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Hello All,

I have a 382 and i am a noobie to tuning. Here is a question for you. With my wide-band O2 sensor hooked up to the exhaust, while under no load cruise, under 4000 RPMs the AFR is a steady 14.1. As soon at the RPMs get to 4000 the AFR drops immedeately to about 10.7. :screwy: The AFR will also drop to about 10.7 around 3200 RPMs, under a heavy load. What tables in the PCM should I be looking at to change? Any ideas?
 

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Geez, I am probably not going to be much help here, but here is what I know.

These cars tend to detonate around 3800-4000 RPM (Around torque peak). Back in the older LS1 cars that is where the computer would pull timing. My guess would be that the CPU is seeing a lean condition and dumps fuel around the spot that the car would be likely to detonate.

Post this over on LS1 tech, there are a bunch of technical guys/gals/vendros that post over there.
 

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4000 rpm dings in my memory as the point at which the PCM is no longer blending the VE table and strictly relies on the MAF.

AFR dropping is normal when entering PE mode, not sure if that's what you mean by "Under a heavy load".

I don't know how much help this is for you, but I thought I'd mention it.

John.

PS: I have no idea what a 382 is, so that might be a good clue to ignore what I'm saying. :)
 

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I just ran an EASE on my 01Z and if I recall correctly what the tuner said to me, 10.7 certainly isn't "rich", I believe it considered lean, way lean.
I noted my 01 at about 5200-5500 rpm seems to lose power because the injectors can't keep up with the demand so timing is adjusted accordingly and a few misfires occur.
I am installing the SVO 30lb injectors in the Z06 in about a week, that will help according to the tuner, then a good tune will hone things the way they should be.
Perhaps you need larger injectors to accomodate your power demand/
Just a though, of course I realize my slightly modded LS6 is not a 382 so feel free to ignore everything i just wrote.
 

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You can't diagnose this issue with the information you have. If you've got EFILive or similar, you should data log and see what everything is doing. MAF, Injector timing, fuel trims, Ignition timing, etc..
 

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NavyPhrog said:
I just ran an EASE on my 01Z and if I recall correctly what the tuner said to me, 10.7 certainly isn't "rich", I believe it considered lean, way lean.
I noted my 01 at about 5200-5500 rpm seems to lose power because the injectors can't keep up with the demand so timing is adjusted accordingly and a few misfires occur.
I am installing the SVO 30lb injectors in the Z06 in about a week, that will help according to the tuner, then a good tune will hone things the way they should be.
Perhaps you need larger injectors to accomodate your power demand/
Just a though, of course I realize my slightly modded LS6 is not a 382 so feel free to ignore everything i just wrote.
10.7 is ritch -> the lower the # the leaner. Most tuners shoot for 12.8->13.0: Air to fuel ratio.

12.8:1
First number 12.8 is air
second number 1 is fuel
as the first number rises it means you are getting more air per the same volume of fuel and the engine becomes more lean.
 

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I agree 100%.

2nd comment is that if you are new to tuning I would NOT recommend playing with the AF tables, leave that to a trained professional. AF, timing and a variety of other parameters work together to optimize the performance of your motor while not risking detonation or other issues.

And 10.7 is very rich, but not unheard of in factory tuned cars, that is why going with a 12.8 or so (with appropriate timing etc) can yield you 10 RWHP or more with no mods and very little risk. I would recommend getting any mods completed you plan on the car, then have a pro tune it.

Les




niphilli said:
10.7 is ritch -> the lower the # the leaner. Most tuners shoot for 12.8->13.0: Air to fuel ratio.

12.8:1
First number 12.8 is air
second number 1 is fuel
as the first number rises it means you are getting more air per the same volume of fuel and the engine becomes more lean.
 

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Thanks for the explanation of the rich/lean. I must have misunderstood the tuner. Mine is running rich then as well.
I am certainly going to leave the tuning to the pros, once I get a couple things done, i.e., 30lb injectors/160 deg t-stat/exhaust.......for now.
Thanks again for the education.
Jim
 

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When you upgrade the injectors you will need a retune. Sorry to state the obvious if you already knew.

Les


NavyPhrog said:
Thanks for the explanation of the rich/lean. I must have misunderstood the tuner. Mine is running rich then as well.
I am certainly going to leave the tuning to the pros, once I get a couple things done, i.e., 30lb injectors/160 deg t-stat/exhaust.......for now.
Thanks again for the education.
Jim
 

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Thanks Les. I figured a retune would be required to take full advantage of the new injectors. My plans are to install the injectors, the 160 deg t-stat, change the plugs and wires and install a catback and then re-run an EASE, have that interpreted by a pro and get a tune based on that EASE.

Do you have any other recommendations I should consider?

Thanks again for your help and input.

Jim
 

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What are your average LTFTs?
If they are 15 plus the PCM is adding fuel when you go into open loop. The LTFTs add fuel in open loop according to what was recorded in closed loop. The stoich value is set just below 14.7 and this is where the PCM trys to keep the AFR in closed loop. When you go in to open loop the AFR is dictated by the PE table plus the extra fuel added by the saved LTFTs.
The PCM goes into open loop under load and also preset throttle positions at different rpms.

I use HP Tuners and the scan tool lets you clear the LTFTs.
Try that before you take a ride and see if your AFR is still low.
 

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Tom
Can I email you the EASE read I got so you can give me your input on it?

Jim
 

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NavyPhrog said:
Tom
Can I email you the EASE read I got so you can give me your input on it?

Jim
Can you convert your ease scan to a .xls or .csv file?
 

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I am in a similar position. I just got my s/c ls6 back together and it now has a lowered compression ratio etc. I plugged in my Genisys Scan tool and recorded information during boost and off boost. If I post the info can someone help me read it and make sure everything is good? Here are the highlights I have recorded

TP Angle
rpm
ect
Spark +/-
Knock retard
map psi kpa
map voltage
maf
fuel pump pressure
fuel table
bank 1 sensor 1 o2
bank 2 sensore 2 o2

Will this data help me have a general idea of how the engine is operating? It has a vortech program isntalled I belive, just as a fyi.

HELP!

Thanks,

Dustin:)
 
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