A few months ago, I was asked by M3Post user 'per' to rate the efficiency of the different supercharger kits on the market. My first attempt was to simply calculate the ratio of GAIN/PSI (the ratio of whp gain vs. PSI boost). 'Per' quickly pointed out that I couldn't rate efficiency in that manner because my own results were included, and mine were skewed by my displacement increase. So, I came up with the same idea  version2: Efc = Gain / Displacement / Boost. The idea is to measure efficiency as a function of Gain, Displacement, and Boost.
There are other ways to measure supercharger output used by companies like ESS. They simply measure the percentage increase of power from the baseline to the end result. This is a good approach if you have a standard kit with no customization options. But this approach does not work when you start mixing and matching hardware and different boost levels.
Here's a rundown of the various ways to measure supercharger performance  along with some pro's and con's. In all cases, the baseline must be true and correct, and no changes are allowed between the baseline and the final results.
Method  Pro's  Con's 
MaxHP 


Percentage 


Supercharger Efficiency Formula (Version 1) 


Supercharger Efficiency Formula (Version 2) 


Supercharger Efficiency Formula (Version 3) 


One advantage of this formula is that it can't be cheated or manipulated by any
vendor. It's just a number, and the number doesn't lie. A kit's performance
efficiency will not depend on boost level, displacement, headers, exhaust, or
any bolton items. Simply put, the kit efficiency will determine how well the
kit performs  and this number will remain relatively constant regardless of
any changes  except for octane rating.
To account for octane rating, I relied extensively on the Dyno Database. Using the results I had at my disposal, I calculated that each AKI point above 91, accounts for approximately 7.15whp of gain. Therefore, a 91 octane motor is the baseline, and anything above it will be adjusted by 7.15whp per AKI rating. There seems to be a ceiling on AKI rating. Tests have demonstrated that the MSS60 DME does not continue to increase performance above (approximately) 96 AKI octane gasoline. This was predicted by some M3Post forum members and then demonstrated in later tests.
Now that I know how much whp each point of octane adds or subtracts from performance, I can come up with a unified formula that accounts for baseline performance, displacement, boost, and gasoline. Here's what I came up with (version 3):
Efc = (Gain  (7.15*(Gas_AKI  91)) / Displacement / Boost
 Efc = Efficiency
 Gain = Horsepower gain (whp)
 Gas_AKI = AKI Octane rating of gasoline used during testing
 Displacement = Motor displacement
 Boost = Boost PSI
Here's how it works:
Example1:
 367whp Baseline
 517whp Results
 91 Octane
 8.0 PSI
 3.996L displacement
Efc = ((517357)  7.15*(91  91)) / 3.996 / 8.0
= 150  (7.15 * 0) / 3.996 / 8.0
= 150 / 3.996 / 8.0
= 4.69 Efficiency
Example2:
 409whp Baseline
 601whp Results
 96 Octane
 6.25 PSI
 4.619L displacement
Efc = ((601  409)  7.15*(9691)) / 4.619 / 6.25
= 192  (7.15*5) / 4.619 / 6.25
= 192  35.75 / 4.619 / 6.25
= 156.25 / 4.619 / 6.25
= 5.41 Efficiency
Real World Examples
Now let's look at some more real world examples. The results below were taken from the Dyno Database  all from independent dyno results. Not a single vendor dyno was used to compile the results below. You will quickly notice from these examples that the efficiency does not deviate very much for each vendor. There are no real statistical "outliers" here  because all of the results regardless of the displacement, boost, or gasoline produce an efficiency in the same ballpark as each other (on a pervendor basis). Without any "outliers"  the results are very good proof that this formula works.
Description  Before  After  Gain  Octane  Displ.  Boost  Efc. 
ESS46  409  561  152  91  4.619  6.0  5.48 
ESS46  409  601  192  96  4.619  6.25  5.41 
ESS VT2  329  468  139  91  3.996  6.5  5.39 
ESS VT1  338  441  103  92  3.996  4.5  5.33 
GPower SK2  338  457  119  91  3.996  6.0  4.92 
GPower SK2  319  437  118  91  3.996  6.0  4.92 
