hi! from a newbie in canada. rb25det neo, in 240sx

[polemite]

yeah, i hear ya. but it's not flooding. i wondered that, and zero'd out the crank enrich, and cranked with the throttle wide open to clear it out. that was my first move. but it didn't fire at all.

i stepped up incrementally until getting to the point when it was just starting to fire.

there must be something else wrong there. kinda doubting the battery though. nistune reports 11.6v, but my meter reads 12.2v.
plus the problem didn't go away when we were jumpstarting it.

it's very odd. temperature is definitely a factor. both ambient air, and coolant temp. seems to do better in cool ambient air.

up till this tune, cold start always started. might have cranked a bit more than it should, but it always started. is it the tune, or is something wearing out? i don't know.
up till this tune, my idle was great. but now it's stumbling at full temp and 650rpm target.

out on the road, it's fine. this tune needs mapping obviously, but the engine still seems to operate perfectly under normal driving conditions.

as you suggest, i'll reduce k 20% and allow TIM to auto adjust, and see where that gets me. this puts K at 283 and TIM at 614.

my new o2 sensor has arrived, so i'll get that in there and see if it helps the idle. i'll adjust latency if the idle gets rough. see if that makes a difference.
if i can't figure out the starting issues, i guess i'll have to start changing parts. maybe another new maf. plugs. maybe follow through with the new fuel rail and regulator. send the injectors away too. maybe a different brand of coils.... ugh.

********
update
the new K and TIM settings, along with the new o2 sensor, has been an improvement.

the o2 reading is much quicker, and afr holds more steady.

i've got the crank enrich at 11 now. not right, but a big improvement. makes me wonder if i could dial it in better with adjustment to TIM? provided that it doesn't mess up the trims of course.

*******
another update
load scale appears to be good. i was able to hold a 3rd gear pull until 6800rpm, and it reached 152, at 14psi.
only some small adjustments in store for the next map attempt. it's very close.

although afr's hold more steady now (at idle and cruise), i notice it's slightly on the rich side. i'd say 14.3-14.5 would be the average, with occasional swings above and below in either direction.
trims are holding close to zero at 2000rpm cruising. so if i remember right, i need to try adjusting the injector latency, although i still wonder if slight adjustments to TIM might also improve the starting, and get my crank enrich numbers where they should be.

[polemite]

more testing today-

the morning commute was 14 degrees ambient air temp. hard to start, but did catch. no adjustment to crank enrich in that column.

high load pull approaches the boost limit of 15psi, and just shy of the full scale load limit (i think it hit 159 for a moment). did not rev to redline. didn't feel right.
short and long trims were both bang on 0% when i arrived at work. (18 minute drive)

afternoon commute was 33 degrees ambient air. hard start, but did catch. no adjustment to crank enrich in that column.
i did adjust injector latency from 870 to 840 to try and get closer to stoich idle afr.

managed to pull 2nd gear right to 7100rpm (rev limit). 11psi of boost, and only 147 was the peak for the load scale. (wheel spin nearly all the way through the power band)

hit a peak load of 153 in 3rd, and 11.5psi of boost, but didn't rev it all the way out.
at the end of that commute, both trims were sitting at 10%. i found this odd.
sat for 5 minutes, and would not restart. coolant temp was at 90. crank enrich was already adjusted to 11, from 5. tried again at zero. nothing. tried again at 20, and it fired up.
drove another 10 minutes. at the end, trims were zero short, and 10% long.

not sure if this change in trims is relevant. not sure if it's in response to adjusting latency (which did seem to clean up the idle), or if it's in response to the ambient air temp.
still not sure what is causing the hard start and hot restart, but seems to be temperature related, as that setting of 11 in the 90 degree column was working on a cooler day. (makes me wonder if this is a maf cartridge problem?).

[polemite]

a thought crossed my mind today, as i was scanning the nistune documents for clues on how to fix my cranking/starting issues-

what is the base fuel pressure of the r35 gtr?

i have been setting my fuel pressure at 43.5psi, as that is what's recommended by nissan in the service manual for the rb25det neo....

but i assume that injector flow rate is dependent on the operating pressure of the system that they are designed for.

i used the radium engineering install instructions to confirm what little info google was turning up- gtr base fuel pressure is supposed to be 55psi (or 3.8 bar)

r35 static fuel pressure.JPG

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so... now the question is, do i raise my base fuel pressure to 55psi, and tune around that? or do i assume that i should recalculate the injector flow rate based on a pressure setting of 43.5psi?
if you can trust the ebay sellers of the world, you can see this cleaning and flow test data for gtr injectors, flowing 550cc at 43.5psi.

r35 injectors at 43.5 psi.JPG

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[polemite]

update-
i tried an injector resize from 570 to 550. didn't make any difference to my starting issues, so i reverted back to the 570cc tune, since i've already roughed in the map at high load.

i did several hot restarts and played with the crank enrich each time. i found that a setting of 15 across the all the warm temp settings had it starting perfectly.
later in the day, with the ambient temp probably 10 degrees hotter, it took slightly longer to fire, but still started fine.
cold start this morning maybe took an extra crank or so, but i could probably improve that with a little extra fuel.

i know this shouldn't be right, but it is what it is. not sure what could be so drastically effected by ambient air temp.
maybe the idle air controller? maybe the maf cartridge? vacuum leak? i went looking for loose hose clamps on the iac. nothing jumped out at me. i'll clean the maf next. i do have another (used) maf cartridge that i can try.

