Apexi Fc Injector Lag Time Setting

[GeeTR]

Hey Friends,

I posted this in the NS.com forums, but thought this is totally aplicable here, as said, this effects my setup too.

Please see attached which is from the Apexi PFC RX7 online guide that everyones seen (Bottom right hand corner)

I have a mate, who's tuner used minus numbers (-0.04) i believe, when using SARD 740cc's on a SR20.

Now from all the literature iv found, plus reading around on forums like these

http://www.nissansilvia.com/forums/index.php?showtopic=50277

It seems pretty clear that going injectors double the size, would need settings like 50% for the size and PLUS (+0.04) numbers for the lag time.

Seriousally, any help would of massive help!! Im 99% of the A:, would just like some HC acknowledgment of the setting.

THANKS!!!

Michael

Edited March 20, 2007 by GeeTR

[DivHunter]

Lag times are not directly related to the size of the injectors and are not linear. When you get the injectors flow tested and cleaned they should be able to give you all the relevant info.

[Guilt-Toy]

if you completly re-map the ecu then you dont need to worry about this do you ???. its only when using the stock map to bring the a/f ratios right. correct me if i am wrong.

[180or200]

It seems pretty clear that going injectors double the size, would need settings like 50% for the size and PLUS (+0.04) numbers for the lag time.

I'm not sure this is as clear as you think, surely when fuel pressure is constant and you double the size of the injector, it's not going to flow double the amount without increasing pressure?

someone set me straight if this isnt correct ( be nice ) but isnt the closed loop on the fc factory set, so wouldnt that mean you adjust injector percentage until its in the correct afr range of 14.3-14.7 at idle? then correct your fuel map for "wot"

anyhoo mine is a rb25 and has nismo 740's set to 65% and 0.00, afr's sit on mid 14's then dips too 11.5 then sits flat on 12 till redline.

when i installed i set to 50-55% and closed loop could only manage high 15's

no problem with pops or cold starts here and those settings were left alone!

i think this subject should be discussed further, no offense but the FAQ is a little vague in this area!

[Robo's]

I'm not sure this is as clear as you think, surely when fuel pressure is constant and you double the size of the injector, it's not going to flow double the amount without increasing pressure?

someone set me straight if this isnt correct ( be nice ) but isnt the closed loop on the fc factory set, so wouldnt that mean you adjust injector percentage until its in the correct afr range of 14.3-14.7 at idle? then correct your fuel map for "wot"

anyhoo mine is a rb25 and has nismo 740's set to 65% and 0.00, afr's sit on mid 14's then dips too 11.5 then sits flat on 12 till redline.

when i installed i set to 50-55% and closed loop could only manage high 15's

no problem with pops or cold starts here and those settings were left alone!

i think this subject should be discussed further, no offense but the FAQ is a little vague in this area!

How do you stop the dip to 11.5 A/F?? mine goes to 11 and i want to lean it off a little when i press the throttle

[180or200]

How do you stop the dip to 11.5 A/F?? mine goes to 11 and i want to lean it off a little when i press the throttle

dyno time is the easy answer, someone who will take the time to flatten out the afr's, mine coincided with a slight boost spike and was advised to leave alone!

[Guilt-Toy]

I am not sure that would be a very good way of doing it because if you do that then how do you really know what the a/f is on cruise ?

Every power fc i have tuned I have reset the ecu and used no injector correction and use the numbers in the map to controll the fuel - i usually leave the ignition timing stock unless trying to bring on boost quicker (big turbos only)

Anyway the reason i think that is not right is because if your relying on closed loop mode to keep your a/f ratios in order on cruise is that it will not be very reliable or very fast in gauging what the ratio's are to correct it and also keeping in mind that the oxy sensors are very slow and it will be running really rich or lean untill its corrected.

The best way to do it IMHO is to completly re program the whole map and leave all corrections standard so the car runs good a/f ratios on cruise and leave the oxy sensor OFF. i have found that it ALLWAYS richens the mixture up to the point where it uses more fuel and changes the a/f ratio from 14.7 back down to 13.3 - 13.8 which is using more fuel then is needed.

