Injection Timing Injector Trims With Pfc .

[discopotato03]

Quick question . A while back I remember people saying better to leave the trims at 100 and punch in numbers in the fuel table to suit . I'm curious to know if using say "50" trims and 740 Nismos has any affect on injection timing .

Battery going flat , cheers A .

Edited December 8, 2012 by discopotato03

[STATUS]

thats an approach used by those who cant tune pfc properly.... ie no understanding of the backgrounds operations... there is a particular workshop here in melb that we are forever retuning, yes it makes numbers on the day but wont return decent fuel economy and have terrible transient response etc...

[t_revz]

Not that its a huge difference but my nismo 740s are at 52% 0.02ms. Been like thar for 8yrs+

[MJTru]

thats an approach used by those who cant tune pfc properly.... ie no understanding of the backgrounds operations... there is a particular workshop here in melb that we are forever retuning, yes it makes numbers on the day but wont return decent fuel economy and have terrible transient response etc...

Status can you expand on that a little bit mate

thanks.

[rob82]

Quick question . A while back I remember people saying better to leave the trims at 100 and punch in numbers in the fuel table to suit . I'm curious to know if using say "50" trims and 740 Nismos has any affect on injection timing .

Battery going flat , cheers A .

Absolutly no affect on the inj timing - only duration....

As status said those that know how to tune will use the appropriate tables!

Edited December 9, 2012 by rob82

[MJTru]

compensations are known as "trim" right ???

the ecu is looking for 14.7 all most all the time on closed loop of course, so if we were to say WOT them the ecu needs to add fuel, it then gets feed back from sensors and if it doesn't see any change in richness (which is needed for more power any where between 12.5-14.7) then this is what the trim table is for compensation also known as trim?????

please give me your point of views as i have shared mine, which may be wrong. lol

these short answer helps no one, but thanks again mate.

[discopotato03]

Ok so I gather using the trims , which is what I did , is the way to go and set up the extras to suit .

I was just curious to know which way they widen/shorten the injection pulse because I keep getting a rich spike every time I lift off and nothing I do fueling wise seems to help . Just because I did try setting the trims to 100 and halving my fuel table but it didn't do anything positive so I'm back to 51 - residual ethanol because I'm back on pulp again .

Something I really don't know is if these PFCs are a it slow processing wise and possibly slowing down their responses .

I'm saving my pennies and the proceeds of parting the old Roo will probably go towards a G4 or ViPec Plug in .

A .

[discopotato03]

I thought a bit more about this and changed my trims back to 50 yesterday and made whole fuel table changes to get back in the ball park .

I'm beginning to think that the trim changes I made when I was using E70 E50 and E25 blends , as in over 50 just for the Nismo 740s , was the wrong way to go about increasing the fueling and was probably a large part of reason why I had such poor consumption with high ethanol blends .

It sounds like the injector trims and "dead time" compensations have to be right in relation to the standard injectors or the tune will never be really right . Thats not to say you can't use different numbers if you choose but I'm trying everything I can to make my car run nicely and not just throw fuel away for no good reason .

Cheers A .

[MJTru]

keep it up I'm much like you, I'm hoping guru's like status would give use his opinion, and insight in this matter. Most can just say short answers, but i'm hoping that he can go into how the back ground features work on the PFC.

[t_revz]

I could be completely wrong but I'm guessing what Trent was saying is by leaving injector settings at 100% then your increments aren't as fine when tuning.

Having injectors at 50% and 100 in a certain spot on the map, adjusting to 101 is only 1% change making it fine. Injectors at 100 and 50 on the map, changing to 51 is 2%. Would be more of an issue down low I'd imagine. Other settings that adjust the map by a percentage would also be as coarse.

Enough thinking for me, bedtime

[paulr33]

if youve got standalone engine management why not use it correctly?

setting it to 50% sounds like a brain dead way - almost SAFC Style, bend the tune instead of set correctly

[discopotato03]

Maybe I didn't read Trents post right - as in which is the wrong way to go .

So can someone who tunes properly tell me if using 50% trims on 100% oversized injectors was the right or wrong way to go .

There has been things mentioned like like other things in the background being affected by these trims if they are not set correctly .

Back in my Autronic SM2 days I thought I rember reading that sequential injection timing was set up around the end of injection pulse and where that was in the four stroke 720 degree cycle . If you wanted to inject more fuel the ECU opened the injector earlier to widen the pulse width .

I really don't know how Apexi sets these things up and I have no way of knowing if they allow for any of this with their injector trim function .

Some people must know if using the trims IS the right way to go with larger than standard injectors - or they are just a quick dirty way to get your car started when you fit larger injectors .

A problem I have , have always had , is that my mixtures seem to go rich every time I back off except when I'm right off the throttle and it goes into fuel cut mode . Often it goes rich and stays that way on a gradually reducing throttle position and won't change unless I increase the throttle or lift right off . Nothing I do with fuel or timing tables seems to cure this one . Obviously my "tuning" strategies are very wrong or there is some issue with the PFC/maybe Nismo 740s are dated slow reacting technology/something weird going on with my Tech Edge WB3A2 .

