Nistune Forums

Hi guys

I recently installed nismo 740cc injectors, aeromotive stealth 340 lph, and N62 (Z32) Maf. After installation and the auto re calibrations (TP Scale, TTP) and adjusting inj latency to 660 the car would give a hard cold start with mild erratic idle (also I recently installed Tomei 260 cams prior with no issues with stock sr maf & inj). Also ign timing at idle jumped from 15* to 25*-29* at 1300rpm and 21* at 900 - 1000rpm with AFRs in the 14-16 range...
HELP!!!!!!!!!!!!!!!!!!!!!!!

stretch out the timing scales in the low rpm, low load areas.

did you set the base timing or TPS correctly after the engine mods?

The TPS is set to .40 and timing is 15*. Whats hard for me to understand is that when I run the stock (sr20det redtop) map (370cc inj setting with the 740s in) it starts easy only thing is it has the pig rich afr (naturally). Now after I do the change injector process in Nistune the engine just goes oout of wack!?!?! Hard start even with playing with the throttle, high ish and erratic idle, afr's jumping from to rich to too lean when trying to get it at 14.5 afr, stalls on rpm fall (coming off the throttle)

-So even tho NIStune re scaled the map I should stretch the low rpm/load area on the map even more? Could someone post a map showing how much of a stretcch I have to do for the 740cc inj?

-Whats the latency for the nismo 740cc inj? I read somewhere its .66ms. could u confirm?

-Would I have to re-scale again for the Z32 MAF?

Try starting from a factory base image and making changes only once before saving..
(to ensure that there is no chance that the same change was made twice causing the map scaling).

Start off with latency around 800 - 1100 as a ball park. Don't try to get idle mixtures right at first.. you just need the engine to idle well enough to be able to drive the vehicle and correct injection multiplier as per nistune mapping guide.

Is the base fuel pressure set back to standard or lower after the cam and fuel pump replacement? larger injectors often require lowering pressure to maintain idle mixtures if pulse width reduction doesn't allow enough scope for fuel control.

check if TTPmin is low enough to enable the ecu to adjust correctly for idle and decel.
start from 0 and see what is required from reveiwing logs once tuned to get the final value.

Ok so I started with a fresh base map (redtop sr), input the resize injectors, dropped the ttpmin two (2) values across the board, put in 800 for inj latency, fpr at 3bars (43.5psi) then I swung the key and didnot start . So then I increased the k constant in small increments until it hard started on its own.
I turned off the 02 sensor and knock sensor, "0" out the fuel map and played with the k constant and the latency until I got for the most part a smooth idle. So now it idles between 900-950rpm, afr between 13.5-14.0, vacuum at a stable 16 inHg (I have 260* cams).
Next concerns now are the timing at idle feels smoother at 21* (Nistune readout) , when reved it catches its self but falls to low IMO (450-500rpm), and there is still a hard start.

So now my KCONST is 9060
Injec Latency is 850


My Setup: (If it helps)
SR20DET Red Top
Tomei 260 cams
BC Springs
3" Exhaust + De Cat
Voltage stabilizer
Grounding Kit
Throttle body & Intake Mani Thermal gasket
Devils Own water/alchy kit
ARC SMIC
Cusco metal intercooler cold pipe (replaces stock plastic pipe)
Aeromotive Stealth 340 pump
VMS FPR
T25g
HKS actuator
Nismo 740cc Inj
and once I sort out the injectors a Z32 MAF

For the hard starts it seems as tho its cuz i allowed nistune to adjust the cranking tables (cold enrichment, crank enrichment offset, etc). I added back 4 values at the 158*F mark in the crank enrich and crank enrich offset (that was the car's water temp at the time) and it cranked on the first swing had a little bog after starting but that might be due to the other adjusted tables. Gonna wait till the morn to add across the board and see if it helps the cold start.

good to hear you are sorting through it.

what was the original 'k-constant' 39000?
was the base fuel pressure checked with tps 'off' eg.1200rpm?

seems like a massive drop in k-contant value unless I'm looking at the wrong binary. (which is always possible)

bachig24u wrote:good to hear you are sorting through it.

what was the original 'k-constant' 39000?
was the base fuel pressure checked with tps 'off' eg.1200rpm?

seems like a massive drop in k-contant value unless I'm looking at the wrong binary. (which is always possible)

My original K Constant with the stock (92 180sx sr20det redtop) 370cc was 21474 and the nistune "resize injector" calculator carried it to 10737. Now I carried it down to 9637 with my latency at 835 and everything is 99% (idle, startup, part throttle, wot). The high timing I found was due to the idle switch not being activated, so I unplugged it start, shut down plug back up and it was bck to 15* at idle. So what was happening is it was reading off of the map instead of being fully in closed loop mode.

The hard start was actually due to the cranking tables being changed when I used the "injector resize" so I did it again and unticked "adjust cranking tables" however I did manually adjust the crank enrichment table cuz it was measured in ms which means ( I think) that it doesnt use the k constant so I divided the values by .5 (740cc is double 370cc). I learned alooot over this past 5 days.

Now to tackle the MAF, shouldnt be as hard i hope

using 740cc I think is probably wrong with injector resize...
2100/9000 ends up being about x2.3.
This means your injectors are either 870's or your base fuel pressure is too high (roughly 15psi)causing your latency and K to be so far off calculations.

anyway, whatever works is good!!