I guess thats one of the the differences from getting a quick $200 tune to a $800 tune from various workshops around the place.

Keep an eye out that some people around are only reporting 300km's to a tank with 200rwkw and some (like myself) get over 500 if i dont hammer it everywhere with over 300rwkw.

If your in nsw near sydney send me a PM if your keen to fix it up on a road tune..

I'm not sure this is as clear as you think, surely when fuel pressure is constant and you double the size of the injector, it's not going to flow double the amount without increasing pressure?

someone set me straight if this isnt correct ( be nice ) but isnt the closed loop on the fc factory set, so wouldnt that mean you adjust injector percentage until its in the correct afr range of 14.3-14.7 at idle? then correct your fuel map for "wot"

anyhoo mine is a rb25 and has nismo 740's set to 65% and 0.00, afr's sit on mid 14's then dips too 11.5 then sits flat on 12 till redline.

when i installed i set to 50-55% and closed loop could only manage high 15's

no problem with pops or cold starts here and those settings were left alone!

i think this subject should be discussed further, no offense but the FAQ is a little vague in this area!

Edited March 21, 2007 by Guilt-Toy

[180or200]

I agree a full remap is important, I just wonder whether a 50 % setting for 740's is anywhere near enough fuel, it will get it to the tuner but will need more work!

and yes i have had a full tune, thanks for the offer,

I have a apexi pen timer with afr feedback are these very accurate ? seemed pretty good compared to the dyno reading, it sits on 14.7 on cruise,

just for reference Guilt-toy were did your injector setting end up?

[Guilt-Toy]

Anything using the standard oxy sensor is not going to cut it as far as i am concerned. Sure its good for a guide and cruise it could be okay but for tuning you must use a wide band.. i prefer the Autronic one but alot of the cheaper ones are just as good these days

I have re-mapped my ecu twice in the last 3 months (once when it just hit 800ks at 296rwkw for fuel economy which failed missions and the second time to pass the emissions test and 317rwkw)

The first time i had stock fuel pressure and had it set to 0% either way and the second time i raised the fuel pressure from 28psi (yeah it was low) to 45psi and i had to drop it down to 77% because the numbers would not go low enough to give me 14.7 a/f on idle and i ended up running out of fuel (walbro 550hp pump at its limit)

I am going to re-do it again in a few months after i save up some money for a 044 pump and possibly surge tank and a better fuel reg which i will do as a road tune up to 20psi and then more boost will be saved for the dyno soon after.

I agree a full remap is important, I just wonder whether a 50 % setting for 740's is anywhere near enough fuel, it will get it to the tuner but will need more work!

and yes i have had a full tune, thanks for the offer,

I have a apexi pen timer with afr feedback are these very accurate ? seemed pretty good compared to the dyno reading, it sits on 14.7 on cruise,

just for reference Guilt-toy were did your injector setting end up?

[paulr33]

the pfc faq has a better explanation of the injector correction and latency screens

that old stuff you screen captures is from the rx7 with pri and sec injectors

thats only likely to confuse you more, check the pfc faq under advanced tuning (its in my sig)

[180or200]

what is the latency of rb25 nismo 740's?

[GeeTR]

Whoah, i watched 30 views on this thread in 24 hours, then check it now, and 100+ and 10 responses THANKS!

Let me pull the reigns in a little.

Im not so much talking about the precise setting of injector correction nor latency, its if larger injectors generally need a Positive or a Minus latency setting. In the example i gave, a mates SR20 with double sized injectors, the tuner used a minus value, whereas if i read the manual, it should be a positive number made up from the new injector time - stock injector time.. giving a POSITIVE number ( me would have thought)

Thats my question.

Lag times are not directly related to the size of the injectors and are not linear. When you get the injectors flow tested and cleaned they should be able to give you all the relevant info.

