Justin@VMP
September 25th, 2007, 10:47 AM
I will be testing and documenting various GT500 induction system modifications. For the purposes of this article the "intake" can be thought of as the portion between the throttle body and air filter, consisting of some tubes, a mass air meter housing, and filter.
Part 1 will cover the K&N engineering full replacement intake.
GT500s are very sensitive to heat and weather conditions, so each time I do testing a new "baseline" is done. In this case, the baseline is a VMP performance tune with completely stock intake and stock pulley, gains are then compared from there.
K&N has been claiming you can bolt on their intake and gain 53HP, with no tuning. This is somewhat correct, but I would not recomend it at all.
The KN intake, just like other intakes on the market, makes more power by increasing the size of the MAF housing and reducing the restriction on the inlet side of the motor. This larger MAF housing results in the car running much leaner (bad).
Dyno run 1 shows the results from a stock car with just a tune.
Dyno run 9 is made with the KN intake, stock tune, and stock pulley, notice the A/F is nearly 15:1.
http://www.vmptuning.com/GT500/3knuntuned.jpg
Dyno run 15 is with a stock car and just a tune
Dyno run 19 is wit the KN intake and VMP custom tuning, notice the safe A/F and 16RWHP gain.
http://www.vmptuning.com/GT500/3kntuned.jpg
The car later made 532RWHP with a 2.6" pulley, on par with what it should make given the warm summer conditions we are having right now in Florida.
Final thoughts:
The K&N intake performs just as well as other intakes on the market. It is a well thought out kit that is very competitively priced.
http://www.vmptuning.com/GT500/3knfullpic.jpg
Edit: more info 6/17/08
The graph below shows what happens if you let the computer learn a little bit before doing a WOT pull with the K&N intake and no tune. This is how K&N is able to claim that the product works, while in reality it's total trickery of the PCM and not a good idea at all.
K&N is relying upon the factory computer to apply a Wide-Open-Throttle Air/Fuel correction, based on learned part throttle A/F corrections. The comptuer can only learn at part throttle when it's closed loop and relying upon feedback from the O2 sensors. At WOT its running open loop and can't actively learned, just use corrections from closed loop.
As you can see, it does not do that great of a job of learning. The A/F is still lean at low RPM and not very straight.
Where does all the extra power come from? K&N probably does not even realize this, but without properly tuning for the intake, you totally screw up the load calculation. The computer see much lower load with the intake, ends up on much lower row on the spark table, and runs a ton more timing. You've effectively totally screwed up the spark table, and while it does have the effect of adding more spark and making more power, it does not do so in a correct fashion.
When the K&N intake is properly tuned for it makes more power and you get a safer and more consistent A/F ratio.
http://vmptuning.com/GT500/3knlearned.jpg
Part 1 will cover the K&N engineering full replacement intake.
GT500s are very sensitive to heat and weather conditions, so each time I do testing a new "baseline" is done. In this case, the baseline is a VMP performance tune with completely stock intake and stock pulley, gains are then compared from there.
K&N has been claiming you can bolt on their intake and gain 53HP, with no tuning. This is somewhat correct, but I would not recomend it at all.
The KN intake, just like other intakes on the market, makes more power by increasing the size of the MAF housing and reducing the restriction on the inlet side of the motor. This larger MAF housing results in the car running much leaner (bad).
Dyno run 1 shows the results from a stock car with just a tune.
Dyno run 9 is made with the KN intake, stock tune, and stock pulley, notice the A/F is nearly 15:1.
http://www.vmptuning.com/GT500/3knuntuned.jpg
Dyno run 15 is with a stock car and just a tune
Dyno run 19 is wit the KN intake and VMP custom tuning, notice the safe A/F and 16RWHP gain.
http://www.vmptuning.com/GT500/3kntuned.jpg
The car later made 532RWHP with a 2.6" pulley, on par with what it should make given the warm summer conditions we are having right now in Florida.
Final thoughts:
The K&N intake performs just as well as other intakes on the market. It is a well thought out kit that is very competitively priced.
http://www.vmptuning.com/GT500/3knfullpic.jpg
Edit: more info 6/17/08
The graph below shows what happens if you let the computer learn a little bit before doing a WOT pull with the K&N intake and no tune. This is how K&N is able to claim that the product works, while in reality it's total trickery of the PCM and not a good idea at all.
K&N is relying upon the factory computer to apply a Wide-Open-Throttle Air/Fuel correction, based on learned part throttle A/F corrections. The comptuer can only learn at part throttle when it's closed loop and relying upon feedback from the O2 sensors. At WOT its running open loop and can't actively learned, just use corrections from closed loop.
As you can see, it does not do that great of a job of learning. The A/F is still lean at low RPM and not very straight.
Where does all the extra power come from? K&N probably does not even realize this, but without properly tuning for the intake, you totally screw up the load calculation. The computer see much lower load with the intake, ends up on much lower row on the spark table, and runs a ton more timing. You've effectively totally screwed up the spark table, and while it does have the effect of adding more spark and making more power, it does not do so in a correct fashion.
When the K&N intake is properly tuned for it makes more power and you get a safer and more consistent A/F ratio.
http://vmptuning.com/GT500/3knlearned.jpg