Injector duty cycle

**Impala ss sleeper** · 04-14-2012

I have a 2005 impala l67,xp cam,gen v ,northstar tb,3.4 pulley,speed daddy headers,and my injector cycle was at 125 at wot and got 5*knock during high rmp and shift then it would drop down to 2* any suggestions?Oh i still have stock l67 injectors.

**dsmuts** · 04-14-2012

What kind of tune do you have?

**afallucco** · 04-14-2012

As I said in the other thread Any knock is bad even a few degrees. What tuning have you done and do you have someone who can tune the car for you?

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**Impala ss sleeper** · 04-14-2012

hp tuning

**afallucco** · 04-14-2012

Have you done a wideband tune and what's your afr?

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**Impala ss sleeper** · 04-16-2012

have to ask my tuner i think he said around 12?? cont remember not done a wideband yet what should the afrs be

**rynoman03** · 04-16-2012

11.1-11.3ish at WOT

I mean you can go leaner but that's upto you. Sounds like your running too lean!

**Tuner-Extraordinaire** · 04-16-2012

pulley is too small. -- if your duty cycles are 125 you're too rich.

**Impala ss sleeper** · 04-16-2012

yea i bought some 60lbs seimens injectors cheap goin to put them on and tune see what happens

**rynoman03** · 04-16-2012

Ya but he said his tuner said the afr was around 12. That's kinda lean if that's true. With the xp it almost sounds like he can't get enough fuel at 125 inj duty.

**Impala ss sleeper** · 04-16-2012

its too small even with the xp cam??

**rynoman03** · 04-16-2012

I think it's fine i personally think your running out of injector and going lean. I can't see that without a scan though.

**Impala ss sleeper** · 04-16-2012

thanks for your help and info guys goin to install injectors and scan will post more info tomorrow

**Tuner-Extraordinaire** · 04-16-2012

still seems rich 125% duty -- you're def running out of injectors though

**rynoman03** · 04-16-2012

Don't forget you have to change your tune for those injectors. You just can't slap em on without doing anything to the computer. I'm sure you know this but i'm just telling you just in case ya know.

**darkhorizon** · 04-16-2012

Originally Posted by Nixon

still seems rich 125% duty -- you're def running out of injectors though

The 04+ read incorrectly... He is still well within his functional range on that car... a 3.4 pulley with any cam will not max out stock injectors on any GTP... He can command a bit more fuel if he is really lean without hurting anything.

I imagine there is a bunk maf file on there that was loaded for the northstar that is leaning things out (because it was richened too much at idle).

**Impala ss sleeper** · 04-22-2012

installed 60lbs injects duty cycle is at 48% now and AFRs at 11.3 wot but i still get about 6* then it goes back to 1*

**Tuner-Extraordinaire** · 04-23-2012

burst kr.

**afallucco** · 04-25-2012

Originally Posted by rynoman03

Ya but he said his tuner said the afr was around 12. That's kinda lean if that's true. With the xp it almost sounds like he can't get enough fuel at 125 inj duty.

You want around 11.5 afr for non intercooled and 12 for intercooled. In this case he's lean

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