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Discussion Starter #1
I got my car dynoed today and here are the results my pulls were in third and I got 229.6 power/229.4 Torque, with a A/F ratio of about 13 down to about 11.8. My next pull was the best one, I used my NX-cooler kit and pulled 250.4 power/246.3 torque with an A?F of about 13.1 I'll post my sheets on monday when I get to work and use my scanner. Are these numbers ok for a Cobb stg2 with headers,up, and Walbro. My boost in third only got to about 14.8psi
 

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cdvma said:
Those air/fuel ratios are very lean, are you positive those values are correct?
Are you sure they're "very lean"? Most A/Fs I've seen start off near stoichiometric at low engine load/rpm in closed loop to spool the turbo faster, then as load increases you see the ratio quickly move to the mid 11s to upper 10s. 11.8 is on the lean side but not outrageous. If it really ran in the 13s with the NX cooler, THAT'S just plain crazy.

fwiw, i've seen people with cobb stage2 report worse A/Fs, I'd call Trey about it if you were really concerned.
 

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you have a walbro pump? why? unless you have a special map for it, no need even with a VF34 with cobb software... try a stock fuel pump and dyno again
 

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supermarkus said:
Are you sure they're "very lean"? Most A/Fs I've seen start off near stoichiometric at low engine load/rpm in closed loop to spool the turbo faster, then as load increases you see the ratio quickly move to the mid 11s to upper 10s. 11.8 is on the lean side but not outrageous. If it really ran in the 13s with the NX cooler, THAT'S just plain crazy.

fwiw, i've seen people with cobb stage2 report worse A/Fs, I'd call Trey about it if you were really concerned.
They are lean compared to most setups I've seen. Generally its stoich until about 7 psi then shoots down to 10.8 or so (this is on pump gas btw) at peak torque then either maintain that AFR or slide to 11.0 towards redline. 13.1 I would expect to see on high octane race gas or a water/methanol injection kit and 11.8 on regular pump gas is odd.
 

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cdvma said:
They are lean compared to most setups I've seen. Generally its stoich until about 7 psi then shoots down to 10.8 or so (this is on pump gas btw) at peak torque then either maintain that AFR or slide to 11.0 towards redline. 13.1 I would expect to see on high octane race gas or a water/methanol injection kit and 11.8 on regular pump gas is odd.
I saw several A/F curves from when Phil tuned a bunch of local guys. His curves were as expected with a big dip at peak torque but as the graph leveled out they settled to around 11.25 or so depending on the setup. I did see one graph that sat around 11.5 for a while. 11.8 is a bit weird, but if it's not knocking...
I say make some more pulls and get a knock link or det cans to listen for det above 5k rpm.
 

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NX really gives u 20 hp?
 

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your first run is richer than 12:1 at the end of 3rd gear. the second is a bit leaner, but still inside the 12s. the reason it is leaner, is because you chilled the intake air and the dense air is not getting enough fuel.

where it says 13.1:1, what the hell is that measuring? MPH says 63.7... what is important about this MPF and AFR?

it seems like there is a gradual increase in fueling, starting at stoichiometric to aobut 11.8:1? that is of course without the N-tercooler chillin.... i would think that the extra 20 horses is not worth it, if the AFR at +12:1 is dangerous for WRX.
 

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your avatar cracks me up NOTimpressed
 

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Rich10 said:
It looks too lean. I would contact Cobb.
around what AFR would be considered lean on the EJ20?

a lot of tuners for say, Supra, or Skyline, would tune to about 12:1 at WOT.
 

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TurboXS recommended to me that I keep it at 11:1. They suggested that the air:fuel ratio at the torque peak should be dropped to approximately 10.7:1.

Maybe it is OK since you aren't detonating (atleast according to the graphs), but I would definately speak to Cobb.
 

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Discussion Starter #16
Thanks for all your responses, I did call Cobb and showed them my dyno sheets and they said from what they saw that I'm fine and my A/F curve is just like the ones they show when they dyno. Again thanks for all your helps guys :)

Time for my stg4 upgrade this weekend:D
 
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