTE guys to chime in on there Experience on stock 440's and Map Sensor.
My logic: The jdm engine is dependent on the voltage from the map sensor in determining the amount of fuel to inject. The voltage increases with boost pressure. At roughly 14 psi (or whatever fuel cut is at), the map sensor is sending about 4.2Volts (if i recall correctly). However at 4.3V (or whatever the boost cut voltage limit is), the ECU goes into boost cut mode (fuel cut).
All the BCC or FCD is doing is using an adjustable resistor to limit the amount of voltage the ECU sees. To effectively disable fuel cut, it must not see the amount of voltage that induces the fuel cut.
So, let's they run 17psi. The BCC is still only letting the map sensor see 4.2 volts, which it correlates to 14psi. The ecu sees this level of boost as safe and doesn't induce the fuel cut. However, it is still only injecting the amount of fuel based upon (4.2V or 14psi) while the engine is in actuality running 17psi.
Obviously running 17psi requires more fuel.. So why does it work you ask? The ECU "dumps" fuel at higher boost levels. It is programmed from the factory to run very rich at higher levels. In relation, the amount of fuel it dumps at 14psi (4.2v) is excessive for that boost level (and very safe). With the BCC, it is still dumping that amount of fuel for 14psi, but because the engine is running 17psi the A/F ratio is closer to stoichiometric or lean conditions.
Is this safe? Judging by the amount of people using it and not destroying their engines persuades me to believe that the a/f ratio at 18psi or so (which is the common level of choice for them) is still relatively safe, even though the map sensor is still only injecting the amount for 14psi.
So, I would advise the use of a wideband o2 sensor with the BCC mod on JDM engines to monitor the A/F's.
Hopefully that makes sense and isn't too redundant.
REMEMBER: This is only for JDM engines. The "TURBO PRESSURE SENSOR" on the USDM engines is only used to determine boost cut, and is not dependent on it to determine the amount of fuel the engines needs at a given x amount of boost. It uses an air flow meter to determine this. That's why unplugging does not affect how the car runs..
I'm currently running 16lbs, 11.2 a/f, FP set to 40psi and this is on a big t70. Boost will be going up once winter leaves and the air is less cold.
Note this is on Stock JDM 2JZgte w 440 injectors still, I'm not sure if the ECU is stock its the one I got with the motor, it does have a chip inside it with Japanese writing on it. Ive yet to hit fuel cut or speed cut or any of that.
Lets see some more numbers on the stock JDM setups!
This ad is not displayed to registered members. Register your free account today and become a member on Club Lexus!
jdm harness and ecu done by tweakd
full 3 inch exhaust
Titan cam gears
With stock vacuum lines on the vsv's the car does about 15psi in 2nd gear, and afr is between 11.2-12.00 which is decent. If I put a t in the vsv line the car will make 17psi in 2nd and 3rd gear. I have seen the afr range from 11.5-13.0 which is a bit risky. I am going to put 550cc injectors in it and tune it with a afc.
^ Not bad are you running an adjustable fuel regulator? And ya 13 A/F is a lil risky. Just to *** If your going to tune it I know its expensive but standalone is the way to go instead of the Safc tricking the ECU plus I dunno if we can use a VPC with a Map sensor? If we could that would be decent with an SAFC.
From what i have read, the vpc can not be used with a jdm aristo ecu. It needs to tap into the maf signal even though it does remove it. I wanted to use a vpc but i would have to use a usdm ecu and all the other crap that goes along with it. With 550's the safc should work ok.
If you install larger injectors you can scale back the map sensor signal with an afc (or use a slightly larger map sensor) and this will effectively increase your fueling at higher boost levels than 14 psi, the problem is though you will be running more agressive timing due to the lower than normal map signal, and also your idle load will be different from normal, so its really a trade off that only works if you don't go too large in injectors. 550's and an safc may work well and get the job done for 18 psi, I personally wouldn't push it much past 550's on the JDM ecu though cause the timing will be problematic once you adjust the map signal for fueling, but people have installed much larger injectors and gotten away with it.
1995 Lexus SC300 5spd Na-T ( TT Ecu Mod + a few others)
SAFC advances timing if you pull fuel. An Emanage Ultimate allows full timing and fuel control, so it would be better than a SAFC for sure. I THINK Emanage Blue allows timing retard, but I am not positive on that.
i am having the exact reverse issue here as my a/f with the aristo vvti swap go right to 10.0 under full throttle /full boost which hits 14.2 instantly .. i cant figure why so rich.. i have a walbro intank using the sard jet pump killer , using stock feed as return and ran a new -6an to the front connected to the feed at bottom of block where fuel pulsation damper is ....using stock pink/red top injectors and stock rail with stock fpr attached to rail.... tried a brand new jdm maf and tried another map sensor to no avail...i am using 7 heat range iridiums and i wonder if plug is to cold for the application and should go back to 6
let me also add that i was able to scan ecu thru jdm scanner and the one and only o2 sensor registered a fault with heater circuit which means its not heating up to burn carbon off , could that be the issue