The car fired up immediately. The install was so perfectly done there was not a single hick up, surge or any computer error code. I drove around with the OEM calibration and to be honest I was a little disappointed. It drove almost like stock at part throttle and Roush tune really kicks the power in when you go WOT and reach about 3-4k rpm. Roush tune lived only for 30 mins or so, until I drove home from Garage Dutli to upload the VMP tune from the legendary tuner Justin Starke.
VMP Tune (http://www.vmptuning.com/)
I haver been reading about VMP and their owner, master tuner, Justin Starke for a long time. He is one of the most reputable tuners who specializes in TVS style blowers. He has tuned 100s of Roush cars and swapped 11-13 GT500 factory twin screw with his own VMP TVS supercharger since years.
From his website you can buy a "remote tuning" for $350 which saves you a ton of money from doing actual dyno tuning in Europe which will easily cost you close to 700-1000 Euros! The way Justin works is; he sends you a tune that is made for your specifications and asks you to datalog the car using SCT's LiveLink logging software. All you need to do is datalog idle, rpm range in neutral gear and do either a 2nd, 3rd or 4th gear street WOT pull. The higher the gear, the better.
Now, the difference between Roush OEM and VMP performance tune is day and night. The car was a complete different beast and so much more responsive with VMP's tune. Not to mention, Roush is extremely conservative tune that hides away an easy 60-80hp. VMP releases these hidden horsepower without a pulley change. It is estimated that a 575hp Roush OEM package is easily upgraded to 630-640hp without any pulley swap.
The car has absolutely zero driveability issues. Idle is smooth, part throttle has no surge or bucking issues. Throttle response was a little snappy at first but I rapidly got used to it. The power level is insane. Burning tires is almost unavoidable in 2nd gear and even sometimes in the 3rd.
I will soon dyno the car to proove the results but here take a look my datalog after I uploaded the VMP tune:
AFR Log
The AFR on a supercharged mustang is usually set to low 11s, typically 11.0-11.2 range to be on the safe side with the boost while maximizing power. My AFR was measured starting at 11.7 at 1500rpm, dropped to 11.2 as of 2500 and remained constant almost all the way to the top of the rpm range where it dropped to 11-11.1 above 5500rpm. Just as expected and just as how it should be.
Spark Advance
Here is the graph of my spark advance timing. The thick blue line is the timing where the thin yellow line is the knock sensor, starting at zero right at 48th second.
In the recent days, I learned so much about how knock sensors in 11-13 Mustang GT and Spark timing work together. I always thought that the parameter in SCT livelink software that measures knock sensors, was actually indicating whether the car had a knock or not. Which is completely false. The Knock sensor, whether being zero, a + or - number, indicates if the PCM is commanded to advance or retard timing. If the knock sensor reads a positive value like +1, it means it is commanding the PCM to retard the spark timing by 1 degree because it actually measures less than ideal conditions to make extra power. Retarding the timing causes cylinder pressure to drop and helps avoiding a possible detonation. If the knock sensor reads a value like "-2" it means, the ideal conditions exist and spark timing can be advanced up to 2 degrees to produce more power.
A good performance tune must leave the knock sensors on and must ensure that spark timing is almost instantly adjusted as knock sensors command. As you can see in my graph above, the "yellow" knock sensor drops to -2 and commands increasing the timing which is shown in thick blue line. The timing is advanced up to 17-18 degrees as commanded by the knock sensor to make use of the most power.
One of the most feared reasons why a supercharged engine dies is when the PCM is not able to retard the timing almost instantly when Knock sensor orders to. The reasons can be; a) the knock sensors are left off by the tuner b) the tune and equipment i.e. injectors, spark plugs etc. used are not properly installed so that even though when knock sensor commands a retard, it takes long time for spark to be actually retarded. It is matter of miliseconds a detonation can occur and destroy the engine.
Now take a look at the zoomed section of my Spark advance graph below.
At 49th second, the yellow line goes positive to +0.5. Which is the knock sensor commanding the spark to retard by 0.5 degrees as the ideal conditions for making extra power at this second do not exist. The command for retard does not mean anything bad. It only shows that at that moment, all the factors that effect horspower generation like fuel condition, supercharger intake temperature, air intake temp, fuel pressure, injectors, cam timing etc. are in an overall system condition that requires timing to be retarded to protect the engine. This happens in almost less than 1/3 of a second.
Now, look at the spark advance line in thick blue. You can see that, immediately, how the timing is retarded by 0.5 degree as knock sensor commanded at the same time. VMPs tune is designed to retard timing up to 6 degrees when needed and only increase by 2 degrees if possible for performance. You can also see in the first spark timing graph that how timing is advanced to max 18 and kept there so that the pcm does not continue advancing timing until it causes detonation. This for me is a good proof that the car is properly tuned and all the sensors in it are working in perfect order to keep the engine safe.
I have heard several stories of destroyed engines and most of them were because either knock sensors were off or the spark was not retarded when needed even though knock sensors were commanding to.
Now I am counting days to take the car to a dyno shop and see how much are the final hp/torque figures.
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