I analyzed 5 C5s LAPD added high priced mods and dyno tuned. The data shows the reported performance gains bloated and lousy tunes.

Mods were AFR heads, CAM, LG headers, vendor claims larger injectors but PCM is commanding those injectors over 23 mSecs on time yet still reporting unsafe lean condition.

Received a PCM from a '04 Z06 that had several mods done to it and the vendor claiming like 450 RWtq.
Customer had issues that the car was not performing well and even had 3 other vendor tune for the mods but still the engine was not producing the numbers the vendor claims.

Now having his PCM I downloaded the PCM flash to find a very bad tune as shown below just some of what I found to be wrong with the tune

Where the Z06 stock has about 22 degrees of timing under engine load yet this higher 10.9:1 compression engine was tuned for 31-34 degrees of timing !
Add the fact they programmed PCM if there was knock to ignore it and set the torque managment to 639 ft/lbs when engine is producing around 400 so TM was also turned off.
The AFR for PE and WOT was set way too lean and the rev limiter for a stock engine was set at 7000 RPMs !
Not bad enough but they screwed around with VE tables causing misfires at low engine loads and knock at high loads.
Add this all up and long term this engine would not only continue to be a low performer but would have internal damage to how this was "let's guess and see if this works" tune where customer was paying as much as $650 for a dyno tune not once bu multi times.

Clearly the tuning methods they used they picked up from other forums where people who tune their own cars now thik they are tuning pros with stupid notions on how to properly tune.



Lots of knock and misfire.
Hugh lean conditions even at ilde 25% lean
Left head leaner then right head.
I suspect leaking intake or bad heads as to valve guides or incorrect injectors being used.
Also since left is leaner then right head I suspect wrong header gaskets were used.



Here is results of BEFORE I tuned and then AFTER 1st cut of tune after car was driven several hundred miles after the tune.

All the knock and misfire is gone. It now has correct PE/WOT timing.
Keep in mind the engine compression is right around 11.0:1 and even using stinking CA 91 octane smog gas and still after tune no knock.

Even though the after tune was only a 91 MPH testrun verus the 158 MPH before tune we can see the good gains in HP and Tq after the tune and would have been higher values if this testrun would have also gotten to higher speeds.

Once customer does one more testrun I will tweak the tune to make this a solid good overall tune that will work well in winter or summer temps

So this again shows that a tune done via analyzing the PCM's OBD-II data collected from a realworld testrun on the street gets a good gain up and beyond what the super dyno tune did and also shows you gain more being slightly on the lean side and not rich fuel trims.



I analyzed the Ease recording from another of these LAPD C5s and testrun shown in part below :
As seen customer went to 158 MPH and 6,900 RPMs which I think is the tuner set the rev limiter too high for long term engine life.

In short this engine is not producing the rearwheel numbers the vendor told you
Being the head work and now having 10.9:1 compression on this '04 Z06 having just under 30 degrees at WOT is not a good thing.
Notice at times using the Vararam the intake air temps went up tp 104 degrees when outside temp was 60 degrees. Also the maximum air the engine was burning was 42 lbs/min which is what a stock C5 eats (628 CFM)

At the low end there is a bunch of multi misfires which causes PCM to yank timing and at the other end of high engine load there is ping which also yanks out timing

Its a shame that this customer had this '04 Z06 tuned 6 or more times when its the tuning that is not correct but in any case there is 100 HP missing then what LAPD tolf the customer.