Larger Injectors

[Don Dada]

Guys Im having a little issue setting up my top feed 555cc Nismos pink tops on my rb26

Following Pauls pfc faq the new settings worked out to 80% and -0.16 that is using a lag time of 0.61 as stated for Tomei injectors which I believe is the same as Nismos

Input the settings with the current map the car was running and it goes crazy lean

Input the settings with the pfc base map and it goes crazy rich to around 10.4ish

I really didnt expect it to be spot on but I never expected it to be that way off either. The thing is when I make my corrections to get proper afr on idle(14.7) it idles really lumpy and does not feel ok till I richen it up to low 13s..... BUT with the ac on it idles smooth even if I lean it out past 14.7

The rpm at idle and with the ac on is basically remains the same and voltage also remains the same at 13.9-14V. Otherwise cold/hot starts is normal.

I tried various combinations where I changed the correction % and the lag time together then even one by one, and compensated for it each time on the fuel map but it never wants to idle smooth unless its rich on low 13s

So am I to believe these injectors have to be on the rich side to idle smoothly?

[Lithium]

Thats really really interesting, I had Nismo 555cc yellow side feeds on my GTS25t and I had exactly the same idle issues, right down to the A/C. With A/C on the car would idle perfectly with around stoich AFRs but when A/C turned off (once the car was warmed up) it would lean miss even with AFRs even richer than .95λ.

I'd put that to the fact that I was using a G1 GTS Link ECU which didn't support sequential injection and the lean miss was just due to poor fuel distribution, and when I sold the injectors on to GotRice? and set them up with his G4 Link we never had any issues

So sorry, thats not really a good answer beyond the fact I've seen similar behaviour - good luck sorting it out and let us know what you find!

[zebra]

Nearly every RB I have played with/seen needs to be rich to idle right, my own 3 different engines included

[Don Dada]

Yea really interesting Mr Lith...Thought maybe I had a bogus set of injectors as they are second hand. I made up my own "test bench" and cleaned and flow tested them myself as no one does that locally, and they basically flowed the same with the higher flowing ones from 6 to 1.

I really didnt think I would have this sort of problem though because they not much bigger and they actually have less lag time than the std ones

Zebra...How rich is rich?

[zebra]

From memory (was a while ago now) 12.5-13:1...So not super rich

[DVS JEZ]

Leave the lag at 0 and see what it does.

[DVS JEZ]

Nearly every RB I have played with/seen needs to be rich to idle right, my own 3 different engines included

I have found the same. 13.2 is where i find they don't lean pop

[Don Dada]

Jez with the pfc base map, correction on 80% and lag on 0, as I go toward stoich it starts to get rough....Only with the ac off.

Its the part with the ac that has me stumped, although i did notice this even with the oem injectors and pfc,and even futher back when it had the oem ecu. It would always idle smoother with the ac on, Its just with these nismos now its really noticable with it off

I'm not sure I'd call it a lean "pop" though.... Its just sort of rough and afr moves around by about 0.3afr

[JonnoHR31]

yep most RB's, especially ones with old ignitors and coilpacks, idle like shit any leaner than 13-13.5. the reason it doesnt with the a/c on is the revs are higher, as soon as your off idle you can usually go as lean as 15-16:1 without any misfire issues.

are you sure the nismo lag times are less than standard? almost always bigger injectors have a higher lag time. either way if you have a wideband best bet is to adjust the scaling until you get the same afr's you had before with the standard injectors. adjust the latency until your idle afr's are the same then use high load to adjust the % correction and check both again.

[Lithium]

yep most RB's, especially ones with old ignitors and coilpacks, idle like shit any leaner than 13-13.5. the reason it doesnt with the a/c on is the revs are higher, as soon as your off idle you can usually go as lean as 15-16:1 without any misfire issues.

Most RBs I've done tuning have idled fine at around 14:1, including my own BEFORE putting in the Nismos. I played around with idle control speed to make it idle at similar rpm with aircon on or off and managed to keep it within the same zone and still, I'd get a lean miss at anything leaner than 13.5:1 and steady smooth idle with aircon on even up to 14.7.

From memory I set my mates idle afrs to around 14:1 when he got the Nismos and I believe it idles pretty good with that.

[zebra]

When I eventually get around to fitting my wideband to the Soarer I'll let you guys know what it idles at

[SargeRX8]

I have found the same. 13.2 is where i find they don't lean pop

I'm using 1.08 correction and it fixed the popping. The injector settings are annoying.