IF I can get the trim business right , 50% or 100% , I can punch workable numbers in my fuel table - enough to get around ok .

So spell it out , which way do I go because questionable drivability and poor consumption shits me up the wall .

PFCs may be dated technology but it would be a shame to burn the bucks and replace it with something else having not had the best out of it .

Cheers A .

[rob82]

Maybe I didn't read Trents post right - as in which is the wrong way to go .

So can someone who tunes properly tell me if using 50% trims on 100% oversized injectors was the right or wrong way to go .

There has been things mentioned like like other things in the background being affected by these trims if they are not set correctly .

Back in my Autronic SM2 days I thought I rember reading that sequential injection timing was set up around the end of injection pulse and where that was in the four stroke 720 degree cycle . If you wanted to inject more fuel the ECU opened the injector earlier to widen the pulse width .

I really don't know how Apexi sets these things up and I have no way of knowing if they allow for any of this with their injector trim function .

Some people must know if using the trims IS the right way to go with larger than standard injectors - or they are just a quick dirty way to get your car started when you fit larger injectors .

A problem I have , have always had , is that my mixtures seem to go rich every time I back off except when I'm right off the throttle and it goes into fuel cut mode . Often it goes rich and stays that way on a gradually reducing throttle position and won't change unless I increase the throttle or lift right off . Nothing I do with fuel or timing tables seems to cure this one . Obviously my "tuning" strategies are very wrong or there is some issue with the PFC/maybe Nismo 740s are dated slow reacting technology/something weird going on with my Tech Edge WB3A2 .

IF I can get the trim business right , 50% or 100% , I can punch workable numbers in my fuel table - enough to get around ok .

So spell it out , which way do I go because questionable drivability and poor consumption shits me up the wall .

PFCs may be dated technology but it would be a shame to burn the bucks and replace it with something else having not had the best out of it .

Cheers A .

I'm not sure which trims you are referring to as there is a few in the PFC. I was referring to the injectors trims when I made my previous statement. I'm not sure why PFC went the route of using trims and not just giving the tuner an injector flow parameter. Either way the value that you get is a calculated scaler of the actual injector flow rate. Combine this with the latency values gives you a pretty good understanding of how much the injector will flow for a desired on time.

Now for a maf based system using transfer table, you know the quanity of air entering the engine, all you need is the desired air/fuel quanity. This comes from the main fuel map, a value of 1 revers to an afr of 14.7:1 a value of 1.24 is 14.7/1.24=12:1 afr. Now with everything tuned correctly all you need to do isvchange the main fuel table value to what afr you desire.... Well that's the way I tune anyway. I usually spend more time in the maf transfer table making sure I get that correct, then slightly trim the main table to make up for any slight imperfections.

Don't concern yourself with processor speeds it makes very little difference for the type of control systems and calculations you will need on an rb. Trust me I can get a old 8bit 68hc11 delco computer to run a vn-vt v8 better than all the bells and whistles mpc555 32bit float motec running at a close to 100 times the instruction speed. Software is everything... Just because you can't get to all the tuning parameters in a PFC doesn't mean it is flawed.

I believe the issue you are seeing is probably due to slight reversion, what bov are you running?

[t_revz]

Now for a maf based system using transfer table, you know the quanity of air entering the engine, all you need is the desired air/fuel quanity. This comes from the main fuel map, a value of 1 revers to an afr of 14.7:1 a value of 1.24 is 14.7/1.24=12:1 afr. Now with everything tuned correctly all you need to do isvchange the main fuel table value to what afr you desire....

I knew a value of 1 was 14.7 but I'd never thought about others. I wonder why my tune has been set up in the top corner boxes with 119 fading out in all directions. Seems excessively rich for idle and take off

[discopotato03]

Standard , all my inlet plumbing is bar the panel filter GTRS and GTt IC .

I had to do a run to Hornsby yesterday and with the mapping I was running and trims still at 50% I was actually starting to get some half reasonable fuel consumption . On the way back I was thinking about this trim business and thought WTF and loaded the 100% injector trims and the fuel map I briefly threw together last week . Not surprisingly it felt flat so on a whim I loaded the default RB25 timing map and that really brought it to life . Under load it was a tad rich IMO at 0.85 lambda so I leaned off the on load cells and its now feeling pretty good and giving what looks like good consumption .

The fuel table numbers look different ranging from 0.500 ish to something like 0.722 but anyway it feels better to drive . I'll be interested to see what sort of mileage I get out of this tank of Ultimate . It occurs to me that the piss poor consumption I was getting on E70 EFlex was probably partly because of where I had the injector trims ie 65% - 50% for the double size injectors + 15 for half the extra 30% for ethanol . I may stick another tank of E70 through after this one to see if it works for that as well .

Cheers A .

[discopotato03]

I still haven't got a real answer to the original question . I have been running around with 740 Nismos and using std injector trims 100.00 , Paul reckons this is right but I've yet to hear from workshop tuners .

In my experience you tend to have to use slightly rich AFRs and if you try to lean them off drivability goes through the floor .

