Rating Supercharger Kit Efficiency

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.

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 bolt-on 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:

Example-1:

• 367whp Baseline
• 517whp Results
• 91 Octane
• 8.0 PSI
• 3.996L displacement

Efc = ((517-357) - 7.15*(91 - 91)) / 3.996 / 8.0
= 150 - (7.15 * 0) / 3.996 / 8.0
= 150 / 3.996 / 8.0
= 4.69 Efficiency

Example-2:

• 409whp Baseline
• 601whp Results
• 96 Octane
• 6.25 PSI
• 4.619L displacement

Efc = ((601 - 409) - 7.15*(96-91)) / 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 per-vendor basis). Without any "outliers" -- the results are very good proof that this formula works.

Applications

There are a few applications for this formula above. Primarily, it can be used to cross-check 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 cross-check a vendor to prove how much boost they were running. The G-Power 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 non-biased 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 Custom-Built Motors

Since there is no baseline with a custom-built or low-compression 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 side-effect: 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

Example-1:

• 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

Example-2:

• 601whp Results
• 96 Octane
• 6.25 PSI
• 4.619L displacement

Efc = (601 - 7.15*(96-91)) / 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 Efc-v3 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 G-Power 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.