Hey guys i have a question. I just installed my AEM Wideband and according to this thing at idle i am around 12.3:1 air fuel ratio. Was wondering if that is good or is that still rich for an idling motor. When i first installed it and my fuel pressure was at 50psi at idle. the air fuel was at 11.3 Now i have put the fuel pressure to 45 psi. and the air fuel is around 12. Also when im cruising around its around 13.5. Is that good? or should i turn the fuel pressure down a bit more.

 

Hey,

From what my buddy explained to me on his dsm from what I understand you set your fuel pressure to 43.5 at idle on a normally warmed up car without the vacuum line connected to the FPR once thats set you reconnect the vac line and leave it.

I suppose you can run a higher fuel pressure within the injector's tolerances and the output of your fuel pump so you can fudge more fuel at a higher duty cycle also but double check with other people if that's the case.

as for AF ratio at idle you should be fluctuating between X and Y and your goal is 14.7:1 at idle and cruise

So to answer your question 12.3:1 at idle is way too rich for any engine wait till the engine warms up before you start adjusting **** at least wait till the radiator fan comes on and off then I believe according to the Honda manual the engine is warmed up and ready to be tinkered with.

I guess I should ask what tuning package are you using? Why do you have a FPR? and why do you have a Wideband?

 

do you have an engine management?

fuel pressure has an effect on every aspect of driving so be careful trying to tune with a pressure regulator.

12 afr is very rich for idle. 14.7 is the "perfect" air to fuel mixture aka stoichiometric.

please read the rules of this section of HT located in the "tuning faq" if you plan on posting here.

 

ah, you know what. im gonna contradict you guys on the idle afr. when i was over at evans tuning jeff and i had a conversation about idle afr. my car left there idle in the 11s and he said it wasnt too big of a deal. it ran like this at idle for thousands of m iles no problems.

currently i idle my car in the 12s and 13s. stoich ratio of 14 and up idle like dogshit on my injectors

 

Blackeg


I suppose it will idle fine but why not have it idle with the correct AF to avoid burning up wasted gas?

my 2 cents..

 

with an afr of 14.5, it idles like ****. the rpms fluctuate and so does the afr. everything is smoothest in the 13:1 range. im running neptune rtp and 880cc precisions.

even though the afr is rich, keep in mind how low the duty cycle is at idle, and usse that with the flow rating of the injectors to see how little fuel you are really dumping into the cyls

 

14.7 might be optimum for burn, but the afr the engine likes at idle is going to depend on the duty cycle of the injectors, size, atomization, port size and velocity, etc... Basically whatever makes it smoothest.

 

well emm not to get side tracked here can one simply reduce duty cycle and increase fuel pressure to get the same result? granted your within the tolerances of your injectors for maximum pressure?...

If so is there any adverse effects doing this tweak? or is this even done?

I understand the solution would get the properly sized injectors for your project/goals.

Oh actually on topic now, didnt neptune have some sorta voltage compensation so you could theoreticaly get below 1% duty? in cases where your injectors are so large you cant tune idle fuel only top end? how do you generally do that on silly cars that have 1500cc or 1000cc injectors at idle???

THANKS

Not to thread jack or anything but the question has 50% merit to this topic