how to command richer part throttle AFR

[WILYUMZ1]

my inj Pw min is still at factory set point of .8 ms with the factory injectors. I haven't seen the need to change it yet but who knows in the future it may be necessary, it may also explain why the pcm seems to pull more fuel at the low end of the table (aircharge of 0-.20 and rpm less than 1200)

[chizzle1]

i think the suggestion about the O2 sensors getting hit with unburned fuel from the cam overlap causing issues at idle is very accurate, when I tune closed loop I can get everything dialed in except for idle.
Tried upping the VE tables and reducing the fuel mass by 5% to richen it up, still lean at idle. Once the rpms get up to 1300 the AFR is perfect.
Open loop might be the way I have to go, tuning part throttle is a pain in the ass though...

[06300CSRT8]

chizzle you are right, but a bit off on the result of what that means. It is a false lean as a result. Remember o2 sensors don't read the amount of fuel, they only read the amount of oxygen. overlap causes both excess fuel AND oxygen to go in and out of the cylinder. So even though you may seem like no matter what you can do you cant get it to richen up, use your eyes and smell test too. Noticing the horrific fuel smell still bellowing out the exhaust even though you're "reading" lean? Target an air fuel ratio of 15.5 at idle and see how it behaves and smells.

[chizzle1]

chizzle you are right, but a bit off on the result of what that means. It is a false lean as a result. Remember o2 sensors don't read the amount of fuel, they only read the amount of oxygen. overlap causes both excess fuel AND oxygen to go in and out of the cylinder. So even though you may seem like no matter what you can do you cant get it to richen up, use your eyes and smell test too. Noticing the horrific fuel smell still bellowing out the exhaust even though you're "reading" lean? Target an air fuel ratio of 15.5 at idle and see how it behaves and smells.

the wideband is reading 16-17 and it sits at the collector, so maybe it's out of range for the factory narrow band? I dunno, in open loop i can get it to read right around 14 which is where is seems to be happy idling at.

[06300CSRT8]

Gotcha. When it reads 16-17 in closed loop, what are the fuel trims looking like?

[chizzle1]

Gotcha. When it reads 16-17 in closed loop, what are the fuel trims looking like?

at cold start it reads +5 - +7, then when it warms up it reads -3 to -7.
idles at 800 with 55 kpa registered on the map sensor

[chizzle1]

well, I have the WOT tables dialed in - 0 to .5 degrees of ST KR and 12.3-12.7 AFR across the RPM range.
Still smells a little when idling in traffic but other than that seems to be running well.
I have went so far as to enter negative cells in the PT and WOT timing trying to get rid of the ST KR I get when short shifting or when cruising in 6th gear.
I think it's a combination of the compression ratio and too much engine load at too low of a rpm.
To mitigate this from happening I just keep it in 5th until I'm traveling at 80+ mph.
If the RPMs are above 1800 there is no KR.

[Hemituna]

What are your cam specs and install degs??

[chizzle1]

It's a Howard's 786965-13. Intake duration at .050 231, exhaust duration at .050 237, just under .600 lift.
I installed it neutral as per the cam manufacturers instructions, it has four degrees of Advance ground into it.
https://howardscams.com/i-24077524-h...-camshaft.html

[Hemituna]

Probably a little advanced with 11:1 comp and causing the low rpm kr.

It's a Howard's 786965-13. Intake duration at .050 231, exhaust duration at .050 237, just under .600 lift.
I installed it neutral as per the cam manufacturers instructions, it has four degrees of Advance ground into it.
https://howardscams.com/i-24077524-h...-camshaft.html

[chizzle1]

Probably a little advanced with 11:1 comp and causing the low rpm kr.

Are you suggesting I pull it apart and put a retard eccentric on the timing set? When I degreed the cam the intake Centerline lined up with what the cam card said so I thought it was good to go.
Or are you suggesting that the setup is not designed to run at low RPMs?

[Hemituna]

If it bothers you enough
It is a little late now but this is somewhat of a common issue.
It is easy to remedy on the VVT stuff but figured the info might help others with fixed cams to avoid this.
I most often see too much camshaft and/or installed too much advanced and what you have described is exactly how they act.

Are you suggesting I pull it apart and put a retard eccentric on the timing set? When I degreed the cam the intake Centerline lined up with what the cam card said so I thought it was good to go.
Or are you suggesting that the setup is not designed to run at low RPMs?

[chizzle1]

If it bothers you enough
It is a little late now but this is somewhat of a common issue.
It is easy to remedy on the VVT stuff but figured the info might help others with fixed cams to avoid this.
I most often see too much camshaft and/or installed too much advanced and what you have described is exactly how they act.

It doesn't bother me that much lol.
Do you think a cooler heat range plug would help?

I am going to try pulling more timing from 1500-1700 rpm @ 60-75 kpa.
Unfortunately that is the rpm range when in 6th at 70-ish mph. I'm surprisingly still getting 16 city and 24 highway mpg.

[* _ *]

try higher octane and if it lessens the kr, then a colder (less protruding porcelain) range might be helpful.

[chizzle1]

try higher octane and if it lessens the kr, then a colder (less protruding porcelain) range might be helpful.

I'm running 93, ill put a bottle of torco in and see if that helps.

[* _ *]

I'm running 93, ill put a bottle of torco in and see if that helps.

If you can locally get 104 or 110 unleaded; Run the 93 as low as possible and add 5 gallons of the 110 unleaded to the tank. That'll either provided you with results or just burn some cash and smell good in doing so.

[chizzle1]

If you can locally get 104 or 110 unleaded; Run the 93 as low as possible and add 5 gallons of the 110 unleaded to the tank. That'll either provided you with results or just burn some cash and smell good in doing so.

it's a 45 minute drive each way to get race fuel at the strip. I'll try it with torco to 1/2 tank of fuel first, should bump 93 to 95-96.

[chizzle1]

is it normal for STFTs to be effecting WOT fueling? I was doing adjustments this weekend and noticed I started getting +2 - +3 in the 95 & 100 cells during WOT pulls. I tried adding +3 in the VE tables and it went up to +5 on the next log. WTF?
I thought WOT was open loop, but I guess the PCM still tries to adjust fuel trims. It doesn't seem to be effecting the AFR much, it's still 12.1-12.3.
Do I have to tune open loop to eliminate STFTs at WOT?

[06300CSRT8]

Closed loop trims will carry over to open loop if you have consistent long term fuel trims close to where you transition to WOT.

Make sure to clear adaptives in between logs

[chizzle1]

I clear the adaptives after I make changes to the tune. the closed loop trims should be erased when I clear the adaptives.