AFR question

[Darwin's 8]

I had my car dyno'd this weekend cause I was curious to see exactly where I'm at after the 272/272 cams and tune from Justin. It pulled 283 hp and 301 ft lbs in the initial run. He told me i'm running pretty rich (around 10:0). He made a quick adjustment with my SAFC and leaned it out to about 11:3 and it pulled 296 hp and 298 ft lbs. I told him thats great and all but I wanted it zeroed out because I didn't want it interfering with Justin's tune.

Now like I said in another thread I'm happy with the custom tune I got from Justin. Curiosity is getting the best of me. My question is which AFR sounds better to guys?

Would leaning it to 11:3 hurt anything or should I just leave it?

[JustDSM]

No.. 11.3 is good to go.. I'm surprised its running that rich.. I'd like to have a boost leak test done on the car to verify that you're not venting measured airflow somewhere. I know I left it a bit rich since the fuel pump was the wrong one and we didn't install one.. Did you by chance get the correct one and put it in? That would cause you to run quite a bit richer than what I dialed you in for.

I'd have to pull your logs back up, but I usually tune pump gas between 11.3-11.5:1

If something's a stray I'll re-correct that AFR once we can figure out why the drift in AFR.

BTW: Where was this dyno'd?

{EDIT}
Another thing that stands out.. Being that he used the SAFC to lean out the mixture (which by nature adds ignition timing) and you lost torque hints to me that it might be knocking some in the peak torque region.. I'd back off the correction there for the time being until I know what's happening here.
{/EDIT}

[Darwin's 8]

I don't remember exactly what you dailed me in at but I do remember you saying you were going to leave it a little rich. I have not installed the fuel pump or anything since we did the tune. On the dyno sheet it's showing at 3000 rpms the AFR is at 12:0 and drops to 11:2 by 4000 rpm, then it tapers down to 10:0 by 6000. It actually dips into the 9's around 6500 which sounds really rich to me. This is why I wanted to ask you before I did anything. Even though the dyno was showing more power I did not want him tampering with your AFRs.

I got it dyno'd at Trenz Motorsports in Denver.

What should we do?

[JustDSM]

11.2:1 sounds about right for where I left you. I left it on the richer side of what I normally do for the reasons we spoke about.. However it's obviously a bit richer after 4K than I would like. Quite a bit actually. I'm certain I didn't let you leave running that rich. Hmm..

I'd most definately like to correct this. When would be good for you to meet me somewhere in north Denver (Ft Lupton exit)? I'll come down and get you fixed up and check for a possible leak.

I definately can't let you run around that rich, especially while I'm so poor

[Darwin's 8]

When ever is good for me. You let me know when your free and I'll be happy to meet you. I wouldn't mind compensating you for your time also.

[JustDSM]

No way man.. You've already done that I stand behind my services/product and this is just part of taking care of the guys who take care of me. You don't owe me anything buddy.

I've gotta say.. I'm pretty happy with the numbers you made considering you're still on stock boost control. We'll see what's up and maybe we can't squeeze a little more out of it

PM me your number (I don't think I've got it saved) and I'll get ahold of you. I should have some time tomorrow afternoon if that'll work for you..

[Darwin's 8]

Well I don't get off till 4 or 5pm but if thats too late we may have to meet up on a weekend or something. I'll PM you my number in the mean time. Thanks for your help man.

[JustDSM]

No, actually that's perfect for me. How about 6-6:30?

[Darwin's 8]

6 should work depending where you wanted to meet. I'm not sure where the fort lupton exit is.

[JustDSM]

I want to say its exit 235... Don't quote me, but its just north of Westminster right off I-25

[Darwin's 8]

Sounds good to me. Name the spot. Any gas stations or any thing right there that are easy to see from the highway?

[JustDSM]

Yep, there's one on the west side of the exit.

[Darwin's 8]

It looks like exit 235 on mapquest. Looks like i'm getting off at 4:00 today if you want toget together an hour earlier. But if that conflicts with your schedule we can still meet at 6:00. Call me up today and let me know.