GPower SK2  346  545  199  94.5  3.996  9.0  4.83 
Gintani Stage2+Meth  367  517  150  91  3.996  8.0  4.69 
Gintani  330  461  131  91  3.996  7.0  4.68 
Applications
There are a few applications for this formula above. Primarily, it can be used to crosscheck a vendor. If a vendor's kit produces an efficiency factor of 7.80, but the kit efficiency with verifiable dynos has demonstrated an Efc=4.92, then it would be a clear sign that the baseline was not correct, the boost was not being reported accurately, the gasoline was not the octane rating claimed...or many of these factors combined. The bottom line is that this number does not lie  whereas vendors might. I've already used this formula to sniff out multiple instances where the baseline dyno was not taken from the same car.
I've also used this formula for another very important purpose as well. If you know the baseline of the car and the final result  this formula can be used to crosscheck a vendor to prove how much boost they were running. The GPower 9.0 PSI entry above was a great example. I knew the baseline, final result, gasoline octane  but I didn't know the boost. Using this formula, I calculated the boost as 9.0 PSI and then wrote the vendor to ask. I didn't realize the vendor was a mathematician  and he was impressed with the formula I presented. The vendor did confirm that the car was running 9.0 PSI  and that my formula was used correctly to figure this out.
Finally, the efficiency factor can be used to rate a vendor's product. It's very clear from the table above which vendor creates a product with greater efficiency than the other. Whereas vendors are very emphatic about their products and always claiming to be better than their competitors  this efficiency factor is a nonbiased way to rate the products and compare the results. As more vendor products come to market (AA, VF, etc.), it will be interesting to see how they stack up against the vendors already established in the market.
Low Compression and CustomBuilt Motors
Since there is no baseline with a custombuilt or lowcompression motor, the efficiency formula can be slightly modified. This is a case where MaxHP can be used instead of HP gain. This method comes with a negative sideeffect: Now, the results are dependent on the dyno  whereas the above method is relatively immune to dyno brands.
Efc = (MaxHP  (7.15*(Gas_AKI  91)) / Displacement / Boost
Example1:
 517whp Results
 91 Octane
 8.0 PSI
 3.996L displacement
Efc = (517  7.15*(91  91)) / 3.996 / 8.0
= 517  (7.15 * 0) / 3.996 / 8.0
= 517 / 3.996 / 8.0
= 16.17 Efficiency
Example2:
 601whp Results
 96 Octane
 6.25 PSI
 4.619L displacement
Efc = (601  7.15*(9691)) / 4.619 / 6.25
= 601  (7.15*5) / 4.619 / 6.25
= 601  35.75 / 4.619 / 6.25
= 156.25 / 4.619 / 6.25
= 19.57 Efficiency
Using the same exact DynoDB entries as above, but using MaxHP instead of "Gain"  the results would be as follows. There's a few things of importance to point out from the results below. For the most part, the relative order of the entries did not change. Only the items highlighted in red have change their relative positions. Secondly, the method below shows the superiority of measuring against the baseline. In Efcv3 the efficiency coefficients were all within a few percent of each other, whereas ignoring the baseline tends to spread out the results differently and with less accuracy. The GPower SK2 kit at the bottom (listed in blue) because it shows the effects of a different dyno brand. All of the other entries were gathered using a Dynojet  whereas the last entry was gathered with a Dyno Dynamics  which definitely have a lower measuring scale than Dynojet.
Description  Before  After  Gain  Octane  Displ.  Boost  Efc. 
ESS VT1  338  441  103  92  3.996  4.5  24.13 
ESS46  409  561  152  91  4.619  6.0  20.24 
ESS46  409  601  192  96  4.619  6.25  19.57 
GPower SK2  338  457  119  91  3.996  6.0  19.06 
GPower SK2  319  437  118  91  3.996  6.0  18.22 
ESS VT2  329  468  139  91  3.996  6.5  18.01 
Gintani  330  461  131  91  3.996  7.0  16.48 
Gintani Stage2+Meth  367  517  150  91  3.996  8.0  16.17 
GPower SK2  346  545  199  94.5  3.996  9.0  14.59 