Duty cycles

1slow370 · 06-14-2014, 08:40 PM

Im curious if anyone has logged duty cycles from the factory injectors? what was your duty cycle and how much power did it make? if you know the afr that would be great too. My car is being tweaked and i don't know power yet because the afr's need to be dialed in but Im at 96% duty with 11.8 afr at 7700rpm and 50psi fuel pressure on factory injectors with a 255lph pump right now.

Jordo! · 06-14-2014, 09:18 PM

Do you know max flow on the OEM injectors? That RC calculator should get you in the ball park on an answer if you know the fuel pressure difference from stock.

Another possibility, is injector scaling -- it may be there is more flow to be had, but OEM values for the injectors in the fueling maps end up giving you a higher claimed duty cycle that the OEM injectors are actually using.

Also, your AFR's sounds about right for your boost levels -- are you looking to run more boost or enrichen the tune?

BTW: I am very aware that you are much more knowledgeable than me on many or all of these types of issues, so if I'm mentioning obvious/irrelevant things, chalk this up to I mean well, but my background in tuning and such is greater than some but far less than others...

anyway, just throwing out ideas to try and help

1slow370 · 06-14-2014, 10:07 PM

0 boost pressure bro, it's got to go leaner. I do not know the exact flow rating on the oem injector, i can try to look it up. as we start getting more and more higher horsepower na cars it would be nice to know how much power the factory injectors can actually support.

Jordo! · 06-15-2014, 05:28 AM

Quote:

Originally Posted by 1slow370

0 boost pressure bro, it's got to go leaner. I do not know the exact flow rating on the oem injector, i can try to look it up. as we start getting more and more higher horsepower na cars it would be nice to know how much power the factory injectors can actually support.

Oh, ok -- I missed that!

I think I tried to reverse engineer this once before -- see here

Flow rates for the stock fuel injectors & MAF sensors?

I think that is probably in the ballpark -- if you have the p/n you can probably trace it back to a specific Denso (or whatever) which should have that info listed.

jrb55gh · 06-15-2014, 10:21 PM

Here is an ECUtek data log for a full throttle pull through 3rd gear on my stock 370z 7AT.

The injector duty cycle at about 7300 rpm shows at 86% which is about correct for the indicated injector pulse width of 14.12 msec. in 16.4 msec for 2 engine revolutions. If the engine power is increased with boltons by about 30 hp it would seem that is near the limit for the stock injectors unless a/f ratio is leaned out. Mine is currently set at a conservative ~12.0.

06-14-2014, 08:40 PM	#1 (permalink)
1slow370 A True Z Fanatic Join Date: Aug 2009 Location: In the D Posts: 3,732 Drives: v8 74 260z ;) Rep Power: 7250	Duty cycles Im curious if anyone has logged duty cycles from the factory injectors? what was your duty cycle and how much power did it make? if you know the afr that would be great too. My car is being tweaked and i don't know power yet because the afr's need to be dialed in but Im at 96% duty with 11.8 afr at 7700rpm and 50psi fuel pressure on factory injectors with a 255lph pump right now. __________________ ANSWER PRICE LIST Answers - - - - - - - - - - - - - - - - $0.75 Answers (requiring thought) - - - - $1.25 Answers (correct) - - - - - - - - - - $12.50

06-14-2014, 09:18 PM	#2 (permalink)
Jordo! A True Z Fanatic Join Date: May 2010 Location: nirvana Posts: 6,394 Drives: 2023 NATM Rep Power: 417	Do you know max flow on the OEM injectors? That RC calculator should get you in the ball park on an answer if you know the fuel pressure difference from stock. Another possibility, is injector scaling -- it may be there is more flow to be had, but OEM values for the injectors in the fueling maps end up giving you a higher claimed duty cycle that the OEM injectors are actually using. Also, your AFR's sounds about right for your boost levels -- are you looking to run more boost or enrichen the tune? BTW: I am very aware that you are much more knowledgeable than me on many or all of these types of issues, so if I'm mentioning obvious/irrelevant things, chalk this up to I mean well, but my background in tuning and such is greater than some but far less than others... anyway, just throwing out ideas to try and help __________________ Enjoy it. Destroy it.

06-14-2014, 10:07 PM	#3 (permalink)
1slow370 A True Z Fanatic Join Date: Aug 2009 Location: In the D Posts: 3,732 Drives: v8 74 260z ;) Rep Power: 7250	0 boost pressure bro, it's got to go leaner. I do not know the exact flow rating on the oem injector, i can try to look it up. as we start getting more and more higher horsepower na cars it would be nice to know how much power the factory injectors can actually support. __________________ ANSWER PRICE LIST Answers - - - - - - - - - - - - - - - - $0.75 Answers (requiring thought) - - - - $1.25 Answers (correct) - - - - - - - - - - $12.50

06-15-2014, 10:21 PM	#5 (permalink)
jrb55gh Base Member Join Date: Mar 2013 Location: DFW Texas Posts: 149 Drives: '13 370z black 7AT Rep Power: 12	Here is an ECUtek data log for a full throttle pull through 3rd gear on my stock 370z 7AT. The injector duty cycle at about 7300 rpm shows at 86% which is about correct for the indicated injector pulse width of 14.12 msec. in 16.4 msec for 2 engine revolutions. If the engine power is increased with boltons by about 30 hp it would seem that is near the limit for the stock injectors unless a/f ratio is leaned out. Mine is currently set at a conservative ~12.0. Jordo! likes this.

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