Thanks DivHunter, i didn't know one could get a definitive answer of inj lag from a injector flow bench setup ( as i also don't know the exact latency of the SARDs i have)

As for if the latency is more in a larger injector... well i would have thought it was clear that a higher flowing unit, would need a larger hole, and a higher spring pressure keeping the pintle seated, therefore causing more "Injector Latency" Flame away

As for the injector scaling debate, I think I'll scale it as close as I can, to keep close loop on cruise, and then just tune the higher values.

PaulR33, i searched your site solid, though cant find the "advanced tuning" manual

Although Microtech's and other don't have the setting, Haltech and Motecs do, which leads me to believe theres some importance in setting it correctly... even if most multi point / sequential injecton setups go batch fire after 4000rpm.

Please keeps the thoughts comming!!

Q: "Is the setting the Positive delta between the new and stock injector latency times???

M

[DivHunter]

Straight out of the FAQ -

How do I configure larger injectors?

Configuring larger injectors into the PowerFC is quiet simple and takes only a few moments. You need to know the following information before you can continue

Current injector size

Current injector latency

New injector Size

New injector Lag time

Injector Size and Latency (standard units)

Unit Size Latency

RB26 444cc/min 0.772msec

RB25 370cc/min 0.528msec

SR20 (Jap Spec Manual) 448cc/min 0.584msec

Aftermarket New Units 600cc/min 0.810msec

To work out new INJECTOR correction and latency;

Old SIZE / New Size = Correction

Old Latency - New Latency = Latency Correction

John plans to install 600cc injectors into his RB26 VL Turbo. The following figure's are used;

444 / 600 = 0.74 * 100 = 74.0%

0.81 - 0.77 = +0.04 msec

So he would enter 74% for correction and 0.04 as new latency

Once you have switched to larger injectors you should still check your AFR's with a wideband to ensure they are safe and acceptable.

[GeeTR]

Straight out of the FAQ -

Clearly i was feeling a little "special" last night, and looking through the site, not the FAQ.

Well Paul's example is about as clear cut as they get. That, along with the old RX7 manual, plus comments from others... to me thats definitive!

Time to kick some tuner ass

Thanks as always for all thoughts and help!!

M

[Beer Baron]

Whoah, i watched 30 views on this thread in 24 hours, then check it now, and 100+ and 10 responses THANKS!

Let me pull the reigns in a little.

Im not so much talking about the precise setting of injector correction nor latency, its if larger injectors generally need a Positive or a Minus latency setting. In the example i gave, a mates SR20 with double sized injectors, the tuner used a minus value, whereas if i read the manual, it should be a positive number made up from the new injector time - stock injector time.. giving a POSITIVE number ( me would have thought)

Thats my question.

Thanks DivHunter, i didn't know one could get a definitive answer of inj lag from a injector flow bench setup ( as i also don't know the exact latency of the SARDs i have)

As for if the latency is more in a larger injector... well i would have thought it was clear that a higher flowing unit, would need a larger hole, and a higher spring pressure keeping the pintle seated, therefore causing more "Injector Latency" Flame away

As for the injector scaling debate, I think I'll scale it as close as I can, to keep close loop on cruise, and then just tune the higher values.

PaulR33, i searched your site solid, though cant find the "advanced tuning" manual

Although Microtech's and other don't have the setting, Haltech and Motecs do, which leads me to believe theres some importance in setting it correctly... even if most multi point / sequential injecton setups go batch fire after 4000rpm.

Please keeps the thoughts comming!!

Q: "Is the setting the Positive delta between the new and stock injector latency times???

M

there is no rule to say larger injector has a slow response time. you are linking two things that are not directly linked. latencey/lag time/response time is one thing. flow rate (measured in cc per min) is another. Yes GENERALLY a larger injector will have a longer/slower response time which means a + adjustment in the PFC. BUT don't take it as a rule. just find the specs for the injectors you have, and the injectors you want to use and then you can tell me if it is a + adjustment or a - adjustment.