i just got my car dynod a couple weeks ago at 8900miles, the car is stock and always seemed to pull strong (as a Z06 should).
After buying and installing a K&N intake on it it felt a little slower so i wanted to get a before and after dyno done to make sure i wasnt losing power with out having it tuned. To my surprise i was losing a tremendous amount of power in the midrange, and topend too. The guy performing the dyno said it felt almost as if it was detinating. Those numbers came out to 454rwhp and 380tq with a nasty midrange tq curve. we swapped out to the stock intake and the car run much better putting down 473rwhp and 438rwtq bone stock!
heres a pic of the dyno chart (scanner having problems):
Red is stock curves, blue is K&N.
That is odd that it would lose hp. I have heard of several people being around 470 whp and putting headers, exhaust, and intake on and only gaining about 10 whp with all those mods.
Well if it was detonating then it could possibly be that the CAI was letting in so much more air than stock and you said you did not have it tuned that it was leaning out so it was detonating and when the computer sensing detonation it pulls timing till it stops detonating which would result in the MASSIVE drop in power. With the CAI you are letting in more air and the motor does not know how much more fuel to dump in so it leans out. Get it tuned with the K&N and you should atleast come back up to stock power if not a little above.
First off it's super lean. Over 14:1 on both pulls.
The dip in the torque curve looks like the clutch was slipping or something.
Detonation would make the graph very choppy.
From that PERFECTLY FLAT AFR line i would suspect that that particular AFR sensor they are using was not working quite right OR you were SO LEAN that i was maxing out the sensor at 14.75 or so.
Then I would go back to my first comment that with the CAI it needs to be tuned for the extra air that is able to get into the motor. Without the tune it is leaning out so bad that it is detonating which is causing the ECU to pull timing which is dropping your power. Put the K&N back on and tune it and I am sure you will pick your power back up and then some.
From that PERFECTLY FLAT AFR line i would suspect that that particular AFR sensor they are using was not working quite right OR you were SO LEAN that i was maxing out the sensor at 14.75 or so.
Yeah, it is odd, but if they're just layin on the floor or something, they'll read 18:1. I've had several go bad over the years, and I've never seen one lock in on 14:1. If they go bad, they read either 18:1, or nothing.
The OP said in his other thread, that it wasn't in the tailpipe, but like I said, I've never seen one read 14:1 layin on the floor.
Then I would go back to my first comment that with the CAI it needs to be tuned for the extra air that is able to get into the motor. Without the tune it is leaning out so bad that it is detonating which is causing the ECU to pull timing which is dropping your power. Put the K&N back on and tune it and I am sure you will pick your power back up and then some.
That intake wouldn't lean it out so much as to cause detonation. They're pretty damn rich to begin with, and untuned, the new intake would get the A/F ratio closer to what it needs to be.
Besides, the graph looks too smooth to have any amount of detonation.
The formula for correcting to SAE is:
cf=1.18*[(990/Pd)*[(Tc+273)/298]^1/2] - 0.18
Where cf is correction factor, Pd is ambient pressure in hPa, and Tc is ambient temperture in degrees Celsius.
SAE corrects to 77*F and 29.234 in Hg and STD corrects to 60*F and 29.92 in Hg.
If we want to correct to SAE standards and the engine was tested at ambient conditions of 60*F and 29.92 in Hg, (which just happens to be the STD standards) we have:
cf=1.18*[(990/1013.2)*[(15.56+273)/298]^1/2] - 0.18
cf=.95456, which is the correction factor when going from STD to SAE.
The difference when going from STD to SAE will always be ~4.5%...it doesn't depend on the weather.
The MAF will sense any additional airflow and adjust accordingly - you do not need a tune for a different air filter no matter how efficient it may be, that is absurd.
The MAF will sense any additional airflow and adjust accordingly - you do not need a tune for a different air filter no matter how efficient it may be, that is absurd.
Not true. Almost any time you change the intake in front of the MAF, the MAF will need to be recalibrated. Will it be so far out that it's out of the range of adaptability? No. But it will throw it off somewhat. Is this the cause of the power loss in the graph? I highly doubt it.
The MAF will sense any additional airflow and adjust accordingly - you do not need a tune for a different air filter no matter how efficient it may be, that is absurd.
Our MAF is a "sampling" type maf. It does not sense all the airflow, it is calibrated for the stock intake. Change the intake and the calibration is off, it won't be telling the PCM a correct value. You will see your LTFT's go up, maybe enough to set codes and the CEL.
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Depends on the weather.. But most of the time, SAE would be higher.
Ok, but in my case the STD was 9 hp higher. Futhermore, this is the very first time I've heard that the SAE is higher....unless I'm missing something here.
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C6Z stock dyno... Freak??