[Don Dada]

yep most RB's, especially ones with old ignitors and coilpacks, idle like shit any leaner than 13-13.5. the reason it doesnt with the a/c on is the revs are higher, as soon as your off idle you can usually go as lean as 15-16:1 without any misfire issues.

are you sure the nismo lag times are less than standard? almost always bigger injectors have a higher lag time. either way if you have a wideband best bet is to adjust the scaling until you get the same afr's you had before with the standard injectors. adjust the latency until your idle afr's are the same then use high load to adjust the % correction and check both again.

My stock set up with splitfires was able to idle good at 14.7 and even down to 15.0 with very slight roughness. And yes the lag time is less than std as stated on Tomei web site (0.61)and therefore have to input a minus value

Not sure I understand what you said in the last statement though because changing either %correction or lantency affects afr across the entire map so changing latency alone to get good afr at idle will affect afr on load too.

[DVS JEZ]

Latency mostly affects idle and low load. So i agree with jonno as this is what i have found when testing.

[JonnoHR31]

Not sure I understand what you said in the last statement though because changing either %correction or lantency affects afr across the entire map so changing latency alone to get good afr at idle will affect afr on load too.

as jez said, latency makes a big difference at low duty cycles (idle and light load) but makes bugger all difference at high duty cycles (full load) whereas % correction makes the same difference everywhere. so if you set the % correction to 80% as you have it should be fairly close.

then you get the car idling and adjust the latency until you have the same afr's as you did with the old injectors and it should be fairly close. you then check afr's under load and adjust the % correction until you have the same as you did with the old injectors, if the injectors flow what they should then this should just be a minor tweak if you have to change it at all.

then once you've got that set, check idle afr's again and adjust the latency if required.

the reason latency affects light load is its a set time that is either added or subtracted from the pulse time, assuming voltage stays the same this amount stays constant, therefore makes a bigger difference in a situation where the overall pulse time is only 1-2ms than it would under load where pulse times are more like 8-10ms (just an example, would vary depending on setup).

the % adjustment simply multiplies the entire base map by this %. so if with your standard injectors you have a 1ms pulse at idle and 10ms pulse at peak power then you put in bigger injectors and scale them to 50% without changing latency or any of the maps your now gonna have a .5ms pulse at idle and 5ms at peak power, therefore your going to have half the pulsewidth accross the entire map.

hope that makes sense.

Edited October 29, 2011 by JonnoHR31

[rob82]

What's your plug gap and heat range?

Most engines idle smother with some load on board. You can induce some idle load by retarding your Ignition timing. I usually only like running low timing advance when proportional spark control is available though.

[Don Dada]

Makes perfect sense Jonno. Apparently the lag time I was using was totally off and had it going really lean.

Thanks to Numleg on the forums I was able to get it set up right as he has the same injectors...Entered his setting and was able to get it really close to the original map fueling

The problem of the rough idle still persist though and I think I will not be able to get it smooth running any leaner than 13.1afr

Took it for a drive and with corr at 83% got good afr on load, Tried various setting of lag in 0.01 increments from 0 up to 0.16 and adjusted the fuel map to try get it to 14.7 but was rough at all settings

I tried it as well with the ac on, had the two cells(idle and ac on) at basically the same value in the fuel map, made lag correction change till I got it to stoich (so basically that would be the equivalent lag as matched by the std injectors), switched the ac off and it was around stoich but really rough.

I even fiddled with inj lag vs batt and also raised idle rpm and still no go. Dont know why the hell it idles perfect at stoich with the ac on and like a boxer with the ac off

Anyway for those who may use Nismo 555cc pink top feed injs use 0.85 as the lag time and not 0.61 as stated on Tomei's web site.....I actually did see this value suggested a couple of places but thought Tomei had to know what they were talking about....boy was I wrong. And i'm 99.9% sure Nismos and Tomeis are the same

Rob82.... I run Bkr7 at 1.1mm with splitfires. Doesnt the pfc lock timing at 20*?

[JonnoHR31]

yer pfc goes into closed loop at idle, adjusting the timing by up to 5 degrees to reach the target idle rpm. the main ignition map is ignored.

as for the roughness, just leave it rich, having it idle at 13:1 isnt gonna do any harm and isnt gonna make much difference to fuel economy. idles better with a/c due to the extra load as said, same as retarding the timing and winding the idle screw up, your using the same amount of fuel just with more air and less timing for the same result.

[The Mafia]

I've tuned heaps of RBs, from stock to heavily modified ones.

They all need around 13.2:1 to idle without struggling or popping.

Also, if you have a dickhead atmo BOV, this also causes issues.

[MsR]

when the titel read larger injectors i thought you meant running 2000cc at idle with problems...eg ID2000's at 40% duty cycle when runing so barely even lifting a finger. can that cause any issues with power fc for management?