[Matt]

Yeah I'm not sure on that one. What you set in the table is what the injectors pulse at key on, but then is adjusted by length of time of cranking and engine speed etc in those tables you see.

[polemite]

ok, thanks for the info.

as of last night, i cleaned and tried my other maf cartridge. still needs crank enrich set at 15 to work.

tried raising fuel pressure to 55psi, but didn't make any difference.


next, i'm going to try cycling the idle air controller a bit. i seem to remember doing that once before when i was stuck in high idle. currently idle is about 100rpm higher than it should be, so that's what has me looking in that direction.

after that, i have a new set of spark plugs to try. i might even adjust dwell time at 12v to see if that makes a difference.

if i haven't found anything after all that, i may try looking for vac leaks with smoke.... or just live with it... might not be right, but i've got it working at least, and it seems to run great out on the road. maybe i'm overthinking this problem.

[polemite]

finally got around to changing out the spark plugs.

didn't make any difference to the fuel settings while cranking, but they sure did make a difference under power.

i gapped the new ones to .95mm, using the 50ignite r8 coil kit instructions as a guide for that. the old ones measure at more like 1.15mm.
resistance check showed the old plugs were definitely getting to the end of their life too.

very smooth cruising, and feels great under power, all the way to 7000rpm. no sign of sputtering near redline now.

the map is a bit odd though.

i'm getting slightly above full scale load (162) in 3rd gear mid range. again, this is cool morning air that seems to push boost up to near 15psi. it doesn't climb that high in the heat of the day BUT, the long term plan is to shoot for 15-17psi, so eventually i'll have to adjust K a bit more.

afr's are also going for a bit of a roller coaster ride. my fuel map is reflecting this, and it might even get more pronounced if i keep chasing 11.5 as the target.
again, the numbers i'm entering are getting quite low. like 18, and that's still rich in that area... but maybe that afr is residual from the big shot that i give it in the transition zone? i'll play with it some more. flatten out the early peak and see where that gets me.

aug 15 map.JPG

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[polemite]

ok! time for an update

a few weeks ago, i was having afr's were not holding steady. they would get richer along with cooler temps. the hard starting issue was also getting harder.
and then one morning, my dash and marker lights stopped working. that was the final straw. i planned to eliminate the possibility that an electrical problem might be causing my fueling problems.

so with the help of the electrical prints, i went looking for causes. found that the lights were likely the combination switch. that was true.
but also after testing i found that the ignition switch was working questionably. it has the potential to drop power to the ecu while cranking. took that apart and cleaned it too. much better testing after that.

then i noticed the battery voltage was getting low. i didn't want to believe it, but my very expensive battery wasn't holding up under load. i should have listened to matt earlier. bought another (bigger) battery.

but also, i talked to a guy that told me about how the gtr injectors are indexed 90 off from the rb injectors. so i took the fuel rail off, modded the tabs for the retainer clips, and turned all the injectors 90 degrees.

taken together, the starting has improved a lot. from a hot crank enrich setting of 20, i'm now down to 8.
but out on the road, i now also have better trims, way faster and more stable afr's under load, and a lot more wheelspin.
so i'm now a believer in indexing the r35 injectors to make them work properly.

[Matt]

This is good news that you finally found the culprits. There is a point where the information we can provide is limited as far as assisting you, especially if fighting electrical and/or mechanical issues (in your case both)

[polemite]

thanks for all the support that you did give me, and to PL too.

i hope that by documenting all this, somewhere down the road, it saves you and someone else some time. (including my future self).

[coupelove]

great thread, thanks for posting your process.

hope to read some more. would be great to see some more pics of the car too.

[polemite]

thanks! glad to know you found it useful.
the car is still running and sounding awesome. i feel like i'm finally ready to start cranking up the boost. although, i might revamp the wastegate dump pipe. either enlarge and improve, or dump to atmosphere. maybe try both. haha.


i've actually video documented most of this, but i haven't edited it yet. it's a huge volume of video to sort through. so eventually, there will be an in depth tour.

[polemite]

early snow this year, and so ends another driving season. got it washed and tucked in to bed just in time.

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