I just happened to be looking at someone elses PFC maps yesterday and noted it had standard injector settings (both) but was used with RX7 Turbo injectors - top feed conversion . I gave this a go and it went real lean and would barely idle . So I went back to the 0.13 correction 740 Nismos are supposed to run - and tried 0.15 as well which made all the normal drive stuff much better as in smoother and torquier .

I am convinced that the larger the injector you use the more critical injection timing as in end of pulse timing becomes . Obviously having all the fuel in at the most advantageous time in relation to inlet valve timing makes a difference .

It would be real interesting to know which end of the injection pulse these PFCs change to alter the pulse width , and if its different for fuel table and injector trim changes .

I don't believe the theory that untimed or batch fire injection works as well as sequential injection overall , and if no thought is given to injection timing with a sequential system its a bit of a waste IMO .

I went searching for opinions of sequential injection timing and these threads may interest some people .

http://www.miataturb...njection-55183/

http://nissanroadrac...read.php?t=3568

http://www.msextra.com/forums/viewtopic.php?f=131&t=38399

Cheers A .

Edited December 16, 2012 by discopotato03

[rob82]

Trust me injection timing has very little effect on most engines. On an aspirated engine with the right size port and a decent helmholtz resonance point you may see +/- 3% fueling change from optimal to worst injection timing point, and the effect of injection timing diminishes when moving away from the inlet timing resonance points.

Trust me most tuners don't tune these tables because a. They don't understand how to or b. They couldn't be f**k because it make little difference.

I had a supercharged v8 with an autronic running wasted spark and id1000 they had the injection phasing 360degrees out due to the wasted spark, the difference was f**k when retuned..... Made a tiny difference (2-3%) to wot afr at low rpm, that was it.

Also Paul is wrong - scaling the injector trims when changing injectors is the proper way to tune. I though you would have understood that from my previous post....

[discopotato03]

Well I think there is more to sequential injection timing than meets the eye but because of the endless engine and component combinations out there its difficult to find common ground . I posted three of four links I had because one wouldn't work . Anyway in one of them it was mentioned that the larger the injector gets in relation to capacity and performance the more important injection timing becomes .

We know that when changing from batch to sequential injection the injector size generally has to increase because it has only one shot per cycle to get all the fuel in rather than two like batch systems have .

I don't think the car manufacturers went to sophisticated engine management systems for no reason and emissions and consumption would have been the reason why . Also competition cars often now have to put up with limited pit/fueling stops so they need to have performance and acceptable consumption to finish/be competitive .

They ALL seem to use sequential injection which when you look at it is reasonably complex when compared to simple batch fire systems .

Back to PFC land . For me I'm using 740cc injectors which in theory are twice the size of the OE ones . I'll assume the injector trim business effectively cuts the pulse width in half BUT , is it the start or end of pulse and if its the end then the injection timing point which is generally regarded as the reference will have moved .

I can only say by doing it that doing things that I reckon changes injection timing makes a difference to how my car runs , I want to know why making the sorts of changes that get similar AFRS in the fuel table don't achieve the same ends . Granted some of this is probably how PFCs time accel etc changes but if its as you say it shouldn't matter what alters the injection pulse width . How can anyone draw any other conclusion than the given pulse width has moved and made significant drivability and torque differences particularly at small throttle openings .

In a flat out high rev/load situation I can see how the injection timing could become insignificant particularly if the injectors are barely large enough at full power/revs and are open most of the time to keep the fuel flow up .

But this is not where road cars are most of the time - they are being driven at part throttle light loads and low to medium revs .

Anyhow I can go back to using 50% trims but I'm certain that if I got my fuel table close again I could move my voltage corection around and make differences positive and negative depending on what this engine likes most .

I hope I have my original dat files from before I started playing with Eflex E70 because even though the fuel table was a bit squiff it made more usable torque than it has since .

Overall the only way to know for sure is to use an engine management system that doesn't hide anything , get it tuned and ask the tuner to move the injection timing around and see what happens . I remember reading in one of the above linked sites that sometimes optimising the injection timing means the AFR stays the same with slightly shorter injector pulse widths .

It probably wouldn't be that hard with something like a Vipec computer to set it up in auto tune mode , start fishing around with the injection timing and note the injection pulse widths milli seconds whatever . Obviously if the AFR remains the same and with less fuel you've achieved something , if the torque doesn't fall away you've lost nothing .

I'm not saying you are wrong , what I am saying is that its worth a go to see if there are any worthwhile gains to be had .

I think to some degree we are flying blind with Datalogit because it doesn't tell us some of the things going on we need to know about with PFCs . Maybe most don't have my nasty minded curiosity and those that do just change to a computer that shows all and does rightly or wrongly what ITS told to do not what some invisible third pary thought was right - years ago when PFCs were current .

Guilt Toy whats your opinion on this ?

Cheers A .

[GTSBoy]

Oh for Christ's sake. Any 6 toed moron who was given the job of designing a sequential injection ECU would make the fixed point of the injection pulse at the end and add increasing time by opening earlier. It has been that way since forever. I can remember it being that way in the early 90s. There is no way that the PFC would be any different.

Good aftermarket tunable ECUs may allow you to adjust the injection endpoint. But they only do that for the nth degree of tuning finesse that the real fussy will want to achieve.